The photoelectrochemical (PEC) production of hydrogen uses solar energy to split water into hydrogen and oxygen. The process requires special semiconductors, the PEC materials and catalysts to split the water. Precious metals have been used as catalysts attached to the semiconductors, including platinum, ruthenium and iridium - but these are too expensive for large scale production.
Announced December 22, 2015, researchers at the Energy Department's National Renewable Energy Laboratory (NREL) have begun to examine molecular catalysts outside of the liquid solution they are normally studied in to see if they could attach the catalyst directly onto the surface of the semiconductor. They were able to put a layer of titanium dioxide (TiO2) on the surface of the semiconductor and bond the molecular catalyst to the TiO2. Their work showed molecular catalysts can be as highly active as the precious metal-based catalysts in the process that produces hydrogen.