Revisiting Optical Reflectance from Au(111) Electrode Surfaces with Combined High-Energy Surface X-ray Diffraction

Weronica Linpé,Lisa Rämisch,Leon Jacobse,Giuseppe Abbondanza,Sebastian Pfaff,Johan Zetterberg,Edvin Lundgren,Gary S Harlow,Andreas Stierle,Lindsay Merte,Ulrich Lienert,Alfred Larsson,Zoltan Hegedues

doi:10.1149/1945-7111/ac2702

Abstract

We have combined high-energy surface X-ray diffraction (HESXRD) with 2D surface optical reflectance (2D-SOR) to perform in situ electrochemical measurements of a Au(111) electrode in 0.1 M HClO4 electrolyte. We show that electrochemically induced changes to Au(111) surface during cyclic voltammetry can be simultaneously observed with 2D-SOR and HESXRD. We discuss how small one atom high 1x1 islands, accommodating excess atoms after the lifting of the surface reconstruction, can lead to discrepancies between the two techniques. The use of HESXRD allows us to simultaneously detect parts of the truncation rods from the (1 × 1) surface termination and the p x √3 electrochemically induced surface reconstruction, during cyclic voltammetry. The presence of reconstruction phenomena is shown to not depend on having an ideally prepared surface and can in fact be observed after going to very oxidizing potentials. 2D-SOR can also detect the oxidation of the Au surface, however no oxide peaks are detected in the HESXRD signal, which is evidence that any Au oxide is X-ray amorphous.

Highlights

To cite this article: Weronica Linpé et al 2021 J
The X-ray beam damage is is a straight line across the sample because the sample was held still at a constant position, where both the super lattice rods (SLRs) and herringbone reconstruction (HB) were visible in the high-energy surface X-ray diffraction (HESXRD) image, during the whole measurement
Since the features are reproducicable and we see no significant difference in the HESXRD results between the earlier cycles and the later cycles where they diverge, we assume that our HESXRD results are valid in this case

Summary

Introduction

To cite this article: Weronica Linpé et al 2021 J. In situ studies of electrocatalysts under reaction conditions are essential for understanding the impact of structure upon catalytic performance.[2] Electrochemical techniques such as: cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Galvano/Potentiostatic, and differential capacitance measurements have been extensively used to understand processes such as: adsorption, reaction rates, interfacial charge, reaction onsets, and catalyst degradation. High-energy surface X-ray diffraction (HESXRD) has been shown to allow more rapid mapping of reciprocal space under reaction conditions,[3,4] and has been combined with electrochemistry to study oxide formation on Pt single crystals.[5] The surface structure of Au(111) single crystals under electrochemical conditions has been extensively studied by STM6–10 and SXRD.[11,12,13,14] It is well-known that the topmost atomic surface layer of Au(111) can reconstruct. Various peaks in the CV of Au(111) electrodes have been attributed to the lifting of the surface reconstruction, but the interpretation is often obscured by simultaneous anion adsorption.[18,19,20] The thermal-induced reconstruction (i.e. from flame annealing) lifts at higher potentials whereas the more defect rich potential-induced reconstruction lifts at slightly lower potentials.[20,21]

Results

Discussion

Conclusion