Molybdenum Microalloying L1₂‐Pt₃Co Intermetallic Compounds via Bimodal Ordering Process by Mo Surface Termination and PDA‐Coated Particle Confinement for Stable PEMFC

Abstract Ordered platinum (Pt) intermetallic compounds with high performance expression under proton exchange membrane fuel cell (PEMFC) operating conditions are a prerequisite for practical application. However, the heat treatment required for forming an ordered structure can lead to severe agglomeration and uneven distribution of nanoparticles, posing a significant challenge to efficient synthesis. Here, a molybdenum (Mo) assisted structural evolution strategy to controllably synthesize sub‐4 nm Pt₃Co intermetallic compounds is proposed. The results of experiments combined with density functional theory calculations demonstrate that the participation of trace Mo (0.2 wt.%) not only triggers the “growth site locking effect” and effectively suppresses the growth of nanoparticles, but also effectively adjusts the electronic structure, thereby optimizing the adsorption/desorption of oxygen intermediates. The preeminent intrinsic activity on an optimized catalyst reaches a mass activity as high as 1.22 A mg_Pt⁻¹ and has extraordinary stability with only a 5.7% decrease after 30 k cycles. This study paves a new path for the practical application of low Pt catalysts in PEMFCs in the future.