Designing Z-scheme In2O3 @ZnIn2S4 core-shell heterojunctions for enhanced photocatalytic multi-pollutant removal

In water bodies, the coexistence of and interaction between multiple pollutants complicate remediation. In this study, the In2O3@ZnIn2S4 Z-scheme heterojunction with a stratified core-shell structure was constructed and used to remove multiple pollutants (tetracycline hydrochloride and Cr(VI)). The large number of active sites and the mechanism of photogenerated charge separation ensured the substantially enhanced catalytic activity of this photocatalyst, making it superior to In2O3 nanospheres and pure ZnIn2S4. The optimised In2O3@ZnIn2S4 nano-flowers (In2O3@ZnIn2S4 NFs) realised 99.8% removal of tetracycline hydrochloride and 100% removal of Cr(VI) within 60 min under visible-light. The material’s high stability was demonstrated by five experiment cycles. Effects of organics, inorganics, and pH about the photocatalytic performance of the optimised In2O3@ZnIn2S4 NFs when tetracycline hydrochloride and Cr(VI) coexist were also explored. Finally, the intermediates and degradation pathways were analysed, and the possible photocatalytic mechanism was also investigated by performing density functional theory calculations. The increasing coexistence of organic and inorganic pollutants in multi-pollutant environments poses significant threats to water biodiversity and human water safety. Most research on photocatalytic pollutant removal has focused on individual pollutants instead of multi-pollutant systems. This is due to the low transfer and high complexation rates of photogenerated charges, making it challenging to simultaneously degrade multiple pollutants. This study constructed a Z-scheme heterojunction semiconductor photocatalyst to effectively remove multi-pollutants (tetracycline hydrochloride and Cr(VI)) and offers critical insights into the potential applications of heterojunction semiconductor photocatalysts in addressing this environmental problem and facilitating effective strategies for remediating multi-pollutant systems.