The Efficient Photoelectrochemical Reduction of Aqueous CO2: Carbon Sequestration Via Conversion of Carbon Dioxide to Alcohols

There has been increasing interest in artificial photosynthetic schemes for converting the greenhouse gas, carbon dioxide, into a value added fuel such as methanol. Although photoelectrochemical schemes, utilizing a semiconductor-electrolyte interface that is responsive to sunlight have been considered for this application, all reports to date indicate that excessive overpotentials are required. The observed activation potential cannot be accommodated by insolation available at the terrestrial surface, and thus, photoelectrochemical cells have not been observed to actually convert light energy to chemical energy in CO2 reduction systems. However, we have developed a catalytic system that efficiently and selectively converts carbon dioxide to methanol and higher order alcohols. The system couples a semiconducting electrode such as p-GaP with a substituted pyridinium catalyst. In certain cases, we find that the reaction can be driven solely with visible or near UV light to yield faradaic efficiencies approaching 100% at potentials well below the thermodynamic potential required in the absence of light. In addition to methanol, isopropanol can be photochemically synthesized by using ring substituted pyridinium catalysts.

Autobiography

Andrew Bocarsly received his Bachelor of Science degree jointly in chemistry and physics from UCLA in 1976, and his Ph.D. in chemistry from M.I.T. in 1980. He has been a member of the Princeton University, Chemistry Department faculty for twenty-nine years. Professor Bocarsly has published over 175 papers in peer reviewed journals and co-authored six patents. Research in his laboratory is focused on the materials chemistry associated with elevated temperature proton exchange membrane fuel cells, including composite membranes for elevated temperature cells and electrocatalysts for direct alcohol fuel cells; visible light photoelectrochemistry for the conversion of carbon dioxide to alcohols; cyanogel sol-gel processing routes to refractory metal alloys and nanostructures; and molecule-based multielectron photoinduced charge transfer processes.

Professor Bocarsly serves as a consultant and contractor to various fuel cell and alternate energy companies. He is a founder and President of the Science Advisory Board for Liquid Light Inc., a company formed to commercialize the formation of organic commodity chemicals from carbon dioxide using alternate energy sources. Professor Bocarsly has received an Alfred P. Sloan Fellowship, the Sigma Xi (Princeton Section) Science Educator Award, the American Chemical Society-Exxon Solid State Chemistry award, and has served as the electrochemistry editor for Methods in Materials Research: A Current Protocols Publication. Presently, he is serving as a volume editor for Structure and Bonding in the area of fuel cells and batteries.

Professor Bocarsly can be reached by email at bocarsly@princeton.edu.