本文選題：Pd核@Pt殼　切入點(diǎn)：解離氫　出處：《催化學(xué)報(bào)》2017年07期

【摘要】：質(zhì)子交換膜燃料電池(PEMFC)作為一種清潔、高效的能源轉(zhuǎn)化裝置,已經(jīng)備受學(xué)術(shù)界與產(chǎn)業(yè)界的關(guān)注.然而,高活性、高穩(wěn)定性與低成本的鉑基陰極氧還原(ORR)電催化劑的缺乏,嚴(yán)重限制PEMFC的大規(guī)模商業(yè)化應(yīng)用.為提高貴金屬鉑的電催化性能,核殼納米結(jié)構(gòu)的研究受到廣范關(guān)注.然而,核殼納米結(jié)構(gòu)的制備過程通常需要采用有機(jī)前驅(qū)體、表面活性劑與較高的反應(yīng)溫度,導(dǎo)致大多核殼結(jié)構(gòu)制備方法的大規(guī)模應(yīng)用受到限制.我們?cè)谑覝叵聼o表面活性劑與高沸點(diǎn)溶劑的參與下,通過鈀表面吸附的解離的氫原子來還原K_2PtCl_4,得到Pd_核@Pt_殼納米結(jié)構(gòu).通過改變加入K_2PtCl_4的量,可以成功控制殼的厚度;通過透射電子顯微鏡(TEM)觀察得知,我們制備了鉑殼厚度分別為0.45,0.75,0.9 nm的核殼結(jié)構(gòu).Pd_核@Pt_殼納米結(jié)構(gòu)的良好的納米晶體結(jié)構(gòu)與外延生長(zhǎng)模式,通過高分辨透射電子顯微鏡(HRTEM)與能量色散譜儀(EDS)得到證實(shí).同時(shí),所制備Pd_核@Pt_殼樣品的核殼結(jié)構(gòu)通過高角環(huán)形暗場(chǎng)-掃描透射-元素分布(HAADF-STEM-EDX)表征方法,得到證實(shí).X射線粉末衍射(XRD)表征證實(shí),樣品Pd_核@Pt_殼并無單獨(dú)的Pd或Pt衍射峰出現(xiàn),而是表現(xiàn)出良好的同種晶相結(jié)構(gòu);相對(duì)于單質(zhì)Pt,樣品中Pd核的存在導(dǎo)致Pd_核@Pt_殼核殼結(jié)構(gòu)表現(xiàn)出一定程度的晶格緊縮.X射線光電子能譜(XPS)表明,鈀核的存在導(dǎo)致鉑殼的電子結(jié)合能增大,并且當(dāng)鉑殼厚度增大到一定程度后,核殼結(jié)構(gòu)引起的電子效應(yīng)維持不變.通過XPS分峰擬合可知,Pd_核@Pt_殼結(jié)構(gòu)中零價(jià)態(tài)的鉑含量均在80%以上,并且零價(jià)態(tài)的鉑含量隨著鉑殼層厚度的增大而增大.采用電感耦合等離子體(ICP)與XPS,發(fā)現(xiàn)鉑的表面富集現(xiàn)象,并且鉑表面富集現(xiàn)象隨著鉑殼層厚度的增大而增大.在半電池中,經(jīng)過循環(huán)伏安掃描活化,Pd_核@Pt_殼表現(xiàn)出明顯的鉑的氫吸附與脫附特征峰,再次證明了鉑殼層的成功包覆.Pd_核@Pt_殼納米顆粒表現(xiàn)出優(yōu)于Pt/C(JM)的面積比活性、質(zhì)量比活性及電化學(xué)穩(wěn)定性.核殼結(jié)構(gòu)的良好的ORR電催化性能,來源于催化劑表面含氧物種吸附強(qiáng)度的減弱;上述現(xiàn)象歸因于鈀核與鉑殼之間的電子效應(yīng)與晶格應(yīng)力效應(yīng).此處簡(jiǎn)易、清潔的核殼結(jié)構(gòu)制備方法也可以用來在溫和條件下制備Ni_核@Pt_殼等核殼結(jié)構(gòu).
[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.
【作者單位】： 中國(guó)科學(xué)院大連化學(xué)物理研究所;中國(guó)科學(xué)院大學(xué);華中農(nóng)業(yè)大學(xué)理學(xué)院化學(xué)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)~~
【分類號(hào)】：O643.36;TM911.4

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