Catalysis Letters, Vol.57, No.1-2, 49-53, 1999
XPS and DRS of Au/TiO2 catalysts: effect of pretreatment
TiO2 impregnated with AuCl3 was subjected to different pretreatments and then characterized by XPS and DRS. After drying at 298 K under vacuum, the catalyst contains highly dispersed, nonmetallic Au species; whereas drying at 393 K in an oven caused the Au to be partially reduced and agglomerate. Further treatments of the oven-dried sample at higher temperatures resulted in the disappearance of Au signals in XPS except the one after a HTR/C/LTR (high-temperature reduction/calcination/low-temperature reduction) sequence. The high-temperature reduction at 773 K shifted the plasmon resonance peak in DRS to higher wavelength, and the following C and LTR treatment did not change the peak position. This peak shifting is interpreted as a change in the electronic status of the Au.