Z-scheme water splitting using particulate semiconductors immobilized onto metal layers for efficient electron relay

A major challenge in developing high-performing Z-scheme water splitting systems lies in achieving efficient transfer of electrons between the H2 and O2 evolution photocatalysts. Here, we report a Z-scheme system consisting of H2 evolution photocatalyst (HEP)/metal layer (M)/O2 evolution photocatalyst (OEP), taking SrTiO3:La,Rh/Au/BiVO4 as a prototype. SrTiO3:La,Rh/Au/BiVO4 systems exhibit photocatalytic activities for overall water splitting that are 6 and 20 times higher than powder suspensions and SrTiO3:La,Rh/BiVO4 systems without metal layers, respectively. The SrTiO3:La,Rh/Au/BiVO4 system achieves an apparent quantum yield of 5.9% under monochromatic light irradiation at 418 nm and a solar-to-hydrogen conversion efficiency of 0.2%. The high performance of this system is due to the presence of the Au layer that transfers photogenerated electrons from BiVO4 to SrTiO3:La,Rh in an effective manner. The present study offers a new design concept for HEP/M/OEP solid-state devices to overcome the limitations of earlier Z-scheme systems and thus enable efficient photocatalytic water splitting.