Interfacial Electronic Regulation in N-Doped Carbon-Encapsulated NiCo Alloy Enables High-Current Nitrate-to-Ammonia Electrosynthesis

Abstract Electrochemical nitrate reduction (NO 3 − RR) offers a route to couple wastewater remediation with green ammonia (NH 3 ) synthesis, but remains kinetically and mechanistically challenging under high-current-density operation. Herein, an N-doped carbon-encapsulated NiCo alloy catalyst (NiCo@NC) is derived from a NiCo-ZB precursor supported on conductive carbon black. The cathodic NO 3 − RR over NiCo@NC achieves an NH 3 yield rate of 187 mol h −1 g cat −1 with 95% Faradaic efficiency (FE) at −0.6 V RHE in an H-type cell and sustains ~92% FE at 2.0 A cm −2 under a cell voltage of 3.3 V in a membrane–electrode assembly. Pairing this cathodic NO 3 − RR with anodic methanol oxidation to formate enables simultaneous NH 3 and formate production at 2.1 A cm −2 under a cell voltage of 2.8 V, while maintaining NH 3 and formate FEs above 90% and 96%, respectively. In situ Fourier transform infrared and operando X-ray absorption fine structure spectra reveal preferential *NO stabilization and reversible Co valence/coordination, while theoretical calculations disclose interfacial charge polarization between NiCo alloy core and N-doped carbon shell, fabricating dual sites, comprising electron-deficient graphitic carbon and electron-rich pyridinic-N domains, that accelerate water dissociation/proton supply and lower the barrier of the rate-determining *NO → *NOH step. These insights establish alloy@NC interface regulation as a general strategy for high-rate NO 3 − RR.