Promoting Electrocatalytic CO₂ Reduction to CH₄ by Copper Porphyrin with Donor–Acceptor Structures

Abstract

Molecular catalysts have been receiving increasingly attention in the electrochemical CO₂ reduction reaction (CO₂ RR) with attractive features such as precise catalytic sites and tunable ligands. However, the insufficient activity and low selectivity of deep reduction products restrain the utilization of molecular catalysts in CO₂ RR. Herein, a donor-acceptor modified Cu porphyrin (CuTAPP) is developed, in which amino groups are linked to donate electrons toward the central CuN₄ site to enhance the CO₂ RR activity. The CuTAPP catalyst exhibited an excellent CO₂ -to-CH₄ electroreduction performance, including a high CH₄ partial current density of 290.5 mA cm^-2 and a corresponding Faradaic efficiency of 54.8% at -1.63 V versus reversible hydrogen electrode in flow cells. Density functional theory calculations indicated that CuTAPP presented a much lower energy gap in the pathway of producing *CHO than Cu porphyrin without amino group modification. This work suggests a useful strategy of introducing designed donor-acceptor structures into molecular catalysts for enhancing electrochemical CO₂ conversion toward deep reduction products.