Density Functional Theory Study of an Oxygen Reduction Reaction on a Pt3Ti Alloy Electrocatalyst

First-principles density functional theory calculations were performed to investigate the pathway of oxygen reduction reaction (ORR) on a Pt surface-segregated Pt3Ti(111) surface. Our calculation results indicate that the ORR intermediates (H, O, OH, O-2, OOH, and H2O) would bind weakly on the Pt3Ti(111) surface compared to those on the pure Pt(111) surface. The possible ORR mechanism on the Pt3Ti(111) surface is elucidated by calculating the activation energies for all of the possible elementary reaction steps in ORR. We predict that the ORR on the Pt3Ti(111) surface proceeds via a H2O2 dissociation mechanism. Importantly, the activation energy for the rate determining step in the H2O2 dissociation mechanism on the Pt3Ti(111) surface is significantly lower than the corresponding value on the pure Pt(111) surface. This provides an explanation for the experimentally observed superior ORR performance of Pt3Ti electrocatalyst in comparison to pure Pt electrocatalyst. Furthermore, we studied the degradation behavior of Pt3Ti electrocatalyst by evaluating the electrochemical potential shift of surface Pt dissolution and the formation energy of a a-PtO2 layer on the Pt3Ti(111) surface. Our computations predict an enhanced stability of the Pt3Ti(111) surface against surface Pt dissolution and surface oxidation in comparison to that of the pure Pt(111) surface.