May 15, Bart Bartlett, University of Michigan
Special Joint Seminar with the Department of Chemistry
4:00 PM in Room 203, 8 St. Mary’s Street
Refreshments served at 3:45 PM
Designing Chemically Robust Metal Oxides for Visible-Light Photocatalysis: toward Solar Z-Scheme Water Splitting
Abstract: Solar driven water splitting for large-scale hydrogen fuel production from semiconductor photo-electrodes has the potential to provide energy on large scale from renewable, sustainable sources. Our research focuses on the kinetically more demanding oxygen-evolution reaction, and we prepare thin film metal oxide photoanodes by low-temperature, solution-based processes. One promising light absorber is TiO2:(Nb,N) where Nb and N substitute for Ti and O on their respective lattice sites in anatase. These materials are prepared by sol-gel processing followed by annealing in flowing ammonia. We observe a band-gap energy as low as 2.0 eV at 25% Nb and 2% N. In conjunction with a RuO2 catalyst, powdered TiO2:(Nb,N) evolves O2. A second class of materials we study is the transition-metal tungstates, and we have prepared our most promising candidate, CuWO4, by several routes: electrochemical deposition, sol-gel processing, and spray pyrolysis. These methods afford highly reproducible and robust CuWO4 thin-film electrodes on transparent conducting substrates. CuWO4 is an n–type semiconductor with a band-gap energy of ~2.4 eV. CuWO4 thin films photooxidize water with simulated solar radiation with a nearly quantitative Faradaic efficiency for O2 evolution at no applied bias in the presence of the sacrificial electron acceptor, [Fe(CN)6]3–. Most important, these thin-film electrodes are stable against photocorrosion when illuminated with visible light at neutral pH, a significant improvement to the more commonly studied photoanode, WO3. Current efforts are aimed at preparing complex tungstates that absorb lower energy light to improve the quantum yield.
Biography: Bart Barlett is an Assistant Professor of Chemistry at the University of Michigan. The Bartlett group focuses on inorganic synthesis to prepare compositionally complex materials for applications in renewable energy. The two main thrusts of their program are electrical energy storage in ion insertion materials and solar energy conversion in light-harvesting metal oxides. A central theme of the program is the interplay between structure, composition, and physical properties such as electrochemistry and absorption. Their current efforts are aimed at controlling morphology and composition in nanoscale materials.
Faculty Host: Linda Doerrer