Preparation And Investigation Of High Performance And High Power Density Of Membrane Electrode Assembly For Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cell?PEMFC?has attracted more and more attention and recognition because of its advantages of high energy conversion efficiency,zero pollution and fast starting at low temperature.It has a wide application prospect in power vehicles and small portable power generation equipment.So far,more and more researchers have focused on PEMFC,and have made more and more achievements in this field.Membrane electrode assembly?MEA?is the core part of PEMFC,and the performance of MEA directly determines the performance of PEMFC.MEA includes five parts:proton exchange membrane?PEM?,cathode catalytic layer?CaCL?,anode catalyst layer?AnCL?,cathode gas diffusion layer?CaGDL?and anode gas diffusion layer?AnCL?.These parts of MEA have a great impact on the performance of MEA,and each component is indispensable.The catalyst layer in MEA is the place where the chemical reaction happens,and the chemical energy can be transformed into electric energy.Therefore,the catalyst layer is very important for MEA.Hydrogen is oxidized to protons and electrons in the anode catalyst layer,which is easier to occur,and there are not too many by-products in the anode to affect the reaction rate and catalyst activity of the anode catalyst layer.The reduction reaction of oxygen occurs in the cathode catalyst layer,oxygen molecules react with the protons and electrons transferred from anode catalyst layer to form water under the action of catalyst.The reduction of cathode is more complicated than the reaction of anode,and there is also the generation of by-product water.Therefore,the preparation and design of the cathode catalyst layer are more difficult and more challenging than the anode catalyst layer.Firstly,the problem of the water management in cathode catalyst layer is a big trouble and the water flooding is easy to occur.Water flooding will lead to the reduction of the activity of the catalyst and the blockage of the gas diffusion channel.Another problem is that the reduction of oxygen in the cathode catalyst layer is rather difficult,and the utilization of the catalyst is relatively low.Aiming at these problems,the research in this paper is also focused on the design and construction of MEA cathode catalyst layer.In this paper,the membrane electrode assembly of proton exchange membrane fuel cell with high performance and high power density is prepared by the research and exploration of the cathode catalyst layer,which effectively improves the performance of MEA and is a great significance for the commercialization of PEMFC.In this paper,a high performance and high power density of membrane electrode assembly is systematically studied from the view of MEA cathode catalyst layer.The main contents of the research are as follows:In order to improve the performance and power density of the MEA,improve the durability of the MEA and enhance the performance of the MEA under the low backpressure of the reaction gas,the hydrophobic fluorocarbon compound is used as the hydrophobic agent and added to the MEA cathode catalyst layer to prepare the MEA with high performance and high power density and the hydrophobic cathode catalyst layer.A high performance and high power density MEA with three dimensional structure and hydrophobic cathode catalyst layer was prepared by using carbon nanomaterials as the three-dimensional structure agent and the fluorocarbon compound as the hydrophobic material,and added to the cathode catalyst layer at the same time.Firstly,the MEA with different Nafion content in the catalyst layer was prepared by using Nafion as ionomer for the catalyst layer.The influence of the content of Nafion in MEA catalyst layer on MEA performance was preliminarily explored,and the content of Nafion was optimized.The results show that when the content of Nafion in the catalyst layer is 35 wt.%,the MEA can get the best performance.Secondly,a hydrophobic fluorocarbon compound?FC?was used as a hydrophobic agent to prepare a MEA with a hydrophobic ability in the cathode catalyst layer.The effects of the amount of FC and the flow of air on the performance of MEA were investigated,and the durability of the MEA with the hydrophobicity of the cathode catalyst layer was investigated.The results showed that the performance and durability of MEA were improved after adding the hydrophobic FC to the cathode catalyst layer.The addition of FC can effectively improve the water management ability of the cathode.When the addition amount of FC is 50 wt.%,it can not only improve the water management ability,but also improve the performance of the MEA.When the single cell operating condition is 70?,30 psi and RH100%,the current density of MEA at 0.7 V and 0.6 V is 950 mA cm^-2 and 1450 mA cm^-2,respectively.And the maximum power density reaches 865 mW cm^-2.After a long time stability test of 60h,the performance of MEA decreased by 10%,and the performance of the blank MEA attenuated by 23%,which was greatly improved compared with the blank MEA.Finally,on the basis of the hydrophobic fluorocarbon compound as the cathode catalyst layer hydrophobic agent,the carbon nanomaterial?CNM?was added as the three-dimensional structure agent of the cathode catalyst layer,and the MEA with three dimensional structure and hydrophobic cathode catalyst layer was prepared.The effects of CNM addition,FC addition and different gas backpressure on MEA performance were explored.The results showed that after the cathode catalyst layer was added with CNM and FC,the performance of the MEA and the performance of MEA under low back pressure were all improved.After optimization,it is found that when the amount of CNM is 20wt.%and the amount of FC is 50wt.%,MEA can get the best battery performance.When the single cell operating condition is 70?,30 psi and RH100%,the current density of MEA at 0.7 V and 0.6 V is 1 A cm^-2 and 1.5 A cm^-2,respectively.And the maximum power density reaches 905 mW cm^-2.When the backpressure of the reaction gas is reduced to 20 psi,the performance of MEA is almost not attenuated.When the backpressure of the gas continues to decrease to 15 psi,the current density of MEA at 0.7 V and 0.6 V is 750 mA cm^-2 and 1300 mA cm^-2,respectively,and the maximum power density can also be kept in 855 mW cm^-2.