核壳型Ru@Pt在甲醇电催化氧化反应中的电子效应研究

Electronic Effect of Core-Shell Ru@Pt Nano-Particle Catalysts in Methanol Electro-Oxidation

通过两步化学还原法合成了不同壳层厚度的核壳型Ru@Pt纳米粒子,采用X射线衍射光谱（XRD）、X射线光电子能谱（XPS）、透射电子显微镜（TEM）和X射线能谱（EDS）等手段对粒子的晶体结构、表面元素、微观形貌及组成进行物理表征;应用循环伏安法和交流阻抗法对电催化氧化甲醇的催化性能进行电化学测试。结果显示,制备的Ru@Pt纳米粒子直径约为2~4nm,为核壳型结构;不同Ru@Pt样品氢的脱附峰随n（Pt）∶n（Ru）比值的增大呈现先增加后减小的＂山形＂趋势,其中n（Pt）∶n（Ru）=0.5∶1样品的脱附峰值最高;由于核层Ru对Pt壳层产生电子效应,使核壳型纳米粒子电化学活性面积增大,且电子效应越强活性比表面积越大;随着纳米粒子电子效应的增强,其比质量活性增大,甲醇反应过程的阻抗降低。

Thin shell Ru@Pt core-shell nanoparticles with different thicknesses were synthe- sized through two-step chemical reduction. X-ray diffraction （XRD）, X-ray photoelectron spec- troscopy （XPS）, transmission electron microscopy （TEM） and X-ray energy dispersive spectome- try （EDS） were employed to characterize particle crystal structure, surface elements, microstruc- ture and composition of as-prepared Ru@Pt core-shell nanoparticles; the electrochemical catalytic performance of catalytic oxidation of methanol was tested by cyclic voltarnmetry, AC impedance and chronoamperometry. Results show that, the prepared Ru@Pt core-shell nanoparticles were uniform spheres with average diameters around 2-4 nm. Among Ru@Pt nanoparticles with dif- ferent n（Pt） ： n（Ru） values, hydrogen stripping peaks increased and then decreased as ＂volcano＂ with the increase of content of Pt, the nanoparticle with n（Pt） ： n（Ru）=0.5：1 had the highest peak. The electrochemical active area of core-shell nanoparticles was improved by the electronic effect of Ru core on Pt shell, and the stronger the electronic effect was, the bigger the specific surface area was. With the augmentation of the electronic effect, specific mass activity of nanop-articles increaced, and the reaction resistance of methanol was reduced.