New opportunities for studying catalytic reactions above and below 2D materials with x-ray photoelectron spectroscopy

Jan Knudsen

In this talk, I will discuss how graphene can be used to study catalytic reactions on surfaces. In the first example, I will discuss how graphene can be used as a dense positioning matrix to study and gain knowledge of the catalytic activity of different atomic H-cluster motifs [1]. In the second example, I will demonstrate how gas-composition pulses combined with ambient pressure photoelectron spectroscopy (APXPS) can be used to study chemical reactions in the confined space between a graphene film and a catalytically active Ir(111) substrate [2]. Hereby, gas delivery, undercover H₂ and CO oxidation, and product removal from the undercover region can be followed in situ and in a time-resolved manner.

As an outlook in my talk, I will discuss new methodologies for time-resolved APXPS we developed at the MAX IV laboratory. In particular, I will discuss: (i) Event-averaging [3-5] and power spectrum analysis of stroboscopic APXPS data acquired in a cyclic reaction environment established by transient gas supply. Using these new methodologies, I will demonstrate that ms - µs time-resolution can be reached and that it is possible to selectively probe phases that oscillate on the surface. We believe that these new methodologies open new avenues for time-resolved catalysis experiments both on metallic surfaces but also above and below 2D materials and this with hitherto unseen stroboscopic vision.

References (Press to find paper)

[1] Boix et al., J. Phys. Chem. C, 126, 14116 (2022)

[2] Boix et al., ACS catalysis 12, 9897 (2022)

[3] Knudsen et al., Nat. Comm. 12, 6117 (2021)

[4] Shavorskiy et al., ACS Appl. Mater. Interfaces, 13, 47629 (2021)

[5] Shavorskiy et al., Synchrotron Radiation News, 35, 4-10 (2022)