A one-dimensional model for Pt degradation and precipitation in proton exchange membrane fuel cell considering Pt nucleation, particle size growth, and band formation

Abstract

Reducing Pt catalysts amount without sacrificing the performance and durability is critical for the commercialization of proton exchange membrane fuel cells (PEMFCs). Pt degradation in the cathode catalyst layer (CCL) decreases the electrochemically active surface area (ECSA), and Pt precipitation, especially Pt band formation, has a significant effect on proton exchange membrane (PEM) stability, resulting in severe PEMFC degradation during long-term operation. In this study, a one-dimensional model is developed focusing on Pt catalyst degradation and precipitation, including Ostwald-ripening, mass loss, precipitation in the PEM from nucleation, particle size growth, to Pt band formation. The model accuracy is comprehensively validated against the corresponding experimental data, including ECSA loss and particle size distribution (PSD) evolution in the CCL under different operating conditions (temperature, relative humidity, and loading mode), as well as the precipitated Pt size distribution characteristics and local potential in the PEM. Using this model, the Pt band formation process is comprehensively analyzed, and the effects of operating conditions on Pt degradation and Pt band formation are investigated in detail. It is found that the nucleation stage is brief, and then the significant inhomogeneity at the size growth stage causes Pt band formation. In addition, the high activation enthalpy of dissolution under low humidity can effectively inhibit Pt degradation, and Ostwald-ripening is the mean cause of Pt degradation, which is likely to occur during the rapid voltage change period.