| This thesis includes two parts of contents: The solubility of elemental sulfur in non-aqueous solution for lithium-sulfur batteries and Pt/Au bi-metallic catalyst toward methanol oxidation electro-catalytic activity.Part I: As a promising candidate for next generation rechargeable Li batteries, the rechargeable Li-S battery has advantages of environment friendly, rich sources and high energy density. For the detailed mechanism of the redox reactions in Li-S battery, it is widely accepted that polysulfide anions play an important role, and that elemental sulfur is the active material and the product of reaction process in a Li-S battery. But, no research work on quantitative analysis of elemental sulfur in Li-S battery has been reported. We study the solubility of element sulfur in non-aqueous for lithium-sulfur batteries in this thesis, the followings are the major research contents and results:(1) By using high performance liquid chromatography with a UV detector, the solubility of S in 12 different pure solvents and in 22 different electrolytes was determined. And the three factors affecting S solubility, such as the Lewis basicity, the polarity of solvents and the salt concentration in the electrolytes, are studied. It is found that the solubility of S in non-polar solvent is higher than that in polar solvent, the sulfur is more soluble in the solvent with higher Lewis basic solution, and with the concentration of the salts higher the solubility is decreased.(2) By the proposed HPLC/UV method, determined the S content in the electrolyte recovered from a discharged Li-S battery and the simulated electrolyte. The results show that the feasibility of the method to the online analysis for a Li-S battery is demonstrated and the S was found super-saturated in the electrolyte recovered from a discharged Li-S battery which is due to the decomposition of polysulfide species: polysulfide species with long chain length are unstable and will gradually decompose into polysulfide species with shorter chain length and elemental sulfur.Part II: Direct methanol fuel cell(DMFC) is considered as one of advanced energy devices, which can meet the increasing demands of efficient and environmental-friend energy system. One of the key issues in the study of DMFC is finding a high activity catalyst for electro-oxidation of methanol. In order to improve the Pt-based activity and utilization of catalysts, this thesis research coverage-dependent electro-catalytic activity of Pt/Au bi-metallic catalyst toward methanol oxidation. And the following list the study contents and outcomes:(1) Adopt under potential deposition and redox-replacement reaction prepare different coverage Pt/Au bi-metallic catalyst for methanol oxidation. And study the Pt/Au bi-metallic eletro-catalytic activity toward methanol. It is found that when the coverage is 0.6 of Pt on Au substrate, the Pt/Au bi-metallic show the best catalytic activity which have smaller particle size, good dispersed and higher efficiency.(2) The ratio of the current density between the forward anodic peak and the reverse anodic peak(If/Ib) can be used to evaluate the poison tolerance of the Pt-based catalyst. Compare Pt/Au bi-metallic and Pt catalyst, the results show that Pt/Au bi-metallic catalyst has higher resistance to CO, and the reason is “bifunctiional mechanism” of Au which promote Pt catalyst. |
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