Electrochemical Reduction of Gaseous Nitrogen Oxides on Transition Metals at Ambient Conditions

Abstract

Mitigating nitrogen oxide (NO_x) emissions is critical to tackle global warming and improve air quality. Conventional NO_x abatement technologies for emission control suffer from a low efficiency at near ambient temperatures. Herein, we show an electrochemical pathway to reduce gaseous NO_x that can be conducted at high reaction rates (400 mA cm^-2) under ambient conditions. Various transition metals are evaluated for electrochemical reduction of NO and N₂O to reveal the role of electrocatalyst in determining the product selectivity. Specifically, Cu is highly selective toward NH₃ formation with >80% Faradaic efficiency in NO electroreduction. Furthermore, the partial pressure study of NO electroreduction revealed that a high NO coverage facilitates the N-N coupling reaction. In acidic electrolytes, the formation of NH₃ is greatly favored, whereas the N₂ production is suppressed. Additional mechanistic studies were conducted by using flow electrochemical mass spectrometry to gain further insights into reaction pathways. This work provides a promising avenue toward abating gaseous NO_x emissions at ambient conditions by using renewable electricity.