Heterogenized Pyridine-Substituted Cobalt(II) Phthalocyanine Yields Reduction of CO₂ by Tuning the Electron Affinity of the Co Center

Abstract

Conversion of CO₂ to reduced products is a promising route to alleviate irreversible climate change. Here we report the synthesis of a Co-based phthalocyanine with pyridine moieties (CoPc-Pyr), which is supported on a carbon electrode and shows Faradaic efficiency ∼90% for CO at 490 mV of overpotential (-0.6 V vs reversible hydrogen electrode (RHE)). In addition, its catalytic activity at -0.7 V versus RHE surpasses other Co-based molecular and metal-organic framework catalysts for CO₂ reduction at this bias. Density functional theory calculations show that pyridine moieties enhance CO₂ adsorption and electron affinity of the Co center by an inductive effect, thus lowering the overpotential necessary for CO₂ conversion. Our study shows that CoPc-Pyr reduces CO₂ at lower overpotential and with higher activity than noble metal electrodes, such as silver.