Congratulations to Charles Quesnel on the acceptance of his first peer-reviewed journal article. The work took several years to conduct and ages to interpret the data. The final result is an excellent work in the top-tier Journal of Physical Chemistry C.
Abstract: The percolating flow of liquid water in the gas-diffusion layer (GDL) of polymer-electrolyte fuel cells (PEFCs) was studied ex situ using a simple water-injection experiment. Water was injected into the top of the sample so the droplet was free to detach from the bottom, allowing for uninterrupted study of the dynamic cycle of droplet appearance, growth, and detachment. Although droplets emerged from a single point on the GDL, the measured pressure response in the water phase was clearly not equivalent to a single needle. The behavior of the system was explained by the simultaneous filling and inflating of many menisci, resulting in extended periods with no droplet activity at the GDL surface, followed by the sudden eruption of a droplet at the breakthrough site as all interfaces deflated and their stored water was directed towards the droplet. A simple numerical model was presented that could qualitatively explain the observed behavior. Tests were performed on GDLs, with and without microporous layers (MPLs) and all observed behavior could be interpreted in terms of the proposed model. MPLs shifted the behavior to a more needle-like behavior which was consistent with the MPL reducing the number of invading liquid clusters in the system.