| 摘要: | 高活性直接甲醇燃料電池陽極觸媒必須滿足以下幾點：(一) 載體必須具有足夠的導電性、(二)活性中心均勻的附載於載體表面、 (三) 觸媒顆粒必須要小。本研究利用高表面積碳黑 Ketjen black ECP300 (855m2/g) 作為載體，分別以雙氧水與臭氧對其表面進行改質，藉由增加碳黑表面官能基含量提高碳黑親水性與觸媒的均勻度，進而達到降低觸媒顆粒大小之目的。利用程序升溫脫附(TPD)鑑定表面官能基性質、比表面積與孔隙偵測(BET)鑑定改質後碳黑結構的改變及四點探針測試改質後導電度的改變，配合循環伏安法 (Cyclic Voltammetry )測試觸媒對甲醇氧化的電化學活性，篩選出最適用於高活性甲醇燃料電池陽極觸媒之碳黑載體。 並探討不同還原劑對合成觸媒之影響，再分別以穿透式電子顯微鏡(TEM)及X光繞涉光譜(XRD)鑑定觸媒的微結構及合金程度，螢光繞涉(XRF)分析合成觸媒組成， X 射線光電子能譜儀(XPS)進行觸媒表面成分分析，進一步由X光吸收光譜(XAS)探討鉑釕原子分佈對活性之影響，其中以次磷酸鈉作為還原劑不僅能有效降低觸媒粒徑大小，並能製造均勻組成之鉑釕合金，配合最適化之碳黑載體能合成出活性高於商業觸媒(Johnson Matthey)之高甲醇氧化能力觸媒。 There are some criteria for high performance direct methanol fuel cell anode electrocatalysts：The material used as support has high conductivity, reaction centers dispersed homogeneously on support’ s surfaces and the particle size of anode catalysts must be small. In this study we use high surface carbon black, Ketjen Black EC300 , with surface area of 855 m2/g , as the support. In order to increase the hydrophilic ability of EC300 and has a more homogenous dispersed reaction centers, we functionlized these carbon black’s surface by H2O2 and ozone, respectively, and we hope the particle size of catalysts can be reduced by these surface modifications. Temperature Programmed Desorption was used to identify those functional groups created by surface modification of carbon black, Brunauer-Emmett-Teller method was used to check the surface area and porosity of those modified carbon black, and conductivities of these modified carbon black were obtained by four-probe method. We test the methanol oxidation ability of catalysts supported on these modified carbon black by using cyclic volatommetry measurement, and find out the most adaptable carbon black for high performance anode electrocatalysts for use in DMFC. Furthermore, we used NaBH4, HCHO and NaH2PO2 as reduction agents, and research the influence of these agents on electrocatalyst synthesis. These catalysts were characterized by XRD and TEM, components of these catalysts were detected by XRF and XPS, EXAFS had been used to study the microstructure of NaH2PO2-synthesised catalysts. We found that NaH2PO2 can effectively reduce the particle size of the active site of anode catalyst, furthermore better dispersion on carbon black was also accomplished. The catalysts prepares in the study have better performance and in methanol oxidation then commercial, Johnson Matthey H10100 catalysts. Particle size, Pt-Ru ratio on the catalyst surface and conductivity of the carbon support are the key factor contribute to the performance of the catalyst. |
