Interface charge separation in Cu2CoSnS4/ZnIn2S4 heterojunction for boosting photocatalytic hydrogen production

The practical application of hexagonal ZnIn 2 S 4 (ZIS) as a visible-light photocatalyst for hydrogen (H 2 ) production is hindered by rapid internal charge recombination. In this study, we successfully synthesized Cu 2 CoSnS 4 (CCTS) nanocrystals and loaded them onto the surface of ZIS nanosheets to create a p-n heterojunction photocatalyst. The optimized Cu 2 CoSnS 4 /ZnIn 2 S 4 (CCTS/ZIS) heterojunction exhibited a significantly higher visible-light photocatalytic H 2 evolution rate of 4.90 mmol·g −1 ·h −1 compared to ZIS and CCTS alone. The enhanced photocatalytic efficiency was attributed to improved electron transfer and charge separation at the heterojunction interface. The formation of p-n heterojunction facilitated the accumulation of valence band electrons in ZIS and conduction band holes in CCTS, effectively suppressing the recombination of photogenerated electrons and holes. Theoretical calculations, spectroscopic, and photoelectrochemical characterizations supported the findings. This work presents a promising approach for designing efficient p-n heterojunction semiconductor photocatalysts for practical applications in visible-light-driven hydrogen evolution.