Improving CO electroconversion by customizing the hydroxyl microenvironment around a semi-open Co-NO configuration.

Constructing local microenvironments is one of the important strategies to improve the electrocatalytic performances, such as in electrochemical CO reduction (ECR). However, effectively customizing these microenvironments remains a significant challenge. Herein, utilizing carbon nanotube (CNT) heterostructured semi-open Co-NO catalytic configurations (Co-salophen), we have demonstrated the role of the local microenvironment on promoting ECR through regulating the location of hydroxyl groups. Concretely, compared with the maximum Faradaic efficiency (FE) of 62% for carbon monoxide (CO) presented by Co-salophen/CNT without a hydroxyl microenvironment, the designed Co-salophen-OH/CNT, featuring hydroxyl groups at the Co-NO structural opening, shows remarkable CO-to-CO electroreduction activity across a wide potential window, with the FE of CO up to 95%. In particular, through the deuterium kinetic isotope experiments and theoretical calculations, we decoded that the hydroxyl groups act as a proton relay station, promoting the efficient transfer of protons to the Co-NO active sites. The finding demonstrates a promising molecular design strategy for enhancing electrocatalysis.