金属及金属氧化物助剂对Pt催化氧化甲醇的助催化作用
发布时间：2018-08-18 16:31
【摘要】：直接甲醇燃料电池最常用的阳极催化材料是Pt,从近些年的国内外研究成果来看,Pt的优越催化性能目前还难以被其它普通金属所替代。但是,Pt催化剂存在的问题也显而易见。Pt不但价格昂贵而且容易被甲醇氧化过程产生的类CO中间体所毒化,致使其催化活性和稳定性降低。为了降低催化剂的成本,提高Pt催化剂的催化活性和抗CO中毒能力,本工作采用向Pt催化剂中添加第二种组分/助剂(金属或金属氧化物)的方法,利用助剂与Pt之间的电子效应、协同效应等调变Pt的表面结构性质,进而调变其抗CO中毒能力和催化性能(活性、稳定性)。具体结果如下:1.以石墨烯为载体,通过液相中共还原的方法,制备了一系列具有不同原子比的负载型非合金双金属催化剂PtmAu/RGO(m代表Pt/Au原子比,m=0.5~2.0),考察了不同摩尔比的助剂Au对Pt催化剂在碱性电解质中催化氧化甲醇的助催化作用。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)等技术对催化剂的形貌、晶体结构和电子结构进行了表征,利用电化学测试技术如循环伏安法和计时电流法对催化剂进行了催化性能的测试。研究结果显示,助剂Au的加入可显著提高Pt催化剂在碱性介质中抗CO中毒能力和对甲醇氧化的电催化性能。Pt催化剂上CO中毒程度的降低与催化剂表面CO生成程度降低而不是CO分子的快速脱除有关。系列PtmAu/RGO催化剂的催化性能与催化剂的m值具有火山型关系,在本实验研究范围内,当Pt/Au原子比为1.0时,催化剂具有最高的电催化活性和电化学稳定性。Pt1.0Au/RGO催化剂样品的起始电位最负(-0.78 V),与Pt/RGO(-0.64 V)相比,电位负移140 mV左右;其峰电流最高(0.81 A mg-1Pt+Au),分别是Pt/RGO(0.30 A mg-1Pt+Au)、Pt0.5Au/RGO(0.50 A mg-1Pt+Au)、Pt0.8Au/RGO(0.70 A mg-1Pt+Au)及Pt2.0Au/RGO(0.41 A mg-1Pt+Au)催化剂样品的2.70、1.62、1.15和1.97倍。2.利用简单的化学沉淀法合成了纳米片、珊瑚状及纳米棒状的纳米二氧化锰,并将其作为助剂/载体添加至Pt催化剂中,制备了三种Pt/MnO_2催化剂,分别记作Pt/MnO_2-P、Pt/MnO_2-C和Pt/MnO_2-R,研究了不同形貌的MnO_2载体对Pt催化性能的影响。通过SEM、TEM、XRD等对样品进行了物理化学性质表征,并在酸性电解质中,研究了催化剂对甲醇电催化氧化的性能。结果表明,不同形貌的二氧化锰载体与Pt颗粒间的相互作用不同,对甲醇氧化反应的助催化作用也不一样。在CO剥离伏安曲线中,催化剂Pt/MnO_2-R的起始电位大约为0.34 V,比Pt/MnO_2-C和Pt/MnO_2-P催化剂的起始电位分别负移了近70和100 mV。三种催化剂中,Pt/MnO_2-R催化剂具有最高的本征活性(IA),为30.46 A m-2,分别是Pt/MnO_2-C催化剂(16.21 A m-2)和Pt/MnO_2-P催化剂(10.60 A m-2)的2.31和3.53倍。以二氧化锰纳米棒为载体的Pt/MnO_2-R催化剂样品具有更高的抗CO中毒能力和高的氧化甲醇的催化能力以及稳定性。MnO_2与Pt间的协同作用/双功能机理是提升Pt催化性能的重要因素。3.利用水热法合成了八面体状、纳米球状以及立方体状等不同形貌的二氧化铈,以此作为Pt催化剂的助剂/载体制备了Pt-CeO_2/C催化剂,分别记作Pt-CeO_2/C-O、Pt-CeO_2/C-S300、Pt-CeO_2/C-S400、Pt-CeO_2/C-S500和Pt-CeO_2/C-C,并在碱性电解质中测试了其对甲醇电催化氧化的性能,考察了不同焙烧温度对纳米球状CeO_2助催化性能的影响。研究发现,不同形貌的氧化铈对Pt/C催化剂具有显著不同的助催化作用。在三种不同形貌的CeO_2助剂掺杂的催化剂中,Pt-CeO_2/C-S400催化剂对甲醇的催化氧化表现了更高的催化活性和稳定性,我们分析这可能与氧化铈的粒径相对较小和粗糙的表面结构有关。氧化铈助剂的粗糙表面结构一方面使其具有较大的表面积,增加了助剂和Pt间的相互作用;另一方面,助剂粗糙的表面结构使与其密切接触的Pt的表面配位不饱和原子增多,活性位点增加,因此对甲醇的催化氧化性能增强。
[Abstract]:Pt is the most commonly used anodic catalytic material for direct methanol fuel cells. In recent years, the excellent catalytic performance of Pt can not be replaced by other common metals. However, the problems of Pt catalyst are obvious. Pt is not only expensive but also easy to be produced by the process of methanol oxidation. In order to reduce the cost of catalyst, improve the catalytic activity and anti-CO poisoning ability of Pt catalyst, the method of adding the second component/promoter (metal or metal oxide) to Pt catalyst was adopted. The electronic effect and synergistic effect between Pt and promoter were used to adjust the Pt table. The specific results are as follows: 1. A series of supported non-alloy bimetallic catalysts Pt m Au/RGO (m for Pt/Au atomic ratio, M = 0.5~2.0) with different molar ratios were prepared by liquid-phase CO-reduction using graphene as support. Au promoter was used to catalyze the oxidation of methanol by Pt catalyst in alkaline electrolyte. The morphology, crystal structure and electronic structure of the catalyst were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical measurement techniques such as electrochemical measurement. Cyclic voltammetry and chronoamperometry were used to test the catalytic performance of Pt catalyst. The results showed that the addition of Au could significantly improve the anti-CO poisoning ability of Pt catalyst in alkaline medium and the electrocatalytic performance for methanol oxidation. The catalytic performance of a series of Pt m Au/RGO catalysts has a volcanic relationship with the m value of the catalysts. In this experiment, when the Pt/Au atom ratio is 1.0, the catalysts have the highest electrocatalytic activity and electrochemical stability. The Pt 1.0Au/RGO catalyst sample has the most negative initial potential (-0.78 V) and the Pt/RGO (-0.64 V) phase. Compared with Pt/RGO (0.30 A mg-1 Pt + Au), Pt 0.5 Au / RGO (0.50 A mg-1 Pt + Au), Pt 0.5 Au / RGO (0.50 A mg-1 Pt + Au), Pt 0.8 Au / RGO (0.70 A mg-1 Pt + Au) and Pt 2.0Au / RGO (0.41 A mg-1 Pt + Au) U / RGO (0.41 A mg-1 Pt + Au) were 2.70, 1.70, 1.62, 1.15, 1.15 and 1.97 times and 1.97 times higher than those of Pt / RGO (0.70, 1.70, 1.62, 1.15 and 1.97 times, 1.97 times, respectively) Nanosheets, coral-like and Three kinds of P t/MnO_2 catalysts were prepared by adding nanorod-like manganese dioxide as promoter/carrier into P t catalyst. They were recorded as P t/MnO_2-P, P t/MnO_2-C and P t/MnO_2-R, respectively. The effects of different morphologies of MnO_2 support on the catalytic performance of P T were studied. The samples were characterized by SEM, TEM, XRD and so on. Electrocatalytic oxidation of methanol was studied in acidic electrolytes. The results showed that the interaction between MnO_2 carriers with different morphologies and Pt particles was different, and the catalytic effect on methanol oxidation was different. In CO stripping voltammetry curve, the initial potential of Pt/MnO_2-R was about 0.34 V, which was higher than that of Pt/MnO_2-C and P. Among the three catalysts, P t/MnO_2-R catalyst had the highest intrinsic activity (IA) of 30.46 A m-2, which was 2.31 and 3.53 times of P t/MnO_2-C catalyst (16.21 A m-2) and P t/MnO_2-P catalyst (10.60 A m-2), respectively. The synergistic / bifunctional mechanism between MnO_2 and Pt is an important factor to improve the catalytic performance of Pt. 3. Octahedral, nanospherical and cubic cerium dioxide with different morphologies were synthesized by hydrothermal method and used as Pt catalyst. Pt-CeO_2/C catalysts were prepared as Pt-CeO_2/C-O, Pt-CeO_2/C-S300, Pt-CeO_2/C-S400, Pt-CeO_2/C-S500 and Pt-CeO_2/C-C-C, respectively. The effects of calcination temperature on the catalytic performance of nanospherical CeO_2 were investigated in alkaline electrolytes. C eO_2/C-S400 catalysts exhibited higher catalytic activity and stability for the catalytic oxidation of methanol in three different morphologies of C eO_2-doped catalysts, which may be related to the relatively small particle size and rough surface structure of C eO_2. On the one hand, the rough surface structure of ceria promoter makes it have a larger surface area, which increases the interaction between the promoter and Pt. On the other hand, the rough surface structure of ceria promoter increases the surface coordination unsaturated atoms and active sites of Pt which is in close contact with it, so the catalytic oxidation performance of methanol is enhanced.
【学位授予单位】：曲阜师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM911.4;TQ426
本文编号：2190037
[Abstract]:Pt is the most commonly used anodic catalytic material for direct methanol fuel cells. In recent years, the excellent catalytic performance of Pt can not be replaced by other common metals. However, the problems of Pt catalyst are obvious. Pt is not only expensive but also easy to be produced by the process of methanol oxidation. In order to reduce the cost of catalyst, improve the catalytic activity and anti-CO poisoning ability of Pt catalyst, the method of adding the second component/promoter (metal or metal oxide) to Pt catalyst was adopted. The electronic effect and synergistic effect between Pt and promoter were used to adjust the Pt table. The specific results are as follows: 1. A series of supported non-alloy bimetallic catalysts Pt m Au/RGO (m for Pt/Au atomic ratio, M = 0.5~2.0) with different molar ratios were prepared by liquid-phase CO-reduction using graphene as support. Au promoter was used to catalyze the oxidation of methanol by Pt catalyst in alkaline electrolyte. The morphology, crystal structure and electronic structure of the catalyst were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical measurement techniques such as electrochemical measurement. Cyclic voltammetry and chronoamperometry were used to test the catalytic performance of Pt catalyst. The results showed that the addition of Au could significantly improve the anti-CO poisoning ability of Pt catalyst in alkaline medium and the electrocatalytic performance for methanol oxidation. The catalytic performance of a series of Pt m Au/RGO catalysts has a volcanic relationship with the m value of the catalysts. In this experiment, when the Pt/Au atom ratio is 1.0, the catalysts have the highest electrocatalytic activity and electrochemical stability. The Pt 1.0Au/RGO catalyst sample has the most negative initial potential (-0.78 V) and the Pt/RGO (-0.64 V) phase. Compared with Pt/RGO (0.30 A mg-1 Pt + Au), Pt 0.5 Au / RGO (0.50 A mg-1 Pt + Au), Pt 0.5 Au / RGO (0.50 A mg-1 Pt + Au), Pt 0.8 Au / RGO (0.70 A mg-1 Pt + Au) and Pt 2.0Au / RGO (0.41 A mg-1 Pt + Au) U / RGO (0.41 A mg-1 Pt + Au) were 2.70, 1.70, 1.62, 1.15, 1.15 and 1.97 times and 1.97 times higher than those of Pt / RGO (0.70, 1.70, 1.62, 1.15 and 1.97 times, 1.97 times, respectively) Nanosheets, coral-like and Three kinds of P t/MnO_2 catalysts were prepared by adding nanorod-like manganese dioxide as promoter/carrier into P t catalyst. They were recorded as P t/MnO_2-P, P t/MnO_2-C and P t/MnO_2-R, respectively. The effects of different morphologies of MnO_2 support on the catalytic performance of P T were studied. The samples were characterized by SEM, TEM, XRD and so on. Electrocatalytic oxidation of methanol was studied in acidic electrolytes. The results showed that the interaction between MnO_2 carriers with different morphologies and Pt particles was different, and the catalytic effect on methanol oxidation was different. In CO stripping voltammetry curve, the initial potential of Pt/MnO_2-R was about 0.34 V, which was higher than that of Pt/MnO_2-C and P. Among the three catalysts, P t/MnO_2-R catalyst had the highest intrinsic activity (IA) of 30.46 A m-2, which was 2.31 and 3.53 times of P t/MnO_2-C catalyst (16.21 A m-2) and P t/MnO_2-P catalyst (10.60 A m-2), respectively. The synergistic / bifunctional mechanism between MnO_2 and Pt is an important factor to improve the catalytic performance of Pt. 3. Octahedral, nanospherical and cubic cerium dioxide with different morphologies were synthesized by hydrothermal method and used as Pt catalyst. Pt-CeO_2/C catalysts were prepared as Pt-CeO_2/C-O, Pt-CeO_2/C-S300, Pt-CeO_2/C-S400, Pt-CeO_2/C-S500 and Pt-CeO_2/C-C-C, respectively. The effects of calcination temperature on the catalytic performance of nanospherical CeO_2 were investigated in alkaline electrolytes. C eO_2/C-S400 catalysts exhibited higher catalytic activity and stability for the catalytic oxidation of methanol in three different morphologies of C eO_2-doped catalysts, which may be related to the relatively small particle size and rough surface structure of C eO_2. On the one hand, the rough surface structure of ceria promoter makes it have a larger surface area, which increases the interaction between the promoter and Pt. On the other hand, the rough surface structure of ceria promoter increases the surface coordination unsaturated atoms and active sites of Pt which is in close contact with it, so the catalytic oxidation performance of methanol is enhanced.
【学位授予单位】：曲阜师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM911.4;TQ426
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