Computational Screening of Transition Metal-Phthalocyanines for the Electrochemical Reduction of Carbon Dioxide

Molecular complexes containing low-cost transition-metal (TM) centers have been extensively studied for the electrochemical reduction of carbon dioxide. Of all the molecular catalysts reported so far, only a few of them are selective for CO2 reduction, and moreover, these catalysts mainly produce carbon monoxide or formic acid. However, molecular catalysts generating highly reduced products such as hydrocarbons are very rare. Herein, we explore the electrocatalytic activity of TM-Phthalocyanine (TM-Pc) by placing different transition metals into the vacant N-4 cavity toward the reduction of CO2. By using first-principles calculations, we demonstrate that among all the 3d transition metals used, Chromium-Phthalocyanine (Cr-Pc)-Pc shows excellent performance for converting CO2 to methane with a limiting potential of -0.34 V. In comparison, the limiting potentials for the CO2 reduction reaction (CO2RR) to CH4 for the best catalyst considered so far such as Cu(111) and Cu(211) are -0.93 V and -0.74 V, respectively. Chromium, being a non-noble metal, presents as a promising TM for catalyzing CO2RR. Co-Pc however converts CO2 to methanol with a limiting potential of -0.69 V. This report shows that Pc with different TMs can provide an effective pathway for tuning the catalytic performance of electrocatalysts, which could help in the design of molecular catalysts in the future that will expectantly soon emerge at an industrial scale.