XRD patterns showing (a) Pt NPs, (b) Pt@Sn NPs, and (c) Pt-SnO2 NPs obtained by calcination of Pt@Sn NPs at 500 ℃ for 3 h.
TEM studies of Pt NPs, Pt@Sn NPs, Pt/Al2O3, and PtSnO2/Al2O3
Catalytic Performance
the catalytic activities and selectivities for hydrogenation of nitrobenzaldehyde and nitroacetophenone over Pt-SnO2/Al2O3 are higher than those over Pt/Al2O3 except that the catalytic activities for p-NAP hydrogenation over Pt-SnO2/Al2O3 and Pt/Al2O3 are the same (100%).
XPS spectra showing (a) as-synthesized Pt@Sn and (b) Pt-SnO2
Small percentages of Snδ+ and Pt2+ are observed for Pt@Sn NPs and Pt2+、Pt4+ are observed for Pt-SnO2 NPs presumably due to the exposure of NPs to air. The binding energies at 486.6/494.9 eV in Figure b can be assigned to 3d5/2/3d3/2 of Sn4+, which is consistent with the XPS database of SnO2 and their XRD patterns.
TPO study of Pt@Sn/Al2O3
further confirms the complete oxidation of Sn of Pt@Sn below 300℃
DRIFT-IR spectra with CO probes
linear CO on Pt step and kink sites
Pt-SnO2/Al2O3 nanocatalysts had higher activity and selectivity than Pt/Al2O3 nanocatalysts, with the exception that the selectivity of catalytic m-CNB hydrogenation over Pt-SnO2/Al2O3 is lower than that over Pt/Al2O3.
The higher Sn/Pt ratio for Pt@Sn by XPS is consistent with Pt@Sn core@shell structures The Pt/oxidized Pt ratio of 27.68/72.32 for Pt-SnO2 indicates that more surface Pt atoms are oxidized by calcination Sn/Pt ratio of 2.79/ 1.00 by XPS suggests heteroaggregate nanostructures with a distribution of SnO2 on Pt surfaces.
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XPS
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TPO
DRIFT-IR
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XRD patterns of individual Pt, assynthesized Pt@Sn, and Pt-SnO2 NPs obtained by calcination of Pt@Sn NPs
As shown in Figure 1b, nearly pure Pt diffractions were observed and Sn diffractions were invisible for Pt@Sn NPs. The clear Pt and SnO2 diffractions for PtSnO2 NPs in Figure 1c are consistent with the presence of Sn in the Pt@Sn NPs, although the Sn diffractions were not observed in Figure 1b.
linear CO on Pt terrace sites
linear CO on Pt step and kink sites
Only CO bands on Pt are observed, since CO is not adsorbed on tin
the surfaces mainly consist of Sn and the majority of Pt is in the cores
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Catalytic Stability of Pt-SnO2/Al2O3
Within the first five cycles, the catalytic activity of Pt-SnO2/Al2O3 was stable, and the catalytic selectivity slightly increased, suggesting a good structural stability of Pt-SnO2 heteroaggregate nanocatalysts
theoretical calculations(using DET)
the partial coverage of Pt (111) surfaces with SnO2 slightly promotes the H adsorption on Pt (111) surfaces. the Pt-SnO2 nanostructures can slightly facilitate the adsorption of o-CNB. the cooperative Pt−SnO2 interaction can desorpt products easier, resulting in more catalytic surface being available and a fast reaction rate the enhanced catalytic performance of Pt-SnO2/Al2O3 nanocatalysts originates from the cooperative interaction between Pt and SnO2 inside the heteroaggregate nanostructures
Catalytic Performance
Pt-SnO2/Al2O3 with a Pt/Sn ratio of 1/1 has the highest catalytic activity and excellent catalytic selectivity
Catalytic Performance
Catalytic Performance
Pt-SnO2/Al2O3 nanocatalysts had higher activity than Pt/Al2O3 nanocatalysts, while the selectivities over PtSnO2/ Al2O3 and Pt/Al2O3 are the same (100%)
Design of Highly Efficient Pt-SnO2 Hydrogenation Nanocatalysts using Pt@Sn Core−Shell NanoparticlesΒιβλιοθήκη 1.synthesis
Characterization
2.
Characterization
XRD TEM
Conclusion
1、 DRIFT-IR with CO probes, HRTEM, and XPS studies confirmed Pt-SnO2 heteroaggregate nanostructures, where SnO2 partially covered the Pt nanoparticle surface. 2、In comparison to the control Pt nanocatalysts, the Pt-SnO2 nanocatalysts exhibited higher catalytic activity and selectivity . 3、the enhanced catalytic performance of Pt-SnO2/Al2O3 originates from the cooperative Pt−SnO2 interaction inside the heteroaggregate nanostructures.