Ultrathin NiCo2O4/g-C3N4 Z-scheme heterojunction for visible-light-driven persulfate activation toward rapid and low-toxicity phenol degradation

Abstract

Efficient removal of phenolic compounds from industrial wastewater remains a significant challenge in water treatment. While persulfate-based advanced oxidation processes have garnered attention due to their strong oxidation capability, their application is constrained by activation efficiency. In this work, a visible-light-responsive Z-scheme CN/NiCo heterojunction photocatalyst was successfully constructed by integrating ultrathin NiCo2O4 (NiCo) nanosheets with g-C3N4(CN) for activating persulfate to efficiently degrade phenol. Under visible light irradiation, 0.1CN/NiCo achieved a phenol removal rate of 97.1% within 30 min, significantly outperforming its individual components. The CN/NiCo heterojunction structure effectively promotes the separation and migration of photogenerated electron–hole pairs, following a Z-scheme charge transfer pathway. The Ni3+/Ni2+ and Co3+/Co2+ redox couples synergistically activated persulfate, with superoxide radicals (O2·-), singlet oxygen (1O2), and holes (h+) identified as the dominant reactive species. Moreover, the catalyst maintained high activity over five consecutive cycles, demonstrating excellent stability. This study provides new insights for designing efficient and stable persulfate-based photocatalytic systems for the treatment of refractory organic pollutants.