Efficient and stable photocatalytic hydrogen production from water splitting over ZnxCd1-xS solid solutions under visible light irradiation

A simple co-precipitation method was employed to synthesize a series of cubic zinc-blende phase of ZnxCd1−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 ZnxCd1−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 ZnxCd1−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 ZnxCd1−xS solid solution. The photocatalytic H2 evolution from water splitting in the sacrificial reagents of 0.25 M Na2S/0.35 M K2SO3 under visible light at 30 °C and 55 °C were also examined in the study. It is found that ZnxCd1−xS solid solution with composition x = 0.4-0.5 shows the highest photocatalytic H2 production performance. The studied ZnxCd1−xS exhibits at least 50 h stable photocatalytic activity under outdoor sunlight irradiation.