Pore-scale investigation of catalyst layer ingredient and structure effect in proton exchange membrane fuel cell

A pore-scale model based on the lattice Boltzmann method (LBM) is developed to simulate the reactive transport processes in the cathode catalyst layer of a proton exchange membrane fuel cell (PEMFC). The porous structures of the cathode catalyst layers are reconstructed in the process-based method with the consideration of carbon supporter, platinum, ionomer and pores. Its characteristics are analyzed including pore size distribution, phase connectivity and active catalyst area. The effects of two critical parameters, platinum/catalyst (Pt/C) and ionomer/catalyst (I/C) ratios, and structure design are investigated in terms of oxygen concentration distribution, reactive area, and reaction rate. The results indicate that, under the constant platinum loading (0.3 mg cm−2), a higher Pt/C ratio yields a thinner catalyst layer, which significantly enhances the oxygen transport and improves the performance. For the same Pt/C ratio, although a higher I/C ratio brings more mass transport loss, it increases the active catalyst area and ultimately yields better performance. Therefore, the active catalyst area should be given precedence during catalyst layer fabrication. To realize a large active catalyst area on the premise of low transport loss, an ideal catalyst layer structure design is proposed and capable of improving the performance by 50%.