| A significant enhancement of electrocatalytic activities for the 6-electron transfer electro-oxidation of methanol has been, and still is, thought as the most challenging problem for the development of direct methanol fuel cells (DMFCs). PtRu and other Pt-based catalysts are extensively investigated and employed presently as anode catalysts for methanol electro-oxidation. Their nature and structure, which are significantly influenced by catalyst preparation or/and treatment procedure, play a key role in the adsorption and electro-oxidation of methanol, and consequently the performances of DMFCs. In this dissertation, three methods were employed to prepare carbon supported Pt-based catalysts. They are the impregnation-reduction of metal precursors by formaldehyde, the oxidative decomposition of sodium sulphites of platinum or/and ruthenium by H2C>2 and the novel method originated in this dissertation, respectively. Ethylene glycol and other glycols were used as reducing agents, solvents and protective agents in the novel catalyst preparation procedure. Carbon supported Pt, PtRu and other catalysts synthesized by different methods were characterized by several technologies such as XRD, XPS, TEM and pulse titration. The parameters such as pH, temperature and so on were also investigated for catalyst preparation. The catalytic activities of these catalysts for methanol electro-oxidation and CO tolerance were compared. It was found that particle sizes, parameter lattice andinteraction between Pt and Ru play important roles in the electro-oxidation of methanol.Generally, particle sizes of Pt-based catalysts prepared by the method of impregnation-reduction of metal precursors by formaldehyde are relatively big and the interaction of Pt and Ru is also relatively weak. The catalyst types prepared by the second method are mainly restricted to Pt, Ru or PtRu. PtRu catalyst synthesized by the novel method, in comparison with its counterparts synthesized by other two methods, has smaller particle sizes and stronger interaction between Pt and Ru, and accordingly has improved electrocatalytic activity for methanol electro-oxidation. Consequently, the single direct methanol fuel cell employing the PtRu catalyst has demonstrated superior performances. The novel method, which is easy to control and operate, can be used to prepare various catalysts with nano-sized particle even in the presence of higher metal loadings. In addition, the particle size of catalysts can be controlled by the addition and sequence of water during this novel method.Titanium oxide, tungsten oxide and molybdena were used to modify Pt and PtRu catalysts in the present work. The modification mode and treatment condition have resulted in important effects on the activities of those catalysts toward methanol electro-oxidation and consequently the performances of single DMFCs with those catalysts. The addition of Tin to PtRu anode catalysts has showed no obvious improvement of DMFCs.It was also found hi this dissertation that the addition of either Ru or Sn to Pt improved its catalytic activity for electro-oxidation of methanol and ethanol, although the reactivities of methanol and ethanol on PtRu or PtSn catalysts were different from each other.As demonstrated in the previous work, PtRu was proved by methanol CV and single DMFC experiments here to be a better anode catalyst for DMFC in comparison to other binary Pt-based catalysts. On the other hand, direct ethanol fuel cells (DEFCs) demonstrated significant performances when PtSn was employed as anode catalyst The optimized atomic ratio of Pt to Sn has been found to vary with the operation temperatures of DEFCs. The direct alcohol fuel cells (DAFCs) employing PtSn as anode, whenever fueled by either methanol or ethanol, have demonstrated the similar cell performances, especially the maximum output power density, even at the relatively low temperature of 90癈. The electro-oxidation mechanisms of methanol and ethanol on PtRu and PtSn have also been primarily studied.
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