In Situ and Operando X-ray Scattering Methods in Electrochemistry and Electrocatalysis

Abstract

Published as part of Chemical Reviews virtual special issue "Operando and In Situ Studies in Catalysis and Electrocatalysis".

Shedding Light on Electrocatalysts: Practical Considerations for Operando Studies with High‐Energy X‐Rays

“…[34] Grazing-incidence X-ray diffraction (GI-XRD) extends this capability to study surface structures and the electrode-electrolyte interface of e. g. single crystals and thin-film samples. [35] Smallangle X-ray scattering (SAXS) yields structural information on the nanoscale, as large objects scatter X-rays to smaller angles. This enables studies of e. g. nanoparticle sizes and size distributions, particle shapes, and particle ordering or aggregation.…”

“…Only a few literature reviews of the cells used for operando characterization of electrocatalysts are available. [35,62] To give the reader an overview of currently used cells, various published designs have been compiled in Table 1. Based on the beam path through the cell, one can categorize transmission and grazing incidence cells.…”

“…[85] X-ray beam-induced changes can occur in liquid electrolytes, polymer membranes, and also the catalyst material. [35] Recently, a row of studies on beam damage in operando battery experiments has been published, which aim to elucidate the effects and underlying mechanisms of X-ray beam damage, providing a great resource for a larger research community. [86,[88][89][90] Beam-induced effects are mainly a result of the photoelectric effect leading to local heating due to absorption, creation of excited states, and emitted free electrons.…”

“…[89,90] Measuring multiple spots with different dosages not only helps to mitigate beam modulation effects but also enables a reproducibility check. [35] To assess the sample's beam stability carefully, it is important to test the stability of the sample and all other cell components when irradiated, e. g. by extended beam exposure without applied potential or by repeat measurements, and to monitor any artifacts arising in the electrochemical data resulting from beam modulation, which were not present in a blank experiment performed without the beam. [83] Furthermore, careful consideration must be given to how electrochemical measuring conditions influence catalyst restructuring.…”

Ultrafast Electronic and Vibrational Spectroscopy of Electrochemical Transformations on a Metal-Oxide Surface during Oxygen Evolution Catalysis

“…Further, during catalysis, interfacial strain can be coincident with catalyst restructuring. Calculations often predict new structural phases close to OER associated with catalyst restructuring. − Recently, with the advent of operando X-ray scattering techniques, the strain can be measured atomically as a function of reaction conditions during catalysis . However, while these examples associate strain to catalysis either by material engineering prior to the catalysis or the stable phase that arises because of the catalysis, it would be important to understand how the strain arises dynamically as intermediates form.…”