On the Chemical Romance Between Gas and Surface, and how to Illuminate it

Pfaff, SebastianLund University,Lunds universitet,Förbränningsfysik,Fysiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,LTH profilområde: Energiomställningen,LTH profilområden,Combustion Physics,Department of Physics,Departments at LTH,Faculty of Engineering, LTH,LTH Profile Area: The Energy Transition,LTH Profile areas,Faculty of Engineering, LTH (författare)

An increasing number of catalysis experiments are conducted at higher pressures to bridge the pressure gap. This means that we need to measure not only the sample surface but also the gas phase around the sample with spatial resolution. This thesis treats the development and applications of two optical techniques that can be used to image the surface of a model catalyst together with the surrounding gas: planar laser-induced fluorescence (PLIF) and 2D-surface optical reflectance (2D-SOR). The strengths and weaknesses of the techniques are discussed. Examples are used to show how the techniques can be applied to study active model catalysts \textit{in situ} under ambient pressure conditions. PLIF is used to image the CO and CO₂ concentrations around various Pd model catalysts during the CO oxidation reaction. 2D-SOR is used to show the surface oxidation process during the same reaction. We show how PLIF and 2D-SOR can be combined with additional techniques, primarily high-energy surface X-ray diffraction (HESXRD), thermography, mass spectrometry (MS) and polarisation modulation infrared reflection absorption spectroscopy (PMIRRAS).Finally, we show how PLIF and 2D-SOR can be used to bridge the so-called materials gap by taking advantage of the spatial resolution of the techniques to study polycrystalline samples. These samples, which exhibit a plethora of surface structures, can be seen as a step towards more industry-like samples.

NATURVETENSKAP Fysik Atom- och molekylfysik och optik hsv//swe
NATURAL SCIENCES Physical Sciences Atom and Molecular Physics and Optics hsv//eng
planar laser-induced fluorescence
surface optical reflectance
model catalysis
palladium
polycrystal
CO oxidation
heterogeneous catalysis
Fysicumarkivet A:2022:Pfaff

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