Conductive hydrogel and its derivatives, carbon nanomaterial and enzyme bioelectrode and application thereof

Abstract

The present invention provides a conductive hydrogel and its derivatives, carbon nanomaterials, and enzyme bioelectrodes and their applications. The designed and synthesized conductive hydrogel and its derivatives can serve as electrolytes for flexible / rechargeable enzyme biofuel cells, ensuring ion conduction between the enzyme bioanode and enzyme biocathode while also serving as a fuel tank. Furthermore, the use of the hydrogel simplifies and facilitates the assembly of the biofuel cell, allowing the enzyme bioanode and enzyme biocathode to be directly pressed onto the sides of the hydrogel electrolyte plate, thereby eliminating the cumbersome battery assembly and packaging issues. The present invention uses a catalyst to activate asphalt to produce RADC and enzyme bioelectrodes prepared using RADC. The biofuel cell / capacitor hybrid biodevice assembled based on the conductive hydrogel electrolyte and enzyme bioelectrode outputs up to 0.64V OCP and 1.01μW·cm ‑2 It has the maximum power density and has high stability, excellent self-healing, ductility, adhesion, puncture resistance and plasticity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of conductive hydrogel, in particular to a conductive hydrogel and its derivative, a carbon nanomaterial and an enzyme bioelectrode prepared therefrom, and application of the conductive hydrogel and its derivative and the enzyme bioelectrode in a flexible biofuel cell / capacitor hybrid bio-device. BACKGROUND

[0002] Flexible and stretchable functional electronic products are attracting more and more attention due to their wearable, comfortable, remote operation and timely feedback characteristics. In order to provide perfect matching power for these flexible electronic devices, it is necessary to develop high-performance flexible or even stretchable energy conversion and storage devices. Electronic devices have high requirements for energy storage devices in use, which can adapt to various mechanical deformations (such as bending, compression, twisting, stretching, etc.), maintain continuous and stable power supply and safety. The development of the times puts forward higher requirements for the size, weight, safety, mechanical durability and electrochemical performance of energy storage devices.

[0003] Biofuel cells have good biocompatibility and are expected to be used as power sources for flexible and wearable bioelectronic devices. Generally, a biofuel cell is composed of an anode, a cathode, an electrolyte and a separator. Biofuel cells are a kind of green and environmentally friendly power generation devices, which generally use hydrogen, methanol and the like as fuel, and O2 as oxidant, and convert chemical energy into electrical energy through an electrochemical reaction pathway.

[0004] Enzyme biofuel cells (EBFCs) are a subclass of biofuel cells, which use enzymes to convert the chemical energy in fuels (such as glucose, lactose, fructose or alcohol) into electrical energy through fuel oxidation at the anode and molecular oxygen reduction at the cathode. Compared with traditional fuel cells, EBFCs have the following advantages: 1) they can work under mild conditions (room temperature, normal pressure, near neutral pH environment), which is conducive to simplifying the structural design of the battery to facilitate its practical application; 2) biological catalysts widely exist in animals, plants and microorganisms, and can be artificially extracted on a large scale, which has better cost advantage; 3) natural renewable sugars, alcohols and other biomasses can be used as fuel, which has a wide source and low price, and also meets the environmental protection requirements. EBFCs are expected to be used as implantable energy sources to power heart pacemakers and microsensors, or as wearable energy devices for sensing, drug controlled release and other fields.

[0005] How to smoothly run the flexible device is a challenge for researchers, and the stretchability of traditional liquid electrolyte is limited, which leads people to consider various flexible ion conductors, such as ionic liquids, electrolyte solutions and polymer hydrogel electrolytes, which can be regarded as similar charge conductors and have been used in flexible and stretchable devices.

[0006] Gel electrolytes, usually composed of liquid electrolytes (organic / inorganic salts dissolved in organic solvents / water) and different polymer matrices. A variety of polymers can be applied as matrices to hydrogel electrolytes. Common matrices of hydrogels are natural macromolecules (chitosan, sodium alginate) and synthetic macromolecules (polyacrylamide, polyacrylic acid, polyvinyl alcohol). Gel electrolytes not only retain the advantages of liquid electrolytes, providing sufficient ionic conductivity and ensuring close interfacial contact, but also inherit the relatively high mechanical properties of solid polymer electrolytes, exhibiting excellent flexibility, which can be applied to flexible electronic devices, portable and wearable electronic devices. The unique properties of hydrogels make them ideal candidates for soft electrolyte materials of flexible EBFCs. Polymer hydrogels are composed of hydrophilic polymer chains, with a tissue-like, viscoelastic, flexible cross-linked network that can maintain structural integrity under various mechanical deformations. The interior of the hydrogel electrode has a three-dimensional network with three-dimensional interconnections, a rich pore structure, a large active area for redox reactions, and provides sufficient electron transport paths.

[0007] However, traditional single conductive hydrogels cannot meet all the needs of people in some aspects of performance, and the lack of strength and toughness, the lack of function are the main obstacles to its application. By changing the conductive filler, dopant, cross-linking or hydration state, the electrochemical performance, network structure, mechanical properties and biological functions of the conductive hydrogel can be easily adjusted in a wide range. The current literature reports that the preparation of conductive hydrogel mainly introduces functional additives such as polydopamine, chitosan guar gum, tannic acid, carbon nanotubes into the conductive hydrogel system, and has developed a variety of conductive hydrogels with adhesion, self-repairing, antibacterial, sensing performance. However, the addition of functional additives often weakens the dynamic cross-linking interaction in the hydrogel network, resulting in a loss of mechanical strength.

[0008] Therefore, it is still a challenge to prepare multifunctional conductive hydrogels with reliable performance and good mechanical stability, and how to further improve the conductive performance and stretchable wearable performance of conductive hydrogels and other problems need to be solved. SUMMARY

[0009] In order to achieve the purpose of the application, the present application provides a conductive hydrogel and its derivatives, a carbon nanomaterial and an enzyme bioelectrode and a preparation method and application thereof. By preparing a conductive hydrogel and its derivatives with conductivity close to that of an ionic solution, using a catalyst to activate asphalt to obtain RADC, and using RADC to prepare an enzyme bioelectrode, and further preparing a flexible / chargeable enzyme biofuel cell using the conductive hydrogel and its derivatives and the enzyme bioelectrode, it paves the way for the development of glucose hydrogel hybrid devices for biochemical energy storage and conversion.

[0010] To achieve the above object, the technical scheme of the present application is as follows:

[0011] In one aspect, the present application provides a conductive hydrogel, which is prepared by using acrylamide as a monomer (AAM), N,N-methylene bisacrylamide as a crosslinking agent (MBA), carboxymethyl chitosan as a functional enhancer (CCTS), propylene glycol as a water-retaining agent, and ammonium persulfate (APS) as an initiator. The hydrogel prepared by the present application has good in-situ self-repairing properties, toughness and puncture resistance, and good adhesion and plasticity.

[0012] In one aspect, the present application provides a preparation method of the conductive hydrogel, and the specific steps are as follows:

[0013] S1: preparing an acrylamide aqueous solution, adding N,N-methylene bisacrylamide, carboxymethyl chitosan and propylene glycol to stir to obtain a mixed solution;

[0014] S2: adding ammonium persulfate to the mixed solution obtained in S1, stirring and then transferring to a mold, heating and reacting in an oven to obtain the conductive hydrogel.

[0015] Further, in the acrylamide aqueous solution, the mass ratio of acrylamide to deionized water is 1:3-3:1, specifically 1:1, 1:2, 1:3, 3:1, 2:1, etc.

[0016] Further, the mass ratio of N,N-methylene bisacrylamide, carboxymethyl chitosan and propylene glycol is 4:1:1-4:1:4, specifically 4:1:1, 4:1:2, 4:1:3, etc. Preferably, the S1 reaction is carried out in ordinary glassware.

[0017] Further, in S2, the reaction is heated in an oven at 55℃ for 8h until the polymerization is completed. Ammonium persulfate is a polymerization initiator.

[0018] In one aspect, the present application provides a preparation method of the conductive hydrogel derivative, which is prepared by immersing the conductive hydrogel obtained in the present application in a glucose phosphate buffer solution to obtain a glucose-conductive hydrogel, which is named PAAM-G.

[0019] Further, the glucose phosphate buffer solution refers to a phosphate buffer solution containing 0.2M glucose.

[0020] In one aspect, the present application provides an application of the conductive hydrogel and its derivative in a flexible biofuel cell / capacitor hybrid bio-device.

[0021] Further, the conductive hydrogel and derivatives thereof can be used to prepare a flexible electrolyte in a biofuel cell / capacitor hybrid bio-device, preferably, a flexible electrolyte in a glucose / oxygen biofuel cell / capacitor hybrid bio-device.

[0022] Further, the biofuel cell / capacitor hybrid bio-device can further be an enzymatic biofuel cell / capacitor hybrid bio-device, in particular, a glucose / oxygen biofuel cell / capacitor hybrid bio-device.

[0023] The conductive hydrogel and derivatives thereof prepared by the present application as a flexible electrolyte has an electrical conductivity close to that of an ionic solution, which paves the way for the development of a glucose hydrogel hybrid device for bio-chemical energy storage and conversion.

[0024] In one aspect, the present application provides a carbon nanomaterial, wherein the C1s spectrum of the carbon nanomaterial has characteristic signal peaks at 284.6, 285.3, 286.6 and 288.8 eV.

[0025] Further, the C1s spectrum of the carbon nanomaterial is as shown in Figure 5 .

[0026] In one aspect, the present application provides a method for preparing a carbon nanomaterial, and the specific preparation process is as follows:

[0027] After mixing the ground asphalt particles with the catalyst K3[Fe(CN)6], stirring is performed to evaporate the solvent, and a mixed material is obtained;

[0028] The mixed material is gradually heated to carbonize under a nitrogen atmosphere;

[0029] After carbonization, the material is refluxed and condensed, then soaked in acid for activation, and finally washed, vacuum dried, and prepared.

[0030] Further, the mass ratio of the asphalt particles to potassium ferricyanide is selected from 1:0, 1:1, 1:2 or 1:3.

[0031] In one aspect, the present application provides an enzyme bioelectrode, which comprises a substrate electrode, a carbon material layer and an enzyme layer, and the carbon material layer contains a carbon nanomaterial.

[0032] Further, in the carbon material layer, the content of the carbon nanomaterial is 5.92-11.84 mg·cm -2 .

[0033] Further, the substrate electrode can be a glassy carbon electrode (GCE), a nickel foam, carbon paper, carbon cloth or carbon felt.

[0034] Further, the enzyme in the enzyme layer is a biological enzyme, which can be glucose oxidase or bilirubin oxidase (BOD), etc., and is preferably glucose oxidase (GOx) in the present application. Preferably, when the enzyme layer is glucose oxidase (GOx), the electrode can serve as an anode in an enzyme biological fuel cell electrode; when the enzyme layer is bilirubin oxidase (BOD), the electrode can serve as a cathode in an enzyme biological fuel cell electrode.

[0035] Further, the enzyme layer further comprises a Nafion coating layer coated on the surface of the enzyme layer. Further, the Nafion coating layer is formed by dropping a Nafion solution on the surface of the enzyme layer and drying to form a coating layer.

[0036] In another aspect, the present application provides an enzyme biological fuel cell / capacitor hybrid biological device, which comprises the conductive hydrogel prepared by the present application as a flexible electrolyte. Further, it further comprises the electrode prepared by the present application. Further, the electrode comprises an anode and a cathode, which can be directly pressed on both sides of the flexible electrolyte.

[0037] In one aspect, the present application provides the use of the enzyme biological electrode of the present application in a flexible biological fuel cell / capacitor hybrid biological device.

[0038] Further, the enzyme biological electrode can be used to prepare an anode and / or a cathode in a biological fuel cell / capacitor hybrid biological device based on different enzyme layers, and preferably can be used to prepare an anode and / or a cathode in a glucose / oxygen biological fuel cell / capacitor hybrid biological device.

[0039] Further, the biological fuel cell / capacitor hybrid biological device can further be an enzymatic biological fuel cell / capacitor hybrid biological device, and specifically can be a glucose / oxygen biological fuel cell / capacitor hybrid biological device.

[0040] The present application develops a convenient strategy for preparing conductive hydrogel and its derivatives (flexible sheets) and electrodes (enzyme biological electrodes). The conductive hydrogel and its derivatives PAAM-G designed and synthesized by the present application can be used as electrolytes of flexible / chargeable enzyme biological fuel cells. The conductive hydrogel and its derivatives can not only ensure the ion conduction between the enzyme biological anode and the enzyme biological cathode, but also can serve as a fuel tank. The use of the conductive hydrogel makes the assembly of the biological fuel cell simple and easy, and the enzyme biological anode and the enzyme biological cathode can be directly pressed on both sides of the conductive hydrogel electrolyte plate, thereby solving the cumbersome problem of battery assembly and packaging. The results show that this new type of flexible biological fuel cell / capacitor hybrid biological device based on the electrolyte of the conductive hydrogel and its derivatives can output an OCP as high as 0.64 V and a 1.01 μW·cm -2The maximum power density is 1.01 mW·cm-2, and the flexible enzyme biofuel cell has high stability, excellent self-healing, ductility, adhesion, puncture resistance, plasticity, which is mainly due to the use of conductive hydrogel and enzyme bioelectrode.

[0041] The synthetic conductive hydrogel and its derivative PAAM-G can be used as the electrolyte of the flexible / chargeable enzyme biofuel cell, which can ensure the ion conduction between the enzyme bioanode and the enzyme biocathode, and can also be used as a fuel tank.

[0042] The carbon nanomaterial prepared by the method has excellent conductivity and rich active sites, and has a large number of pores, which is beneficial to the filling of the flexible electrolyte and the diffusion of the substrate and ions.

[0043] The biofuel cell / capacitor hybrid biological device assembled based on the conductive hydrogel electrolyte and the enzyme bioelectrode can output an OCP of up to 0.64V and a maximum power density of 1.01 mW·cm -2 The flexible enzyme biofuel cell has high stability, excellent self-healing, ductility, adhesion, puncture resistance, plasticity.

[0044] The conductive hydrogel and its derivative developed by the application have excellent flexibility, electrochemical performance, mechanical performance, water retention and biocompatibility, and the flexible electrolyte can improve the stability of the enzyme, solve the problems of easy deactivation and dissolution leakage of the enzyme catalyst on the electrode surface, and enhance the stability of the EBFCs, thereby improving the performance of the EBFCs. The preparation process conditions (monomer type, monomer / crosslinking agent ratio, polymerization temperature, polymerization time, etc.) of the hydrogel and its derivative are studied. The results show that the glucose / O2 EBFCs equipped with the conductive hydrogel flexible electrolyte can output an OCP of up to 0.64V and a maximum power density of 1.01 mW·cm -2 The flexible enzyme biofuel cell has high stability, excellent self-healing, ductility, adhesion, puncture resistance, plasticity. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 (a) is a schematic diagram of RADC / Enzyme composite bioelectrode.

[0046] Figure 1 (b) is a schematic diagram of the principle of flexible EBFCs.

[0047] Figure 1 (c) is a schematic diagram of the regeneration process of EBFCs.

[0048] Figure 2 is the CV curve of RADC sample.

[0049] Figure 3 is the XRD pattern of RADC.

[0050] Figure 4 is the Raman spectrum of RADC.

[0051] Figure 5 is the C1s XPS fitting result of RADC.

[0052] Figure 6 (a) is the N2adsorption-desorption isotherm of ADC nanoparticles.

[0053] Figure 6 (b) is the pore size distribution of RADC nanoparticles.

[0054] Figure 7 is the SEM (a, b) and HR-TEM (c, d) images of RADC.

[0055] Figure 8 is the electrochemical performance test of bioelectrode.

[0056] Figure 9 is the physical performance test of hydrogel, (a) the photo of hydrogel self-healing process. (b) the puncture resistance of hydrogel. (c) the combination of hydrogel with human wrist, (d-g) the adhesive shows that the hydrogel is adhered to different materials. (h-k) the hydrogel is shaped into various shapes.

[0057] Figure 10 is the CV curve of (left) RADC / GCE in 0.2 M glucose solution (pH 7.0 curve a) and PAAM-G (curve b), the scan rate is 10 mV·s -1 . (right) the CV test curve of modified RADC / GCE in 0.2 M glucose solution (curve a) and PAAM-G (curve b), respectively.

[0058] Figure 11CV curves of (left) RADC-TTF / GOx / GA in 0.2 M glucose solution (pH 7.0 curve a) and PAAM-G (curve b) with a scan rate of 10 mV-s -1 (right) ORR of modified RADC-ABTS / BOD / GA in 0.2 M glucose solution (curve a) and PAAM-G (curve b).

[0059] Figure 12 EIS plots of GCE, RADC / GEC and the cell.

[0060] Figure 13 E-t plots of (left) hybrid bioelectrochemical devices collected at 1 mA-cm -2 , measured in PAAM-G (0.2 M glucose) and PAAM (0.5 M PBS, pH 7.0) saturated with air. (Right) Chronopotentiometric (CP) test plots of EBFCs at different current densities with PAAM-G as electrolyte.

[0061] Figure 14 Charge-discharge curves of RADC-TTF / GOx / GA and RADC-ABTS / BOD / GA electrodes in the presence of 2 mM glucose in air-saturated buffer solution. Discharge was performed by applying a 0.5 mA-cm -2 pulse current for 1 s.

[0062] Figure 15 Charge-discharge curves of (left) PAAM-G assembled EBFCs. Voltage drop was measured by applying different current pulses: (A) 10 mA-cm -2 , (B) 12 mA-cm -2 , (C) 14 mA-cm -2 , (D) 16 mA-cm -2 , (E) 18 mA-cm -2 and (F) 20 mA-cm -2 , for 1 s. (Right) Power-current distribution plot in pulse mode from the end-point voltage values obtained by applying various current pulses.

[0063] Figure 16 Polarization and power output plots of (left) glucose / O2 EBFCs assembled with RADC and PAAM-G obtained at 1.0 mV-s -1 . (Right) Long-term charge-discharge cycling test of the hybrid device assembled with PAAM-G with a current pulse of 0.5 mA-cm -2 and a discharge time of 1 s.

[0064] Figure 17The glucose / O2 EBFCs assembled under the conditions were tested for polarization and power output curves at 0.5 mA·cm-2applied current pulse with 1 s discharging time. (Right) Hybrid power device long-term charge-discharge cycling test at 0.5 mA·cm-2applied current pulse with 1 s discharging time. -1 The polarization and power output curves of glucose / O2 EBFCs assembled under the conditions were tested. (Right) Hybrid power device long-term charge-discharge cycling test at 0.5 mA·cm-2applied current pulse with 1 s discharging time. -2 The polarization and power output curves of glucose / O2 EBFCs assembled under the conditions were tested. (Right) Hybrid power device long-term charge-discharge cycling test at 0.5 mA·cm-2applied current pulse with 1 s discharging time.

[0065] The application will be further described below in connection with specific embodiments. These embodiments are only used to illustrate the application and not to limit the scope of the application. DETAILED DESCRIPTION

[0066] The application will be further described below in connection with specific embodiments. These embodiments are only used to illustrate the application and not to limit the scope of the application.

[0067] Example 1 Preparation and physical property test of conductive hydrogel electrolyte

[0068] 1. Preparation of conductive hydrogel:

[0069] The conductive hydrogel was prepared by one-pot method.

[0070] Firstly, acrylamide monomer (AAM, 1.422 g) was added to deionized water in a weight ratio of 1:1 and magnetically stirred for 30 min for dissolution;

[0071] Then, N,N-methylene benzene acrylamide (MBA, 0.001 g), carboxymethyl chitosan and propylene glycol were added to the above mixed solution in a weight ratio of 4:1:2 and stirred uniformly;

[0072] Finally, initiator ammonium persulfate (APS, 0.257 g) was added, transferred to a mold, and finally heated in an oven (55°C) for 8 h to form a conductive hydrogel (named PAAM) through free radical polymerization,

[0073] The above-synthesized flexible conductive hydrogel was soaked in 5 mL of phosphate buffer solution (PBS, pH = 7.0) containing 0.2 M glucose, and the glucose was allowed to penetrate to obtain a glucose-conductive hydrogel, named PAAM-G.

[0074] 2. Physical property test of conductive hydrogel:

[0075] Take 50 mg of fresh conductive hydrogel sample, cut it into two parts using a knife, and then tightly contact the two cut surfaces together. Observe the in-situ self-repairing after a period of time.

[0076] The in-situ self-repairing property of the conductive hydrogel was studied by the method of shearing / healing.

[0077] Results are shown in Figure 9 a. A whole piece of conductive hydrogel was cut into two pieces, and then the surfaces of the two pieces of conductive hydrogel were contacted with each other. After 10 s, the conductive hydrogel automatically healed. When the healed conductive hydrogel was lifted with a pair of tweezers, it could bear its own weight without falling off. Considering that the conductive hydrogel needs to have a certain toughness as an electrolyte, we also studied the puncture resistance of the conductive hydrogel Figure 9 b). In addition, we also studied the adhesion of the conductive hydrogel. The conductive hydrogel could adhere to the surface of fresh biological tissues, and the results are shown in Figure 9 c. The conductive hydrogel could adhere to the surface of human tissues. Similarly, the conductive hydrogel could firmly adhere to the surface of non-biological tissues and could bear a certain degree of stretching without falling off Figure 9 d-g). Finally, the plasticity of the conductive hydrogel was studied Figure 9 h-k). The conductive hydrogel could maintain various shape patterns.

[0078] Example 2 Preparation and performance characterization of carbon nanomaterials (RADC)

[0079] 1. Preparation

[0080] The ground asphalt particles and the catalyst K3[Fe(CN)6] were mixed in a mass ratio of 1:2 in 20 mL of deionized water, stirred for 8 h, and the solvent was evaporated to obtain a mixed material;

[0081] Gradually heated (2 ℃ min -1 ) to the target temperature of 1200 ℃ in a nitrogen atmosphere, so that the mixed material was carbonized;

[0082] The crude sample of the carbonized material was refluxed and condensed in 20 mL of deionized water, soaked in 2M sulfuric acid solution and 3M nitric acid solution at 75 ℃ for 12 h, and washed with 20 mL of distilled water for 3 times.

[0083] Finally, the washed material was vacuum dried at 65 ℃ for 24 h to obtain the prepared RADC.

[0084] 2. Characterization of carbon nanomaterial RADC

[0085] The cyclic voltammetry (CV) was used to study the micro-reaction process on the electrode to verify the catalytic performance of the prepared active material. An equilateral triangular pulse voltage was applied to the working electrode. As shown in Figure 2 , due to the [Fe(CN)6] 3- / 4-The redox reaction has good reversibility, and redox waves are detected at each electrode with excellent level symmetry. The reaction rate on the electrode is closely related to the electrode potential, and the reaction current density is closely related to the reaction rate. It is clear that the current density (0.64 mA·cm -2 ) detected on the bare GCE (curve a) is the smallest among all electrodes, indicating that the modification of RADC promotes the Faraday reaction on the electrode surface. It is worth noting that the peak current value of the potassium ferricyanide activated catalytic RADC (curve d) is greater than that of the RADC prepared by direct high-temperature annealing with asphalt as the precursor (curve b), indicating that the potassium ferricyanide successfully modified the ADC material. The peak current of curve c is the highest, reaching 1.66 mA·cm -2 , indicating that the prepared RADC has excellent electrical conductivity and abundant active sites.

[0086] The material composition and internal atomic structure of the prepared RADC sample were further studied by X-ray diffraction (XRD). As Figure 3 shown in the XRD pattern, the diffraction peak signals with different diffraction intensities are shown on the (002) and (101) carbon surfaces, and a sharp peak is observed in the XRD pattern of RADC, indicating the presence of graphitized carbon. Compared with the original ADC (curve a), the diffraction peak position of the (002) RADC (curve b) is lower, indicating that the distance between the crystal layers increases after the potassium ferricyanide excitation, and the wide and low diffraction peak of the (002) RADC appears because its structure is amorphous, unlike the long-range order of carbon atom arrangement in standard crystals, only short-range order in several atoms.

[0087] Raman spectroscopy Figure 4 shows that two characteristic peaks of ADC (curve a) appear at 1342 cm -1 and 1586 cm -1 , respectively, responding to the degree of disorder of the crystal structure of the D band and the in-plane stretching vibration mode of the G band. After high-potassium ferrate catalysis, the intensity ratio (I D / I G ) of ADC (curve a) and RADC (curve b) representing disordered graphite increases from 1.04 to 1.27, indicating that the goal of introducing defects and active sites in the matrix carbon is achieved. In order to study the bonding characteristics and chemical composition of the RADC (curve b) and the original ADC (curve a) material, X-ray photoelectron spectroscopy (XPS) measurement spectrum test was carried out.

[0088] Figure 5 is the C1s spectrum, and the four signal peaks at 284.6, 285.3, 286.6 and 288.8 eV correspond to sp 2 carbon, sp 3carbon, C=C and O-C-O. This is strong evidence for the successful preparation of RADCs, whose sp 2 Carbon content is higher than that of the original ADC.

[0089] The textural properties of the two materials were compared by nitrogen adsorption-desorption isotherms and pore size distribution curves. Nitrogen adsorption-desorption isotherms and pore size distribution curves are shown in Figure 6 The ADC curve (curve a) shows a clear classical Type I, indicating that the microporous structure is dominant. The RADC curve (curve b) shows a Type IV curve in the window from 0.42 to 1.0 of P / P0, characterized by a H3-type hysteresis loop, showing a rich meso-macroporous loose pore structure. The BET specific surface area increased from 15 m 2 g -1 to 162.73 m 2 g -1 ; the pore volume increased from 0.02 cm 3 g -1 to 0.16 cm 3 g -1 . This phenomenon indicates that RADC forms a large number of pores. The average residual pore size was calculated to be 10.05 nm Figure 6 b, which may be due to the internal excitation of potassium ferricyanide.

[0090] In order to further study the formation of RADC, the morphological changes were observed by electron microscopy. Figure 7 a The structure of RADC with typical three-dimensional porous structure was detected, showing interconnected channels. The Figure 7 b detected by high-resolution transmission electron microscopy (HRTEM) shows that the rough surface of RADC has pores and open characteristics. Figure 7 c further proves the connectivity of each pore grown in RADC, as well as the open three-dimensional framework composed of disordered connection of single carbon atoms and multi-carbon layer stacking. This may be due to the highly developed porous structure produced during the chemical activation process, which is beneficial to the filling of flexible electrolyte and the diffusion of substrates and ions. It can be seen from Figure 7 d that due to the activation catalysis effect of potassium ferricyanide, the interlayer thickness (0.41 nm) corresponding to the (002) face of RADC is larger than that of graphite (0.36 nm).

[0091] Example 3 Preparation of enzyme-based bioelectrode and electrochemical measurement

[0092] 1. Preparation of enzyme bioelectrode: The enzyme bioelectrode is a glassy carbon electrode (GCE, diameter 3 mm) modified with enzyme / bitumen-derived carbon material RADC.

[0093] A simple drop-casting method was used to manufacture the working electrode.

[0094] Before modification, the GCE was polished with alumina slurry (0.3 μm and 0.03 μm) on a polishing cloth and then ultrasonicated in double-distilled water and ethanol for 15 s sequentially and then dried at room temperature.

[0095] Preparation of bioanode: 10 μL of pitch-derived carbon material RADC suspension (10 mg mL -1 , dispersed in N,N-dimethylformamide) and 2μL tetrathiafulvalene (TTF) mediator solution (0.02M, solvent is acetonitrile) were mixed and 2μL was cast on the surface of the pretreated GCE and dried in air. Then, 5μL GOx solution was cast on the surface of the GCE modified with pitch-derived carbon material RADC, and the electrode was stored in a refrigerator at 4°C for 4h. Finally, 3μL Nafion solution (5‰) was dropped on the surface of the GCE modified with GOx / pitch-derived carbon material RADC, and the electrode was stored in a refrigerator at 4°C for 2h to obtain a bioanode (denoted as RADC / TTF / GOx or RADC-TTF / GOx / GA).

[0096] Preparation of biocathode: 10 μL of pitch-derived carbon material RADC suspension (10 mg mL -1 , dispersed in N,N-dimethylformamide) and 2μL of 2,2'-azidobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) mediator solution (0.02M, solvent is water) were mixed and 2μL was cast on the surface of the pretreated GCE and dried in air. Then, 5μL of BOD solution was cast on the surface of the GCE modified with pitch-derived carbon material RADC, and the electrode was stored in a refrigerator at 4°C for 4h. Finally, 3μL of Nafion solution (5‰) was dropped on the surface of the GCE modified with BOD / pitch-derived carbon material RADC, and the electrode was stored in a refrigerator at 4°C for 2h to obtain a biocathode (denoted as RADC / ABTS / BOD or RADC-ABTS / BOD / GA).

[0097] 2. Preparation of comparative electrode

[0098] For control experiments, RADC / GOx, RADC / BOD, RADC / GCE, Nafion / GOx / ADC / carbon paper, and Nafion / BOD / RADC / carbon paper were prepared in a similar manner to the preparation of enzyme bioelectrodes.

[0099] Example 4 Electrochemical Measurement of Enzyme Bioelectrode

[0100] 1. Electrochemical measurement of working electrode:

[0101] Electrochemical experiments were performed on a CHI 660E electrochemical workstation in a three-electrode system, in which GOx / BOD / RADC / GCE (RADC / ABTS / BOD and RADC / TTF / GOx, respectively) was used as the working electrode, Ag / AgCl in 3 M KCl was used as the reference electrode, and Pt foil (1 cm 2 ) was used as the counter electrode. N2-saturated 0.5 M PBS (pH 7.0) was used as the supporting electrolyte. Electrochemical impedance spectroscopy (EIS) data were obtained using a 0.1 M KCl solution containing 5 mM [Fe(CN)6] 3- / 4- , at a frequency of 0.01 Hz to 100 kHz, and an AC applied potential of 1 mV, with bare GCE and BOD / Asphalt-derived carbon material RADC-modified GCE as the working electrode. Linear sweep voltammetry (LSV) experiments were performed in N2-saturated 0.5 M PBS (pH 7.0) containing different concentrations of glucose, at a scan rate of 10 mV·s -1 . All tests were performed at room temperature.

[0102] 2. Electrochemical performance test:

[0103] ① The electrochemical performance of single anode and cathode on PAAM flexible electrolyte (PBS, pH = 7.0) was detected by three-electrode system Figure 8 (a). The peak signal of RADC-TTF / GOx / GA anode was captured at 0.31 V on the polarization curve Figure 8 (b). Subsequently, the RADC-TTF / GOx / GA bioanode showed a rapid current response Figure 8 (c), and glucose oxidation was accompanied by the injection of glucose solution into the flexible electrolyte PAAM, and the current increased sharply.

[0104] Another method was to seal the device with N2 for 30 min, and the signal of the reduction of substances in RADC-ABTS / BOD / GA cathode was detected at 0.45 V Figure 8 (d). Secondly, O2 was introduced into the flexible electrolyte PAAM, and the RADC-ABTS / BOD / GA bio-cathode showed a significant current response, indicating that O2 was successfully reduced Figure 8 (e). The bioelectrocatalytic reactions of glucose oxidation and oxygen reduction on the bioanode and bio-cathode, respectively, successfully indicated that the enzyme biofuel cell (EBFCs) established by the potential difference between the positive and negative electrodes was thermodynamically favorable.

[0105] As a comparison, RADC had limited electrochemical catalytic activity for glucose oxidation and oxygen reduction without enzyme loading. CV was recorded on the flexible electrolyte PAAM-G (pH = 7.0), as Figure 10As shown in Figure 3, the CV curve of the RADC / GCE electrode is rectangular without a clear peak signal, reflecting the typical capacitive behavior of RADC, which indicates that RADC acts as an electron transfer carrier in the bioelectrochemical process.

[0106] In order to clarify the principle of energy generation and conversion in the system, the catalytic ability of the anode or cathode is detected. Figure 11 As shown in a, in PAAM-G electrolyte (pH = 7.0), at 10 mV·s -1 At the scan rate, the potential windows at the anode and cathode were -0.1-0.4 and 0.1-0.7 V, respectively. While an oxidation peak in PBS originates from the oxidation of TTF, an S-shaped response was observed for RADC-TTF / GOx / GA in the presence of 0.2 M glucose, which was attributed to glucose-catalyzed oxidation. This study investigated the glucose oxidation process, demonstrating the effective immobilization of glucose oxidase at the anode and its successful catalytic oxidation of glucose to gluconic acid.

[0107] The oxygen reduction reaction of the RADC-ABTS / BOD / GA catalyst layer was also studied. Figure 8 b shows the characteristic peak of the RADC-ABTS / BOD / GA biocathode in N2-saturated PAAM is from the reduction of ABTS. However, when O2 flow is passed through the device, the cathode current increases sharply until it reaches a maximum point at 0.38V on the RADC-ABTS / BOD / GA biocathode ( Figure 11 a). This peak is attributed to the reduction of oxygen. As the electrolyte changes phase, the current density decreases, e.g. Figure 11 As shown in ab, this may be due to the fact that the solid flexible hydrogel replaces the traditional electrolyte and the limited channels slow down the diffusion of the substrate.

[0108] In order to study the surface charge behavior of the electrode, EIS measurements were performed. The Nyquist plot is shown in the figure below. Figure 12 As shown, (where Z' represents the real part of the impedance and Z" is the imaginary part of the impedance). The half arc of the bare glassy carbon electrode at high frequencies indicates that its charge transfer resistance (Rct) is high, while the GCE curve after RADC modification is a sloping line, indicating that the electrode interface resistance is reduced due to the modification of the RADC conductive material. A quarter arc can be observed in the battery test, which explains the obvious reason why ordinary biological enzyme proteins have the characteristic of resisting large charge transfer. The slope of the conductivity curve of Cell (PAAM-G) is slightly smaller than that of Cell (glucose solution), which confirms that the synthesized hydrogel electrolyte is already very close to the conductivity between ionic solutions.

[0109] Example 5 Design and evaluation of flexible glucose / oxygen enzyme biofuel cells (EBFCs)

[0110] Glucose / O₂ EBFCs are assembled using Nafion / GOx / ADC / carbon paper as the bioanode and Nafion / BOD / RADC / carbon paper as the biocathode, pressed onto either side of a hydrogel sheet. Conductive adhesive is applied behind the anode and cathode carbon papers to allow a nickel conductive sheet to conduct current. A foam mesh is layered behind the cathode carbon paper as a gas diffusion layer. The anode and cathode are then secured with a glass slide and dovetail clips. Finally, the anode and cathode are clamped to the nickel sheet with wires, forming a series circuit.

[0111] In order to investigate the energy conversion characteristics and power supply capacity of the hydrogel-based hybrid device, CP was used to conduct 1 mA cm -2 Discharge at a current density of .

[0112] First, a comparative experimental study was conducted on the electrolyte conditions of PAAM and PAAM-G. Figure 13 As shown, the front discharge time (red curve) is 5691s, with a time premium of up to 183.58 times, which is longer than the rear discharge time (31s) (black curve). This capacitive behavior is attributed to the synergistic process of biocatalysis and self-charging of the catalytic layer on the electrode surface in the presence of glucose, so the former (red curve) can extend the discharge time. At the same time, the latter (black line) clearly showed a sharp drop in voltage, which may be because the catalyst did not play a catalytic role and the device generated almost no electricity, so it discharged quickly during operation. Subsequently, in order to verify the charge storage characteristics of the hybrid device, the capacitance under different current densities was analyzed, and the comparison figure is shown in the figure below. Figure 13 As shown. At 2mA·cm -2 At a current density of 3 mA·cm, it took 503 s for the detected specific capacitance to drop to zero. -2 When the current density is low, the potential drops rapidly to 0V. The test results show that the hybrid system can obtain a higher capacitance value when discharged at a low current density.

[0113] The bioelectrochemical catalytic performance and enzyme stability of the hybrid device were evaluated at a certain current using pulse discharge cycles. Figure 14 The researchers show 100 charge-discharge cycles of the bioelectrode and calculate the corresponding OCV (the difference between the OCPs of the bioanode and biocathode) for a biosupercapacitor assembled from a RADC-TTF / GOx / GA bioanode and a RADC-ABTS / BOD / GA biocathode. This demonstrates the excellent self-charging performance of both bioelectrodes. Notably, after each voltage drop, the hybrid system returns to its pre-pulse voltage value due to continued and efficient energy conversion by the enzyme in the presence of an ample supply of glucose and oxygen. The system's stability over multiple charge-discharge cycles likely relies on the enzyme's assistance in effectively adsorbing and biodegrading the substrate during operation of the self-charging device.

[0114] As Figure 15 shown, in 600 seconds of time, the pulse applied for one second of the capacitive voltage was detected at different current densities, ranging from 10 mA cm -2 to 20 mA cm -2 . Interestingly, the application of a current pulse, a significant voltage drop occurs, the strength of which depends on the applied current. The system quickly recovers to a certain voltage after each pulse, and then gradually recovers to the initial voltage value of the smooth, indicating that the device has excellent stability in the process of multiple charge and discharge. The open-circuit voltage (OCV) of the assembled flexible PAAM-G EBFCs remained essentially unchanged (0.64 ± 0.07 V) under pulse mode.

[0115] In addition, the typical power output and polarization curve of PAAM-G hydrogel type EBFCs are shown in Figure 16 , the maximum power density output of the EBFCs is 1.01 mW cm -2 at 0.24 V, and the short-circuit current density is 3.74 mA cm -2 . Then we evaluated the output performance of EBFCs in 0.2 M glucose solution in Figure 17 , the OCV value is 0.70 V higher than that of flexible EBFCs (0.64 V). The j max is 4.62 mA cm -2 , P max is 1.14 mW cm -2 , it can be seen that the electrolyte changes from aqueous solution to hydrogel, and the battery voltage and power do not decrease too much. The long-term stability test cycle of the system is 100 times, the amperage is 0.5 mA cm -2 , and each pulse is applied for 1 s. A piece of flexible PAAM-G electrolyte is clamped between the two air diffusion electrodes. Before the voltage drops, in the subsequent experiments, 60 min of charge balance is maintained between the charge and discharge cycles and the substrate diffusion. The change process of each pulse voltage is monitored, and after each discharge for 600 s, the bioelectrochemical catalytic mixed system can actively recover to a stable voltage value of 0.64 V. The self-charging of RADC depends on the energy conversion of biological protein catalysis, and the slight rise of the initial voltage is likely due to the continuous diffusion of TTF / ABTS on the RADC modified electrode. This leads to the release of part of the stored energy when the study begins until equilibrium is reached. More importantly, long-term immersion in glucose solution can cause the enzyme coverage of the enzyme electrode to decrease, thereby affecting the number of generated electrons, affecting the stability of the bioelectrode and the ion diffusion efficiency, and ultimately leading to low and unstable voltage. The hydrogel-based EBFCs have excellent pulse charge and discharge stability.

[0116] In summary, we pioneered the preparation of RADC-TTF / GOx / GA and RADC-ABTS / BOD / GA electrodes, and developed a self-charging biological system integrating supercapacitors and biofuel cells. In addition, it showed good performance when equipped with liquid electrolyte and gel electrolyte, and the output power density was 1.14 mW·cm -2 and 1.01 mW·cm -2 respectively. Based on electrostatic interaction and chemical crosslinking, the flexible hydrogel has excellent self-healing, ductility, adhesion, puncture resistance, plasticity and conductivity. Compared with ordinary hybrid devices, the developed hybrid gel device shows excellent biosensing properties and stable operation (after 16.67 h of continuous operation in pulse mode, the current density remains at 98% of the initial current density). The research results not only open up a new way for the efficient use of waste asphalt, but also pave the way for the development of glucose hydrogel hybrid devices for biochemical energy storage and conversion.

[0117] The above merely provides the preferred but non-limiting embodiments of the present application, and the protection scope of the present application is not limited thereto. Any person skilled in the art, according to the technical solution and inventive concept of the present application, can make equivalent replacements or changes within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for preparing a derivative of a conductive hydrogel, characterized in that: The specific steps are as follows: S1: preparing an acrylamide aqueous solution, adding N,N-methylenebisacrylamide, carboxylated chitosan and propylene glycol and stirring to obtain a mixed solution; S2: adding ammonium persulfate to the mixed solution obtained in S1, stirring, transferring the mixture into a mold, and heating the mold in an oven to react to obtain a conductive hydrogel; S3: preparing a glucose-conductive hydrogel by immersing the conductive hydrogel in a glucose phosphate buffer solution.

2. The preparation method according to claim 1, characterized in that In the acrylamide aqueous solution, the mass ratio of acrylamide to deionized water is 1:3-3:1; The mass ratio of the N,N-methylenebisacrylamide, carboxylated chitosan and propylene glycol is 4:1:1-4:1:

4.

3. The preparation method according to claim 1, characterized in that In S2, the reaction was heated in an oven at 55°C for 8 h until the polymerization was complete.

4. An enzyme biofuel cell / capacitor hybrid biodevice, characterized in that: The flexible electrolyte comprises a derivative of the conductive hydrogel prepared by the method of claim 1.

5. The enzyme biofuel cell / capacitor hybrid biodevice according to claim 4, characterized in that: Also included are enzyme bioelectrodes.

6. The enzyme biofuel cell / capacitor hybrid biodevice according to claim 5, characterized in that: The enzyme bioelectrode includes an anode and a cathode, both of which can be directly pressed on both sides of the flexible electrolyte.

7. The enzyme biofuel cell / capacitor hybrid biodevice according to claim 5, characterized in that: The enzyme bioelectrode comprises a base electrode, a carbon material layer and an enzyme layer.

8. The enzyme biofuel cell / capacitor hybrid biodevice according to claim 7, characterized in that: The carbon material layer contains carbon nanomaterials.

9. The enzyme biofuel cell / capacitor hybrid biodevice according to claim 8, characterized in that: The carbon nanomaterial C 1 s The spectrum has characteristic signal peaks at 284.6, 285.3, 286.6 and 288.8 eV.

10. The enzyme biofuel cell / capacitor hybrid biodevice according to claim 8, characterized in that: The content of carbon nanomaterial in the carbon material layer is 5.92-11.84 mg·cm -2 .

11. The enzyme biofuel cell / capacitor hybrid biodevice according to claim 7, characterized in that: The base electrode is selected from glassy carbon electrode, nickel foam, carbon paper, carbon cloth or carbon felt.

12. The enzyme biofuel cell / capacitor hybrid biodevice according to claim 7, characterized in that: The enzyme in the enzyme layer is selected from glucose oxidase or bilirubin oxidase.

13. The enzyme biofuel cell / capacitor hybrid biodevice according to claim 12, characterized in that: The enzyme layer further includes a Nafion coating coated on the surface of the enzyme layer.

14. The enzyme biofuel cell / capacitor hybrid biodevice according to claim 12, characterized in that: When the enzyme layer is glucose oxidase, the electrode serves as an anode in an enzyme biofuel cell electrode; When the enzyme layer is bilirubin oxidase, the electrode serves as a cathode in an enzyme biofuel cell electrode.

15. Use of a derivative of the conductive hydrogel prepared by the method of claim 1 in a flexible biofuel cell / capacitor hybrid biodevice.

16. The use according to claim 15, characterized in that The flexible biofuel cell / capacitor hybrid biodevice is used to prepare a glucose / oxygen biofuel cell / capacitor hybrid biodevice.

Images