Internal electric field driving separation and migration of charge carriers via Z-scheme path in AgIn5S8/ZnO heterojunction for efficient decontamination of pharmaceutical pollutants

Z-scheme heterojunctions are considered as prospective photocatalysts for elimination of organic pollutants. However, the origin of enhanced oxidation ability of Z-scheme heterojunctions is not well understood, and the working mechanism based on internal electrical field is still ambiguous. Here, we report Z-scheme AgIn5S8/ZnO heterojunction with superior photocatalytic activity in degrading pharmaceutical pollutants and enhancing biodegradability of pharmaceutical wastewater. The average oxidation state (AOS) and carbon oxidation state (COS) of pharmaceutical wastewater are significantly increased from 0.42 to 1.35 and 2.94 after photocatalytic treatment of AgIn5S8/ZnO. The analysis on the origin of superior photocatalytic activity reveals that the internal electric field in AgIn5S8/ZnO heterojunction works as a driving force to facilitate efficient separation of photogenerated charge carriers via Z-scheme path, thus generating spatially separated holes and electrons with high redox ability and realizing effective elimination of pharmaceutical pollutants. This study provides deep insight into photocatalytic mechanism of Z-scheme heterojunction for efficacious elimination of organic pollutants and boosted biodegradability of pharmaceutical wastewater.