Synergism of electrostatic attraction and tandem catalytic effect enabled efficient electrosynthesis of ammonia from a wide-range of nitrate concentrations

Abstract

Electrochemical reduction of nitrate to ammonia provides a promising route to sustainable ammonia synthesis under mild conditions. Herein, we reported a metal–organic framework-derived CuCo bimetallic nanoparticles/nitrogen-doped carbon (CuCo/CN) composite electrocatalyst for nitrate-to-ammonia conversion. Strong interface coupling between CuCo nanoparticles and CN matrix enables enhanced electrostatic attraction effect and availably triggers accumulation of nitrate at electrocatalyst surfaces. Moreover, the incorporated Co site could effectively supply hydrogen radical in favor of achieving dynamic equilibrium of active hydrogen. Owing to these unique properties, the CuCo/CN electrocatalyst achieved an unprecedented ammonia Faradaic efficiency (>84 %) across a wide range of nitrate concentrations from 20 to 2000 ppm, with an optimal Faradaic efficiency of 93.56 % at 200 ppm. Excitingly, coupling nitrate reduction reaction to methanol oxidation reaction (by replacing sluggish oxygen evolution reaction) could further reduce total electrolytic voltage of conventional nitrate-to-ammonia system, and produce value-added chemicals on both sides of the electrolyzer.