Highly dispersed copper-iron nanoalloy enhanced electrocatalytic reduction coupled with plasma oxidation for ammonia synthesis from ubiquitous air and water

Abstract

Conversion of nitrogen to ammonia at ambient conditions is a promising avenue for future distributed energy storage and fertilizer supply. However, it is currently hindered by the difficult nitrogen activation and competitive hydrogen evolution reaction. Herein, we develop a new strategy of highly dispersed copper-iron (Cu-Fe) nanoalloy enhanced electrocatalytic nitrate reduction to ammonia (NRA), in which nitrate can be derived from nitrogen and oxygen in the air via plasma process. The nitrate obtained by plasma oxidation of air is more than 3 times as much as nitrite, and the total yield rate of nitrate and nitrite is over 137 μmol·h1 by a single electrode of Tesla coil. Highly dispersed Cu-Fe nanoalloy with different ratios of Cu to Fe were prepared for NRA catalysts using the Joule heating method with instantaneous thermal shock, Cu10Fe1 nanoalloy demonstrates the best NRA activity, exhibits an excellent ammonia yield rate of 190.46 μmol·h1·cm2 and Faraday efficiency of 93.74 %. The Kelvin probe force microscope, in situ electrochemical Raman spectroscopy and density functional theory reveal the enhancing effect and tuning mechanism of Fe atom on the adsorption energy and electronic structure of Cu. This work opens up a new pathway for ammonia synthesis from air and water and provides a new strategy for the construction of high-performance NRA catalysts and the analysis of the reaction mechanism.