The midas touch on copper into palladium
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e midas touch on copper into palladium Jie Zeng
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Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China Received August 9, 2020; accepted August 11, 2020; published online September 1, 2020
Citation:
Zeng J. The midas touch on copper into palladium. Sci China Chem, 2020, 63, https://doi.org/10.1007/s11426-020-9849-0
The catalytic semi-hydrogenation of alkynes (C≡C) to alkenes (C=C) has long been a crucial and challenging step in industry as it restrains the tendency of over-hydrogenation towards substrates [1]. Up to now, Pd-based catalysts show ultrahigh activity and selectivity towards the semihydrogenation of alkynes and are commonly used in industry, while metals such as Cu, Ag and Au exhibit relatively low activity due to their poor hydrogen activation ability. “Hydrogen spillover” is a common phenomenon in catalytic hydrogenation process [2]. The word “spillover” was first used to describe the migration of H atoms from hydrogenactivated sites onto support in the 1960s [3]. It is so-called “spillover hydrogenation” when a catalytic hydrogenation process involves spilled H species. This concept has been frequently used to explain the hydrogenation behavior of various catalysts such as single atom alloys [4]. For a Pt1Ni single-atom alloy catalyst, H2 was dissociated at Pt single atoms, followed by spillover onto Ni sites where substrate molecules were hydrogenated efficiently [5]. Though the concept has been proposed for years, several doubts about the mechanism still exist. Neither the support structure, nor the distance limit required for hydrogen spillover is clear yet. In the latest issue of Nature Nanotechnology, Jiang et al. [6] proposed a so-called “golden touch” strategy to activate “inert” Cu host facets with the hydrogen spillover from Pd single atoms, thus manufacturing a cost-effective spillover hydrogenation catalyst with low Pd usage. Such Pd1/Cu catalysts with 50 ppm Pd loading performed effectively in semi-hydrogenating a broad range of alkynes. Mechanism *Corresponding author (email: [email protected])
studies confirmed that the host metal facet played a critical role in the spillover hydrogenation. The authors creatively proposed a novel strategy to characterize the hydrogen spillover process, where they found that hydrogen spillover distance can reach at least 500 nm on Cu metal hosts. In order to provide the more proof on the spillover hydrogenation mechanism of single atom alloy catalysts, the authors designed model catalysts with Pd single atoms on different Cu facets. They first synthesized Cu nanosheets and nanocubes which selectively exposed Cu(111) and (100) facets, respectively (Figure 1(a, b)). Then Pd single atoms were introduced onto Cu facets by galvanic process to form Pd1/Cu(111) and Pd1/Cu(100) catalysts. The isolated Pd single atomic structure was confirmed by Fourier transform extended X-ray absorption fine structure spectra with only one peak at 2.3 Å (Figure 1
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