| Proton exchange membrane fuel cell(PEMFC)has attracted much attention for its high energy efficiency,but the cost hinders its commercialization progress,while the Pt-based catalyst used on the cathode is the most important composition.Fe-N-C is considered as a possible substitute for Pt-based catalysts.When applied Fe-N-C catalyst to MEA,the performance is not only affected by the catalyst,but also the preparation process.The following work has been carried out in this paper:(1)Fe-N-C catalyst with high activity was prepared with iron(II)acetate,1,10-phenanthroline,and ZIF-8.The optimal feed ratio(1:20:80)and the best pyrolysis time(30 min)were determined.The catalyst shows a large specific surface area(1008.86m2/g),high pyridine nitrogen content(27.2% of nitrogen content)and uniform Fe distribution and a half-wave potential of 0.808 V,a H2O2 yield of less than 5%,while the half-wave potential attenuation is 24 m V after ADT testing.(2)Parameters in preparation process were changed to find out their influences.For slurry dispersion,the 24 h ice bath stirring step is indispensable because the performance of MEA prepared without 24 h ice bath stirring has been greatly reduced.Too low or too high I/C were both harmful to the performance,the best performance appears in 1.0,which is increased to 624 m W/cm2.When spraying,if the drying temperature is too low,it will affect the volatilization of the solvent.The sprayed mist slurry will gather into droplets on the surface and affects the spraying effect.Selecting60℃ as spraying temperature,the performance reached to 686 m W/cm2.Insufficient hot pressing causes poor bonding between the membrane and the catalytic layer,while excessive hot pressing result in the membrane structure and the pore structure of the catalytic layer to be destroyed.The performance is increased to 832.2 m W/cm2 under5 MPa,3 min,and 140°C.The highest performance of MEA prepared by electrostatic spraying is appearing at 5 mg/cm2 of the loading capacity,which is 868.3 m W/cm2,and the highest performance of the ultrasonic spraying is reached when the loading capacity is 3 mg/cm2,which is 1117.5 m W/cm2.The oxygen transmission resistance of different loadings is highly positively correlated with performance.The possible reason is that the uneven distribution of the pores caused by the increase in the unevenness of the catalyst layer due to the low loading,which leads to an increase in the oxygen transmission resistance.Too high loading results in a denser catalytic layer,an increase in oxygen transmission resistance.After the above optimization,the MEA performance has been improved from 593.6 m W/cm2 to 1117.5 m W/cm2,which is nearly doubled.The preparation process has a huge impact on the performance.In this paper,the factors affecting the performance of Fe-N-C catalyst in MEA are studied from the aspect of preparation process,which lays the foundation for the follow-up research on the mass transfer and oxygen transmission problems in MEA.It also provides a new perspective for the design of new models.Fe-N-C catalyst. |
PDF Full Text Request