Photocatalytic water splitting using semiconductor photocatalysts is considered a promising way to break away from dependence on fossil fuels by generating sustainable hydrogen from solar energy. As a strategy to improve the efficiency of photocatalytic water splitting, cocatalyst loading onto the surface of semiconductor photocatalysts is used frequently, especially to boost hydrogen evolution reaction (HER). Therein, noble metals such as Pt and RuOx have been used as HER auxiliary catalysts.
In this study, we demonstrate that NiBHT, a type of metal-organic structure (MOF), can function as a non-precious metal HER cocatalyst. By combining NiBHT with aluminum-doped strontium titanate (SrTiO3:Al), a typical water splitting photocatalyst, attains overall water splitting (generation of H2 and O2 at a stoichiometric ratio of 2:1) is achieved upon photoirradiation. NiBHT is able to selectively split water without promoting reverse water formation from the generated H2 and O2, and the reduction of O2, thereby having suitable reaction selectivity as an HER cocatalyst. The photocatalytic system NiBHT/CoOx/SrTiO3:Al (CoOx is cobalt oxide as an oxygen evolution reaction (OER) cocatalyst) shows particularly stable photocatalysis, with a water reduction efficiency of 6.5% at 350 nm illumination.
