Overall pure-water splitting under visible-light irradiation was accomplished utilizing a solid-state heterojunction photocatalyst following the Z-scheme mechanism. Zinc rhodium oxide (ZnRh2O4) and defective silver antimonate (Ag1–x SbO3–y ) as hydrogen (H2)- and oxygen (O2)-evolution photocatalysts, respectively, were connected with silver (Ag) to prepare a solid-state Z-scheme photocatalysis system (ZnRh2O4/Ag/Ag1–x SbO3–y ). In this system, Ag acted as a solid-state electron mediator for the transfer of electrons from the conduction band of Ag1–x SbO3–y to the valence band of ZnRh2O4. Utilizing the thus-constructed ZnRh2O4/Ag/Ag1–x SbO3–y photocatalyst, the simultaneous liberation of H2 and O2 from pure water at a molar ratio of ∼2:1 was achieved under irradiation with visible light at over 500 nm.

We have prepared a solid-state heterojunction photocatalyst, in which zinc rhodium oxide (ZnRh2O4) and bismuth vanadium oxide (Bi4V2O11) as hydrogen (H2) and oxygen (O2) evolution photocatalysts, respectively, were connected with silver (Ag, ZnRh2O4/Ag/Bi4V2O11).

We recently reported the synthesis of a solid-state heterojunction photocatalyst consisting of zinc rhodium oxide (ZnRhO) and bismuth vanadium oxide (BiVO), which functioned as hydrogen (H) and oxygen (O) evolution photocatalysts, respectively, connected with silver (Ag). Polycrystalline BiVO (p-BiVO) powders were utilized to form ZnRhO/Ag/p-BiVO, which was able to photocatalyze overall pure-water splitting under red-light irradiation with a wavelength of 700 nm (R. Kobayashi et al., J. Mater. Chem. A, 2016, 4, 3061). In the present study, we replaced p-BiVO with a powder obtained by pulverizing single crystals of BiVO (s-BiVO) to form ZnRhO/Ag/s-BiVO, and demonstrated that this heterojunction photocatalyst had enhanced water-splitting activity. In addition, ZnRhO/Ag/s-BiVO was able to utilize nearly the entire range of visible light up to a wavelength of 740 nm. These properties were attributable to the higher O evolution activity of s-BiVO.