Monoatomic metalloporphyrinoid catalysts for efficient oxygen reduction

In this research, we present a comprehensive investigation on the catalyst screening, reaction mechanism, and electrocatalytic properties of two-dimensional monoatomic metalloporphyrinoid (MPor) materials for the oxygen reduction reaction (ORR). Through a combination of high-throughput screening, first-principles DFT calculations, and molecular dynamics simulations, we uncovered some promising oxygen reduction catalysts with limiting potentials of 0.60, 0.57, 0.56 V under acidic medium, and −0.17, −0.20, −0.21 V under basic medium for M = Co, Fe, Mn, respectively. Full reaction pathway search demonstrates that CoPor is a special case with 2e^– and 4e^– paths under both acidic and basic media, and for FePor and MnPor, only 4e^– path is viable. In-depth analyses indicate that the adsorption free energy of OH and limiting potential shows the volcano curve relationship, which can guide the design and optimization of the ORR catalysts. The crystal orbital Hamiltonian population (COHP) between M and O in O₂-MPor can well explain why only CoPor has a 2e^– path, while other metals do not, because the Co–O bond is much weaker compared to other M–O bonds. Our research will shed some insights on designing efficient ORR catalysts, and stimulate the experimental efforts in this direction.