EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

The ability to study the solid/liquid interface in situ is essential to gain fundamental understanding of electrochemical processes. A poor understanding of surface chemical processes at electrodes is a key bottleneck in the development of many energy technologies -e.g. alternative battery technologies or water splitting catalysts. X-Ray Photoelectron Spectroscopy (XPS) is one of the most powerful probes of surface chemistry available but addressing the electrode/electrolyte interface with XPS is a major technical challenge as it is buried by the electrode on one side and the electrolyte on the other - making detection of photoelectrons from this interface very difficult. There has been intense efforts to overcome these challenges by either establishing (electron-transparent) ultrathin wetting layers on sample surfaces (known as the “dip and pull” method) or by making ultrathin graphene electrodes through which the interface can be addressed.
I will present an alternative approach to establishing an ultrathin wetting layer on the sample surface, through which we can directly probe the electrode/electrolyte interface in-situ. We do this by introducing a droplet of electrolyte onto the sample, offset from the analysis area by a few millimetres. This “offset droplet” approach has the advantages of being applicable to virtually any sample, the capability to alter the solution composition dynamically and a short diffusion length from analysis area to the “bulk” droplet.
I will outline the capabilities and the challenges of this technique and present some results applying it to the study of model electrocatalysts and battery materials.