Properties of redox-active materials vary exponentially with (electro)chemical potential and are heterogeneous both at the atomic length scale and at the macroscale. The Chueh Group is at the forefront of developing new in-situ X-ray spectroscopy and microscopy approaches to probe electrochemically-active materials while reactions take place.
To “see” the gas/solid interface, such as those in solid-oxide fuel cells, we combined microfabricated solid-state electrochemical cells with ambient-pressure, surface-sensitive X-ray spectroscopies (Feng et al., Nature Commun. 2014; Mueller, et al., Nature Commun. 2015; Gopal et al., Nature Commun. 2017). This characterization platform has enabled us to probe electrochemical reactions at the atomistic and molecular level, providing a previously unavailable window into ion-insertion reactions. To probe the liquid/solid interface, such as those in lithium-ion batteries and aqueous electrolyzers, we combined microfluidic cells and X-ray microscopy to track single-particle electrochemistry in real time (Li et al., Adv. Func. Mater. 2015; Lim et al., Science 2016), providing a nanoscale, in-situ view of ion-insertion reactions.
In collaboration with SLAC National Accelerator Laboratory, we are also pushing the limits of temporal resolution by utilizing X-ray free-electron lasers to monitor a single ion hop on the order of picoseconds, which is the most fundamental process that governs ionic transport in solids.