Redox-active covalent organic nanosheets (CONs) as a metal-free electrocatalyst for selective CO2 electro-reduction to the liquid fuel methanol

Abstract

In essence, the utilization of renewable energy in the carbon dioxide reduction reaction (CO₂RR) holds the potential to transform carbon emissions into valuable chemicals, encompassing a range of hydrocarbons and alcohols. Herein, we have implemented a redox-active triphenylamine (TPA)-based covalent organic nanosheets (CONs) as a metal-free electrocatalyst for CO₂ reduction in 0.2 M phosphate buffer (pH-7.2). The reaction produced methanol as the only carbonaceous liquid product reaching a maximum faradaic efficiency (FE) of 51.6% under mild reaction conditions in aqueous medium. Moreover, the corresponding overpotential of the reaction was as low as 210 mV illustrating the superiority of this metal-free electrocatalyst. The mechanistic aspects are supported through experimental in situ RAS-IR (reflection–absorption), in situ Raman study as well as computational study. The superior performance of the electrocatalyst is believed to be due to the presence of redox-active 2-D nanosheets with exposed active sites. This work unlocks a way to produce methanol efficiently by the electrochemical reduction of CO₂.