TY - GEN A1 - Boehn, Bernhard von A1 - Weißbach, Anton A1 - Krisponeit, Jon-Olaf A1 - Flege, Jan Ingo A1 - Falta, Jens A1 - Gregoratti, Luca A1 - Amati, Matteo A1 - Zeller, Patrick A1 - Imbihl, Ronald T1 - Phase Separation within Vanadium Oxide Islands under Reaction Conditions: Methanol Oxidation at Vanadium Oxide Films on Rh(111) T2 - The Journal of Physical Chemistry C N2 - Submonolayer coverages of V-oxide on Rh(111) condense during catalytic methanol oxidation into a pattern of macroscopic stripes or islands. Under reaction conditions, a phase separation occurs within the VOx islands that has been studied in a pressure range of 10–6–10–4 mbar with photoemission electron microscopy (PEEM), low-energy electron microscopy (LEEM), microspot-low-energy electron diffraction (μLEED), and microspot-X-ray photoelectron spectroscopy (μXPS). An oxidized outer ring with a (√7 × √7)R19.1° structure coexists with an inner (12 × 12) Moiré-type boundary layer and a reduced core exhibiting a (√3 × √3)R30° Moiré type pattern. The dependence of the substructure on the reaction conditions, on V coverage, and on island size was investigated. With μXPS, the V coverages of the different phases in the VOx islands were determined. KW - Methanol Oxidation KW - Vanadium Oxide KW - Photoemission electron microscopy (PEEM) KW - Low-energy electron microscopy (LEEM), KW - Microspot-low-energy electron diffraction (μLEED) KW - Microspot-X-ray photoelectron spectroscopy (μXPS) Y1 - 2022 U6 - https://doi.org/10.1021/acs.jpcc.2c04174 SN - 1932-7455 SN - 1932-7447 VL - 126 IS - 45 SP - 19101 EP - 19112 ER - TY - GEN A1 - Boehn, Bernhard von A1 - Penschke, Christopher A1 - Li, Xiaoke A1 - Paier, Joachim A1 - Sauer, Joachim A1 - Krisponeit, Jon-Olaf A1 - Flege, Jan Ingo A1 - Falta, Jens A1 - Marchetto, Helder A1 - Franz, Torsten A1 - Lilienkamp, Gerhard A1 - Imbihl, Ronald T1 - Reaction dynamics of metal/oxide catalysts: Methanol oxidation at vanadium oxide films on Rh(111) from UHV to 10-2 mbar T2 - Journal of Catalysis N2 - Recent advances in in situ microscopy allow to follow the reaction dynamics during a catalytic surface reaction from ultra-high vacuum to 0.1 mbar, thus bridging a large part of the pressure gap. Submonolayer vanadium oxide films on Rh(111) have been studied during catalytic methanol oxidation in situ with spatially resolving imaging techniques. At 10-6 to 10-4 mbar VOx condenses into macroscopic circular islands that exhibit a substructure, consisting of a reduced island core and an oxidized outer ring. This substructure arises due to an oxygen gradient inside the VOx islands, which results in different coexisting 2D-phases of VOx on Rh(111). This substructure is also responsible for a "breathing-like" oscillatory expansion and contraction that the islands undergo under stationary conditions. Using density functional theory, the 2D-phase diagram of VOx on Rh(111) has been computed. The oscillatory behavior can be understood as a periodic phase transition between two 2D phases of VOx. With a newly developed near ambient pressure – low-energy electron microscope, it was shown that VOx islands disintegrate at 10-2 mbar, resulting in turbulent dynamics. KW - Vanadium oxide KW - Methanol oxidation KW - Inverse catalyst KW - Restructuring KW - Near ambient pressure low-energy electron microscope KW - Heterogeneous catalysis KW - Pressure gap Y1 - 2020 U6 - https://doi.org/10.1016/j.jcat.2020.03.016 SN - 0021-9517 SN - 1090-2694 VL - 385 SP - 255 EP - 264 ER -