Synchronizing Proton-Electron Transfer in Nanoconfined Cu-Ni Alloys Enables Highly Selective Nitrate-to-Ammonia Conversion

Abstract

coupled catalytic sites, enabling efficient pathway regulation in nitrate reduction. Within mesoporous carbon nanofibers, Cu sites preferentially stabilize NOx intermediates and promote N-O bond activation, while adjacent Ni sites facilitate in situ active hydrogen generation. The alloy interface establishes cooperative adsorption–hydrogenation units that align intermediate binding with hydrogenation kinetics, thereby lowering the energetic barriers of sequential deoxygenation steps and suppressing competing Electrochemical nitrate reduction to ammonia involves a complex eight-electron proton-coupled electron transfer (PCET) cascade, in which asynchronous electron-proton delivery and kinetically decoupled adsorption-hydrogenation steps lead to sluggish deoxygenation and limited selectivity. Here we design a nanoconfined Cu-Ni alloy catalyst that synchronizes proton-electron transfer at spatially hydrogen evolution. The optimized Cu2Ni catalyst delivers an ammonia production rate of 8.7 mg cm-2 h-1 with a Faradaic efficiency of 96% at -0.5 V versus RHE. Mechanistic analyses reveal that nanoconfinement further modulates local proton availability and reaction kinetics, reinforcing PCET synchronization across the cascade. Coupling nitrate conversion with a Zn-NO3- battery demonstrates a pollution-to-energy strategy, highlighting reaction-pathway engineering as a viable approach toward sustainable nitrogen cycle management.