Catalytic layer, method of preparation and microbial fuel cell

Abstract

The present application relates to the technical field of bioelectrochemistry, and discloses a catalytic layer, a preparation method and a microbial fuel cell, wherein acetylene black and F@SiO2 catalyst are mixed, then deionized water is added drop by drop to obtain a solution one; a perfluorosulfonic acid type polymer solution and pure isopropyl alcohol solution are added to the solution one and stirred uniformly to obtain a suspension; the suspension is coated on carbon cloth to form a coating layer on the carbon cloth, and the coating layer is dried to obtain the catalytic layer; compared with noble metal platinum and noble metal compounds, the F@SiO2 catalyst is a good oxygen reduction reaction catalyst because it has a wide source of raw materials and a low price.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bio-electrochemistry, and particularly to a catalytic layer, a preparation method and a microbial fuel cell. BACKGROUND

[0002] Energy and environmental problems have become two of the ten serious problems faced by mankind in the next 50 years, and are the main challenges faced by mankind in the 21st century. Human beings are in the process of sustainable development and global industrialization, and the demand and consumption of energy are increasing year by year. The environmental and ecological problems caused by energy utilization are also deteriorating, and it is urgent to accelerate the green and low-carbon transformation of energy. As a new type of microbial electrochemical technology, microbial fuel cells can produce electricity while degrading organic matter, and have the characteristics of cleanliness, energy saving and economy, and have become a research hotspot in the field of wastewater treatment, and are expected to improve energy and environmental problems.

[0003] In the anaerobic environment of the anode chamber of a microbial fuel cell (MFC), organic matter is catalytically degraded by microorganisms to produce electrons and protons. The electrons are transmitted to the cathode through an external circuit, and the protons are transmitted to the cathode chamber through a proton exchange membrane. The protons, O2 and electrons are reduced to form H2O in the aerobic environment of the cathode. MFCs can produce electricity while degrading various pollutants, do not need to intake energy from the outside world, and do not cause secondary pollution. The operating conditions are mild, and the MFCs have the characteristics of economy and cleanliness, and have broad application value.

[0004] Silicon dioxide is widely used in the field of electrochemistry due to its abundant reserves, low cost, good thermal stability, high specific surface area and other characteristics, and is often used as a MFC cathode material. In the process of preparing silicon dioxide, hydrogen fluoride solution is often used to etch silicon dioxide. After etching is completed, the material needs to be washed and baked, and the hydrogen fluoride solution is very toxic. Therefore, this method is relatively cumbersome, not green and environmentally friendly, and has safety hazards. In order to explore a more convenient, green and safe preparation method of MFC cathode catalyst, the present application provides a catalytic layer, a preparation method and a microbial fuel cell. SUMMARY

[0005] (I) Technical problems solved

[0006] In view of the deficiencies in the prior art, the present application provides a catalytic layer, a preparation method and a microbial fuel cell, which solves the above problems.

[0007] (II) Technical solutions

[0008] To achieve the above-mentioned purposes, the application provides the following technical scheme: a catalytic layer, comprising acetylene black, F@SiO2 catalyst, deionized water, perfluorosulfonic acid type polymer and pure isopropyl alcohol;

[0009] The mass ratio of acetylene black to the F@SiO2 catalyst is (3-5):1;

[0010] The mass ratio of deionized water to the F@SiO2 catalyst is (10-15):1;

[0011] The mass ratio of the F@SiO2 catalyst to the perfluorosulfonic acid type polymer and pure isopropyl alcohol is 1:(30-35):(25-30).

[0012] Preferably, the concentration of the perfluorosulfonic acid type polymer is 3%-5%, and the concentration of the pure isopropyl alcohol is 95%-99%.

[0013] A preparation method of a catalytic layer, comprising the following steps:

[0014] Step 1: mixing acetylene black and F@SiO2 catalyst, then adding deionized water drop by drop to obtain solution I;

[0015] Step 2: adding a perfluorosulfonic acid type polymer solution and a pure isopropyl alcohol solution to solution I, stirring uniformly to obtain a suspension;

[0016] Step 3: coating the suspension on carbon cloth to form a coating layer, drying to obtain a catalytic layer.

[0017] Preferably, the thickness of the coating layer is 0.3-0.5 mm.

[0018] Preferably, the drying time in step 3 is at least 24 h.

[0019] Preferably, the preparation method of the F@SiO2 catalyst in step 1 comprises the following steps:

[0020] S1: mixing ammonia water, ethanol, pure water and tetraethyl orthosilicate uniformly to obtain a first mixed solution;

[0021] S2: placing the first mixed solution at room temperature to react to obtain a clear transparent solution;

[0022] S3: mixing dopamine hydrochloride and pure water to obtain a second mixed solution, adding the second mixed solution to the clear transparent solution to react at room temperature to obtain a dark brown solution;

[0023] S4: washing the dark brown solution with pure water, centrifuging, and heating and drying to obtain a dark purple solid.

[0024] S5: the deep brown purple solid is subjected to first high-temperature calcination treatment to obtain a black solid, and the black solid is subjected to second high-temperature calcination treatment with ammonium fluoride solid to obtain the F@SiO2 catalyst.

[0025] Preferably, the mass ratio between the ammonia water, ethanol, pure water and tetraethyl orthosilicate in S1 is (1-3):(47-49):(159-161):1.

[0026] Preferably, the mass ratio between the dopamine hydrochloride and pure water in S3 is 1:20, and the mass ratio between the clear transparent solution and the pure water in the second mixed solution is 10:1.

[0027] Preferably, the heating and drying treatment condition in S4 is drying in a vacuum oven at 50-70 DEG C for 12-36 h.

[0028] Preferably, the first high-temperature calcination treatment condition in S5 is high-temperature calcination at 1000 DEG C under nitrogen atmosphere, and the second high-temperature calcination treatment condition is high-temperature calcination at 800-1000 DEG C.

[0029] A catalytic layer microbial fuel cell comprises a diffusion layer, a carbon-based layer, a carbon cloth layer and a catalytic layer with a thickness of 0.4-0.5 mm.

[0030] (III) Beneficial Effects

[0031] Compared with the prior art, the catalytic layer, the preparation method and the microbial fuel cell have the following beneficial effects:

[0032] 1. The catalytic layer, the preparation method and the microbial fuel cell use F@SiO2 catalyst as raw material, and compared with noble metal platinum and noble metal compounds, the F@SiO2 catalyst has a wide source of raw material and low price, and is a good oxygen reduction reaction catalyst.

[0033] 2. The catalytic layer, the preparation method and the microbial fuel cell use ammonium fluoride to gasify and etch silica beads to achieve doping, and compared with etching silica beads by using strong acid or strong base which is dangerous and not environmentally friendly, the preparation method is more green and clean, and reduces environmental hazards.

[0034] 3. The catalytic layer, the preparation method and the microbial fuel cell, the prepared catalytic layer is applied to the microbial fuel cell, which is not only green and environmentally friendly, but also can improve the stability of the microbial fuel cell, reduce the operation cost and improve the cathode electron transfer rate. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 A structure schematic view of a catalytic layer cathode provided by the microbial fuel cell according to the embodiment of the application.

[0036] Figure 2 Electrochemical linear polarization curve graphs for different materials;

[0037] Figure 3 Cyclic voltammetry graphs for different materials;

[0038] Figure 4 Pore size distribution graphs for different materials;

[0039] Figure 5 N2 adsorption and desorption graphs for different materials;

[0040] Figure 6 Initial potential, half-wave potential, and limiting current / density parameters of different materials in alkaline and neutral media, respectively. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work are within the protection scope of the present application.

[0042] Please refer to Figures 1-6 The embodiment of the present application provides a preparation method of a catalytic layer, which comprises the following steps:

[0043] The acetylene black and the F@SiO2 catalyst are mixed, and then deionized water is added drop by drop; then, a Nafion solution and an isopropanol solution are added, and stirring is uniformly performed to obtain a suspension; the suspension is coated on a carbon cloth to form a coating layer on the carbon cloth, and drying is performed to obtain the catalytic layer.

[0044] The preparation method of the F@SiO2 catalyst comprises the following steps:

[0045] The ammonia water with a volume fraction of 25%, ethanol, pure water, and tetraethyl orthosilicate are mixed to obtain a first mixed solution; the first mixed solution is placed at an ambient temperature to react, and a clear and transparent solution is obtained;

[0046] The dopamine hydrochloride and the pure water are mixed to obtain a clear and transparent solution, which is a second mixed solution; the second mixed solution is added to the first mixed solution to react at an ambient temperature, and a dark brown solution is obtained;

[0047] The deep brown solution is washed with pure water, centrifuged, and dried at 50-70°C to obtain a deep brown-violet solid; the deep brown-violet solid is calcined at 1000°C to obtain a black solid; the black solid is calcined with ammonium fluoride at 800-1000°C to obtain the F@SiO2 catalyst.

[0048] The preparation method of the catalytic layer comprises:

[0049] The acetylene black and the F@SiO2 catalyst are mixed, with the mass ratio of acetylene black to F@SiO2 catalyst being (3-5):1; then deionized water is added dropwise, with the mass ratio of added deionized water to F@SiO2 catalyst being (10-15):1; then a Nafion solution with a concentration of 3-5% and an isopropyl alcohol solution with a concentration of 95-99% are added, and the order of addition of the Nafion solution and the isopropyl alcohol solution is not limited, wherein the mass ratio of F@SiO2 catalyst to Nafion solution to isopropyl alcohol solution is 1:(30-35):(25-30), and the mixture is stirred uniformly to obtain a suspension; the suspension is coated on the carbon cloth to form a coating layer with a thickness of 0.3-0.5 mm on the carbon cloth, and the coating layer is dried to obtain the catalytic layer.

[0050] The preparation method of the F@SiO2 catalyst comprises the following steps:

[0051] (1) Ammonia water, ethanol, pure water, and tetraethyl orthosilicate are mixed, with the mass ratio of the four being (1-3):(47-49):(159-161):1, and preferably 2:48:160:1, to obtain a first mixed solution; in a preferred embodiment, the ammonia water, ethanol, and pure water are mixed in proportion, and then stirred magnetically at an ambient temperature of 25°C for 30 min, and then the tetraethyl orthosilicate is added in proportion and stirred magnetically for 15 min to obtain the first mixed solution;

[0052] (2) Dopamine hydrochloride and pure water are mixed to obtain a clear and transparent solution as a second mixed solution; the second mixed solution is added to the first mixed solution and reacted at room temperature of 25°C, with a preferred reaction time of 24 h, to obtain a deep brown solution;

[0053] (3) The deep brown solution is washed with pure water, centrifuged and filtered five times to obtain a precipitate, with a centrifugal speed of 7000-9000 r / min, and preferably 8000 r / min, and a centrifugal time of 5-10 min; the precipitate is dried, specifically in a vacuum drying oven, with a working temperature of 50-70°C, and preferably 60°C, and a drying time of 12-36 h, and preferably 24 h, to obtain a deep brown-violet solid;

[0054] (4) placing the deep brown purple solid in a tube furnace for high temperature calcination at 1000℃, wherein the reaction condition is 5℃ / min, and the reaction time is 1h-3h, preferably 2h, to obtain a black solid;

[0055] (5) mixing the black solid with ammonium fluoride solid at a mass ratio of 1:(15-25), preferably 1:20, and placing the mixed solid in a tube furnace for high temperature calcination at 800℃-1000℃, preferably 900℃, wherein the reaction condition is 5℃ / min, and the reaction time is 1h-3h, preferably 2h, to obtain the F@SiO2 catalyst. Specifically, the catalyst obtained by mixing the black solid with ammonium fluoride solid at a reaction temperature of 800℃, 900℃, and 1000℃ for high temperature calcination is respectively recorded as F@SiO2-800℃ catalyst, F@SiO2-900℃ catalyst, and F@SiO2-1000℃ catalyst.

[0056] More specifically, the preparation method of the catalytic layer in the embodiment of the present application comprises:

[0057] S1, placing acetylene black and F@SiO2 catalyst in a dosing container at a mass ratio of (3-5):1, and adding deionized water to the dosing container at a mass ratio of 1:(11-12) with respect to the F@SiO2 catalyst; specifically, placing the acetylene black on a weighing paper, then placing the weighed F@SiO2 catalyst on the weighing paper, and mixing the acetylene black and F@SiO2 catalyst uniformly; further, dropping deionized water into the dosing container containing the acetylene black and F@SiO2 catalyst; it should be noted that when the deionized water is dropped into the dosing container, it should be dropped one drop at a time to make the acetylene black and F@SiO2 catalyst and the deionized water mix more uniformly, and no stirring is required when the deionized water is dropped.

[0058] S2, adding the 5% Nafion solution and the 99% isopropyl alcohol solution with a mass ratio of 1:(31-32):(26-27) to the F@SiO2 catalyst in the ingredient container and stirring uniformly, and the adding sequence of the Nafion solution and the isopropyl alcohol solution is not limited, obtaining a suspension; specifically, first adding the 5% Nafion solution with a mass ratio of 1:(31-32) to the F@SiO2 catalyst in the ingredient container, and then adding the 99% isopropyl alcohol solution with a mass ratio of 1:(26-27) to the F@SiO2 catalyst in the ingredient container; then sealing the F@SiO2 catalyst (as a powder), the 5% Nafion solution and the 99% isopropyl alcohol solution (as solvents) in the ingredient container and placing on a vibrator to obtain a centrifugal force stirring by the vibrator, and the rotating speed of the vibrator is not greater than 250 revolutions per second when the ingredient container is on the vibrator, so that the solution and the powder in the ingredient container are fully mixed, thereby obtaining a uniformly mixed suspension.

[0059] In the embodiment of the application, the density of the 5% Nafion solution is 0.92-0.94 g / ml, and the density of the 99% isopropyl alcohol solution is 0.785 g / ml. Specifically, the mass ratio of acetylene black, the F@SiO2 catalyst, deionized water, the 5% Nafion solution and the 99% isopropyl alcohol solution is in grams.

[0060] S3, coating the suspension on the carbon cloth to form a coating layer with a thickness of 0.3-0.5 mm, and obtaining a catalytic layer after drying the carbon cloth with the coating layer for at least 24 h. It should be noted that the suspension should be coated on one side of the carbon cloth as much as possible.

[0061] Further, after coating the suspension on the carbon cloth, drying is needed, and generally, a hair dryer is needed to dry the carbon cloth. In the embodiment of the application, since the carbon cloth is coated with the suspension, in order to prevent the structure of the carbon cloth and the suspension from being damaged due to high temperature during drying, preferably, the hair dryer uses cold air, or when hot air is used, the distance between the carbon cloth and the air outlet of the hair dryer is greater than 70-100 cm, and a partition is arranged between the carbon cloth and the air outlet of the hair dryer, so that the structure of the carbon cloth and the suspension is prevented from being damaged due to high temperature.

[0062] In actual application, the carbon cloth coated with the suspension is dried for at least 24 h, and the catalytic layer is obtained after the carbon cloth is dried for 24 h, and the catalytic layer is an F@SiO2 catalytic layer.

[0063] The present application is to load the catalytic layer containing F@SiO2 catalyst on carbon cloth, and then apply the catalytic layer to a microbial fuel cell to obtain a cathode of the microbial fuel cell loaded with F@SiO2 carbon cloth. Figure 1 As shown in Figure 1, the structure of the cathode of the microbial fuel cell loaded with F@SiO2 catalyst provided by the present application is shown, which includes a diffusion layer, a carbon-based layer 1-3, a carbon cloth layer 1-2 and a catalytic layer 1-1. The thickness of the catalytic layer provided by the present application is between 0.4-0.5 mm.

[0064] The following will be described in detail in combination with specific examples.

[0065] Example 1

[0066] 0.0442g of SiO2 catalyst and 0.1768g of acetylene black were placed in a batching container, deionized water with a mass ratio of 1:11.5 to the SiO2 catalyst was added dropwise into the batching container, and then 5% Nafion solution and pure isopropyl alcohol solution with a mass ratio of 1:31.5:26.5 to the SiO2 catalyst were sequentially added and stirred to obtain a suspension; the suspension was coated on the carbon cloth to form a coating layer with a thickness of 0.4mm on the carbon cloth, and the carbon cloth with the coating layer was dried for at least 24h to obtain a catalytic layer.

[0067] Example 2

[0068] 0.0442g of F@SiO2-800 catalyst and 0.1768g of acetylene black were placed in a batching container, deionized water with a mass ratio of 1:11.5 to the F@SiO2-800 catalyst was added dropwise into the batching container, and then 5% Nafion solution and pure isopropyl alcohol solution with a mass ratio of 1:31.5:26.5 to the F@SiO2-800 catalyst were sequentially added and stirred to obtain a suspension; the suspension was coated on the carbon cloth to form a coating layer with a thickness of 0.4mm on the carbon cloth, and the carbon cloth with the coating layer was dried for at least 24h to obtain a catalytic layer.

[0069] Example 3

[0070] 0.0442g of F@SiO2-900 catalyst and 0.1768g of acetylene black were placed in a batching container, deionized water with a mass ratio of 1:11.5 to the F@SiO2-900 catalyst was added dropwise into the batching container, and then 5% Nafion solution and pure isopropyl alcohol solution with a mass ratio of 1:31.5:26.5 to the F@SiO2-900 catalyst were sequentially added and stirred to obtain a suspension; the suspension was coated on the carbon cloth to form a coating layer with a thickness of 0.4mm on the carbon cloth, and the carbon cloth with the coating layer was dried for at least 24h to obtain a catalytic layer.

[0071] Example 4

[0072] 0.0442 g of F@SiO2-1000 catalyst and 0.1768 g of acetylene black were placed into a dosing container, deionized water in a mass ratio of 1:11.5 to the F@SiO2-1000 catalyst was added dropwise into the dosing container, and then 5% Nafion solution and pure isopropyl alcohol solution in a mass ratio of 1:31.5:26.5 to the F@SiO2-1000 catalyst were added in sequence and stirred to obtain a suspension; the suspension was coated onto a carbon cloth, a coating layer with a thickness of 0.4 mm was formed on the carbon cloth, and after the carbon cloth with the coating layer was dried for at least 24 h, a catalytic layer was obtained.

[0073] Performance test

[0074] Figure 2 The oxygen reduction peak potential can be observed from the cyclic voltammogram, and the oxygen reduction activity of the catalyst can be understood, that is, the greater the peak value, the smaller the overpotential, the easier the reaction occurs, and the better the performance of the catalyst. The oxygen reduction peak potentials of Examples 1-4 were 0.41, 0.43, 0.57, and 0.49 V, respectively, and it can be seen that the catalyst obtained in Example 3 had the best performance.

[0075] Figure 3 Table 1 respectively shows the electrochemical linear polarization curves of different materials and the corresponding three important parameters of the initial potential, half-wave potential, and limiting current density, and it can be seen that after ammonium fluoride pyrolysis, the removal of silicon dioxide and the doping of fluorine greatly improve the performance of the material. Compared with the catalyst obtained in Example 1, the performance of Examples 2-4 is obviously better, and it can be seen that the electrochemical performance of Example 3 is the best among the other examples. Figure 4 、 Figure 5 The pore size distribution and N2 adsorption / desorption graphs of different materials, respectively, and the porosity and specific surface area are important factors affecting the electrocatalytic oxygen reduction performance of the catalyst. It can be seen from the graph that the curves of Examples 1-4 exhibit type IV isotherms with hysteresis loops, indicating that the material has a hierarchical porous structure with both micropores and mesopores, which is beneficial to the transmission of substances between the three-phase interface, exposes more active sites, and further promotes the occurrence of oxygen reduction reaction. Among them, Example 3 has the best effect.

[0076] From the above data, it can be seen that the best material is the catalyst obtained in Example 3. The catalyst obtained in Example 3 was used as a cathode catalyst in a microbial fuel cell, and its voltage was tested. Figure 6 is the output voltage graph when the catalyst obtained in Example 3 and Pt / C are used as MFC cathode catalysts, respectively. From Figure 6It can be seen that the average voltage of the Pt / C material is about 0.383 V, the average voltage of the catalyst obtained in Example 3 is about 0.583 V, and the maximum voltage can reach 0.652 V, which is much greater than the voltage of the Pt / C material. The above shows that the catalyst obtained in the example of the application can replace the Pt / C material as a catalyst and be loaded on the cathode to be applied in the microbial fuel cell.

[0077] Table 1. Initial potential, half-wave potential and limiting current density parameters of the catalysts obtained in Examples 1-4 in neutral medium

[0078]

[0079] Although the embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A catalytic layer, characterized by, acetylene black, catalyst, deionized water, perfluorosulfonic acid type polymer and pure isopropanol; The mass ratio of acetylene black to the catalyst is (3-5):1; The mass ratio of deionized water to the catalyst is (10-15):1; The mass ratio of catalyst to the perfluorosulfonic acid type polymer and pure isopropanol is 1:(30-35):(25-30). The preparation method of the catalyst comprises the following steps: S1: uniformly mixing ammonia water, ethanol, pure water and tetraethyl orthosilicate to obtain a first mixed solution; S2: placing the first mixed solution at room temperature to react to obtain a clear transparent solution; S3: mixing dopamine hydrochloride and pure water to obtain a second mixed solution, adding the second mixed solution into the clear transparent solution to react at room temperature to obtain a dark brown solution; S4: washing the dark brown solution with pure water, centrifuging, and drying to obtain a dark brown purple solid; S5: performing first high-temperature calcination treatment on the dark brown purple solid to obtain a black solid, and performing second high-temperature calcination treatment on the black solid and ammonium fluoride solid to obtain a catalyst; the first high-temperature calcination treatment is performed at 1000℃ under a nitrogen atmosphere, and the second high-temperature calcination treatment is performed at 800-1000℃; the mass ratio of the black solid to the ammonium fluoride solid is 1:(15-25).

2. The catalytic layer according to claim 1, characterized in that The concentration of the perfluorosulfonic acid type polymer is 3-5%, and the concentration of the pure isopropanol is 95-99%.

3. The method of claim 1, wherein the catalyst layer is prepared by the steps of: The method comprises the following steps: First step: mixing acetylene black and catalyst, and then adding deionized water drop by drop to obtain solution one; Second step: adding a perfluorosulfonic acid type polymer solution and a pure isopropanol solution into solution one, and stirring to obtain a suspension; Third step: coating the suspension on a carbon cloth to form a coating layer, and drying to obtain a catalytic layer.

4. The method of claim 3, wherein the catalyst layer is prepared by the steps of: The drying time in the third step is at least 24h, and the thickness of the coating layer is 0.3-0.5mm.

5. The method of claim 1, wherein the catalyst layer is prepared by the steps of: The mass ratio of ammonia water, ethanol, pure water and tetraethyl orthosilicate in S1 is (1-3):(47-49):(159-161):

1.

6. The method of claim 1, wherein the catalyst layer is prepared by the steps of: The mass ratio of dopamine hydrochloride to pure water in S3 is 1:20, and the mass ratio of the clear transparent solution to pure water in the second mixed solution is 10:

1.

7. The method of claim 1, wherein the catalyst layer is prepared by the steps of: The drying treatment condition in S4 is drying in a vacuum oven at 50-70℃ for 12-36h.

8. A catalyzed layer microbial fuel cell characterized by, The catalyst layer comprises a diffusion layer, a carbon-based layer, a carbon cloth layer and the catalytic layer of claim 1, and the thickness of the catalytic layer is 0.4-0.5mm.

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