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Gold Oxide Formation on TiO2/Au(111) Model Catalysts

Date
Tuesday 31 March 2020
Time
Address
Hotel NH Noordwijk Conference Centre Leeuwenhorst

Sabine Wenzel, Dajo Boden, Mahesh K. Prabhu, Irene M. N. Groot
Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands

Hydrogen produced from methanol has to be cleaned from traces of CO for its use in fuel cells [1]. Conventional CO oxidation catalysts such as platinum and palladium oxidize hydrogen as well and are thus not suitable. Alternative gold-based catalysts have been shown to selectively oxidize CO at low temperatures [2]. There is ample evidence for strong interactions between gold and typically used supports such as TiO2 [3]. However, the exact oxidation state of the active phase of gold remains under debate [4,5].

Our set-up [6] allows for the controlled preparation and characterization of model catalyst surfaces in ultra-high vacuum combined with scanning tunneling microscopy at atmospheric pressures and elevated temperatures. A TiO2/Au(111) model catalyst was prepared via physical vapor deposition and exposed to CO oxidation reaction conditions. We present evidence for the formation of a surface gold oxide in this environment as can be seen in Figure 1. Finally, we discuss the role that the titania nanoparticles, contaminants on the gold substrate and the water background in the gas mixture play in the oxidation of the gold substrate.

Figure 1: a) 120 nm x 120 nm image of the as-prepared TiO2/Au(111) model catalyst. b) 120 nm x 120 nm image of the same surface after exposure to 1 bar of 4 O2 + 1 CO for 1 hour showing the surface gold oxide. c) 10 nm x 10 nm zoom of the marked region in b) showing the squared unit cell of the surface gold oxide.

References

  1. Dhar et al., J. Electrochem. Soc. 1987, 134, 12, 3021.
  2. Haruta, The Chemical Record  2003, 3, 75–87.
  3. Palomina et al., ACS Sustainable Chem. Eng. 2017, 5, 10783.
  4. Min et al., Chem. Rev. 2007, 107, 2709.
  5. Klyushin et al., ACS Catal. 2016 6, 3372.
  6. Herbschleb et al., Rev. Sci. Instrum. 2014, 85, 083703.

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