Study On Preparation And Performance Of Membrane Electrode For Fuel Cell

Proton exchange membrane fuel cell (PEMFC) is a kind of efficient and clean energy conversion device, It can be direct conversion of chemical energy that stored in the fuel into electrical energy, consequently, which is widely used in small power station, family thermoelectric combined supply apparatus, vehicle power supply, portable back-up power supply and other fields. Membrane electrode assemble(MEA) is the core component of the proton exchange membrane fuel cell, the main place of the electrochemical reaction and the main factor which hinders the commercialization of the fuel cell. Therefore, the design and manufacture of fuel cell not only to follow the basic principle and character of the electrochemical reaction of the fuel cell, but also to overall consider for the finally using conditions, the economic benefits and preparation method. Different preparation methods determine the performance, useful life, auxiliary facilities, and production costs of fuel cell and so on. The research on the preparation of MEA has important significance for accelerating the commercialization of fuel cells.This article firstly established a MEA preparation method that is electrospray deposition method, evaluating the preparation method of three non-contact type of MEA, including ultrasonic spraying, pneumatic spraying method, electrostatic spraying method. Characterized the membrane electrode assemble which prepared by different methods, including SEM、EIS、ECSA、LSV、IV to illustrate the characteristics of the preparation method of the membrane electrode assemble. The results showed that electrostatic spraying method and ultrasonic spray is flatter than pneumatic spray method in the catalytic layer. The Nafion distribution and the catalyst layer thickness are more uniform, showing the excellent performance, Especially the electrostatic spraying with its unique high voltage corona discharge bring the catalyst aggregates negatively charged that give rise to"charges repel each other", It can effectively prevent the agglomeration of the binder Nafion polymer which is add to build a three phase reaction interface of the catalytic layer to increase the proton conducting ability. This kind of aggregation phenomenon has been found in the pneumatic spraying method, Agglomeration of Nafion polymers not only to play a role in the transferring of protons but also to reduce the effective reaction area of the catalytic layer which can reduce the performance of the membrane electrode assemble.At the same time, the hydrophilic characteristics of Nafion polymer, It will cause local flooding phenomenon around the point group, This is particularly evident in the mass transfer polarization region on the IV performance curve. In addition, through the measurement of the resistivity of the membrane electrode interface, The interface resistivity of the membrane electrode catalyst layer by different preparation methods was different, The surface resistivity of the membrane electrode assemble catalyst layer that prepared by electrospray deposition and ultrasonic spraying method is close. The surface resistivity of the membrane electrode assemble catalyst layer that prepared by pneumatic spraying is larger. The larger surface resistivity of the catalyst layer is not beneficial to electron conduction.Through the research on the preparation methods of the membrane electrode assemble, The dispersion degree of the binder Nafion and the catalyst in the catalyst layer has a great influence on the overall performance of the membrane electrode assemble. Dispersion degree indicates the electrochemical active area that exposed compare with total active area in the catalyst layer, the main effect of the catalyst size dispersion is the solid content of the slurry. Therefore, it is necessary to investigate the effect of solid content of the slurry(0.5%,1%,2%) on the performance of the membrane electrode. The results showed that the microstructure of the catalytic layer affects the overall performance of the membrane electrode assemble. Addition of Nafion polymers could help to increase the proton conduction, The effect of the dispersion degree of polymers Nafion on the performance of the membrane electrode is that the more uniform Nafion disperse, the lower hydrogen crossover current density is.The lower intrinsic-resistance is, the lower mass-transfer-resistance is, The better mass-polarization-region performs. But the Nafion polymers brought the active site of the catalyst layer be covered. The electrochemical active area of the catalyst layer was affected, In the polarization curve of electrochemical polarization region (<200mA/cm2) and the holmic polarization region(200-1500mA/cm2) performs poor, Not only The occurrence of catalytic reaction should be taken into consideration but also the prompt transfer of reactants and products should be taken into account in the catalyst layer of the membrane electrode assemble.Controlled the proportion of Nafion polymer and the catalyst and Fully dispersed, the electrochemical active area of the catalyst layer accounts for a half of the total active area, which is maintained in the 40-50m2/g. The membrane electrode assemble prepared with solid content of slurry of 1.0% vhas better overall performance. The active site of the catalyst can be fully exposed and the prompt transfer of reactants and products, it is very suitable for spray technology.