Table-Top Ultrafast Soft X-Ray Spectroscopy Toward Synchrotron-like In-Situ Photoelectrochemical Measurements

D. Nimlos, A. Arellano, L. Paradis-Fortin, K. Lewis, W. Drisdell, S.K. Cushing
California Institute of Technology,
United States

Keywords: X-ray spectroscopy, photoelectrocatalysis, in-situ X-ray measurements

Summary:

Photoelectrochemical reduction of CO2 to value-added fuels and feedstocks requires a comprehansive understanding of the reaction, spanning carrier dynamics, reaction mechanisms, and electrode degradation. Recent progress in in-situ X-ray capabilities have enabled the measurement of these processes in more realistic operating conditions, primarily within synchrotron facilities. Performing in-situ X-ray measurements on the table-top scale has remained a challenge in the field. Laser-produced plasma sources can extend into the soft X-ray energy range, covering the water window and potentially facilitating in-situ studies of photcatalysts. Nevertheless, their inherent source fluctuations have prevented ultrafast studies in the past. In this work, we employ methods pioneered by jogj-harmonic (HHG)-based extreme ultraviolet (XUV) table-top setups to create a novel laser-produced plasma technique for table-top time-resolved measurements in the soft X-ray regime (200 – 1000 eV). We combine EMCCD detection, background-free self-referencing, edge-referencing analysis, and other advances, to reduce shot-to-shot noise enabling the detection of sub-mOD. This presentation also describes the technical advances pioneered at synchrotron sources that have facilitated in-situ X-ray measurements of photoelectrochemical systems. These advancements have inspired the effort to achieve the first table-top soft X-ray measurements in device-relevant liquid environments, enabling the correlation of photocatalyst properties, such as electron and hole energies and polarons, with photoelectrochemical product formation.