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

Abstract

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 [*-COOH]^2- 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 FE_CO compared to unmodified CoPc. This study contributes to the broader understanding of designing efficient molecular electrocatalysts for CO₂RR.