Carbon-confined FeNi alloy nanoparticles with minor Fe3C domains derived from enzymatic lignin for oxygen reduction and zinc–air batteries

Enzymatic lignin enables confined FeNi alloys and M–N x sites in porous carbon. • A 1.5:1 Fe/Ni ratio drives dual-level electronic regulation for ORR. • The FeNi@ELNC-1.5 composite exhibits an outstanding ORR half-wave potential of 0.903 V, rivaling commercial Pt/C. • DFT links FeNi–carbon coupling to optimized oxygen-intermediate adsorption. • Zn–air batteries reach 1.520 V OCV, 772.93 mAh g −1 specific capacity and 154 h cycling. Slow oxygen electroreduction at the air electrode and the associated dependence on Pt catalysts continue to restrict the deployment of zinc-air batteries (ZABs). This study examines whether enzymatic hydrolysis lignin can serve as a renewable carbon precursor for constructing an efficient FeNi-based ORR catalyst. FeNi@ELNC-X catalysts were synthesized by solvothermal treatment followed by pyrolysis and evaluated through physicochemical characterization, rotating-electrode electrochemistry, ZAB tests, and density functional theory (DFT) calculations. At an optimized Fe/Ni precursor molar ratio of 1.5:1, the lignin-derived N-doped porous carbon framework confines FeNi alloy nanoparticles and minor Fe 3 C domains, limiting particle aggregation and creating coupled metal-carbon interfaces. In 0.1 M KOH, FeNi@ELNC-1.5 reached E 1/2  = 0.903 V vs. RHE, approaching the response of 20% Pt/C; it also favored a four-electron route and preserved 98.9% of the current over 36,000 s. The calculations indicate that interfacial electronic interactions adjust the binding of *OOH, *O, and *OH. When implemented as the air electrode, the catalyst enabled a ZAB delivering 1.520 V OCV together with a capacity of 772.93 mAh g −1 at a discharge current of 5 mA cm −2 . These findings provide a renewable route to non-precious-metal air-cathode catalysts. Download: Download high-res image (284KB) Download: Download full-size image