A ceramic proton exchange membrane for microbial fuel cells and a method of making the same

Abstract

This invention provides a ceramic proton exchange membrane for microbial fuel cells and its preparation method, comprising the following steps: mixing clay, an inorganic modifier, and an organic modifier to obtain a solid powder; the inorganic modifier is alumina and silicon dioxide, and the organic modifier is selected from one or more of wheat flour, biochar powder, straw powder, and bamboo powder; the solid powder is ball-milled, granulated, pressed into sheets, and calcined to obtain the ceramic proton exchange membrane. This invention addresses the problems of poor mass transfer performance and low power generation performance of traditional pure clay ceramic membranes. Using clay as the matrix material, and through specific inorganic and organic modifiers, the pore structure of the material is adjusted. A novel ceramic proton exchange membrane is then prepared through ball milling, granulation, pressing, and calcination. This membrane has low manufacturing cost, good proton transport efficiency, and extremely low internal resistance. When applied to microbial fuel cells, it can achieve higher output voltage and more stable power generation performance.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a ceramic proton exchange membrane for microbial fuel cells and its preparation method. Background Technology

[0002] Microbial fuel cells (MFCs) are bioelectrochemical systems that utilize microbial degradation of organic waste through electrochemical reactions. A typical two-chamber MFC consists of separate anode and cathode chambers separated by a proton exchange membrane. MFCs show promising applications in wastewater treatment and energy regeneration. Existing research has largely employed perfluorosulfonic acid (PFSA) membranes as proton exchange membranes in MFC assembly. However, PFSA membranes suffer from drawbacks such as high cost, poor mechanical strength, and severe membrane fouling, limiting the large-scale application and recyclability of MFCs.

[0003] Ceramic-based proton exchange membranes have become a major alternative to traditional proton exchange membranes due to their advantages such as easy composition control, low manufacturing cost, high mechanical strength, and environmental friendliness. Therefore, preparing ceramic membranes with high mass transfer performance is an important way to improve the power generation performance and cycle stability of microbial fuel cells, and reduce their operating costs. Summary of the Invention

[0004] Based on this, the present invention provides a method for preparing a ceramic proton exchange membrane with good mass transfer performance and high mechanical strength.

[0005] A method for preparing a ceramic proton exchange membrane for microbial fuel cells includes the following steps:

[0006] Clay, an inorganic modifier, and an organic modifier are mixed to obtain a solid powder; the inorganic modifier is alumina and silicon dioxide, and the organic modifier is selected from one or more of wheat flour, biochar powder, straw powder, and bamboo powder; the alumina accounts for 5% to 15% of the mass percentage of the solid powder, the silicon dioxide accounts for 5% to 15% of the mass percentage of the solid powder, and the organic modifier accounts for 5% to 15% of the mass percentage of the solid powder;

[0007] The solid powder is ball-milled, granulated, pressed into tablets, and calcined to obtain the ceramic proton exchange membrane.

[0008] In one embodiment, the alumina accounts for 9% to 11% of the mass percentage of the solid powder, the silicon dioxide accounts for 9% to 11% of the mass percentage of the solid powder, and the organic modifier accounts for 9% to 11% of the mass percentage of the solid powder.

[0009] In one embodiment, the ball milling includes the following steps: mixing the solid powder with a dispersant and ball milling at a speed of 200-400 r / min for 60-120 min.

[0010] Preferably, the dispersant is anhydrous ethanol, and the solid-liquid ratio of the solid powder to anhydrous ethanol is 0.5–2 g / mL. Preferably, the clay is natural clay.

[0011] In one embodiment, agate grinding balls of 2mm, 3mm and 5mm are added during the ball milling process, with a mass ratio of 12:3:1, and the direction of rotation is changed every 30 minutes at a set rotation speed.

[0012] In one embodiment, the granulation includes the following steps: drying the product after ball milling, then adding a binder for granulation, and sieving with a sieve to retain particles between 40 and 60 mesh.

[0013] Preferably, the adhesive is a 5 wt% polyvinyl alcohol aqueous solution, and the amount added is 0.5 to 1.5 mL of adhesive per 10 g of the solid powder. Preferably, the drying temperature is 65 to 75°C, and the drying time is 0.5 to 2 hours.

[0014] In one embodiment, the tableting includes the following steps: placing the granulated product into a mold and pressing it to obtain a rough preform film with a thickness of 3-6 mm.

[0015] Preferably, the mold is a cylindrical mold, and the diameter is selected according to the actual microbial fuel cell device.

[0016] In one embodiment, the tableting is performed using an oil-sealed tablet press, holding the pressure at 10–15 MPa for 3–15 minutes, and then slowly depressurizing.

[0017] In one embodiment, the calcination includes the following steps: calcining the tableted product under the following heating program: heating from room temperature to 100-106°C at a rate of 1-2°C / min and holding for 30-60 min; then heating to 500°C at a rate of 1-2°C / min and holding for 60-120 min; finally heating to 700-1000°C at a rate of 5-10°C / min and holding for 120-180 min. Preferably, the final heating is to 700-800°C at a rate of 5-10°C / min and holding for 120-180 min; more preferably, 750°C.

[0018] The present invention also provides a ceramic proton exchange membrane for microbial fuel cells, which is prepared according to the above preparation method.

[0019] The present invention also provides a microbial fuel cell, comprising an anode chamber, a cathode chamber, and the aforementioned ceramic proton exchange membrane.

[0020] The above-described solution of the present invention has the following beneficial effects:

[0021] This invention addresses the problems of poor mass transfer performance and low power generation performance of traditional pure clay ceramic membranes. Using clay as the matrix material, specific inorganic and organic modifiers are used to adjust the pore structure of the material. A novel ceramic proton exchange membrane is then prepared through ball milling, granulation, tableting, and calcination. Modification with alumina and silica enables the ceramic proton exchange membrane to have continuous proton transfer capacity. The organic modifier optimizes pore size and pore size distribution during high-temperature carbonization, thereby improving the water absorption performance and pore structure of the ceramic proton exchange membrane. Therefore, the ceramic proton exchange membrane prepared by this invention has low manufacturing cost, good proton transport efficiency, and extremely low internal resistance. It also exhibits good water absorption and porosity, as well as high mechanical strength. When applied to microbial fuel cells, it can replace traditional perfluorosulfonic acid membranes, achieving higher output voltage and lower transfer resistance, effectively improving the power generation performance of microbial fuel cells and facilitating their large-scale application. Attached Figure Description

[0022] Figure 1 The image shows the surface microstructure of the ceramic proton exchange membrane prepared in Example 1 of this invention.

[0023] Figure 2 This refers to the output voltage of the ceramic membrane microbial fuel cell in Embodiment 2 of the present invention;

[0024] Figure 3 The AC impedance spectrum of the ceramic membrane microbial fuel cell in Example 2 of this invention;

[0025] Figure 4 The power density and polarization curves of the ceramic membrane microbial fuel cell in Example 2 of this invention are shown. Detailed Implementation

[0026] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Unless otherwise specified, the reagents and instruments used in the embodiments are conventional choices in the art. Experimental methods not specifying specific conditions in the embodiments are implemented according to conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.

[0028] Example 1

[0029] The ceramic proton exchange membrane was prepared by the following method:

[0030] 1. Preparation of ceramic proton exchange membrane precursors

[0031] (a) Ball milling mixing

[0032] Weigh appropriate amounts of the target material, including natural clay, silica, alumina, and wheat flour, in a mass ratio of 7:1:1:1, and place them into an agate ball mill jar. Add anhydrous ethanol (1 mL per 1 g of solid) as a dispersion solvent at a solid-liquid ratio of 1:1, and add agate grinding balls in a ratio of 2 mm:3 mm:5 mm = 12:3:1. Set the milling speed to 400 r / min, changing the direction of rotation every 30 min, for a total milling time of 120 min.

[0033] (b) Grinding and granulation

[0034] The mixture obtained after ball milling is placed in an oven and dried at 70℃ for 60 minutes. The dried mixture powder is then granulated using a 5% polyvinyl alcohol solution as a binder. 1 mL of binder is added for every 10 g of raw material. The mixture is then ground and granulated in a mortar and sieved through a 40-60 mesh screen, retaining particles with a size between 40 and 60 mesh.

[0035] 2. Preparation of ceramic proton exchange membranes

[0036] (a) Tableting

[0037] Weigh 8g of particles with a size between 40 and 60 mesh and place them into a cylindrical mold with a diameter of Ф = 5mm. Use an oil-sealed tablet press to maintain pressure at 14MPa for 10 minutes, and then slowly release the pressure to obtain a 4mm rough film.

[0038] (b) High-temperature calcination

[0039] The preform membrane obtained by pressing is placed in a digitally controlled temperature muffle furnace. First, the temperature is increased to 106℃ at 2℃ / min and held for 30min to remove moisture. Then, the temperature is increased to 500℃ at 1℃ / min and held for 120min to remove plastic. Finally, the temperature is increased to 750℃ at 5℃ / min and held for 180min to calcine and shape the membrane, thus obtaining the finished ceramic proton exchange membrane.

[0040] Figure 1 This is a scanning electron microscope (SEM) image of the ceramic proton exchange membrane prepared in this embodiment. The microstructure shows a micrometer-scale pore distribution on the ceramic membrane surface, which enhances the membrane's porosity and water absorption capacity. Furthermore, increased porosity improves the contact rate between the silicon-aluminum groups and protons, thereby enhancing the proton transport capacity of the ceramic membrane. In this embodiment, the addition of wheat flour optimizes the pore structure of the ceramic membrane, and the addition of silicon-aluminum oxide enables the formation of more proton-adsorbing groups, thus optimizing the proton transport efficiency. Simultaneously, the addition of silicon-aluminum oxide also creates a complex spatial structure of stacked crystalline particles on the surface of the clay-based ceramic proton exchange membrane, which provides the ceramic membrane with stable mechanical strength.

[0041] Example 2: Construction of a dual-chamber microbial fuel cell

[0042] The clay-based ceramic proton exchange membrane prepared in Example 1 was applied to a dual-chamber microbial fuel cell. The specific structure of the constructed dual-chamber microbial fuel cell includes: (1) a 1000Ω resistor; (2) a wire; (3) a clay-based ceramic proton exchange membrane; and (4) a carbon felt electrode with dimensions of 3cm × 3cm (length × width). 10g of activated sludge and 120mL of simulated wastewater were placed in the anode chamber. The simulated wastewater consisted of: 0.2g / L ammonium chloride, 0.075g / L calcium chloride dihydrate, 0.33g / L potassium chloride, 0.30g / L sodium chloride, 0.315g / L magnesium chloride, 1.26g / L dipotassium hydrogen phosphate, 0.42g / L potassium dihydrogen phosphate, 1mL / L trace element solution, 1g / L yeast extract, and 3.29g / L sodium acetate. The cathode chamber is filled with a 50 mM PBS-potassium ferricyanide solution, composed of 0.13 g / L potassium chloride, 0.31 g / L ammonium chloride, 2.77 g / L sodium dihydrogen phosphate dihydrate, 11.54 g / L disodium hydrogen phosphate dodecahydrate, and 16.45 g / L potassium ferricyanide. The trace elements include Fe, Zn, Mn, Mo, Co, and Ni. A 1000 Ω resistor is connected to the external circuit of the dual-chamber microbial fuel cell, and the battery output voltage is recorded periodically to plot a voltage-time curve. Figure 2 To date, the dual-chamber microbial fuel cell has been operating stably for multiple cycles, with the highest operating voltage exceeding 600mV, demonstrating excellent power generation performance.

[0043] (1) Measurement of AC impedance of a two-chamber microbial fuel cell constructed with clay-based ceramic proton exchange membrane

[0044] Electrochemical performance tests were performed on the anode of the microbial fuel cell using a DH7000 electrochemical workstation from Donghua University. Electrochemical impedance spectroscopy (EIS) was conducted on the anode of the dual-chamber microbial fuel cell using a three-electrode system, with the anode as the working electrode, the cathode as the counter electrode, and a silver-silver chloride electrode as the reference electrode.

[0045] Figure 3 The AC impedance spectrum of the constructed dual-chamber microbial fuel cell is shown. Using ZView software and fuel cell equivalent circuit fitting calculations, the cell solution resistance was 1.5 Ω, the anode charge transfer resistance was 7.9 Ω, the cathode charge transfer resistance was 18.8 Ω, the cathode diffusion resistance was 104 Ω, and the total internal resistance was 132.2 Ω. Modifiers were used to fully adjust the pore structure of the ceramic membrane, giving it excellent mass transfer efficiency. Using the ceramic membrane as the proton exchange membrane in the microbial fuel cell results in lower resistance to proton transfer from the anode chamber to the cathode chamber, thereby enhancing the power generation performance of the microbial fuel cell.

[0046] (2) Polarization curve and power density

[0047] By varying the external resistance (9kΩ, 8kΩ, 7kΩ, 6kΩ, 5kΩ, 4kΩ, 3kΩ, 2kΩ, 1.8kΩ, 1.6kΩ, 1.4kΩ, 1.2kΩ, 1kΩ, 900Ω, 800Ω, 700Ω, 600Ω, 500Ω, 400Ω, 300Ω, 200Ω, 100Ω, 90Ω, 80Ω, 70Ω, 60Ω, 50Ω, 40Ω), the output voltage and current of the battery can be tested, resulting in a polarization curve and the calculation of the battery's power density. Figure 4 As shown, when a ceramic membrane is used as the proton exchange membrane, the maximum power density of the microbial fuel cell can reach 421.7 mW·m. -2 The corresponding current density is 765.3 mA·m. -2 It exhibits excellent electrochemical characteristics and power generation performance.

[0048] Example 3

[0049] In this embodiment, the wheat flour in Example 1 was replaced with biochar powder, straw powder, and bamboo powder, respectively, and the performance was tested in the manner of Example 2. The results are shown in the table below.

[0050] Group Fitting total internal resistance Maximum power density Corresponding current density Biochar powder 410.4Ω <![CDATA[170.2mW.m -2 ]]> <![CDATA[640.3mA.m -2 ]]> straw powder 705.6Ω <![CDATA[361.2mW.m -2 ]]> <![CDATA[708.3mA.m -2 ]]> bamboo powder 625.0Ω <![CDATA[372.5mW.m -2 ]]> <![CDATA[722.5mW.m -2 ]]>

[0051] Comparative Example 1

[0052] This comparative example is basically the same as Example 1, except that wheat flour is not added, and natural clay, silica and alumina are mixed in a mass ratio of 8:1:1.

[0053] Comparative Example 2

[0054] This comparative example is basically the same as Example 1, except that alumina is not added, and natural clay, silica and wheat flour are mixed in a mass ratio of 7:2:1.

[0055] Comparative Example 3

[0056] This comparative example is basically the same as Example 1, except that wheat flour is replaced with maltose powder, and natural clay, silica, alumina and maltose powder are mixed in a mass ratio of 7:1:1:1.

[0057] The total internal resistance, maximum power density, and maximum current density of the above comparative examples were tested in accordance with the method of Example 2. The results are shown in the table below. It can be seen that the microbial fuel cell prepared by the ceramic proton exchange membrane in Example 1 is significantly inferior.

[0058] Group Fitting total internal resistance Maximum power density Corresponding current density Comparative Example 1 1457Ω <![CDATA[316.0mW.m -2 ]]> <![CDATA[662.5mA.m -2 ]]> Comparative Example 2 362.2Ω <![CDATA[345.4mW.m -2 ]]> <![CDATA[692.3mA.m -2 ]]> Comparative Example 3 322.0Ω <![CDATA[151.1mW.m -2 ]]> <![CDATA[601.2mA.m -2 ]]>

[0059] Example 4: Optimization of the addition ratio of alumina and silica

[0060] As shown in the table below, the mass ratio of natural clay, silica, alumina, and wheat flour was adjusted, and then the total internal resistance, maximum power density, and maximum current density were tested as described in Example 2. It can be seen that the preferred addition ratio of alumina, silica, and wheat flour is about 10%.

[0061] The mass ratio of natural clay, silica, alumina, and wheat flour Fitting total internal resistance Maximum power density Corresponding current density 7：1：1：1 132.2Ω <![CDATA[421.7mW.m -2 ]]> <![CDATA[765.3mA.m -2 ]]> 7:0.5:1.5:1 182.1Ω <![CDATA[400.3mW.m -2 ]]> <![CDATA[735.2mA.m -2 ]]> 7:1.5:0.5:1 237.0Ω <![CDATA[362.7mW.m -2 ]]> <![CDATA[709.7mA.m -2 ]]>

[0062] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a ceramic proton exchange membrane for microbial fuel cells, characterized in that, Includes the following steps: Clay, an inorganic modifier, and an organic modifier are mixed to obtain a solid powder; the inorganic modifier is alumina and silicon dioxide, and the organic modifier is selected from one or more of wheat flour, biochar powder, straw powder, and bamboo powder; the alumina accounts for 5% to 15% of the mass percentage of the solid powder, the silicon dioxide accounts for 5% to 15% of the mass percentage of the solid powder, and the organic modifier accounts for 5% to 15% of the mass percentage of the solid powder; The solid powder is ball-milled, granulated, pressed into tablets, and calcined to obtain the ceramic proton exchange membrane.

2. The preparation method according to claim 1, characterized in that, The alumina accounts for 9% to 11% of the mass percentage of the solid powder, the silicon dioxide accounts for 9% to 11% of the mass percentage of the solid powder, and the organic modifier accounts for 9% to 11% of the mass percentage of the solid powder.

3. The preparation method according to claim 1, characterized in that, The ball milling includes the following steps: mixing the solid powder with a dispersant and ball milling at a speed of 200-400 r / min for 60-120 min; the dispersant is anhydrous ethanol, and the solid-liquid ratio of the solid powder to anhydrous ethanol is 0.5-2 g / mL.

4. The preparation method according to claim 3, characterized in that, During the ball milling process, 2mm, 3mm and 5mm agate grinding balls are added in a mass ratio of 12:3:1, and the direction of rotation is changed every 30 minutes at a set speed.

5. The preparation method according to claim 1, characterized in that, The granulation process includes the following steps: drying the product after ball milling, then adding a binder for granulation, and sieving through a sieve to retain particles between 40 and 60 mesh; the binder is a 5 wt% polyvinyl alcohol aqueous solution, and the amount added is 0.5 to 1.5 mL of binder per 10 g of the solid powder.

6. The preparation method according to claim 1, characterized in that, The tableting process includes the following steps: placing the granulated product into a mold and pressing it to obtain a rough preform film with a thickness of 3-6 mm.

7. The preparation method according to claim 6, characterized in that, The tableting is performed using an oil-sealed tablet press, maintaining pressure at 10–15 MPa for 3–15 minutes, and then slowly releasing the pressure.

8. The preparation method according to claim 1, characterized in that, The calcination includes the following steps: calcining the tableted product under the following heating program: heating from room temperature to 100-106°C at a rate of 1-2°C / min and holding for 30-60 min, then heating to 500°C at a rate of 1-2°C / min and holding for 60-120 min, and finally heating to 700-1000°C at a rate of 5-10°C / min and holding for 120-180 min.

9. A ceramic proton exchange membrane for use in microbial fuel cells, characterized in that, It is prepared according to any one of claims 1 to 8.

10. A microbial fuel cell, characterized in that, It includes an anode chamber, a cathode chamber, and the ceramic proton exchange membrane as described in claim 9.

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