Polarized Metal Nitride Solid Solutions as Electrocatalysts Enabling Ampere-Level Selective Formic Acid Synthesis.

Formic acid (FA) is an important value-added product in biomass electrooxidation and an effective liquid fuel and hydrogen carrier. However, achieving its efficient industrial-scale synthesis with durable hydrogen evolution remains challenging. Here, we report a single-phase NiCoN solid-solution metal nitride catalyst, in which atomic-level Co incorporation induces symmetry-breaking Ni-N-Co coordination environments with electronically polarized active sites. This structural modulation drives the interfacial transformation into metal oxy(hydro)xide species and optimizes the adsorption energies of relevant intermediates. These changes accelerate dehydrogenation kinetics and lower the energy barrier for C-C bond cleavage, thereby directing the reaction pathway toward selective stepwise oxidation to FA. The optimal NiCoN catalyst achieves a FA Faradaic efficiency of 97.2% and sustains over 3,600 h of operation at 1 A cm-2 in an anion-exchange membrane (AEM) electrolyzer, representing one of the longest reported lifetimes for a glycerol-assisted coupled system. This work establishes atomic-scale solid-solution engineering as an effective approach to regulate catalytic pathways and long-term interfacial stability for biomass electrochemical conversion.