During recent years, 2D Surface Optical Reflectance (2D-SOR) [1,2] microscopy [3] has emerged as a valuable surface characterization tool for model catalysts or electrodes [4] when performing operando investigations in harsh environments. In particular, 2D-SOR microscopy is favorably used as a complementary technique to other photon-in-photon-out techniques which do not carry direct information on the surface 2D morphology. In this presentation we will present the development and examples of 2D-SOR instrumentation and investigations from single and poly-crystalline samples in combination with Planar Laser Induced Fluorescence (PLIF) [2, 3], High Energy Surface X-Ray Diffraction (HESXRD) [5,6,7] and Polarization Modulation-Infrared Reflection Absorption Spectroscopy (PM-IRRAS) [8] coupled to Mass Spectrometry (MS) and Cyclic Voltammetry (CV) in thermal catalysis, electrocatalysis and corrosion.

Illustrating examples of the versatility of the technique will be shown including reflectance changes during the thermal CO oxidation over Pd(100) and Pd polycrystalline surfaces. We show that reflectance changes during the reaction can be associated with the formation of thin Pd oxides by the combination of 2D-SOR and Surface X-Ray Diffraction (SXRD). The combined measurements demonstrate a sensitivity of 2D-SOR to the formation of a 2-3 Å thin Pd oxide film.

During Cyclic Voltammetry (CV) in an acidic electrolyte using a Au(111) surface as an electrode, we show that the differential of the change in 2D-SOR reflectance correlate to various current features in the CV curve. This observation can be used to differentiate current features in the CV curve from a polycrystalline Au surface, demonstrating that the different grains contribute to the current at different potentials due to the different surface orientations.

Finally, we show that 2D-SOR is a cheap and useful technique to investigate the corrosion of applied materials such as duplex stainless steels and Ni alloys.

Graphics: a) The 2D-SOR experimental setup for thermal catalysis. b) Side view of the electrochemical flow-cell showing the electrode configuration and a window at the top for the 2D-SOR LED light.

References

[1] W. G. Onderwaater et al Rev. Sci. Instrum., 88 (2017) 023704.

[2] J. Zhou et al, J. Phys. Chem. C 121 (2017) 23511.

[3] S. Pfaff et al, ACS Appl. Mater. Interfaces 13 (2021) 19530.

[4] W. Linpe, et al, Rev. Sci. Instrum., 91 (2020) 044101.

[5] S. Pfaff, et al Rev. Sci. Instrum. 90 (2019) 033703.

[6] S. Albertin, et al, J. Phys. D: Appl. Phys. 53 (2020) 224001.

[7] W. Linpé, et al J. Electrochem. Soc. 168 (2021) 096511.

[8] L. Rämisch et al, Appl. Surf. Sci. 578 (2022) 152048