Disentangling the Role of Local Composition and Electronic Structure in NO3RR Performance of NiFe Alloys

Elemental first row transition metal electrocatalysts typically exhibit a tradeoff between NO3RR Faradaic efficiency (FE) and NH4+ selectivity. Here, we find that NiFe alloys have high NO3RR FE and substantially higher NH₄⁺ selectivity than Ni or Fe. Calculations show that NO3* adsorption is promoted by Fe-rich surfaces, and its competitive adsorption with H* rationalizes trends in reaction rate order. Activation energies of subsequent reduction steps illustrate NO2* deoxygenation is promoted by Ni-rich surfaces, whereas NO* dissociation is promoted by both surface and subsurface Fe atoms. These findings suggest that NiFe alloys achieve enhanced selectivity by leveraging local site diversity.