A successful approach to prepare the Pd-Ni nanowire arrays electrode without carbon supports was reported. The morphology and crystallinity of nanowire were characterized by transmission electron microscopy, selected-area electron diffraction （SAED）, X-ray diffrac- tion （XRD）, and X-ray photoelectron spectroscopy （XPS） analyses, respectively. The results show that the diameters of the nanowire are in the range of 65-75 nm, and the polycrystalline binary solid solution alloy is formed in the Pd-Ni nanowire. Cyclic voltammograms, chronoampero- grams, and electrochemical impedance spectroscopy dem- onstrate that the Pd-Ni nanowire arrays electrodes show excellent electrocatalytic performance for methanol oxi- dation in alkaline media. The catalytic activity of Pd-Ni nanowire arrays electrode is ,,~ 1.39 times higher than that of the Pd nanowire arrays electrode and ,,~2.28 times higher than that of the commercial Pd/C catalyst. This is mostly owing to the transfer of electron density from Ni to Pd. These results indicate that Pd-Ni nanowire arrays electrode is very promising in an alkaline direct methanol fuel cell.
A successful approach to assemble Au core Pd shell （Au@Pd） nanoparticles on the surface of multi-walled carbon nanotubes functionalized by methylene blue （MB） （Au@Pd/fuv-MWCNTs） was reported. In this method, MWCNTs were functionalized under ultraviolet irradiation. UV-Vis analysis and high-angle annular dark-field trans- mission electron microscope （HAADF-TEM） image prove that core-shell structure of Au@Pd nanoparticles forms. TEM results indicate that Au@Pd nanoparticles （ - 5.2 nm） are well-dispersed on the surface of fuv-MWCNTs. X-ray photoelectron spectroscopy （XPS） reveals that ultraviolet irradiation can promote the interaction between Au@Pd nanoparticles and the functional groups on the surface of MWCNTs. Cyclic voltammograms （CV）, chronoampero- grams （CA）, and electrochemical impedance spectroscopy （EIS） results demonstrate that the Au@Pd/fuv-MWCNTs catalysts show excellent electrocatalytic performance for methanol oxidation in alkaline media. The catalytic activity of the Au@Pd/fuv-MWCNTs is ~ 2 times higher than that of the commercial Pd/C catalysts. This is mostly attributed to that ultraviolet irradiation can make the moieties of MB provide a uniform surface with active and anchoring sites, and improves the functional effect of MB on the surface of MWCNTs. Especially, ultraviolet irradiation modifies electronic structure of Pd and is beneficial for the enhance- ment of catalytic activity.
Ming-Li XuXi-Kun YangYing-Jie ZhangShu-Biao XiaPeng DongGuo-Tao Yang
