Photocatalytic Reduction of Cr(VI) and Degradation of Organic Pollutants by Z-Scheme g-C3N4/Bi2S3 Heterojunction

Abstract

Photocatalytic reduction of hexavalent Cr(VI) couping oxidative degradation of organic contamination is an emerging and practical approach for water treatment. In this study, Z-scheme g-C3N4/Bi2S3 heterojunctions with intimate interface were successfully synthesized by direct growth of Bi2S3 on g-C3N4 surface. Notably, the photocatalytic performance of Z-scheme g-C3N4/Bi2S3 was influenced by g-C3N4 content. The optimized 2% g-C3N4/Bi2S3 heterojunction shows the highest photocatalytic reduction performance with 93.4% reduction efficiency of Cr(VI) under UV-visible light due to efficient separation and transfer of charge carriers and proper band structure. Furthermore, 2% g-C3N4/Bi2S3 can degrade tetracycline and Rhodamine B. Free radical capturing and quantitative tests indicate that holes and superoxide radicals are primary active species for the degradation of organic pollutants, while Cr(VI) was reduced to Cr(III) by the photogenerated electrons. Overall, this study provides new insight into the synthesis of high-performance Z-scheme heterojunctions for the future advancement of photocatalysis technology.