Innovative Air Cathode with Ni-Doped Cobalt Sulfide in Highly Ordered Macroporous Carbon Matrix for Rechargeable Zn-Air Battery.

To realize the practical application of rechargeable Zn-Air batteries (ZABs), it is imperative to develop a non-noble metal-based electrocatalyst with high electrochemical performance for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, Ni-doped CoS nanoparticles dispersed on an inverse opal-structured N, S co-doped carbon matrix (IO─NiCoS@NSC) as a bifunctional electrocatalyst is presented. The unique 3D porous structure, arranged in an inverse opal pattern, provides a large active surface area. Also, the conductive carbon substrate ensures the homogeneous dispersion of NiCoS nanocrystals, preventing aggregation and increasing the exposure of active sites. The introduction of heteroatom dopants into the CoS structure generates defect sites and enhances surface polarity, thereby improving electrocatalytic performance in alkaline solutions. Consequently, the IO─NiCoS@NSC shows excellent bifunctional activity with a high half-wave potential of 0.926 V for ORR and a low overpotential of 289 mV at 10 mA cm for OER. Moreover, the rechargeable ZAB assembled with prepared electrocatalyst exhibits a higher specific capacity (768 mAh g ), peak power density (180.2 mW cm), and outstanding stability (over 160 h) compared to precious metal-based electrocatalyst.