Bridging Oxide Thermodynamics and Site-Blocking: A Computational Study of ORR Activity on Platinum Nanoparticles

The Oxygen Reduction Reaction (ORR) is a key reaction in fuel cells and metal-air batteries, where high overpotentials remain a critical challenge despite extensive research. While experimental studies have revealed the importance of surface oxidation, a unified computational framework capable of simultaneously capturing both the thermodynamic aspects of rate-determining steps and the kinetic effects of site-blocking on the overpotential has remained elusive. In this work, we present a novel computational approach that bridges this gap by combining grand-canonical Monte Carlo simulations with the MACE-MP-0 foundation model to study the ORR on experimentally reconstructed Pt nanoparticles. This framework enables the systematic investigation of oxidation effects across multiple scales, from atomic-level place-exchange mechanisms to macroscopic kinetic behavior. Our simulations reveal a strong dependence of system thermodynamics on oxygen coverage and successfully predict the place-exchange mechanism onset at 1.06 V vs. SHE, in agreement with experimental observations. Through established scaling relations and deletion energy analysis, we quantify both the rate-determining step and the distribution of reactive sites on the oxidized surface, providing insight into the complex interplay between surface oxidation and ORR activity. By linking our results with both theoretical and experimental benchmarks on multiple points, we ensure the viability of our assumptions and approach. Using a simplified kinetic model derived from our simulations, we demonstrate agreement with core experimental observations, validating the predictive power of foundation models in computational electrochemistry. This work not only provides a comprehensive understanding of oxide effects in ORR but also establishes a versatile computational methodology that can be readily extended to study similar electrochemical processes on other catalytic systems, offering a powerful new tool for rational catalyst design.