Preparation of Co3O4/NiCo2O4@NC double-shelled catalyst and its high performance for degradation of levodopa in Electro-Fenton system

Based on the pyrolysis of zeolitic imidazolate framework-67/Ni-Co layered double hydroxide (ZIF-67/Ni-Co LDH) precursor, we successfully prepare a novel Co3O4/NiCo2O4@NC double-shelled hollow structure catalyst. After carbonization, Co3O4/NiCo2O4@NC inherit the polyhedral shape from ZIF-67/Ni-Co LDH. At the same time, obvious inter-shell pores appear between the inner shell and outer shell of Co3O4/NiCo2O4@NC. Compared with simple single-shell Co3O4@NC catalyst, more complex hollow structure brings better electrochemical performance of the material. Co3O4/NiCo2O4@NC modified graphite felt (GF) electrode is used to degrade levodopa in Electro-Fenton (EF) system. According to the experimental results, the removal rate of levodopa and TOC have reached 99.07% and 60.16%, respectively after 2 h reaction. The EF reaction for the degradation of levodopa follows a pseudo first-order kinetic model. Based on the intermediate product, we propose a possible degradation pathway of levodopa. In addition, we have evaluated the reusability of Co3O4/NiCo2O4@NC-GF electrode in EF reaction. Finally, we believe that the Co3O4/NiCo2O4@NC-GF electrode is a promising cathode for the treatment of pharmaceutical wastewater in EF field.