Oxygen Reduction Reaction on Metal-Terminated MnCr₂O₄ Nano-octahedron Catalyzing MnS Dissolution in an Austenitic Stainless Steel

To understand pitting corrosion in stainless steel is very important, and a recent work showed that the MnS dissolution catalyzed by MnCr 2 O 4 {111} is a starting point of pitting. This demonstrates the need to understand the oxygen reduction reaction (ORR) on MnCr 2 O 4 {111}, which is the other half-reaction to complete pitting corrosion. In this study, the adsorption behaviors of all oxygen-containing species on MnCr 2 O 4 {111}, which has several possible terminations, are explored via density functional theory calculations. It is found that O 2 adsorbs on MnCr 2 O 4 {111} surfaces very strongly. Many possible reactions are investigated and the favored reaction mechanism of ORR is determined. The interactions between O 2 and H 2 O on the two metal-terminated MnCr 2 O 4 {111} are found to be different according to the atomic configurations of the two surfaces. All the calculated results suggest that ORR can readily occur on the MnCr 2 O 4 {111} surfaces.