本文選題：Pt-Co合金納米催化劑　切入點：表面偏析　出處：《昆明理工大學》2017年碩士論文　論文類型：學位論文

【摘要】：燃料電池是最受關注、推崇的新型綠色清潔能源之一。燃料電池由于工作運行溫度低、啟動速度快、功率密度高和環(huán)境污染低,被看做新一代最環(huán)保的綠色動力能源轉換裝置。但由于Pt資源的稀缺,使得Pt基催化劑的成本居高不下,制約了質(zhì)子交換膜燃料的發(fā)展和推廣,進而使燃料電池不能進行大規(guī)模商業(yè)化應用。在燃料電池商業(yè)化過程中,提高催化劑的催化性能和降低Pt的用量是最為關鍵的問題。質(zhì)子交換膜燃料電池(PEMFC)陰極氧還原反應(ORR)的反應速率緩慢,而直接甲醇燃料電池陽極Pt催化劑甲醇氧化(MOR)活性低且易CO中毒。因此,提高Pt的利用率、降低Pt的使用量,研制新型高性能、低成本的Pt催化劑對推動低溫燃料電池的發(fā)展具有重要意義。為降低Pt的用量,人們主要通過Pt與過渡金屬M(M=Fe、Co、Cu、Ni等)合金化來制備尺寸小、分布均勻的Pt基合金納米催化劑來降低成本及提高催化性能。此外,可利用Pt基合金在還原氣氛中熱處理會發(fā)生吸附誘導Pt表面偏析來調(diào)控Pt基合金納米催化劑的表面成分。本文采用乙酰丙酮鉑和乙酸鈷為前驅體,通過化學熱還原的方法,合成出Pt、Co 原子比分別為 3:1、1:1、1:3 的 Pt3Co/C、PtCo/C、PtCo3/C 催化劑,然后將碳載Pt3Co/C、PtCo/C、PtCo3/C催化劑在還原氣氛中400℃分別保溫2h、4h、6h來調(diào)控Pt-Co合金納米催化劑的表面成分。運用TEM、XRD、XPS等分析手段研究Pt-Co合金納米粒子的尺寸、形貌、化學組成及化學價態(tài),并用電化學方法測試Pt-Co合金納米催化劑的催化性能(ORR、MOR活性)。研究結果如下:(1)利用化學熱還原法合成出的不同Pt、Co原子比例(3:1、1:1、1:3)的Pt-Co納米合金催化劑,分散均勻、平均尺寸小于3nm;(2)通過XRD分析碳載Pt-Co合金納米催化劑,證實Co已溶入Pt的晶格形成Pt-Co合金,表明我們利用化學熱還原法,合成出碳載Pt-Co合金納米催化劑。電化學測試表明,合成出的碳載Pt-Co合金納米催化劑對ORR和MOR都有較高活性。其中,PtCo3/C的ORR活性最好,而Pt3Co/C的MOR活性最好;(3)在還原氣氛中400℃熱處理獲得的碳載PtCo納米合金催化劑,經(jīng)TEM分析表明Pt-Co合金納米粒子的尺寸基本沒有明顯長大。ORR活性測試表明,隨著保溫時間增加,ORR活性明顯提高,但保溫時間過長會導致ORR活性下降;MOR活性測試表明,隨著保溫時間增加,MOR活性明顯提高,但保溫時間過長會導致MOR活性下降,其中保溫2h的MOR活性最好,而PtCo3/C是MOR性能最好的催化劑。
[Abstract]:Fuel cells are one of the most focused and respected green clean energy sources. Fuel cells have low operating temperature, high start-up speed, high power density and low environmental pollution. It is regarded as the new generation of green power conversion device. However, due to the scarcity of Pt resources, the cost of Pt-based catalyst is high, which restricts the development and promotion of proton exchange membrane fuel. So that fuel cells can't be commercialized on a large scale. The most important problem is to improve the catalytic performance of the catalyst and reduce the amount of Pt. The reaction rate of PEMFC cathodic oxygen reduction reaction (ORR) is slow. However, the anode Pt catalyst for methanol oxidation of direct methanol fuel cell has low activity and is prone to CO poisoning. Therefore, it is necessary to improve the utilization of Pt, reduce the amount of Pt used, and develop a new type of high performance. Low-cost Pt catalysts are of great significance in promoting the development of low-temperature fuel cells. Uniformly distributed Pt-base alloy nanocatalysts to reduce cost and improve catalytic performance. The surface composition of Pt-base alloy nanocatalysts can be regulated by adsorption-induced Pt surface segregation during heat treatment in reducing atmosphere. In this paper, acetylacetone platinum and cobalt acetate are used as precursors, and the method of chemical thermal reduction is used. The Pt3Co- / PtCo- / CtCo- / PtCo3 / C catalyst with a ratio of 3: 1 / 1: 1: 1: 3 has been synthesized. Then carbon supported Pt3CoP / PtCoP / PtCo3 / C catalyst was kept at 400 鈩，

本文編號：1568234