# Developing Interface Force Fields for Water and Oxygen on Pt, and Pt 3 Ni, Pt 3 Co Alloy Surfaces for Proton-Exchange Membrane Fuel Cell (PEMFC) Applications

## TL;DR

This paper develops accurate interface force fields for modeling water and oxygen interactions on platinum and alloy surfaces in fuel cells.

## Contribution

A new framework for optimizing interface force fields with reduced errors compared to existing methods like COMB3 and ReaxFF.

## Key findings

- The best interface force field reduces energy errors by 70–90% and force errors by 44–48% compared to existing models.
- Similar improvements are observed for Pt3Ni and Pt3Co surfaces interacting with water and oxygen.
- O2 dissociation on metal surfaces remains challenging for classical force fields, with larger errors in parallel force components.

## Abstract

Interface force fields
(IFFs) are crucial for the atomistic
modeling
of PEMFC interfaces. We benchmark ten optimization algorithms and
four force-field forms against DFT adsorption energies and forces
and present a framework for selecting the algorithm/force-field combination.
At Pt–H2O, the best IFF yields a mean absolute error
(MAE) of 0.32 eV for adsorption energy and 0.12 eV/Å2 for forces, cutting energy error by 70–90% and force error
by 44–48% compared to COMB3, ReaxFF, and LJ mixing. Similar
improvements are observed for Pt3Ni–H2O and Pt3Co–H2O. For Pt/Pt3Ni/Pt3Co–O2, energy MAEs are 0.30–0.68
eV and force MAEs are 0.42–0.85 eV/Å2; errors
are larger for force components parallel to the surface, while normal
components remain well captured, reflecting the challenges of describing
O2 dissociation on (111) metal surfaces using classical
force fields. The framework enables data-efficient IFF development
and guides the selection of force-field forms and optimization algorithms
for PEMFC and interfacial simulations.