Electrodeposition of bimetal Ni-Co oxide as a bifunctional electrocatalyst for rechargeable zinc air battery

Zinc air battery is a promising candidate green energy storage due to its high energy density and low-cost. However, most of the preparation of air cathode in the literature involves a lengthy and inefficient process of mixing catalyst powders with a polymeric binder. Herein, we synthesize bimetal Ni-Co oxide through a simple electrodeposition technique followed by annealing at a low temperature under atmospheric conditions. The addition of cobalt at various contents significantly alters surface morphology from tiny nanoparticles to a 2D nano-sheet structure. The performance of the as-prepared catalysts were firstly evaluated toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in alkaline solution. Our results show that the incorporating cobalt in the NiO host structure not only improve the OER but also the ORR activities. The required potential to drive OER at a current density of 10 mA/cm2 and the half-wave potential for ORR using the NC-2 catalyst are 1.567 and 0.855 V vs. RHE, respectively, resulting a delta potential of 0.712 V. Furthermore, we demonstrate the practical application of the NC-2 catalyst as the air cathode electrode for assembling a liquid zinc air battery device. The battery test reveals that NC-2 has an open circuit potential of 1.36 V and a specific capacity of 714 mAh/gZn with an excellent stability performance for about 80 h. Our findings suggest that bimetal Ni-Co oxide is a promising catalyst for enhancing the performance of zinc air batteries.