CO₂ as a Probe for Monitoring the Surface Defects on TiO₂(110)Temperature-Programmed Desorption

Abstract

The adsorption and thermal desorption of CO 2 bound to both oxidized and reduced TiO 2 (110) surfaces has been studied using temperature-programmed desorption. For the stoichiometric and fully oxidized surface, a single thermal desorption feature (E d ) 48.5 kJ/mol) is measured and attributed to CO 2 bound to regular fivefold coordinated Ti 4+ atoms. For the fully reduced TiO 2 (110) surface, CO 2 binds not only to regular sites, but also to oxygen vacancy sites (E d ) 54.0 kJ/mol), created by thermal annealing. The variation in the characteristic CO 2 desorption kinetics was measured as a function of the surface reduction temperature, and the systematic production of increasing levels of surface defects is observed in the temperature range of 600-1100 K. This investigation was complimented by a comparison of the characteristic CO 2 desorption features from a TiO 2 (110) surface which was prepared by sputtering and direct annealing, without annealing in O 2 flux. It was found that after annealing to temperatures above 900 K, the CO 2 thermal desorption is very similar for surfaces prepared by the two methods, regardless of surface preparation.

Observation of bimodal polyethylene derived from TiO2-supported zirconocene/MAO catalyst during polymerization of ethylene and ethylene/1-hexene

“…It revealed two desorption peaks at temperature ca. 175 and 200 K. Thomson et al [19] reported that surface of TiO 2 incorporates fivefold-coordinated Ti 4+ sites and fourfold-coordinated Ti 3+ sites. Based on their study, it was confirmed that the peak at ca.…”

CO Oxidation on Anatase TiO2 Nanotubes Array and the Effect of Defects

“…It is well documented that CO 2 is a very useful probe molecule to distinguish pristine and defect sites on metal oxides [34][35][36]. For rutile TiO 2 (110), CO 2 adsorbs initially preferentially on defect sites as the highest binding energy sites.…”

A multi-technique study of CO2 adsorption on Fe3O4 magnetite

“…Surface defects such as oxygen vacancies tend to bind CO 2 more strongly than the regular surface, 13 and CO 2 adsorption can therefore be used as a quantitative probe of the defect concentration. 14 To date there are no investigations of CO 2 adsorption on well-defined iron-oxide surfaces, despite the important role of these materials in both geochemistry and catalysis. Work on polycrystalline Fe 3 O 4 , 15 Fe 3 O 4 nanoparticles, 16 and FeO x nanoclusters on graphite 17 suggests however that both physisorption and carbonate formation can a) E-mail address: parkinson@iap.tuwien.ac.at occur, with stronger binding linked to the presence of Fe 2+ cations.…”