Preparation Of Carbon Nanofibers By Electrostatic Spinning And Its Performance As Catalyst Support For The Hydrogen Fuel Cell

This paper focuses on the research of catalyst support materials for hydrogen fuel cell.In this paper,carbon nanofibers（CNFs）and graphitized carbon nanofibers catalyst support were prepared by using electrostatic spinning technology and carbonization heat treatment.Through the design and optimization of experimental conditions to complete the preparation of catalyst and membrane electrode and electrochemical performance test.The specific research contents and results are as follows:（1）Using organic polymer polyacrylonitrile（PAN）as a carbon source,carbon nanofibers were prepared by electrostatic spinning technology,pre-oxidation,and carbonization heat treatment.Finally,a fuel cell catalyst（Pt-CNFs）containing 20 wt%platinum was prepared by liquid-phase reduction of platinum salt using carbon nanofibers（CNFs）as support and ethylene glycol as reducing agent.The catalyst was characterized and its electrochemical activity and single-cell performance were tested.The influence of carbonization temperature and different mass concentration of PAN/N,N-dimethylformamide（DMF）spinning solution on the performance of the catalyst was investigated.The experimental results showed that the optimum preparation conditions were PAN/DMF solution with a mass concentration of 6%and carbonization temperature of 1100℃（Pt-6%PAN-1100）.Its electrochemical surface activity area（ECSA）and mass activity（MA）measured on the electrochemical workstation were 76.62 m²/g _Pt and 0.136 A/mg _Pt,respectively.And its power density measured by a single cell test was 1231.3 m W/cm².Using commercial Vulcan XC-72 as the support（VXC-72）,the Pt-VXC-72 catalyst with a platinum content of 20 wt%was prepared by the same method.The electrochemical surface activity area（ECSA）and mass activity（MA）measured on the electrochemical workstation were 75.65 m²/g _Pt and 0.115 A/mg _Pt,respectively.The power density measured by a single cell test was 1229.4m W/cm².The electrochemical performance and single-cell performance of hydrogen cell catalyst prepared by carbon nanofibers as a support are superior to that of commercial carbon support,indicating that carbon nanofibers prepared by the electrostatic spinning method are feasible as fuel cell catalyst support.（2）In the 6 wt%PAN/DMF solution,manganese acetylacetone（Ⅲ）was added for spinning.In the process of high-temperature carbonization,manganese could catalyze the graphitization of nanofibers to obtain graphitized carbon nanofibers.At the same time,manganese will generate manganese oxide nanoparticles on the surface of nanofibers at high temperatures.The graphitized carbon nanofibers with more surface defects can be obtained by pickling manganese oxide nanoparticles from the fibers,which is beneficial to the loading of platinum nanoparticles on the support.The fuel cell catalyst containing 20 wt%platinum was also prepared by liquid-phase reduction of ethylene glycol.The influence of graphitized carbon nanofiber support prepared by adding different contents of manganese acetyl acetone（Ⅲ）on the performance of catalyst was investigated The corrosion resistance of carbon nanofibers support was tested 5000 cycles on electrochemical workstation and fuel cell test system using accelerated stress test（AST）method.Experimental results show that the support with the best corrosion resistance can be prepared under the following conditions:carbon nanofiber support with the mass ratio of manganese acetylacetone（Ⅲ）to PAN 3:10（Pt-30Mn/6%PAN-1100）.The electrochemical workstation tested its electrochemical activity surface area（ECSA）of 52.76 A/mg _Pt,mass activity（MA）of 0.087 A/mg _Pt,single-cell tested its power density of 665.0 m W/cm².After 5000 cycles of high voltage voltammetry（CV）in the electrochemical station,the ECSA decreased only by6.20%.After 5000 cycles of CV on the fuel cell test system,the voltage dropped by 13 m V at 1.5 A/cm² current density.The ECSA of Pt-6%PAN-1100decreased by 20.97%,and the voltage decreased by more than 220 m V at 1.5A/cm² current density.The ECSA of Pt-VXC-72 decreased by 13.48%,and the voltage decreased by 99 m V at 1.5 A/cm² current density.Compared with VXC-72,the corrosion resistance of carbon nanofibers without graphitization is poor,and the corrosion resistance becomes better after graphitization,but the electrochemical performance of the catalyst prepared by the graphitization decreases,so the balance between the graphitization of the support and the electrochemical performance of the catalyst needs further study.