Photocatalytic water oxidation over BiVO4 with interface energetics engineered by Co and Ni-metallated dicyanamides

Abstract

Photocatalytic water oxidation based on semiconductors usually suffers from poor charge transfer from the bulk to the interface, which is necessary for oxygen generation. Here, we construct a hybrid artificial photosynthesis system for photocatalytic water oxidation. The system consists of BiVO4 as the light harvester, a transitional metal complex (M(dca)2, M = Co, Ni, dca: dicyanamide) as the water oxidation catalyst, and S2O82− as a sacrificial electron acceptor. The system exhibits enhanced oxygen evolution activity when M(dca)2 is introduced. The BiVO4/Co(dca)2 and BiVO4/Ni(dca)2 systems exhibit excellent oxygen evolution rates of 508.1 and 297.7 μmol/(h·g) compared to the pure BiVO4 which shows a photocatalytic oxygen evolution rate of 252.2 μmol/(h·g) during 6 h of photocatalytic reaction. Co(dca)2 is found to be more effective than Ni(dca)2 as a water oxidation catalyst. The enhanced photocatalytic performance is ascribed to the M(dca)2-engineered BiVO4/electrolyte interface energetics, and to the M(dca)2-catalyzed surface water oxidation. These two factors lead to a decrease in the energy barrier for hole transfer from the bulk to the surface of BiVO4, which promotes the water oxidation kinetics.