Master Thesis

PUBDB-2025-04411

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Coherent x-ray diffraction imaging of a single PtRh nanocatalyst under operando condition

Bachmann, L. J. (Corresponding author)Extern*DESY* ; Stierle, A. (Thesis advisor)DESY* ; Keller, T. F. (Thesis advisor)DESY*

2022
Universität Hamburg Hamburg

Abstract: Catalysts have a wide field of applications, for example, they play an important rolein producing chemicals and for renewable energies. Thus it is of great interest tomake them more efficient and to increase their lifetime. Therefore it is necessary tounderstand the changes inside a catalyst during the catalysis.In this thesis, a PtRh nanocatalyst is characterized by scanning electron microscopy(SEM), energy dispersive x-ray analysis (EDX), atomic force microscopy (AFM)and x-ray diffraction (XRD). With SEM and AFM information about the shapeof the nanoparticle (for example diameter and height) was collected, while EDX andXRD give information about the composition of the nanoparticle. After this precharacterization,the same nanocatalyst is investigated with Bragg coherent diffractionimaging (BCDI) to shed light onto shape and strain changes under operandoconditions. A pressure of 100mbar was used with a total gas flow of 50mLmin−1and cycles of CO, CO with O2 and only O2. After this catalysis experiment, thenanocatalyst was investigated with the same techniques as before. Additionally, thesample was also measured by x-ray photoelectron spectroscopy (XPS) and scanningAuger microscopy (SAM) to get more information about the chemical state of thenanocatalyst.The investigated nanoparticle had a diameter of 146nm with a height of 97nm beforeand 103nm after the catalysis experiment. Over the course of several gas cycles, theformation of two new facets could be observed. Additionally, the particle was foundto be twinned horizontally and it was possible to investigate both twins with BCDI.The strain at the twin boundary was higher under catalytic conditions (CO plus O2)than under pure CO or pure O2.1

Note: Masterarbeit, University of Hamburg, 2022

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Contributing Institute(s):

1. Nanolab (FS-NL)

Research Program(s):

1. 632 - Materials – Quantum, Complex and Functional Materials (POF4-632) (POF4-632)
2. NEP - Nanoscience Foundries and Fine Analysis - Europe|PILOT (101007417) (101007417)
3. SFB 1441 A05 - Struktur und Zusammensetzung von PtPd Modellkatalysatoren unter operando Bedingungen: Experiment und Theorie (A05) (446698573) (446698573)

Experiment(s):

1. DESY NanoLab: Microscopy
2. DESY NanoLab: Sample Preparation

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