Low temperature CO oxidation on differently prepared TiO2(110) supported Au catalysts

Abstract

The preparation of Au/TiO2(110) planar catalysts and the low temperature (LT) oxidation of CO (in H2) were investigated by Scanning Tunnelling Microscopy (STM), Auger-electron Spectroscopy (AES) and Thermal Programmed Reaction (TPR). The distribution and the mean size of the Au particles were modified by different pretreatments of the support: (A) Ar+ bombardment; deposition to (B) 0.05 ML of K or (C) 0.5 ML of Mo. It was shown that the mean size of the Au particles formed at RT is 3-4 nm on the clean TiO2(110) surface and this value deacreased to 1.5-2 nm for all pretreated supports. These 2D catalysts were tested in the LT oxidation (PROX) of CO. The same reaction conditions were kept for all experiments: the reaction chamber was filled up to 0.5 hPa O2, 0.5 hPa CO and 9 hPa H2 and the temperature of the catalyst was increased from 310 K to 400 K, 450 K or 500K for 60 minutes. The clean, Ar+pretreated, K or Mo preexposed oxide surfaces exhibited no activity in the PROX reaction. By the deposition of Au of 1-3 monolayer on to these surfaces, however, an enhancement of CO2 in the gas phase was clearly detected. The clean TiO2(110) surface prooved to be the best support for gold, any modification of the support resulted in a loss of the activity. For all cases dependently on the pretreatments, the mean size of the Au particles increased significantly up to 4-8 nm in the PROX at 500 K.