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

Mitigating nitrogen oxide (NO) emissions is critical to tackle global warming and improve air quality. Conventional NO abatement technologies for emission control suffer from a low efficiency at near ambient temperatures. Herein, we show an electrochemical pathway to reduce gaseous NO 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 emissions at ambient conditions by using renewable electricity.