Ru@Pt Core-Shell Nanoparticles: Impact of the Atomic Ordering of the Ru Metal Core on the Electrocatalytic Activity of the Pt Shell

Constructing core-shell nanostructures is demonstrated to be an effective strategy to improve catalytic activity of metal nanoparticles. However, the impact of the atomic ordering of the metal core on the performance of the shell remains unexplored. Here, ruthenium-platinum (Ru-Pt) core-shell nanoparticles, with a crystalline and amorphous Ru core of the same diameter and diverse Pt shell thicknesses, are prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-angle annular dark-field scanning transition electron spectroscopy (HAADF-STEM), and CO tripping voltammetry. The well-defined heterostructured Ru-Pt interface and anisotropic growth of the Pt shell on the crystalline Ru core (Ru@Pt-x) were observed, while the amorphous Ru core induces a partial alloy at the Ru-Pt interface and isotropic growth of the Pt shell. The core-shell structure also results in an apparent down-shift of the d-band center of Pt, which dissipates much faster on the amorphous Ru core than on crystalline ones, as demonstrated by the XRD and CO desorption potential. The two sets of core-shell nanoparticles show that a volcano-shape dependence of the catalytic activity on the thickness of the Pt shell and the crystalline Ru core markedly enhanced the catalytic performance and stability toward electro-oxidation of formic acid and ethanol, which is ascribed to the lattice strain of the Pt shell, down-shift of the d-band center, the weakened CO adsorption, and thus alleviated poisoning.