Study On The Structure Control And Performance Of Platinum Nanowires Catalyst Layer For Proton Exchange Membrane Fuel Cell

The increasing demand of fossil energy from human society has brought about severe energy crisis and environmental problems.The proton exchange membrane fuel cell（PEMFC）can directly converts the chemical energy in fuel into electrical energy,which has a wide range of application.Therefore,it is considered to be an ideal source of power for new energy vehicles in the future.However,during its commercialization,the cost and performance of the catalyst are still two major problems.In order to promote fuel cell technology,the development of long-life,high-performance fuel cell catalysts and the preparation of low platinum（low-Pt）electrode structures are of great significance.In this paper,the platinum nanowires（Pt-NWs）were in-situ grown on the substrate by wet chemical method.The work focused on the influence of catalyst support,gradient structure and Pt nanoparticles seeds on the growth of Pt-NWs,trying to construct an ordered electrode structure.After optimizing the distribution of Pt-NWs in the catalyst layer,the utilization of Pt was improved and better performance was showed in the single cell test.This work has both theoretical research significance and practical application value.The main research work carried out:（1）The effect of carbon materials on the performance of the catalyst was studied.Three carbon materials,Ketjen Black（KJ carbon）,Graphene Oxide（r GO）,and Multi-walled Carbon Nanotubes（MWCNTs）,were mainly investigated.KJ carbon with high specific surface area showed the best performance at 20%Nafion content.When using r GO as a substrate to grow Pt-NWs,adding appropriate carbon black particles can enhance the adhesion of the catalyst on the surface of the support.MWCNTs was used as a porosity enhancer and mixed with commercial Pt/C catalyst to prepare MEA by the GDE（Gas Diffusion Electrode）method.When the MWCNTs content is 30%,the cell shows excellent performance in both the ohmic polarization zone and the concentration polarization zone.（2）The effect of the double-layer structure on the performance of catalyst layer was studied.The double Pt-nanoparticles（Pt-NPs）catalyst layer was prepared by a step-by-step spraying method.When the Pt loading ratio of poor/rich layer is 1:2,the single cell test shows the best performance.The maximum power density reaches 0.69W·cm^-2.Compared with the single-catalyst layer,the peak power is increased by 21%.Furthermore,the Pt-NWs catalytic layer was applied to the double catalyst layer.It was found that the Pt-NWs grown on the Pt-NPs substrate layer is more in line with the ideal catalyst distribution requirements.The gradient Pt distribution in the catalyst layer improved its utilization.（3）The influence of Pt seed loading and seed content on the growth and distribution of Pt-NWs in a restricted geometric space was studied.The distribution of Pt-NWs was controlled by seed induction.Pt seeds provide more nucleation sites for the growth of Pt-NWs,and a reasonable ratio of the Pt seed and Pt-NWs loading can improve the agglomeration of Pt-NWs and increase the utilization rate of Pt.When using 40 wt.%Pt/C with a Pt loading of 0.005 mg·cm^-2 as the seed,the best single cell performance is obtained.The current density at 0.6V is 35%higher than that of the conventional Pt-NWs catalyst layer.