阅读说明：本技术 一种用于微生物燃料电池的高活性碳基电极材料及其制备方法和应用 (High-activity carbon-based electrode material for microbial fuel cell and preparation method and application thereof ) 是由 卢锡洪 周丽君 于 2021-07-28 设计创作，主要内容包括：本发明提供一种用于微生物燃料电池的高活性碳基电极材料及其制备方法和应用。本发明使用高分子凝胶剂作为功能碳材料对碳材料表面进行修饰,同时,选用镍盐和氢氧化钾分别对功能碳材料和碳材料进行制孔,能够得到具有特定形貌的多孔碳基底上负载有多孔功能碳材料的碳基电极材料。该碳基电极材料具有特定的多孔形貌,可以显著增加碳材料的比表面积,有利于提高微生物的吸附量,进而提高电池的功率密度,与未处理的碳材料相比,制备得到的微生物燃料电池的功率密度至少提高了102.5％。(The invention provides a high-activity carbon-based electrode material for a microbial fuel cell, and a preparation method and application thereof. According to the invention, a polymer gel is used as a functional carbon material to modify the surface of the carbon material, and meanwhile, a nickel salt and potassium hydroxide are selected to respectively perform hole making on the functional carbon material and the carbon material, so that the carbon-based electrode material with a specific morphology and loaded with the porous functional carbon material on the porous carbon substrate can be obtained. The carbon-based electrode material has a specific porous morphology, the specific surface area of the carbon material can be remarkably increased, the adsorption quantity of microorganisms can be improved, the power density of the cell is further improved, and compared with an untreated carbon material, the power density of the prepared microbial fuel cell is at least improved by 102.5%.)

1. A preparation method of a carbon-based electrode material is characterized by comprising the following steps:

s1, dissolving nickel salt, potassium hydroxide and a polymer gel in water to form hydrogel;

s2, soaking the carbon substrate in the hydrogel obtained in S1, and drying to obtain a gel-coated carbon substrate;

and S3, activating the dried gel-coated carbon substrate in the inert atmosphere at 500-1000 ℃ for 1-4 h, and eluting nickel salt to obtain the carbon-based electrode material.

2. The preparation method of the carbon-based electrode material according to claim 1, wherein the nickel salt in S1 is one or a combination of nickel chloride, nickel acetate, nickel sulfate and nickel nitrate.

3. The preparation method of the carbon-based electrode material according to claim 1, wherein the polymer gelling agent in S1 is one or a combination of several of polyvinylpyrrolidone, polyvinyl alcohol and polyacrylamide.

4. The preparation method of the carbon-based electrode material as claimed in claim 3, wherein the polymer gelling agent in S1 is polyvinylpyrrolidone.

5. The preparation method of the carbon-based electrode material as claimed in claim 1, wherein the molar ratio of the nickel salt, the potassium hydroxide and the polymer gelling agent in S1 is 0.05-0.5: 0.1-4.

6. The preparation method of the carbon-based electrode material according to claim 1, wherein in S2, the carbon substrate is one or more of carbon paper, carbon felt and carbon cloth.

7. The preparation method of the carbon-based electrode material as claimed in claim 1, wherein the soaking time in S2 is 30-120 min.

8. The preparation method of the carbon-based electrode material according to claim 1, wherein the drying temperature in S2 is 60-100 ℃.

9. A carbon-based electrode material, characterized by being prepared by the preparation method of any one of claims 1 to 8.

10. Use of the carbon-based electrode material according to claim 9 for the preparation of a microbial fuel cell.

Technical Field

The invention belongs to the field of microbial fuel cells, and particularly relates to a high-activity carbon-based electrode material for a microbial fuel cell, and a preparation method and application thereof.

Background

As a bioelectrochemical device that converts organic substances into electrical energy using microorganisms, Microbial Fuel Cells (MFCs) have been drawing attention because of their advantages of environmental protection, safety, low cost, and dual functions of disposing waste and generating electricity. Unfortunately, microbial fuel cells have a troublesome short plate-low power density, which has greatly limited their application and development in the field of energy production. Therefore, increasing the power density of microbial fuel cells has been an important direction for their research and development.

The comprehensive performance of the microbial fuel cell is closely related to electrode materials, the specific configuration of the cell, the operation condition of the cell, nutrient solution and the like. Among them, the electrochemical properties of the cathode material and the anode material are more important factors influencing the electricity generation of the microbial fuel cell. As a novel electrode material, the carbon-based material has the advantages of higher intrinsic conductivity, lower cost, environmental friendliness and the like, and is an electrode material with a good application prospect. Nevertheless, the various properties of the carbon-based materials currently in commercial use still cannot meet the performance requirements of the current microbial fuel cells. Therefore, many efforts have been made in the research for selecting and modifying carbon-based materials, such as: chinese patent CN102881906A utilizes hydrazine hydrate to modify the functional groups on the surface of the carbon-based material, so as to improve the attachment of microorganisms and the migration of electrons between the microorganisms and the electrodes, and improve the maximum power density of the battery, but hydrazine hydrate has certain toxicity and certain pollution to the environment; chinese patent CN111430730A deposits reduced graphene oxide on the surface of carbon fiber by electrochemical reduction method to increase the specific surface area of the material and increase the power density of the microbial fuel cell, but the electrochemical treatment method and graphene oxide raw material used in the method have higher cost.

Although the modification strategy improves the electricity generation performance of the carbon electrode to a certain extent, the modification strategy has the problems of high cost, environmental friendliness and the like. Therefore, there is a need to develop a method for modifying a carbon-based electrode material for microbial fuel cells, which is environmentally friendly, low in cost, and has excellent electrochemical properties.

Disclosure of Invention

In order to overcome the defects, the invention provides a preparation method of a carbon-based electrode material for a microbial fuel cell, which is environment-friendly, low in cost and excellent in electrochemical performance.

Another object of the present invention is to provide a carbon-based electrode material prepared by the above preparation method.

The invention also aims to provide application of the carbon-based electrode material in preparation of a microbial fuel cell.

In order to solve the technical problems, the invention adopts the following technical scheme:

a preparation method of a carbon-based electrode material comprises the following steps:

s1, dissolving nickel salt, potassium hydroxide and a polymer gel in water to form hydrogel;

s2, soaking the carbon substrate in the hydrogel obtained in S1, and drying to obtain a gel-coated carbon substrate;

and S3, activating the dried gel-coated carbon material in the inert atmosphere at 500-1000 ℃ for 1-4 h, and eluting nickel salt to obtain the carbon-based electrode material.

The inventor creatively discovers that the nickel salt and the potassium hydroxide can be uniformly dispersed and embedded in the hydrogel by mixing and dissolving the nickel salt and the potassium hydroxide with the polymer gel, the carbon substrate is coated by the hydrogel to form a coating layer, and the carbon-based anode material with a specific shape and structure can be obtained by calcining. Specifically, in the calcining process, the potassium hydroxide in the gel is removed from the gel, so that on one hand, the potassium hydroxide can be fully contacted with the carbon substrate, and the formation of a porous morphology on the carbon substrate is facilitated; on the other hand, the gel can form a functional carbon material coating layer after being calcined, and the coating layer can form a porous structure after the potassium hydroxide is removed from the gel; in addition, the nickel salt in the gel is still embedded in the coating layer in the calcining process, and the coating layer can form a richer porous structure after elution.

According to the method, the carbon substrate is coated by the specific hydrogel, and the carbon substrate and the coating layer are both in rich porous structures after calcination and elution treatment, so that the carbon-based anode material has a larger specific surface area, is beneficial to long-term and stable adsorption of microorganisms, and further improves the power density of the battery.

Preferably, in S1, the nickel salt is one or a combination of nickel chloride, nickel acetate, nickel sulfate and nickel nitrate.

Further preferably, in s1, the nickel salt is nickel chloride.

Preferably, in s1, the polymer gelling agent is one or a combination of several of polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylamide. The specific polymer gel of the invention can obtain the aperture with smaller particle size and larger specific surface area, is beneficial to improving the adsorption capacity of microorganisms and improving the power density of the battery.

In order to further increase the power density of the battery, the polymer gelling agent in s1. is preferably polyvinylpyrrolidone.

Preferably, in S1, the molar ratio of the nickel salt, the potassium hydroxide and the polymer gel is 0.05-0.5: 0.1-4.

Further preferably, the molar ratio of the nickel salt, the potassium hydroxide and the polymer gelling agent in S1 is 0.2:1: 1.

Preferably, in s2, the carbon substrate is one or a combination of more of carbon paper (including flexible carbon paper and common carbon paper), carbon felt, and carbon cloth.

In order to make the carbon substrate surface have more adsorption sites and load more functional carbon material, the carbon substrate in s2 is further preferably carbon felt.

Preferably, the mass ratio of the carbon substrate to the polymer gel agent is 0.75: 10 to 400.

Preferably, the soaking time in S2 is 30-120 min, and further preferably 60 min.

Preferably, the drying in s2. is conventional drying.

Further preferably, in S2, the drying is vacuum drying or electrothermal blowing drying.

Preferably, the drying temperature in the S2 is 60-100 ℃, and more preferably 80 ℃.

Preferably, the drying time in S2 is 12-48 h, and further preferably 24 h.

Preferably, in S3, the inert atmosphere is an atmosphere formed by one or a combination of several gases of nitrogen, helium or argon.

Preferably, the temperature of said activation in s3. is 750 ℃.

Preferably, the activation time in s3. is 2 h.

Preferably, in S3, the elution of the nickel salt is performed by acid washing and water washing in sequence. In order to remove nickel salt in the activated electrode material or nickel oxide formed in the activation process and obtain the porous material, the acid washing is selected from 3mol/L hydrochloric acid washing for at least 30 min.

Preferably, the step S3 further comprises drying after the nickel salt is eluted.

A carbon-based electrode material is prepared by the preparation method. The carbon-based electrode material is a multi-layer pore structure modified with a porous functional carbon material on a porous carbon substrate, and the pore diameter is about 0.2-0.4 mu m.

The application of the carbon-based electrode material in the preparation of the microbial fuel cell is also within the protection scope of the invention.

Compared with the prior art, the invention has the beneficial effects that:

the preparation method can obtain the carbon-based electrode material loaded with the porous functional carbon material on the porous carbon substrate, the surface of the carbon-based electrode material is rough and is full of holes, the specific multilayer hole structure can obviously increase the specific surface area of the carbon material, and is beneficial to improving the adsorption capacity of microorganisms, so that the power density of the cell is improved, and compared with the untreated carbon material, the power density of the prepared microbial fuel cell is at least improved by 102.5%.

Drawings

FIG. 1 is an SEM surface topography of a carbon-based electrode material prepared in example 1 and an unactivated carbon felt of comparative example 3;

FIG. 2 is a cyclic voltammogram of a microbial fuel cell prepared from the carbon-based electrode materials prepared in example 1 and comparative example 3;

FIG. 3 is an electrochemical impedance diagram of a microbial fuel cell prepared from the carbon-based electrode materials prepared in example 1 and comparative example 3;

FIG. 4 is a plot of polarization curve and power density after stable operation of the HACF-1(b) prepared in example 1, and the CF (a) of comparative example 3;

FIG. 5 is a graph showing the polarization curve and power density after stable operation of the electrode prepared from the ACF-2(b) activated only with potassium hydroxide prepared in comparative example 1 and the ACF-1(a) activated only with nickel chloride prepared in comparative example 2.

Detailed Description

The present invention will be further described with reference to the following specific examples and drawings, which are not intended to limit the invention in any manner. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated. Unless otherwise indicated, reagents and materials used in the present invention are commercially available.

Example 1

The embodiment provides a carbon-based electrode material, and a preparation method thereof comprises the following steps:

s1.0.02mol of nickel chloride, 0.1mol of potassium hydroxide and 0.1mol of polyvinylpyrrolidone are sequentially dissolved in 100mL of deionized water and stirred until uniform hydrogel is formed;

s2, arranging the area to be 5 multiplied by 5cm^-2(0.03g cm)^-2) Soaking a carbon felt in the hydrogel obtained in the step S1, standing and soaking for 60min, and transferring to a vacuum drying oven to dry for 24h at the temperature of 80 ℃ to obtain a gel-coated carbon material;

s3, placing the carbon material coated with the gel obtained in the step S2 in a tubular furnace, activating for 2 hours at 750 ℃ in a nitrogen atmosphere with the flow rate of 50sccm, washing the activated product for 30 minutes by using 3mol/L hydrochloric acid, washing the product clean by using deionized water, and drying for 24 hours at 60 ℃ to obtain the carbon-based electrode material, wherein the carbon-based electrode material is marked as HACF-1.

Example 2

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: s1, adding 0.01mol of nickel chloride; and S3, marking the carbon-based electrode material prepared in the step A as HACF-2.

Example 3

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: s1, adding 0.04mol of nickel chloride; and S3, marking the carbon-based electrode material prepared in the step A as HACF-3.

Example 4

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: s1, adding 0.05mol of potassium hydroxide; and S3, marking the carbon-based electrode material prepared in the step A as HACF-4.

Example 5

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: s1, adding 0.2mol of potassium hydroxide; and S3, marking the carbon-based electrode material prepared in the step A as HACF-5.

Example 6

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: s1, adding 0.05mol of polyvinylpyrrolidone; and S3, marking the carbon-based electrode material prepared in the step A as HACF-6.

Example 7

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: s1, adding 0.2mol of polyvinylpyrrolidone; and S3, marking the carbon-based electrode material prepared in the step A as HACF-7.

Example 8

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: and S3, the activation temperature is 600 ℃, and the prepared carbon-based electrode material is marked as HACF-8.

Example 9

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: and S3, the activation temperature is 900 ℃, and the prepared carbon-based electrode material is marked as HACF-9.

Example 10

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: and S3, the activation time is 1h, and the prepared carbon-based electrode material is marked as HACF-10.

Example 11

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: and S3, the activation time is 4h, and the prepared carbon-based electrode material is marked as HACF-11.

Example 12

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: s1, replacing nickel chloride with nickel nitrate, and marking the carbon-based electrode material prepared in S3 as HACF-12.

Example 13

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: s1, replacing nickel nitrate with nickel acetate, and marking the carbon-based electrode material prepared in S3 as HACF-13.

Example 14

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: s1, polyvinyl pyrrolidone is replaced by polyvinyl alcohol, and the carbon-based electrode material prepared in S3 is marked as HACF-14.

Example 15

The embodiment provides a carbon-based electrode material, and the preparation method thereof is different from that of embodiment 1 in that: s1, replacing polyvinylpyrrolidone with polyacrylamide, and S3, marking the prepared carbon-based electrode material as HACF-15.

Comparative example 1

The present comparative example provides a carbon-based electrode material, and the preparation method thereof is different from that of example 1 in that: s1, nickel chloride is not added; and S3, marking the prepared carbon-based electrode material as ACF-1.

Comparative example 2

The present comparative example provides a carbon-based electrode material, and the preparation method thereof is different from that of example 1 in that: s1, potassium hydroxide is not added; and S3, marking the prepared carbon-based electrode material as ACF-2.

Comparative example 3

This comparative example uses a carbon felt without any treatment as the carbon-based electrode material, noted CF.

Performance testing

1. Topography characterization

The carbon-based electrode material prepared in example 1 and the surface morphology of the carbon felt of comparative example 3 were characterized, and the characterization results are shown in fig. 1, where a and c in fig. 1 are the surface morphology and the enlarged view of the carbon felt that is not activated (comparative example 3), respectively, and it can be seen that the surface of the carbon felt that is not activated is relatively smooth; in fig. 1, b and d are the surface morphology and the enlarged view of the carbon-based electrode material prepared in example 1, respectively, and it can be seen that the surface of the electrode material prepared by the method of the present invention is filled with pores, and the pore diameter is about 0.2 to 0.4 μm.

2. Electrochemical performance

The carbon-based electrode materials prepared in the above examples and comparative examples were prepared into a microbial fuel cell, and then an electrochemical performance test was performed, wherein the microbial fuel cell consisted of: the microbial fuel cell takes the carbon-based electrode material prepared in the above examples and comparative examples as a working electrode, an Ag/AgCl electrode as a reference electrode, a platinum wire as a counter electrode and an electrolyte of 0.05mol/L K₃[Fe(CN)₆]KCl solution.

2.1 Cyclic voltammetry test (CV)

The electrochemical workstation CHI760E is used to perform Cyclic Voltammetry (CV) tests on microbial fuel cells prepared from the carbon-based electrode materials prepared in the following example 1 and comparative example 3, wherein the test conditions are as follows: the carbon-based electrode material prepared in the above examples and comparative examples was used as a working electrode, an Ag/AgCl electrode was used as a reference electrode, a platinum wire was used as a counter electrode, and an electrolyte was used at 0.05mol/L K, using an electrochemical workstation CHI760E manufactured by Shanghai Hua Co., Ltd₃[Fe(CN)₆]The test was carried out in a three-electrode system in KCl solution at a sweep rate of 10 mV/s. The test results are shown in FIG. 2, and it can be seen from FIG. 2 that the capacitance performance of the activated carbon felt electrode is greatly improved, and the capacitance of the activated carbon felt electrode is about that of the activated carbon felt electrode which is not processed by calculating the area of the cycle curve chartThe capacitance of the overactivated carbon felt is 7.6 times that of the activated carbon felt.

2.2 electrochemical impedance test (EIS)

Electrochemical impedance testing (EIS) was performed on microbial fuel cells prepared from the carbon-based electrode materials prepared in example 1(HACF electrode) and comparative example 3(CF electrode) using electrochemical workstation CHI760E, under the following specific test conditions: the carbon-based electrode material prepared in the above examples and comparative examples was used as a working electrode, an Ag/AgCl electrode was used as a reference electrode, a platinum wire was used as a counter electrode, and an electrolyte was used at 0.05mol/L K, using an electrochemical workstation CHI760E manufactured by Shanghai Hua Co., Ltd₃[Fe(CN)₆]The test was carried out in a three-electrode system of KCl solution at a frequency range of 0.01Hz to 100kHz, an amplitude of 5mV, and a scanning potential of open circuit potential. The test results are shown in fig. 3, from which it can be seen that the diameter of the half circle after activation is significantly reduced in the high frequency region, indicating that the HACF electrode is significantly more conductive than the CF electrode, and from which it can be seen that the impedance of the HACF electrode is about 0.1 times that of the CF electrode; meanwhile, the slope of the straight line in the low-frequency region is obviously increased, which shows that the ion diffusion rate of the HACF electrode is obviously higher than that of the CF electrode and is about 2 times of that of the CF electrode.

2.3 polarization curves and Power Density

The research system is a double-chamber microbial fuel cell, wherein the anode is the electrode material obtained in the examples and the comparative examples, the cathode is carbon paper with the same area (2cm multiplied by 3cm) as the anode material, the anode nutrient solution is 0.05mol/L sodium acetate which is pretreated (sterilized in a high-temperature sterilization pot at 130 ℃ for 20 min), and the cathode aeration rate is 70mL min^-1The membrane is a commercial cation exchange membrane (Sigma-Aldrich, Nafion)^TM117) The activated sludge is respectively and uniformly inoculated in a cathode chamber and an anode chamber of the reactor, and the whole device is placed at room temperature (25-30 ℃). The test conditions were: the polarization curve and the power density are both tested by adopting an LVS (Linear Sweep volt measurement) technology, and the test is carried out under the test conditions that the open-circuit potential is used as the starting voltage, the ending potential is 0.7V, and the scanning speed is 0.01 mV/s.

The test results are shown in FIG. 4 (graph of polarization curve and power density after stable operation of the electrode prepared in HACF-1(b) prepared in example 1, CF (a) of comparative example 3) and FIG. 5 (graph of polarization curve and power density after stable operation of the electrode prepared in ACF-2(b) activated only by potassium hydroxide prepared in comparative example 1, ACF-1(a) activated only by nickel chloride prepared in comparative example 2) and Table 1.

TABLE 1 maximum Power Density (mW m) of electrode materials prepared in examples and comparative examples^-2)

As can be seen from fig. 4, the electrode obtained in the comparative example had (a) a current decreased from 0.65V to 0.3V and a polarization of 0.35V; whereas (b) the current of the electrode prepared in example was reduced from 0.56V to 0.28V and the polarization was 0.28V, and thus it was seen that the polarization of the electrode after activation became small. While the polarization of the electrodes activated with only nickel chloride or only potassium hydroxide is comparable (as shown in figure 5).

As can be seen from Table 1, the maximum power density of the microbial fuel cell can be remarkably improved by the electrode material prepared by the preparation method provided by the invention, and the maximum power density of the electrode can be as high as 7100mW m^-2The power density (2297mW m) of the non-activated electrode (comparative example 3)^-2) 3.1 times of the total weight of the powder.

As can be seen from the data of the other examples, the reaction conditions (such as the kind and amount of nickel salt, the amount of potassium hydroxide, the kind and amount of polymer gel agent, the activation temperature and time, etc.) have a small influence on the performance (maximum power density) of the resulting microbial fuel cell. The maximum power density of the microbial fuel cell prepared in each example of the invention is improved by at least 49.8% compared with that of the microbial fuel cell prepared in comparative example 1 (activated by potassium hydroxide); compared with the comparative example 2 (only using nickel chloride for activation), the improvement is at least 15.2%; the maximum power density is improved by at least 102.5% compared with the maximum power density of the electrode without activation (comparative example 3).

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.