Heteroatom-doped carbon attached to ultra-fine Fe-NiCoP as high-performance oxygen electrocatalyst for Zn-air batteries

The construction of efficient and durable electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) remains a challenge for rechargeable Zn-air batteries (ZABs). Bimetallic phosphide (NiCoP) holds considerable promise as a bifunctional catalyst. Here, an efficient NiCoP-based bifunctional electrocatalyst was fabricated using PCN-222-assembled organophosphorus complexes, specifically 1,1-bis(diphenylphosphine)ferrocene (DPPF). These DPPF complexes serve as sources of phosphorus and metals, undergoing in-situ conversion into Fe-doped NiCoP nanoparticles (Fe-NiCoP) while simultaneously constructing a heteroatom-doped carbon matrix (NPC). The final catalytic structure, composed of ultra-fine Fe-NiCoP nanoparticles confined within the NPC, exhibits superior bifunctional electrocatalytic activity (with a ΔEgap of 0.69 V between OER and ORR) and exceptional stability. In-situ Raman spectroscopy and DFT calculations reveal that the high performance arises from the synergistic effect of Fe-NiCoP and NPC, where Fe-NiCoP triggers the catalytic activity of the attached NPC. The calculated active site is identified as the C atom near the N atom on the NPC, lowering the potential barrier for O-containing intermediate compounds and enhancing the catalytic performance. In addition, NPC protects the Fe-NiCoP core from oxidation during battery cycles, allowing ZABs equipped with this catalyst to achieve high power density and long-term cycling performance.