Lewis acidic regulators boost efficient nitrate-to-ammonia electrosynthesis on low-cost copper nanohybrids

Electrochemical nitrate-to-ammonia reduction reaction represents a one-stonetwo-bird strategy for environmental toxin removal and sustainable fertilizer production. However, conventional catalysts, including alloys, nanoparticles, and heterojunctions, often suffer from compromised activity, selectivity, and stability due to insufficient atomic-level control over the active-site architectures. To address these challenges, we introduce the Lewis acid-base concept into the rational design of the electrocatalyst, enabling precise modulation of molecular interactions and charge redistributions between reaction species and catalytic centers. Here, we synthesize a series of transition metal-triazole nanohybrids, among which the version featuring Cu exhibits outstanding selectivity and activity (ammonia Faradaic efficiency of 98.9% and ammonia yield rate of 1.78 mmol h⁻¹ mgcat⁻¹). Notably, upon scaling up in a practical flow electrolyzer, the Cu nanohybrid achieves >99% nitrate-to-ammonia conversion within 4 hours using authentic agricultural wastewater, with the upcycled water achieving WHO drinkable standards. Combined DFT computational and synchrotron X-ray absorption spectroscopic analyses reveal that tailoring the Lewis acid-base characteristics of the Cu nanohybrid optimizes nitrate adsorption at the active site and simultaneously suppresses competing hydrogen evolution. This work establishes a paradigm-shifting catalyst design that focuses on electronic structure modulation with implications in advancing wastewater treatment, resource recovery, and sustainable synthesis technologies.