Fuel cells terms Links

A poorly balanced water distribution in the fuel cell can severely impair its performance and cause long-term effects due to structural degradation. If PEMs or CLs are too dry, proton conductivity will be poor, potentially leading to excessive joule heating, which could affect the structural integrity of the cell. Too much water in diffusion media (CLs and GDLs) blocks the gaseous supply of reactants. As these examples show, all processes in PEECs are linked to water distribution and the balance of water fluxes. 

So far, we have focused on the formal description of current generation in the catalyst layer and discussed major effects of structure and composition on exchange current density and catalyst utilization. In the remainder of this chapter, we will explore in detail, how electrocatalytic activity interferes with other processes at the catalyst surface (e.g. surface diffusion) and transport in the bulk phases. The key measure of catalyst layer performance is the current density that could be extracted from a cell for a given cell potential. This links the spatially varying concentrations and reaction rates with the global performance, rated in terms of power density and fuel cell efficiency. 

Fuel cells are inexorably linked with hydrogen, often generically referred to as hydrogen fuel cells . Certainly for low-temperature fuel cells, hydrogen is the fuel of choice in terms of performance and longevity. 

Owing to their cross-linked network, thermosetting resigns are principally known to be less susceptible to corrosion than some thermoplastic materials. Nonetheless, as shown by Bornbaum (2010), a prediction of long-term stability of polymers in fuel cell operation is hardly possible. Thus, the immersion or accelerated lifetime test should be applied on every novel material which has not been operated successfully in a fuel cell over a several thousand hours. These tests may save considerable amounts of time and can be performed before a fuel cell is set up. Nevertheless and finally, only a long-term test in fuel cells at various parameters and different conditions can provide ultimate certainty as to whether a newly developed composite is suitable or not. 

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