Dye sensitized photoelectrosynthesis cells for making solar fuels: From basic science to prototype devices

Abstract

As in natural photosynthesis, artificial photosynthesis integrates solar energy conversion and storage in processes that produce solar fuels. The targets are water splitting into H2 and O2 or solar-driven reduction of CO2 by water to carbon-based fuels. The dye sensitized photoelectrosynthesis cell (DSPEC) offers a hybrid approach. It combines molecular-level light absorption and catalysis with the high energy bandgap properties of n-type (TiO2, SnO2) or p-type (NiO) semiconductor oxides. The DSPEC functions as an artificial leaf by using molecular assemblies that both absorb light and catalyze water oxidation at a photoanode or proton/CO2 reduction at a photocathode. It draws on research on dye-sensitized solar cells (DSSCs) and advances in molecular light-harvesting and catalysis to address the more complex set of challenges arising from coupling single photon/single electron absorption/injection events with multi-electron/multi-proton half-reactions for water oxidation and CO2 reduction. This account provides a summary of DSPEC research at the University of North Carolina Energy Frontier research Center on Solar Fuels. By using a team-based approach, the Center has made significant progress in research on molecular assemblies, catalysis of water oxidation and CO2 reduction, understanding and controlling interfacial electron transfer dynamics, the use of semiconductor oxides, and surface assembly and stabilization, all of which are integrated in DSPEC photoanodes for water oxidation and photocathodes for water and CO2 reduction.