| Summary: | 碩士 === 國立臺南大學 === 材料科學系碩士班 === 95 === The direct methanol fuel cell (DMFC) is suffered from methanol tolerant on cathode of oxygen reduction. The properties of oxygen reduction at Pt electrode were resisted by absorbed methanol on Pt surface. This study is focused on oxygen reduction in phosphate solution with copper complexes to reduce the methanol tolerant on oxygen reduction at Pt electrode.
This study investigated the copper complexes containing nitrogen ligand ([Cu(bpy)2]2+, bpy is 2,2-bipyridine) was dissolved in phosphate buffer solution, then the electrocatalytic reduction of oxygen at glassy carbon and Pt electrodes in phosphate solution with/without copper complexes and with/without methanol were investigated. Cyclic voltammetry (CV) of glassy carbon electrode (working electrode) was processed in the range between 0.5 ~－0.4 V vs. Ag/ AgCl reference electrode in different copper complexes concentration and pH value. The 5×10-4M [Cu(bpy)2]2+ was the better catalytic effect on methanol-resistant oxygen-reduction in acidic phosphate solution. In the working electrode of platinum electrode, the adsorption concentrations of [Cu(bpy)2]2+ were shown with platinum electrode in acidic and alkaline buffer solution were 5×10-4M and 2.2×10-3M, respectively. The oxygen-reduction at Pt electrode were inhibited by [Cu(bpy)2]2+, especially in acidic buffer solution. The oxygen reduction electrocatalytic effect of Pt was decreased obviously in phosphate solution with methanol, but it was protected effectively from the 10 % methanol phosphate solution with [Cu(bpy)2]2+ in various pH ranges. In acidic phosphate solutions with methanol, it was useful for the methanol-resistant oxygen-reduction when [Cu(bpy)2]2+ was adsorbed. In alkaline phosphate solutions with methanol, it is better effect on methanol-resistant oxygen reduction with [Cu(bpy)2]2+, which is due to the un-adsorbed [Cu(bpy)2]2+ maintaining the properties of oxygen reduction of Pt electrode and restraining the methanol tolerant on Pt surface. The oxygen reduction at adsorbed [Cu(bpy)2]2+ Pt electrode is mainly thought two electron pathway. Therefore, we use the [Cu(phen)2]2+ to substitute [Cu(bpy)2]2+ to investigate the different complexes effects for oxygen reduction. The [Cu(phen)2]2+ have good protected Pt surface from the methanol tolerant.
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