N-Heterocyclic Carbene Organic Dies Bonded to TiO2 Surfaces: Photoelectrodes with an N-Heterocyclic Carbene-Organic Dye Derived from 2,4,5,6-tetra(9H-Carbazol-9-yl)isophtalonitrile (4CzIPN)The impact factor of this journal is 2.483, not that automatically filled in below.
Publication announcing new, easily prepared organic dyes and novel bonding to TiO2 semiconductors.
Manuscript submitted April 25, 2023 University of Alberta | Publication | 2017-01-01 | Octavio Martinez Perez, Mona Amiri, Loorthuraja Rasu, Bergens, S. |
Excellence of TeachingInterdepartmental Science Students' Society Excellence of Teaching Award for dedication to Undergraduate Teaching 2019 University of Alberta | Award | 2020-02-05 | Bergens, S. |
NSERC Alliance Alberta Innovates Advance ProgramA grant awarded by Alberta Innovates to Augment an NSERC Discovery grant. The research is to develop prototype nitrogen to NH3 electrolyzers. This research uses systems developed under the FES grant. University of Alberta | Award | 2023-01-18 | Bergens, S. |
Science Outreach Faculty of Science Service Award. I am honoured to receive this award for our efforts towards SciComm public outreach on Climate Change and Solar Fuels. My group and I have given a number of presentations to the public, public school classrooms, and summer preschools. These are listed in the output section. The presentations deal with climate change, solar fuels, and EDI in Science. Folks in the group from all over the world and from minoritized groups join me to present to the public and students of all ages to discuss climate change, solar fuels, and what it's like to be a Scientist working on these problems. We strongly emphasize that nobody should be discouraged from pursuing Science and that folks from many disciplines can contribute. University of Alberta | Award | 2020-02-21 | Bergens, S. |
Active, Stable, and Abundant Photocatalytic Materials for Hydrogen Fuels: Solar fuels by tandem photocatalysisSolar harvesting, conversion, and utilization are vital to the economy, environment, and society. It is essential to minimize the negative impact of fossil fuels, and to expand the development of renewables. Solar voltaics are key to achieving these goals.
We are developing hybrid photocatalytic cells that convert sunlight, water, and CO2 into high-energy fuels, or hydrogen. These fuels will help power a sustainable and carbon-neutral society. University of Alberta | Activity | 2017-09-21 | Chao Wang, Octavio Martinez Perez, Mona Amiri, Bergens, S. |
Calgary Lecture Series; Energy Panel: To provide continuing education opportunity in Calgary that showcases excellence and innovation at the University of Albertapanel discussion (1.2 hours long) with the public (audience ~ 300 people) at the Calgary public library. University of Alberta | Activity | 2019-05-22 | Bergens, S., John R Parkins, Maggie Cascadden, Naeth, M. |
Climate Change and Solar FuelsPresentation and lab tour to delegates attending the Sustainability in Higher Education in Canada Conference, 2019 University of Alberta | Activity | 2019-05-16 | Bergens, S., Octavio Martinez Perez, Mona Amiri |
Core-shell titanium dioxide@titanium nitride nanotube arrays for optical limiters and near-infrared sensitive optoelectronicsPresented by Sheng Zeng in Symposium: S3: Optical and Electronic Materials and Devices - Fundamentals and Applications in the Session titled: Hybrid and Composite Optical Materials.
Electrochemical anodization was used to form glass-like TiO2 nanotube arrays (TNTAs) on native (Ti foil) and non-native (silicon) substrates. Atomic layer deposition (ALD) was used to conformally coat TNTAs with ceramic overlayers of transition metal nitrides (TiN, ZrN, HfN). Core-shell nanotubes resulted with a double-walled structure consisting of a TiO2 inner wall and a metal nitride outer wall, and exhibited strong near-infrared localized surface plasmon resonances (LSPR). The ~100 nm nanotube diameters and LSPR effects rendered the core-shell TiO2@TiN nanotubes(NTs) excellent optical limiters due to their strong Mie scattering and absorption effects. Compared to optical limiters based on noble metal nanoparticles, TiO2@TiN NTs displayed stronger resilience and higher damage threshold under intense laser irradiation because of their ceramic nature. Due to hot electron injection into TiO2 following plasmon decay in the nitride, the core-shell nanotubes are also good plasmonic photocatalysts. University of Alberta | Activity | 2020-08-03 | Sheng Zeng, Ajay Manuel, Saralyn Riddell, Ryan Kisslinger, Shankar, K. |
Earth abundant 1D & 2D nanomaterial sensitized TiO2 nanotube arrays for visible light driven water-splitting University of Alberta | Activity | 2019-09-17 | Pawan Kumar, Ryan Kisslinger, Ujwal Thakur, Kazi Alam, "Ebru Uzer", "Tom Nilges", Shankar, K. |
Flame Annealed TiO2 and its Heterojunctions for the Production of Solar FuelsFlame annealed TiO2 received significant attention in the early 2000s as a method to improve the visible light responsivity of titania through the introduction of defects and dopants. In a highly cited but controversial paper, S.U.M. Khan and colleagues reported on highly efficient water-splitting using flame annealed TiO2 thin films
in the journal Science in 2002. Due to problems with the reproducibility of the reported results, spectral mismatch issues and potentially unphysical mechanisms, this line of research was abandoned. In the last few years, there has been a resurgence of interest in Black TiO2, which is a defect rich form of reduced titania exhibiting visible light absorption over a broad spectral range. Recently, the Shankar Lab found that flame annealing anodically formed TiO2 nanotube arrays produced an unusual morphological transition from circular to square-shaped cross-sections, which was accompanied by changes in the density of Ti3+ states and the phase composition. Using isotope-labeled mass spectrometry, we observed that flame annealed nanotubes significantly outperformed regular nanotubes in
the photoreduction of CO2 to methane while harvesting blue light. Flame annealed titania nanotubes also performed better than regular nanotubes in photoelectrochemical water splitting. This Invited Talk will focus on the use of flame annealed TiO2 nanotubes for the production of solar fuels. University of Alberta | Activity | 2019-03-06 | Kazi Alam, Shankar, K. |
Heterojunctions based on 2D Carbon-Based Semiconductor Nanomaterials for Photocatalysis and PhotovoltaicsKeynote Lecture at Virtual International Conference on Hierarchically Structured Materials (ICHSM'2021), 08 - 10 April 2021, which featured over 100 participants. University of Alberta | Activity | 2021-04-10 | Shankar, K. |
Heterojunctions based on 2D Carbon-Based Semiconductor Nanomaterials for Photocatalysis and PhotovoltaicsInvited Plenary Lecture at ISCMNB'21. University of Alberta | Activity | 2021-05-26 | Shankar, K. |
Hot Electron-mediated Plasmonic Photocatalysis Using Heterojunctions of Noble Metal Nanoparticles and Semiconductor Nanowires/NanotubesKeynote Lecture in Session 3:Nanomedicine, Nanomaterials & Nanotechnology at the Vebleo Webinar. My lecture was sandwiched in-between those of Dr. Arthur Nozik (NREL) and Prof. Sanjay Banerjee (University of Texas at Austin), who are both legends in the field of semiconductor optoelectronics. My lecture was also posted on YouTube by the conference organizers. University of Alberta | Activity | 2020-08-18 | Shankar, K. |
Modular construction of Ru- and Ir- chromophore photoanodes by covalent bonding and self-assemblyOral Presentation at Electrochemical Society Canadian section meeting University of Alberta | Activity | 2018-05-26 | Mona Amiri, Chao Wang, Octavio Martinez Perez, Bergens, S. |
Modular Construction of Water Oxidation Photoanodes by Covalent Bonding and Self-AssemblyDye-sensitized photoelectrochemical cells (DSPECs) convert the energy of visible light into chemical bonds through water splitting. We report a reliable method to attach 1,10-phenanthroline (phen) to ITO or TiO2 semiconductors by a C(5)-Osurface single covalent bond. Reaction between the surface phen and the corresponding Ru- or Ir- precursors formed the [Ru(bipy)2(phen)]2+ (bipy = 2,2'-bipyridine) or [Ir(ppy)2(phen)]+ (ppy = 2-phenylpyridine) chromophores grafted at C(5) to ITO or TiO2. We investigated the photoelectrochemical activity of these photoanodes with hydroquinone and triethylamine as sacrificial electron donors over a wide pH range (pH 1-13). The covalent C(5)-Osurface linkage is quite resistant to hydrolysis under basic conditions, unlike phosphonate acid groups. University of Alberta | Activity | 2018-03-14 | Chao Wang, Mona Amiri, Octavio Martinez Perez, Bergens, S. |
Modular Construction of Water Oxidation Photoanodes by Covalent Bonding and Self-AssemblyDye-sensitized photoelectrochemical cells (DSPECs) convert the energy of visible light into chemical bonds through water splitting. We report a reliable method to attach 1,10-phenanthroline (phen) to ITO or TiO2 semiconductors by a C(5)-Osurface single covalent bond. Reaction between the surface phen and the corresponding Ru- or Ir- precursors formed the [Ru(bipy)2(phen)]2+ (bipy = 2,2'-bipyridine) or [Ir(ppy)2(phen)]+ (ppy = 2-phenylpyridine) chromophores grafted at C(5) to ITO or TiO2. We investigated the photoelectrochemical activity of these photoanodes with hydroquinone and various amines as sacrificial electron donors over a wide pH range (pH 1-13). The covalent C(5)-Osurface linkage is quite resistant to hydrolysis under basic conditions. We found that these positively-charged TiO2/chromophore surfaces self-assemble with colloidal, anionic Ir1-xNix (x ranges from 0 to 0.5) hydrous oxide nanoparticles to form active photoanodes for water oxidation. University of Alberta | Activity | 2018-01-28 | Chao Wang, Mona Amiri, Riley Endean, "Samuel Varley", Benjamin E Rennie, Bergens, S. |
Molecular Brick Building Sets for Chromophores and Catalysts for Solar-Powered Water Splitting and CO2 ReductionInvited Speaker at the 22nd International Conference on Past and Present Research Systems on Green Chemistry University of Alberta | Activity | 2019-04-26 | Bergens, S., Mona Amiri, Octavio Martinez Perez, Riley Endean, Prabin Nepal, Jaya Pal, Jinkun Liu, "Shuai Xu" |
Nanosheets of carbon nitride and nitrogen doped graphene for photovoltaics and photocatalysisKeynote Lecture in Symposium on 2D Materials and Devices at International Conference on Emerging Electronics (ICEE-2020), 26-28 November 2020. University of Alberta | Activity | 2020-11-27 | Shankar, K. |
New Dyes and Catalysts for Photosynthetic Organic Reactions and Solar FuelsInvited Seminar (Zoom) for the Monthly Webinar Series at the Energy Technology Centre,
School of Engineering, University for Developing Studies. Ghana University of Alberta | Activity | 2023-02-28 | Bergens, S., Octavio Martinez Perez, Loorthuraja Rasu, Jinkun Liu, Mona Amiri, Elizabeth Murphy, Mike Donohoe, Dominic Lavergne |
New NHC- and Imidazole-Functionalized Carbazole Dyes for Visible-Light Organic- and Solar Fuels Photoreactions Over Homogeneous- and Heterogeneous Photocatalysts.Oral Presentation at the 21st International Symposium on Organometallic Chemistry University of Alberta | Activity | 2023-07-25 | Bergens, S., Octavio Martinez Perez, Elizabeth Murphy, Jinkun Liu, Dominic Lavergne, Mona Amiri, Loorthuraja Rasu |
Novel Earth Abundant Catalyst and Photosensitizer for Photocatalytic Carbon Dioxide Reduction Towards Solar FuelsPresentation by Undergraduate Student Elissa Yao at IUPAC CCCE 2021 University of Alberta | Activity | 2021-08-18 | Elissa Yao, Octavio Martinez Perez, Loorthuraja Rasu, Mike Donohoe, Bergens, S. |
Novel Materials for Clean and Sustainable Energy CHALLENGE PROGRAM WORKSHOPThis was an INVITATION-ONLY workshop related to a major new funding initiative in Clean-Tech, spearheaded by NRC. The purpose of my participation in the workshop was to deliver input in helping to refine the R&D areas and start identifying key projects and partners that would help NRC to collaboratively deliver next generation materials for clean and sustainable energy technologies. University of Alberta | Activity | 2018-12-06 | Shankar, K. |
Novel Photocatalysts for Carbon Dioxide Reduction Towards Solar FuelsInorganic Chemistry Exchange presentation by Elissa Yao describing our discovery of a visible light-driven CO2 conversion reaction using our newly discovered dyes. University of Alberta | Activity | 2021-08-17 | Elissa Yao, Bergens, S. |
Optical Modelling of Non-Lithographically Fabricated Photonic Crystal- and Plasmonic- PhotocatalystsHigh performance photocatalysts need to make optimal use of incident light to drive chemical reactions. Photonic crystals are materials consisting of microscale- and submicron-scale periodicity in their refractive index wherein the propagation of light is prohibited in a certain frequency band (called the photonic stop-band). When pi-conjugated molecules or quantum dots are introduced into a photonic crystal whose absorption profile matches the photonic stop band, very strong absorption can result in such defect-doped photonic crystals, which is useful for photocatalysis. Likewise, nanoscale- and submicron-scale noble metal structures exhibit strong surface plasmon resonances (SPR) that result in an amplification of the local field and the generation of energetic carriers called "hot electrons". The exploitation of SPR in photocatalysis forms the basis for the rapidly expanding field of plasmonic photocatalysis. Herein, we present the results of three-dimensional finite difference time domain (3D-FDTD) electromagnetic simulations of solution grown photonic crystal and plasmonic materials for photocatalytic applications. These simulations are tremendously helpful in explaining experimental data and in obtaining predictive insights into the optimal geometries. Unlike lithographically patterned nanomaterials with deterministically positioned absorbers and scatterers, the underlying spatial configuration in non-lithographically fabricated photonic crystals and plasmonic materials is frequently unclear, thus requiring a heuristic and iterative modelling approach to obtain useful information. University of Alberta | Activity | 2018-06-20 | Sheng Zeng, Ajay Manuel, Ehsan Vahidzadeh, Collin VanEssen, Yun Zhang, Piyush Kar, Shankar, K. |
Photocatalytic Production of Hydrogen Towards Solar FuelsInorganic Chemistry Exchange Student Presentation about our highest activity earth abundant Cobalt-DMG catalyst for visible light-driven H2 production with our newly discovered organic dyes. University of Alberta | Activity | 2021-08-18 | Mike Donohoe, Bergens, S. |
Photocatalytic Production of Hydrogen Towards Solar FuelsPresentation by Mike Donohoe at the IUPAC CCCE 2021 Conference describing our new discovery of the most active Co-DMG complex catalyzed photocatalytic hydrogen evolution using visible light and our new organic earth abundant dye. University of Alberta | Activity | 2021-08-18 | Mike Donohoe, Elissa Yao, Octavio Martinez Perez, Loorthuraja Rasu, Bergens, S. |
Plasmonic Catalysis: Fundamentals, Materials, Methods And ChallengesPlenary Lecture at International Online Conference on Nanomaterials (ICN’2021), April 9-11, 2021 which featured more than 200 participants University of Alberta | Activity | 2021-04-11 | Shankar, K. |
Robust Plasmonic Glasses using nanoporous TiO2 embedded with Au nanoparticlesPresented by Ajay Manuel in Symposium: S3: Optical and Electronic Materials and Devices - Fundamentals and Applications in the Session titled: Hybrid and Composite Optical Materials.
A high throughput, large area substrate-compatible, solution process namely electrochemical anodization has been used to grow highly ordered, vertically oriented, titania nanotube arrays (TNTAs). We introduced an innovation into the anodization process that enabled us to embed Au NPs into the nanostructured titania thin films. We call the resulting substrates Au NP-TNTAs. Au NP-TNTAs exhibited localized surface plasmon resonance (LSPR) peaks at ~600 nm characterized by very strong extinction coefficients and high ensemble Q-factors. The high surface area Au NP-TNTAs are excellent substrates for bioimaging and biosensing due to the strong enhancement of two-photon fluorescence observed in them. Au NP-TNTAs are also excellent plasmonic photocatalysts for sunlight-driven water-splitting. University of Alberta | Activity | 2020-08-03 | Sheng Zeng, Ryan Kisslinger, Ajay Manuel, Kazi Alam, Shankar, K. |
Solar FuelsPlenary lecture. Student Organized Electrochemical Society, British Columbia chapter, Vancouver University of Alberta | Activity | 2019-07-26 | Bergens, S. |
Straight-Forward Derivatizations of Tetracarbazole-Dicyanobenzene Organic Dyes for Solar Fuels Photoelectrodes and Heterogeneous Photocatalysts for Photosynthetic Organic Reactions. Oral presentation by Steve Bergens announcing our novel organic dyes as components of photoelectrons for converting CO2 into solar fuels. University of Alberta | Activity | 2021-08-19 | Bergens, S., Loorthuraja Rasu, Mona Amiri, Jinkun Liu, Octavio Martinez Perez |
Tsinghua University and UAlberta Student WorkshopDiscussion panel on the future energy systems research. University of Alberta | Activity | 2017-10-06 | Chao Wang, Bergens, S. |
Visible Light Responsive, Earth-Abundant Heterojunction Photocatalysts University of Alberta | Activity | 2018-06-11 | Shankar, K. |
Asymmetric Hydrogenation of Esters and Efforts Towards PhotohydrogenationRiley Endean's PhD Dissertation describing, in part, the synthesis of molecular photocatalysts that were explored as photoelectrodes in solar fuels chemistry. These "NHC" compounds were part of the discovery of a new way to attach dyes to semiconductor surfaces. Riley successfully defended his dissertation on Dec 21, 2020. | Publication | 2021-01-28 | Riley Endean |
Developing Catalysts for Energy Conversion DevicesA thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy by Chao Wang
University of Alberta | Publication | 2018-07-31 | Chao Wang, Bergens, S. |
Multifunctional Carbazole-Based Materials as Electrochemical Water Splitting and Photoredox CatalysisPhD dissertation | Publication | 2023-09-29 | Jinkun Liu |
New abundant 4CzIPN-derived Photosensitizers and Catalysts for Photosynthetic Organic Reactions and Solar FuelsPhD dissertation. | Publication | 2024-01-22 | Octavio Martinez Perez |
Using 1D and 2D Nanomaterials in Halide Perovskite Solar Cells to Enhance Light Harvesting and Charge Collection | Publication | 2020-03-16 | Ujwal Thakur |
There’s more than enough solar power to meet our energy needs: the problem is storing itInterview about the work on solar fuels and ways how to solve energy storage problems University of Alberta | Activity | 2018-04-10 | Bergens, S., Mona Amiri |
Development of Re(I) Photocatalysts for the Photochemical Reduction of Atmospheric CO2Master's Dissertation | Publication | 2024-09-25 | Elizabeth Murphy |
Active, Stable, and Abundant Photocatalytic Materials for Hydrogen Fuels: Solar Fuels by Tandem PhotocatalysisPoster presentation summarizing the theory behind our research University of Alberta | Activity | 2018-10-03 | Chao Wang, Mona Amiri, Riley Endean, "Samuel Varley", Benjamin E Rennie, Octavio Martinez Perez, Bergens, S. |
Catalysis and Energy Worldwide Universities Network (1.5-hour class- 22 students) University of Alberta | Activity | 2019-07-15 | Bergens, S. |
Catalysis, Climate Change, and Solar FuelsInvited public presentation at Edmonton Public Library. It is available as a FES video on YouTube
(https://youtu.be/48EYVEzU_aM) University of Alberta | Activity | 2022-05-01 | Octavio Martinez Perez, Mike Donohoe, Bergens, S. |
Chemistry demos for kids, Mad ScienceScience demo University of Alberta | Activity | 2019-08-23 | Emily Majaesic, Bergens, S. |
Climate Change and Artificial Photosynthesis to Store Solar Energy in Fuels.Classroom presentation to grade 8 students at Ecole Champs Vallee School University of Alberta | Activity | 2022-04-13 | Bergens, S., Octavio Martinez Perez |
Climate Change on Earth and MarsA zoom presentation to Julie Arsenaut's grade 8 class at Michael Strembitsky School University of Alberta | Activity | 2021-03-03 | Bergens, S. |
Climate Change, Solar Fuels, and ScienceLecture, demonstration, and supervise experiments by U School Class from John A McDougall School University of Alberta | Activity | 2022-10-31 | Bergens, S., Octavio Martinez Perez, Jinkun Liu, Dominic Lavergne, Elizabeth Murphy |
Edmonton High School Students, TeamUp Science Summer Camp (Enrichment Program)The TeamUp science summer camp paid a visit for an enrichment experience (a group of about 20 students from high schools in Edmonton). The program was intended to inspire them to continue their education to university. This group were shown different instruments used in a Chemistry lab for solar fuel generation application. University of Alberta | Activity | 2018-07-27 | Lan Truong, Mona Amiri, Jaya Pal, Bergens, S. |
Energy ExplorersPresentation for FES at the Telus World of Science. My FES student, Elizabeth Murphy presented ways to convert CO2 into solar fuels to the public. | Activity | 2023-03-04 | Elizabeth Murphy |
In Lab Presentation and TourFuture Energy Systems lab tour University of Alberta | Activity | 2019-10-16 | Bergens, S., Loorthuraja Rasu, Mona Amiri, Octavio Martinez Perez |
N-Heterocyclic Carbene-Chromophore Ligands in Organic Photocatalysis and Solar Fuels ChemistryInvited Departmental Seminar given by Bergens University of Alberta | Activity | 2023-03-16 | Bergens, S., Octavio Martinez Perez, Loorthuraja Rasu, Mona Amiri, Elizabeth Murphy, Mike Donohoe, Dominic Lavergne |
Novel 4CzIPN-derived Photosensitizers for Organic Reactions and Solar FuelsPublic PhD presentation | Activity | 2023-01-23 | Octavio Martinez Perez |
Novel Carbazole-Based Materials as Water Splitting and Photoredox Catalysis Public PhD presentation. | Activity | 2023-09-26 | Jinkun Liu |
Photoelectrochemical solar cells for water oxidation and CO2 reduction University of Alberta | Activity | 2018-03-08 | Chao Wang, Octavio Martinez Perez, Mona Amiri, Bergens, S. |
Photoelectrochemical solar cells for water oxidation and CO2 reduction reactions University of Alberta | Activity | 2018-03-08 | Chao Wang, Octavio Martinez Perez, Mona Amiri, Bergens, S. |
Photoelectrochemical solar cells for water oxidation and CO2 reduction systems University of Alberta | Activity | 2017-12-05 | Chao Wang, Mona Amiri, Bergens, S. |
Renewable Energies presentation and hands-on photoelectrochemistry experimentEcole Champs Vallee School students (90 students) University of Alberta | Activity | 2020-01-24 | Emily Majaesic, Loorthuraja Rasu, Octavio Martinez Perez, Bergens, S. |
Renewable Energies presentation and hands-on photoelectrochemistry experimentMichael Strembitsky School students (90 students) University of Alberta | Activity | 2019-12-16 | Mona Amiri, Octavio Martinez Perez, Bergens, S. |
Renewable Energies presentation and hands-on photoelectrochemistry experimentU School University of Alberta | Activity | 2020-02-03 | Bergens, S., Loorthuraja Rasu, Mona Amiri, Emily Majaesic |
Shaping the Future of Energy/ Solar EnergyThe BERLIN SCIENCE WEEK is an international event that brings people from the world’s most innovative scientific institutions together in Berlin. It is dedicated to the dialogue between science and society to inspire a deeper understanding of our world.
In partnership with the Canadian Embassy in Berlin, Future Energy Systems hosted a special event exploring the future of energy in Canada and around the world. In this event, some of our leading research in solar, geothermal, bioenergy, land and water reclamation and system-wide assessments of energy was presented.
Also, a discussion panel was organized to debate success of global energy research partnerships, as well as the University of Alberta's successful research relationships in Germany with the Fraunhofer Society, Helmholtz Association and RWTHAachen. University of Alberta | Activity | 2018-11-05 | Bergens, S., Mona Amiri, Octavio Martinez Perez, Jaya Pal, Riley Endean, Chao Wang |
Skype a Scientist Program, 3rd grade Students (Rosemary Heights School)Skype session with elementary school students to help them get familiar with solar energy and solar fuels. University of Alberta | Activity | 2018-10-10 | Mona Amiri, Bergens, S. |
Skype a Scientist Program, 4th grade Students at Brougham Elementary School, KansasSkype session with elementary school students to help them get familiar with solar energy and solar fuels. University of Alberta | Activity | 2018-10-04 | Mona Amiri, Bergens, S. |
Skype a Scientist Program, 6th grade Students (John Knox Christian School)Skype session with elementary school students to help them get familiar with solar energy and solar fuels University of Alberta | Activity | 2018-10-31 | Bergens, S. |
Skype a Scientist Program, 6th grade Students (John Knox Christian School)Skype session with elementary school students to help them get familiar with solar energy and solar fuels. University of Alberta | Activity | 2018-10-31 | Octavio Martinez Perez, Mona Amiri, Bergens, S. |
Solar Fuels and Climate ChangeCO2 reduction and hydrogen fuel generation and fuel cells University of Alberta | Activity | 2019-05-11 | Mona Amiri, Octavio Martinez Perez, Bergens, S. |
Solar Fuels, Research, and Climate ChangeLecture, demonstration, and supervise experiments by U School Class from Anne Fitzgerald School University of Alberta | Activity | 2022-10-03 | Bergens, S., Octavio Martinez Perez, Dominic Lavergne, Elizabeth Murphy, Jinkun Liu |
Teaching outreach Climate Change and Solar FuelsLecture, demonstration, and supervise experiments by U School Class from Andrew School. University of Alberta | Activity | 2022-10-26 | Bergens, S., Octavio Martinez Perez, Dominic Lavergne, Elizabeth Murphy, Jinkun Liu |
Teaching Solar FuelsGave a presentation and met with local Teachers describing our research on solar fuels and strategies to teach students and the public on climate change. University of Alberta | Activity | 2023-03-13 | Bergens, S. |
Two presentations and Lab tour University of Alberta | Activity | 2019-05-08 | Bergens, S., Mona Amiri, Octavio Martinez Perez |
Two presentations and lab tours for international students University of Alberta | Activity | 2019-07-11 | Bergens, S., Emily Majaesic, Mona Amiri |
Carbazole-cyanobenzene dyes electrografted to carbon or ITO support for visible light-driven photoanodes and olefin isomerizations (USPTO)USPTO Patent Application No.: 63/166,334
FIled on: 2021-03-26
Abstract: Molecular dyes are utilized in applications including displays,1–3 photocatalysis of organic reactions,4,5 photodynamic cancer therapy,6 dye-sensitized solar cells,7–10 and photoelectrodes that produce solar fuels.11,12 Dye-sensitized systems incorporate a thin, often molecular layer of dye, typically on the surface of a semiconductor.1–3,7–12 The majority of dye-sensitized systems employ transition metal complexes as dyes.13,14 Ru- 8–10,15,16 and Ir- 15,17 polypyridyl systems are the most common because they offer good conversion efficiencies, they are readily modified, and form long-lived triplet excited states by intersystem crossing (ISC). These systems can be costly and toxic. Organic dyes are less expensive if they are easily made from available precursors.18 The organic dyes used in
photoelectrodes19 include porphyrins,20,21 perylene derivatives,22,23 sub porphyrins,24 and triphenylamines.25 Push-pull dyes have been studied extensively in dye sensitized solar cells,8–10 and more recently, in photoelectrodes for water oxidation and hydrogen
production.14,24–26 Organic dyes are typically attached to electrode surfaces by carboxylate21 or phosphonate22 bridges, or by noncovalent interactions.20,23 Phosphonate and carboxylate bridges tend to hydrolyze at alkaline pHs. Several groups, including our own, have demonstrated that electrografting aromatic diazonium compounds results in covalent bonds between semiconductors (SCs) and transition metal-based dyes that tolerate alkaline pHs better than carboxylate and phosphonate linkages.16,27 Further, we demonstrated that the SC-dye bonds predominantly form at the electroactive sites on the semiconductor,16 a property that may prevent organic dye aggregation on the SC surface. There are few examples of organic chromophores electrografted to electrode surfaces by diazonium chemistry.28,29 We now report a simple synthesis to allow bonding of the carbazole-cyanobenzene push-pull organic dye 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN)2,4 to ITO and carbon. The resulting photoelectrodes are active and appreciably
stable towards photooxidations under acidic, and basic pHs. They are also active photocatalysts for the photosynthetic isomerization of stilbene- and cinnamic acid-derivatives. University of Alberta | IP Management | 2021-03-26 | Bergens, S., Mona Amiri, Loorthuraja Rasu |
Carbazole-cyanobenzene dyes electrografted to carbon or ITO supports for visible light driven photoanodes and olefin isomierizationUS patent application. # 63327873. Filed April 6, 2022 University of Alberta | IP Management | 2022-04-06 | Loorthuraja Rasu, Mona Amiri, Bergens, S. |
Electronically Conductive, Multifunctional Polymer Binder for Highly Active, Stable, and Abundant Composite Electrodes for Oxygen EvolutionA patent application describing the highly active, stable oxygen evolution reaction electrodes made in 3 simple steps from inexpensive starting materials. Will be submitted Monday or Tuesday of the week of May 8, 2023. This work was accepted in ACS Applied Materials & Interfaces this week, and the application will be filed before the paper is published online by the journal. University of Alberta | IP Management | 2023-05-08 | Jinkun Liu, Bergens, S. |
A One-Step Electropolymerization of a Dicyanobenzene-Carbazole-Imidazole Dye for Photoelectrodes, Heterogeneous Photocatalysts, and Sensing ApplicationsNew, abundant organic dyes are polymerized in one step to form visible light driven electrodes for electrooxidations of sacrificial electron donors, fluorescent sensors, and photocatalyst for olefin isomerizations. The phosphorescence of the electrodes is tuned with electrode potential. University of Alberta | Publication | 2017-01-01 | Jinkun Liu, Octavio Martinez Perez, Loorthuraja Rasu, Dominic Lavergne, Elizabeth Murphy, Bergens, S. |
A Simple Imidazole Derivative of 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene Absorbed on Silica Gel for Photosynthetic Isomerizations of Olefins in Batch and FlowWe developed a novel, inexpensive organic dye based upon the recent, highly popular Carbazole-Cyanobenzene dye modified with an imidazole donating group. Imidazole groups are well-known for bonding to metal centres and strongly enhancing their activities. In this paper we describe the synthesis of this system, and remarkably, discover that it is adsorbed by SiO2, and the adsorbed systems carry out photosynthetic reactions in sunlight under air. Literally in the parking lot on a sunny day. This dye will feature heavily in our solar fuels electrodes and molecular systems
This manuscript will be submitted the week of May 17, 2021 University of Alberta | Publication | 2021-05-14 | Bergens, S., Loorthuraja Rasu |
Active, Simple Iridium--Copper Hydrous Oxide Electrocatalysts for Water Oxidation University of Alberta | Publication | 2017-02-16 | Chao Wang, Reza B Moghaddam, Bergens, S. |
Air- and water-stable halide perovskite nanocrystals protected with nearly-monolayer carbon nitride for CO 2 photoreduction and water splittingHalide perovskites are exciting candidates for broad-spectrum photocatalysts but have the problem of ambient stability. Protective shells of oxides and polymers around halide perovskite nano- and micro-crystals provide a measure of chemical and photochemical resilience but the photocatalytic performance of perovskites is compromised due to low electron mobility in amorphous oxide or polymer shells and rapid charge carrier recombination on the surface. Herein an in situ surface passivation and stabilization of CsPbBr3 nanocrystals was achieved using monolayered graphenic carbon nitride (CNM). Extensive characterization of carbon nitride protected CsPbBr3 nanocrystals (CNMBr) indicated spherical CsPbBr3 nanoparticles encased in a few nm thick g-C3N4 sheets facilitating better charge separation via percolation/tunneling of charges on conductive 2D nanosheets. The CNMBr core-shell nanocrystals demonstrated enhanced photoelectrochemical water splitting performance and photocurrent reaching up to 1.55 mA cm−2. The CNMBr catalyst was successfully deployed for CO2 photoreduction giving carbon monoxide and methane as the reaction products. University of Alberta | Publication | 2022-08-01 | Devika Laishram, Sheng Zeng, Kazi Alam, Aarat P Kalra, Kai Cui, Pawan Kumar, Rakesh K Sharma, Shankar, K. |
All-solid-state formation of titania nanotube arrays and their application in photoelectrochemical water splittingThe present work demonstrates for the first time the facile fabrication of TiO2 nanotube arrays (TNTAs) by a fluoride-free solid-state anodization process using LiClO4 containing solid polymeric electrolyte. The resulting nanotubes were tested for photoelectrochemical water splitting. The elimination of liquid electrolytes in electrochemical anodization constitutes a paradigm shift for the formation of nanoporous and nanotubular metal oxides. Our results open a new area of research that uses the distinctive properties of solid polymer electrolytes to achieve targeted doping and nano-morphologies. Characterization of the grown TNTAs indicated solid state anodized TNTAs to consist purely of the anatase phase of titania. The solid-state anodization process provides several advantages over conventional liquid electrolytes such as easy handling and processing, better charge transport, environmentally benign chemicals and methodology. Photoelectrochemical water splitting experiments were performed which confirmed the viability of TNTAs grown by the new solid-state process for photocatalytic applications. University of Alberta | Publication | 2018-08-08 | "Arezoo Hosseini", Pawan Kumar, Najia Mahdi, Yun Zhang, Shankar, K. |
Arrays of TiO2 nanorods embedded with fluorine doped carbon nitride quantum dots (CNFQDs) for visible light driven water splittingGraphenic semiconductors such as carbon nitride are attracting increasing attention as photocatalysts due to their chemical stability, visible light absorption and excellent electronic properties. The photocatalytic activity of nanostructured TiO2 catalysts is constrained by the wide bandgap and concomitant low visible light responsivity of TiO2. In this context we present the formation of new fluorine doped carbon nitride quantum dots (CNFQDs) by solid state reaction and the subsequent examination of their heterojunctions with TiO2 for photoelectrochemical water splitting. Arrays of rutile phase TiO2 nanorods embedded with CNFQDs were synthesized by a simple in situ hydrothermal approach and the resulting nanomaterials were found to exhibit strong visible light absorption. The energetics at the heterojunction were favorable for efficient electron transfer from CNFQDs to TiO2 under visible light irradiation and transfer of holes to the aqueous electrolyte. CNFQD-sensitized TiO2 nanorods exhibited a strong photoelectrochemical response up to 500 nm. Reuse experiments confirmed robustness and long term stability of the sample without exhausting the catalytic performance. The present work demonstrates a new pathway to sensitize TiO2 to visible photons by the in situ formation of embedded heterojunctions with fluorine doped carbon nitride quantum dots. University of Alberta | Publication | 2018-05-12 | Pawan Kumar, Ujwal Thakur, Kazi Alam, Piyush Kar, Ryan Kisslinger, Sheng Zeng, Sahil Patel, Shankar, K. |
Core-shell titanium dioxide-titanium nitride nanotube arrays with near-infrared plasmon resonancesTitanium nitride (TiN) is a ceramic with high electrical conductivity which in nanoparticle form, exhibits localized surface plasmon resonances (LSPRs) in the visible region of the solar spectrum. The ceramic nature of TiN coupled with its dielectric loss factor being comparable to that of gold, render it attractive for CMOS polarizers, refractory plasmonics, surface-enhanced Raman scattering and a whole host of sensing applications. We report core–shell TiO2–TiN nanotube arrays exhibiting LSPR peaks in the range 775–830 nm achieved by a simple, solution-based,
low cost, large area-compatible fabrication route that does not involve laser-writing or lithography. Self-organized, highly ordered TiO2 nanotube arrays were grown by electrochemical anodization of Ti thin films on fluorine-doped tin oxide-coated glass substrates and then conformally coated with a thin layer of TiN using atomic layer deposition. The effects of varying the TiN layer thickness and thermal annealing on the LSPR profiles were also investigated. Modeling the TiO2–TiN core–shell nanotube structure using two different approaches, one employing effective medium approximations coupled with Fresnel coefficients, resulted in calculated optical spectra that closely matched the experimentally measured spectra. Modeling provided the insight that the observed near-infrared resonance was not collective in nature, and was mainly attributable to the longitudinal resonance of annular nanotube-like TiN
particles redshifted due to the presence of the higher permittivity TiO2 matrix. The resulting TiO2–TiN core–shell nanotube structures also function as visible light responsive photocatalysts, as evidenced by their photo-electrochemical water-splitting performance under light emitting diode illumination using 400, 430 and 500 nm photons. University of Alberta | Publication | 2018-02-01 | Samira Farsinezhad, Thariq Shanavas, Najia Mahdi, Abdelrahman M Askar, Piyush Kar, Himani Sharma, Shankar, K. |
Effect of morphology on the photoelectrochemical performance of nanostructured Cu2O photocathodesCu2O is a promising earth-abundant semiconductor photocathode for sunlight-driven water splitting. Characterization results are presented to show how the photocurrent density (Jph), onset potential (Eonset), band edges, carrier density (NA), and interfacial charge transfer resistance (Rct) are affected by the morphology and method used to deposit Cu2O on a copper foil. Mesoscopic and planar morphologies exhibit large differences in the values of NA and Rct. However, these differences are not observed to translate to other photocatalytic properties of Cu2O. Mesoscopic and planar morphologies exhibit similar Eg and Efb values of 1.93±0.04 eV and 0.48±0.06 eV respectively. Eonset of 0.48±0.04 eV obtained for these systems is close to the Efb indicating negligible water reduction overpotential. Electrochemically deposited planar Cu2O provides the highest photocurrent density of 5.0 mA cm−2 at 0 V vs RHE of all the morphologies studied. The photocurrent densities observed in this study are among the highest reported values for the bare Cu2O photocathodes. Although different deposition methods show a similar average photocurrent density 2.8±0.3 mA/cm2 at 0 V vs RHE, large variations in the photocurrent density are observed for samples prepared under nominally identical deposition methods. University of Alberta | Publication | 2020-07-01 | Lian Shoute, Kazi Alam, Ehsan Vahidzadeh, Ajay Manuel, Sheng Zeng, Pawan Kumar, Piyush Kar, Shankar, K. |
Electronically Conductive, Multifunctional Polymer Binder for Highly Active, Stable, and Abundant Composite Electrodes for Oxygen EvolutionNote the impact factor of the journal is 10.4, not 8.4 as automatically inputed.
This is a publication describing the most active earth-abundant oxygen evolution electrodes reported to date. There can be no green hydrogen economy without water electrolysis driven by renewable energy. Water electrolysis requires the oxygen evolution reaction (OER) in 1/2 of the unit. We discovered a simple way to prepare electrodes in three easy steps from inexpensive chemicals that are the most active and stable abundant water OER electrodes reported to date. We cannot find reports of more active and stable systems than ours that are also made of earth abundant materials. In our case, Ni, Fe, carbon and nitrogen. Unlike most systems in the literature, we tested ours under very harsh conditions: 6 M KOH, 85 deg C, 115 hours of continuous operation with very little loss in activity. University of Alberta | Publication | 2023-05-10 | Jinkun Liu, Bergens, S. |
Enhanced Charge Separation in g-C3N4–BiOI Heterostructures for Visible Light Driven Photoelectrochemical Water Splitting University of Alberta | Publication | 2019-01-07 | Kazi Alam, Pawan Kumar, Piyush Kar, Ujwal Thakur, Sheng Zeng, "Kai Cui", Shankar, K. |
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems Based on SnIP University of Alberta | Publication | 2019-03-13 | "Claudia Ott", "Felix Reiter", "Maximilian Baumgartner", "Markus Pielmeier", "Anna Vogel", "Patrick Walke", "Stefan Burger", "Michael Ehrenreich", "Gregor Kieslich", "Dominik Daisenberger", "Jeff Armstrong", Ujwal Thakur, Pawan Kumar, "Shunda Chen", "Davide Donadio", "Lisa Walter", "Thomas Weitz", Shankar, K., "Tom Nilges" |
Harvesting Hot Holes in Plasmon-Coupled Ultrathin Photoanodes for High-Performance Photoelectrochemical Water SplittingThe harvesting of hot carriers produced by plasmon decay to generate electricity or drive a chemical reaction enables the reduction of the thermalization losses associated with supra-band gap photons in semiconductor photoelectrochemical (PEC) cells. Through the broadband harvesting of light, hot-carrier PEC devices also produce a sensitizing effect in heterojunctions with wide-band gap metal oxide semiconductors possessing good photostability and catalytic activity but poor absorption of visible wavelength photons. There are several reports of hot electrons in Au injected over the Schottky barrier into crystalline TiO2 and subsequently utilized to drive a chemical reaction but very few reports of hot hole harvesting. In this work, we demonstrate the efficient harvesting of hot holes in Au nanoparticles (Au NPs) covered with a thin layer of amorphous TiO2 (a-TiO2). Under AM1.5G 1 sun illumination, photoanodes consisting of a single layer of ∼50 nm diameter Au NPs coated with a 10 nm shell of a-TiO2 (Au@a-TiO2) generated 2.5 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias, rising to 3.7 mA cm–2 in the presence of a hole scavenger (methanol). The quantum yield for hot-carrier-mediated photocurrent generation was estimated to be close to unity for high-energy photons (λ < 420 nm). Au@a-TiO2 photoelectrodes produced a small positive photocurrent of 0.1 mA cm–2 even at a bias of −0.6 V indicating extraction of hot holes even at a strong negative bias. These results together with density functional theory modeling and scanning Kelvin probe force microscope data indicate fast injection of hot holes from Au NPs into a-TiO2 and light harvesting performed near-exclusively by Au NPs. For comparison, Au NPs coated with a 10 nm shell of Al2O3 (Au@Al2O3) generated 0.02 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias. These results underscore the critical role played by a-TiO2 in the extraction of holes in Au@a-TiO2 photoanodes, which is not replicated by an ordinary dielectric shell. It is also demonstrated here that an ultrathin photoanode (<100 nm in maximum thickness) can efficiently drive sunlight-driven water splitting. University of Alberta | Publication | 2021-09-04 | Ehsan Vahidzadeh, Sheng Zeng, Kazi Alam, Pawan Kumar, Saralyn Riddell, Narendra Chaulagain, "Sergey Gusarov", Alexander E Kobryn, Shankar, K. |
Heterojunctions of halogen-doped carbon nitride nanosheets and BiOI for sunlight-driven water-splittingA fluorine-doped, chlorine-intercalated carbon nitride (CNF-Cl) photocatalyst has been synthesized for simultaneous improvements in light harvesting capability along with suppression of charge recombination in bulk g-C3N4. The formation of heterojunctions of these CNF-Cl nanosheets with low bandgap, earth abundant bismuth oxyiodide (BiOI) was achieved, and the synthesized heterojunctions were tested as active photoanodes in photoelectrochemical water splitting experiments. BiOI/CNF-Cl heterojunctions exhibited extended light harvesting with a band-edge of 680 nm and generated photocurrent densities approaching 1.3 mA cm−2 under AM1.5 G one sun illumination. Scanning Kelvin probe force microscopy under optical bias showed a surface potential of 207 mV for the 50% BiOI/CNF-Cl nanocomposite, while pristine CNF-Cl and BiOI had surface photopotential values of 83 mV and 98 mV, respectively, which in turn, provided direct evidence of superior charge separation in the heterojunction blends. Enhanced charge carrier separation and improved light harvesting capability in BiOI/CNF-Cl hybrids were found to be the dominant factors in increased photocurrent, compared to the pristine constituent materials. University of Alberta | Publication | 2019-11-01 | Kazi Alam, Pawan Kumar, Piyush Kar, Ankur Goswami, Ujwal Thakur, Sheng Zeng, Ehsan Vahidzadeh, Kai Cui, Shankar, K. |
Heterojunctions of mixed phase TiO2 nanotubes with Cu, CuPt, and Pt nanoparticles: interfacial band alignment and visible light photoelectrochemical activityAnodically formed, vertically oriented, self-organized cylindrical TiO2 nanotube arrays composed of the anatase phase undergo an interesting morphological and phase transition upon flame annealing to square-shaped nanotubes composed of both anatase and rutile phases. This is the first report on heterojunctions consisting of metal nanoparticles (NPs) deposited on square shaped TiO2 nanotube arrays (STNAs) with mixed rutile and anatase phase content. A simple photochemical deposition process was used to form Cu, CuPt, and Pt NPs on the STNAs, and an enhancement in the visible light photoelectrochemical water splitting performance for the NP-decorated STNAs was observed over the bare STNAs. Under narrow band illumination by visible photons at 410 nm and 505 nm, Cu NP-decorated STNAs performed the best, producing photocurrents 80% higher and 50 times higher than bare STNAs, respectively. Probing the energy level structure at the NP–STNA interface using ultraviolet photoelectron spectroscopy revealed Schottky barrier formation in the NP-decorated STNAs, which assists in separating the photogenerated charge carriers, as also confirmed by longer charge carrier lifetimes in NP-decorated
STNAs. While all the NP-decorated STNAs showed enhanced visible light absorption compared to the bare STNAs, only the Cu NPs exhibited a clear plasmonic behavior with an extinction cross section that peaked at 550 nm. University of Alberta | Publication | 2017-11-01 | Piyush Kar, Yun Zhang, Najia Mahdi, Ujwal Thakur, Benjamin Wiltshire, Ryan Kisslinger, Shankar, K. |
Hot Electrons in TiO2-Noble Metal Nano-Heterojunctions: Fundamental Science and Applications in PhotocatalysisPlasmonic photocatalysis enables innovation by harnessing photonic energy across a broad swathe of the solar spectrum to drive chemical reactions. This review provides a comprehensive summary of the latest developments and issues for advanced research in plasmonic hot electron driven photocatalytic technologies focusing on TiO2–noble metal nanoparticle heterojunctions. In-depth discussions on fundamental hot electron phenomena in plasmonic photocatalysis is the focal point of this review. We summarize hot electron dynamics, elaborate on techniques to probe and measure said phenomena, and provide perspective on potential applications—photocatalytic degradation of organic pollutants, CO2 photoreduction, and photoelectrochemical water splitting—that benefit from this technology. A contentious and hitherto unexplained phenomenon is the wavelength dependence of plasmonic photocatalysis. Many published reports on noble metal-metal oxide nanostructures show action spectra where quantum yields closely follow the absorption corresponding to higher energy interband transitions, while an equal number also show quantum efficiencies that follow the optical response corresponding to the localized surface plasmon resonance (LSPR). We have provided a working hypothesis for the first time to reconcile these contradictory results and explain why photocatalytic action in certain plasmonic systems is mediated by interband transitions and in others by hot electrons produced by the decay of particle plasmons. University of Alberta | Publication | 2021-05-01 | Ajay Manuel, Shankar, K. |
Investigation into the properties of a ruthenium(polypyridyl)-NHC compoundThis invited paper describes the synthesis and study of a ruthenium-polypyridyl dye modified with a N-heterocyclic carbene. Ru-polypyridyl compounds are the most common dye used in solar fuel studies. N-heterocyclic carbenes are among the most important type of ligands studied in transition metal literature. This paper describes the combination and study of these features. University of Alberta | Publication | 2020-10-23 | James W Pearson, Riley Endean, Loorthuraja Rasu, Bergens, S. |
Modular Construction of Photoanodes with Covalently Bonded Ru- and Ir-Polypyridyl Visible Light Chromophores1,10-phenanthroline is grafted to indium tin oxide (ITO) and titanium dioxide nanoparticle (TiO2) semiconductors by electroreduction of 5-diazo-1,10-phenanthroline in 0.1 M H2SO4. The lower and upper potential limits (−0.20 and 0.15 VSCE, respectively) were set to avoid reduction and oxidation of the 1,10-phenanthroline (phen) covalently grafted at C5 to the semiconductor. The resulting semiconductor-phen ligand (ITO-phen or TiO2-phen) was air stable, and was bonded to Ru- or Ir- by reaction with cis-[Ru(bpy)2(CH3CN)2]2+ (bpy = 2,2′-bipyridine) or cis-[Ir(ppy)2(CH3CN)2]+ (ppy = ortho-Cphenyl metalated 2-phenylpyridine) in CH2Cl2 and THF solvent at 50 °C. Cyclic voltammetry, X-ray photoelectron spectroscopy, solid-state UV–vis, and inductively coupled plasma–mass spectrometry all confirmed that the chromophores SC-[(phen)Ru(bpy)2]2+ and SC-[(phen)Ir(ppy)2]+ (SC = ITO or TiO2) formed in near quantitative yields by these reactions. The resulting photoanodes were active and relatively stable to photoelectrochemical oxidation of hydroquinone and triethylamine under neutral and basic conditions. University of Alberta | Publication | 2018-07-03 | Chao Wang, Mona Amiri, Riley Endean, Octavio Martinez Perez, "Samuel Varley", "Ben Rennie", Loorthuraja Rasu, Bergens, S. |
N-Heterocyclic Carbene Organic Dyes Derived from 2,4,5,6-tetra(9H-Carbazol-9-yl)isophthalonitrile (4CzIPN) Bonded to TiO2 Surfaces University of Alberta | Publication | 2023-01-01 | Mona Amiri, Loorthuraja Rasu, Bergens, S., Octavio Martinez Perez |
Noble Metal Free, Visible Light Driven Photocatalysis Using TiO2 Nanotube Arrays Sensitized by P-doped C3N4 Quantum DotsBulk g-C3N4 is an earth-abundant, easily synthesizable, and exceptionally stable photocatalyst with an electronic bandgap of 2.7 eV. Herein, the concepts of P-doping and size quantization are combined to synthesize highly fluorescent P-doped carbon nitride quantum dots (CNPQDs) with a bandgap of 2.1 eV. CNPQDs are hosted on anatase-phase and rutilephase TiO2 nanotube array scaffolds, and examined as photoanodes for sunlight-driven water-splitting and as photocatalysts for surface catalytic reactions. Square-shaped rutile phase TiO2 nanotube arrays (STNAs) decorated with CNPQDs (CNPQD-STNA) generate 2.54 mA cm−2 under AM1.5 G simulated sunlight. A champion hydrogen evolution rate of 22 µmol h−1 corresponds to a Faradaic efficiency of 93.2%. In conjunction with Ag nanoparticles (NPs), the CNQPD-STNA hybrid is also found to be an excellent plexcitonic photocatalyst for the visible light-driven transformation of 4-nitrobenzenethiol (4-NBT) to dimercaptoazobenzene (DMAB), producing reaction completion at a laser power of 1 mW (532 nm) while Ag NP/TNA and Ag NP/STNA photocatalysts cannot complete this transformation even at 10 mW laser power. The results point the way forward
for photochemically robust, noble metal free, visible light harvesting photoacatalysts based on nanostructured heterojunctions of graphenic frameworks with TiO2. University of Alberta | Publication | 2019-10-17 | Pawan Kumar, Piyush Kar, Ajay Manuel, Ujwal Thakur, Kazi Alam, Yun Zhang, Ryan Kisslinger, Sheng Zeng, "Kai Cui", Guy Bernard, Vladimir K Michaelis, Shankar, K. |
Novel semiconductor, Re-catalyst assemblies for CO2 reductionSolar energy storage into chemical bonds is, potentially, an ideal solution to global warming remediation and effective solar energy utilization. Additionally, carbon dioxide is the key target to remove from the atmosphere, and simultaneously, a difficult but unsurpassable recipient for maximum solar utilization. In this context, a combination of a chromophore coupled to a CO2 reduction catalyst is an attractive strategy to store solar energy into C-O bonds, recycling CO2 in the process, and possibly creating a closed sustainable loop with zero carbon emissions. Ruthenium polypyridine chromophores are largely known for their outstanding ability to harvest sunlight, stability, and to be tunable [1]. On the other hand, fac-Rhenium polypyridine-tricarbonyl catalyst lead the list of highly active molecular catalyst for CO2 reduction [2]. The research in our lab aims to incorporate these two and improve their stability through immobilization on a semiconductor surface. On an indium doped-tin oxide surface we have covalently bonded a ruthenium-rhenium photocatalytic system. Ruthenium is linked to rhenium through a tetrapyrido phenazine ligand in order to accelerate the electron transfer process. Preliminary photoelectrochemical results demonstrate that photocurrents generated in the presence of CO 2, and high intensity white light can reach up to -20 μA/cm2 corresponding to the CO2 reduction. The photoelectrochemical CO2 reduction current changes as function of applied bias, showing best results at -0.5 V vs Ag/AgO in CO2 saturated 0.1M LiClO4 acetonitrile.
This manuscript is being written.
The final experiments are held up by the current lab shutdown. University of Alberta | Publication | 2020-05-10 | Octavio Martinez Perez, Bergens, S. |
Novel NHC-Bonded Ru-Polypyridine and Organic Dyes in Photoanodes that Operate in Alkaline MediaWe developed a novel, inexpensive organic dye based upon the recent, highly popular Carbazole-Cyanobenzene dye modified with a N-heterocyclic carbene (NHC) donating group. NHC groups are well-known for bonding to metal centres and strongly enhancing their activities. In this paper we describe the synthesis of this system, and remarkably, discover that they bond to semiconductors such as TiO2. The paper describes the photoactivity of the electrodes towards model solar fuels reactions under acidic, neutral, and alkaline conditions. James Pearson is an NSERC scholarship student working on another project in the group, but helped prepare the novel NCH-organic dye.
This manuscript will be submitted by the end of May, 2021. University of Alberta | Publication | 2021-05-14 | Mona Amiri, James W Pearson, Loorthuraja Rasu, Bergens, S. |
One-Step Electropolymerization of a Dicyanobenzene-Carbazole-Imidazole Dye to Prepare Photoactive Redox Polymer FilmsThis paper describes the one-step formation of the photo-redox support for all CO2 photoelectrodes we will use in the next phase of this study.
The impact factor of this journal is 5, not 3.5 as listed automatically below. University of Alberta | Publication | 2023-08-02 | Jinkun Liu, Octavio Martinez Perez, Dominic Lavergne, Loorthuraja Rasu, Elizabeth Murphy, Andy Galvez Rodriguez, Bergens, S. |
Photocatalytic mechanism control and study of carrier dynamics in CdS@C3N5 core-shell nanowiresWe present a potential solution to the problem of extraction of photogenerated holes from CdS nanocrystals and nanowires. The nanosheet form of C3N5 is a low bandgap (Eg = 2.03 eV), azo-linked graphenic carbon nitride framework formed by the polymerization of melem hydrazine (MHP). C3N5 nanosheets were either wrapped around CdS nanorods (NRs) following the synthesis of pristine chalcogenide or intercalated among them by an in situ synthesis protocol to form two kinds of heterostructures, CdS-MHP and CdS-MHPINS respectively. CdS-MHP improved the photocatalytic degradation rate of 4-nitrophenol by nearly an order of magnitude in comparison to bare CdS NRs. CdS-MHP also enhanced the sunlight-driven photocatalytic activity of bare CdS NWs for the decolorization of rhodamine B (RhB) by a remarkable 300% through the improved extraction and utilization of photogenerated holes due to surface passivation. More interestingly, CdS-MHP provided reaction pathway control over RhB degradation. In the absence of scavengers, CdS-MHP degraded RhB through the N-deethylation pathway. When either hole scavenger or electron scavenger was added to the RhB solution, the photocatalytic activity of CdS-MHP remained mostly unchanged while the degradation mechanism shifted to the chromophore cleavage (cycloreversion) pathway. We investigated the optoelectronic properties of CdS-C3N5 heterojunctions using density functional theory (DFT) simulations, FDTD simulations, time-resolved terahertz spectroscopy (TRTS) and photoconductivity measurements. TRTS indicated high carrier mobilities > 450 cm2Vs-1 and carrier relaxation times > 60 ps for CdS-MHP while CdS-MHPINS exhibited much lower mobilities < 150 cm2Vs-1 and short carrier relaxation times <20 ps. Hysteresis in the photoconductive J-V characteristics of CdS NWs disappeared in CdS-MHP confirming surface passivation. Dispersion-corrected DFT simulations indicated a delocalized HOMO and a LUMO localized on C3N5 in CdS-MHP. C3N5, with its extended π-conjugation and low bandgap can function as a shuttle to extract carriers and excitons in nanostructured heterojunctions, and enhance performance in optoelectronic devices. Our results demonstrate how carrier dynamics in core-shell heterostructures can be manipulated to achieve control over the reaction mechanism in photocatalysis. University of Alberta | Publication | 2021-04-30 | Kazi Alam, Charles Jensen, Pawan Kumar, Riley Hooper, Guy Bernard, Aakash Patidar, Ajay Manuel, "N Amer", "A. Palmgren", Narendra Chaulagain, David Purschke, John Garcia, Phillip Suwan Kirwin, Lian Shoute, "K. Cui", "S. Gusarov", "A. Kobryn", Vladimir K Michaelis, Frank Hegmann, Shankar, K. |
Plexcitonics – Fundamental principles and optoelectronic applicationsThe nanoscale confinement and coupling of electromagnetic radiation into plexcitonic modes has drawn immense interest because of the innovative possibilities for their application in light harvesting and light emitting devices (LEDs). Plexcitons arise from the coupling between two types of quasiparticles, plasmons and excitons, and can be distinguished by the strength of the coupling into strong and weak coupling regimes. Plexcitons have been used to modulate the rate of Förster-type resonance energy transfer in quantum dot assemblies and enhance the spontaneous emission rate in quantum dot LEDs. The clearest examples of a plexcitonic enhancement of photocatalytic reaction rates have been evidenced in hybrid systems wherein the strongly bound exciton found in 2D sheet-like semiconductors is coupled to the surface plasmon resonance of close-lying noble metal nanoparticles. Plexcitonic photocatalysts and solar cells aim to increase the lifetime of hot carriers and thereby enhance the quantum yields for energy harvesting. Since plexcitonics requires the placement of plasmonic and excitonic components in close proximity with one another to facilitate their coupling, it provides a rich arena for chemists and materials scientists to form deterministic and non-deterministic arrays and heterojunctions involving noble metal thin films and nanostructures, quantum dots and dye molecules. This review summarizes the dynamics of plexcitons in the various composite systems and provides an overview of the latest theoretical and experimental developments in the field of plexcitonics. University of Alberta | Publication | 2019-01-02 | Ajay Manuel, Aaron Kirkey, Najia Mahdi, Shankar, K. |
Solid-Phase Synthesis and Photoactivity of Ru-Polypyridyl Visible Light Chromophores Bonded Through Carbon to Semiconductor Surfaces1,10-phenanthroline (phen) was grafted to either indium tin oxide (ITO), fluorine-doped tin oxide (FTO), or titanium dioxide nanoparticles (TiO2) by electrochemical reduction of 5-diazo-phen. The phen ligand is bonded to the semiconductor (SC) at C5, and it can be handled in air. The semiconductor-phen (SC-phen) complexes displace both CH3CN ligands from either cis-[Ru(Mebipy)2(CH3CN)2]2+ (Mebipy = 4,4’-methyl 2,2’-bipyridine), cis-[Ru(tBubipy)2(CH3CN)2]2+ (tBubipy = 4,4’-tert-butyl 2,2’-bipyridine), or cis-[Ru(pheno)(bipy) (CH3CN)2]2+ (bipy = 2,2’-bipyridine; pheno = 1,10-phenanthroline- 5,6-dione) dissolved in DCM/THF (4h, 70 °C) to form the corresponding surface-bound SC-[(phen)Ru(bipyridyl)2]2+ complexes. The identities of SC-[(phen)Ru(Mebipy)2]2+, SC-[(phen)Ru(tBubipy)2]2+, and SC-[(phen)Ru(pheno)(bipy)]2+ (SC = ITO, FTO or TiO2) chromophores were confirmed by X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP-MS), UV-vis and reflectance infrared spectroscopies, and cyclic voltammetry (CV). The data were compared to Ru-polypyridyl control compounds dissolved in solution wherever possible. A facile ketone-amine condensation reaction between SC-[(phen)Ru(pheno)(bipy)]2+ and [Ru(1,10-phenthroline-5,6-diamine)(bipy)2]2+ in ethanol (80 °C, 1 h) formed the dinuclear, bound chromophore SC-[(phen)Ru(bipy)(tpphz)Ru(bipy)2]4+ (tpphz = tetrapyrido[3,2-a:2’,3’-c:3”,2”-h:2”’,3”’-j]phenazine). Photoelectrochemical oxidation of hydroquinone and triethylamine under acidic, neutral, or basic conditions showed that the SC-chromophore photoanodes are active, and that TiO2-[(phen)Ru(Mebipy)2]2+ is the most active and stable in the series.
University of Alberta | Publication | 2020-07-15 | Mona Amiri, Octavio Martinez Perez, Riley Endean, Loorthuraja Rasu, Prabin Nepal, "Shuai Xu", Bergens, S. |
Sunlight-driven water-splitting using two dimensional carbon based semiconductorsThe overwhelming challenge of depleting fossil fuels and anthropogenic carbon emissions has driven research into alternative clean sources of energy. To achieve the goal of a carbon neutral economy, the harvesting of sunlight by photocatalysts to split water into hydrogen and oxygen is an expedient approach to fulfill energy demand in a sustainable way along with reducing the emission of greenhouse gases. Even though the past decades have witnessed intensive research into inorganic semiconductor photocatalysts, the quantum efficiencies for hydrogen production from visible photons remain too low for the large scale deployment of this technology. Visible light absorption and efficient charge separation are two key necessary conditions for achieving the scalable production of hydrogen from water. Two-dimensional carbon based nanoscale materials such as graphene oxide, reduced graphene oxide, carbon nitride, modified 2D carbon frameworks and their composites have emerged as potential photocatalysts due to their astonishing properties such as superior charge transport, tunable energy levels and bandgaps, visible light absorption, high surface area, easy processability, quantum confinement effect, and high photocatalytic quantum yields. The feasibility of structural and chemical modification to optimize visible light absorption and charge separation makes carbonaceous semiconductors promising candidates to convert solar energy into chemical energy. In the present review, we have summarized the recent advances in 2D carbonaceous photocatalysts with respect to physicochemical and photochemical tuning for solar light mediated hydrogen evolution. University of Alberta | Publication | 2018-05-24 | Pawan Kumar, Rabah Boukherroub, Shankar, K. |
TiO 2-HfN Radial Nano-Heterojunction: A Hot Carrier Photoanode for Sunlight-Driven Water-SplittingThe lack of active, stable, earth-abundant, and visible-light absorbing materials to replace plasmonic noble metals is a critical obstacle for researchers in developing highly efficient and cost-effective photocatalytic systems. Herein, a core–shell nanotube catalyst was fabricated consisting of atomic layer deposited HfN shell and anodic TiO2 support layer with full-visible regime photoactivity for photoelectrochemical water splitting. The HfN active layer has two unique characteristics: (1) A large bandgap between optical and acoustic phonon modes and (2) No electronic bandgap, which allows a large population of long life-time hot carriers, which are used to enhance the photoelectrochemical performance. The photocurrent density (≈2.5 mA·cm−2 at 1 V vs. Ag/AgCl) obtained in this study under AM 1.5G 1 Sun illumination is unprecedented, as it is superior to most existing plasmonic noble metal-decorated catalysts and surprisingly indicates a photocurrent response that extends to 730 nm. The result demonstrates the far-reaching application potential of replacing active HER/HOR noble metals such as Au, Ag, Pt, Pd, etc. with low-cost plasmonic ceramics. University of Alberta | Publication | 2021-11-01 | Sheng Zeng, Triratna Parmeshwar Muneshwar, Saralyn Riddell, Ajay Manuel, Ehsan Vahidzadeh, Pawan Kumar, Ryan Kisslinger, Kazi Alam, Alexander E Kobryn, Sergey Gusarov, Ken Cadien, Shankar, K. |
Tunable Absorption and Emission in Mixed Halide Bismuth Oxyhalides for Photoelectrochemical Water SplittingLayered materials such as bismuth oxyhalides (especially BiOBr and BiOI) are the focus of research attention as photocatalysts due to their visible light activity, unique electronic structure, excellent chemical and physical stability, and internal electric field effect. We report the solvothermal synthesis of BiOX solid solutions with continuously tunable optical absorption and photoluminescence spectra. We employed solid-state nuclear magnetic resonance (SSNMR) characterization to probe the local environment around Bi atoms. We determined that the synthesized BiOX solid solutions exhibit good agreement with Vegard’s law through refinement of the lattice parameters using powder X-ray diffraction (PXRD) and complementary atomic-level 209Bi SSNMR spectroscopy. The solid solution strategy makes it possible to modulate the light absorption of BiOX and tune the redox potentials corresponding to the electronic band edges to drive chemical reactions. The BiOX solid solutions demonstrated superior performance in sunlight-driven photoelectrochemical and photocatalytic water splitting. The best performing solid solution generated a photocurrent density of 1.5 mA cm–2 and a H2 evolution rate of 16.32 μmol g–1 h–1 for photoelectrochemical water splitting and photocatalytic hydrogen generation, respectively, and the enhanced performance is attributed to a higher specific surface area, a shorter carrier transit distance, and a higher electron density. The approximate order of magnitude performance improvement compared to pristine BiOBr and BiOI photoanodes was primarily due to optimal light harvesting combined with adequate thermodynamic driving force to drive water oxidation and proton reduction. University of Alberta | Publication | 2024-01-01 | Md Masud Rana, Kazi Alam, Narendra Chaulagain, John Garcia, Navneet Kumar, Damini Vrushabendrakumar, Harshitha Rajashekhar, Guy Bernard, Al Meldrum, Vladimir K Michaelis, Shankar, K. |
Vapor Deposition of Semiconducting P Allotropes into TiO2 Nanotube Arrays for Photo-Electrocatalytic Water SplittingRecent evidence of exponential environmental degradation will demand a drastic shift in research and development toward exploiting alternative energy resources such as solar energy. Here, we report the successful low-cost and easily accessible synthesis of hybrid semiconductor@TiO2 nanotube photocatalysts. In order to realize its maximum potential in harvesting photons in the visible-light range, TiO2 nanotubes have been loaded with earth-abundant, low-band-gap fibrous red and black phosphorus (P). Scanning electron microscopy– and scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron microscopy, and UV–vis measurements have been performed, substantiating the deposition of fibrous red and black P on top and inside the cavities of 100-μm-long electrochemically fabricated nanotubes. The nanotubular morphology of titania and a vapor-transport technique are utilized to form heterojunctions of P and TiO2. Compared to pristine anatase 3.2 eV TiO2 nanotubes, the creation of heterojunctions in the hybrid material resulted in 1.5–2.1 eV photoelectrocatalysts. An enhanced photoelectrochemical water-splitting performance under visible light compared with the individual components resulted for the P@TiO2 hybrids. This feature is due to synergistically improved charge separation in the heterojunction and more effective visible-light absorption. The electronic band structure and charge-carrier dynamics are investigated in detail using ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy to elucidate the charge-separation mechanism. A Fermi-level alignment in P@TiO2 heterojunctions leads to a more reductive flat-band potential and a deeper valence band compared to pristine P and thus facilitates a better water-splitting performance. Our results demonstrate effective conversion efficiencies for the nanostructured hybrids, which may enable future applications in optoelectronic applications such as photodetectors, photovoltaics, photoelectrochemical catalysts, and sensors. University of Alberta | Publication | 2019-05-09 | "Ebru Uzer", Pawan Kumar, Ryan Kisslinger, Piyush Kar, Sheng Zeng, Shankar, K., "Tom Nilges" |
Vapor growth of binary and ternary phosphorus-based semiconductors into TiO2 nanotube arrays and application in visible light driven water splittingWe report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12) were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO2 nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO2 emerged to be the most active among the polyphosphide@TiO2 materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO2. University of Alberta | Publication | 2019-05-24 | "Ebru Uzer", Pawan Kumar, Ryan Kisslinger, Piyush Kar, Ujwal Thakur, Shankar, K., "Tom Nilges" |
Water-splitting photoelectrodes consisting of heterojunctions of carbon nitride with a p-type low bandgap double perovskite oxideQuinary and senary non-stoichiometric double perovskites such as Ba2Ca0.66Nb1.34-xFexO6-δ (BCNF) have been utilized for gas sensing, solid oxide fuel cells and thermochemical CO2 reduction. Herein, we examined their potential as narrow bandgap semiconductors for use in solar energy harvesting. A cobalt co-doped BCNF, Ba2Ca0.66Nb0.68Fe0.33Co0.33O6-δ (BCNFCo), exhibited an optical absorption edge at ~ 800 nm, p-type conduction and a distinct photoresponse upto 640 nm while demonstrating high thermochemical stability. A nanocomposite of BCNFCo and g-C3N4 (CN) was prepared via a facile solvent assisted exfoliation/blending approach using dichlorobenzene and glycerol at a moderate temperature. The exfoliation of g-C3N4 followed by wrapping on perovskite established an effective heterojunction between the materials for charge separation. The conjugated 2D sheets of CN enabled better charge migration resulting in increased photoelectrochemical performance. A blend composed of 40 wt% perovskite and CN performed optimally, whilst achieving a photocurrent density as high as 1.5 mA cm-2 for sunlight-driven water-splitting with a Faradaic efficiency as high as ~ 88%. University of Alberta | Publication | 2021-03-01 | Pawan Kumar, Suresh Mulmi, Devika Laishram, Kazi Alam, Ujwal Thakur, V Thangadurai, Shankar, K. |