Unravelling electrocatalytic properties of metal porphyrin-like complexes hosted in graphene matrices

Carbon-based materials are a promising class of catalysts for oxygen and carbon dioxide reduction reactions to value-added chemicals. Here we study the electrocatalytic properties of nitrogen doped graphene structures hosting four pyrrolic rings able to coordinate metal ions in a porphyrin-like configuration. The analysis is carried out by means of density functional theory (DFT) with hybrid functionals, employed to estimate the overpotentials of oxygen reduction reaction to water and hydrogen peroxide, as well as carbon dioxide reduction to carbon monoxide and formic acid. The competing hydrogen evolution reaction is also studied. We predict that Co- and Mn-doped structures exhibit low overpotentials for oxygen reduction to water, with the concurrent suppression of hydrogen peroxide production in the Mn case. Carbon dioxide reduction to formic acid is instead favored by Ti and Mn doping with overpotentials lower than 1 V, while hydrogen evolution reaction is disfavored.