ZnS/Cd1-xZnxS composite photocatalyst synthesized with excessive strong alkali solution as a hydrothermal solvent: The chemical equilibrium theory of the synthesis process and its influence on photocatalytic performance

The ZnS/Cd1-xZnxS composite photocatalyst was successfully synthesized using a hydrothermal solvent by adding excess hydroxide ions. The ZnS/Cd1-xZnxS composite photocatalyst showed excellent photocatalytic activity for hydrogen production with a hydrogen evolution rate of 21.8 mmol/g−1 h−1, which is the highest photocatalytic activity reported to date among visible-light-driven photocatalysts without loading cocatalysts. According to the theoretical calculation and analysis of the chemical equilibrium in the synthesis process, the synthesized Cd1-xZnxS solid solution contained a certain amount of ZnS. A certain amount of ZnS was also contained in the synthesized Cd1-xZnxS solid solution based on experimental results, thus demonstrating the validity of the theoretical calculation. Experimental results showed that the key factor affecting the photocatalytic activity of hydrogen production for the ZnS/Cd1-xZnxS composite photocatalyst was not the heterojunction formed between ZnS and Cd1-xZnxS but rather the stacking fault structures in the Cd1-xZnxS solid solution. However, more stacking fault structures could be formed in the Cd1-xZnxS solid solution due to the presence of ZnS.