Preparation of PtRuTa/C electrocatalysts for improving the stability of Pt-Ru based anodes for use in direct methanol fuel cell

• Main Authors: Hsin-Yu Ke, 柯心喻
• Other Authors: 卓錦江
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/50608101586068757478

碩士 === 國立高雄應用科技大學 === 化學工程與材料工程系 === 100 === PtRuTa/C tri-metal electrocatalysts were prepared by impregnation method for use as anode catalysts, with an attempt to improve the stability and electrocatalytic activity of the PtRu for methanol oxidation reaction (MOR). The lattice parameters, composition, and particle size distribution of catalysts were characterized by the means of X-ray diffractometer (XRD), X-ray energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), and scanning electron microscope (SEM), respectively. The electrochemical behaviors of the electrodes were studied by cyclic voltammetry (CV), chronoamperometry (CA), and CO-stripping voltammetry. The inductively coupled plasma-mass spectrometer (ICP-MS) was used to detect the dissolved species in the immersing solutions (0.5 M H2SO4 + 2.0 M CH3OH), used for examining the degradation and dissolution of the PtRu catalysts during the out-of-service time. The results show that the atomic ratios of Pt, Ru, and Ta in the PtRuTa/C catalysts are approximately equal to the known values in the original precursor solutions, indicating the successful preparation of the PtRuTa catalysts. The particle size of the PtRuTa/C catalysts is 4.3 to 6.1 nm with a spherical structure. The catalysts are well dispersed on the carbon black supports; however, the distributions of Pt atoms decrease, while the agglomeration increases, with the increase of Ta content. On the other hand, the exact methanol oxidation on-set potential (VMOSP) at various PtRu based catalysts are obtained accurately by extrapolation at a scan rate of zero. The results show that the optimum ratio of Pt: Ru is ca. 1:1, and the dependence of VMOSP on the Ta content in the catalyst is insignificant。In addition, the stability of the catalysts for MOR increases significantly with the increase of Ta contents, while the specific activity of the catalysts increases when the Ta content is less than 5 atom %. Additionally, the degradation and dissolution of the PtRu catalysts during the out-of-service time examined by immersing tests shows that, as well as that in the operation time, the dissolution of Ru on the catalysts is effectively depressed in the presence of Ta due to the formation of Ta2O5.