Universal Solid-Phase Seed-Mediated Synthesis of Monodisperse and Ultrasmall L1₀-PtM Intermetallic Nanocrystals

Intermetallic compounds have emerged as a class of promising electrocatalysts for fuel cells; however, it is still a great challenge to synthesize monodisperse and small intermetallic phases by an economical and scalable method. Herein, we demonstrate a generally applicable solid-phase seed-mediated diffusion strategy for controllable synthesis of ordered L1 0 -PtM (M = Mn, Fe, Co, and Zn) nanoparticles, where the preprepared monodispersed Pt seeds are used as the growth sites. The freeze-drying procedure produces monodisperse metal precursors on Pt/C, and the subsequent annealing process in a H 2 /Ar atmosphere obtains highly dispersed and ultrasmall PtM intermetallic nanocrystals (∼3 nm) on carbon supports. More importantly, such a strategy is also applicable to the preparation of a high-loaded PtMn intermetallic catalyst (50 wt %). Taking PtMn/C catalysts as examples, we illustrate their synthetic details and formation mechanism of the desired ordered phases. This approach eliminates the need for energy-consuming filtering and washing procedures, which makes it very promising for large-scale production.