A common theme of our research is the use of transient voltage-current response (impedance and nonlinear impedance)
to probe factors limiting electrode performance or causing electrode degradation. We often couple these measurements
with operando techniques to probe more directly (or locally) what is happening in or around the electrode materials
during a reaction. By measuring and modeling these responses as a function of frequency, we gain deeper insights about
the physics and chemistry of the reaction, and which factors limit performance. More recently we have been extending
these methods to entire systems (such as stack of fuel cells in a commercial fuel cell system), and the use of data
science and machine learning to interpret measured responses in terms of physics, chemistry, and operational parameters.