Pore-scale modelling of reactive transport processes in catalyst layers with mesoporous carbon supports

For proton exchange membrane fuel cells (PEMFCs), it is generally believed that the catalyst layer (CL) with mesoporous carbon supports has a higher catalyst activity, but the oxygen transport performance remains unclear. In this work, a pore-scale model is developed to simulate the reactive transport processes of oxygen in mesoporous carbon CLs. Besides, theoretical models are proposed to predict the oxygen local transport resistance for the solid and mesoporous carbon catalysts, which are in good agreement with numerical results. It's found that the oxygen adsorption resistance at the water-Pt interface is far less than that at the ionomer-Pt interface, and thus the oxygen transport performance of mesoporous carbon catalysts can be superior to the solid carbon at a high relative humidity (RH). Moreover, the structure-performance relation of mesoporous carbon is built to find that there exists an optimal microstructure to reach the lowest oxygen transport resistance. Too much Pt deposited in the interior pores would lead to the increase of oxygen local transport resistance. The RH-dependence performance of mesoporous carbon catalysts is also revealed in this work.