Enhancing CO<sub>2</sub> Reduction Efficiency on Cobalt Phthalocyanine via Axial Ligation
Hongxing Kang, Aaliyah Staples‐West, Audrey Washington, Chris Turchiano, Andrew L. Cooksy, Jier Huang, Jing Gu
Abstract
Abstract Electrochemical reduction of carbon dioxide (CO 2 RR) to value‐added products is a promising strategy to alleviate the greenhouse gas effect. Molecular catalysts, such as cobalt (II) phthalocyanine (CoPc), are known to be efficient electrocatalysts that are capable of converting CO 2 into carbon monoxide (CO). Herein, we report an axial modification strategy to enhance CoPc's CO 2 RR performance. After coordinating with axial ligands, the electron density of Co was depleted via π‐backbonding. This π‐backbonding weakened the Co‐CO bond, resulting in rapid desorption of CO. Also, the presence axial ligands elevated the Co dz 2 orbital energy, resulting in a significantly enhanced CO selectivity, evidenced by an increased faradaic efficiency (FE) from 82 % (CoPc) to 91 % and 94 % with the presence of pyridine (CoPc‐py) and imidizal ligands (CoPc‐im), respectively, at −0.82 V vs. RHE. Density functional theory calculations reveal that axial ligation of CoPc can reduce the energy barrier for CO 2 activation and facilitate the formation of * COOH.