Hydrogen evolution by photocatalysis

The production of fuels from sunlight represents one of the major challenges to the development of a sustainable energy system. Hydrogen is the simplest fuel to produce and while platinum and other noble metals are efficient catalysts for photo-chemical hydrogen evolution, earth-abundant alternatives are needed for large-scale use. We show that cubane-like clusters containing molybdenum and sulfur efficiently catalyze the evolution of hydrogen when coupled to a p-type Si semiconductor harvesting the red light portion of the solar spectrum.

We show that higher photocurrents results when a silicon pn junction absorber is used. With a Ti/TiO2 protection layer added on the pn-junction the photocathode becomes durable even when oxygen is present in high concentrations. The current densities at the reversible potential match the requirements of a photochemical hydrogen production system with energy conversion efficiency in excess of 10%.

Illustration of a tandem device in which two semiconductor materials are used on either side of a proton exchange membrane to run the water splitting process. Example of silicon photocathodes created for experimental use.
With DTU Physics (CASE & CINF) and Haldor Topsøe A/S.