Anode flooding is frequently encountered in proton exchange membrane fuel cells, which can induce local hydrogen starvation and subsequently result in carbon corrosion in catalyst layers. In this work, we develop a two-dimensional computational model and focus our attention on the mechanisms of hydrogen transport within the diffusion medium when part of the anode channel is clogged. In-plane convection is demonstrated to be the primary mechanism for hydrogen transport at the fringe of the flooded area. As the reactant flows deep inside, however, the dominating mechanism switches to diffusion due to nitrogen accumulation in the anode. Moreover, if hydrogen outside the flooded region is diluted with nitrogen, the length scale for hydrogen to deplete completely is reduced substantially, leading to an extension of the area suffering from hydrogen starvation and carbon corrosion. Meanwhile, the spatial distribution of carbon corrosion rate is emphasized in this work, and the effect of in-plane proton conduction is highlighted. This paper also sheds light on the maximum rate of carbon corrosion, which is demonstrated to be solely determined by oxygen crossover rate at high cell voltages, but is influenced by the kinetics of oxygen reduction reaction at low voltages.
|Number of pages
|International Journal of Heat and Mass Transfer
|Published - Aug 2012
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Mechanical Engineering
- Fluid Flow and Transfer Processes