Hybrid functionals studies of structural and electronic properties of ZnxCd(1−x)S and (ZnxCd1−x)(SexS1−x) solid solution photocatalysts

The structural and electronic properties of the wurtzite Zn_xCd_1−xS and (Zn_xCd_1−x)(Se_xS_1−x) alloys are calculated using density functional theory calculations with HSE06 hybrid exchange-correlation functional. Special quasirandom structures are used to describe the disordered alloys, for x = 0.125, 0.25, 0.375, 0.5, 0.625, 0.75 and 0.875, respectively. Our calculations reveal that Zn_xCd_1−xS alloy with the appropriate Zn doping concentration not only causes the elevation of the conduction band minimum energy, but also increase the mobility of photogenerated holes and electrons, which well explains the high photocatalytic activity and stability of Zn_0.2Cd_0.8S alloy under a long-term light irradiation. Compared with Zn_xCd_1−xS alloy, (Zn_xCd_1−x)(Se_xS_1−x) alloy holds greater potential to simultaneously meet band gap, band edge, and mobility criteria for water splitting. Theoretical results predict that (Zn_xCd_1−x)(Se_xS_1−x) alloy with the ZnSe concentration in the range from 0.38 to 0.75 could be a more promising candidate than Zn_0.2Cd_0.8S alloy for photoelectrochemical hydrogen production through water splitting.