Rigid / flexible composite polymer anode material prepared using variable temperature cycle technology and preparation method

Abstract

The present invention provides a rigid-flexible composite polymer anode material and a preparation method prepared by variable temperature cycle technology. The material has unique properties such as high porosity and conductivity, good hydrophilicity and biocompatibility, good mechanical strength and bioelectrocatalytic activity, and has the characteristics of hydrogels and the excellent electrochemical activity of conductive polymers and nitrogen-doped carbon nanotubes. It is an ideal anode for bioelectrochemical systems (BES). It is conducive to the selective attachment of electricity-producing microorganisms and extracellular electron transfer, as well as the rapid transmission and degradation of the matrix. In addition, the excellent mechanical properties make it possible for the long-term and stable operation of BES. The material manufacturing process of the present invention is simple and low in cost. The power generation capacity of the BES system constructed with the material as the anode is greatly improved, and the anode bioelectrocatalytic activity is significantly enhanced, which has great application prospects.

Description

Technical Field

[0001] The present invention relates to a bioelectrochemical system, in particular to a rigid / flexible composite polymer anode material prepared by using variable temperature cycle technology and applied to the bioelectrochemical system, and a preparation method thereof. Background Art

[0002] The insufficient supply of fossil fuels, especially oil and natural gas, and their negative impact on the environment directly lead to unsustainable development around the world. Therefore, carbon-free, renewable and alternative energy sources have become the focus of attention, and the use of biotechnology has become one of the solutions. The bioelectrochemical system (BES) is a device that combines electrochemical and microbial action. It uses microorganisms attached to the anode surface to degrade organic matter and recover the chemical energy stored in the organic matter. It can be used to generate electricity and hydrogen, and can also simultaneously achieve wastewater purification, solving energy problems and protecting the environment at the same time.

[0003] The main components of the BES system are the reactor, anode and cathode. The anode is one of the key components of the BES system because of its important influence on bacterial attachment, growth and extracellular electron transfer (EET). The electrode material used as the anode in the BES system should have the characteristics of high conductivity, mechanical properties, biocompatibility, chemical stability in the anolyte, high specific surface area, high porosity, and be conducive to microbial attachment, while promoting electron transfer and transmission. The research on the BES anode has always been the focus and difficulty of research in this field, but the current problems of low microbial attachment on the anode and slow electron transfer between microorganisms and the anode have hindered the practical application of the BES system. It is of great research significance to develop new and efficient anode materials, solve the problems of anode construction and extracellular electron transfer process in the BES system, and develop new technologies for the recycling of carbon resources. Summary of the invention

[0004] The object of the present invention is to provide a rigid / flexible composite polymer anode material prepared by using variable temperature cycle technology and a preparation method thereof.

[0005] The object of the present invention is achieved in that:

[0006] A rigid-flexible composite polymer conductive hydrogel anode material with an open-through-macroporous structure. The present invention makes a comprehensive design from the aspects of the structure, composition and properties of the anode material, so that it has the characteristics of an ideal BES anode material.

[0007] From the perspective of structure and properties, the material of the present invention is a rigid-flexible composite polymer conductive hydrogel. Conductive hydrogel is an essentially stretchable ion conductor, a flexible material with a three-dimensional network structure and a high water content, good biocompatibility, and provides a relatively large attachment area for microorganisms. The conductive polymer hydrogel of the present invention not only gives the hydrogel high conductivity, but also overcomes the inherent high rigidity of the conductive polymer conjugated system and the hydrophobicity caused by the π-π stacking of the chain. Therefore, the material of the present invention has the advantages of high conductivity, good hydrophilicity, good biocompatibility, hierarchical interconnected macroporous structure, etc., which increases a large number of places for the attachment of microorganisms, and a large specific surface area can provide more bioelectrocatalytic active sites, which is conducive to the transmission and utilization of the matrix.

[0008] From the aspect of material composition, the main components of the material of the present invention are rigid polymer polypyrrole (PPY), nitrogen-doped carbon nanotubes and flexible polymer polyvinyl alcohol (PVA).

[0009] As a conductive polymer material, PPY conductive polymer has high bioelectrocatalytic activity and has a large number of applications in BES. Although PPY has high conductivity, environmental stability and good redox properties, it has poor processability and lacks necessary mechanical properties. The composite flexible polymer PVA has the advantages of hydrophilicity, ductility, good biocompatibility, good adhesion to carbon fiber and low cost and easy availability. The present invention prepares a composite hydrogel with a flexible polymer PVA with good mechanical properties and PPY with high electrocatalytic activity, which can solve the problem of poor processing performance and mechanical properties of PPY. Combining PVA with PPY can improve the mechanical strength of the composite material and the bioelectrocatalytic activity of the material. In addition, PVA added to the conductive polymer can also resist the volume expansion and contraction caused by the insertion and removal of electrolyte ions into the electrode material, thereby maintaining the stability of the composite conductive polymer material. Nitrogen-doped nanocarbon materials such as N-CNT have rich catalytic sites and conductivity, and the pyrrole nitrogen component in N doping can promote the electron transfer of certain electrogenic bacteria at the anode, which can improve the power density of BES. Therefore, the composite material PVA / PPY / N-CNT synthesized by these three substances can significantly improve the electrode performance.

[0010] From the perspective of preparation technology, the present invention utilizes variable temperature cycle technology. The PVA / PPY / N-CNT electrode material is synthesized by alternating normal temperature and low temperature and cyclic multiple treatments. The microstructure of the conductive hydrogel is improved by variable temperature alternating cycle treatment, and the pore size of the hydrogel is increased, thereby improving the performance of the material, providing more attachment sites for microorganisms, and enhancing material transfer, thereby improving the performance of BES. In addition, the excellent mechanical properties make it possible for the long-term stable operation of BES.

[0011] The electrode preparation method is achieved by the following technical solution:

[0012] Preparation process: preparation of polyvinyl alcohol solution, preparation of PVA / PPY / N-CNT composite hydrogel material, preparation of PVA / PPY / N-CNT composite hydrogel electrode material.

[0013] (1) Preparation of polyvinyl alcohol solution: Weigh a certain amount of PVA and dissolve it in deionized water, and place it in a reflux device. After swelling for a certain period of time at a constant temperature of 60°C, stir it with a magnetic stirrer at a constant temperature of 95°C for several hours to prepare a PVA solution with a mass fraction of 5-15%.

[0014] (2) Preparation of PVA / PPY / N-CNT composite hydrogel materials

[0015] Preparation of solution A: Weigh a certain amount of ammonium persulfate (APS), dissolve APS in deionized water under an ice-water bath to prepare an ammonium persulfate solution of a certain concentration.

[0016] Preparation of solution B: In an ice-water bath, N-CNT is ultrasonically dissolved in a mixed solution of PVA and phytic acid (PA), and then pyrrole PY is added and stirred evenly. Then solution A is added to solution B and mixed quickly to prepare a dilute composite hydrogel material.

[0017] (3) Preparation of PVA / PPY / N-CNT composite hydrogel electrode materials

[0018] After mixing solution A and solution B evenly, the obtained dilute composite hydrogel material is immediately coated on a current collector such as hydrophilic carbon felt for polymerization for one week, and the electrode is immersed in deionized water for 24 hours to remove impurities. Then the electrode is treated with variable temperature cycle technology, and after 2-10 cycles, it is immersed in deionized water for 24 hours to prepare an electrode material.

[0019] The nitrogen-doped nano-carbon material is a one-dimensional or two-dimensional carbon material, such as one of nitrogen-doped nano-carbon powder, carbon nanotubes and graphene, or may be various nano-carbon materials not doped with nitrogen or transition metal carbide Mxene and the like.

[0020] The current collector may be carbon felt, carbon cloth, carbon paper or various metal current collectors.

[0021] The rigid polymer may be one of conductive polymers with capacitance properties such as polypyrrole, polyaniline, and polythiophene.

[0022] The rigid-flexible composite polymer conductive hydrogel electrode material and carbon felt prepared by the present invention were used as anodes to construct a bioelectrochemical system, and 2000 mg / L sodium acetate was used as fuel to investigate the power generation performance of the BES constructed with the anode material of the present invention. The results are shown in the accompanying drawings.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The rigid-flexible composite polymer conductive hydrogel anode material prepared by the variable temperature cycle technology of the present invention has unique properties such as high porosity, high conductivity, good hydrophilicity and biocompatibility, good mechanical strength and bioelectrocatalytic activity. The material has the characteristics of hydrogel and the excellent electrochemical activity of conductive polymers and nitrogen-doped carbon nanotubes, and is an ideal anode for BES. It is conducive to the selective attachment of electricity-producing microorganisms and extracellular electron transfer, as well as the rapid transmission and degradation of the matrix. In addition, the excellent mechanical properties make it possible for the long-term and stable operation of BES. The material of the present invention has a simple manufacturing process and low cost. The power generation capacity of the BES system constructed with the material of the present invention as the anode is greatly improved, and the anode polarization phenomenon is significantly reduced, which has great application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the power density curve and polarization curve of the BES constructed with the PVA / PPY / N-CNT electrode and carbon felt as anode of the present invention;

[0026] Figure 2 is the polarization curve of the PVA / PPY / N-CNT and carbon felt bioanode of the present invention;

[0027] Figure 3 It is the AC impedance diagram of the PVA / PPY / N-CNT and carbon felt bioanode of the present invention. DETAILED DESCRIPTION

[0028] The present invention is described in more detail below with reference to the accompanying drawings:

[0029] 1. Preparation of PVA / PPY / N-CNT

[0030] Preparation of solution A: Weigh 0.5460 g of ammonium persulfate APS and dissolve it in 2.00 mL of deionized water.

[0031] Preparation of solution B: First, ultrasonically dissolve 0.0500g N-CNT in a mixed solution of 1.50mL of 10% PVA and 0.62mL PA, and add 0.34mL PY solution and 0.50mL deionized water to the mixed solution in turn and stir evenly. After solution A and solution B are evenly mixed, they are immediately coated on a hydrophilic carbon felt current collector for polymerization for one week, and the electrode is immersed in deionized water for 24 hours. The electrode is then subjected to a variable temperature cycle technology treatment of -20°C and room temperature. After 5 cycles, it is soaked in deionized water for 24 hours to prepare the electrode material of the present invention.

[0032] 2. A single-chamber microbial fuel cell (MFC) of one of the BES types was constructed using the PVA / PPY / N-CNT electrode (2 cm×2 cm) of the present invention as the anode to investigate its power generation performance. 2000 mg / L sodium acetate was used as the fuel and sea mud was the source of the bacteria for the MFC. The polarization curve and power density curve of the MFC were measured by changing the connection resistance of the external circuit. The experimental results are shown in Figure 2. Figure 1 As shown. Figure 1 It can be seen that the maximum output power of the MFC constructed with the PVA / PPY / N-CNT electrode of the present invention as the anode is 1806.3 mW / m2, which is 9.88 times the maximum output power of the MFC with carbon felt anode (182.8mW / m2). The polarization phenomenon of the battery is greatly reduced, and the power generation capacity of the system is greatly improved.

[0033] Depend on Figure 2 and Figure 3 It can be seen that the PVA / PPY / N-CNT anode of the present invention has a more negative open circuit potential, lower polarization and smaller charge transfer impedance than the carbon felt anode. The experimental results show that the PVA / PPY / N-CNT anode of the present invention has good bioelectrocatalytic activity and extracellular electron transfer ability, which improves the power generation performance of the BES system.

[0034] Therefore, the present invention provides a new rigid-flexible composite polymer anode material prepared by variable temperature cycle technology. The hydrogel anode material with open-through-macroporous structure has the characteristics of hydrogel and the excellent electrochemical activity of conductive polymer and nitrogen-doped carbon nanotubes, and has the advantages of being conducive to microbial attachment, matrix transmission and degradation, high biocompatibility and bioelectrocatalytic activity, good hydrophilicity, and low charge transfer impedance. In addition, the preparation process is simple and the cost is low, and it has a wide range of application prospects in practical applications.

Claims

1. A method for preparing a rigid / flexible composite polymer anode material using variable temperature cycle technology, characterized in that: The steps include: (1) Preparation of polyvinyl alcohol solution: PVA was weighed and dissolved in deionized water, placed in a reflux device, and swelled at a constant temperature of 60°C for a certain period of time, and then magnetically stirred at a constant temperature of 95°C for several hours to prepare a PVA solution with a mass fraction of 5-15%; (2) Preparation of PVA / PPY / N-CNT composite hydrogel materials; Preparation of solution A: Weigh a certain amount of ammonium persulfate (APS), dissolve APS in deionized water under ice water bath to prepare a certain concentration of ammonium persulfate solution; Preparation of solution B: N-CNT was ultrasonically dissolved in a mixed solution of PVA and phytic acid (PA) in an ice-water bath, and then pyrrole PY was added and stirred evenly; Then, solution A is added to solution B and mixed rapidly to prepare a dilute composite hydrogel material; (3) Preparation of PVA / PPY / N-CNT composite hydrogel electrode materials; The dilute composite hydrogel material obtained after evenly mixing solution A and solution B is immediately coated on the hydrophilic carbon felt current collector for polymerization for one week. The electrode is immersed in deionized water for 24 hours to remove impurities. The electrode is then treated with variable temperature cycling technology. After 2-10 cycles, it is immersed in deionized water for 24 hours to prepare an electrode material.

2. The method for preparing a rigid / flexible composite polymer anode material using variable temperature cycle technology according to claim 1, characterized in that: The N-CNT material is a one-dimensional or two-dimensional carbon material, various nitrogen-free nano-carbon materials or transition metal carbide Mxene.

3. The method for preparing a rigid / flexible composite polymer anode material using variable temperature cycle technology according to claim 1, characterized in that: The current collector is carbon felt, carbon cloth, carbon paper or various metal current collectors.

4. A rigid / flexible composite polymer anode material prepared using variable temperature cycling technology, characterized in that: Prepared by any one of the methods described in claims 1-3.

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