Water-Gas-Shift and SOFC Anodic on Transition Metal Surfaces

• Main Authors: Lin chia-hau, 林家豪
• Other Authors: Wang Jeng-han
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/56507302853704547034

碩士 === 國立臺灣師範大學 === 化學系 === 99 === This thesis reports two kinds of catalytic reactions on a series of transition metals.In the first part, a density functional theory (DFT) calculation has been carried out to investigate water-gas-shift reaction (WGSR) on the chemical related materials of Co,Ni, Cu, (from the 3d row) Rh, Pd, Ag, (from the 4d row) Ir, Pt and Au (from the 5d row). The result shows that WGSR mechanism involves the redox, carboxyl, and formate pathways. The reaction barriers in the three pathways are competitive and have similar a trend that groups 9 > 10 > 11 and 3d > 4d > 5d. Thus, the bottom-right d-block metals (Cu, Ag, Pt, and Au) show better WGSR activity. The experimentally most observed intermediate of formate can be attributed to its lower formation and higher decomposition barriers. Furthermore, the catalytic behavior on these active metal surfaces has been examined. The result shows that WGSR is mostly follows the redox pathway on Ag(111) and Au(111) surfaces due to the negligible CO* oxidation barriers; on the other hand, all the three pathways contribute similarly in WGSR on Cu(111) and Pt(111) surfaces. Finally, the feasible steps of formyl in Fischer-Tropsch synthesis (FTS), the combustion reaction, and formate pathway have also been examined. The result shows that activities of FTS and the WGSR have opposite trends on the metal surfaces. Formyl preferentially follows the formate pathway on Cu, Ag, Pt, and Au catalysts. In the second part, we experimentally examine the catalytic activity of the anodic reaction in solid oxide fuel cell (SOFC) on the highly active anodes of Co/YSZ, Ni/YSZ, Cu/YSZ, Pd/YSZ, Ag/YSZ, Pt/YSZ, and Au/YSZ cermets. Both anodic and electrolyte supported SOFC are initially fabricated by co-pressing, impregnation and spin coating methods. The cells are ex-situ characterized XRD, SEM and EDX to indentify the composited anodes, investigate the surface morphology, and confirm the elementary composition, respectively. The cells are followed by in-situ cell performance test with hydrogen fuel at the temperature range of 600 – 850 oC. The tested result shows that anodic supported cell by spin coating method shows the highest performance. In the electrolyte supported cell, the anodic reaction, hydrogen oxidation reaction (HOR), follows the order of Au-YSZ > Ag-YSZ > Pt-YSZ > Ni-YSZ > Co-YSZ > Cu-YSZ > Pd-YSZ. The catalytic behaviors on different anodic materials have been preliminarily discussed.