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摘要本文中，通过微波化学法制备不同外径碳载钯基催化剂，并使用XRD对其进行表征，使用循环伏安法和线性伏安法对其机理和动力学展开研究。结果表明：MH3对钯的吸附性能最佳且电化学测试中峰值电流最高。KOH和乙醇浓度均对乙醇氧化反应起影响作用。氢氧化钾的反应级数为0.7，乙醇的反应级数为0.2。阳极的转化因子α为0.11。当KOH和乙醇浓度为1M+1M时，乙醇的扩散因子为1.23×10-4cm2s-1。Pd/MH3催化剂在碱性环境下的总速率计算方程式由计算得出j=5.6×10-5C0.7EtOHC0.2KOHexp(0.33Fη/RT)。催化剂对游离的乙醇吸附的速度很快，且催化剂表面对乙醇中间氧化物的脱附是主要的反应控诉步骤。Pd/ MHx和Pd/ XC催化剂的Tafel曲线斜率在低电位出为170mV/ dec左右，且OH-的吸附过程符合Temkin-type等温曲线。而在高电位，其Tafel斜率增至250mV/ dec。这种变化表明了当电位达到高电位处，影响乙醇氧化动力学的因素不仅是OH-的吸附，还与Pd电极上非活性氧化层的形成有关。9019
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关键字： 碳载Pd基催化剂；碱性；直接乙醇燃料电池；乙醇氧化反应；机理研究；动力学研究
Abstract
In this work, the Pd nanoparticle catalyst using different OD multi-wall nanotube and vulcan-XC as support was prepared by microwave chemistry treatment. The characterization of the catalyst was studied using XRD, and the kinetics of ethanol electrooxidantion and the mechanism of ethanol oxidantion reaction on palladium electrode was studied using the cyclic voltammetry and linear sweep voltammetry method. The result shows that the MH3 absorption of palladium is the best and the peak current of Pd/MH3 is the highest. The concentration of KOH and ethanol affects the ethaol oxidantion. The reaction order for KOH and ethanol is 0.2 and 0.7. The anodic transfer coefficient is 0.11. The defusion coefficient is caculated as 1.23×10-4cm2s-1 when the concentration of KOH and ethanol is both 1M. The overall rate equation of Pd/MH3 is given as j=5.6×10-5C0.2EtOHC0.7KOHexp(0.33Fη/RT) in the alkaline media. The study of mechanism shows that the dissociative adorption of ethanol was found to proceed rather quicly and the rate-determining step was the removel of the adsorbed ethoxi by the adsorbed OH-. The tafel slope of Pd/MHx and Pd/XC is 170mV/dec around in the low potential, and the adsorption of OH- follows the Temkin-isotherm. At the high potential, the Tafel slope increases to 250mV/dec. The change indicated that the kinetics is not only affect by the adsorption of OH- but the formation of inactive ethoxi layer on Pd electrode.
Keywords: caborn palladium catalyst; alkaline media; DEFCs; ethanol oxidation reaction; mechanism; kinetics.
目 录
1. 引言 1
1.1. 燃料电池综述 1
1.1.1. Pd基催化剂的现状 1
1.1.2. 碳负载型Pd 催化剂 2
1.1.3. 以CNTs为载体的阳极催化剂的研究 2
1.1.4. 碱性环境的乙醇燃料电池 3
1.2. 催化剂制备方案设计 3
1.2.1. 化学还原法 3
1.2.2. 改进化学还原法 3
1.2.3. 溶剂热法 4
1.2.4. 其他方法 4
1.2.5. 微波化学法 4
2. 实验部分 5
2.1. 实验样品与仪器 5
2.1.1. 试剂与气体 5
2.1.2. 仪器与设备 5
2.2. 实验步骤 5
2.2.1. 催化剂的制备 5
2.2.2. 表征 6
3. 实验结果与分析 8
3.1. BET孔径分布测试 8
3.2. XRD 10
3.3. 电化学 12
3.3.1. 循环伏安测试 12