In situ/Operando studies of electrocatalysts using hard X-ray spectroscopy

Abstract

This review focuses on the use of X-ray absorption and emission spectroscopy techniques using hard X-rays to study electrocatalysts under in situ/operando conditions. We describe the importance and the versatility of methods in the study of electrodes in contact with the electrolytes, when being cycled through the catalytic potentials during the progress of the oxygen-evolution, oxygen reduction and hydrogen evolution reactions. The catalytic oxygen evolution reaction is illustrated with examples using Co, Ni and Mn oxides, and Mo and Co sulfides are used as an example for the hydrogen evolution reaction. A bimetallic, bifunctional oxygen evolving and oxygen reducing Ni/Mn oxide is also presented. The various advantages and constraints in the use of these techniques and the future outlook are discussed.

Trends of epitaxial perovskite oxide films catalyzing the oxygen evolution reaction in alkaline media

“…In situ X-ray diffraction has been used to study the structure and its evolution with potential for epitaxial oxides [154][155][156] but not perovskite oxides. In situ X-ray spectroscopy is used to elucidate the valence during OER for other catalysts but has not been used for epitaxial thin film oxides [157][158][159][160]. These in situ measurements are instrumental to understand the OER on epitaxial perovskite oxides and fully harness their potential as model electrodes to derive guidelines to improve their electrocatalysis by optimizing the composition or by exploiting new concepts inherent to epitaxial layers.…”

The Journey toward Low Temperature, Low Pressure Catalytic Nitrogen Fixation

“…[ 69 ] Surface sensitive spectroscopic methods such as surface‐enhanced infrared absorption spectroscopy have offered valuable insights about reaction pathways. [ 70 ] In situ and operando characterization techniques with high chemical sensitivity and improved time resolution are needed for deeper understanding of NRR mechanisms. [ 71 ]…”

Emerging trends in metal oxide electrocatalysis: Bifunctional oxygen catalysis, synergies and new insights from in situ studies

“…X-ray methods have a stellar record in heterogeneous catalysis and their application to electrocatalysts for the OER has recently seen a remarkable expansion. In situ and operando X-ray methods play a particularly important role as they can interrogate the catalyst in its functional form and under operating conditions [42] .…”