Semiconductor Catalysts for Oxygen and Hydrogen Evolution Reactions

Semiconductors are the workhorse material of solar cells for the conversion of solar energy into electrical current. Similarly, catalysts play a major role in the electrochemical water splitting, providing efficient shuttles for the exchange of charge carriers between the solid and electrolyte. Simultaneous use of semiconductors as catalysts is under an ongoing research effort bringing together these different research fields toward a common target of renewable hydrogen production. In this Review, we summarize the common concepts from photovoltaics and electrocatalysis, highlighting the available literature on the catalytic properties of semiconductors toward hydrogen evolution and oxygen evolution reactions. The overpotential, photovoltage, and Tafel slope are considered as the main figures of merit for the water splitting reactions. The surveyed literature presents a broad span of Tafel slopes highlighting the complexity of the photoelectrode processes and rate-determining steps of the water splitting reactions. This work aims to provide arguments and suggestions for investigations of the common catalytic properties of semiconductors during the quest for the efficient photoelectrodes.