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This study investigated the influence of micro-porous layer (MPL) surface topology on the polymer electrolyte fuel cell (PEFC) performance through both experimental characterization and computational modeling. Studies were performed considering MPLs with varying degrees of surface roughness and crack size/density. In two instances, we systematically varied the topology by introducing water transport channels into the MPL. We experimentally observed that transport channels consistently increased the maximum current density. To investigate the reasons for the performance improvement, a two-dimensional, multi-phase, multi-fluid model was formulated with discrete domains for morphological features, including liquid water retention within interfacial voids and cracks. The model results provide evidence that the performance improvement with the modified MPLs is due to improved liquid water removal from the catalyst layer (CL). Liquid water moves laterally through the CL|MPL interface until it reaches the milled lines and from there it is removed in through-plane direction through the fibrous diffusion media (DM) and into the gas channel. A key outcome of this work is that we demonstrate a CL|MPL interface model that can accurately capture the effects of varying MPL surface morphology on PEFC performance and can be used in the design of new, optimized CL|MPL interface morphologies.

The side reactions during long-term operation of vanadium redox flow batteries (VRFBs) increase the average oxidation state of the electrolyte and associated equilibrium potential of the positive half-cell. This consequently initiates the corrosion reactions at the positive side as the half-cell potential passes the critical limit. In this study, an ex-situ accelerated electrochemical corrosion protocol is performed on the carbon paper electrode to investigate the effects of corrosion conditions induced by extended cycling on electrode morphology and VRFB system performance. In terms of morphological changes of corroded electrodes, only minor mechanical degradation is observed, including disappearance of binder material and reduced mechanical properties. With regards to the cell performance, the flow cell with the corroded electrode demonstrates notably higher charge and discharge capacities which can be attributed to the enhanced active surface area of the electrode. Furthermore, the corroded case exhibits an improved capacity retention during extended cycling which can be related to the improved redox activity caused by the increased carboxyl groups and wettability. This study shows that even at these fairly aggressive corrosion conditions, the process behaves as a treatment method, which oxidizes surface functional groups, increases active surface area, and hydrophilicity, and subsequently enhances VRFB performance.

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We present a two-phase, two-dimensional computational model for studying the effect the microporous layer (MPL) and catalyst layer (CL) interface has on the performance of a polymer electrolyte fuel cell (PEFC). The CL|MPL interface is incorporated as a finite-thickness domain where liquid water saturation levels are determined with van Genuchten water retention curves. These relations are extracted through deterministic contact mechanics model that simulates the three-dimensional interfacial deformation under different levels of compression. Model simulations show high levels of liquid water saturation at the interface that have significant effect on the PEFC performance as opposed to when interfacial contact resistance is included there is a minor performance decrease.