Lecture

Van Marum Colloquium: Catalysis and Electrocatalysis Insight from Planar Model Studies: Applications of in-situ STM and NAP-XPS

Prof. Jeppe Vang Lauritsen (Aarhus University)

Date: Thursday 26 June 2025
Time: 15:30 - 16:30
Location: Gorlaeus Building
Einsteinweg 55
2333 CC Leiden
Room: CM.3.23

Abstract

A fundamental understanding of heterogeneous catalysts and electrocatalysts can be accessed by focusing on what happens at the atomic level on surfaces. Surface science techniques, such as Scanning Tunneling Microscopy (STM) and X-ray Photoelectron Spectroscopy (XPS) are excellent methods in this regard, since they allow us to image surfaces in atomic detail and characterize chemical interactions – sometimes even at elevated pressure conditions.

Here, I will give examples of how we use near-ambient-pressure scanning tunneling microscopy (NAP-STM) to investigate Cu surfaces in atomic detail. Cu(110) is not reactive to CO₂ in vacuum conditions, but when the pressure is raised, the surface structure converts, leading to a high Cu mobility and creation of Cu-carbonate complexes¹. For CuZn alloys on Cu(111), which is a candidate for the active surface in industrial methanol synthesis, the response is quite different. Here the surface is stable in CO₂, but for CO containing gases at mbar pressure, Zn atoms are abstracted from the alloy, leading to a destabilization^{1, 2}. In electrocatalysis studies, we have developed a model system that incorporates Co₁ single atom sites in a monolayer carbon-nitride on Au(111) as an example of a single-atom catalyst³. Using an electrochemical cell seamlessly connected to the STM system, we can monitor the reactivity and investigate the characteristic structural changes and (lack of) stability of resulting from contact to the electrochemical environment. Moreover, we have developed a dip-and-pull method to access the surface properties of porous Ni foam electrodes used in alkaline water electrolysis using operando near-ambient-pressure XPS (NAP-XPS)⁴. In combination with planar model electrodes, we find that the intrinsic activity of Fe-doped Ni is strongly affected by surface roughness, which we attribute to beneficial formation of the active Ni(Fe)OOH phase at edge sites of the Ni(111).

References

Jensen, S.; et al. Role of Cu Oxide and Cu Adatoms in the Reactivity of CO₂ on Cu(110). Angewandte Chemie International Edition 2024, 63 (33), e202405554.
Jensen, S.; et al. Visualizing the gas-sensitive structure of the CuZn surface in methanol synthesis catalysis. Nature Communications 2024, 15 (1), 3865.
Gammelgaard, J. J.; et al. A Monolayer Carbon Nitride on Au(111) with a High Density of Single Co Sites. ACS Nano 2023, 17 (17), 17489-17498.
Chalil Oglou, R.; et al. Operando Characterization of Porous Nickel Foam Water Splitting Electrodes Using Near-Ambient Pressure X-ray Photoelectron Spectroscopy. The Journal of Physical Chemistry Letters 2025, 16 (14), 3597-3605.