Efficient and stable photocatalytic hydrogen production from water splitting over Zn_xCd_1-xS solid solutions under visible light irradiation

A simple co-precipitation method was employed to synthesize a series of cubic zinc-blende phase of Zn_xCd_1-xS photocatalysts using Na₂S as the S source. Structural, morphological and optical properties of the samples have been investigated by XRD, SEM, EDS, XRF, ICP, N₂ physisorption and UV-vis diffuse reflectance techniques. The Zn_xCd_1-xS solid solution is not a simple compound mixture of ZnS and CdS, its XRD patterns show new structural peaks instead of mixture of original peaks. The lattice parameter a measured from the XRD patterns of the Zn_xCd_1-xS samples exhibits a slightly nonlinear relationship with the Zn mole fraction, which is slightly inconsistent with Vegard's law, thus suggesting that a nonhomogeneous alloy structure exists in Zn_xCd_1-xS solid solution. The photocatalytic H₂ evolution from water splitting in the sacrificial reagents of 0.25 M Na ₂S/0.35 M K₂SO₃ under visible light at 30°C and 55°C were also examined in the study. It is found that Zn _xCd_1-xS solid solution with composition x = 0.4-0.5 shows the highest photocatalytic H₂ production performance. The studied Zn_xCd_1-xS exhibits at least 50 h stable photocatalytic activity under outdoor sunlight irradiation.