In-situ spectroscopic probe of the intrinsic structure feature of single-atom center in electrochemical CO/CO 2 reduction to methanol.

While exploring the process of CO/CO 2 electroreduction (CO x RR) is of great significance to achieve carbon recycling, deciphering reaction mechanisms so as to further design catalytic systems able to overcome sluggish kinetics remains challenging. In this work, a model single-Co-atom catalyst with well-defined coordination structure is developed and employed as a platform to unravel the underlying reaction mechanism of CO x RR. The as-prepared single-Co-atom catalyst exhibits a maximum methanol Faradaic efficiency as high as 65% at 30 mA/cm 2 in a membrane electrode assembly electrolyzer, while on the contrary, the reduction pathway of CO 2 to methanol is strongly decreased in CO 2 RR. In-situ X-ray absorption and Fourier-transform infrared spectroscopies point to a different adsorption configuration of *CO intermediate in CORR as compared to that in CO 2 RR, with a weaker stretching vibration of the C-O bond in the former case. Theoretical calculations further evidence the low energy barrier for the formation of a H-CoPc-CO - species, which is a critical factor in promoting the electrochemical reduction of CO to methanol.