Alkaline ORR Pathway on Spinel Electrocatalysts Revealed Through Joint Density-Functional Theory*

The oxygen reduction reaction (ORR) features prominently and is of fundamental importance in the field of electrocatalysis, with direct applications to fuel cells. The alkaline ORR on metal oxide surfaces shows great promise to reduce/eliminate the need for costly platinum group metals (PGMs). This reaction is currently thought to proceed through the intermediates *OH, *O₂, *OOH, and *O. We have investigated these intermediates using ab initio joint density-functional theory (JDFT) to describe the electrochemical interface. In particular, we studied the above intermediates on spinel Co₃O₄ and CoMn₂O₄. We find that the energies of the traditional intermediates do not agree with the observed experimental values of the ORR half-wave potential. However, splitting the reaction intermediates, hydrogenating the surface, and angling the adsorbates to form additional surface bonds significantly improves agreement with experiment. Given the agreement of this new reaction pathway with experimental data, we propose a new pathway for the alkaline ORR on spinel electrocatalyst materials.