ESCA studies of chemical shifts for metal oxides

Reproducibility of highly active Au/TiO2 catalyst preparation and conditioning

“…Fits of the Au 4f peaks of the redox conditioned and reductively conditioned samples show metallic Au as main component and small contributions of Au 3+ species, which appear at 1.9 eV higher BE, at values of 85.7-86.0 eV, independent of conditioning procedure or gold loading. These values agree well with those reported by Holm and Storp [31] and Dickenson et al [32].…”

Stability and deactivation of unconditioned Au/TiO2 catalysts during CO oxidation in a near-stoichiometric and O2-rich reaction atmosphere

“…3, right panel), all samples exhibited a broad (FWHM ∼1.5 eV), slightly asymmetric signal with maximum Au(4f 7/2 ) peaks at about 84.4 eV for the catalyst before reaction and 84.4/84.3 eV after reaction at 30 and 80 • C, respectively. The peak shift and the broadening of the Au(4f) peak can originate from coexistent cationic and metallic Au species (initial state effect) [12,36] and/or the very small size of the metallic Au particles (final state effect) [37]. In a recent in situ XPS study on a unconditioned catalyst, which equally yielded broad, up-shifted Au(4f) peaks, the authors explained the peak structure by one state at 84.3 eV and an additional, broader component centered at 85.2 eV, indicative of two Au species that they described as nonionic [14].…”

Mesoporous Au/TiO2 Catalysts for Low Temperature CO Oxidation

“…Survey spectra (not shown) show peaks related to Ti, O and Au as well as some C. Detail spectra recorded in the Ti(2p) (not shown) and Au(4f) regions reveal the following trends: The Ti(2p) spectra show completely oxidized Ti 4+ species (459.2 eV [29]). For all catalysts, Au is present mainly as metallic Au 0 , (84.0 ± 0.1 eV) [29] with Au 3+ (85.9 ± 0.1 eV) 10 20 [35,36] contributions of *2% and *4% for Au/TiO 2 based on the P25 and on the mesoporous TiO 2 support, respectively (Fig. 3).…”