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

电催化新材料的开发对清洁能源的应用至关重要。虽然设计新的活性和稳定的电极材料是一个关键的活动，但人们认识到电化学界面的电解质侧起着同样重要的作用，因为反应物必须通过在界面上形成的双电层才能到达反应位点。特别是电解质的阳离子可以极大地改变许多电催化过程的速率和反应选择性，这是目前电化学领域的研究热点[1-2]。虽然电化学反应总是涉及电荷转移过程，但施加的电位也可以在没有电荷转移的情况下诱导结构重排。例子包括金属表面松弛和表面重建等过程，也包括导致界面电解质一侧重排的双层充电。电化学表面科学是一个从理论和实验两方面发展起来的领域，后者是由可以探测电解质下和电化学反应过程中的电极结构的技术的发展所驱动的，称为原位或操作测量。利用同步x射线辐射的表面x射线衍射（SXRD）在电化学环境下单晶金属表面的研究中占有突出地位，并特别成功地识别了界面金属侧的结构变化。在界面液体侧的有序方面，镜面晶体截断棒（CTR）散射的测量和建模是少数能够探测整个界面结构的方法之一。这在对矿物表面的水和阳离子排序的研究中得到了很好的证明。拉曼光谱广泛应用于有机化学、高分子化学、高分子物理和物理化学等领域。该技术在电化学系统的研究中也有许多应用，例如与电池和氢燃料电池相关的应用。在这个领域特别引人注目的是使用壳隔离纳米粒子增强拉曼光谱（SHINERS）。拉曼光谱是一种本质上很弱的技术，只有千万分之一的光子被非弹性散射。通过在电极表面覆盖壳隔离纳米颗粒，可以直接从衬底获得表面增强，并通过检测反应产物[5]来跟踪表面反应，例如氧还原反应（ORR）。该项目旨在通过制备单晶电极表面和不同的电解质溶液来表征这些能源材料的物理特性。它们之间的相互作用将使用循环伏安法进行研究，并结合SXRD研究，SXRD研究将使用由英国牛津郡钻石光源和英国资助的BM28提供的x射线同步辐射，以及法国格勒诺布尔ESRF的XMaS光束线。在XMaS光束线上安装全新的拉曼光谱探针后，将获得进一步的电化学过程信息，这将补充SXRD研究。参考文献：[1]M. M. Waegele等，化学物理学报，2019,51 (1):160902王志强等，化学工程学报，2002,26 (5):444 - 444张建军，刘建军，刘建军，等。电化学研究进展，2020,19 (1):1 - 6陈晓明，张志强，张志强，表面科学进展，2003,17 (1):1 - 6R. Rizo等，自然通讯，13,2550 （2022）

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 physicsand 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