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

Abstract 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.