Photocatalysts harness sunlight to enhance chemical reactions for several applications that include reducing pollution levels in air and water and providing a potential renewable hydrogen energy cycle. The research project centers on linking the subtle features of the atomic arrangements in ceramic materials with their effectiveness as photocatalysts. By understanding the atomic-scale workings of ceramic photocatalysts, new and improved materials can be designed. Direct experimental studies will be performed and supported by detailed atomic-scale computer simulations in order maximize the knowledge gained. The development of photocatalysts for generating hydrogen from water could have profound political, economical, and environmental impacts. Removing CO2 from power plant operations will reduce the total greenhouse gas emissions in the US by ~35%, while hydrogen-powered vehicles will lead to an additional ~25% reduction. The educational aspects of the program highlight interdisciplinary work between undergraduates in art and engineering to attract a new generation of scientists and engineers to the field.
TECHNICAL DETAILS
Layered Aurivillius ceramics will be used as the host system to allow precise control of the Ti-O, Nb-O, and Ta-O bond lengths over a wide range. The Aurivillius crystal will allow a direct evaluation of the effects of the layered structure and ferroelectric domains on charge recombination, and will provide a host for dilute doping of aliovalent cations. The distinct structural characteristics of the complex Aurivillius phases provide a framework in which to improve upon the current state-of-the-art TiO2 photocatalysts. Very little additional performance improvement is anticipated by using simple ceramics such as TiO2, necessitating the study of complex ceramics with different structural features. Instead of searching for methods for incremental improvements, layered ceramics present the opportunity to make breakthrough advances in understanding and performance of photocatalysts. The experimental work will center on the use of diffraction, complemented with X-ray absorption and photoelectron spectroscopy to characterize the structures in detail. Density functional theory computer simulations will be performed using both energy-minimized structures and intentionally strained structures to track the electronic band structure, defect energies, and dopant clustering tendencies in parallel with experiment. By linking the simulation and experimental results, phenomenological models will be developed by the research team that will allow prediction of catalytic behavior and set the foundation for future work focused on surface structures and energetics. The experimental aspects of the project will allow the students involved to take full advantage of new national facilities for X-ray and neutron scattering, and to develop expertise in these areas.
