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A three-dimensional, electrochemical-transport coupled model is applied to a 50 cm 2 proton exchange membrane ͑PEM͒ fuel cell and validated against the current distribution data experimentally measured earlier. A parallel computational methodology is employed to substantially reduce the computational time and make large-scale calculations involving millions of grid points possible. Simulation results are analyzed and validated against the available experimental data of current distribution under fully humidified conditions for two cathode stoichiometry ratios. The comparisons of simulations and experiments point out a lack of agreement in the current distribution, although the average polarization curves are matched nearly perfectly. The numerical simulations correctly capture the comma-shaped local polarization curves observed in the current distribution experiments.

Metal-free carbon materials have emerged as cost-effective and high-performance catalysts for the production of hydrogen peroxide (H2O2) through the two-electron oxygen reduction reaction (ORR). Here, we show that 3D crumpled...

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Neutron radiography ͑NR͒ was intended to visualize the accumulation and distribution of product water inside diffusion media ͑DM͒ in a polymer-electrolyte fuel cell ͑PEFC͒. However, the two-dimensional NR technique is unable to separate anode water from cathode water and resolve the liquid water distribution along the cell thickness, two pieces of information strongly needed to characterize the level of cathode DM flooding or anode dry-out. In this paper, NR data analysis is performed for the first time in the context of a three-dimensional two-phase PEFC model. The numerical study illustrates the difficulty in NR data analysis where the major concern originates from the separation of liquid water in the cathode DM from the water in thick membranes, or from liquid water in the anode DM for the thin membrane case. In addition, the two-phase simulation results show that the calculated amount of water according to NR conditions is well within the range measured by NR experiments in the literature, demonstrating the validity of the present two-phase model. A concern is raised whether the two-dimensional NR technique is suitable for studying water management, which generally requires separation of water between the anode and cathode.While increasing oil prices and environmental concerns have become pressing issues worldwide, the polymer-electrolyte fuel cell ͑PEFC͒ has received great attention as a promising future energy converter. Despite enormous progresses in PEFC technology for the last decade, several challenges remain before its potential can be realized. One of these is related to flooding phenomena. Due to the presence of liquid water inside a PEFC where the catalyst layer ͑CL͒, porous diffusion media ͑DM͒, and even gas channel ͑GC͒ can be flooded, thereby impeding transport of reactants and oxygen reduction reaction and finally resulting in significant deterioration in cell performance and durability. To resolve the issue, substantial efforts have been made to study flooding phenomena and related two-phase transport inside PEFCs. A number of two-phase PEFC models published in the literature are based on two-phase transport in porous media driven by capillary action, focusing on electrode and DM flooding. 1-18 An overview was provided by Wang. 19 Some of them further analyzed the effects of multi-layer DMs, composed of two or more layers of porous materials having different pore sizes and/or wetting characteristics. 4,7,12,16 Nonisothermal, two-phase transport effects were also investigated [3][4][5]9,15,17 and transient aspect on liquid water distribution. 2,14,18 Simultaneously, various experimental techniques for investigation of flooding phenomena have been developed. Optical visualization using transparent cells has been widely employed to study complex mechanisms of liquid water transport in channels, such as droplet formation, growth, and detachment from DM surfaces ͑hy-drophobic͒, droplet interaction with channel side walls ͑hydro-philic͒, as well as development of liquid film on channel walls or chan...