The Enhanced Electro-catalytic Performance of Au@Pd Nanoparticles Self-assembled on Fluorine-Modified Multi-walled Carbon Nanotubes for Methanol Oxidation

Abstract

Au@Pd nanoparticles (NPs) with different atomic ratios (4:1, 1:1, 1:4) are synthesized via a simple one-step ultraviolet irradiation method, which are self-assembled on the surface of multi-walled carbon nanotubes modified by –F groups (HF−MWCNTs). The morphology, structure and composition of catalysts are characterized by ultraviolet visible spectra (Uv–Vis), transmission electron microscopy (TEM), high-angle annular dark-filed scanning TEM (HAADF-STEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results display Au@Pd (1:4) NPs have a clear core–shell structure. All of Au@Pd NPs can be uniformly dispersed on the HF−MWCNTs. Methanol oxidation performance of the catalysts is measured by cyclic voltammetry (CV) and chronoamperometry (i−t). Electrochemical tests indicate that Au@Pd/MWCNTs (1:1) catalyst exhibits the excellent electrocatalytic activity and best durability toward methanol oxidation in alkaline media, which is 4.4 times higher than that of the commercial Pd/C. This enhanced electro-catalytic performance could be attributed to uniform dispersion, synergetic effect of core–shell structure, strong metal-support interaction (SMSI effect) between –F functional groups and NPs. The –F groups can interact with Au and Pd atoms to form fluorine complexes, which change the electronic structure of Au and Pd atoms so as to enhance the activity and stability of the Au@Pd/MWCNTs (1:1) catalyst.