Bifunctional mesoporous CoO/nitrogen-incorporated graphene electrocatalysts for high-power and long-term stability of rechargeable zinc-air batteries

Despite high energy density, low-cost, and ecofriendly, rechargeable Zinc-air batteries (ZABs) suffer from sluggish kinetics stability during oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the cathode. Herein, we demonstrate CoO nanoparticles anchored on N-doped reduced graphene oxide (CoO/N-rGO) with an excellent bifunctional catalytic activity and stability and facile redox kinetics of ORR and OER for high-performance rechargeable ZABs. The CoO/N-rGO catalysts are featured with the abundant active sites, a large accessible area, and high electrochemical conductivity, which are associated with increased oxygen vacancy surface, reduced valence, and mesoporous architecture. The half-wave potential (E_1/2) and electron transfer number for ORR are 0.79 V and 3.72 at 0.40 V (vs RHE), respectively, while OER potential at 10 mA cm⁻² (E_{j = 10}) is 1.61 V (vs RHE). Remarkably, the ZAB cell with CoO/N-rGO achieves high specific capacity of 545 mAh g_zn⁻¹, power density of 41 mW cm⁻², and cyclic stabilities with high energy efficiency of 64.44% at 2 mA cm⁻². In addition, postmortem analysis validates that the oxidation and aggregation of CoO/N-rGO catalyst is mitigated while the inactivation of Zn anode is inhibited.