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

- Synthesis of LaVO4 nanoparticles by solution combustion method.
- Direct Z-scheme photocatalytic system of LaVO4/BiVO4 without use of redox mediators.
- Metallic Ag acts as electron mediator for enhanced H2 evolution of Ag/LaVO4/BiVO4.
- Efficiency of Ag/LaVO4/BiVO4 is ascribed to longer life span of charge carriers.

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 H2 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 H2 evolution, it can significantly enhance the H2 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 H2 evolution activity with significant longevity and will be useful for potential applications in energy driven technologies.

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