A flexible air biocathode containing a superhydrophobic interface, a method of making, and a fuel cell comprising the same

Abstract

The application discloses a flexible air biological cathode containing a super-hydrophobic interface, a preparation method and a fuel cell containing the air biological cathode, and belongs to the technical field of bioelectrochemistry. The application uses a flexible protective film as a flexible matrix, a screen-printed circuit as a wire, and a hydrophobic porous matrix as an air diffusion module and a current collector, and a flexible air base electrode is constructed through a'sandwich' structure. The super-hydrophobic property is formed by depositing Pt particles with special morphology on the surface of the hydrophobic porous matrix, and then an enzyme membrane layer with catalytic oxygen reduction is fixed on the super-hydrophobic surface, so that a flexible air biological cathode containing a super-hydrophobic interface is formed. The biological cathode can be used on a flexible wearable biological fuel cell, and has the characteristics of high oxygen reduction current density, simple manufacturing process and low cost. The preparation method can be expanded to develop flexible air diffusion electrodes of flexible porous matrix electrodes such as carbon cloth, carbon felt and foam metal sheets.

Description

Technical Field

[0001] This invention belongs to the field of bioelectrochemical technology, specifically relating to a flexible air biocathode with a superhydrophobic interface, its preparation method, and a biofuel cell containing the biocathode. Background Technology

[0002] In recent years, flexible wearable electronic devices have attracted much attention due to their broad application prospects in real-time monitoring of human physical signs and chemical indicators. Developing energy conversion or storage devices that are well-matched to flexible wearable electronic devices is crucial. Flexible enzyme biofuel cells, with their characteristics of directly utilizing human body fluids as energy, good skin compatibility, good biocompatibility, and environmental friendliness, have become one of the ideal power sources for flexible wearable electronic devices. Flexible enzyme biofuel cells used in wearable electronic devices typically use lactic acid from sweat as biofuel. The anode catalyzes the production of electrons from lactic acid through lactate oxidase, while the cathode accepts electrons through the reduction of oxygen by bilirubin oxidase (BOD) or laccase (Lac), thereby realizing electron flow and generating electrical energy. However, the extremely low dissolved oxygen concentration in sweat causes the cathode's limiting catalytic current density to be insufficient to match the anode's catalytic current density, making cathode performance a limiting factor in the overall battery performance and hindering the development of this flexible enzyme fuel cell towards practical application. Adding an air-diffusion biocathode to a flexible enzyme biofuel cell is one effective way to improve the overall performance of the cell. However, the power density of currently reported breathable flexible enzyme biofuel cells is only in the tens to hundreds of microwatts per square centimeter range, and the dissolved oxygen concentration in sweat is typically around 0.22–0.31 mmol / L. -1 The concentration of lactic acid is approximately 5–40 mmol / L. -1 Under highly efficient bioelectrocatalytic conditions, this significant difference in substrate concentration can lead to a severe mismatch in anode and cathode performance due to substrate diffusion control. This makes cathode performance a rate-limiting factor in the performance of flexible wearable enzyme biofuel cells, insufficient to provide adequate power for flexible wearable electronic devices. Therefore, there is an urgent need to develop a high-performance flexible air biocathode that is simple to fabricate, low in cost, and can be integrated with a bioanode. Summary of the Invention

[0003] In view of this, the present invention provides a flexible air biocathode containing a superhydrophobic interface and a method for preparing the same. This method can be further extended to the preparation of a breathable flexible wearable enzyme biofuel cell. By superhydrophobic modification of the hydrophobic porous matrix, the performance of the biocathode can be greatly improved, thereby improving the overall performance of the flexible wearable enzyme biofuel cell.

[0004] According to one embodiment of the present invention, the present invention first provides a flexible air diffusion substrate electrode, the air diffusion substrate electrode comprising a pair of flexible protective films as an outer layer structure, a screen-printed circuit as a middle layer structure, a copper sheet, and a hydrophobic porous matrix, wherein the outer layer structure and the middle layer structure are formed into a sandwich structure by a hot pressing process.

[0005] According to one embodiment of the present invention, the hydrophobic porous matrix can serve as an air diffusion module and current collector for a base electrode.

[0006] According to one embodiment of the present invention, the hydrophobic porous matrix may be a hydrophobic porous matrix such as hydrophobic carbon paper, hydrophobic carbon cloth, and hydrophobic carbon felt.

[0007] According to one embodiment of the present invention, the pair of flexible protective films each contain hot melt adhesive and the sides containing hot melt adhesive are opposite to each other, and the whole is opaque frosted.

[0008] According to one embodiment of the present invention, the hot melt adhesive may be one of polyurethane (TPU) hot melt adhesive, copolyester (PES) hot melt adhesive, polyamide (PA) hot melt adhesive, polyolefin (PO) hot melt adhesive, and vinyl acetate copolymer (EVA) hot melt adhesive.

[0009] According to one embodiment of the present invention, the flexible protective film is selected from one of the following materials: TPU hot melt adhesive film, PES hot melt adhesive film, PA hot melt adhesive film, PO hot melt adhesive film and EVA hot melt adhesive film with a thickness of 60~100 μm.

[0010] According to one embodiment of the present invention, the flexible protective film is preferably a TPU hot melt adhesive film.

[0011] According to one embodiment of the present invention, the flexible protective film has an open electrode hole and a tab hole, the diameter of the electrode hole is 4 mm, the diameter of the tab hole is 3 mm, and the diameter of the copper sheet is 4 mm.

[0012] According to one embodiment of the present invention, the hydrophobic porous matrix is ​​fixed on the screen-printed circuit around the electrode holes by a hot-pressing process at a temperature of 150°C.

[0013] According to one embodiment of the present invention, preferably, the material used in the screen-printed circuit is commercially available oil-based silver paste (silver content greater than 68%), which has good conductivity after curing.

[0014] According to one embodiment of the present invention, the hydrophobic carbon paper is preferably hydrophobic carbon paper from Toray Industries, Inc. of Japan.

[0015] According to another embodiment of the present invention, the present invention also provides a flexible air biocathode containing a superhydrophobic interface, the air biocathode comprising the above-mentioned air diffusion substrate electrode; the air biocathode further comprising an enzyme membrane modification layer located on the above-mentioned hydrophobic porous matrix and a superhydrophobic interface layer located between the two.

[0016] According to one embodiment of the present invention, the superhydrophobic interface layer may also be a superhydrophobic modified layer composed of metal particles or their alloys that have oxygen-reducing properties.

[0017] According to one embodiment of the present invention, the metal particles or their alloy are preferably Pt metal particles or Pt alloys.

[0018] According to one embodiment of the present invention, the superhydrophobic interface layer is preferably composed of Pt particles, wherein the Pt particles have a cactus-like morphology and a particle size of 100~800 nm, and the water contact angle of the interface formed by the Pt particles is greater than 120°.

[0019] According to one embodiment of the present invention, the Pt alloy may be one of Pt-Co, Pt-Ni, Pt-Cu, and Pt-Zn.

[0020] According to one embodiment of the present invention, the enzyme membrane modification layer includes a copper-containing oxidoreductase, an enzyme carrier material, and a membrane matrix. The copper-containing oxidoreductase includes bilirubin oxidase (BOD) and laccase (Lac). The enzyme carrier material includes carbon nanotubes and graphene. The membrane matrix includes Nafion solution and chitosan solution.

[0021] According to another embodiment of the present invention, the present invention also provides a method for preparing the above-mentioned flexible air diffusion substrate electrode, the preparation steps including: screen printing conductive lines on a protective film containing hot melt adhesive; punching electrode holes consistent with the screen-printed lines on the two protective films using a hole puncher or laser cutter; fixing the air diffusion module to the screen-printed circuit around the electrode holes using a soldering iron; embedding the air diffusion module in the two flexible protective films using a molding machine; and integrally hot-pressing to form a flexible air diffusion substrate electrode with a sandwich structure.

[0022] According to one embodiment of the present invention, preferably, the hot pressing temperature of the sealing machine during the hot pressing process is 80~140°C and the pressure is 0.3 bar.

[0023] According to another embodiment of the present invention, the present invention also provides a method for preparing a flexible air biocathode with a superhydrophobic interface. By superhydrophobically modifying the surface of a hydrophobic porous matrix to increase the gas-liquid contact area, the oxygen supply of the air diffusion module is further increased, thereby improving the performance of the air biocathode. The method includes: (1) The hydrophobic porous matrix in the above-mentioned air diffusion substrate electrode is modified to be superhydrophobic. The modification steps include: the prepared air diffusion substrate electrode is subjected to 10 g L -1 In a mixed solution of HPtCl6, H2O and 1 M H2SO4, with Ag / AgCl as the reference electrode and Pt as the auxiliary electrode, electrodeposition was performed to form a superhydrophobic layer with uniform structure and cactus-like Pt particles on the surface of a hydrophobic porous matrix.

[0024] (2) Immobilization of the catalytic oxygen reductase membrane modified layer, the immobilization steps include: taking 5 mg mL -1 Carboxylated carbon nanotube suspension, 20 mg / mL -1 Add the BOD solution and 0.5 wt% Nafion (isopropanol) dilution solution to a test tube and mix thoroughly to form a mixture; then, wet the surface of the air diffusion substrate electrode containing the superhydrophobic interface prepared in step (1) with ethanol solution, and then quickly take the mixture and coat it evenly on the surface of the Pt superhydrophobic layer, and let it dry at room temperature.

[0025] According to one embodiment of the present invention, preferably, in step (1), the volume ratio of HPtCl6, H2O and H2SO4 is 13:12:2.

[0026] According to one embodiment of the present invention, preferably, in step (1), the electrodeposition conditions are electrodeposition for 200s at a voltage of -0.2 V vs. Ag / AgCl.

[0027] According to one embodiment of the present invention, preferably, in step (2), the BOD solution is pH 7.2, 0.1 mol / L. -1 PBS buffer.

[0028] According to one embodiment of the present invention, preferably, in step (2), the volume ratio of the carbon nanotube suspension, BOD solution, and Nafion dilution solution is 5:4:1.

[0029] According to one embodiment of the present invention, preferably, in step (2), the carbon nanotubes are carboxylated, with a carboxylation degree greater than 7% and a diameter of 20~30 nm.

[0030] According to one embodiment of the present invention, preferably, the BOD is derived from Myrothecium verrucaria strain (EC 1.3.3.5, 27 U mg). -1 ).

[0031] According to another embodiment of the present invention, the present invention also provides an application of catalytic reduction of oxygen using the above-mentioned air biocathode.

[0032] According to another embodiment of the present invention, the present invention also provides a biofuel cell, the biofuel cell comprising a bioanode and the above-mentioned air biocathode, the battery structure being arranged in an 'island-chain' array.

[0033] According to another embodiment of the present invention, the bioanode may be a modified electrode based on lactate oxidase (Lac) and glucose oxidase (GOx).

[0034] Beneficial effects (1) The flexible substrate used in the flexible air biocathode provided by the present invention is a commercially available protective film that is inexpensive and available in a variety of models, providing a new flexible substrate option for the preparation of flexible enzyme bioelectrodes.

[0035] (2) The superhydrophobic modification of the flexible air diffusion substrate electrode in this invention can increase the contact area between air and enzyme membrane, and greatly improve the diffusion rate of oxygen molecules in the air into the electrolyte.

[0036] (3) The superhydrophobic modification of the flexible air diffusion substrate electrode in this invention uses Pt particles that can form a synergistic effect of oxygen reduction with the enzyme membrane layer fixed behind it, which greatly improves the cathode catalytic oxygen reduction capability.

[0037] (4) The method for preparing a flexible air biocathode provided by this invention can be extended to prepare a breathable flexible wearable enzyme biofuel cell, the structure of which is as follows: Figure 2 As shown. Attached Figure Description

[0038] Figure 1 A schematic diagram of the structure of the flexible air biocathode with a superhydrophobic interface designed for this invention; Figure 2 A schematic diagram of a breathable flexible wearable enzyme biofuel cell structure that extends the preparation method of the present invention. Figure 3 This is a photograph of the hydrophobic carbon paper-based air diffusion matrix electrode prepared in Example 1. Figure 4 SEM image of the Nafion / BOD / CNT / Pt / CP electrode prepared in Example 2; Figure 5 The CV curves of the Nafion / BOD / CNT / Pt / CP electrode prepared in Example 3 and the control electrode are shown. Detailed Implementation

[0039] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0040] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0041] Example 1: Fabrication of a flexible air-diffusing substrate electrode (1) The 60 μm thick card protector film produced by Hangzhou Deli Group Co., Ltd. was selected as the flexible protective film; (2) Conductive lines are screen printed on the protective film containing hot melt adhesive. Commercial silver paste (silver content greater than 68%) is used as the conductive paste. The line width is 0.5 mm. The inner diameter of the ring in contact with the current collector is 4 mm and the outer diameter is 5 mm. The inner diameter of the ring in contact with the tab is 3 mm and the outer diameter is 4 mm. The distance between the centers of the two rings is 50 mm. (3) Hydrophobic carbon paper produced by Toray Corporation of Japan is selected as the current collector and cut into a circular piece with a diameter of 5 mm. Copper sheet with a diameter of 50 μm is selected as the electrode tab and cut into a circular piece with a diameter of 4 mm. (4) Use punches with diameters of 4 mm and 3 mm to punch holes in the protective film of the printed silver circuit according to the ring (inner circle) to form electrode holes and electrode tab holes respectively. Take another protective film and punch holes according to the same size. (5) Use a soldering iron to fix a 5 mm diameter hydrophobic carbon paper and a 4 mm diameter copper sheet onto the silver circuit around the electrode hole and the tab hole, respectively. (6) According to Figure 1 The electrode structure is obtained by pressing the two flexible protective films together into one layer using a molding machine at a temperature of 80°C and a pressure of 0.3 bar, thus obtaining the flexible air diffusion substrate electrode. The finished product is as follows: Figure 3 As shown.

[0042] Example 2: Preparation of a flexible air-diffusion biocathode with a modified layer containing a modified hydrophobic porous matrix (1) A flexible air diffusion substrate electrode was prepared according to the preparation steps of Example 1; (2) Electrodeposition of Pt nanoparticles to prepare a superhydrophobic interface, immersing one side of the hydrophobic carbon paper-based flexible air diffusion matrix electrode in 13 mL of 10 g L -1In a mixed solution prepared with HPtCl6, 12 mL of deionized water and 2 mL of 1 M H2SO4 (v:v:v=13:12:2), with Ag / AgCl as the reference electrode and Pt as the auxiliary electrode, deposition was carried out at a voltage of -0.2 V for 200 s. -1 (3) Prepare BOD-based enzyme membrane solutions by taking 50 μL and 5 mg / mL of each solution. -1 Carboxylated carbon nanotube suspension, 40 uL 20 mg mL -1 BOD solution (0.1 mol L) -1 Add PBS (pH 7.2) and 10 μL of 0.5 wt% Nafion solution (diluted with isopropanol) to a test tube and mix thoroughly. (4) Take 2 μL of ethanol solution to moisten the surface of the electrode prepared in step (2), and then quickly take 20 μL of the mixture prepared in step (3) to uniformly coat the electrode surface. Dry it at room temperature. Repeat this process 5 times to obtain an air biocathode, named Nafion / BOD / CNT / Pt / CP. Its surface microstructure is as follows: Figure 4 As shown.

[0043] Application example: Performance testing of biodiffusion cathodes The catalytic reduction performance of three biocathodes for oxygen in air diffusion mode was tested. The electrolyte was 0.1M PBS (pH 6), and the test method was cyclic voltammetry (CV). The scan range was -0.1 to 0.7 V vs. Ag / AgCl, and the scan rate was 10 mV s. -1 ; (3) Test results are as follows Figure 5 As shown, curve a is the CV curve of the electrode Nafion / BOD / CNT / Pt / CP under anaerobic conditions, curve b is the CV curve of the electrode Nafion / CNT / Pt / CP under air diffusion mode, curve c is the CV curve of the electrode Nafion / BOD / CNT / CP under air diffusion mode, and curve d is the CV curve of the electrode Nafion / BOD / CNT / Pt / CP under air diffusion mode.

[0044] In addition, current density tests were conducted on three biocathodes, with the current density being the CV current density value of 0.1 V vs. Ag / AgCl.

[0045] Table 1 Comparison of current densities of three biological cathodes

[0046] The above description of the embodiments is merely for the purpose of helping to understand the method and core idea of ​​the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0047] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the principles or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novelty disclosed herein.

Claims

1. A flexible air biocathode containing a superhydrophobic interface layer, characterized in that, The flexible air biocathode includes a flexible air diffusion substrate electrode; the air biocathode also includes an enzyme membrane modification layer on a hydrophobic porous matrix and a superhydrophobic interface layer located between the two, wherein the superhydrophobic interface layer is a superhydrophobic modified layer composed of metal particles or their alloys that have oxygen-reducing properties. The flexible air diffusion substrate electrode includes a pair of flexible protective films as the outer layer structure, a screen-printed circuit as the middle layer structure, a copper sheet, and a hydrophobic porous matrix. The pair of flexible protective films each contain hot melt adhesive and the sides containing the hot melt adhesive are opposite each other. The outer layer structure and the middle layer structure are formed into a sandwich structure by a hot pressing process.

2. The flexible air biocathode according to claim 1, characterized in that, The flexible protective film is selected from one of the following materials: TPU hot melt adhesive film, PES hot melt adhesive film, PA hot melt adhesive film, PO hot melt adhesive film, and EVA hot melt adhesive film with a thickness of 60~100 μm; the hot melt adhesive is one of the following: polyurethane hot melt adhesive, copolyester hot melt adhesive, polyamide hot melt adhesive, polyolefin hot melt adhesive, and vinyl acetate copolymer hot melt adhesive.

3. A flexible air biocathode according to any one of claims 1-2, characterized in that, The flexible protective film has open electrode holes and tab holes. The diameter of the electrode holes is 4 mm, the diameter of the tab holes is 3 mm, and the diameter of the copper sheet is 4 mm.

4. The flexible air biocathode according to claim 1, characterized in that, The hydrophobic porous matrix is ​​fixed on the screen-printed circuit around the electrode holes by a hot-pressing process. The hydrophobic porous matrix is ​​one of hydrophobic carbon paper, hydrophobic carbon cloth, and hydrophobic carbon felt.

5. The flexible air biocathode according to claim 1, characterized in that, The enzyme membrane modification layer includes a copper-containing oxidoreductase, an enzyme carrier material, and a membrane matrix. The copper-containing oxidoreductase includes bilirubin oxidase and laccase. The enzyme carrier material includes carbon nanotubes and graphene. The membrane matrix includes Nafion solution and chitosan solution.

6. A flexible air biocathode according to claim 5, characterized in that, The bilirubin oxidase was derived from Myrothecium verrucaria, EC 1.3.3.5, 27 U mg. -1 .

7. The flexible air biocathode according to claim 1, characterized in that, The metal particles or their alloys are Pt metal particles or Pt alloys.

8. A flexible air biocathode according to claim 7, characterized in that, The metal particles are Pt metal particles with a cactus-like morphology and a particle size of 100~800 nm. The water contact angle of the interface formed by the Pt metal particles is greater than 120°.

9. A method for preparing a flexible air biocathode as described in any one of claims 1-8, characterized in that, The preparation method includes: (1) Superhydrophobic modification of the hydrophobic porous matrix in the flexible air diffusion substrate electrode, the modification steps including: the prepared air diffusion substrate electrode in 10 g L -1 In a mixed solution of HPtCl6, H2O and 1 M H2SO4, with Ag / AgCl as the reference electrode and Pt as the auxiliary electrode, a superhydrophobic layer containing Pt particles with uniform structure and cactus-like morphology was formed on the surface of a hydrophobic porous matrix by electrodeposition. (2) Immobilization of the catalytic oxygen reductase membrane modified layer, the immobilization steps include: taking 5 mg mL -1 Carboxylated carbon nanotube suspension, 20 mg / mL -1 Add the bilirubin oxidase solution and 0.5 wt% Nafion dilution solution to a test tube and mix thoroughly to form a mixture; then, wet the surface of the air diffusion substrate electrode containing the superhydrophobic interface prepared in step (1) with ethanol solution, and then quickly take the mixture and coat it evenly on the surface of the Pt superhydrophobic layer, and air dry at room temperature.

10. The application of an air biocathode as described in any one of claims 1-8 in the catalytic reduction of oxygen.

11. A biofuel cell, the biofuel cell comprising a bioanode and an air biocathode as described in any one of claims 1-8, wherein the cell structure of the biofuel cell is arranged in an island-chain array.

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