Analysis of Reactant Gas Transport in a Catalyst Layer

An analytical in-situ technique was investigated for evaluating reactant gas transport in a catalyst layer of a fuel cell using limiting current measurements. It was hypothesized that the reactant gas diffusivity in the catalyst layer might be found from the other transport resistance, including Knudsen diffusion resistance and transport resistance through the ionomer and liquid water, when a GDL without an MPL was used. The other transport resistance was estimated by subtracting the molecular diffusion resistance from the total gas transport resistance obtained by measuring the limiting current. The correlation between the catalyst layer specifications, specifically the ionomer carbon weight ratio, and the gas diffusivity in the catalyst layer was investigated using this technique. The results showed that the other transport resistance increased with a larger I/C ratio. It was considered that the difference in porosity due to the variation of the I/C ratio affected the Knudsen diffusion coefficient.