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

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 S₂O₈^2- 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.