Contributions of gradient electrode designs to the performance of PEMFCs: Modeling and optimization

Owing to proton and oxygen transport resistances, a gradient distribution of proton potential and oxygen concentration is generally existed in the porous electrode. In this work, the electrodes with both gradients in the catalyst layer (CL) and gas diffusion layer (GDL) are proposed to coordinate with the transport processes, improving the utilization efficiency of Pt catalyst. A multi-field coupling transport model of PEMFCs is developed to determine the contributions of gradient designs to the performance improvement. We find that the contribution of CL gradient is much higher than that of GDL gradient and thus we explore how each gradient component in CLs affect the performance. Interestingly, it is observed that the optimal distribution of the Pt gradient is closely related to I/C: when I/C is low(high), more Pt loading on the MEM(GDL) side is preferred. We then adopt a data-driven model coupled with genetic algorithm to determine the optimal gradient structure, which improve the performance by 22.9 %. Finally, the performance of electrode with multilayered gradient structures are examined by the phase diagrams.