Senior Lecturer Jan Knudsen, Synchrotron Radiation Research, Lund University

Dynamic catalyst surfaces at work studied with ambient pressure x-ray photoelectron spectroscopy

Ambient pressure x-ray photoelectron spectroscopy (APXPS) is an excellent in-situ characterization technique for catalyst surfaces as it is able to characterize the surface, adsorbates, and the gas-phase just above the surface simultaneously while a chemical reaction is running. Unfortunately, the technique is slow with seconds or minutes of acquisition time per spectrum. This has until now limited its use to identify the equilibrium and majority phases present on the surface while the catalyst is active.

In this talk, I will use scientific case stories to demonstrate how this limitation can be overcome by new method development now available at the MAX IV laboratory. First of all, I will show how the construction of event-averaged data from stroboscopic APXPS data acquired in a cyclic reaction environment, established with transient gas supply, can be used to achieve ms-µs time-resolution [1-3]. Using this methodology, I will demonstrate how we can identify short lived phases, their catalytic function, and what triggers surface reconstruction. Secondly, I will present a new method that selectively probe phases that oscillate on the surface and link this to oscillations observed in the gas phase, while spectator species on the surface and in the gas phase are filtered away. In short, this new method is based on Fast Fourier transformation of stroboscopic APXPS data acquired also in in a cyclic reaction environment.

[1] Knudsen et al., Nat. Comm. 12, 6117 (2021)
[2] Shavorskiy et al., ACS Appl. Mater. Interfaces, 13, 47629 (2021)