采用解离的氢原子作为还原剂制备高氧还原电催化性能的Pd_核@Pt_壳纳米结构（英文）

发布时间：2018-04-04 09:06

本文选题：Pd核@Pt壳　切入点：解离氢　出处：《催化学报》2017年07期

【摘要】：质子交换膜燃料电池(PEMFC)作为一种清洁、高效的能源转化装置,已经备受学术界与产业界的关注.然而,高活性、高稳定性与低成本的铂基阴极氧还原(ORR)电催化剂的缺乏,严重限制PEMFC的大规模商业化应用.为提高贵金属铂的电催化性能,核壳纳米结构的研究受到广范关注.然而,核壳纳米结构的制备过程通常需要采用有机前驱体、表面活性剂与较高的反应温度,导致大多核壳结构制备方法的大规模应用受到限制.我们在室温下无表面活性剂与高沸点溶剂的参与下,通过钯表面吸附的解离的氢原子来还原K_2PtCl_4,得到Pd_核@Pt_壳纳米结构.通过改变加入K_2PtCl_4的量,可以成功控制壳的厚度;通过透射电子显微镜(TEM)观察得知,我们制备了铂壳厚度分别为0.45,0.75,0.9 nm的核壳结构.Pd_核@Pt_壳纳米结构的良好的纳米晶体结构与外延生长模式,通过高分辨透射电子显微镜(HRTEM)与能量色散谱仪(EDS)得到证实.同时,所制备Pd_核@Pt_壳样品的核壳结构通过高角环形暗场-扫描透射-元素分布(HAADF-STEM-EDX)表征方法,得到证实.X射线粉末衍射(XRD)表征证实,样品Pd_核@Pt_壳并无单独的Pd或Pt衍射峰出现,而是表现出良好的同种晶相结构;相对于单质Pt,样品中Pd核的存在导致Pd_核@Pt_壳核壳结构表现出一定程度的晶格紧缩.X射线光电子能谱(XPS)表明,钯核的存在导致铂壳的电子结合能增大,并且当铂壳厚度增大到一定程度后,核壳结构引起的电子效应维持不变.通过XPS分峰拟合可知,Pd_核@Pt_壳结构中零价态的铂含量均在80%以上,并且零价态的铂含量随着铂壳层厚度的增大而增大.采用电感耦合等离子体(ICP)与XPS,发现铂的表面富集现象,并且铂表面富集现象随着铂壳层厚度的增大而增大.在半电池中,经过循环伏安扫描活化,Pd_核@Pt_壳表现出明显的铂的氢吸附与脱附特征峰,再次证明了铂壳层的成功包覆.Pd_核@Pt_壳纳米颗粒表现出优于Pt/C(JM)的面积比活性、质量比活性及电化学稳定性.核壳结构的良好的ORR电催化性能,来源于催化剂表面含氧物种吸附强度的减弱;上述现象归因于钯核与铂壳之间的电子效应与晶格应力效应.此处简易、清洁的核壳结构制备方法也可以用来在温和条件下制备Ni_核@Pt_壳等核壳结构.
[Abstract]:Proton exchange membrane fuel cell (PEMFC), as a clean and efficient energy conversion device, has attracted the attention of academia and industry.However, the lack of high activity, high stability and low cost platinum based cathodic oxygen reduction (ORR) electrocatalysts seriously limits the large-scale commercial application of PEMFC.In order to improve the electrocatalytic performance of noble metal platinum, the study of core-shell nanostructures has attracted wide attention.However, the preparation process of core-shell nanostructures usually requires organic precursors, surfactant and higher reaction temperature, which limits the large-scale application of most core-shell structures.We have reduced K _ 2PtCl _ 4 by dissociated hydrogen atoms adsorbed on palladium surface with the participation of non-surfactant and high boiling solvent at room temperature.The thickness of the shell can be successfully controlled by changing the amount of K_2PtCl_4.We have prepared a core-shell structure with thickness of 0.45 ~ 0.75 ~ (0.9) nm and a good epitaxial growth mode of the nanocrystalline Pt _ shell structure. The results are confirmed by high resolution transmission electron microscopy (HRTEM) and energy dispersive spectrometer (EDS). The crystal structure and epitaxial growth pattern of Pt _ shell nanocrystalline have been confirmed by high resolution transmission electron microscopy (HRTEM) and energy dispersive spectrometer (EDS).At the same time, the core-shell structure of the prepared Pd- @ PTT _ shell sample was characterized by high angle ring dark field, scanning transmission and element distribution, and confirmed by X ray powder diffraction (XRD), and the structure of the sample was characterized by HAADF-STEM-EDX.There are no single PD or Pt diffraction peaks in the PD _ nucleus and Pt shell, but a good allocrystalline structure.The presence of PD nuclei in the samples leads to a certain degree of lattice contraction in the structure of the Pt- shell, which indicates that the presence of the palladium core leads to the increase of the electron binding energy of the platinum shell.When the thickness of the platinum shell increases to a certain extent, the electron effect caused by the core-shell structure remains unchanged.The results of XPS peak fitting show that the platinum content of the zero valence state in the structure of Pt- shell is above 80%, and the platinum content of the zero valence state increases with the increase of the thickness of the platinum shell.By using inductively coupled plasma ICP (ICP) and XPS, it is found that the surface enrichment of platinum increases with the increase of the thickness of platinum shell.After cyclic voltammetry (CV) activation, the Pt_ shell exhibited obvious hydrogen adsorption and desorption characteristic peaks of platinum. It was proved again that the successful coating of the platinum shell. The Pt_ shell nanoparticles exhibited a better area specific activity than that of the Pt- / Con JM.Mass specific activity and electrochemical stability.The good ORR electrocatalytic performance of core-shell structure originates from the decrease of adsorption intensity of oxygen-containing species on the surface of the catalyst, which is attributed to the electronic effect and lattice stress effect between the palladium core and the platinum shell.The simple and clean method for preparing core-shell structures can also be used to prepare core-shell structures such as Ni_ core @ Pt_ shell under mild conditions.
【作者单位】：中国科学院大连化学物理研究所;中国科学院大学;华中农业大学理学院化学系;
【基金】：supported by the National Major Research Project(2016YFB0101208) the National Natural Science Foundation of China(21576257) the Natural Science Foundation-Liaoning United Fund(U1508202)~~
【分类号】：O643.36;TM911.4

【相似文献】