Potential application of tungsten carbides as electrocatalysts - III. Reactions of methanol, water, and hydrogen on Pt-modified C/W(111) surfaces

被引:59
作者
Liu, N
Kourtakis, K
Figueroa, JC
Chen, JGG [1 ]
机构
[1] Univ Delaware, Dept Mat Sci & Engn, Ctr Catalyt Sci & Technol, Newark, DE 19716 USA
[2] DuPont Co Inc, Cent Res & Dev, Wilmington, DE 19880 USA
关键词
fuel cells; tungsten carbides; Pt-modified C/W(111);
D O I
10.1016/S0021-9517(03)00019-8
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The bonding and dissociation of methanol, water, and hydrogen on Pt-modified C/W(111) surfaces have been studied using high-resolution electron energy loss spectroscopy and temperature-programmed desorption. The decomposition pathways of methanol on C/W(111) are significantly modified by the presence of submonolayer coverages of Pt. For example, on the unmodified C/W(111) surface, the decomposition of methanol occurs via three pathways: (i) partial decomposition to produce carbon monoxide and hydrogen (similar to31% selectivity), (ii) partial decomposition to form methane and atomic oxygen (similar to14% selectivity), and (iii) complete decomposition to produce hydrogen, atomic carbon, and atomic oxygen (similar to55% selectivity). In contrast, on the 0.6 monolayer (ML) Pt-modified C/W(111) surface, similar to49% of methanol partially dissociates to carbon monoxide and hydrogen, and the other similar to51% of methanol molecules undergo complete decomposition to hydrogen, atomic carbon, and atomic oxygen. The presence of submonolayer coverages of Pt prohibits the production of methane, which is an undesirable side product in direct methanol fuel cells. Furthermore, both the C/W(111) and the Pt-modified C/W(111) surfaces are active toward the dissociation of water. However, the amount of adsorbed water that undergoes dissociation is reduced from 0.18 H2O per W atom on C/W(111) to 0.056 H2O per W on the 0.6 ML Pt-modified C/W(111) surface. Finally, both C/W(111) and 0.6 ML Pt/C/W(111) surfaces are active toward the dissociation of hydrogen. These results demonstrated the possible synergistic effects by supporting low loading of Pt onto tungsten carbides for potential applications in methanol or hydrogen fuel cells. (C) 2003 Elsevier Science (USA). All rights reserved.
引用
收藏
页码:254 / 263
页数:10
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