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. 2017 Oct 13;3(10):e1700231.
doi: 10.1126/sciadv.1700231. eCollection 2017 Oct.

Classical strong metal-support interactions between gold nanoparticles and titanium dioxide

Hailian Tang  1   2   3 , Yang Su  1 , Bingsen Zhang  4 , Adam F Lee  5 , Mark A Isaacs  5 , Karen Wilson  5 , Lin Li  1 , Yuegong Ren  1   3   6 , Jiahui Huang  1   6 , Masatake Haruta  1   6   7 , Botao Qiao  1 , Xin Liu  1 , Changzi Jin  1   2 , Dangsheng Su  1   4 , Junhu Wang  1   2 , Tao Zhang  1   2   3
Affiliations

Classical strong metal-support interactions between gold nanoparticles and titanium dioxide

Hailian Tang et al. Sci Adv. .

Abstract

Supported metal catalysts play a central role in the modern chemical industry but often exhibit poor on-stream stability. The strong metal-support interaction (SMSI) offers a route to control the structural properties of supported metals and, hence, their reactivity and stability. Conventional wisdom holds that supported Au cannot manifest a classical SMSI, which is characterized by reversible metal encapsulation by the support upon high-temperature redox treatments. We demonstrate a classical SMSI for Au/TiO2, evidenced by suppression of CO adsorption, electron transfer from TiO2 to Au nanoparticles, and gold encapsulation by a TiO x overlayer following high-temperature reduction (reversed by subsequent oxidation), akin to that observed for titania-supported platinum group metals. In the SMSI state, Au/TiO2 exhibits markedly improved stability toward CO oxidation. The SMSI extends to Au supported over other reducible oxides (Fe3O4 and CeO2) and other group IB metals (Cu and Ag) over titania. This discovery highlights the general nature of the classical SMSI and unlocks the development of thermochemically stable IB metal catalysts.

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Figures

Fig. 1
Fig. 1. In situ DRIFT spectra of CO adsorption over RR2Ti-fresh, RR2Ti-HX (X = 200 to 500), and RR2Ti-(H500+O400) samples.
a.u., arbitrary units.
Fig. 2
Fig. 2. Electronic properties of RR2Ti samples.
(A) Au 4f XP spectra of RR2Ti-fresh, RR2Ti-H500, and RR2Ti-(H500+O400) samples. (B) EPR spectra of the RR2Ti-fresh, RR2Ti-H500, and RR2Ti-(H500+O400) samples obtained at 100 K.
Fig. 3
Fig. 3. HRTEM images and EELS spectra.
(A to F) HRTEM images of (A) RR2Ti-fresh, (B) RR2Ti-H200, (C) RR2Ti-H300, (D) RR2Ti-H400, (E) RR2Ti-H500, and (F) RR2Ti-(H500+O400). (G) EELS spectra of the RR2Ti-H500 sample. Spectra were background-subtracted.
Fig. 4
Fig. 4. Reversibility of RR2Ti properties under redox treatment.
(A) In situ DRIFT spectra of CO adsorption over the RR2Ti-fresh sample following alternating pretreatment with 10 volume % H2/He at 500°C (for the first and third cycles) or 10 volume % O2/He at 400°C (for the second and fourth cycles) for 1 hour. (B) CO conversion at 80°C for the RR2Ti-fresh sample as a function of pretreatments described in (A). Reaction gas composition: 1 volume % CO + 1 volume % O2 balanced with He; gas flow rate, 33.3 ml/min; space velocity (SV), 64,452 ml gcat−1 hour−1.
Fig. 5
Fig. 5. The CO conversion curves as a function of reaction time on the RR2Ti-fresh and RR2Ti-H400 samples tested at 300°C.
Reaction gas composition: 1.6 volume % CO, 1 volume % O2, 0.01 volume % propene, 0.0051 volume % toluene, and 10 volume % water balanced with He. For RR2Ti-H400: 40.5 mg of sample diluted with 120 mg of SiO2 powder; gas flow rate, 33.3 ml/min; SV, 49,000 ml gcat−1 min−1. For RR2Ti-fresh: 15.9 mg of sample diluted with 60 mg of SiO2 powder; gas flow rate, 33.3 ml/min; SV, 127,000 ml gcat−1 min−1.
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References

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