A Wetting and Capture Strategy Overcoming Electrostatic Repulsion for Electroreduction of Nitrate to Ammonia from Low‐Concentration Sewage

Abstract

Ammonia production by electrocatalytic nitrate reduction reaction (NO₃RR) in water streams is anticipated as a zero-carbon route. Limited by dilute nitrate in natural sewage and the electrostatic repulsion between NO₃ ^- and cathode, NO₃RR can hardly be achieved energy-efficiently. The hydrophilic Cu@CuCoO₂ nano-island dispersed on support can enrich NO₃ ^- and produce a sensitive current response, followed by electrosynthesis of ammonia through atomic hydrogen (*H) is reported. The accumulated NO₃ ^- can be partially converted to NO₂ ^- without external electric field input, confirming that the Cu@CuCoO₂ nano-island can strongly bind NO₃ ^- and then trigger the reduction via dynamic evolution between Cu-Co redox sites. Through the identification of intermediates and theoretical computation. it is found that the N-side hydrogenation of *NO is the optimal reaction step, and the formation of N─N dimer may be prevented. An NH₃ product selectivity of 93.5%, a nitrate conversion of 96.1%, and an energy consumption of 0.079 kWh g_NH3 ^-1 is obtained in 48.9 mg-N L^-1 naturally nitrate-polluted streams, which outperforms many works using such dilute nitrate influent. Conclusively, the electrocatalytic system provides a platform to guarantee the self-sufficiency of dispersed ammonia production in agricultural regions.