Revealing Substituent Effects in CO to CH₃OH Conversion on a Cobalt Phthalocyanine Catalyst Using DFT Method

The electrochemical transformation of carbon monoxide (CO), which is a primary one-carbon result of the carbon dioxide (CO₂) reduction reaction (CO₂RR), into useful chemical compounds is a promising method for achieving carbon neutrality. Here, we use density functional theory (DFT) to study the detailed mechanism for the CO reduction reaction (CORR) to methanol (CH₃OH) on cobalt phthalocyanine (CoPc) catalyst and the effect of the substituents on the overpotential (η). For all considered complexes, the rate-determining step (RDS) is found to be the transformation of the *CHO intermediate to the *OCH₂ intermediate. According to our DFT calculations, the most favorable pathway for the CO to CH₃OH formation for all the complexes is *CO → *CHO → *OCH₂ → *CH₂OH → CH₃OH. Moreover, our results suggest that substitutions of electron-donating groups on the phthalocyanine ligand increase the η values, whereas substitutions of electron-withdrawing groups decrease the η values. Our results suggest that appropriate substitutions on the macrocycle ligands can be used to design an efficient electrocatalyst with excellent product selectivity, and a minimum overpotential, motivating further experimental and theoretical investigations of molecular catalysts for CO₂RR or CORR into valuable products.