Fig. 1. (a) TEM image of Pt-Ni CNPs. Inset: graph of the diameter distribution of nanoparticles; (b) TEM image of a single Pt-Ni CNPs at a higher magnification; (c) HAADF-STEM images of Pt-Ni CNPs; (d) and (e) are EDS element distribution images of Pt and Ni in Pt-Ni CNPs corresponding to (c), respectively.

Fig. 2. (a) XRD patterns of Pt-Ni CNPs and standard card peaks of Pt and Ni (corresponding to red and blue respectively); (b) EDS spectrum of Pt-Ni CNPs; (c) and (d) are XPS spectra of Pt-Ni CNPs, corresponding to the 4f peak of Pt and the 2p peak of Ni, respectively.

Fig. 3. MOR performance comparison for Pt-Ni CNPs (red) and commercial Pt/C (black): (a) CV of the above catalysts for ECSAs; (b) CV of the above catalysts for MOR; (c) corresponding mass and specific activities of different catalysts for MOR; (d) LSV curves of the above electrocatalysts with a low scan rate of 5 mV/s. Inset:the potential required for fixed current density.

Fig. 4. (a) The electrode area-normalized CO stripping curves; Stability test in 0.5 M H₂SO₄ and 1 M CH₃OH solutions: (b) Pt-Ni CNPs (red) and (c) commercial Pt/C (black) with solid line as the first cycle and dashed line as the 1000th cycle; (d) specific activities of two samples before and after 1000 cycles.