Matching and adjusting energy band structures of Pd-modified sulphides (ZnS, In2S3 and CuS) and improving the photocatalytic activity of CO2 photoreduction

A series of Pd-modified sulphide photocatalysts (ZnS-PdX%, In2S3-PdX% and CuS-PdX%) for the photoreduction of CO2 were synthesised via a simple hydrothermal method. Here, the introduction of the -S-Pd-S- surface species onto the surface of the sulphides extended the visible light absorption, prolonged the lifetime of photogenerated electrons and suppressed the recombination of the photocarriers. Additionally, the match between the band structure and the redox potential for the photoreduction of CO2 was improved. As a result, the photocatalytic activity of ZnS-Pd1.5%, In2S3-Pd1.5% and CuS-Pd1.5% was enhanced when compared with the results from ZnS, In2S3 and CuS photocatalysts. Also, ZnS-Pd1.5%, In2S3-Pd1.5% and CuS-Pd1.5% showed different photocatalytic activities due to differences in the matching relationships between the band structure and the redox potential. In this paper, extensive details on adjusting and matching the energy band structures, as well as viable methods for improving photocatalytic performance, are provided.