Ambient-Pressure X-ray Photoelectron Spectroscopy Study of Cobalt Foil Model Catalyst under CO, H2, and Their Mixtures
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- 作者：Cheng Hao Wu ; Baran Eren ; Hendrik Bluhm ; Miquel B. Salmeron
- 刊名：ACS Catalysis
- 出版年：2017
- 出版时间：February 3, 2017
- 年：2017
- 卷：7
- 期：2
- 页码：1150-1157
- 全文大小：574K
- ISSN：2155-5435
文摘
Ambient-pressure X-ray photoelectron spectroscopy (XPS) was used to investigate the reactions of CO, H2, and their mixtures on Co foils. We found that CO adsorbs molecularly on the clean Co surface and desorbs intact in vacuum with increasing rate until ∼90 °C where all CO desorbs in seconds. In equilibrium with 100 mTorr gas, CO dissociates above 120 °C, leaving carbide species on the surface but no oxides, because CO efficiently reduces the oxides at temperatures ∼100 °C lower than H2. Water as impurities or produced by reaction of CO and H2 efficiently oxidizes Co even at room temperature. Under 97:3 CO/H2 mixture and with increasing temperatures, the Co surface becomes more oxidized and covered by hydroxyl groups until ∼150 °C where surface starts to get reduced, accompanied by carbide accumulation indicative of CO dissociation. A similar trend was observed for 9:1 and 1:1 mixtures, but surface reduction begins at higher temperatures.