Characterization of Electrocatalytic Methanol Oxidation Activity of PtRu Catalyst

• Main Authors: SUJAN CHOWDHURY, 書正
• Other Authors: Shawn D. Lin
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/45427119803769825543

碩士 === 元智大學 === 化學工程與材料科學學系 === 95 === ABSTRACT Methanol oxidation reaction (MOR) of Pt-Ru/C (ETEK) catalyst was studied with half cell analysis, aiming to identify a suitable procedure for the determination of intrinsic catalytic activity. Catalysts’ loading effect on MOR was examined, since the intrinsic catalytic activity should be independent of the amount of catalyst. Potential-scan tests (Cyclic Voltammetry, CV) were conducted to evaluate the catalytic activity of a PtRu/C electrocatalyst and pseudo-steady state was obtained. The results show that, both the catalyst activation by N2-CV and the MOR activity analysis by CV can be affected by the variation of the potential scan range. For the catalyst activation by N2-CV, a scan range to 0.9 V vs NHE resulted in higher active area (from H+ desorption charge) than that of 0~0.7 V. For the MOR activity analysis, a scan range of 0~0.7 V yields a loading independent specific activity based on the active area measured in the presence of MeOH. When a scan range of 0~0.8 or 0~0.9 V is used, the observed specific activity shows some variation with catalyst loading, and the average specific activity is lower than that measured by a scan range of 0~0.7 V. The Tafel slope for MOR is found within 200~440 mV/dec. The reaction order on MeOH is 0.2~0.6 depending on the operating potential for 0.25~2 M concentration range. Effect of Nafion film thickness was examined in this study and no significant influence on MOR was found at an average film thickness of 0.16~1.64 ?慆. Onset potential given by different definitions were also examined. It is found that onset potential depends on the definition and less on the potential scan range and methanol concentration in CV. Chronoamperometric analysis is also shown for pseudo steady state catalytic activity. However, the activity from chronoamperometric analysis is formed lower than that from CV. It is concluded that the intrinsic MOR catalytic activity is preferably analyzed by CV with the scan range up to 0.7 V. Following the proposed procedure, the intrinsic catalytic activity of PtRu Black (E-TEK) for MOR at room temperature was measured and compared with that of PtRu/C. PtRu Black shows higher catalytic activity in different MeOH concentration.