Dissertation

Employing and Developing Operando Scanning Tunneling Microscopy for Fischer-Tropsch Synthesis

This thesis investigates catalytic reactions at the atomic scale using scanning tunneling microscopy (STM), with a focus on Fischer–Tropsch synthesis, a key industrial process that converts hydrogen and carbon monoxide into liquid fuels.

Author: E. Motaee
Date: 16 January 2026
Links: Thesis in Leiden Repository

The central aim is to understand how cobalt catalyst surfaces evolve and function under realistic reaction conditions.Chapter 3 examines cobalt surfaces at room and elevated temperatures. At low temperatures, carbon monoxide adsorbs molecularly and slightly roughens the surface. At high temperatures, carbon reorganizes into a graphite-like layer that alters surface structure and reactivity. Under reaction conditions, the system exhibits striking oscillatory behavior: gas concentrations and product formation pulse rhythmically. These oscillations occur only when both hydrogen and carbon monoxide are present, suggesting that transient carbon clusters periodically block and unblock active sites, dynamically reshaping the surface.Chapter 4 explores oxidized cobalt surfaces, showing that oxidation strongly suppresses activity at room temperature. Although carbon monoxide can partially reduce the surface at higher temperatures, full catalytic performance is not recovered, highlighting the lasting impact of oxygen contamination.Chapter 5 demonstrates that rhenium promotion improves cobalt reducibility and stability, particularly in the presence of water, which otherwise raises activation temperatures. Chapter 6 presents the design of a high-pressure, high-temperature STM capable of operando studies, integrating advanced heating concepts and fluid-flow considerations. Overall, the thesis reveals catalytic surfaces as dynamic systems shaped by chemistry, temperature, and reactor physics.