ZnS/Cd_(1-x)Zn_xS 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

摘要

The ZnS/Cd_(1-x)Zn_xS composite photocatalyst was successfully synthesized using a hydro-thermal solvent by adding excess hydroxide ions. The ZnS/Cd_(1-x)Zn_xS 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 Cd_(1-x)Zn_xS solid solution contained a certain amount of ZnS. A certain amount of ZnS was also contained in the synthesized Cd_(1-x)Zn_xS 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/Cd_(1-x)Zn_xS composite photocatalyst was not the hetero-junction formed between ZnS and Cd_(1-x)Zn_xS but rather the stacking fault structures in the Cd_(1-x)Zn_xS solid solution. However, more stacking fault structures could be formed in the Cd_(1-x)Zn_xS solid solution due to the presence of ZnS.