RU2495509C1 - Method of producing composite material for supercapacitor electrode - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing composite material for a supercapacitor electrode, involving synthesis of electroconductive polymers or substituted derivatives thereof during oxidative polymerisation of corresponding monomers on the surface of carbon materials. The environmentally acceptable method involves conducting polymerisation in the presence of laccase enzyme, acidic dopants, an oxidant and an enzymatic reaction redox mediator, dissolved in the reaction mixture.

EFFECT: improved method.

10 cl, 4 ex

Description

The invention relates to the field of electrical engineering and can be used to create devices that accumulate electrical energy (supercapacitors). One of the important parameters determining the specific power and specific energy of energy-storage rechargeable current sources is the specific capacity of materials used for the manufacture of electrodes of supercapacitors.

In supercapacitors based on the capacity of a double electric layer, the total capacity increases with increasing specific surface area of the electrode material due to a decrease in pore size, which leads to the problem of ion transport and filling of pores with electrolyte. The so-called pseudo-supercapacitors are based on the Faraday reaction at the electrode / electrolyte interface. The materials for the first type of supercapacitors are various carbon materials, primarily coal, and the materials for the second type are noble metal oxides or electrically conductive polymers.

The metal oxides used in pseudosupercapacitors have a high specific capacity, however, they have a sufficiently large specific gravity, and often high cost and toxicity.

The development of composite materials based on carbon materials and electrically conductive polymers synthesized directly on their surface, such as polyaniline, polypyrrole or polyethylene dioxithiophene, allows to increase the specific capacity of the hybrid material due to the combination of capacitive and Faraday components.

The prospect of such studies is confirmed by publications both in periodical scientific journals and in the patent literature: 1. M. Jin, G. Han, Y. Chang, H. Zhao, H. Zhang "Flexible electrodes based on polypyrrole / manganese dioxide / polypropylene" // Electrochimica Acta, 2011, V. 56, P. 9838-9845.

2. J.R. Miller and P. Simon "Materials science: Electrochemical capacitors for energy management // Science, 2008, V. 321, P. 651-652.

3. D. Pech, M. Brunet, H. Durou, P. Huang, V. Mochalin, Y. Gogotsi, P.-L. Taberna, P. Simon, “Ultrahigh-power micrometer-sized supercapacitors based on onion-like carbon” // Nature Nanotechnology, 2010, V. 5, P. 651-654.

4. L. Chen, Ch. Yuan, H. Don, B. Gao, Sh. Chen, X. Zhang "Synthesis and electrochemical capacitance of core-shell poly (3,4-ethylenedioxythiophene) / poly (sodium-4-styrenesulfonate) -modified multiwalled carbon nanotube nanocomposites" // Electrochimica Acta, 2009, V. 54, P 2335-2341.

5. J. Jang, J. Bae, M. Choi, S.-H. Yoon "Fabrication and characterization of polyaniline coated carbon nanofiber for supercapacitor" // Carbon, 2005, V. 43 (13), P. 2730-2736.

6. L. Li, E. Liu, J. Li, Y. Yang, H. Shen, Z. Huang, X. Xiang, W. Li “A doped activated carbon prepared from polyaniline for high performance supercapacitors” // Journal of Power Sources, 2010, V. 195, P. 1516-1521.

7. G.A. Snook, P. Kao, A.S. Best “Conducting-polymer-based supercapacitor devices and elecrodes” // Journal of Power Sources, 2011, V. 196, P. 1-12.

8. Q. Liu, M.H. Nay fen, S.T. Yau, “Brushed-on flexible supercapacitor sheets using nanocomposite of polyaniline and carbon nanotubes” // Journal of Power Sources, 2010, V. 195, P. 7480-7483.

9. US Patent 7508650 "Electrode for electrochemical capacitor", 2009.

10. US Patent 6795293 "Polymer-modified electrode for energy storage devices and electrochemical supercapacitor based on said polymer-modified electrode", 2003.

11. US Patent Application 20100008021 "Porous carbon electrode with conductive polymer coating", 2007.

Typically, composite materials based on electrically conductive polymers are synthesized by chemical or electrochemical methods, by deposition of polymers on solid electrically conductive matrices (in situ method) (US patent application 20100008021; US patent 6,383,640; US patent 7,508,650; US patent 7,673,114; US patent 5,284,723; patent U.S. 6,482,299; China Patent CN 201804714U). The electrochemical polymerization of monomers on an electrically conductive surface proceeds without the addition of chemical oxidizing agents, but is limited by the presence of an electrically conductive substrate and its limited size. Chemical oxidation of monomers is a fairly simple method for producing composite materials based on electrically conductive polymers and carbon materials using strong oxidizing agents, such as ammonium persulfate, salts of ferric ions, dichromates, permanganates in concentrations comparable or many times higher than the concentrations of monomers used. The reduction products of these compounds must be processed, which creates additional costs in the synthesis of electrically conductive polymers on the surface of carbon materials. In addition, the synthesis of certain electrically conductive polymers, such as polyaniline, must be carried out in a strongly acidic environment (1M Hcl or 1M H ₂ SO ₄ ) to provide a linear, electrically conductive polyaniline structure formed in a head-to-tail fashion (J.-C. Chiang, AG Mac Diarmid, Synthetic Metals 13 (1986) 193-205; Y. Cao, P. Smith, AJ Heeger, Synthetic Metals 32 (1989) 263-281). This requires the availability of corrosion resistant equipment.

The electrical conductivity of polymers in composite materials is achieved, as a rule, by acid doping. In this case, acid anions are a charge of compensating anions in the main chain of electrically conductive polymers.

As acidic doping agents, both low molecular weight strong acids (sulfuric, hydrochloric, sulfocamphoric, toluenesulfonic, etc.) and polysulfonic acids (poly (2-acrylamido-2-methyl-1-propanesulfonic acid), sulfonated polystyrene, etc.) and micelle-forming agents are used. hydrophobic sulfonic acids or their salts (sodium dodecyl sulfonate, dodecylbenzenesulfonic acid) (MGHan, SH Foulger, Small, 2 (2006) 1164-1169; V. Rumbau, JA Pomposo, JA Alduncin, H. Grande, D. Mecerreyes, E. Ochoteco , Enzyme and microbial technology, 40 (2007) 1412-1421; US Patent 7,230,071; US Patent 7,462,298; Eur. Patent 686662; US Patent 5,792,558).

The use of biocatalysts to obtain composites based on electrically conductive polymers and carbon materials is an alternative to chemical and electrochemical synthesis and is of great interest because it allows the process of oxidative polymerization in environmentally friendly and relatively mild conditions (in aqueous solutions, at room temperature, atmospheric pressure, and slightly acidic the pH of the reaction medium), without the formation of a large number of toxic by-products, and to obtain a polymer, n f contaminated with oxidizer decomposition products. Thus, this approach largely meets the requirements of green chemistry.

As a prototype, the method for the chemical preparation of a composite material based on multi-walled carbon nanotubes and electrically conductive polymers (E. Frackowiak, V. Khomenko, K. Jurewicz, k. Lota, F. Beguin, J. Power Sources, 2006, 153, 413-418 ), including the following sequence of operations:

- preparing an aqueous or non-aqueous dispersion of carbon nanomaterial containing monomer by ultrasonic treatment;

- preparation of an aqueous / non-aqueous solution of an oxidizing agent;

- initiating the polymerization of the monomer by adding an oxidizing solution to the dispersion of the nanomaterial containing the monomer.

For the chemical preparation of composites based on multi-walled carbon nanotubes and electrically conductive polymers, FeCl ₃ were used as oxidizing agents for monomers; Fe (ClO ₄ ) ₃ ; K ₂ Cr ₂ O ₇ . Electrically conductive polypyrrole and polyaniline were deposited on the surface of carbon nanotubes from strongly acidic aqueous solutions of hydrochloric acid. Since the solubility of 3,4-ethylenedioxythiophene in aqueous solutions is very limited, its polymerization was carried out in acetonitrile. A disadvantage of the known method of carrying out oxidative gulimerization of monomers is the need to use a strongly acidic medium or an organic solvent and high concentrations of oxidizing agent equivalent or higher than the concentrations of the corresponding monomers.

The technical task and, accordingly, the technical result of the invention is the development of a simple, environmentally friendly method for producing composites based on electrically conductive polymers and carbon materials for electrodes of supercapacitors of high specific capacity with a low content of ecotoxicants in the reaction mixture. The problem is solved by the proposed method, providing for the oxidative polymerization of monomers on the surface of a carbon material in the presence of copper-containing oxidase (laccase) and a redox mediator of this enzyme, which belongs to salts of transition metal complexes and accelerates the enzymatic polymerization of monomers.

The implementation of the technical task and obtaining the technical result is ensured by the use of the following set of essential features.

A method of producing a composite material for a supercapacitor electrode, including the synthesis of electrically conductive polymers or their substituted derivatives in the process of oxidative polymerization of the corresponding monomers on the surface of carbon materials,

polymerization is carried out in the presence of a laccase enzyme, acidic dopants, an oxidizing agent and a redox mediator of the enzymatic reaction dissolved in the reaction mixture, while

- polymerization is carried out at a pH of 3.5-4.5, a temperature of 0-30 ° C;

- as electroconductive polymers use polyaniline or

polypyrrole or polyethylenedioxythiophene;

- to carry out oxidative polymerization using the appropriate freshly distilled monomers obtained by distillation under vacuum;

- mushroom laccases are used as biocatalysts;

 - molecular oxygen is used as an oxidizing agent;

 - as solvents use aqueous or aqueous-organic solutions;

- as a redox mediator of the enzymatic reaction, a salt of a transition metal cyanide complex is used: octocyanomolybdate (4+), the redox potential (E0) of which is 0.78 V relative to a normal hydrogen electrode (NVE);

- strong inorganic acids, organic sulfonic acids, polysulfonic acids or their salts are used as acidic dopants;

- mushrooms such as Pleurotus or Phlebia or Trametes or Serrena or Panus (Trametes hirsuta or Trametes pubescens or Trametes ochracea or Cerrena maxima or Coriolopsis fulvocinerea or Trametes versicolor or Panus tigrinus) are used to obtain the laccase enzyme.

The proposal is explained as follows.

Laccase (p-diphenol: oxygen oxidoreductase, classification of enzymes 1.10.3.2 catalyzes the oxidation of a wide range of organic and inorganic compounds, by molecular oxygen and its simultaneous reduction to water. The named oxidase is a commercially available enzyme and can be obtained by a standard method. In principle, producers of these of enzymes can be either natural organisms or organisms modified by genetic engineering methods.Fungi, such as Pleurotus, Phlebia, Trametes, Serrena, Panus {Trametes hirsuta, Trametes pubescens, Trametes ochracea, Cerrena maxima, Coriolopsis fulvocinerea, Trametes versicolor, Panus tigrinus).

Laccases can directly oxidize compounds whose potentials are lower or slightly exceed the redox potential of the primary electron acceptor (T1 center) of copper-containing oxidases. If the oxidation potential of oxidase substrates is exceeded by more than 200 mV compared to the T1 center of the enzyme (the primary electron acceptor in the active center of oxidases), the efficiency of enzymatic catalysis involving these enzymes decreases, or the reaction does not proceed at all. The oxidation potentials of aniline, pyrrole, thiophene and 3,4 ethylenedioxythiophene are high. Therefore, the aniline oxidation rate involving laccases is relatively low, and the EDOT oxidation reaction does not occur at all.

Redox mediators are low molecular weight compounds that are laccase substrates, which form stable, highly reactive products as a result of enzymatic oxidation. The latter in diffusion-controlled mode can enter into chemical (non-enzymatic) reactions with other compounds that are not oxidized with the participation of only copper-containing oxidases. In this case, the oxidized redox mediator is restored by the oxidizable compound to its original form and thus a closed cycle is formed. The oxidized form of the redox mediator formed during the enzymatic reaction can further oxidize compounds with ionization potentials exceeding the redox potential T1 of the laccase center and accelerate the oxidation reaction of these compounds, with the concentration of polymerization by the free-radical mechanism.

The proposed method includes one stage: the preparation of composite materials is carried out by the synthesis of electrically conductive polymers (polyaniline, polypyrrole, polythiophene) or their substituted derivatives during the oxidative polymerization of the corresponding monomers on the surface of carbon materials and in the presence of redox mediator, acid dopant and oxidizing agent dissolved in the reaction mixture - molecular oxygen - at pH 3.5-4.5, temperature 0-30 ° C, catalyzed by laccase. As solvents, aqueous or organic solutions are used.

A salt of a transition metal cyanide complex is used as a redox mediator of the enzymatic reaction: octocyanomolybdate (4+), the redox potential (E0) of which is 0.78 V relative to a normal hydrogen electrode (NVE). As the oxidizing agent, molecular oxygen is used. As biocatalysts, mushroom laccases are used. Strong acidic inorganic acids, organic sulfonic acids, polysulfonic acids or their salts are used as an acid dopant.

The enzymatic method for producing composite materials based on electrically conductive polymers and carbon materials for supercapacitor electrodes using low concentrations of inorganic reaction enhancers and acid dopant is environmentally friendly, one-step, allows the process of oxidative polymerization of monomers on the surface of a carbon material with a high speed and high kinetic yield controlled mode.

The invention is illustrated by the following examples.

In the examples, the specific capacity of the composite material obtained by the proposed method was determined as follows.

Used down conductor: carbon foil sheet 5 mm wide and 30 mm long and 0.2 mm thick;

reagents: 1 M solution of sulfuric acid, prepared with deionized water; freshly distilled under vacuum aniline and pyrrole; multi-walled carbon nanotubes “Taunit M”; after treatment with 70% nitric acid at 90 ° C for 6 h (functionalized multi-walled carbon nanotubes (fMCNTs); soot “Vulkan XC 72R”;

equipment: potentiostat / galvanostat (AUTOLAB) used for cyclic voltammetry and chronopotentiometry; Ag / AgCl (saturated KCl) - reference electrode; 3-electrode glass electrochemical cell; platinum plate - auxiliary electrode; ultrasonic bath (FinnSonic).

Measurement: 1. Voltammetric determination of specific capacity. The measurement procedure consists of two stages. An electrode with a composite material was immersed in an electrolyte and held at a potential of 0.1 V (rel. Ag / AgCl) for 5 min. Then a cyclic voltammogram was recorded in the potential range of -0.1 ÷ 0.6 V with a potential change rate of 50 mV / s. The capacity of the composite material was calculated as i / υ, where i is the average current value, υ is the rate of change of the electrode potential. The calculated capacitance value was then referred to the weight of the composite deposited on the electrode.

2. Determination of the specific capacity of the composite material from galvanostatic measurements. The composite electrode was kept in an electrolyte solution for 5 min at a potential of -0.1 V rel. Ag / AgCl. Then, a charge / discharge curve was recorded in the range of potentials from -0.1 to 0.6 V at various current densities per unit weight of the composite material. The capacity was calculated as i × t / ΔU, where i is the discharge current; t is the discharge time; ΔU is the change in voltage during the discharge.

Example No. 1. In 10 ml of deionized water, equimolar amounts of S-sulfocamphoric acid and freshly distilled aniline were dissolved with a final concentration of 129 mM with stirring. After complete dissolution of the components, the pH of the reaction mixture was adjusted to a value of 2.8 with a solution of S-sulfocamphoric acid. To the resulting solution, 15 mg of Taunit M modified multi-walled carbon nanotubes were added. The resulting dispersion was evacuated for 10 min to increase the wettability of the internal cavities of the MWCNTs with the reaction solution and then processed in an ultrasonic bath for 3 hours. To the obtained dispersion of carbon nanotubes, potassium octocyanolybdate (4+) solution with a final concentration was added with constant stirring in the reaction medium 0.05 mmol (mmol) and stirring was continued for 5 minutes. The aniline polymerization reaction on the surface of the MWCNTs was initiated by adding laccase from the fungus Trametes hirsuta with specific activity in the reaction medium of 4 international activity units (ME) per ml. The composite material was synthesized at room temperature (20–22 ° C) under aerobic conditions with constant stirring for 24 h. As the reaction ended, the precipitate formed was separated by centrifugation at 8000 g, washed four times with deionized water, once with ethanol and dried at 60 ° C for 48 hours

The resulting composite was applied to the collector using Nafion as a binder (the Nafion content in the composite / Nafion mixture was 0.025 wt.%). The specific capacity of the obtained composite during galvanostatic measurement by the discharge of the electrode at a current density of 1.32 A / g of the composite material was 296 F / g, measured from cyclic voltammograms at an electrode potential change rate of 50 mV / s - 320 F / g of the composite material.

Example No. 2. Sodium dodecylbenzenesulfonate (DBSNa) with a final concentration of 25 mm was dissolved in 10 ml of 0.05 m Na-citrate-phosphate buffer with a pH of 3.5. 10 mg of TaunitM mMNTT was added to the solution. The resulting dispersion was evacuated for 10 minutes, and then treated for 3 hours in an ultrasonic bath. Freshly distilled aniline with a final concentration of 25 mM was added dropwise to the obtained stable dispersion of fMCNTs with constant stirring, and the pH was adjusted to 3.8 with a solution of H ₃ PO ₄ . Then, potassium octocyanolybdate (4+) with a final concentration in the reaction medium of 0.05 mM was added to the dispersion of carbon nanotubes. The aniline polymerization reaction on the surface of the fMCNTs was initiated by adding mushroom laccase with a specific activity of 4 IU / ml in the reaction medium and left under continuous stirring for 24 hours. After the completion of the reaction, the polyaniline was doped with 1% aqueous ammonia solution with constant stirring for 24 hours. The precipitate of the composite was separated by centrifugation. Washed 5 times with deionized water and re-doped with 25 mM S-sulfocamphoric acid solution. The precipitate formed was separated by centrifugation, washed twice with deionized water, and then 1 time with ethanol and dried at 60 ° C for 48 h.

The resulting composite was applied to the collector as described in example No. 1. The specific capacitance of the composite was 278 F / g from galvanostatic measurements at a current of 1.1 A / g, and measured from cyclic voltammograms - 301 F / g at an electrode potential change rate of 50 mV / s.

Example No. 3. The synthesis of the composite was carried out similarly to that described in example No. 1, but Vulkan carbon black was used as the carbon matrix. The specific capacity of the obtained composite sample, measured by the galvanostatic method, was 217 F / g at a density of 0.93 A / g, and by cyclic voltammetry at an electrode potential change rate of 241 F / g at an electrode potential change rate of 50 mV / s.

Example No. 4. Freshly distilled pyrrole with a final concentration of 50 mM was dissolved in 10 ml of deionized water containing 50 mM toluenesulfonic acid. After complete dissolution of the pyrrole, the pH of the solution was adjusted to a value of 3.5. To the resulting solution was added 10 mg fMCNTs. The resulting mMNTT dispersion was evacuated for 10 min and then processed in an ultrasonic bath for 3 h. Potassium octocyanomolybdate (4+) potassium with a final concentration in the reaction medium of 0.1 mM was added to the obtained dispersion and stirred for 5 min. The pyrrole polymerization reaction on the surface of the fMCNTs was initiated by the addition of a laccase enzyme with a specific activity of 3 IU / ml in the reaction medium. The synthesis of the composite material was carried out at room temperature for 20 hours. After the polymerization reaction was completed, the precipitate was washed 4 times with deionized water and dried at 60 ° for 48 hours. The resulting composite was applied to the collector as described in example No. 1. The specific capacitance of the composite was 219 F / g from galvanostatic measurements at a current density of 1.1 A / g and measured from cyclic voltammograms at an electrode potential scan rate of 50 mV / s — 249 F / g.

Claims (10)

1. A method of producing a composite material for a supercapacitor electrode, including the synthesis of electrically conductive polymers or their substituted derivatives during the oxidative polymerization of the corresponding monomers on the surface of carbon materials, characterized in that the polymerization is carried out in the presence of laccase enzyme, acidic dopants, oxidizing agent and redox dissolved in the reaction mixture -mediator of the enzymatic reaction. 2. The method according to claim 1, characterized in that the polymerization is carried out at a pH of 3.5-4.5 and a temperature of 0-30 ° C. 3. The method according to claim 1, characterized in that as the electrically conductive polymers use polyaniline or polypyrrole, or polyethylenethiophene. 4. The method according to claim 1, characterized in that for the oxidative polymerization using the appropriate monomers obtained by fresh distillation. 5. The method according to claim 1, characterized in that mushroom laccases are used as biocatalysts. 6. The method according to claim 1, characterized in that molecular oxygen is used as the oxidizing agent. 7. The method according to claim 1, characterized in that as solvents use aqueous or aqueous-organic solutions. 8. The method according to claim 1, characterized in that as a redox mediator of the enzymatic reaction, a salt of a transition metal cyanide complex is used: octocyanomolybdate (4+), the redox potential (E0) of which is 0.78 V relative to a normal hydrogen electrode (NVE) ) 9. The method according to claim 1, characterized in that strong acidic inorganic acids, organic sulfonic acids, polysulfonic acids or their salts are used as acidic dopants. 10. The method according to claim 5, characterized in that to obtain the laccase enzyme, fungi are used, such as Pleurotus or Phlebia or Trametes or Cerrena or Panus (Trametes hirsuta or Trametes pubescens or Trametes ochracea or Cerrena maxima or Coriolopsis fulvocinerea or Trametes versicolor or Panmetes tigrinus).