Effects of flow distributor geometry and diffusion layer porosity on reactant gas transport and performance of proton exchange membrane fuel cells

A study has been conducted on the effects of flow distributor and diffusion layer geometries and morphologies on the transport phenomena of reactant gas from flow channels to gas diffuser, and on the performance of a proton exchange membrane fuel cell. The emphasis of the analysis is placed on the effects of the cross-section of the channel of the anode flow distributor and the porosity of the gas-diffusion layer. By applying a two-dimensional mass transport model, the effects of the channel width fraction, λ=ℓc/ℓb, the channel number, N, the porosity of the diffuser layer, var epsilon, and the surface overpotential of the catalyst layer, η, on the resultant current density are investigated. The cell performance is evaluated by the predicted voltage–current density curves. It is disclosed that an increase in either λ, N or var epsilon may lead to a better cell performance. At relatively low overpotential, better uniformity in current density distribution along the width of the cell (x-direction) can be attained. Based on the present results, a correlation of overpotentials is proposed, namely, ηcr=0.165λ0.0935N0.2033var epsilon0.0856, which may serve as a guideline to justify the validity of a simplified one-dimensional model.