Oxygen reduction reaction on Pt(1 1 1), Pt(2 2 1), and Ni/Au1Pt3(2 2 1) surfaces: Probing scaling relationships of reaction energetics and interfacial composition

Abstract

In this work, we investigate the oxygen reduction reaction (ORR) on Pt(1 1 1), Pt(2 2 1), and Ni/Au1Pt3(2 2 1) surfaces using periodic density functional theory (DFT) calculations augmented with kinetic Monte Carlo (KMC) simulations. In the DFT calculations, both a uniform electric field and an implicit solvent were employed to quantify the changes in the ORR energetics. Based on the DFT values and the reaction mechanism of ORR, KMC simulations were performed to predict the current densities and the surface populations as a function of the electrode potential on the different catalyst surfaces. These results were compared to an ORR model with energetics approximated using scaling relationships. The two approaches for obtaining energetic parameters yield different KMC-predicted polarization curves. An analysis of the surface species concentrations on Pt(1 1 1), Pt(2 2 1), and Ni/Au1Pt3(2 2 1) indicates dramatic concentration variations at different potentials. Direct neighbor-neighbor interactions on the surface were also tested, but they were found to only moderately influence the surface species concentrations, and they led to imperceptible changes in the predicted current densities. Overall, we predict that an alloy surface of Ni/Au1Pt3(2 2 1) can significantly shift the onset potential of the polarization curve to higher potentials, providing guidance for future electrocatalyst design.