Lecture

Reedijk Symposium 2024: Application of X-ray spectroscopy to attain a molecular understanding of the electrochemical interface

Sheena Louisia

Date: Friday 22 November 2024
Time: 10:10 - 10:25
Location: Lecture Hall
Einsteinweg 57
2333 CC Leiden
Room: C1

Authors

Sheena Louisia, Rik Mom, Marc Koper

Abstract

Electrochemical systems such as batteries, fuel cells, and electrolyzers critically depend on the molecular-scale processes that occur at the interface between the electrode and the electrolyte of the cell. Recent work has shown that the interactions between the ions from the electrolyte and the adsorbates on the electrode surface play an important role in these processes.^1,2 I will present an X-ray spectroscopy strategy that can resolve the ion-electrode interactions where in situ X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) are used in a so-called “dip-and-pull” geometry (Fig. 1). Taking the example of an aqueous 50 mM KCl electrolyte near an Au electrode, I will show how the application of in situ XPS and XAS can provide insights into the configuration of the first molecular layers of the electrolyte near the electrode surface. While In situ XPS monitors the concentration and potential of the cations (K⁺) and anions (Cl^-), XAS yields information about their water solvation shell. Using these insights, we uncover the potential response of both surface adsorbed and free solvated ionic species. We show that our strategy not only resolves the presence of adsorbed species on the electrode surface, i.e., Au-Cl, but we can also simultaneously characterize the impact of those adsorbates on the potential response of all species in the electrolyte, i.e., K⁺ ,Cl^-, and H₂O. Applied to the interfaces found in a practical device, we foresee this approach will help deconvolute the contribution of the electrode from the electrolyte composition on the overall performance of an electrochemical process, be it the charging/discharging of a battery or the electrochemical production of H₂ from water.

Figure 1. Schematic of the dip-and-pull geometry combined with XPS to monitor changes in the composition of the double layer and TEY-XAS to identify changes in ions’ coordination environment.

References

Goyal,A., et al. Cooperative Effect of Cations and Catalyst Structure in Tuning Alkaline Hydrogen Evolution on Pt Electrodes. Journal of the American Chemical Society, 2024. 146.11: 7305-7312.
Monteiro, M.CO, et al. Absence of CO2 electroreduction on copper, gold and silver electrodes without metal cations in solution. Nature Catalysis, 2021. 4.8: 654-662.