Cosubstituting effects of copper(I) and gallium(III) for ZnGa2S4 with defect chalcopyrite structure on photocatalytic activity for hydrogen evolution

• Cosubstitution of Cu(I) with Ga(III) gave VIS response for ZnGa2S4 photocatalyst.
• The photocatalytic activities of Pd/Zn1−2x(CuGa)xGa2S4 depended on the composition.
• Pd/Zn0.4(CuGa)0.3Ga2S4 photocatalyst gave 15% of an apparent quantum yield at 420 nm.
• Cosubstitution is effective for the development of VIS-light driven photocatalysts.
• Pd/Zn0.4(CuGa)0.3Ga2S4 and Rh/CuGa5s8 were active for solar H2 production.

ZnGa2S4 with a 3.4 eV band gap and defect chalcopyrite structure showed photocatalytic activity for hydrogen evolution from an aqueous solution containing SO32- and S2− as electron donors under ultraviolet-light irradiation. Cosubstitution of Cu(I) with Ga(III) for Zn(II) sites in ZnGa2S4 gave visiblelight response. The photocatalytic activities of Zn1−2x(CuGa)xGa2S4 (x = 0.15–0.50) depended on the value x of the composition. Pd(0.5 wt%)-loaded Zn0.4(CuGa)0.3Ga2S4 (x = 0.3) showed the highest activity with 15% of an apparent quantum yield at 420 nm. The dependence of the photocatalytic activity on the composition was due to the balance among the number of absorbed photons for photocatalytic reaction, the mobilities of electron and hole at conduction and valence bands, and the conduction band level affecting the driving force for reducing water to hydrogen. Pd(0.5 wt%)-loaded Zn0.4(CuGa)0.3Ga2S4 and Rh(0.5 wt%)-loaded CuGa5S8 (x = 0.5) were active for solar hydrogen production using a solar simulator.

Cosubstitution of Cu(I) with Ga(III) for Zn(II) sites in ZnGa2S4 gave visible-light response to the ZnGa2S4 host photocatalyst. Pd(0.5 wt%)-loaded Zn0.4(CuGa)0.3Ga2S4 (x = 0.3) showed the high activity with 15% of an apparent quantum yield at 420 nm for hydrogen evolution from an aqueous solution containing SO32– and S2– as electron donors. This photocatalyst was active for solar hydrogen production using a solar simulator. Involving Cu(I) with charge compensation by cosubstituting another element is an excellent band engineering for narrowing band gap of photocatalysts and enhancing the photocatalytic property.Figure optionsDownload high-quality image (106 K)Download as PowerPoint slide