CN109732918B - Three-dimensional microbial electrode for 3D printing of gradient porous graphene oxide and preparation method thereof - Google Patents

Three-dimensional microbial electrode for 3D printing of gradient porous graphene oxide and preparation method thereof Download PDF

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CN109732918B
CN109732918B CN201811595184.5A CN201811595184A CN109732918B CN 109732918 B CN109732918 B CN 109732918B CN 201811595184 A CN201811595184 A CN 201811595184A CN 109732918 B CN109732918 B CN 109732918B
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庞媛
付乾
何玉婷
张武华
卢仁浩
谭勇
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Tsinghua University
Chongqing University
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Chongqing University
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Abstract

The invention provides a 3D printing gradient porous graphene oxide three-dimensional microbial electrode and a preparation method thereof. The gradient porous graphene oxide three-dimensional microbial electrode is used for passing Fe3+Or Ca2+Crosslinking with graphene oxide molecules, or further adding Fe3O4Or FeS2And the graphene oxide hydrogel prepared from the conductive nanoparticles is prepared by adopting a 3D printing technology as a material. The three-dimensional electrode with a gradient pore structure, good biocompatibility, conductivity and good interface electron transfer characteristics is manufactured by taking graphene oxide hydrogel as a printing material based on a 3D printing principle of low-temperature deposition, and is applied to a microbial electrochemical system to improve the electrochemical efficiency of the microbial electrochemical system.

Description

Three-dimensional microbial electrode for 3D printing of gradient porous graphene oxide and preparation method thereof
Technical Field
The invention belongs to the technical field of manufacturing of microbial electrochemical system electrodes in the field of renewable energy sources, and particularly relates to a three-dimensional microbial electrode with a gradient pore structure, and a preparation method and application thereof.
Background
The microbial electrochemical system is a novel energy conversion device and is mainly characterized in that electrochemical active bacteria attached to the surface of an electrode are used as a catalyst to drive the oxidation-reduction reaction of the electrode. The microbial fuel cell can degrade organic matters in the wastewater and generate current, and the microbial electrosynthesis system can produce fuel or chemicals under a small applied voltage (0.2V-0.8V). The microbial electrode, which is a core component of the performance of the microbial electrochemical system, is a key factor determining the performance of the microbial electrochemical system. At present, the microbial electrode material mostly adopts two-dimensional structures such as carbon cloth, carbon paper and the like, the surface area is small, the attachment amount of microbes on the surface is small, the interface transfer rate between a microbial catalyst and an electrode is low, the electrochemical activity biomass is small, and the electrochemical performance is poor. Therefore, the microbial electrode performance can be greatly improved by constructing a three-dimensional electrode structure which has controllable appearance, high specific surface area, good biocompatibility and good interface electron transfer characteristic.
Three-dimensional printing (3DP), one of the rapid prototyping techniques, is a technique for casting objects by layer-by-layer printing using a bondable material such as a powdered metal material or a polymer, based on a digital model file. Is commonly used in the fields of mold manufacturing, industrial design and the like, and is gradually used for manufacturing biological tissue bodies (such as cartilage, teeth and the like) in the field of clinical medicine after the introduction of high molecular biological materials.
The material has good viscosity when the graphene oxide hydrogel concentration is high, and can be used for preparing ink suitable for 3D printing. Meanwhile, the lap joint between graphene sheets can generate a porous structure, so that space is provided for the attachment and growth of microorganisms. In addition, the graphene oxide can be reduced into graphene by microorganisms, and has good conductivity.
Although the graphene structure has good conductivity and the graphene oxide hydrogel has high viscosity at high concentration, the process of preparing the three-dimensional electrode by using the graphene oxide hydrogel still has more problems: (1) problems with formation of graphene oxide hydrogels: even at higher concentrations, the viscosity of graphene oxide hydrogels is not sufficient to support the three-dimensional porous structures of 3D printing, and filament-to-filament adhesion and collapse of the overall structure are very likely to occur. (2) The problem of the forming precision of the graphene oxide hydrogel is as follows: because the graphene oxide hydrogel has certain elasticity, internal stress and large internal strain exist in the gel in the printing process, the extrusion and stop time of the printing wire cannot be accurately controlled, and the forming precision of the material is greatly influenced. (3) Conductivity problems of three-dimensional electrodes: graphene oxide itself is almost non-conductive and requires reduction of graphene oxide to graphene. However, reduction using the general hydroiodic acid method makes the electrode toxic and unsuitable for microbial growth. Meanwhile, the lap joint structure between graphene oxide sheet layers is not beneficial to effective retransmission of electrons. (4) The problem of interfacial electron transfer between the microbial catalyst attached to the electrode surface and the electrode: the ability of microorganisms to take electrons from the electrode (or the microorganisms oxidize organic substances to generate electrons and transfer the electrons to the surface of the electrode) has a decisive influence on the performance of the microbial electrochemical system, however, in the current microbial electrochemical system, the interface electron transfer rate between the microorganisms and the electrode is low.
Disclosure of Invention
In order to solve the technical problems, the invention aims to manufacture a three-dimensional electrode with a gradient pore structure, good biocompatibility, conductivity and good interface electron transfer characteristic by using graphene oxide hydrogel as a printing material based on a low-temperature deposition 3D printing principle so as to be applied to a microbial electrochemical system and improve the electrochemical efficiency of the microbial electrochemical system.
According to the performance requirements of a microbial electrochemical system on electrodes, the graphene oxide hydrogel is used as a printing material, and the preparation process and material characteristics of graphene oxide are explored; designing a three-dimensional model and a 3D printing scheme of the electrode; 3D printing equipment of graphene oxide is modified based on a low-temperature deposition technology, extrusion-based 3D printing (extrusion-based 3D printing) under a low-temperature condition is realized, and meanwhile, the room-temperature environment of a needle head and a needle tube part is kept; exploring optimal printing parameters based on the device; the physical and electrochemical properties of the novel electrode were finally evaluated by microscopic section observation and assembly of the microbial electrochemical system.
The research of the invention discovers that a proper amount of Fe is added into the graphene oxide hydrogel3+Or Ca2+The forming problem of the graphene oxide hydrogel can be solved, the three-dimensional porous structure for 3D printing can be supported, and the whole structure is not easy to collapse; the internal stress in the gel in the printing process is also improved, so that the extrusion and stop time of the printing wire can be accurately controlled, and the forming precision of the material can be controlled; further, Fe is added3+Or Ca2+And the conductivity of the graphene oxide hydrogel is improved. Further, by adding Fe3O4Or FeS2The conductive nanoparticles can promote long-range extracellular electron transfer processes in the microbial networks, including interface electron transfer between electrodes and microbes and between different populations of microbes. In addition, Fe3O4Or FeS2The conductive nano particles also have the characteristics of good biocompatibility, low cost, easy processing and the like, and have remarkable advantages.
Specifically, the invention provides a gradient porous graphene oxide three-dimensional microbial electrode which is prepared by passing Fe3+Or Ca2+And the graphene oxide hydrogel is crosslinked with graphene oxide molecules, and conductive nanoparticles are further added, so that the prepared graphene oxide hydrogel is taken as a material and is prepared by adopting a 3D printing technology. The conductive nanoparticles are preferably Fe3O4Or FeS2。
Specifically, by adding Fe to graphene oxide hydrogel3+Or Ca2+Of Fe3+Or Ca2+And the functional groups such as-COOH, -OH and the like in the graphene oxide molecules are subjected to crosslinking, so that the mechanical strength of the hydrogel network is further improved. At the same time, by further adding Fe3O4Or FeS2And waiting for the conductive nano particles to prepare a graphene oxide hydrogel material which meets the condition of the microbial electrode and can be used for 3D printing.
The invention also provides a preparation method of the gradient porous graphene oxide three-dimensional microbial electrode, which comprises the following steps: system for makingPreparing graphene oxide hydrogel, and adding Fe into the graphene oxide hydrogel3+Or Ca2+Of Fe3+Or Ca2+Performing crosslinking action with graphene oxide molecules (mainly-COOH, -OH and other functional groups) to prepare modified graphene oxide hydrogel; and further adding Fe3O4Or FeS2And (3) waiting for the conductive nano particles to prepare the gradient porous graphene oxide three-dimensional microbial electrode which meets the microbial electrode conditions and can be used for 3D printing.
In the above preparation method, the graphene oxide hydrogel can be prepared by a conventional method in the art, for example, a graphene oxide dispersion liquid is prepared by a Hummers method, and then the graphene oxide hydrogel is obtained by high-speed centrifugation at 18000rmp for 30 min.
Further, the concentration of the graphene oxide hydrogel is 20-30mg/ml, preferably 25 mg/ml.
Further, Fe added3+Or Ca2+The molar ratio of the graphene oxide to the graphene oxide molecules is 10-15:16-24, and preferably 14: 20.
Said Fe3+Or Ca2+Can be provided by conventional iron sources, calcium sources, such as Nantong Bady chemical Limited, Weifang essence snow-melting products Limited, and the like.
Further, Fe added3O4Or FeS2The concentration of the equal-conducting nano-particles in the graphene oxide hydrogel is 1.5-3mmol, and preferably 2.08 mmol.
In order to further improve the relevant performance of the gradient porous graphene oxide three-dimensional microbial electrode, the invention also optimizes relevant parameters of the 3D printing technology. Based on the previous process exploration and microscopic observation, researches find that the printing performances of the graphene oxide are different at different temperatures, and the 3D printing of the modified graphene oxide hydrogel needs to be carried out at a temperature of less than or equal to-10 ℃ to ensure the complete structure and the round silk section, and preferably, the printing is carried out at a temperature of-25 ℃ to-15 ℃.
On the basis, parameters such as the optimal printing temperature and the optimal printing speed of the graphene oxide are further explored. The specific forming parameters are as follows: forming chamber temperature: -15 ℃; temperature of the needle head and the needle tube: 25 ℃; the inner diameter of the dispensing needle is 160 and 300 mu m; extrusion speed: 0.25-0.40 mm/s; shearing speed: 10-15 mm/s; the layer height is 100-1000 μm. The preferable printing parameter is the inner diameter of the dispensing needle head is 200 mu m; extrusion speed: 0.3 mm/s; shearing speed: 12 mm/s; the layer height is 200-400 μm.
Further, a computer model of the novel electrode is designed based on the form and position requirements of the microbial electrochemical system on the electrode, and the printing path is generated by layering through software, so that a printing structure with the overall size of (12-21mm) × (12-21mm) × (3-10mm), the wire spacing of 1.0-3.0mm and the wire diameter of 200-400 μm is realized, and the preferred printing structure has the overall size of 20 × 20 × 5mm, the wire spacing of 2mm and the wire diameter of 250 μm.
Furthermore, the invention optimizes the treatment process of the microbial electrode manufactured by 3D printing. Specifically, the microbial electrode obtained by 3D printing is firstly stored at a low temperature of less than or equal to-80 ℃, and then freeze-dried at a low temperature to obtain the finished gradient porous graphene oxide three-dimensional microbial electrode. Lyophilization at low temperature is preferably carried out at 0.05mbar and-50 deg.C, and is typically carried out for 48 h.
Specifically, the preparation method of the gradient porous graphene oxide three-dimensional microbial electrode comprises the following steps: firstly, preparing a graphene oxide dispersion solution by a Hummers method, and then centrifuging at a high speed to obtain a graphene oxide hydrogel; to which Fe is internally added3+Or Ca2+Of Fe3+Or Ca2+Performing a crosslinking effect with graphene oxide molecules; and further adding Fe3O4Or FeS2Preparing modified graphene oxide hydrogel by using conductive nano particles; and 3D printing and low-temperature freeze-drying to prepare the gradient porous graphene oxide three-dimensional microbial electrode.
The invention also discloses the gradient porous graphene oxide three-dimensional microbial electrode prepared by the method.
The resistance of the gradient porous graphene oxide three-dimensional microbial electrode is 5.0-25.3 omega; the observation of a scanning electron microscope shows that mesopores with the size of several micrometers to dozens of micrometers generally exist on the horizontal surface and the cross section, and mesopores rarely exist on the vertical surface and the cross section; by mass estimation, its porosityThe rate is about 92.0% -98.7%; at a relative potential of 0V, the current density peak value of 15A/m can be reached2(ii) a After long-term operation (such as long-term electrogenic bacteria culture), the current density can reach 13A/m at most2Much higher than 2.5A/m of carbon cloth2The highest current density, shows good electrochemical performance. In a word, the microbial electrode has a gradient pore structure, good conductivity and good biocompatibility; can obviously improve the bacteria carrying capacity and the electron transmission rate of the microbial electrochemical system.
In order to further improve the related performance of the gradient porous graphene oxide three-dimensional microbial electrode and be more suitable for 3D printing of the modified graphene oxide hydrogel, the invention also designs 3D printing equipment special for graphene oxide gel based on a low-temperature deposition technology, wherein the 3D printing equipment comprises a 3D printing spray head, the 3D printing spray head comprises a feed pipe and a temperature control device connected with the feed pipe, and the temperature control device is used for controlling the temperature of a 3D printing material in the feed pipe. Further, the material of the temperature control device is copper.
Compared with the prior art, the invention has the beneficial effects that:
1) the preparation of the three-dimensional electrode with the gradient pore structure in the microbial electrochemical system is realized, and compared with two-dimensional electrodes such as carbon cloth, carbon paper and the like, the three-dimensional electrode has higher porosity and specific surface area, and is more beneficial to the attachment and growth of microorganisms.
2)3D printing of graphene oxide hydrogel under a low-temperature condition is achieved by using a low-temperature deposition technology, and a three-dimensional electrode with a gradient pore structure is achieved by using the technology. The rapid printing and forming of the structure can be realized by adopting a low-temperature deposition 3D printing technology.
3) Based on a multiple crosslinking mechanism, the overlapping structure between sheets and the crosslinking structure between functional groups are simultaneously realized in the graphene oxide hydrogel, the viscosity of the graphene oxide hydrogel is increased, and the forming performance and the forming precision of the graphene oxide hydrogel are obviously improved.
4) By adding Fe in graphene oxide hydrogel3O4(or FeS)2) Constant conductivity sodiumThe rice particles promote the electron transfer process of the interfaces between the microbial catalyst and the electrodes (between the electrodes and the microbial interfaces and between different groups of microbes), and reduce the charge transfer impedance, thereby improving the performance of the microbial electrochemical system and optimizing the microbial electrochemical system.
Drawings
FIG. 1: the invention discloses a 3D printing equipment structure schematic diagram (A) and a 3D printing spray head structure schematic diagram (B);
1 is 3D and prints the shower nozzle, 2 is the shaping structure, and 3 is the base plate, and 4 are the shaping room, and 5 are temperature control device (heating copper post), and 6 are 3D printing material, and 7 are the syringe needle.
FIG. 2: the invention relates to a structural schematic diagram (secondary mesoporous structure) and a partial enlarged view of a gradient porous graphene oxide three-dimensional microbial electrode.
Detailed Description
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention. The examples do not show the specific techniques or conditions, according to the technical or conditions described in the literature in the field, or according to the product specifications. The reagents or instruments used are conventional products available from regular distributors, not indicated by the manufacturer.
The following embodiments use a 3D printing apparatus as shown in fig. 1A, which includes a 3D printing head 1. The printing process is completed in the forming chamber 4, printing the forming structure 2 on the substrate 3. Fig. 1B is the enlargements of 3D print shower nozzle 1, 3D print shower nozzle 1 include the inlet pipe and with temperature control device 5 that the inlet pipe is connected still includes syringe needle 7, temperature control device 5 is used for controlling the temperature of 3D printing material 6 in the inlet pipe. Further, the temperature control device 5 is a heating copper column.
Example 1
Addition of Fe3+The preparation method of the cross-linked gradient porous graphene oxide three-dimensional microbial electrode comprises the following steps:
1) preparing graphene oxide dispersion liquid by a Hummers method, and centrifuging at a high speed of 18000rmp for 30min to obtain 25mg/ml graphene oxide hydrogel. 3.11w of graphene oxide hydrogelt% addition of 0.2 mol/L Fe3+Solution through Fe3+And the modified graphene oxide hydrogel is prepared by the crosslinking effect of the modified graphene oxide hydrogel and functional groups such as-COOH, -OH and the like in graphene oxide molecules, so that the mechanical strength of the hydrogel network is further improved.
2)3D printing to prepare gradient porous graphene oxide three-dimensional microbial electrode
A computer model of a novel electrode is designed based on the form and position requirements of a microbial electrochemical system on the electrode, and a printing path is generated by layering through software, so that a printing structure with the wire spacing of 1.5mm and the wire spacing of 20 × 20 × 10mm is realized.
The specific forming parameters are as follows: forming chamber temperature: -15 ℃; temperature of the needle head and the needle tube: 25 ℃; the inner diameter of the dispensing needle head is 200 mu m; extrusion speed: 0.3 mm/s; shearing speed: 12 mm/s; the layer height was 250 μm.
The material obtained by 3D printing is firstly stored at low temperature of-80 ℃, and then freeze-drying treatment is carried out at 0.05mbar, -50 ℃ and 48 hours to prepare the gradient porous graphene oxide three-dimensional microbial electrode
The porous graphene oxide three-dimensional microbial electrode prepared by the embodiment is applied to a microbial electrochemical system and can be directly reduced by electrogenic bacteria.
Experiment 1
And (3) carrying out physical and chemical performance test on the gradient porous graphene oxide three-dimensional microbial electrode prepared in the example 1.
1) Evaluation of physical Properties
The oxygen-containing functional group in the graphene of the gradient porous graphene oxide three-dimensional microbial electrode prepared in the embodiment 1 is reduced and oxidized by the electrogenic bacteria to measure the resistance of the graphene. The resistance of the novel electrode was measured to be 10 Ω by reduction reaction.
The observation of a scanning electron microscope shows that the novel electrode generally has mesopores with the range of several micrometers to dozens of micrometers on the horizontal surface and the cross section, and the mesopores rarely exist on the vertical surface and the cross section, which is caused by the material accumulation under the influence of gravity. The porosity of the novel electrode material was found to be about 97.9% by mass estimation.
2) Evaluation of electrochemical Properties
By usingThe gradient porous graphene oxide three-dimensional microbial electrode prepared in the example 1 is assembled into a complete microbial electrochemical system, and the microbial growth condition and the electrochemical performance of the complete microbial electrochemical system are evaluated by taking a carbon felt as a control group. At a starting potential of 50mV by Fe3+The cross-linked graphene oxide electrode can reach the current density peak value of 18A/m2Is the peak current density (4A/m) of the carbon felt2) About 4.5 times of the electrochemical performance of the electrochemical material shows good electrochemical performance.
Example 2
Addition of Ca2+The preparation method of the cross-linked gradient porous graphene oxide three-dimensional microbial electrode comprises the following steps:
1) preparing graphene oxide dispersion liquid by a Hummers method, centrifuging at a high speed of 18000rmp for 30min to obtain 25mg/ml graphene oxide hydrogel, and adding 0.2 mol/L Ca to the graphene oxide hydrogel according to a proportion of 3.11 wt%2+Solution through Ca2+And the modified graphene oxide hydrogel is prepared by the crosslinking effect of the modified graphene oxide hydrogel and functional groups such as-COOH, -OH and the like in graphene oxide molecules, so that the mechanical strength of the hydrogel network is further improved.
2)3D printing to prepare gradient porous graphene oxide three-dimensional microbial electrode
A computer model of a novel electrode is designed based on the form and position requirements of a microbial electrochemical system on the electrode, and a printing path is generated by layering through software, so that a printing structure with the wire spacing of 2mm and the wire spacing of 20 × 20 × 5mm is realized.
The specific forming parameters are as follows: forming chamber temperature: -15 ℃; temperature of the needle head and the needle tube: 25 ℃; the inner diameter of the dispensing needle head is 200 mu m; extrusion speed: 0.3 mm/s; shearing speed: 12 mm/s; the layer height was 250 μm.
The material obtained by 3D printing is firstly stored at low temperature of-80 ℃, and then is subjected to freeze-drying treatment at 0.05mbar, -50 ℃ and 48 hours to prepare the gradient porous graphene oxide three-dimensional microbial electrode (as shown in figure 2).
The porous graphene oxide three-dimensional microbial electrode prepared by the embodiment is applied to a microbial electrochemical system and can be directly reduced by electrogenic bacteria.
Experiment 2
And (3) carrying out physical and chemical performance test on the gradient porous graphene oxide three-dimensional microbial electrode prepared in the example 2.
1) Evaluation of physical Properties
The oxygen-containing functional groups in the graphene of the gradient porous graphene oxide three-dimensional microbial electrode prepared in example 2 were reduced and oxidized by 55% hydroiodic acid to measure the resistance thereof. The resistance of the novel electrode was measured to be 5 Ω by reduction reaction.
The observation of a scanning electron microscope shows that the novel electrode generally has mesopores with the range of several micrometers to dozens of micrometers on the horizontal surface and the cross section, and the mesopores rarely exist on the vertical surface and the cross section, which is caused by the material accumulation under the influence of gravity. The porosity of the novel electrode material was found to be about 98.7% by mass estimation.
2) Evaluation of electrochemical Properties
The gradient porous graphene oxide three-dimensional microbial electrode prepared in example 2 was assembled into a complete microbial electrochemical system, and the growth of microorganisms and electrochemical properties were evaluated using carbon cloth as a control. Under the starting of a relative potential of 0V, the novel electrode can reach the peak value of current density of 15A/m2Is the peak current density (3A/m) of the carbon cloth2) About 5 times of the total weight of the product. After long-time electrogenic bacteria culture, the current density of the novel electrode can reach 13A/m to the maximum2Much higher than 2.5A/m of carbon cloth2The highest current density, shows good electrochemical performance.
Example 3
Addition of Fe3+Crosslinking and using Fe3O4The preparation method of the gradient porous graphene oxide three-dimensional microbial electrode with the interface electron transfer reinforced by the nano particles comprises the following steps:
1) preparing graphene oxide dispersion liquid by a Hummers method, centrifuging at a high speed of 18000rmp for 30min to obtain 25mg/ml graphene oxide hydrogel, and adding 0.2 mol/L Fe into the graphene oxide hydrogel according to the proportion of 3.11 wt%3+Solution with 2.08mmol Fe3O4And (3) fully mixing the nano particles to prepare the modified 3D printing graphene oxide ink.
2)3D printing to prepare gradient porous graphene oxide three-dimensional microbial electrode
A computer model of a novel electrode is designed based on the form and position requirements of a microbial electrochemical system on the electrode, and a printing path is generated by layering through software, so that a printing structure with the wire spacing of 2mm and the wire spacing of 20 × 20 × 5mm is realized.
The specific forming parameters are as follows: forming chamber temperature: -15 ℃; temperature of the needle head and the needle tube: 25 ℃; the inner diameter of the dispensing needle head is 200 mu m; extrusion speed: 0.3 mm/s; shearing speed: 12 mm/s; the layer height was 250 μm.
The material obtained by 3D printing is firstly stored at low temperature of-80 ℃, and then freeze-drying treatment is carried out at 0.05mbar, -50 ℃ and 48 hours to prepare the gradient porous graphene oxide three-dimensional microbial electrode
The gradient porous graphene oxide three-dimensional microbial electrode prepared in the embodiment is applied to a microbial electrochemical system and is directly reduced by electrogenic bacteria.
Experiment 3
The microbial electrode prepared in example 3 and the microbial electrode prepared in example 1 were subjected to electrochemical impedance tests in a microbial electrochemical system, and the results show that the shapes of the electrochemical impedance curves of the two electrodes are similar. The electron transfer impedance of the microbial electrode prepared in example 3 was 12.6 Ω, and the electron transfer impedance of the microbial electrode prepared in example 1 was 25.3 Ω, which indicates that the addition of the conductive nanoparticles can increase the electron transfer rate at the interface between the microbe and the electrode, and promote the electron transfer outside the microbe cell, so as to achieve higher power density.
Example 4
The only difference from example 3 is that Fe3O4Replacement by FeS2And (3) preparing a gradient porous graphene oxide three-dimensional microbial electrode for enhancing interface electron transfer by using nano particles. The electrochemical properties of the prepared microbial electrode are similar to those of the microbial electrode in example 3.
Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims (13)

1. A gradient porous graphene oxide three-dimensional microbial electrode is prepared by passing Fe3+Or Ca2+The graphene oxide hydrogel is cross-linked with graphene oxide molecules and further added with conductive nanoparticles and is prepared by adopting a 3D printing technology as a material; the conductive nano-particles are Fe3O4Or FeS2；
Wherein the concentration of the graphene oxide hydrogel is 20-30 mg/ml;
added Fe3+Or Ca2+The molar ratio of the graphene oxide to graphene oxide molecules is 10-15: 16-24;
the concentration of the added conductive nanoparticles in the graphene oxide hydrogel is 1.5-3 mmol;
the 3D printing is performed at a temperature of-25 ℃ to-15 ℃.
2. The gradient porous graphene oxide three-dimensional microbial electrode of claim 1,
the concentration of the graphene oxide hydrogel is 25 mg/ml;
added Fe3+Or Ca2+The molar ratio to graphene oxide molecules is 14: 20;
the concentration of the added conductive nanoparticles in the graphene oxide hydrogel was 2.08 mmol.
3. A preparation method of a gradient porous graphene oxide three-dimensional microbial electrode is characterized by comprising the following steps: preparing graphene oxide hydrogel, and adding Fe therein3+Or Ca2+Of Fe3+Or Ca2+Performing a crosslinking effect with graphene oxide molecules, and further adding conductive nanoparticles to prepare modified graphene oxide hydrogel; 3D printing to prepare a gradient porous graphene oxide three-dimensional microbial electrode; the electric conductionThe nano-particles are Fe3O4Or FeS2；
Wherein the concentration of the graphene oxide hydrogel is 20-30 mg/ml;
added Fe3+Or Ca2+The molar ratio of the graphene oxide to graphene oxide molecules is 10-15: 16-24;
the concentration of the added conductive nanoparticles in the graphene oxide hydrogel is 1.5-3 mmol;
the 3D printing is performed at a temperature of-25 ℃ to-15 ℃.
4. The preparation method according to claim 3, wherein the concentration of the graphene oxide hydrogel is 25 mg/ml;
added Fe3+Or Ca2+The molar ratio to graphene oxide molecules is 14: 20;
the concentration of the added conductive nanoparticles in the graphene oxide hydrogel was 2.08 mmol.
5. The method of manufacturing according to claim 3, wherein the 3D printing forming parameters are: forming chamber temperature: -15 ℃; temperature of the needle head and the needle tube: 25 ℃; the inner diameter of the dispensing needle is 160 and 300 mu m; extrusion speed: 0.25-0.40 mm/s; shearing speed: 10-15 mm/s; the layer height is 100-1000 μm; and/or the presence of a gas in the gas,
the 3D printing structure is (12-21mm) × (12-21mm) × (3-10mm), the distance between the wires is 1.0-3.0mm, and the diameter of the wires is 200-400 mu m.
6. The method according to claim 5, wherein the printing parameters are a dispensing needle inner diameter of 200 μm; extrusion speed: 0.3 mm/s; shearing speed: 12 mm/s; the layer height is 200-400 μm; and/or the presence of a gas in the gas,
the 3D printing structure was 20 × 20 × 5mm, the filament spacing was 2mm, and the filament diameter was 250 μm.
7. The preparation method according to any one of claims 3 to 6, further comprising the steps of preserving the microbial electrode obtained by 3D printing at a low temperature of less than or equal to-80 ℃, and then performing low-temperature freeze-drying to obtain the finished gradient porous graphene oxide three-dimensional microbial electrode.
8. The method of claim 7, wherein the lyophilization is carried out at 0.05mbar and-50 ℃.
9. The method according to any one of claims 3 to 6 and 8, comprising: firstly, preparing a graphene oxide dispersion solution by a Hummers method, and then centrifuging at a high speed to obtain a graphene oxide hydrogel; to which Fe is internally added3+Or Ca2+Of Fe3+Or Ca2+Performing a crosslinking effect with graphene oxide molecules, and further adding conductive nanoparticles to prepare modified graphene oxide hydrogel; and 3D printing and low-temperature freeze-drying to prepare the gradient porous graphene oxide three-dimensional microbial electrode.
10. The gradient porous graphene oxide three-dimensional microbial electrode prepared by the method of any one of claims 3 to 9.
11. The gradient porous graphene oxide three-dimensional microbial electrode of claim 1, 2 or 10, wherein the resistance is 5.0-25.3 Ω; the mesoporous material has the advantages that the mesoporous materials with different sizes from several micrometers to dozens of micrometers are commonly present on the horizontal surface and the cross section, and the mesoporous materials are rarely present on the vertical surface and the cross section; a porosity of about 92.0-98.7%; under the starting of a relative potential of 0V, the current density peak value of 15A/m can be reached2(ii) a After long-time operation, the current density can reach 13A/m at most2。
12. The preparation method according to any one of claims 3-6 and 8, wherein the adopted 3D printing equipment comprises a 3D printing spray head, the 3D printing spray head comprises a feeding pipe and a temperature control device connected with the feeding pipe, and the temperature control device is used for controlling the temperature of the 3D printing material in the feeding pipe.
13. The manufacturing method according to claim 12, wherein the 3D printing apparatus is used in which the material of the temperature control device is copper.
CN201811595184.5A 2018-12-25 2018-12-25 Three-dimensional microbial electrode for 3D printing of gradient porous graphene oxide and preparation method thereof Active CN109732918B (en)

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