Enhancing Surface Strain of Intermetallic Fuel Cell Catalysts by Composition-Induced Phase Transition

The lattice parameter of platinum-based intermetallic compounds (IMCs), which correlates with the intrinsic activity of the oxygen reduction reaction (ORR), can be modulated by crystal phase engineering. However, the controlled preparation of IMCs with unconventional crystal structures remains highly challenging. Here, we demonstrate the synthesis of carbon-supported PtCu-based IMC catalysts with an unconventional L1₀ structure by a composition-regulated strategy. Experiment and machine learning reveal that the thermodynamically favorable structure changes from L1₁ to L1₀ when slight Cu atoms are substituted with Co. Benefiting from crystal-phase-induced strain enhancement, the prepared L1₀-type PtCu_0.8Co_0.2 catalyst exhibits much-enhanced mass and specific activities of 1.82 A mg_Pt^-1 and 3.27 mA cm_Pt^-2, which are 1.91 and 1.73 times higher than those of the L1₁-type PtCu catalyst, respectively. Our work highlights the important role of crystal phase in determining the surface strain of IMCs, and opens a promising avenue for the rational preparation of IMCs with different crystal phases by doping.