Abstract
This minireview aims at providing a complete survey concerning the use of X-ray absorption spectroscopy (XAS) for time-resolved studies of electrochemical and photoelectrochemical phenomena. We will see that time resolution can range from the femto-picosecond to the second (or more) scale and that this joins the valuable throughput typical of XAS, which allows for determining the oxidation state of the investigated element, together with its local structure. We will analyze four different techniques that use different approaches to exploit the in real time capabilities of XAS. These are quick-XAS, energy dispersive XAS, pump & probe XAS and fixed-energy X-ray absorption voltammetry. In the conclusions, we will analyze possible future perspectives for these techniques.
Highlights
The research of efficient materials in chemistry and physics requires new criteria for their rational design and the definition of new paradigms for the elucidation of structureperformance guidelines.In catalysis, the investigation on reaction mechanisms and on the concomitant changes in the catalyst nature becomes crucial
XANES gives important information on the coordination environment. This is the X-ray Absorption Near Edge Structure (XANES), that is due to electronic transitions to
In the field of semiconducting oxides, Santomauro and co-workers extended the investigation of Ritmann et al by performing the X-ray absorption spectroscopy (XAS) experiment at an XFEL facility to probe the dynamics of the trapping of the photogenerated electrons in TiO2 [40]
Summary
The research of efficient materials in chemistry and physics requires new criteria for their rational design and the definition of new paradigms for the elucidation of structureperformance guidelines. The quest for analytical tools capable of directly detecting any information on the reactant-intermediate-product sequence and on the catalyst role in the course of the reaction is imperative In this respect, operando spectroscopies are obviously central, since they can assume the role of an independent, uncoupled source of information with respect to the primary ones (such as products yield, selectivity, or potential/current characteristics in the case of electrochemistry). Despite the need of large-scale synchrotron radiation facilities, it provides fundamental information on the local electronic and atomic structure of a selected element The latter characteristic is one of the most intriguing for XAS: tuning the energy of the incident X-ray beam, it is possible to select the Surfaces 2018, 1, 138–150; doi:10.3390/surfaces1010011 www.mdpi.com/journal/surfaces. Is independent on any element in the beam different from that under investigation Another enabling feature of XAS is the high energy of X-rays: especially in the so-called “hard”.
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