A comparative in situ XPS study of PtRuCo catalyst in methanol steam reforming and water gas shift reactions

Abstract

In the present study the oxidation state and the surface composition of a ternary PtRuCo catalyst were investigated under methanol steam reforming (SRM) and water gas shift (WGS) reaction conditions at 570 K. Ambient pressure X-ray photoelectron spectroscopy (APPES) was applied in situ at 0.5 mbar, while simultaneously monitoring the catalytic activity of the sample by on-line mass spectrometry. Non-destructive depth profile measurements performed under SRM reaction conditions over a polycrystalline PtCo foil, were also used to obtain detailed depth-resolved information. The results showed that surface segregation of cobalt and modification of its oxidation state occurs when switching from SRM to WGS reaction conditions. Evidence of ionic Pt was found only during WGS reaction, while Ru was mainly present in the metallic state. The results clearly demonstrate the dynamic response of the PtRuCo catalytic surface to the reaction atmosphere.

Is Steam an Oxidant or a Reductant for Nickel/Doped‐Ceria Cermets?

“…[25] Depth-dependent NAP-XPS measurements can be used to distinguish betweend efective/interstitial lattice sites, which should be enhanced at higher analysis depth,a nd surface-adsorbed hydroxyl species, which should increasea tl ower analysisd epth. [47] As shown in Supporting Information 6, the O1sp eak shape is not particularly influenced by the excitation photon energy,t hat is, the measurementi nformation depth. Accordingly,t he presence of as ignificant population of adsorbed oxygen species (i.e.…”

“…However, this does not necessarily rule out the induction of O 1s peak asymmetry by the presence of hydroxyl groups that remain adsorbed on the NiGDC surface, as proposed earlier in model ceria layer studies . Depth‐dependent NAP‐XPS measurements can be used to distinguish between defective/interstitial lattice sites, which should be enhanced at higher analysis depth, and surface‐adsorbed hydroxyl species, which should increase at lower analysis depth . As shown in Supporting Information 6, the O 1s peak shape is not particularly influenced by the excitation photon energy, that is, the measurement information depth.…”

Unravelling the effect of charge dynamics at the plasmonic metal/semiconductor interface for CO2 photoreduction

“…In ultra-high vacuum (UHV), the C1s signal of a fresh Ag/TiO 2 sample (Fig. 3a ) shows the presence of spurious carbon (C–C, 284.7 eV), as well as other contributions assigned to bicarbonate (HCO 3 − , 288.6 eV), carbonate (CO 3 2− , 289.5 eV) and other species containing C–O bonds (285.5 eV) 26 , 28 , 29 . In turn, the O1s region (Fig.…”

The Active State of Supported Ruthenium Oxide Nanoparticles during Carbon Dioxide Methanation

“…While this pressure is still below the typical operating pressure for the Sabatier reaction (1 bar), it is high enough to ensure the saturation of surface sites with adsorbates, thus making the measurement representative of the surface steady state in the catalytic reactor. This was demonstrated on a number of metal and metal oxide catalysts in the past ten years and by several groups, [19][20][21][22][23][24][25][26][27][28] and in particular for the reaction of catalytic CO oxidation on bulk ruthenium oxide. 29 It is more challenging but still possible to analyze surface ligands and adsorbates on nanoparticles.…”