Fe 2 O 3 /ZnO heterojunction for efficient electrochemical nitrate reduction to ammonia.

Electrochemical nitrate reduction to ammonia (ENO 3 RR) 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 Fe 2 O 3 /ZnO consisting of Fe 2 O 3 nanosheets and ZnO nanoparticles, where the construction of the Fe 2 O 3 /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, Fe 2 O 3 /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 KNO 3 and 0.1 M PBS. DFT calculations also confirmed that the constructed Fe 2 O 3 /ZnO heterojunction effectively decreased the reaction energy barrier of *NO → *NHO and accelerated the reaction kinetics, which is favourable for ENO 3 RR. This study provides a new and facile design strategy of catalysts for electrochemical nitrate reduction to ammonia.