Boosting Performance of PEMFCs via Optimization of Oxygen Transport Resistance in Catalyst Layers Using Mesoporous Carbons

Mesoporous carbons, as the catalyst support in proton exchange membrane fuel cells (PEMFCs), can improve the specific activity of catalysts and the high-power performance of cells, but the underlying physics remains elusive. In this work, a model is proposed to describe the oxygen transport process for both exterior and interior platinum (Pt) catalysts on the mesoporous carbon catalyst layers (CLs) under various relative humidity (RH) conditions, considering the structure evolution of interior pores induced by the condensed water. We find that although the local oxygen transport resistance (R_Pt^O₂) of interior Pt catalysts is less than that of exterior Pt catalysts, too much Pt deposit in the interior pores would still lead to the remarkable increase of R_Pt^O₂. The output performance of mesoporous carbon CLs is better than that of solid carbon CLs at a high RH but is instead worse at a low RH value. A data-driven model is then built to unravel the structure-performance relation of the mesoporous carbon. By reducing R_Pt^O₂ via microstructure optimization, we determine an optimal pore size of mesoporous carbons where the output performance is the best within the studied range of RH values.