Inter-Sublattice Random Pt(Co,Ni) Alloy Nanoparticle Catalysts for Highly Efficient Oxygen Reduction Reaction

Abstract

The rigid atomic ordering in Pt-based intermetallic catalysts enhances structural stability but inherently restricts local electronic tunability and compositional flexibility. These limitations hinder catalyst optimization under dynamic electrochemical conditions in proton exchange membrane fuel cells (PEMFCs). To overcome this, an inter-sublattice random (ISR) alloy strategy is reported that integrates atomic-level compositional disorder into a structurally ordered Pt-M (M = Co, Ni) framework. Using a two-step heteroepitaxial growth approach, Ni atoms are introduced into the M-sublattice of a PtCo intermetallic seed, forming a catalyst with retained crystallographic order and randomized Co/Ni distribution. This dual order-disorder motif decouples structural symmetry from chemical complexity, offering precise electronic modulation and reaction-adaptive flexibility. The ISR catalyst exhibits optimized d-band filling and intermediate binding, achieving ORR activity and durability that surpass the Department of Energy (DOE) 2025 PEMFC targets. Mechanistic analyses combining in situ microscopic observation, synchrotron spectroscopy and density functional theory (DFT) calculations reveal that sublattice disorder and Pt-skin formation synergistically stabilize the surface structure and modulate adsorption energy. This work establishes sublattice-level disorder engineering within intermetallic structures as a promising synthetic strategy for developing robust and tunable electrocatalysts. Moreover, the solid-state synthesis enables scalable production for widespread PEMFC deployment.