Simulations Of The PEMFC Electrode Microstructure

Electrode is one of the most important subassembly in Proton exchange membrane fuel cell (PEMFC). It is benefit to improve cell performance and reduce cell cost by optimization electrode structure and operation condition. Thus, it is an important method to increase the commercial rate of proton exchange membrane fuel cell. However, it is difficult and costs a lot to research the effect of electrode on cell performance. Therefore, simulation using computer is an important assistant method. In this study, we improve cell performance by optimizing the component, structure and operation condition base on microstructure electrode model.We meliorate the present Pore-Solid two phase lattice model by removing the solid lattice which is suspending in the air and make the model more close to the real electrode. By comparation the simulation result, we prove that removing the suspending solid lattice is indispensable to establish an accurate electrode model. Base on the model, we disscuse the effect of porosity, ionomer conductivity, inlet gas concentration, the distribution of catalyst and ionomer across the electrode etc. on cell performance.To solve the problem that Pore-Solid model is unsuiltable for the research of low porosity electrode, we establise a C-IP two phase random lattice model and made the simulation results better fit with experimental result. The effect of ionomer distribution across catalyst layer was studied by comparing profiles of oxygen level, reaction rate and overpotential, as well as corresponding polarization curves. The peak of reaction rate moves from membrane side to GDL side with the increase of cell current, as a result of rate-limiting factor shifting from proton conduction to oxygen transport. Nonuniform ionomer distribution across catalyst layer, with higher ionomer content at the membrane side and higher porosity at GDL side, is superior to uniform ionomer distribution when working at high cell current.We establish a microstructure non-lattice electrode model, in which the Pt/C particles are assumed to be sphere.We discuss the effect of catalyst loading, mean size of Pt/C, electrode thickness, inlet gas pressure and ionomer conductivity on cell performance. The moderate mean size of Pt/C is benefit to improve cell performance.Finally, we elstablish a microstructure lattice cluster electrode model and discuss the effect of agglomerate parameter and agglomerate type on cell performance. The simulation results show the completely ordered electrode structure across the electrode display the best cell performance.