The catalytic properties of gold have been widely investigated. In Dr. Chao-Ming Chiang¡¦s study, department of chemistry of NSYSU, they found that the organic molecules, propanal, form heterocyclic 2, 4, 6- triethyl-1, 3, 5-trioxane ring on Au(110) missing row surface at 180 K by temperature programmed desorption (TPD) and reflection absorption infrared spectra (RAIR). In this study, we used low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) to study the detailed catalytic process on surface. Residual gas analyzer (RGA) was used to measure the thermal desorption of the propanal on Au(110) at 130 K and 185 K. This can be used to calibrate the temperature on the surface, which can not be directly measured by the thermal couple on the manipulator. The combination between the LEED pattern from the experiment and the DFT model shows the propanal adsorbed on the inclined plane with about 64 deg. to 71 deg. companing the (110) plane. The STM results also show that some of the surface after adsorption have trench wider atomic rows. In our experiment, the real temperature of the sample was not exactly determined. More experiments need to be taken to confirm the temperature.

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Gold¡¦s reputation as an inactive catalyst has been changed since the discoveries made by pioneers, including Bond, Hutchings, and Haruta. Today, exploring gold¡¦s potential to catalyze a range of heterogeneous and homogeneous reactions has been a hot topic. In this dissertation, reaction of CO and hydroxyl groups and cyclotrimerization of propanal (C2H5CHO) catalyzed by gold were studied by using temperature-programmed desorption (TPD), reflection absorption infrared spectroscopy (RAIRS), X-ray photoemission spectroscopy (XPS), low energy electron diffraction (LEED) and density functional theory (DFT) calculations. keywords: LEED, XPS, RAIRS,TPD, Gold, cyclotrimerization, propanal, CO oxidation In the first topic, CO oxidation by hydroxyl groups prepared by electron beam bombardment of physisorbed water was performed on Au(110) and Au(531). The formation of hydroxyl groups was evidenced by the observation of the desorption of D2O at 175 K and D2 at 230 K in TPD, in conjunction with the O 1s peak at 531.32 eV in XPS. The adsorption of CO on the hydroxyl-covered surface resulted in CO2 desorption at 110 K and 150 K on Au(110), and 105 K, 140 K and 180 K on Au(531). In the investigation of various D2O and CO coverages, the adsorption of CO and D2O was found to be preferred on low-coordinated Au atoms. Additionally, D2O on low-coordinated Au atoms required lower dissociation energy. This site effect was correlated with the high activity of smaller gold nanoparticles. Moreover, the mechanism for reaction of CO and hydroxyl groups was suggested to be similar to the water-gas-shift reaction due to the observation of the enhancement of D2 desorption after reaction. The second topic studied the cyclotrimerization of propanal catalyzed by gold. After exposing Au(110) to propanal at 180 K, the desorption of 2,4,6-triethyl-1,3,5-trioxane ((C2H5CHO)3) was observed at 340 K. The RAIRS and XPS studies showed that the cyclotrimerization of propanal was completed at 180 K. The same results were also detected on Au(531). However, only propanal molecular desorption was found on Au(111) suggesting that the low coordination Au atoms and the trench-like structure on Au(110) and Au(531) play key roles. On Ag(110) and Cu(110), no reaction was found indicating that the intrinsic nature of gold is also an important factor for the reaction. Investigation on Pt(110) inherited with the same (1x2) missing-row structure revealed that the decarbonylation of propanal occurred due to the stronger £b2(C,O) bonding mode. The reactions observed on Au(110), Au(531), and Pt(110) strongly suggest that the activity for the reactions may result from the relativistic effect of gold. The DFT calculations further showed the interactions between hydrogen in carbonyl groups and low-coordinated Au atoms (O=C-H¡KAu) help to gather propanal molecules and preorganize them at specific surface sites while an intracomplex reaction takes place.