Synergistic Co2N nanoparticles and N-doped porous ginger-derived carbon as an efficient bifunctional oxygen electrocatalyst for Zn-air battery.

The development of efficient and cost-effective bifunctional electrocatalysts for oxygen reduction and evolution reactions (ORR/OER) is essential for rechargeable metal-air batteries and reversible fuel cells, yet remains challenging. Cobalt nitrides (CoxN) coupled with nitrogen-doped carbon have shown promise as bifunctional catalysts, but achieving high performance for both reactions via sustainable synthesis remains difficult. Herein, we report a Co2N nanoparticles-embedded N-doped porous biomass-derived carbon catalyst (denoted as Co/NGGC) that addresses this challenge, exhibiting markedly enhanced bifunctional activity compared to previously reported CoxN/N‑carbon systems. The optimized Co/NGGC achieves a low potential gap (ΔE) of 0.65 V between the ORR and OER. For the ORR, the resulting catalyst demonstrates superior activity, excellent durability and robust methanol tolerance, compared with the commercial Pt/C (20 wt% Pt). For the OER, Co/NGGC can drive current density of 10 mA·cm-2 at an ultralow overpotential of 250 mV, significantly outperforming RuO2. More importantly, the alkaline zinc-air battery (ZAB), assembled with Co/NGGC as the cathode, demonstrates high peak power density and excellent stability, underscoring its practical applicability. The enhanced electrocatalytic performance is attributed to the strong coupling between the Co2N nanoparticles and the nitrogen-doped carbon framework, which creates a synergistic microenvironment that accelerates electron transfer and facilitates mass diffusion. Density functional theory (DFT) calculations further reveal that the electronic states of Co2N near the Fermi level are significantly elevated within the N-doped carbon matrix, optimizing the adsorption/desorption behavior of key reaction intermediates and thereby accelerating the overall reaction kinetics. This work not only presents a sustainable strategy for converting biomass into efficient electrocatalytic materials but also provides valuable insights into the design of advanced oxygen electrodes for next-generation energy conversion and storage devices.