Architecting an indirect Z-scheme NiCo2O4@CdS–Ag photocatalytic system with enhanced charge transfer for high-efficiency degradation of emerging pollutants

Bimetallic oxides with spinel structure show great prospects in the photocatalysis owing to many active sites. Herein, a novel 500NiCo2O4@CdS–5%Ag composite was fabricated via a feasible strategy. Interestingly, the combination with NiCo2O4 could significantly enhance the absorption ability of CdS for visible light. Benefiting from the formation of heterojunction structure between NiCo2O4 and CdS, the recombination of photogenerated electrons and holes was remarkably restrained. As an effective mediator, deposition of Ag could further promote the transfer of photogenerated charge carriers, thereby accelerating the reaction rate. Meanwhile, light absorption capacity of composite was also improved, owing to the surface plasmon resonance effect of metallic Ag. More importantly, 500NiCo2O4@CdS–5%Ag composite with great stability displayed an excellent performance in the photocatalytic degradation of OFX, and its highest removal efficiency was as high as 99.14%. Possible degradation pathways of OFX were given, and most of OFX could be degraded into CO2, H2O and other by-products with no toxicity. Significantly, the separation and transfer of photogenerated charge carriers followed indirect Z-scheme heterojunction mechanism. The O2−, OH and 1O2 were main active species in photocatalytic reaction system. All in all, current work inspired some new ideas for designing novel photocatalytic system in wastewater treatment. •Indirect Z-scheme heterojunction was prepared for inhibiting recombination of carrier.•Surface plasmon resonance effect of metallic Ag boosted the light absorption ability.•Deposition of Ag could accelerate the transfer of photogenerated charge carriers.•Newly-constructed hybrid had good photocatalytic performance in ofloxacin degradation.•A credible mechanism about enhanced photocatalytic activity was proposed.