Delocalizing d Orbital in Co-N4-Centered Molecular Catalysts via π-d Interactions for CO2 Electroreduction

Molecules with metal-N 4 centers have been widely applied as efficient catalysts in electrocatalytic CO 2 reduction (ECR) to CO. However, the localized d orbitals of the metal centers significantly hindered the mass and electron transfer of the CO 2-to-CO process. Herein, we propose a pi- d interaction regulation strategy that involves tuning the molecular conjugated structure to delocalize the metal d orbital of Co-N 4-centered molecular catalysts for ECR. The cobalt naphthalocyanine (CoNPc) with an extended conjugated structure exhibits a superior ECR performance compared to cobalt phthalocyanine (CoPc) and cobalt octaethylporphyrin (CoOEP), with the highest CO faradaic efficiency (FE CO ), reaching 96.1% at -0.8 V versus reversible hydrogen electrode in an H-cell and 97% at 100 mA cm -2 in flow cell using a bicarbonate electrolyte. Furthermore, the electrochemical scanning tunneling microscopy and theoretical analyses reveal that the extended conjugated structures promoted CO 2 adsorption and CO desorption on Co-N 4 active sites, thus accelerating the ECR process. These results provide insights into the design of high-performance metal-N 4-centered electrocatalysts.