Dynamic Self-Enhancing Proton Interface of Oxyhydroxides Unlocks Concerted Proton-Coupled Electron Transfer for...

Electrocatalytic nitrate reduction (NO3RR) to ammonia (NH3) offers a sustainable route for simultaneous environmental remediation and resource recovery, yet it is fundamentally impeded by sluggish proton-coupled electron transfer (PCET) due to diffusion-limited proton delivery, thereby severely undermining the Faradaic efficiency and NH3 selectivity. Here, we exploit a cathodically induced alkaline reconstruction strategy to engineer an intrinsic proton-donating CoOOH/NiOOH interface from a bimetallic Co,Ni precursor on copper foam under NO3RR conditions. The reconstructed CoOOH/NiOOH interface, enriched with dense and labile lattice hydroxyls, functions as a localized solid-state proton donor that spontaneously supplies protons through reversible deprotonation. Crucially, this proton-donating behavior is not static but enters a self-enhancing cycle in which nitrate reduction further accelerates the proton dissociation kinetics, creating a positive feedback loop that continuously amplifies the local generation of reactive hydrogen species. Such a unique mechanism achieves rapid and sustained proton delivery, synchronized with electron transfer that is facilitated by the optimized spin state of the metal centers. The resultant concerted PCET streamlines the reaction pathway of the NO3RR to NH3, bypassing unstable intermediates such as *NH2OH and *H2NO, while suppressing the competing hydrogen evolution reaction. Consequently, the CoOOH/NiOOH interface exhibits near-unity ammonia selectivity with a Faradaic efficiency exceeding 98% at high nitrate conversion. We further extend this self-enhancing proton interface to bridge nitrate reduction with poly(lactic acid) depolymerization, directly electrosynthesizing alanine and highlighting the potential for dual waste valorization.