Synergistic Co₂N nanoparticles and N-doped porous ginger-derived carbon as an efficient bifunctional oxygen...

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 (Co_xN) 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 Co_xN/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.