期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 141, 期 20, 页码 8185-8197出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.9b00486
关键词
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资金
- Flagship Green Energy Programme from National University of Singapore
- National Science Foundation [ACI-1548562]
- UCLA
- project Ensemble representation for the realistic modeling of cluster catalysts at heterogeneous interfaces by the U.S. Department of Energy, Office of Science, Basic Energy Sciences [DE-SC0019152]
Unlike nanostructured metal catalysts, supported single-atom catalysts (SACs) contain only atomically dispersed metal atoms, hinting at much more pronounced metal-support effects. Herein, we take a series of polyoxometalate-supported Pt catalysts as examples to quantitatively investigate the stability of Pt atoms on oxide supports and how the Pt-support interaction influences the catalytic performance. For this entire series, we show that the Pt atoms prefer to stay at a 4-fold hollow site of one polyoxometalate molecule and that the least adsorption energy to obtain sintering-resistant Pt SACs is 5.50 eV, which exactly matches the cohesive energy of bulk Pt metal. Further, we compared their catalytic performance in several hydrogenation reactions and simulated the reaction pathways of propene hydrogenation by density functional theory (DFT) calculations. Both experimental and theoretical approaches suggest that despite the Pt-1-support interactions being different, the reaction pathways of various Pt-1-polyoxometalate catalysts are very similar and their effective reaction barriers are close to each other and as low as 24 kJ/mol, indicating the possibility of obtaining SACs with improved stability without compromising activity. DFT calculations show that all reaction elementary steps take place only on the Pt atom without involving neighboring O atoms and that hydrogenation proceeds from the molecularly adsorbed H-2 species. Pt SACs give a weaker H-2 adsorption energy than Pt clusters or surfaces, resulting in small adsorption equilibrium constants and small apparent activation barriers, which agree between experiment and theory.
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