Operando X-ray Photoelectron Spectroscopy for High-Pressure Catalysis Research Using the POLARIS Endstation

Figures & data

Figure 1. Illustration of a sustainable energy system to produce base chemicals for the industry and transportation fuel based on catalysis. Key processes are electrochemical water splitting and thermal and electrochemical CO₂ and N₂ reduction—graphics courtesy of Jakob Kibsgaard, DTU. An earlier version of this figure appeared in [1].

Figure 2. Illustrations of the POLARIS endstation. (a) The instrument on-site at beamline P22 at DESY, Germany. (b) A cut-through drawing of the front cone, which schematically illustrates the virtual cell concept. (c, d) Microscope images at two different zoom levels showing the array of apertures for the photoelectrons. (e) 3 D drawing of the instrument and the hexapod manipulator on which it stands. (f) Spectra of the Cu 2p region acquired at different pressures of He. The pressure and the integration times are indicated by the legend. The photon energy was 3.7 keV. The figure is adapted from Ref. [3].

Figure 3. Operando XPS study of CO oxidation on Pd(100). (a) An example of peak fitting for the Pd 3d_5/2 peak with two components, a metal peak based on pure components shown with a dotted line and an oxide with a dashed line. (b) Ratio of metal to oxide peak intensity as a function of angle with two calculated models. (c) Metallic Pd forms on top of PdO during the reaction. Reproduced from Ref. [10].

Figure 4: (a) Photon energy dependence of O 1 s XPS spectra after hydrogen treatment of oxidized Cu. The fitting results with blue: Cu₂O, green: O_Cu,vac, and orange: O_int. (b) The illustration of two different subsurface oxygen species, O_Cu,vac. and O_int., formed during oxide-derived Cu preparation, where a defect/vacancy rich surface is generated by Cu atom rearrangement under H₂ treatment in the chamber, and the lattice oxygen is dissolved from the oxide and then diffuses toward to surface as O_int. Reproduced from Ref. [18].

Figure 5: (a) An illustration of the chemical state of the Rh(111) surface. (b) A similar illustration for the Rh(211) surface. These are based on interpretations of the spectra shown in (c, d) of the C 1 s region at the Rh(111) and Rh(211) surfaces, respectively. In inset (e), a comparison of the two surface orientations is shown at 225 °C. The photon energy in the experiment was 4.6 keV, and the CO: H₂ was flown at a 1:2 ratio and 150 mbar pressure. Figures adapted from Ref. [28].

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