【作者】 冯德香；

【导师】 褚道葆；

【作者基本信息】 安徽师范大学 ， 有机化学， 2005， 硕士

【摘要】 最近发展起来的直接甲醇燃料电池（DMFC）由于其燃料来源丰富、价格便宜、运输和储存较安全的优点而受到广泛重视。然而,阳极催化剂的低催化活性、甲醇氧化中间产物羰基对阳极催化剂的毒化,致使DMFC的实际应用发展速度一直没有预期的快,因此,研究和发展高催化活性、抗中毒能力强的新型催化剂已成为当前DMFC发展的关键技术。本文采用电合成前驱体Ti（OEt）₄直接水解法和电化学扫描电沉积法制备活性高的nanoTiO₂-CNT-Pt、nanoTiO₂-CNT-PtNi和nanoTiO₂-CNT-PtNiNd多元复合纳米催化剂,并利用XRD和TEM技术表征了催化剂粒子大小、结晶度,采用电化学方法评价了多元复合纳米催化剂对甲醇的电催化活性和稳定性。主要研究结果如下: 第一部分:采用循环伏安（CV）共沉积方法制备出高分散的Ti/nanoTiO₂-CNT-Pt催化剂,利用循环伏安电化学方法评价了该电极催化剂对甲醇的电催化活性和稳定性。XRD和TEM技术表征了修饰在nanoTiO₂-CNT膜上的Pt催化剂颗粒的大小、分散状态。XRD和TEM结果显示,Pt纳米粒子高度分散nanoTiO₂-CNT膜表面,催化剂颗粒粒径较小,降低了团聚,使催化剂有相当高的表面积。电化学测试结果表明nanoTiO₂-CNT-Pt催化剂对甲醇的电催化氧化呈现出很好的活性和稳定性,这主要是由于Pt和nanoTiO₂、CNT之间的协同催化作用使甲醇氧化中间产物的毒化物种易氧化成最终产物的结果,其次是用这种方法制得的催化剂中各组分具有较小的粒径,且分散较好。 第二部分:在10 mM/L H₂PtCl₆、30 mM/L NiCl₂混合溶液中,在扫描范围-0.80V-0.05V,扫描速度50 mV,电化学共沉积制备Ti/nanoTiO₂-CNT-PtNi电极。通过计时电流图中的电流衰减情况和CV 实验结果比较可得出,该电极比同样方法制备的Ti/nanoTiO₂-CNT-Pt电极甲醇氧化峰电位负移约20 mV,单位质量铂对应甲醇氧化峰电流增加了40～60%。其中Pt和Ni原子比为1:3时性能最优,Ti/nanoTiO₂-CNT-PtNi催化剂对甲醇氧化高的电催化活性可以用双功能机理得到解释,金属Pt起到吸附解离甲醇的作用,更多还原

【Abstract】 Recently developed direct methanol fuel cell has been received widespread attention due to the abundant source、 the low price、 the safety of the storage and transportation of the fuel. Nevertheless, the step toward the practical application has not been developed as fast as had been expected. It is key techniques in DMFC to find with the complex catalysts have good electrocatalytic activity and resistant ability to poisoning for the methanol oxidation. The good electrocatalytic active nanoTiO2-CNT-Pt、 nanoTiO2-CNT-PtNi、nanoTiO2-CNT-PtNiNd complex nanostructural catalysts were prepared by the precursor Ti(OEt)4 directly hydrolyzed and cyclic voltammetry electrodepositing method, using XRD and TEM techniques, the size and crystallinity of the catalysts. The electrocatalytic activitics and stability for the methanol oxidation were evaluated with the electrochemical techniques, The main result obtained are as follows:Part one: electrochemical deposition method by cyclic voltammetry(CV) to prepare the Ti/nanoTiO2-CNT-Pt, and the composite electrodes were characterized to study those composition and those electrochemical behavior by CV, The electrocatalytic activitics and stability for the methanol oxidation and the electrocatalystic activition of the electrodes for the oxygen reduction were evaluated with the electrochemical techniques. Using the XRD and TEM techniques . TEM results and XRD results indicated that the Pt microparticles were uniformly high dispersed on nanoTiO2-CNT films, nanoTiO2-CNT decreased catalytic agglomeration rate, and these made the Ti/nanoTiO2-CNT samples higher specific surface area of Pt. the size and the disperion degree of the catalyst particles were studied in presence or absence of nanoTiO2-CNT films in the catalyst. It was found that methanol oxidation was catalyzed on the nanoTiO2-CNT modified Pt by lowering methanol oxidation potential and promoting methanol oxidation current. The catalysts show high performance and good stability for theelectro-oxidation , which is the results of the co-operation effect of Pt and TiO2 ■. CNT particles and Pt and TiO2 particles have small particle diameters and can disperse.Part two: The Ti/nanoTiO2-CNT-PtNi composite electrode was prepared by cycling the potential between -0.8V and -0.05V versus SCE, at a scan rate of 50mV/s, in a solution of lOmM/L in H2PtCl6^ 30 mM/L in NiCl2. Chronoamperometry response and CV results for the Ti/nanoTiO2-CNT-PtNi composite electrode, compared with the Ti/nanoTiO2-CNT-Pt electrode, methanol oxidation took place on the nanoTiO2-CNT modified PtNi at the potential 20mV more negatively than on the nanoTiO2-CNT modified Pt, the steady mass specitic oxidation current of methanol on this modified platinum was 40%-60%. Pt: Ni atomic ratio of 1: 3 showed the highest electrocatalytic activity for methanol oxidation. The enhanced catalytic activity of nanoTiO2-CNT-Pt-Ni catalysts for methanol oxidation can be rationalized by a bifunctional mechanism in which Pt is responsible for dehydrogenation of methanol and metallic Ni for the dehydrogenation of water. It was also found that an electronic effect in the electrocatalysis is associated with the amount of Ni atoms in the catalysts.Part three: we putted Ti/nanoTiO2-CNT-PtNi composite electrode into a HC1 solution of 6.0 ml/L Nd3+ for half an hour, Chronoamperometry response and CV results for the Nd3+ modified Ti/nanoTiO2-CNT-PtNi composite electrode, showed slightly a better CO tolerant perfomance, Presence of Nd3+ in the Ti/nanoTiO2-CNT-PtNi composite electrode by electrochemical codeposition made peak potential of methanol oxidation a further negative shift of about 20mV and bigger peak current. The experimentas results show that Nd3+ has a high catalysis for electrocatalytic oxidation of methanol in electrolyte. A possible synthesis mechansm was proposed.The thesis studied preparation of some new nanostructural electrocatalytic electrodes with higher electro-catalytic activity and更多还原