Constructing a Bifunctional Heterointerface Realizes Superior Electroreduction of Nitrate-Enriched Wastewater with Wide Concentrations for Ammonia Production

Electrochemical nitrate (NO3–) reduction reaction (NO3RR), emerges as an ingenious approach to the alternative Haber–Bosch process for ammonia (NH3) synthesis, while the investigation on high performance catalysts remains difficult in regulating NO3– adsorption. Herein, we develop a feasible strategy that can simultaneously modulate the adsorption behavior of NO3– and thereby lower the energy barrier for NH3 formation by constructing Cu/Cu2O heterointerface with in situ electrochemical transformation of Cu2(OH)2CO3, realizing over 90% Faradaic efficiency (FE) under concentrations from 50 to 1400 ppm, with superior NH3 yields (0.936–11.21 mg h–1 mg–1). Synchrotron radiation–Fourier transform infrared spectroscopy) and density functional theory calculations decipher that the Cu/Cu2O heterointerface can realize the balanced adsorption capability of NO3– and facilitate the formation of the *NOH intermediate to largely lower the energy barrier of the rate-determining step. The two-electrode flow cell measurement demonstrates its efficiency and practicability to produce a high purity NH4Cl solid and NH3 solution. This work not only provides a rationale for catalyst design for the NO3RR but also indicates the feasibility of converting wastewater NO3– into valuable NH3 products.