Research And Improvement On Water And Gas Transmission In Gas Diffusion Layers

Proton exchange membrane fuel cell is a kind of clean and environmentally friendly electrochemical power generation device, it can be applied to auto-mo biles, portable power supply. Understanding the mass transport problem is very important to improve the performance of fuel cell.This paper analysis”gas transfer” and “water transfer” that high temperature high pressure test for the water-cooling stack and air-cooling stack for back-up power.In the high temperature and high pressure testing,we focus on the oxygen concentration.In the high temperature test,due to the increase of water pressure,oxygen concentration declined sharply,we can increase the concentration of oxygen by adding pressure,so this paper studied the influence of back pressure on the increase with the oxygen concentration at different temperature and humidity,and then through thermodynamics equation to theoretically determine the relationship with the voltage to increase the pressure;then studies the changes along the GDL direction of oxygen pressure,summarizes some methods of judging the GDL.The air-cooling stack used for back-up power,the test condition for the cathode is large flow.Before the mass transfer analysis,we need to judge the MEA is shortage or not in this condition.This paper verifies the mass transfer characteristics the MEA is not short of gas but short of water.we study the moisture transmission mechanism in porous media,the hydrophilic MPL is effective for holding the water and water vapor.Therefore the cathode side MPL using hydrophilic and hydrophobic structure of two layers or three layer structure is improving in this condition.This paper verified the feasibility of nafion as a hydrophilic binder.Nafion can completely replaced the binder for MPL.And for the novel hydrophilic and hydrophobic hybrid structure MPL,when the hydrophobic slurry:hydrophilic slurry=2:1,and the concentration of hydrophilic slurry is 10%,the properties is excellent,is the optimal structure of MPL for back-up power.When the new type of hydrophilic and hydrophobic structure of MPL coated with more than three layers,the thickness can only cause a small increase,so the hydrophilic and hydrophobic structure plays the most important role,the thickness plays the secondary role.