Various interesting processes take place at electrode/electrolyte interfaces.[1-4] Understanding of those electrochemical processes is very important to design highly efficient and durable materials for energy conversion devices such as fuel cells, photocatalysts and rechargeable batteries. Although surface analysis techniques using electrons as a probe, such as electron microscopy, diffraction and spectroscopy, are powerful tools to investigate the morphology, atomic arrangement, elemental composition and oxidation state of sample surfaces, those techniques cannot be used for in situ investigations of solid/liquid interfaces because of the requirement of vacuum.<br/> <br/>In the 2000s, in situ XPS measurements have been carried out by using room temperature ionic liquids (RTILs) as an electrolyte solution.[8,9] In this technique, an electrochemical cell consisted of working and reference/counter electrodes in contact with a droplet of RTILs can be directly introduced into a vacuum chamber because of near zero pressure of RTILs, to measure the surfaces of the RTIL droplet and electrode under the electrochemical potential control.<br/> <br/>More recently, in situ XPS measurements have been successfully performed in ordinary solvents by utilizing near ambient pressure (NAP-) XPS systems[10,11] or environmental cells[12,13] with a thin membrane.[9] NAP-XPS allows us to measure an electrode surface partially withdrawn from an electrochemical cell in a relatively low vacuum, in the presence of a thin liquid layer on the surface. On the other hand, by using the environmental cell, in which a ultrathin membrane is used as a window for x-rays and photoelectrons, a separator between vacuum and liquid, and a working electrode for electrochemical reactions, in situ XPS measurements of the electrode surface in the presence of a thick liquid layer can be performed by detecting photoelectrons emitted from the solid/liquid (membrane/liquid) interface through the membrane.

In-situ x-ray photoelectron spectroscopy for electrode/electrolyte interfaces

256th National Meeting (2018)

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