*2.3. Characterization of Pd Particles and Pd–Pt Bimetallic Catalysts*

The surface morphologies of the Pd particles and the Pt−Pd bimetallic catalysts were investigated by a field-emission scanning electron microscope (Hitachi S-4800, Hitachi, Tokyo, Japan). The structure and composition of the Pt−Pd bimetallic catalysts were investigated by a transmission electron microscope (JEOL 2100F, JELO Ltd., Tokyo Japan) equipped with energy-dispersive X-ray (EDX) analysis. The phase and the crystallinity of the Pd–Pt bimetallic catalysts were analyzed by X-ray diffraction (XRD; Bruker D8 Advanced, Billerica, MA, USA) with CuK<sup>α</sup> radiation (λ = 1.5418 Å). The loading amounts of Pd and Pt particles were obtained by inductively coupled plasma-mass spectrometry (ICP-MS; Agilent 7700, Agilent Technologies, Santa Clara, CA, US).
