The ability of certain crystalline oxides to conduct ions at a significant rate forms the basis for a range of electrochemical devices such as solid oxide fuel cells, solid oxide electrolyser cells, and batteries. These devices are key for the EU Energy 2050 long-term strategy, hence there is an increasing demand for the development of faster and more stable ionic conducting materials.
Ionic transport in oxides requires the long-range motion of crystalline defects and is limited by one or more of the following processes: bulk diffusion, incorporation/excorporation into the material, or transport across grain boundaries or interfaces. Fundamentally, these limits are caused by either the concentration of ionic or electronic defects, migration barriers (according to the bond strengths and steric constraints of the ions), interactions between defects, or the formation of space charge regions that deplete charge carriers. Traditionally, materials development has been based on either searching for new oxides or tuning the chemical composition and microstructure of current materials to maximise ionic transport. But progress has been slow, with newly developed materials failing to meet the strict requirements to replace the state-of-the-art materials at a commercial level.
The OPTICS project aims to investigate and exploit new methods for enhancing ionic transport in electroceramic materials, namely the use of above-bandgap radiation. Several recent reports have suggested that the concentration and effective mobility of ionic defects may be varied by UV light, but currently this effect is poorly understood. Light-enhanced ionic transport has the potential to rapidly progress beyond current state-of-the-art in technologically relevant ionically conducting oxides. While experientially and computationally non-trivial, demonstrating light-enhanced ionic transport would represent significant progress from an academic standpoint, but crucially, would also have the potential to usher in a new class of opto-ionic fuel cells, electrolysers, and batteries.
