Rational design and mechanistic elucidation of Pt-based alloy-supported Fe1(OH)3 interfaces for superior CO oxidation catalysis.

Abstract

The development of active and stable CO oxidation catalysts is critical for PEMFCs, as they purify hydrogen fuel and mitigate cathode poisoning, determining cell efficiency and operational lifetime. In this work, we present a rational design strategy for such catalysts via first-principles calculations. We constructed well-defined Fe₁(OH)₃/M₁Pt interfaces by anchoring Fe₁(OH)₃ clusters onto transition-metal-doped Pt surfaces. A multi-step screening strategy was implemented to screen sixteen transition metals, identifying Cu, Zn, Ag, and Au as optimal dopants that fine-tune *CO adsorption strength into a favorable range. These catalysts exhibit moderate *CO adsorption energies and significantly reduced Gibbs free-energy barriers for the rate-determining step compared to the Fe₁(OH)₃/Pt reference. The activity originates from a balance between moderate *CO adsorption and hydrogen-bond stabilization of *COOH by the Fe₁(OH)₃ site. Alloying the Pt support with Cu, Zn, Ag, or Au leads to more exothermic *COOH formation and enhances the reaction kinetics by lowering the kinetic barriers. Electronic analysis reveals that the cohesive energy of the dopant metal and the number of unpaired d-electrons serve as key descriptors for *CO adsorption strength. This work provides a comprehensive design strategy and fundamental insights for developing highly active and stable single-site catalysts for CO oxidation in PEMFCs.