NiCu bifunctional electrocatalysts enable coupled anodic–cathodic nitrogen elimination with exceptional Faradaic efficiency

Electrochemical elimination of nitrogenous pollutants offers a sustainable solution to water eutrophication but is often limited by low efficiency when anodic and cathodic reactions are conducted separately. Herein, we report a coupled electrochemical system integrating ammonia oxidation reaction (AOR) and nitrate reduction reaction (NIRR) using bimetallic NiCu nanoalloy catalysts. Optimized Ni₅Cu₅ and Ni₂Cu₈ nanoparticles served as the anodic and cathodic catalysts, respectively, exhibiting high activity (174.7 mA·cm⁻²@1.5 V for AOR and 84.1 mA·cm⁻²@0 V for NIRR) and stability. A coupled full-cell electrolyzer demonstrated good stability and achieved a total nitrogen removal equivalent Faradaic efficiency of 157%. In situ characterizations confirmed N₂ as one of the primary products for both AOR and NIRR, along with the other nitrogenous species. These nitrogenous byproducts could be eliminated through a chemical reaction pathway, further improving the nitrogenous elimination efficiency. This work presents an efficient, noble-metal-free strategy for integrated nitrogen waste conversion, offering promising prospects for scalable wastewater treatment applications.