Acceptable mechanisms for oxygen reduction reaction on Fe-C₄₄ and Fe-Si₄₄ surfaces as potential catalysts in an acidic environment

This study examined the potential of using Fe-C-44 and Fe-Si-44 to catalyze the reaction steps in the oxygen reduction reaction (ORR) in an acidic environment based on theoretical models. The formation energy and adoption energy values of Fe-C-44 and Fe-Si-44 were calculated by using the B3LYP/cc-pVQZ method. The capacities of Fe-C-44 and Fe-Si-44 to adsorb O, OH, OOH, O-2, and H2O species were examined, and the results showed that H2O was readily desorbed from Fe-C-44 and Fe-Si-44. The acceptable mechanisms for ORR on Fe-C-44 and Fe-Si-44 were determined from thermodynamic viewpoints. The activation barrier energy (E-activation) and reaction Gibbs free energy (Delta G(reaction)) in all ORR reaction steps via possible mechanisms on Fe-C-44 and Fe-Si-44 were examined in an acidic environment, and the results showed that the over-potentials of the ORR reaction steps were lower on Fe-C-44 and Fe-Si-44 than platinum catalysts.