Nanoscale modelling of compressive stress on oxygen transfer characteristics in catalyst layer of proton exchange membrane fuel cells

In proton exchange membrane fuel cells (PEMFCs), the compressive stresses lead to changes in the CL morphology, which in turn influence the oxygen transfer characteristics and electrochemical reaction processes within CL. In this work, the nanoscale LB model of the catalyst layer is developed and the effects of Pt-C mass ratio, ionomer content and Pt loading coupled compression ratio on the oxygen transport within the CL pores and ionomer as well as on the electrochemical reaction process are analyzed. The results show that oxygen transfer and electrochemical reaction are dependent on the pore size distribution and active reaction area, and that decreasing the Pt-C mass ratio, increasing the ionomer content and Pt loading increases the active reaction area, but also results in decreasing the pore size and making oxygen transfer more difficult. Compression results in a shorter oxygen transport path and the Pt particles are distributed in a thinner CL, resulting in an increase in the number of active reaction sites and increasing the mean oxygen concentration within the ionomer. There are optimal values of ionomer content and Pt loading that result in the fastest oxygen consumption rate, and CL performance is not simply directly related to Pt loading.