Carbon Nanotube-Loaded NiCo₂O₄ Nanoparticles Boosting Oxygen Electrocatalysis in Zinc–Air Batteries

Metal–air batteries, with high energy density and eco-friendliness, are crucial for sustainable energy. Although abundant and low-cost, spinel oxides, ideal for metal–air batteries, suffer from low conductivity, hindering electron transport and slowing electrocatalytic kinetics. In this work, NiCo2O4 (NCO) was embedded on carbon nanotubes (CNTs) via a hydrothermal method to form a composite catalyst (NCO-1CNTs), and subsequent annealing in nitrogen enhanced oxygen vacancy concentration in the spinel structure. In 0.1 M KOH, NCO-1CNTs achieves outstanding oxygen evolution reaction (OER) performance (η10 = 427 mV) and oxygen reduction reaction (ORR) performance (jL = 5.1 mA cm–2), surpassing NCO by 16.6% and 82.1%. The enhanced catalytic activity is attributed to the high conductivity of carbon nanotubes, which accelerates electron transfer. Additionally, carbon nanotubes prevent spinel oxide aggregation, increase active sites, and form a porous structure, enhancing oxygen species transport. Moreover, annealing NCO-1CNTs in a nitrogen atmosphere induces the spinel component to generate more oxygen vacancies, boosting catalytic performance. The resulting zinc–air battery delivers a power density of 68 mW cm–2 and exhibits stable performance over 100 h of charge–discharge cycling. This study delivers a low-cost, high-activity, stable bifunctional cathode catalyst, signaling great promise for commercial rechargeable zinc–air batteries.