Title：	XPS Investigations of Reactions on Stepped Pt and Flat TiO2 Surfaces
Speaker：	Regine Streber ( Aarhus University，Denmark)
Time：	2011-10-17　 10:00
Location：	3#210

 

 

 

 

 

 

 

 

 

Without heterogeneously catalyzed reactions, the vast majority of consumer products today would not be available. Commonly, highly dispersed particles of catalytic materials exhibiting a variety of defects are employed as catalysts. In fact, these defects are thought to be highly reactive. Poisoning of the catalyst’s active sites poses a major problem, e.g., sulfur impurities from crude oil are known to poison platinum containing catalysts. However, the underlying principles and mechanisms of this are poorly understood at present.

In order to clarify a) the reactivity of steps and b) the effects of poisoning these sites, we investigated the adsorption of CO and its reaction with oxygen on stepped and flat platinum with and without coadsorption of sulfur by means of high resolution x-ray photoelectron spectroscopy (HR-XPS). The high photon flux and good energy resolution provided by the synchrotron source (BESSY II) allowed us to perform time-resolved measurements to determine reaction kinetics as well as obtaining information on the adsorption site.

Titanium dioxide (TiO2) is another well known material in heterogeneous catalysis – as a photocatalyst or as a supporting material; in both cases, the reducibility of TiO2 plays an important role. While in many practical applications anatase TiO2 is employed, rutile TiO2(110)-(1×1) has been preferred in surface science studies. The Ti3d defect state in the band gap of rutile TiO2(110) observed in these studies was assumed to be caused by bridging oxygen vacancies. Based on recent high-resolution STM and UPS measurement we propose that Ti interstitials in the surface near region are predominantly responsible for the defect state.