Promoting the Cobalt Phthalocyanine-Catalyzed Electrochemical Reduction of Carbon Dioxide with the Coadsorption of Melamine.

Electrochemical reduction of carbon dioxide (CO2RR) is a promising strategy for mitigating global warming and producing value-added products simultaneously. Molecular catalysts, such as cobalt phthalocyanine (CoPc), are known to be effective in converting carbon dioxide (CO2) to carbon monoxide (CO). However, it is still challenging to improve the reaction rate and selectivity of this conversion. Herein, we report a simple and effective coadsorption strategy to promote the reaction rate and selectivity of CoPc-catalyzed CO2RR to CO by coadsorbing melamine molecules together with CoPc onto the surface of carbon nanotubes (CNTs). The coadsorption of melamine led to an increase in the output current density for 2.6-fold at an overpotential of -1.23 V vs Ag|AgCl. Moreover, the Faraday efficiency (FE) toward CO increased to 92% in an H-type cell, in contrast to the FE of 85% in the absence of melamine coadsorption. The FE toward CO further improved to 99% in a flow cell system. It was revealed that the coadsorption of melamine could modulate the surface adsorption of the *CO intermediates and decrease the energy barrier of CO2 reduction to CO. More importantly, only a solution-based process was employed in the whole procedure and no organic synthesis was involved, making our method highly simple, convenient, and environment friendly. This work paves an effective way for modulating the activity and selectivity of molecular catalysts in the CO2RR.