發(fā)布時間：2018-04-02 04:40

  本文選題：PtNi納米粒子　切入點：核殼結(jié)構(gòu)　出處：《昆明理工大學(xué)》2017年碩士論文

【摘要】：質(zhì)子交換膜燃料電池是最有可能廣泛應(yīng)用的低污染高效率能源轉(zhuǎn)換裝置。該裝置的成本主要在催化劑上,由于催化劑Pt價格昂貴而且資源稀少,燃料電池的研究發(fā)展依賴于獲得低鉑高活性的催化劑。貴金屬及合金催化劑的活性與其形貌、晶體結(jié)構(gòu)、表面狀態(tài)、顆粒尺寸、負(fù)載分散性等因素有關(guān)。目前已有大量研究對鉑進行合金化處理降低Pt在催化劑中的用量,但這仍不足以將燃料電池的成本降低到期望水平。研究顯示對納米顆粒的形貌調(diào)控可以有效提高催化劑的表面積和高指數(shù)晶面,從而提高電化學(xué)活性。另外,由于催化劑在使用時主要是在表面發(fā)生催化反應(yīng),顆粒內(nèi)部的貴金屬處于無用狀態(tài),核殼結(jié)構(gòu)正是針對這一特點設(shè)計的,可以有效降低鉑的使用量。本研究采用PtNi系列合金作為研究對象來調(diào)控獲得到得高活性的催化劑。研究采用兩步法調(diào)控得到多種形貌PtNi納米顆粒。研究了 Pt/Ni的摩爾比對形貌的影響。研究發(fā)現(xiàn):只在Pt/Ni合金摩爾比為1:1的時候,才會傾向于多枝狀結(jié)構(gòu)的生成;枝狀組織是特定晶體方向生長,只含有鉑元素;加入CTAB和二苯醚都促進得到核殼型結(jié)構(gòu)納米粒子,殼層較為均勻;Pt/Ni為1:3時核殼結(jié)構(gòu)的表層鉑的層厚度在6nM左右。本論文還研究了熱處理溫度、時間、氣氛對PtNi/C催化劑電化學(xué)活性影響。在N2/H2氣氛下400℃/4h熱處理后PtNi獲得最佳的氧還原反應(yīng)活性,半波電位為0.74V,電流密度為4.45mA·cm過長的加熱時間會導(dǎo)致金屬粒子的團聚,過高的熱處理溫度則引起納米PtNi的長大。本論文采用XPS分析不同狀態(tài)下PtNi/C催化劑表面鉑的氧化態(tài)和Pt/Ni比。在N2/H2氣氛下混合氣體中熱處理可以降低表面氧化態(tài)數(shù)量,并且在某些條件下可以完全得到金屬還原態(tài)。表面Pt/Ni比表明PtNi納米粒子發(fā)生了表面偏析,形成了合金核殼結(jié)構(gòu)。
[Abstract]:Proton exchange membrane fuel cell (PEMFC) is the most widely used energy conversion device with low pollution and high efficiency. The development of fuel cells depends on the preparation of catalysts with low platinum and high activity. The activity of noble metal and alloy catalysts and their morphology, crystal structure, surface state, particle size, A lot of research has been done to reduce the amount of Pt in the catalyst by alloying platinum. However, this is not enough to reduce the cost of fuel cells to the desired level. Due to the catalytic reaction on the surface of the catalyst, the precious metal in the particle is useless, so the core-shell structure is designed according to this characteristic. In this study, PtNi series of alloys were used as the research object to control the catalyst with high activity. A variety of PtNi nanoparticles with different morphologies were obtained by two-step method. The structure of Pt/Ni was studied. The effect of molar ratio on morphology. It was found that when the molar ratio of Pt/Ni alloy was 1:1, The dendritic structure grows in a specific crystal direction and contains only platinum elements. The addition of CTAB and diphenyl ether promotes the formation of core-shell structure nanoparticles. The thickness of platinum layer of core-shell structure is about 6nM when the thickness of Pt / Ni is 1:3. The temperature and time of heat treatment are also studied. The effect of atmosphere on the electrochemical activity of PtNi/C catalyst. After heat treatment at 400 鈩，

本文編號：1698857