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

Abstract

AbstractAmmonia 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 gNH3−1 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.