Near 100% selectivity for ammonia synthesis at a high current density by promoting nitrate protonation on the copper dispersed todorokite-type manganese oxide

Abstract

Electrochemical nitrate reduction reaction (NITRR) has attracted much attention for yielding ammonia. Thus, it is of great significance to exploit new catalysts with a high nitrate-to-ammonia (NO₃⁻-to-NH₃) activity. In this study, we embedded different concentrations of Cu in an oxide octahedral molecular sieve (Cu(x)-OMS-1). We found that the Cu-dispersed OMS-1 optimizes the adsorption capabilities of the intermediates in NITRR and inhibits the competitive HER at a high current density. We reveal, using operando Fourier transform infrared spectroscopy and theoretical investigations, that the introduction of copper effectively promotes nitrate protonation during NITRR. Consequently, the catalyst presents the capacity for reducing nitrate to ammonia at a high current density (>100 mA cm⁻²) with ∼100% Faraday efficiency. The maximum NH₃ partial current density reaches 148 mA cm⁻² with a high production rate (0.69 mmol h⁻¹ cm⁻²).