Steering CO2 Electroreduction Pathway via Tuning Microenvironment of Cobalt Center in Molecular Catalysts

Owing to its chemical stability and molecular-level structural tunability, the molecular electrocatalyst cobalt phthalocyanine (CoPc) demonstrates significant potential for the electrochemical reduction of CO2 (CO2RR). However, the specific catalytic reaction process of CO2RR and the dynamic structural evolution mechanisms of CoPc remain a contentious subject. Elucidating the reaction pathways of CO2 electroreduction to CO and tracking structural evolution pose substantial challenges. In this study, we first used density functional theory (DFT) calculations to reveal the sequential proton-electron transfer (SPET) mechanisms for CO2RR on CoPc. Moreover, in situ X-ray absorption spectroscopy (XAS) elucidated a detailed deactivation mechanism, providing insights into the transition from single atomic sites (SAs) to nitrogen-coordinated nanoclusters (NCs) during CO2 reduction. Based on these insights, we modified the pendant groups by introducing electron-withdrawing fluorine groups to change the reaction pathways of *-COOH2- to the concerted proton-electron transfer (CPET) process, thereby effectively promoting the CO2 electroreduction to CO. The presence of electron-withdrawing fluorine groups triggers central electron delocalization within CoPc, effectively mitigating the demetalation effect and enhancing the electron donation ability of Co active sites. As a result, we observed a markedly enhanced CO2RR performance, exhibiting high stability, activity, and FECO compared to unmodified CoPc. This study contributes to the broader understanding of designing efficient molecular electrocatalysts for CO2RR.