Unraveling the oxidation of Ru using XPS

Abstract

A method is presented to analyze XPS spectra recorded from thin (<5 nm) oxide layers with known thickness on corresponding metal substrates. With this method, the contribution of the oxide overlayer can be separated from the metal substrate for the metal core level line, even when the difference in binding energy between metallic and oxidic electrons is small. This method involves the fitting of Doniach-Sunjic (DS) line shapes for the metallic and oxidic state to the measured spectrum, where the area ratio between the metallic and oxidic contribution is fixed through the known thickness.The method was applied to ruthenium single crystals with a (0001) surface that were oxidized in a ultra-high vacuum (UHV) chamber at a temperature of 673 K and an oxygen pressure between 1×10 −4 and 1×10 −2 Pa. Analysis of the oxidic contribution to the Ru 3p 3/2 line shows that two different types of oxides can be formed in the oxidation process.

Characterization of a Spent Ru/C Catalyst after Gasification of Biomass in Supercritical Water

“…From our own measurements and in agreementwithliterature(seeTable3, [28][29][30][31][32][33][34] ) the 280.2 eV signal can be related to metallic ruthenium. This is in agreement with the detection of metallic ruthenium by in situ XAS measurements.…”

“…Some literature, see Table 3, label it 'RuO 3 ', however RuO 3 is described not to be stable as bulk compound. [40,41] More likely is the interpretation given by Over et al [33] and by Ernst and Sloof, [34] who show that because of the conductivity of RuO 2 the excitation of a plasmon leads to the observed satellite.…”

Acid‐Functionalized Mesoporous Carbon: An Efficient Support for Ruthenium‐Catalyzed γ‐Valerolactone Production

“…This species is attributed to Ru 4+ + ,m ostl ikely ar esult of RuO 2 -type oxides, whicha re the www.chemsuschem.org most stable oxides, and confirms the assignment from the Ru 3d data. [17,18] The second highest energy species, located at BE = 465 eV,i sl ikely caused by water bound to the surfaceo r as econd, higher oxidation state Ru species, which was observed on the as-preparedc atalysts. The reduction treatment had no clear influence on the ÀPÀOc hemistry but it changed the Sf unctionality dramatically.P ostsynthesis, there was ac lear partial reduction of the ÀSO 4 group (BE = 169.1 eV) to result in the formation of asurface sulfide (BE = 163.7 eV).…”

“…This shift is causedb yareduction of the Ru, though this reduction does not seem to resulti natotal reduction to Ru 0 .I nstead, theseB Es are consistent with the stabilization of oxidizedR us pecies with oxidation states around + +4. [17,18] To characterize the Ru oxidation state further,w ei nvestigated the Ru 3p spectra for the OMC-supported materialt hat had the highest surfacec ontent of Ru.…”

Combined experiment and theory approach in surface chemistry: Stairway to heaven?

“…A similar oxide thickness was derived from XPS [132] and STM studies [133]. From the l-scans in SXRD, which probes the structure normal to the surface, the RuO 2 (110) film surface is found to be very flat, i.e.…”