Dual S-scheme heterojunction g-C3N4/Bi2S3/CuS composite with enhanced photocatalytic activity for methyl orange degradation

Weak redox potential and high recombination of charge carriers are two main factors that limit the efficiency of photocatalysts in wastewater treatment. In this study, the synthesis of heterostructure photocatalyst (composed of graphitic carbon nitride, bismuth sulphide, and copper sulphide (g-C3N4/Bi2S3/CuS)) with improved charge carrier separation and tuned redox potential for improved photocatalysis of methyl orange (MO) dye is reported. The band alignment of the synthesized heterostructure exhibited a synergistic effect, significantly enhancing charge carrier separation and mitigating their recombination. The g-C3N4/Bi2S3/CuS composite exhibited enhanced photocatalytic efficiency compared to the pristine g-C3N4, Bi2S3, and CuS. Furthermore, the activity of the heterostructure was observed to increase as the ratio of CuS in the photocatalyst was increased. The highest photocatalytic efficiency was recorded for the g-C3N4/Bi2S3/CuS(20%), which achieved 98% degradation efficiency and reaction rate constant (k) of 8.08 x 10(-2) min(-1). Radical scavenging experiments showed that (OH)-O-center dot, e(-), and h(+) played significant roles in the degradation process. A charge transfer scheme and mechanism of reaction were proposed on this basis.