期刊
NANO LETTERS
卷 11, 期 2, 页码 847-853出版社
AMER CHEMICAL SOC
DOI: 10.1021/nl104209c
关键词
In-situ X-ray absorption; Bimetallic CoPt nanoparticles; oxidation states; alloy effect; cycling pressure; octahedral and tetrahedral structure
类别
资金
- Director, Office of Energy Research, Office of Basic Energy Sciences of the U.S. Department of Energy [DE-AC02-05CH11231]
- U.S. Department of Energy [DE-AC02-05CH11231]
In-situ near edge X-ray absorption fine structure spectroscopy was performed to monitor the wddation states of Co and CoPt nanoparticles (NPs) of 4 nm size in the presence of H-2 and O-2 in the pressure range of 1 bar and 36 Torr respectively. Platinum helps the rapid reduction of cobalt oxides in hydrogen at a rather low temperature (38 degrees C). In addition, reversible changes of the oxidation states of cobalt in the Co and CoPt NPs as a function of cycling oxygen pressure (in the range of millitorr to 36 Torr) are quantified and compared. The role of Pt in the process of Co reducing and oxidizing was explored. Our findings permit the prediction of the cobalt oxidation states as the reaction conditions are altered. The experimental results also suggest the presence of tetrahedral structure of Cobalt oxide that differs from the Co3O4 spinel structure.
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