@misc{BoehnWeissbachKrisponeitetal., author = {Boehn, Bernhard von and Weißbach, Anton and Krisponeit, Jon-Olaf and Flege, Jan Ingo and Falta, Jens and Gregoratti, Luca and Amati, Matteo and Zeller, Patrick and Imbihl, Ronald}, title = {Phase Separation within Vanadium Oxide Islands under Reaction Conditions: Methanol Oxidation at Vanadium Oxide Films on Rh(111)}, series = {The Journal of Physical Chemistry C}, volume = {126}, journal = {The Journal of Physical Chemistry C}, number = {45}, issn = {1932-7455}, doi = {10.1021/acs.jpcc.2c04174}, pages = {19101 -- 19112}, abstract = {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) Moir{\´e}-type boundary layer and a reduced core exhibiting a (√3 × √3)R30° Moir{\´e} 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.}, language = {en} } @misc{BoehnPenschkeLietal., author = {Boehn, Bernhard von and Penschke, Christopher and Li, Xiaoke and Paier, Joachim and Sauer, Joachim and Krisponeit, Jon-Olaf and Flege, Jan Ingo and Falta, Jens and Marchetto, Helder and Franz, Torsten and Lilienkamp, Gerhard and Imbihl, Ronald}, title = {Reaction dynamics of metal/oxide catalysts: Methanol oxidation at vanadium oxide films on Rh(111) from UHV to 10-2 mbar}, series = {Journal of Catalysis}, volume = {385}, journal = {Journal of Catalysis}, issn = {0021-9517}, doi = {10.1016/j.jcat.2020.03.016}, pages = {255 -- 264}, abstract = {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.}, language = {en} }