Study on the oxygen catalytic property of CZIF-67/NiCo2O4 composite

Developing an efficient electrocatalyst for the oxygen electrode is a significant challenge in the field. In this study, Co–N co-doped carbon (denoted as CZIF-67) is used as modifier to enhance the catalytic activity of the spinel oxide NiCo2O4. Among all the catalysts synthesized, the composite catalyst containing 10% CZIF-67 (where CZIF-67 constitutes 10% of the total mass) exhibits the highest catalytic activity for both the oxygen evolution reaction and the oxygen reduction reaction. This is evidenced by the largest current densities of 275.6 mA·cm−2 and 235.6 mA·cm−2 at the cutoff voltage of 1.9268 V (vs. RHE) and 0.3268V (vs. RHE). XPS characterization showed the surface element composition and valence analysis of 10% CZIF-67, which revealed the synergistic reaction between CZIF-67 and NiCo2O4 to a certain extent. Electrochemical impedance spectroscopy (EIS) results indicate that the charge transfer resistance of 10% CZIF-67 catalyst is the lowest, suggesting a faster charge transfer rate. It can be attributed to the synergistic effects between appropriate amount of CZIF-67 and the spinel oxide NiCo2O4. Additionally, the large specific surface and the porous structure of CZIF-67 can provide more active sites for the reactions.