A method for preparing anode modified with metal compound

Abstract

The present invention belongs to the technical field of anode material preparation, and specifically relates to a method for preparing a metal compound modified anode. First, a substrate is placed in a mixed acid for pretreatment, and then ammonium molybdate, ammonium tungstate and dopamine hydrochloride are dissolved in deionized water. Next, the pretreated substrate is placed in the mixed acid for full immersion, and the pH value is adjusted with ammonia water. After being kept at room temperature for 4-24 hours, the substrate is taken out, repeatedly washed with deionized water, and dried. Finally, the substrate is placed in a reducing atmosphere including hydrogen and calcined to obtain a metal compound modified anode. The metal compound has a large specific surface area and can provide a large number of attachment sites for electricity-producing microorganisms, which is conducive to the enrichment and growth of electrochemically active biofilms, greatly improving the electrocatalytic activity of the anode, accelerating the charge transfer efficiency between the electrochemical biofilm and the electrode interface, significantly improving the power generation performance of microbial fuel cells, and can be mass-produced.

Description

Technical field:

[0001] The present invention belongs to the technical field of anode material preparation, and in particular relates to a method for preparing anodes modified with metal compounds, which can mass-produce anode materials particularly suitable for microbial fuel cells. Background technology:

[0002] Microbial fuel cells (MFCs) are bioelectrochemical devices that utilize the extracellular electron transfer mechanism of electricity-producing microorganisms to directly convert the chemical energy in organic matter into electrical energy. Electricity-producing microorganisms are widely found in oxygen-deficient environments such as soil, aquatic sediments, surface water, and groundwater. They can transfer electrons generated by metabolizing organic matter along the respiratory chain to extracellular electron acceptors. Therefore, MFCs have the advantages of mild operating conditions, high energy conversion efficiency, and no pollution to the environment. They have a wide range of applications in power generation, sewage treatment and other fields.

[0003] Existing MFCs suffer from low output power, and the anode is a key factor limiting their output power. As a carrier of electrogenic microorganisms, the anode not only affects the metabolic activity of the electrogenic microorganisms attached to the anode surface, but also the efficiency of charge transfer between the electrogenic microorganisms and the anode. Currently, commonly used anodes such as carbon plates and carbon cloth have problems such as small specific surface area, low porosity, weak electrocatalytic activity, and poor biocompatibility. Anodes with small specific surface area and low porosity provide fewer attachment sites for electrogenic microorganisms; and anodes with poor electrocatalytic activity significantly increase the charge transfer resistance between the electrogenic microorganisms and the anode. Based on this, to improve the output power of MFCs, the following approaches can be considered to improve the anode: (1) increase the specific surface area of ​​the anode to provide more attachment sites for electrogenic microorganisms. This is because as the number of attachment sites on the anode increases, the number of attached electrogenic microorganisms also increases, and the number of electrons generated also increases accordingly; (2) select an anode with excellent electrocatalytic activity to significantly reduce the charge transfer resistance between the electrogenic microorganisms and the anode, thereby achieving efficient charge transfer; (3) make the anode have good biocompatibility. This is because an anode with good biocompatibility is more conducive to the attachment of electrogenic microorganisms, thereby increasing the number of electrogenic microorganisms on the anode surface and reducing the obstacles for electrogenic microorganisms to transfer electrons to the anode.

[0004] Chinese Patent No. 201510468208.0 discloses a method for preparing a self-doping microbial fuel cell anode material, comprising the following steps:

[0005] (1) drying, grinding, and sieving the activated sludge, and calcining it at 600-900° C. for 2-4 hours under an inert gas atmosphere to obtain a sludge carbon material;

[0006] (2) adding the sludge carbon material and the conductive polymer monomer in step (1) into water and mixing them to obtain a mixed solution; subjecting the mixed solution to electrochemical polymerization deposition in a three-electrode system, and naturally drying to obtain a microbial fuel cell anode material;

[0007] The activated sludge in step (1) is nitrogen-rich activated sludge, oxygen-rich activated sludge, or nitrogen- and oxygen-rich activated sludge; the conductive polymer monomer in step (2) is pyrrole or aniline; the concentration of the conductive polymer monomer in the mixed solution is 0.1-0.5 mol / L, and the concentration of the sludge carbon material is 1-15 mg / mL; the conditions for the electrochemical polymerization deposition in step (2) are: a constant voltage of 0.8 V and an electroplating amount per unit area of ​​0.5-5 C; the mixing in step (2) refers to mechanical stirring first and then ultrasonic dispersion, the mechanical stirring speed is 500-700 r / min, the mechanical stirring time is 10-15 min; the ultrasonic dispersion time is 5-10 min.

[0008] Chinese Patent No. 201910743508.3 discloses a method for preparing anode materials for microbial fuel cells, comprising the following steps:

[0009] S1. Drying and grinding the straw and mixing it with water, and heating it at 200-300° C. for 2-4 hours under an inert gas atmosphere, filtering and drying to obtain carbonized straw; soaking the carbonized straw in a mixed solution of trifluoroacetic acid, polystyrene sulfonic acid and diethylenetriamine penta (methylene phosphoric acid) at 40-60° C. for 12-24 hours and then naturally drying to obtain a straw carbon material; the mass ratio of the trifluoroacetic acid, polystyrene sulfonic acid and diethylenetriamine penta (methylene phosphoric acid) is 1:2.2-5.6:1.3-2.7;

[0010] S2, mixing the straw carbon material, conductive polymer monomer and water to obtain a mixed solution; electrochemically polymerizing and depositing the mixed solution under a three-electrode system, and drying the mixed solution to obtain a microbial fuel cell anode material.

[0011] Chinese Patent No. 202210424795.3 discloses a method for preparing a biocompatible microbial fuel cell composite anode material, comprising the following steps:

[0012] (1) Synthesis of polyaniline: 0.01 mol of aniline was added to 20 ml of toluene and stirred in an ice-water bath for 20 min; 2 g of a 10% aqueous solution of polyvinyl alcohol was added to 90 ml of a 1 mol / L hydrochloric acid solution; the hydrochloric acid solution containing polyvinyl alcohol and the toluene solution containing aniline were vigorously stirred and mixed in an ice-water bath; 0.01 mol of ammonium persulfate was dissolved in 10 ml of water at room temperature and then added dropwise to the above mixture, which was then allowed to react. Finally, the reaction product was rinsed with deionized water and anhydrous ethanol, filtered, and dried to obtain polyaniline;

[0013] (2) Preparation of polyaniline / reduced graphene oxide composite material: 0.06 g of graphene oxide was mixed with a certain amount of polyaniline, 20 ml of water was added, and ultrasonic dispersion was performed uniformly; a certain amount of ascorbic acid was added and stirred uniformly, and then reduction reaction was performed at 90°C for a certain time; after the reaction was completed, the product was taken out, vacuum dried and ground into powder to obtain a polyaniline / reduced graphene oxide composite material;

[0014] (3) Preparation of composite electrode material: 0.6 g of sodium alginate and 0.3-0.5 g of agar were added to 10 ml of water and completely dissolved, and then the agar solution was added to the sodium alginate solution, and then the prepared polyaniline / reduced graphene oxide composite material was added. After stirring evenly, the mixture was allowed to stand to remove bubbles. Subsequently, nickel foam was immersed in the mixture to evenly coat the mixture. After cooling, the mixture was immersed in a calcium chloride solution for cross-linking to obtain the biocompatible microbial fuel cell composite anode material.

[0015] The anode materials produced by the preparation methods in the above-mentioned patents and prior art have disadvantages such as weak electrocatalytic activity and low output power. Therefore, a method for preparing anodes modified with metal compounds was developed and designed to improve the power generation performance of microbial fuel cells by enhancing the bioelectrocatalytic efficiency of the anode surface. Summary of the invention:

[0016] The purpose of the present invention is to overcome the shortcomings of the existing technology and develop a method for preparing a metal compound modified anode, which can mass-produce anode materials that solve the shortcomings of weak electrocatalytic activity and low output power.

[0017] In order to achieve the above-mentioned purpose, the specific process of the metal compound modified anode preparation method of the present invention is as follows:

[0018] First, the substrate is placed in a mixed acid of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1, pretreated at 90°C for 1-3 hours, and then repeatedly washed with deionized water to obtain a pretreated substrate;

[0019] Pre-treating the substrate can ensure that the metal compound precursor grows evenly on the surface of the substrate, and the substrate includes carbon cloth and carbon felt;

[0020] Then, 1-5 parts by mass of ammonium molybdate and / or 1-5 parts by mass of ammonium tungstate and 1-10 parts by mass of dopamine hydrochloride are dissolved in 50 mL-1 L of deionized water to form a soaking solution;

[0021] Secondly, the pretreated substrate is placed in the soaking solution and fully soaked for 0.5-2 hours, and the pH value of the soaking solution is adjusted to 3.0-6.0 by using ammonia water with a molar concentration of 3-12 mol / L. After being kept at room temperature for 4-24 hours, it is taken out, repeatedly washed with deionized water, and dried to obtain a substrate with a metal compound precursor grown thereon;

[0022] Dopamine can self-polymerize on the surface of the substrate to form a polydopamine coating, and the catechol group and other functional groups of dopamine can complex MoO4 2- WO4 2- According to the characteristics of the substrate, after adjusting the pH of the immersion solution to 3.0-6.0, dopamine undergoes a slow self-polymerization reaction to form a metal compound precursor on the substrate surface;

[0023] The surface of the metal compound precursor is a petal-like morphology formed by a large number of nanosheets interwoven and stacked, with a large specific surface area. The main body of the metal compound precursor is spherical particles, evenly distributed on the surface of the substrate, and has very good electrocatalytic activity.

[0024] Repeating this step can adjust the loading amount of the metal compound precursor on the substrate;

[0025] Finally, the substrate on which the metal compound precursor is grown is placed in an inert or reducing gas atmosphere and calcined at a temperature of 500-800° C. for 2-6 hours to obtain a metal compound modified anode.

[0026] Compared with the existing technology, the present invention, on the one hand, adopts the chemical in situ polymerization method to grow the metal compound precursor on the surface of the substrate, avoiding the use of organic binders such as polytetrafluoroethylene; on the other hand, compared with conventional electrochemical deposition, hydrothermal synthesis and other methods, it can achieve the purpose of large-scale and batch preparation of metal compound modified anodes; at the same time, the metal compound has a large specific surface area, which can provide a large number of attachment sites for electricity-producing microorganisms, which is conducive to the enrichment and growth of electrochemically active biofilms, greatly improving the electrocatalytic activity of the anode, accelerating the charge transfer efficiency between the electrochemical biofilm and the electrode interface, and significantly improving the power generation performance of the microbial fuel cell. Specific implementation method:

[0027] The present invention will be further described below by way of examples.

[0028] Example 1:

[0029] The specific process of the metal compound modified anode preparation method involved in this embodiment is as follows:

[0030] The carbon cloth or carbon felt is placed in a mixed acid, pretreated at 90° C. for 1-3 hours, and then repeatedly washed with deionized water to obtain a pretreated carbon cloth or carbon felt;

[0031] Dissolve ammonium molybdate, ammonium tungstate and dopamine hydrochloride in deionized water to form a soaking solution;

[0032] After the pretreated carbon cloth or carbon felt is fully soaked in the soaking solution, the pH value of the soaking solution is adjusted by adding ammonia water, and after keeping it at room temperature for 4-24 hours, it is taken out, repeatedly washed with deionized water, and dried to obtain the carbon cloth or carbon felt with the metal compound precursor grown thereon;

[0033] The carbon cloth or carbon felt grown with the metal compound precursor is placed in an argon atmosphere and calcined to obtain a molybdenum-tungsten bimetallic compound modified anode.

[0034] Example 2:

[0035] The specific process of the metal compound modified anode preparation method involved in this embodiment is as follows:

[0036] The carbon cloth or carbon felt is pretreated in a mixed acid and then repeatedly washed with deionized water to obtain a pretreated carbon cloth or carbon felt;

[0037] Dissolve ammonium molybdate, ammonium tungstate and dopamine hydrochloride in deionized water to form a soaking solution;

[0038] After the pretreated carbon cloth or carbon felt is fully soaked in the soaking solution, the pH value of the soaking solution is adjusted by adding ammonia water, and after keeping it at room temperature for 4-24 hours, it is taken out, repeatedly washed with deionized water, and dried to obtain the carbon cloth or carbon felt with the metal compound precursor grown thereon;

[0039] The carbon cloth or carbon felt grown with the metal compound precursor is placed in a reducing atmosphere including hydrogen and calcined to obtain a molybdenum-tungsten bimetallic compound modified anode.

[0040] Example 3:

[0041] The specific process of the metal compound modified anode preparation method involved in this embodiment is as follows:

[0042] Pre-treating the carbon cloth or carbon felt;

[0043] Dissolve ammonium molybdate and dopamine hydrochloride in deionized water to form a soaking solution;

[0044] After the pretreated carbon cloth or carbon felt is fully soaked in the soaking solution, the pH value of the soaking solution is adjusted by adding ammonia water, and after keeping it at room temperature for 4-24 hours, it is taken out, repeatedly washed with deionized water, and dried to obtain the carbon cloth or carbon felt with the metal compound precursor grown thereon;

[0045] The carbon cloth or carbon felt grown with the metal compound precursor is placed in an argon atmosphere and calcined to obtain a molybdenum-based metal compound modified anode.

[0046] Example 4:

[0047] The specific process of the metal compound modified anode preparation method involved in this embodiment is as follows:

[0048] Pre-treating the carbon cloth or carbon felt;

[0049] Dissolve ammonium molybdate and dopamine hydrochloride in deionized water to form a soaking solution;

[0050] After the pretreated carbon cloth or carbon felt is fully soaked in the soaking solution, the pH value of the soaking solution is adjusted by adding ammonia water, and after keeping it at room temperature for 4-24 hours, it is taken out, repeatedly washed with deionized water, and dried to obtain the carbon cloth or carbon felt with the metal compound precursor grown thereon;

[0051] The carbon cloth or carbon felt grown with the metal compound precursor is placed in a hydrogen atmosphere and calcined to obtain a molybdenum-based metal compound modified anode.

[0052] Example 5:

[0053] The specific process of the metal compound modified anode preparation method involved in this embodiment is as follows:

[0054] Pre-treating the carbon cloth or carbon felt;

[0055] Dissolve ammonium tungstate and dopamine hydrochloride in deionized water to form a soaking solution;

[0056] After the pretreated carbon cloth or carbon felt is fully soaked in the soaking solution, the pH value of the soaking solution is adjusted by adding ammonia water, and after keeping it at room temperature for 4-24 hours, it is taken out, repeatedly washed with deionized water, and dried to obtain the carbon cloth or carbon felt with the metal compound precursor grown thereon;

[0057] The carbon cloth or carbon felt grown with the metal compound precursor is placed in an argon atmosphere and calcined to obtain a tungsten-based metal compound modified anode.

[0058] Example 6:

[0059] The specific process of the metal compound modified anode preparation method involved in this embodiment is as follows:

[0060] Pre-treating the carbon cloth or carbon felt;

[0061] Dissolve ammonium tungstate and dopamine hydrochloride in deionized water to form a soaking solution;

[0062] After the pretreated carbon cloth or carbon felt is fully soaked in the soaking solution, the pH value of the soaking solution is adjusted by adding ammonia water, and after keeping it at room temperature for 4-24 hours, it is taken out, repeatedly washed with deionized water, and dried to obtain the carbon cloth or carbon felt with the metal compound precursor grown thereon;

[0063] The carbon cloth or carbon felt grown with the metal compound precursor is placed in a hydrogen atmosphere and calcined to obtain a tungsten-based metal compound modified anode.

[0064] Example 7:

[0065] The specific process of the metal compound modified anode preparation method involved in this embodiment is as follows:

[0066] First, the carbon cloth was placed in a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1 at 90°C for 2 hours and then repeatedly washed with deionized water to obtain a pretreated carbon cloth.

[0067] Then, 100 mg of ammonium molybdate, 100 mg of ammonium tungstate, and 200 mg of dopamine hydrochloride were dissolved in 70 mL of deionized water to form a soaking solution;

[0068] Secondly, the pretreated carbon cloth was immersed in the soaking solution for 1 hour, and the pH value of the soaking solution was adjusted to 4.5 by adding 6 mol / L ammonia water. After keeping it at room temperature for 12 hours, it was taken out, repeatedly washed with deionized water, and dried to obtain a carbon cloth with a metal compound precursor.

[0069] Finally, the carbon grown with the metal compound precursor was placed in a hydrogen atmosphere and calcined at 800°C for 4 hours to obtain a molybdenum-tungsten bimetallic compound modified carbon cloth anode.

[0070] The performance test process of the molybdenum-tungsten bimetallic carbide modified carbon cloth anode prepared in this embodiment is as follows:

[0071] Microbial fuel cells were assembled using molybdenum-tungsten bimetallic carbide modified carbon cloth anode and carbon cloth anode respectively;

[0072] A data acquisition system was used to record the output voltage of the microbial fuel cell when connected to a 1000Ω resistor. The results showed that the stable output voltage of the microbial fuel cell with a molybdenum-tungsten bimetallic carbide-modified carbon cloth anode was nearly 25% higher than that of the microbial fuel cell with a carbon cloth anode.

[0073] The power density curve of the microbial fuel cell was measured and plotted using the constant resistance discharge method. The results showed that the maximum power density of the microbial fuel cell with molybdenum-tungsten bimetallic carbide modified carbon cloth anode was 3000mW / m 2 , which is three times the maximum output power of the carbon cloth anode microbial fuel cell.

Claims

1. A method for preparing a metal compound modified anode, characterized in that: The specific process is: The substrate is placed in a mixed acid for pretreatment and then repeatedly washed with deionized water to obtain a pretreated substrate; Dissolve ammonium molybdate, ammonium tungstate and dopamine hydrochloride in deionized water to form a soaking solution; the amount of ammonium molybdate or ammonium tungstate is 1-5 parts by mass, and the amount of dopamine hydrochloride is 1-10 parts by mass; The pretreated substrate is placed in a soaking solution, and the pH value of the soaking solution is adjusted to 3.0-6.0 by adding ammonia water. After keeping it at room temperature for 4-24 hours, it is taken out, repeatedly washed with deionized water, and dried to obtain a substrate with a metal compound precursor grown thereon; this step is repeated to adjust the loading amount of the metal compound precursor on the substrate; placing the substrate on which the metal compound precursor is grown in a gas atmosphere and calcining it to obtain a metal compound modified anode; Among them, the catechol functional groups of dopamine complexed with MoO4 2- and WO4 2- , a self-polymerization reaction occurs to form a metal compound precursor on the surface of the substrate; The surface of the metal compound precursor has a petal-like morphology formed by interweaving and stacking nanosheets.

2. The method for preparing a metal compound modified anode according to claim 1, wherein: The matrix includes carbon cloth and carbon felt.

3. The method for preparing a metal compound modified anode according to claim 1, wherein: The process of substrate pretreatment is: The substrate was placed in a mixed acid formed by concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1, pretreated at 90°C for 1-3 hours, and then repeatedly washed with deionized water.

4. The method for preparing a metal compound modified anode according to claim 1, wherein: Deionized water is 50mL-1L.

5. The method for preparing a metal compound modified anode according to claim 1, wherein: The soaking time is 0.5-2h, and the molar concentration of the ammonia water is 3-12mol / L.

6. The method for preparing a metal compound modified anode according to claim 1 or 5, characterized in that: Dopamine self-polymerizes on the substrate surface to form a polydopamine coating.

7. The method for preparing a metal compound modified anode according to claim 6, characterized in that: The main body of the metal compound precursor is in the form of spherical particles and is evenly distributed on the surface of the substrate.

8. The method for preparing a metal compound modified anode according to claim 1, characterized in that: The calcination is carried out in an inert or reducing gas atmosphere at a calcination temperature of 500-800°C.