Electronic State Modulation via Electrochemical Reconstruction Enhances Dilute Nitrate-to-Ammonia Reduction Efficiency

Abstract

The electrochemical reduction of NO3- to NH3 represents a promising approach for producing a renewable fuel with high energy density. However, the problems such as low activity and/or selectivity in low-concentration solutions (≤100 ppm NO3--N) and instability of active sites still require to be overcame. In this work, Cu/ZnO heterostructure composite materials were synthesized for NO3RR. During the electrocatalysis process, the Cu/ZnO undergoes electrochemistry-driven structural reconstruction, generating CuZn bimetallic alloy phase. Under the dilute NO3--N solution of 100 ppm, the optimal Cu75Zn25 catalyst displays a FENH3 of 94.1% at -0.7 V vs. RHE, and a high NH3 yield of 414 mmol h-1 gcat-1. Density Functional Theory calculations and a series of characterizations unveil that the CuZn alloy phase alters the electronic state surrounding Cu, leading to the regulation of Cu d-band center and thereby optimizing the adsorption of intermediates. Meanwhile, forming new alloy phase inhibits the competitive HER as well. This study shows the prospect of CuZn composite catalyst in sustainable NH3 synthesis, which is convinced of having certain guiding significance for the efficient and eco-friendly conversion of effluents in the future.