Dual S-scheme-based ternary BiOCl/CuInS₂/WO₃ heterojunction for Victoria blue photodegradation

Photocatalysis has great potential for transforming sustainable solar energy into chemical energy, offering significant benefits for environmental applications. However, the rapid charge carrier recombination in pristine semiconductors is a big challenge. S-scheme heterojunction strategy is one of the effective strategies to overcome this challenge. The present work explored the photodegradation ability of the BiOCl-CuInS₂-WO₃ heterojunction against Victoria blue (VIB) dye. The pristine photocatalysts (i.e. BiOCl, CuInS₂, WO₃) were fabricated hydrothermally, however the BiOCl-CuInS₂-WO₃ ternary photocatalyst was constructed via a facile physical mixing. The BiOCl-CuInS₂-WO₃ ternary photocatalyst followed dual S-scheme charge migration route as per the band alignments which lead to upgraded photodegradation ability in comparison to other pristine photocatalysts. The S-Scheme heterojunction formation offered enhanced charge separation and the separated charge carriers carry out degradation process in presence of light. The photodegradation rate of BiOCl-CuInS₂-WO₃ dual S-scheme heterojunction was 99.24 % after 90 min, that was superior than other photocatalysts. Similarly, via ESR studies and scavenging experiments, the significant role of ^[rad]O₂⁻, and ^[rad]OH radicals was determined in the degradation of VIB. Also, the S-scheme heterojunction resulted in extended light absorption ability with reduced recombination rate (verified by PL analysis) and higher separation rate of photocarriers (confirmed by EIS and TPR analysis) in ternary heterojunction. This resulted in improved photodegradation effectiveness of the ternary BiOCl-CuInS₂-WO₃ photocatalyst. The stability of the formed heterojunction was verified via reusability tests which displayed 90.25 % degradation efficiency after 5 successive catalytic cycles.