Preparation And Electrochemical Performance Of Composite Electrode Based On Polyaniline

With the rapid economic and technological growth,environmental pollution is becoming increasingly serious and the energy problem is imminent.Energy storage equipment supercapacitor and energy conversion equipment fuel cell attach great importance by the industry and scientific research community.As an important component of energy storage and conversion equipment,the electrode material plays an irreplaceable role on the overall electrical properties of the equipment.Among a wide range of electrode materials,the conductive polymer polyaniline with the advantages of raw material easy to get,simple synthesis,environment-friendly,high electrical conductivity and good thermal stability has become one of the research hotspots in the field of electrode materials.However,due to processing performance and physical performance of conductive polyaniline is not ideal,to some extent,its application is limited in energy storage equipment.In this paper,a simple chemical method is used to synthesize composite electrode material of conductive polyaniline with a pseudo-capacitance performance and carbon materials(carbon cloth and carboxyl group functionalized carbon nanotubes)with double-layer capacitance performance for supercapacitors.With the combined action of conductive polyaniline and carbon material,it not only make up the deficiency of the mechanical propertied of polyaniline,enhance the stability of the electrode material,but also improve the specific capacitance,energy density and power density of the electrode material.On the basis of this,through the further processing of the composites,we further study the oxygen reduction reaction performance of polyaniline and aniline @ pyrrole copolymer based electrode material.The main research work is summarized as follows:1)The sea cucumber like polyaniline @ carboxyl group functionalized carbon nanotubes composite for supercapacitor is synthesized using carboxyl group functionalized carbon nanotubes with better conductivity and higher specific surface area as the skeleton.And we compare with polyaniline @ non-functionalized carbon nanotubes composite on the structure,specific surface area,thermal stability and electrochemical properties.The results show that the sea cucumber like composite has a large specific surface area,good thermal stability and more excellent electrochemical properties such as good cycle stability,good rate capability and better capacitance performance.In addition,we discuss the effect of carboxyl group in depth,the chemical linkage between –COO-and –NH= plays a positive function to the electrochemical properties of the composite.We could get a conclusion that the surface treatment of the traditional materials is very meaningful to improve the properties of the materials.2)We fabricate polyaniline @ carbon cloth composite electrode material for supercapacitor by in situ polymerization method under different temperature conditions.The results show that polyaniline fibers own different structures in different temperature environment.Compared with polyaniline fibers from room temperature,the polyaniline fibers prepared in the ice-water bath have smaller length and diameter,50 nm and 20 nm respectively.And the polyaniline fibers are uniformly and orderly covered on the surface of the carbon cloth generate a three-dimensional porous structure,which provides a greater surface area for the contact of the active material with the electrolyte ions and also provide a shorter path for the transport of electrolyte ions and electrons.Compared with the pure polyaniline material,the polyaniline @ carbon cloth composites show obvious enhanced electrochemical performance,and the electrochemical properties of the polyaniline @ carbon cloth composite synthesized in the ice bath environment is the best.The specific capacitance is 439 F g-1 at the current density of 1 A g-1,and the energy density is 60.83 Wh kg-1 at the power density of 500 W kg-1,in addition to this,the composite electrode material also exhibits good cycle stability.3)We synthesized structure controlled polyaniline coating using different oxidants by a simple chemical method and the use of different oxidant corresponds to different polyaniline coating structure.FeCl3 as the oxidant,the polyaniline coating is uniformly coated;H2O2 as the oxidant,the polyaniline coating is layer and layer fibrous;MnO2 as the oxidant,the polyaniline coating is ordered needle like.The effect of the structure on the properties of the polyaniline electrode is investigated by the physical characterization and the electrochemical properties.The results show that the ordered needle like polyaniline coating with relatively large porosity exhibits the best electrochemical performance.The specific capacitance is up to 560.5 F g-1 at the discharge current density of 1 A g-1.The study of polyaniline structure is very important for its application in energy storage equipment.4)The oxygen reduction catalyst electrode materials Fe-N/C,Cu-N/C and Co-N/C are synthesized by three-step method(polymerization reaction,complexation reaction and pyrolysis reaction)with polyaniline and iron,cobalt and copper chloride as precursors.And we characterize their electrochemical property.The results show that the oxygen reduction ability of catalyst electrode material is improved obviously after the metal-doped.But the oxygen reduction activity of the different metal elements is different,the iron-doped catalyst electrode material has the best oxygen reduction ability.In addition to this,the time of metal ion complexation reaction and the pyrolysis temperature in nitrogen atmosphere have great influence on the oxygen reduction activity of electrode materials.After electrochemical performance analysis,we obtained the best complex reaction time is 6 h and the best pyrolysis temperature is 900 ?.5)Under the nitrogen atmosphere,the Fe-N/C catalyst electrode material with low cost and excellent electrochemical performance is obtained by pyrolysis of iron-doped aniline@pyrrole copolymer composite at high temperature.Aniline@pyrrole copolymer is modified by in situ polymerization on the surface of carbon cloth as a precursor of carbon source and nitrogen source,and then to achieve the metal ion coordination,the complexation reaction happens.Finally,we obtain the Fe-N/C catalyst electrode material by high temperature carbonation.We analysis the active sites in the catalyst material in depth.The experimental results show that the catalyst electrode material prepared at 850 ? has abundant active sites,and the oxygen reduction initiation potential is 17 mV(vs.Ag / AgCl),close to 28 mV of the catalyst material Pt / C in the alkaline electrolyte system.