Fe2O3/ZnO heterojunction for efficient electrochemical nitrate reduction to ammonia†

Electrochemical nitrate reduction to ammonia (ENO₃RR) has attracted great attention owing to its characteristics of treating wastewater while producing high value-added ammonia. In this study, we successfully prepared a heterojunction electrocatalyst Fe₂O₃/ZnO consisting of Fe₂O₃ nanosheets and ZnO nanoparticles, where the construction of the Fe₂O₃/ZnO heterojunction not only increased the exposure of the active sites of the catalyst, accelerated the interfacial electron transfer, and improved the conductivity of the catalyst but also optimized its overall electronic structure. Thus, Fe₂O₃/ZnO demonstrated a high Faraday efficiency of 97.4% and an ammonia yield of 6327.2 μg h⁻¹ cm⁻² at −1.0 V (vs. RHE) in 0.1 M KNO₃ and 0.1 M PBS. DFT calculations also confirmed that the constructed Fe₂O₃/ZnO heterojunction effectively decreased the reaction energy barrier of *NO → *NHO and accelerated the reaction kinetics, which is favourable for ENO₃RR. This study provides a new and facile design strategy of catalysts for electrochemical nitrate reduction to ammonia.