Application of Fourier Transforms to time-resolved ambient pressure spectroscopy operando studies of CO oxidation over Pt(111)

Sammanfattning: The study of heterogeneous catalysis has important implications in increasing the efficiency of industrial processes and in reducing the emissions of greenhouse gases from sources such as automobiles. A reaction with high industrial relevance is the oxidation of CO on noble metal catalysts. In this work I apply Fourier Transformations to Ambient Pressure X-ray and Ultraviolet Photoelectron Spectroscopy and use this to study in situ CO oxidation over Pt(111) under pressure oscillation conditions generated by periodic dosing of CO pulses, with total pressure in the mbar regime, and at catalytic temperatures on the order of 580 +/- 40 K. I demonstrate a high sensitivity of the method by showing evidence that 97% of the surface structure is static while 3% oscillates back and forth between different structural phases and show evidence that a fraction of the surface consistently becomes clean of adsorbates during the surface structure oscillations. Further, I demonstrate that Fourier Transformation-based methods provide excellent resolution in determining the work function shift impressed upon gas-phase species by structural oscillations on the catalyst surface. I confirm the ability of the new methods to discern the reaction mechanism of CO oxidation on Pt(111) for specific reaction conditions. Finally, I demonstrate the ability of Fourier Transform-based techniques to quantify the variation in catalyst electronic structure and discuss potential future developments for the methods employed. In the long run, this thesis helps with the validation and development of a potentially-valuable new analytic method for in situ heterogeneous catalysis studies.