4.8 Article

Support-Induced unusual size dependence of Pd catalysts in chemoselective hydrogenation of para-chloronitrobenzene

期刊

JOURNAL OF CATALYSIS
卷 400, 期 -, 页码 173-183

出版社

ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcat.2021.06.002

关键词

Chemoselective hydrogenation; Pd catalyst; Particle size effect; Support effect; Electronic promotion

资金

  1. National Science Fund for Distinguished Young Scholars [22025205]
  2. National Natural Science Foundation of China [21673215]
  3. DNL Cooperation Fund, CAS [DNL201907]
  4. Users with Excellence Program of Hefei Science Center CAS [2019HSC-UE016]
  5. Fundamental Research Funds for the Central Universities, China [WK2060030029]
  6. Max-Planck Partner Group

向作者/读者索取更多资源

Pd nanoparticles supported on oxygen-functionalized carbon black exhibit an unexpected inverse trend of selectivity compared to those on carbon black. The balance of positive Pd delta+ species strongly modulates the competitive adsorption of different groups on the substrate, affecting the chemoselectivity of the catalytic reaction.
For supported metal catalysts, the underlying support not only disperses and stabilizes metal particles, but also modulates their electronic structures remarkably, and even directly participates in catalytic reactions. Here we report that Pd nanoparticles (NPs) supported on oxygen-functionalized carbon black (Pd/O-C) show an unexpected inverse trend of selectivity on Pd particle size in chemoselective hydrogenation of para-chloronitrobenzene (p-CNB), compared to those on carbon black (Pd/C). In situ X-ray photoemission spectroscopy reveals that the Pd NPs are more positively charged with decrease of particle size in both samples, while the Pd NPs in Pd/O-C have relatively higher fractions of positive Pd delta+ species than those in Pd/C with similar sizes. Fourier transform infrared spectroscopy shows that the balance of positive Pd delta+ species strongly modulates the competitive adsorption of -NO2 and -Cl group in p-CNB according to their different electronegativities. As a consequence, we, for the first time, demonstrate that a moderate positive charge of Pd NPs is essential to improve the p-chloroaniline (p-CAN) selectivity, while too high or too low positive charge could impel the adsorption of the less negatively charged-Cl group, thus generating the dehalogenated aniline by-product. These findings suggest that precise tailoring of the electronic structures of metal NPs could be essential for design of high chemoselective metal catalysts. (C) 2021 Elsevier Inc. All rights reserved.

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