Optimal porosity design for gas diffusion layers of hydrogen fuel cells

In this paper, we introduce porosity-optimization approach to improve electrochemical reactions taking place in the cathode catalyst layer of hydrogen fuel cells. For this, we first model the physics of the reacting oxygen-hydrogen gases in cathode. The model is a two-dimensional, nonlinear, coupled system of Darcy, continuity, and convection-diffusion equations, incorporated with suitable boundary conditions modeling electrochemical reactions in the cathode catalyst. The system is then incorporated with a porosity-optimization problem aiming to find an optimal porosity function of the cathode gas diffusion layer, such that the oxygen-hydrogen reaction rates become even over the cathode catalyst. Our numerical results show that gas diffusion layers designed with the optimized porosity can uniformly distribute the oxygen molecules over the catalyst. This contributes in increasing the lifetime of the cell as it prevents accumulation of heat and water, and leads to a higher electricity production due to better utilization of the cathode catalyst.