In-situ x-ray and electrochemical characterisation of energy materials

The development of new materials for electrocatalysis is of central importance for clean energy applications. Whilst the design of new active and stable electrode materials is a key activity, it is recognized that the electrolyte side of the electrochemical interface plays an equally important role as reactants must pass through the electric double layer that is formed

at the interface in order to reach the reaction sites. In particular it has been shown that the cations of the electrolyte can greatly change the rates and reaction selectivity of many electrocatalytic processes and this is currently a hot research topic in electrochemistry [1-2]. Although electrochemical reactions always involve charge transfer processes, the applied

potential can also induce structural rearrangement without charge transfer [3]. Examples include processes such as metal surface relaxation and surface reconstruction but also double layer charging which leads to rearrangement on the electrolyte side of the interface. Electrochemical surface science is a field that has grown both from theoretical and

experimental advances, the latter driven by the development of techniques that can probe the electrode structure under the electrolyte and during electrochemical reactions, known as

in-situ or operando measurements. Surface X-ray diffraction (SXRD) utilizing synchrotron X-ray radiation has been prominent in the study of single crystal metal surfaces in the electrochemical environment and has been particularly successful in identifying structural changes on the metal side of the interface. In terms of ordering in the liquid side of the

interface, measurement and modelling of the specular crystal truncation rod (CTR) scattering is one of the few methods that can probe the entire interface structure. This has been elegantly demonstrated in the studies of water and cation ordering on mineral surfaces [4]. Raman spectroscopy is widely used in the field of organic, polymer chemistry, polymer physics

and physical chemistry. This technique also has a number of applications in the study of electrochemical systems, for example related to applications in batteries and hydrogen fuel cells. Particularly striking in this field has been the use of shell-isolated nanoparticles for enhanced Raman spectroscopy (SHINERS). Raman spectroscopy is an inherently weak

technique, with only 1 in 10 million photons being inelastically scattered. By covering the surface of an electrode in shell-isolated nanoparticles, it is possible to obtain surface enhancements from the substrate directly and track surface reactions, such as the oxygen reduction reaction (ORR), by the detection of reaction products [5].

This project aims to characterise the physical properties of these energy materials, by preparing single crystal electrode surfaces and different electrolyte solutions. The interactions between these will be studied using Cyclic Voltammetry and be combined with SXRD studies which will be carried out by using X-Ray Synchrotron Radiation provided by the

Diamond Light Source, Oxfordshire, UK and the UK funded BM28, the XMaS beamline at the ESRF, Grenoble, France. Further information from the electrochemical processes will be obtained after the installation of the brand-new Raman spectroscopy probe in the XMaS beamline which will complement the SXRD studies.

References: [1] M. M. Waegele et al., Journal of Chemical Physics, 2019, 151, 160902. [2] A. H. Shah et al., Nature Catalysis, 2022, 5, 923. [3] Y. Grunder and C.A. Lucas, Current Opinion in Electrochemistry, 2020, 19, 168. [4] P. Fenter and N.C. Sturchio, Progress in Surface Science, 2005, 77, 171.

[5] R. Rizo et al., Nature Communications, 13, 2550 (2022