A Study On The Micro-modelling Of Catalyst Layer In PEM Fuel Cell

Catalyst layer is one of the most important subassembly in Proton exchangemembrane fuel cell (PEMFC). Its stracture and materials transport is closely relatedwith electrode reaction. Therefore, it s very important to understand the relationshipof catalyst layer s structure and functions for improving PEMFC performance. Fornow, it still has significant limitations to research the micro-scale catalyst layer sstructure-function relationship by experimental methods, but the mathematicalsimulation provides an important means for this purpose. Besides, because PEMFCusually works at the atmospheric pressure and80℃, gaseous and liquid water willcoexist inside the cathode catalyst layer, that will affect the concentration andtransport of oxygen,and then affect the whole cell performance. However, previousrelevant simulation much neglected the influence of water. In this study, we simulatethe performance of PEMFC with microstructure lattice models of the catalyst layer,inclding the effect of liquid and gaseous water, and investigate the impact of variousparameters on water transport in the microstructure of catalyst layer and cellperformance.We meliorate the present C-IP two-phase (the Pt/C catalyst phase as C phase, themixed phase of ionomer and pore as IP phase) lattice model by adjusting the oxygeneffective diffusivity which comes from Bruggeman correlation and boundaryconditions to make the model more close to the assumption that the ionomer is mixedwith pore as one phase. Comparisons of simulations where the model is and is notadjusted are carried out, demonstrating the impact of the difference between the twomodels on cell performance should not be neglected. Based on the adjusted C-IPmodel, we discuss the effect of the distribution of ionomer across the catalyst layer,inlet gas pressure, and ionomer conductivity on cell performance.The performance of PEMFC is simulated for the first time with C-IPmicrostructure lattice models of the catalyst layer, including the effect of liquid andgaseous water. Comparisons of simulations where liquid water is and is not factoredin are carried out, demonstrating the necessity of including liquid and gaseous watereffects in the catalyst microstructure. The distribution of the degree of liquid watersaturation, oxygen concentration, and rate of oxygen reduction with catalyst layerthickness are calculated, and factors affecting these distributions are investigated.Then, Based on the model, we discuss the effect of water flooding in the catalyst layer, ionomer volume fraction in IP phase, catalyst layer contact angle andpermeability on cell performance.Since C-IP lattice model is usually suitable for the research of low porositycatalyst layer, for the high porosity catalyst layer we employ Pore-Solid lattice modelto simulate the performance of PEMFC, including the effect of liquid and gaseouswater. And comparisons of the polarization curve by simulated and experimental dataare carried out. Then, Based on Pore-Solid lattice model, we also discuss the effect ofwater flooding in the catalyst layer, porosity, catalyst layer contact angle andpermeability on cell performance.