High-efficiency ammonia synthesis via electrochemical nitrate reduction over Co3O4 nanoarrays by B doping

Abstract

Electrochemical conversion of nitrate to valuable ammonia (NH₃) is a green and widely used approach to NH₃ synthesis that can be an attractive and complementary alternative to the Haber–Bosch process. However, due to the multi-step reactions in the nitrate reduction pathway, there are still challenges in developing efficient catalysts that can selectively guide the reaction route towards NH₃. Herein, B doping is proposed as an effective strategy to enhance nitrate conversion to NH₃ on the Co₃O₄ nanoarrays, which not only improves the electrical conductivity of Co₃O₄, but also lowers the energy barrier of the potential-determining step. Such B-Co₃O₄/TM delivers a high faradaic efficiency of 94.7% and a large NH₃ yield rate of 407.3 μmol h⁻¹ cm⁻². Theoretical calculations further elucidate that the introduction of B enhances the adsorption characteristic of Co₃O₄ for NO₃⁻, consequently facilitating the reduction kinetics.