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

Zinc–cobalt oxide/nitrogen-doped carbon (ZnCo 2 O 4 /NC) hollow polyhedra (HP) were synthesized by mediating zinc and cobalt bimetallic zeolitic imidazolate frameworks (ZIF-8–ZIF-67). The coexistence of Co 3+ /Co 2+ and a significantly increased amount of oxygen vacancies were found in ZnCo 2 O 4 /NC HP compared with Co 3 O 4 /NC HP. As a bifunctional catalyst, on the one hand, ZnCo 2 O 4 /NC HP displayed more than 15- and 5-fold higher apparent reaction rates for bisphenol A (BPA) degradation with persulfate compared to Co 3 O 4 /NC and Co 3 O 4 –ZnCo 2 O 4 /NC HP, respectively. A desirable reusability of ZnCo 2 O 4 /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, ZnCo 2 O 4 /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 Co 3 O 4 /NC at 10 mA·cm –2 as well as the good stability. The advantages of ZnCo 2 O 4 /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.