Cocatalyst free Z-schematic enhanced H2 evolution over LaVO4/BiVO4 composite photocatalyst using Ag as an electron mediator

A novel cocatalyst free Z-schematic photocatalytic system of Ag/LaVO4/BiVO4 was successfully fabricated for clean hydrogen fuel evolution. The spherical nanoparticles of LaVO4 were prepared in solution combustion method for the first time using glycine as a fuel, BiVO4 was deposited onto LaVO4 through a deposition precipitation method and Ag was loaded on the surface of LaVO4/BiVO4 composite by photoreduction method. The composites were characterized by XRD, UV vis DRS, SEM, TEM, EDS and XPS to ensure the successful integration of Ag or (and) BiVO4 with LaVO4. A series of photocatalytic H-2 evolution experiments, employing Na2S and Na2SO3 as hole scavengers, showed that the Ag/LaVO4/BiVO4 composite exhibited a superior photocatalytic performance compared to single LaVO4 or BiVO4. Although BiVO4 cannot be used for H-2 evolution, it can significantly enhance the H-2 evolution performance of LaVO4 through a Z-scheme mechanism with Ag as an electron mediator. Moreover, investigations on photoluminescence and fluorescence lifetime measurements demonstrated the greater separation efficacy of photoinduced excitons in the Z-scheme Ag/ LaVO4/BiVO4 photocatalytic system. This newly constructed LaVO4 based Z-scheme system exhibits promising photocatalytic H-2 evolution activity with significant longevity and will be useful for potential applications in energy driven technologies.