Copper/carbon nanotube catalysts prepared by ion- exchange/electroreduction for electrocatalytic nitrate reduction: Enhanced performance and mechanism insight

Carbon-supported copper is a well-known catalyst for the electrocatalytic reduction of nitrate to ammonium/ ammonia (ECRNA). However, relatively low Cu utilisation and/or restricted ECRNA performance currently limit its practical applications. Here, we report a novel carbon nanotubes (CNTs)-supported Cu catalyst (IE-Cu/CNTs) for ECRNA fabricated through ion-exchange/electroreduction method. Versus traditional CNTs-supported Cu catalysts, the IE-Cu/CNTs have a small particle size of Cu. Moreover, an increased electrochemical surface area and improved electron transfer were observed for the IE-Cu/CNTs, resulting in a 2.22fold increase in the mass activity of the ECRNA, indicating enhanced Cu utilisation and ECRNA performance. In addition, the IE-Cu/CNTs exhibited high stability for ECRNA. Electrokinetic analysis, scavenging experiments, and online electrochemical mass spectrometry measurements confirmed that ECRNA is regulated over the IE-Cu/CNTs by both direct electron transfer reduction and indirect atomic hydrogen reduction, with the former being the main regulator. This work offers new suggestions for the design of high-performance catalysts for ECRNA and deepens the understanding of the ECRNA mechanism on Cu-based catalysts.

Automated summary

A new carbon nanotubes-supported copper catalyst (IE-Cu/CNTs) for the electrocatalytic reduction of nitrate to ammonium/ammonia (ECRNA) is reported in this study. The IE-Cu/CNTs catalyst shows a smaller particle size of copper compared to traditional CNTs-supported copper catalysts. It exhibits an increased electrochemical surface area and improved electron transfer, leading to enhanced Cu utilization and ECRNA performance. Moreover, the IE-Cu/CNTs catalyst demonstrates high stability for ECRNA, and the mechanism is regulated by both direct electron transfer reduction and indirect atomic hydrogen reduction.