Effect And Optimization Of Solvents In The Preparation Of Fuel Cell Membrane Electrode Assembly By Blade Coating

Proton exchange membrane fuel cell(PEMFC)is considered to be the most promising hydrogen energy conversion and utilization technology at present.At present,MEA is mainly produced through the following three ways:(1)the catalyst is coated with the gas diffusion layer(GDE);(2)the catalyst is coated with a proton exchange membrane(CCM)and(3)the catalyst is coated with a decal substrate(DTM).In the process of catalyst slurry coating,process conditions such as slurry formulations(composed of catalyst,ionomer and dispersed solvent),substrate materials(PTFE membrane,proton exchange membrane,gas diffusion layer)will affect the formation of microstructure of the catalyst layer,and then directly affect the number and distribution of active three-phase sites in MEA.In view of the shortcomings of the scraping process,such as poor contact between the membrane and catalyst layer and low battery performance,this paper focused on the optimization of the scraping process to prepare the membrane electrode assembly,and compared and explored the influence of solvent effect on the performance of PEMFC on different substrate materials.Based on the above findings,a preparation method of membrane electrode assembly based on scraping GDE of MEA was developed,which has scientific guidance and application significance for large-scale development of high-performance MEA.The details are as follows:(1)The influence of solvent types in catalyst slurry on catalyst layer was explored.Firstly,the MEA preparation process by scraping and coating method was optimized to obtain high performance MEA.Subsequently,the influence of slurry prepared with different dispersive solvents on catalyst layer was studied in the process of MEA preparation by decal method.Through the contact Angle test of the catalyst layer and SEM analysis,it can be found that the boiling point and viscosity of the dispersive solvents affect the coatability of the catalyst slurry and the drying step of the slurry,and then affect the formation of the three-phase site in the membrane electrode assembly and the good contact interface between the membrane and the catalyst layer.(2)The influence of catalyst paste directly scraped on PEM(CCM)and GDL(GDE)and solvent types on the performance of MEA was investigated.Through the single cell test and low oxygen concentration test of MEAs prepared by different dispersive solvents,and the comparison of the physical characteristics of the catalyst layer,it can be found that when the catalyst slurry is scrape on the surface of PEM or GDL,Nafion ionomer exists in the solution form in the dispersive solvent,it has better battery performance.At the same time,physical properties such as the boiling point,viscosity and density of the dispersive solvent will also affect the dispersion state of the catalyst slurry when it acts on the base material.(3)In order to solve the problem of large ionic conduction internal resistance at the interface between the catalyst layer and the PEM prepared by the GDE method,a new membrane electrode process based on the GDE method was developed: the GDE intermediate layer method.The battery performance of MEA prepared by the optimized membrane electrode preparation process was improved by 8.8%.A one-dimensional gas transport model was established and mass transfer resistance was analyzed.It was found that when the intermediate layer of the polymer was covered on the surface of the gas diffusion electrode in the form of solution,the oxygen needed to travel less path to the active site of the catalyst and the overall gas transport resistance was small.