Water Splitting Using a Photocatalyst with Single-Atom Reaction Sites

Nanosheets doped with isolated single-atom reaction sites for hydrogen evolution are a potential means of suppressing recombination during photocatalytic water splitting. Oxide nanosheets show higher activity during photocatalytic hydrogen evolution from CH3OH/water after doping with single-atom reaction sites in the lattice. However, water splitting into H-2 and O-2 from pure water has not yet been achieved on such materials because backward reactions, such as oxygen reduction, are also accelerated at these same reaction sites. In the present study, calcium niobate nanosheets incorporating Rh single-atom reaction sites covered with ultrathin NiOx atomic layers are fabricated. The nanosheets having a Ni/Rh atomic ratio of 7/1 are found to promote evolution of H-2 and O-2 from water. In this system, the ultrathin NiOx atomic layers prevent oxygen penetration but allow H+ to access the Rh reaction sites, thus promoting photocatalytic water splitting for H-2 and O2 production. This is the first demonstration of perfect water splitting using a nanosheet photocatalyst with single-atom reaction sites.