Molybdenum Microalloying L1-PtCo Intermetallic Compounds via Bimodal Ordering Process by Mo Surface Termination and PDA-Coated Particle Confinement for Stable PEMFC.

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 PtCo 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 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.