Silver cocatalyst-concentration dependence of overall water splitting performance over silver-inserted solid-state heterojunction photocatalyst composed of zinc rhodium oxide and bismuth vanadium oxide

We loaded silver (Ag), as a hydrogen (H-2)-evolution cocatalyst, selectively onto zinc rhodium oxide (ZnRh2O4 (ZRO)), as a H-2-evolution photocatalyst, with various amounts of the Ag cocatalyst in a heterojunction photocatalyst, Ag-inserted ZRO and bismuth vanadium oxide (Bi4V2O11(BVO), ZRO/Ag/BVO). The selective loading of the Ag cocatalyst was realized by a photodeposition method by utilizing the bandgap difference between ZRO (1.2 eV) and BVO (1.7 eV), and the amount of deposited Ag was controlled by the photodeposition time to generate Ag/ZRO/Ag/BVO with up to 4.0 wt% of Ag cocatalyst. All the prepared Ag/ZRO/Ag/BVO proceeded overall water splitting under red light irradiation at a wavelength of 700 nm, enhancing the stoichiometric evolutions of H-2 and O-2 from water. Also, the apparent quantum efficiency increased up to 1.1 wt% of Ag cocatalyst and then tended to saturate in the measurement range up to 4.0 wt%.