A method for improving the wettability of the anode microporous layer of a micro direct methanol fuel cell

Abstract

The application discloses a method for improving the wettability of an anode microporous layer of a micro direct methanol fuel cell, which comprises the following steps: brushing a CNFP / Ag microporous layer slurry on carbon paper as an anode microporous layer, sintering in a tubular furnace with flowing nitrogen to obtain an anode microporous layer AMPL prepared by CNFP / Ag, and preparing a micro direct methanol fuel cell by using the anode microporous layer AMPL. 2 The brushing thickness of the CNFP / Ag microporous layer slurry is 0.008-0.015 mm, or 1 cm 2 The weight of the carbon paper is increased by 0.12-0.25 mg before and after brushing. The anode microporous layer (AMPL) is prepared by using a chemical deposition method, the application has lower charge transfer resistance and mass transfer resistance, and higher surface roughness and catalyst active sites, so that the overall power density of the battery is improved.

Description

Technical Field

[0001] This invention relates to the anode microporous layer of a micro direct methanol fuel cell, and more particularly to a method for improving the wettability of the anode microporous layer of a micro direct methanol fuel cell. Background Technology

[0002] Micro direct methanol fuel cells (μDMFCs) are miniaturized fuel cells that use methanol as fuel. With technological advancements and cost reductions, μDMFCs are expected to become the primary power source for future microelectronic devices. The core of a μDMFC is the membrane electrode assembly (MEA)—composed of an anode electrode, a cathode electrode, and a proton exchange membrane (PEM). The anode and cathode electrodes consist of a gas diffusion layer (GDL) and a catalyst layer (CL). The GDLs of the anode and cathode typically consist of two layers: a support layer (BL) and a microporous layer (MPL) with smaller pore sizes. The MPL plays a crucial role in improving catalyst activity and stability, controlling the mass transfer of reactants and products to the catalyst layer and providing adsorbable active sites for the catalyst. Therefore, improving the MPL is key to μDMFC technology.

[0003] The existing μDMFC has the disadvantage of low methanol mass transfer resistance and few catalyst attachment sites, resulting in low battery power density. The main purpose of this invention is to improve the wettability of the anode microporous layer. By depositing Ag nano-silver ions on the anode microporous layer prepared by carbon nanofiber powder (CNFP) and carbon powder, the resistance of methanol solution mass transfer process is increased, and the catalyst attachment sites are also increased, thereby improving the overall power density of the battery. Summary of the Invention

[0004] To address the shortcomings of existing technologies, such as low methanol mass transfer resistance and few catalyst attachment sites, which result in low battery power density, this invention provides a method to improve the wettability of the anode microporous layer in a micro direct methanol fuel cell. This invention employs a chemical deposition method to deposit Ag nanoparticles onto an MPL prepared from carbon nanofiber powder (CNFP) and carbon powder, serving as a novel MPL for μDMFCs. This increases the resistance to the methanol solution mass transfer process and also gives the prepared catalyst support better electrochemical performance, thereby improving the overall power density of the battery.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A method for improving the wettability of the anode microporous layer of a micro direct methanol fuel cell, wherein a CNFP / Ag microporous layer slurry is brushed onto carbon paper as an anode microporous layer, and sintered in a tube furnace with flowing nitrogen to obtain a CNFP / Ag anode microporous layer AMPL, and a micro direct methanol fuel cell is prepared using the anode microporous layer AMPL.

[0006] Preferably, the coating thickness of the CNFP / Ag microporous layer slurry is 0.008-0.015 mm, or 1 cm thick. 2 Based on carbon paper calculations, the weight gain before and after brushing is 0.12-0.25 mg.

[0007] Preferably, when sintering in a tube furnace, the sintering temperature is 300-400℃ and the sintering time is 1.5-4h.

[0008] Preferably, the CNFP / Ag microporous layer slurry is prepared as follows:

[0009] Step (1) Take the sensitized CNFP and put it into Tollen's reagent and stir to fully mix the CNFP suspension. Use glyoxal and triethanolamine solution as reducing agents and add the reducing agents dropwise to react and obtain CNFP / Ag suspension.

[0010] Step (2) The CNFP / Ag suspension was washed multiple times with deionized water using a Buchner funnel and then dried to obtain CNFP / Ag powder;

[0011] Step (3) Add PTFE solution and ethylene glycol to CNFP / Ag powder, disperse by ultrasonication and stir to obtain CNFP / Ag microporous layer slurry.

[0012] As a preferred option, when preparing the CNFP suspension in step (1), the mass-to-volume ratio of the sensitized CNFP to Tollen's reagent is 1:10-30, and the mixing time is 20-50 min.

[0013] As a preferred option, when preparing the CNFP / Ag suspension in step (1), the reducing agent should be added dropwise to the CNFP suspension at a temperature of 1300-1600 rad / min and 35-45°C.

[0014] Preferably, the preparation process of the reducing agent in step (1) is as follows:

[0015] Take a clean test tube, add 0.5-0.7 ml of 35-45% glyoxal and 1.5-2.5 ml of triethanolamine, then add 18-22 ml of deionized water, stir thoroughly, and place in an ultrasonic oscillator to vibrate for 3-8 minutes as a reducing agent; the reducing agent has a good reduction effect.

[0016] The volume ratio of the reducing agent to the CNFP / Ag suspension is 0.8-1.2:0.8-1.2.

[0017] Preferably, when washing the CNFP / Ag suspension with a Buchner funnel in step (2), the vacuum degree is 0.6-0.8 MPa, and after washing, it needs to be dried at 60-70℃ for 20-30 hours.

[0018] Preferably, in step (3), when preparing the CNFP / Ag microporous layer slurry, it is necessary to ultrasonically disperse and stir for 2-3 hours, with an ultrasonic power of 35-45KHz; the mass-volume ratio of the CNFP / Ag powder to the PTFE solution and ethylene glycol is 0.8-1.2:0.8-1.2:8-15.

[0019] Preferably, the sensitization process of the CNFP is as follows: the CNFP is immersed in a SnCl2 solution with a concentration of 0.03-0.05M for sensitization treatment for 3-10 seconds, then washed with deionized water and dried for later use.

[0020] This invention involves depositing Ag nanoparticles onto carbon nanofiber powder (CNFP) and carbon powder-based MPL (Metal-Plastic Composite). The Ag nanoparticles are uniformly attached to the novel MPL obtained through chemical vapor deposition (CVD), and the process is simple to operate. CVD can achieve a smooth deposition surface. This is because CVD is performed at high saturation, resulting in a high nucleation rate and density, with uniform distribution across the entire plane, thus producing a macroscopically smooth surface. Simultaneously, in CVD, the mean free path of molecules (atoms) is relatively large, leading to a more uniform spatial distribution of molecules, which is beneficial for forming a smooth deposition surface.

[0021] This invention employs a chemical deposition method to prepare a novel MPL for μDMFC by depositing Ag nanoparticles onto carbon nanofiber powder (CNFP) and carbon powder-based MPL, thereby improving the overall power density of the battery. The wettability modification and the effect of increased roughness on μDMFC performance were analyzed by measuring the contact angle and observing the MPL surface roughness using scanning electron microscopy (SEM). Experimental results show that the CNFP / Ag MPL, due to the increased silver microparticles on its surface, appropriately increases the resistance to the mass transfer process in the methanol solution, resulting in a catalyst support with better electrochemical performance. This provides the catalyst with more adsorption anchors than ordinary carbon nanofiber powder (CB) for the subsequent catalyst layer spraying process. In comparison, the improvement of the novel MPL increases the maximum power density of the battery from 25.6 mW·cm⁻¹. -2 Increased to 32.0 mW·cm -2 The current was increased by 25%. At the same time, due to the increased mass transfer barrier capability, the maximum operating current of CNFP / Ag-μDMFC was better than that of CB-μDMFC at all concentrations.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses chemical deposition to deposit Ag nanoparticles on carbon nanofiber powder (CNFP) and MPL prepared by carbon powder as a novel MPL for μDMFC, which increases the resistance of the mass transfer process of methanol solution and also makes the prepared catalyst support have better electrochemical performance, thereby improving the overall power density of the battery. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of μDMFC;

[0024] Figure 2 A schematic diagram comparing the membrane structures of CB-μDMFC and CNFP / Ag-μDMFC;

[0025] Figure 3 Comparison of surface morphology of anodic microporous layers (AMPL) prepared for CB and CNFP / Ag using scanning electron microscopy.

[0026] Figure 4 Polarization curves of CB-μDMFC and CNFP / Ag-μDMFC at different concentrations;

[0027] Figure 5 Linear scan images of LSV tests of batteries in methanol solutions of different concentrations (1M, 2M, 3M). Detailed Implementation

[0028] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited to the following technical solutions.

[0029] Example 1

[0030] Weigh an appropriate amount of CNFP (TXJS-T700, Toray), immerse it in 0.04M SnCl2 for sensitization treatment for 5 seconds, then wash it with deionized water and dry it for later use.

[0031] Tollen's reagent is obtained by adding 0.01M ammonia solution dropwise to a 0.1M AgNO3 solution until the precipitate just disappears.

[0032] Take 1g of sensitized CNFP and put it into 20mL of Lollen's reagent and stir for 30min to thoroughly mix the CNFP suspension. Dissolve 0.6mL of glyoxal ((CHO)2, 40%) and 2mL of triethanolamine (N(CH2CH2OH)3) in 20mL of deionized water as a reducing agent. Gradually add the reducing agent dropwise at 1300rad / min and 308K until all the reducing agent is used to obtain the CNFP / Ag suspension.

[0033] The CNFP / Ag suspension was washed multiple times with deionized water using a Buchner funnel at 0.7 MPa, and then dried at 60 °C for 24 h to obtain CNFP / Ag powder.

[0034] 0.1 mL of PTFE solution and 1.2 mL of (CH2OH)2 were added to 0.096 g of CNFP / Ag powder. After ultrasonic dispersion, the mixture was stirred for 2 hours to obtain a CNFP / Ag microporous layer slurry. The slurry was then brushed onto a carbon paper with an area of ​​1.2 cm × 1.2 cm as an anode microporous layer (AMPL). The paper was then placed in a tube furnace with flowing nitrogen and sintered at 340 °C for 2 hours to obtain the anode microporous layer (AMPL) prepared by CNFP / Ag. The brushing process was the same as the existing technology and the carbon powder brushing process. The weight difference between the anode microporous layer after brushing and the anode microporous layer before brushing was at least 0.2 mg. The brushing thickness was estimated to be 0.008-0.015 mm.

[0035] The surface morphology comparison images of the anodic microporous layer (AMPL) prepared by CNFP / Ag powder and the anodic microporous layer (AMPL) prepared by ordinary CB are shown in the following figure. Figure 3 As shown.

[0036] Figures (a), (c), and (e) show SEM images of CB at 100×, 5000×, and 10000× magnification, while figures (b), (d), and (f) show SEM images of CNFP / Ag at 100×, 5000×, and 10000× magnification. As the magnification increases, the microporous structure of the MPL surface becomes apparent; these micropores serve as channels for gas and liquid flow. In the CNFP / Ag SEM images, the green areas represent carbon nanofiber powder, and the red areas represent chemically deposited silver on the MPL surface. Comparing the SEM images of CB and CNFP / Ag reveals that the addition of carbon nanofibers to the CNFP / Ag MPL alters the overall MPL surface morphology, embedding nanofiber lines into the otherwise flat CB-MPL surface. Simultaneously, the chemical deposition of silver causes the carbon nanofibers and carbon powder surface to adhere to silver nanoparticles with the same pore size as the CB, forming a CNFP / Ag composite MPL. The carbon nanofiber powder used in this invention has good electrical conductivity. After being coated with appropriate silver microparticles, it partially blocks the micropores formed by CB particles, appropriately increasing the resistance to the mass transfer process of methanol solution. However, the high activity and good conductivity of the silver microparticles themselves result in a catalyst support with good electrochemical performance. The MPL treated with chemically deposited silver has a more significant surface roughness compared to CB-MPL, which provides more adsorption anchors for the catalyst in the subsequent catalyst layer spraying process than ordinary CB.

[0037] Example 2

[0038] wettability and surface roughness of the microporous layer of the μDMFC anode electrode

[0039] The μDMFC consists of a cathode end plate 1, a cathode current collector 2, a membrane electrode assembly 3, an anode current collector 4, an anode end plate 5, a cathode diffusion layer 6, a conventional CB microporous layer 7, a cathode catalytic layer 8, a proton exchange membrane 9, an anode catalytic layer 10, a modified CNFP / Ag microporous layer 13, and an anode diffusion layer 12. Figure 1 As shown.

[0040] The membrane electrode assembly of μDMFC is described in detail by comparing the membrane electrodes of CB-μDMFC and CNFP / Ag-μDMF before and after improvement. The CB-μDMFC membrane electrode includes a cathode diffusion layer 6, a conventional cathode CB microporous layer 7, a cathode catalyst layer 8, a proton exchange membrane 9, an anode catalyst layer 10, a conventional anode CB microporous layer 11, and an anode diffusion layer 12. The difference between the CNFP / Ag-μDMF membrane electrode and the CB-μDMFC membrane electrode is that the improved anode CNFP / Ag microporous layer 13 replaces the conventional anode CB microporous layer 11. Figure 2 As shown.

[0041] Both the cathode and anode current collectors are made of 304 stainless steel with an opening ratio of 38.5% and a thickness of 1 mm. Under normal operating conditions of μDMFC, the influence of the wettability and surface roughness of the microporous layer of the μDMFC anode electrode on the battery power is analyzed to find a method to improve the performance of μDMFC.

[0042] Under steady-state conditions, the contact angle on the MPL surface is related to the droplet radius, and the diffusion coefficient of the droplet on the MPL surface is related to temperature, solution viscosity, and droplet radius.

[0043]

[0044] In equation (1), D is the diffusion coefficient, K is the Boltzmann constant, T is the absolute temperature, η is the solution viscosity, and R is the droplet radius.

[0045] There is a standard correlation between droplet radius and contact angle, and the relationship equation is as follows:

[0046]

[0047] In equation (2), ΔP is the pressure difference between the inside and outside of the droplet, γ is the surface tension of the liquid, R is the radius of curvature of the droplet, and θ is the contact angle between the droplet and the solid surface.

[0048] In a passive DMFC, the mass transfer of methanol from the reservoir through the microporous layer to the anode catalyst layer is primarily diffusion-based. Therefore, the flux of methanol to the anode catalyst layer can be expressed as:

[0049]

[0050] In equation (3), J CH3OH It is the diffusion flux of methanol, D CH3OH It is the diffusion coefficient, C CH3OH X is the concentration of methanol. MPL It is a diffusion path.

[0051] Combining equation (2), we can obtain:

[0052]

[0053] The contact angle of CB is 151.85°, and the contact angle of CNFP / Ag is 105.8°, which results in a high diffusion coefficient D of the methanol solution on the MPL surface. CNFP / Ag Greater than D CB According to equation (4), it can be concluded that J CH3OH and J CNFP / Ag The diffusion flux of methanol is improved. Therefore, using CNFP / Ag with a smaller contact angle as the MPL can improve the diffusion coefficient of methanol, which helps to improve the overall reaction efficiency of μDMFC. At the same time, the good conductivity of CNFP / Ag will also reduce the overall resistance of the battery and increase the power density of μDMFC.

[0054] μDMFC test system

[0055] The testing system consists of a DC electronic load, an electrochemical workstation, and a constant temperature chamber. This system is primarily used for testing the EIS, discharge, and polarization curves of μDMFCs. Before testing, the μDMFCs are activated to achieve maximum power density. During testing, the temperature of the constant temperature chamber is set to 25°C. The μDMFCs are then placed in the chamber, with the positive and negative electrodes of the DC electronic load connected to the cathode and anode of the μDMFC, respectively. The electrochemical workstation is connected to the μDMFC according to the specific testing requirements.

[0056] Results and Analysis

[0057] polarization curve

[0058] The polarization curves of CP-μDMFC and CNFP / Ag-μDMFC at different concentrations are shown below. Figure 3 As shown. To investigate the effect of CNFP / Ag on the power density of μDMFC, 1.5 mL of methanol solutions of different concentrations (0.5 M-3.5 M) were injected sequentially into the fuel cells of CP-μDMFC and CNFP / Ag-μDMFC test batteries at 343 K, allowing the batteries to start from 0 and accelerate at 5 mA·cm⁻¹. -2 The current gradient is increased gradually until the voltage drops to 0, and the polarization curve of voltage as a function of current is recorded.

[0059] Table 1. Maximum power densities of CB-μDMFC and CNFP / Ag-μDMFC at different methanol concentrations.

[0060]

[0061] Combination Figure 3 (a) and Table 1 show that the CB-μDMFC achieves its maximum power density of 25.6 W·cm³ at 1 MHz. -2 .from Figure 3 (b) It can be seen that the CNFP / Ag-μDMFC achieves a maximum power density of 32.0 mW·cm³ at 1.5 MHz. -2 Compared to CB-μDMFC, it improved both the optimal methanol concentration and the maximum power density. The optimal methanol concentration increased from 1M to 1.5M, possibly because the presence of carbon nanofibers and Ag blocked the original pore structure of CB, reducing porosity and increasing the ability to block methanol mass transfer during battery operation. Results showed that the addition of CNFP and Ag improved the surface roughness of the electrode material and the number of catalyst-accessible active sites. Simultaneously, the addition of Ag reduced the internal resistance of the battery, increasing the overall power density, with the maximum power density increasing from 25.6 W·cm⁻¹. -2 Increased to 32.0 mW·cm -2 This represents a 25% improvement. Furthermore, due to the increased mass transfer barrier capability, the maximum operating current of CNFP / Ag-μDMFC is superior to that of CB-μDMFC at all concentrations.

[0062] Linear scan

[0063] The battery was linearly scanned from 0V to 1.8V at a scan rate of 50mV / s. The scan results are as follows. Figure 4 As shown. To further investigate the effect of CNFP / Ag as the MPL on methanol cross-linking, methanol solutions of different concentrations (1M, 2M, and 3M) were sequentially injected into the fuel cell chamber of the battery under test at 343K for LSV measurements to determine the degree of methanol cross-linking from the anode to the cathode. The cross-linking current density generated by methanol was characterized by its penetration from the anode to the cathode. It can be seen that the cross-linking current density increases with increasing methanol concentration. The cross-linking current densities of CB-μDMFC and CNFP / Ag-μDMFC are shown in the figure. Figure 4As shown in the figure. The results indicate that using CNFP / Ag as the MPL can significantly reduce methanol cross-linking at a concentration of 1M, with a difference of 21.98% between methanol cross-linking current densities. As the concentration increases, the difference between methanol cross-linking current densities gradually decreases by 9.0%. When the methanol concentration increases to 2M, the difference increases to 15.90%. When the methanol concentration increases to 3M, the difference increases to 17.81%. Considering measurement errors, the ability to suppress methanol cross-linking under 2M and 3M conditions is approximately the same. The results show that reducing the anode contact angle improves the ability of CNFP / Ag as the MPL to block methanol mass transfer, thus mitigating methanol cross-linking and increasing the methanol concentration at optimal power from 1M to 1.5M. This also has a certain correlation with the improvement of battery performance at various concentrations.

[0064] In summary, this invention modifies the anode microporous layer to reduce the internal resistance and improve the overall power density of the battery. This is achieved by introducing a hydrophilic anode MPL (Ampere Plasma Layer) of deposited Ag in carbon nanofiber powder (CNFP) onto the anode side of the DMFC. Under room temperature conditions, the EIS, electrochemical impedance spectroscopy, and fitting curves of CB-μDMFC and CNFP / Ag-μDMFC were tested and analyzed. Polarization curves, linear sweeps, and galvanostatic discharge curves at different methanol concentrations were also performed. The conclusions are as follows.

[0065] 1. Compared to CB-μDMFC, CNFP / Ag-μDMFC exhibits essentially the same contact impedance, but reduced high-frequency ohmic resistance, charge transfer resistance during the anodic reaction, and mass transfer resistance. This is attributed to the altered wettability of the anode microporous layer in CNFP / Ag, which optimizes electrolyte transport and CO2 emission channels, increases the electrolyte diffusion rate during mass transfer, and reduces mass transfer resistance. Simultaneously, it ensures uniform distribution of methanol molecules on the MEA membrane surface during diffusion to the anode, improving the flow path between the gas and liquid phases and reducing the difficulty of the reaction.

[0066] 2. The CB-μDMFC achieves its maximum power density of 25.6 W·cm³ at 1 MHz. -2 The CNFP / Ag-μDMFC achieved a maximum power density of 32.0 mW·cm³ at 1.5 MHz. -2 Compared to CB-μDMFC, it achieves improvements in both optimal methanol concentration and maximum power density, with the optimal methanol concentration increasing from 1M to 1.5M. This is attributed to the improved surface roughness of the electrode material and the increased number of catalyst-accessible active sites resulting from the addition of CNFP and Ag. Simultaneously, the addition of Ag reduces the internal resistance of the battery, thereby increasing the overall power density, with the maximum power density increasing from 25.6 W·cm⁻¹. -2 Increased to 32.0 mW·cm -2This represents a 25% improvement. Furthermore, due to the increased mass transfer barrier capability, the maximum operating current of CNFP / Ag-μDMFC is superior to that of CB-μDMFC at all concentrations.

[0067] 3. Using CNFP / Ag as the MPL significantly reduces methanol cross-linking at 1M concentration, with a difference of 21.98% between methanol cross-linking current densities. As the concentration increases, the difference gradually decreases by 9.0%. When the methanol concentration increases to 2M, the difference increases to 15.90%. When the methanol concentration increases to 3M, the difference increases to 17.81%. Considering measurement error, the ability to suppress methanol cross-linking under 2M and 3M conditions is approximately the same. The results show that reducing the anode contact angle improves the ability of CNFP / Ag as the MPL to block methanol mass transfer, thus mitigating methanol cross-linking and increasing the methanol concentration at optimal power from 1M to 1.5M. This also has a certain correlation with the improvement of battery performance at various concentrations.

[0068] 4. The discharge time of CB-μDMFC is approximately 87 minutes, while that of CNFP / Ag-μDMFC is increased to 110 minutes, a 26.4% increase compared to CB-μDMFC. Simultaneously, at the same solution concentration and current density, CNFP / Ag-μDMFC also exhibits a higher voltage output than CB-μDMFC. This indicates that the improved CNFP / Ag-μDMFC offers higher power and a longer stable operating time.

[0069] The above description is merely one embodiment of the present invention. Any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the present invention should be included within the protection scope of the present invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for improving the wettability of the anode microporous layer in a micro direct methanol fuel cell, characterized in that, CNFP / Ag microporous layer slurry was brushed onto carbon paper as an anode microporous layer, and sintered in a tubular furnace with flowing nitrogen to obtain anode microporous layer AMPL prepared by CNFP / Ag. Micro direct methanol fuel cell was prepared using the anode microporous layer AMPL.

2. The method for improving the wettability of the anode microporous layer in a micro direct methanol fuel cell according to claim 1, characterized in that, The thickness of the CNFP / Ag microporous layer slurry applied by brushing is 0.008-0.015 mm, or in increments of 1 cm. 2 Based on carbon paper calculations, the weight gain before and after brushing is 0.12-0.25 mg.

3. The method for improving the wettability of the anode microporous layer in a micro direct methanol fuel cell according to claim 1, characterized in that, When sintering in a tube furnace, the sintering temperature is 300-400℃ and the sintering time is 1.5-4h.

4. The method for improving the wettability of the anode microporous layer in a micro direct methanol fuel cell according to claim 1, characterized in that, The preparation method of the CNFP / Ag microporous layer slurry is as follows: Step (1) Take the sensitized CNFP and put it into Tollen's reagent and stir to fully mix the CNFP suspension. Use glyoxal and triethanolamine solution as reducing agents and add the reducing agents dropwise to react and obtain CNFP / Ag suspension. Step (2) The CNFP / Ag suspension was washed multiple times with deionized water using a Buchner funnel and then dried to obtain CNFP / Ag powder; Step (3) Add PTFE solution and ethylene glycol to CNFP / Ag powder, disperse by ultrasonication and stir to obtain CNFP / Ag microporous layer slurry.

5. The method for improving the wettability of the anode microporous layer in a micro direct methanol fuel cell according to claim 4, characterized in that, When preparing the CNFP suspension in step (1), the mass-to-volume ratio of the sensitized CNFP to Tollen's reagent is 1:10-30, and the mixing time is 20-50 min.

6. The method for improving the wettability of the anode microporous layer in a micro direct methanol fuel cell according to claim 4, characterized in that, When preparing the CNFP / Ag suspension in step (1), the reducing agent needs to be added dropwise to the CNFP suspension at 1300-1600 rad / min and 35-45℃.

7. The method for improving the wettability of the anode microporous layer in a micro direct methanol fuel cell according to claim 4, characterized in that, The preparation process of the reducing agent in step (1) is as follows: Take a clean test tube, add 0.5-0.7 ml of 35-45% glyoxal and 1.5-2.5 ml of triethanolamine, then add 18-22 ml of deionized water, stir thoroughly, and place in an ultrasonic oscillator to vibrate for 3-8 minutes as a reducing agent; The volume ratio of the reducing agent to the CNFP / Ag suspension is 0.8-1.2:0.8-1.

2.

8. The method for improving the wettability of the anode microporous layer in a micro direct methanol fuel cell according to claim 4, characterized in that, When washing the CNFP / Ag suspension using a Buchner funnel in step (2), the vacuum degree is 0.6-0.8 MPa. After washing, it needs to be dried at 60-70℃ for 20-30 hours.

9. The method for improving the wettability of the anode microporous layer in a micro direct methanol fuel cell according to claim 4, characterized in that, When preparing the CNFP / Ag microporous layer slurry in step (3), it is necessary to ultrasonically disperse and stir for 2-3 hours with an ultrasonic power of 35-45KHz; the mass-volume ratio of the CNFP / Ag powder to the PTFE solution and ethylene glycol is 0.8-1.2:0.8-1.2:8-15.

10. The method for improving the wettability of the anode microporous layer in a micro direct methanol fuel cell according to claim 4, characterized in that, The sensitization process of CNFP is as follows: CNFP is immersed in a SnCl2 solution with a concentration of 0.03-0.05M for sensitization treatment for 3-10 seconds, then washed with deionized water and dried for later use.

Images