利用PdO奈米片狀結構做為Pt觸媒擔體─直接甲醇燃料電池陽極觸媒之應用

Abstract

本研究以改良直接甲醇燃料電池(DMFC)電極觸媒為主要的課題，利用Sputter濺鍍氧化鈀薄膜，再利用脈衝電鍍電鍍鉑，嘗試以Pt/PdO/C.C. 觸媒(Carbon Cloth , C.C.代表碳布)。利用甲醇、CO-stripping 循環伏安法及計時安培法觀察對觸媒電催化性能的效應，探討許氧化鈀薄膜能增進鉑對於抗毒化的效果。利用TEM觀察在不同電流密度下之脈衝電鍍白金奈米顆粒之微觀結構，研究能提升白金催化的效應，同時探討白金顆粒的大小對於氧化鈀抗毒化之功效之其關連性。 實驗結果顯示，利用10mA/cm2及15mA/cm2以及不同圈數( Ton + Toff )脈衝電鍍條件，電鍍白金於氧化鈀薄膜上，Pt/PdO具有提升電化學催化的效果，Pt/PdO/C.C. 相較於Pt/C.C. 具有抗毒化的功效。由TEM分析結果，當白金觸媒粒徑越小，其氧化鈀薄膜抗毒化的功效越好。其最佳化條件參數以10mA/cm2 , 850圈之白金電鍍於氧化鈀薄膜上效果最好。

The main object of this study is to improve the performance of the anode catalyst in direct methanol fuel cell. We sputtered deposited palladium oxide (PdO) nanoflakes on carbon cloths (C.C.) as the anode catalyst support for direct methanol fuel cells (DMFC). Well dispersed Pt catalyst nanoparticles were electrodeposited on the PdO nanoflakes using galvanic pulse anodization method. According to microscopy studies, the size of Pt nanoparticles ranged from 3 nm to 5 nm, depending on the pulse anodization parameters, such as the current density and the period of the on-off pulse cycle. Cyclic voltammetry (CV) and chronoamerometry were used to study the methanol oxidation reaction of the Pt/PdO/C.C. anode. The use of the PdO nanoflakes and the Pt nanoparticles could greatly increase the electroactive surface area, and thus improved the electrocatalytic performance of the Pt/PdO/C.C. anode. In addition, the hydrophilic nature of the PdO surface under the electrocatalytic condition was likely to enhance the CO tolerance of the nanosized Pt catalyst. We have found that the CO tolerance increased with decreasing the particle size of the Pt catalysts.