DFT Study for Oxygen Reduction and Oxygen Evolution Reactions in Pyrochlore Oxides as Bi-functional Electrocatalysts

Abstract

In this study, we studied about the oxygen reduction and oxygen evolution reactions in pyrochlore oxides to investigate the capability as bi-functional electrocatalysts. Initially, the most stable surface terminations were determined by relaxed surface energy calculations. From the most stable terminations including (100), (110), and (111) directions, the reaction intermediates (e.g. OOH*, O*, and OH*) were calculated to investigate the free energy diagrams for oxygen reduction and oxygen evolution reactions (ORR/OER). The results showed that the overpotentials for both reactions were decreased as the –OH coverage increased in alkaline environment. Also, the (110) surface was the most favorable among the surfaces. It was also found that the rubidium site was favorable for ORR whereas the bismuth site was favorable for OER.