Light-Driven Water Splitting in the Dye-Sensitized Photoelectrosynthesis Cell

Abstract

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. Light-driven water-splitting devices, also known as dye-sensitized photoelectrosynthesis cells (DSPECs), show promise and are based on molecular light absorption and catalysis which occur at the surfaces of nanocrystalline oxide semiconductors. Absorption of sunlight by surface-attached molecules leads to electron injection into the semiconductor conduction band followed by catalyst activation. Light-driven water splitting occurs by repetition of this cycle four times at a photoanode with solar fuels generated at the cathode. The underlying design of the DSPEC is based on this photoelectrochemical approach. Light-driven water splitting is made possible by the recent development of molecular water oxidation catalysts. With the components finally available to explore the DSPEC in detail, design principle guidelines are rapidly emerging which will lay the foundation for these devices to harness and utilize solar energy, night or day.