ZnCo₂O₄/NC Hollow Polyhedra for Bisphenol A Disposal and the Oxygen Evolution Reaction

Zinc–cobalt oxide/nitrogen-doped carbon (ZnCo2O4/NC) hollow polyhedra (HP) were synthesized by mediating zinc and cobalt bimetallic zeolitic imidazolate frameworks (ZIF-8–ZIF-67). The coexistence of Co3+/Co2+ and a significantly increased amount of oxygen vacancies were found in ZnCo2O4/NC HP compared with Co3O4/NC HP. As a bifunctional catalyst, on the one hand, ZnCo2O4/NC HP displayed more than 15- and 5-fold higher apparent reaction rates for bisphenol A (BPA) degradation with persulfate compared to Co3O4/NC and Co3O4–ZnCo2O4/NC HP, respectively. A desirable reusability of ZnCo2O4/NC HP for BPA degradation was achieved, and further study suggested that the main active species for BPA elimination were the superoxide anion and single oxygen. On the other hand, ZnCo2O4/NC HP could be a potential catalyst for the oxygen evolution reaction (OER), which was evidenced by a 20 mV lower potential in comparison with Co3O4/NC at 10 mA·cm–2 as well as the good stability. The advantages of ZnCo2O4/NC HP in BPA degradation and OER could be ascribed to the small size of particles, hollow structure with high specific surface area, and rich oxygen vacancies.