Preparation method of phosphoric acid fuel cell electrode

Abstract

The invention relates to the technical field of fuel cell manufacturing, and discloses a preparation method of a phosphoric acid fuel cell electrode. The electrode is prepared from a hydrophobic carbon paper base material and slurry containing a modified graphene oxide thickening agent, a platinum-carbon catalyst and polytetrafluoroethylene. The preparation method comprises the following steps: collecting the weight of a base material in real time before coating and calculating a surface density deviation coefficient; during coating, feed-forward control is executed based on the coefficient, and the feeding flow or the lip gap is adjusted in real time through a permeation compensation algorithm so as to actively compensate the local difference of the liquid absorption amount of the base material; and after curing, correcting a path by utilizing visual positioning, and dynamically adjusting laser power based on local thickness data for finishing. By establishing a real-time feedforward control loop of the physical parameters of the base material and the coating process, the influence of the non-uniformity of the base material on the product quality is effectively eliminated, and meanwhile, the modified functional slurry and the precise post-treatment process are combined, so that the electrode internal resistance is reduced, and the integrity of the edge microstructure is ensured.

Description

Technical Field

[0001] This invention relates to the field of fuel cell manufacturing technology, specifically to a method for preparing a phosphoric acid fuel cell electrode. Background Technology

[0002] Phosphoric acid fuel cells, as a mature power generation technology, typically use a porous diffusion electrode, a core component, which is composed of a hydrophobic carbon paper or carbon cloth substrate and a catalytic functional layer. During the large-scale manufacturing of the electrode, ensuring consistent catalyst loading, reducing internal electrode resistance, and maintaining machining precision are key factors determining the performance and lifespan of the fuel cell stack.

[0003] In existing continuous coating production, coating equipment typically coats slurry according to a preset constant feed rate and cutter gap. However, the hydrophobic carbon paper or carbon cloth used as the substrate is a porous material, and its areal density and porosity objectively fluctuate between batches and even in different areas of the same roll due to its manufacturing process limitations. Traditional fixed-parameter coating methods cannot respond to local changes in the physical properties of the substrate. When the substrate porosity or basis weight changes, its liquid absorption capacity fluctuates accordingly, leading to deviations in the final electrode catalyst loading. This uneven loading not only increases the waste of precious metal platinum but also causes uneven voltage distribution among individual cells within the battery stack, affecting overall output performance.

[0004] Furthermore, to meet the rheological properties requirements of precision processes such as slot die coating, thickeners or rheology modifiers, such as sodium carboxymethyl cellulose or hydroxypropyl methyl cellulose, are typically added to the slurry formulation. These polymeric additives are mostly electrical insulators and tend to leave ash or form non-conductive carbides during the high-temperature sintering of the electrode. This blocks the electron transport channels within the catalyst layer, leading to an increase in the electrode's ohmic impedance. Simultaneously, high-concentration platinum-carbon catalyst particles are prone to agglomeration in the slurry. If the dispersion system lacks effective steric support, catalyst agglomeration reduces the effective reaction area at the three-phase interface, thereby limiting the electrochemical activity of the electrode.

[0005] In the post-processing stage of electrode preparation, laser cutting technology is typically used to slit and trim the cured roll-shaped electrodes. Due to the flexibility of the electrode material, slight stretching or misalignment can easily occur during long-distance roller-to-roll transport. Traditional mechanical stop positioning or simple photoelectric alignment methods cannot guarantee precise matching between the cutting path and the actual coating area, easily leading to dimensional deviations. On the other hand, because the preceding coating process cannot achieve absolute thickness uniformity, using a constant-power laser for cutting often presents a dilemma: in areas with thin coatings, excessive laser energy can cause severe edge carbonization, expanding the heat-affected zone and even damaging the substrate fibers; while in areas with thicker coatings, the same energy may not be enough to completely cut through, leading to difficulties in product separation or the formation of burrs, severely affecting the microstructural integrity of the electrode edges and the reliability of subsequent sealing. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing a phosphoric acid fuel cell electrode, which solves the technical problems in existing technologies, such as poor uniformity of catalyst loading due to fluctuations in the physical properties of hydrophobic carbon paper substrate, increased internal resistance of the electrode due to residues of traditional insulating thickeners, and the difficulty of balancing dimensional accuracy and edge micro-quality in conventional laser cutting processes.

[0007] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of the present invention provides a phosphoric acid fuel cell electrode, which is prepared from raw materials including a hydrophobic carbon paper substrate and a catalyst slurry.

[0008] The catalyst slurry comprises a solvent and solid components dispersed in the solvent, the solid components including a platinum-carbon catalyst, polytetrafluoroethylene (PTFE), and a modified thickener. The total solid content of the catalyst slurry is controlled between 15 wt% and 35 wt%; the dry weight ratio of the platinum-carbon catalyst to PTFE is 6:4 to 8:2; and the amount of the modified thickener added is 0.1% to 0.5% of the total weight of the catalyst slurry.

[0009] The modified thickener is methoxy polyethylene glycol amine-grafted graphene oxide. Its preparation method is as follows: The carboxyl groups on the surface of a graphene oxide dispersion are activated using 1-3-dimethylaminopropyl-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. Then, methoxy polyethylene glycol amine with a number-average molecular weight of 1000 to 5000 is added. The reaction is carried out at pH 8.0 and a temperature of 60°C. The product is obtained after dialysis and drying. This modified thickener utilizes the two-dimensional sheet structure of graphene oxide to regulate the rheological properties of the slurry and leverages the steric hindrance effect generated by grafting long-chain polymers to improve the catalyst dispersion stability. During heat treatment, the graphene oxide component is reduced to construct a conductive network, avoiding the increase in internal resistance caused by residual insulating thickener.

[0010] A second aspect of the present invention provides a method for preparing the phosphoric acid fuel cell electrode, the method comprising the following steps: Catalyst slurry preparation steps: The platinum-carbon catalyst, polytetrafluoroethylene dispersion, and modified thickener are dispersed in a solvent. After the components are mixed and premixed, high-shear dispersion is performed at a speed of 2000 rpm to 5000 rpm for 30 to 45 minutes, followed by vacuum degassing under negative pressure.

[0011] Substrate feeding and data acquisition steps: During the conveying of the hydrophobic carbon paper substrate, the real-time weight of the substrate is collected using an online weighing device. Based on the set reference areal density, the system calculates the real-time areal density of the substrate and further calculates the areal density deviation coefficient of the current substrate area.

[0012] Surface cleaning pretreatment steps: Clean and dry the substrate surface. Cleaning methods include: using deionized water atomized spray cleaning, followed by water removal by air knife and then entering the infrared drying zone. The temperature of the infrared drying zone is set to 95℃ to 105℃ to ensure that the moisture content of the substrate is below 0.1% before coating; or using an atmospheric pressure plasma cleaner to bombard the substrate with a mixture of argon and oxygen.

[0013] Adaptive dynamic coating process: The catalyst slurry is coated onto the substrate surface, while the control system performs feedforward control based on the previously calculated areal density deviation coefficient. The system sets a base flow rate and a penetration compensation coefficient, calculates the target flow rate using a penetration compensation algorithm, and adjusts the flow rate of the coating feed pump or the lip gap of the coating head in real time. When the real-time areal density of the substrate is lower than the reference areal density, the system increases the feed flow rate to compensate for the substrate difference. The penetration compensation coefficient ranges from 0.1 to 0.5. During coating, the lip gap of the coating head is set to 60 micrometers to 250 micrometers, and the wet film thickness is controlled to be 65 micrometers to 300 micrometers.

[0014] Gradient high-temperature curing step: The coated wet electrode is passed sequentially through a solvent evaporation zone, a surfactant removal zone, and a sintering curing zone. The temperature of the solvent evaporation zone is set to 80℃ to 120℃, the temperature of the surfactant removal zone is set to 240℃ to 280℃, and the temperature of the sintering curing zone is set to 330℃ to 360℃.

[0015] Laser trimming step: The cured electrode is cut using a laser. This step includes: identifying the marked points on the electrode using a vision system, extracting the actual coordinates using the Otsu algorithm and performing an affine transformation to generate a corrected cutting path; simultaneously, establishing a coupling mechanism between thickness and laser energy, acquiring local thickness data of the electrode during the cutting process, and increasing the laser power by 3% when the detected local thickness exceeds 5% of the average.

[0016] This invention provides a method for preparing a phosphoric acid fuel cell electrode. It has the following beneficial effects: 1. This invention establishes a feedforward control mechanism based on the real-time areal density of the substrate by introducing a substrate weight data acquisition and processing step before the coating process. This mechanism utilizes a penetration compensation algorithm to adjust the flow rate of the coating feed pump or the lip gap of the coating head in real time according to the local physical differences of the substrate, actively compensating for the differences in liquid absorption caused by fluctuations in the porosity and areal density of the hydrophobic carbon paper substrate. This dynamic adjustment method effectively eliminates the impact of batch-to-batch and batch-to-batch inhomogeneities on the final product, significantly improving the process capability index of catalyst loading and product consistency.

[0017] 2. This invention uses methoxylated polyethylene glycol amine-grafted graphene oxide as a modified thickener for the catalyst slurry. This thickener utilizes the two-dimensional sheet structure of graphene oxide to adjust the rheological properties of the slurry, making it suitable for slot coating processes; simultaneously, it utilizes the steric hindrance effect generated by the grafted long-chain polymers to suppress the agglomeration of platinum-carbon catalyst particles. Furthermore, during the high-temperature curing process of the electrode, the graphene oxide component is reduced to construct a conductive network, avoiding the problem of increased electrode internal resistance caused by the residue of traditional insulating thickeners, thus balancing coating processability and electrode electrochemical performance.

[0018] 3. This invention employs a combination of visual positioning and energy-linked adjustment in the laser finishing process. The actual marker coordinates are extracted by a vision system and subjected to affine transformation to correct the cutting path and eliminate deformation errors caused by the flexible electrode transfer. Simultaneously, a coupling mechanism between the local electrode thickness and laser power is established, dynamically adjusting the laser energy based on thickness data during the cutting process. This control method ensures complete cutting through thick coating areas while preventing edge carbonization or expansion of the heat-affected zone in thin coating areas due to excess energy, thus ensuring the integrity of the electrode edge microstructure. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see the appendix Figure 1 This invention provides a method for preparing a phosphoric acid fuel cell electrode.

[0022] raw material: The main raw materials and reagents used in the following examples and comparative examples are as follows: platinum-carbon catalyst (platinum loading 60 wt%, carbon support is high specific surface area carbon black); polytetrafluoroethylene concentrated dispersion (solid content 60 wt%, average particle size 0.22 μm, containing nonionic surfactant); carbon paper (thickness 190 μm, porosity 78%, treated with 5 wt% polytetrafluoroethylene hydrophobicity); graphene oxide powder (monolayer ratio greater than 99%, oxygen content 40 wt% to 50 wt%); methoxy polyethylene glycol amine (mPEG-NH2, linear homopolymer, Mn=2000); and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and N-hydroxysuccinimide (NHS) used to synthesize the modifier; the remaining solvents, isopropanol, ethylene glycol and deionized water, are commercially available analytical grade products.

[0023] Preparation example: Preparation Example 1: This preparation example provides a low molecular weight grafted graphene oxide modified thickener (PEG molecular weight 1000), comprising the following steps: 100 mg of graphene oxide powder is dispersed in 100 mL of deionized water and ultrasonically treated for 2 hours at a power of 400 W to obtain a dispersion with a concentration of 1 mg / mL. 150 mg of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 90 mg of N-hydroxysuccinimide (NHS) are added to the above dispersion, and the mixture is magnetically stirred at 25 °C for 1 hour to activate the carboxyl groups on the surface of the graphene oxide. Subsequently, 300 mg of methoxy polyethylene glycol amine (mPEG-NH2, Mn=1000) is added, and the pH of the reaction system is adjusted to 8.0 using sodium hydroxide solution. The reaction is continuously stirred in an oil bath at 60 °C for 24 hours. After the reaction was completed, the mixture was placed in a dialysis bag with a molecular weight cutoff (MWCO) of 3500 Da and dialyzed in deionized water for 72 hours, with the dialysate being changed every 8 hours to remove unreacted PEG and small molecule byproducts. The dialyzed product was freeze-dried to obtain modified thickener powder A.

[0024] Preparation Example 2: This preparation example provides a medium molecular weight grafted graphene oxide modified thickener (PEG molecular weight 2000), comprising the following steps: 100 mg of graphene oxide powder is dispersed in 100 mL of deionized water and ultrasonically treated for 2 hours at a power of 400 W to obtain a dispersion with a concentration of 1 mg / mL. 200 mg of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 120 mg of N-hydroxysuccinimide (NHS) are added to the above dispersion, and the mixture is activated by magnetic stirring at 25 °C for 1 hour. Subsequently, 500 mg of methoxy polyethylene glycol amine (mPEG-NH2, Mn=2000) is added, and the pH of the reaction system is adjusted to 8.0 using sodium hydroxide solution. The reaction is continuously stirred in an oil bath at 60 °C for 24 hours. After the reaction was completed, the mixture was placed in a dialysis bag with a molecular weight cutoff (MWCO) of 10,000 Da and dialyzed in deionized water for 72 hours, with the dialysate being changed every 8 hours to remove unreacted PEG and small molecule byproducts. The dialyzed product was freeze-dried to obtain modified thickener powder B.

[0025] Preparation Example 3: This preparation example provides a high molecular weight grafted graphene oxide modified thickener (PEG molecular weight 5000), comprising the following steps: 100 mg of graphene oxide powder is dispersed in 100 mL of deionized water and ultrasonically treated for 2 hours at a power of 400 W to obtain a dispersion with a concentration of 1 mg / mL. 250 mg of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 150 mg of N-hydroxysuccinimide (NHS) are added to the above dispersion, and the mixture is magnetically stirred and activated at 25 °C for 1 hour. Subsequently, 800 mg of methoxy polyethylene glycol amine (mPEG-NH2, Mn=5000) is added, and the pH of the reaction system is adjusted to 8.0 using sodium hydroxide solution. The reaction is continuously stirred in an oil bath at 60 °C for 24 hours. After the reaction was completed, the mixture was placed in a dialysis bag with a molecular weight cutoff (MWCO) of 14000 Da and dialyzed in deionized water for 72 hours, with the dialysate being changed every 8 hours to remove unreacted PEG and small molecule byproducts. The dialyzed product was freeze-dried to obtain modified thickener powder C.

[0026] Example: Example 1: This embodiment provides a method for fabricating a standard phosphoric acid fuel cell electrode based on feedforward control, suitable for medium-speed continuous production, including the following steps: (1) Catalyst slurry preparation: Deionized water and isopropanol were mixed at a volume ratio of 1:2 as the dispersion medium. Platinum-carbon catalyst (Pt loading 60wt%) was dispersed in the solvent, and polytetrafluoroethylene concentrated dispersion (Pt / C to PTFE mass ratio of 7:3 after conversion to solid dry weight) was slowly added dropwise, along with 0.3% of the modified thickener powder B obtained in Preparation Example 2, accounting for 0.3% of the total weight of the slurry. The total solid content of the slurry was controlled to be 20wt%. After mechanical stirring and premixing, the mixture was subjected to high shear dispersion at 3000 rpm for 40 minutes, followed by degassing under a vacuum of -0.09 MPa for 15 minutes to obtain a viscosity of Catalyst slurry.

[0027] (2) Substrate feeding and feedforward data acquisition: The feeding speed of the hydrophobic carbon paper substrate is controlled at 3.0 m / min. The weight of the substrate is collected in real time using an online micro-tension electronic balance, and the reference surface density ρref is set to 100 g / m2. The system calculates the surface density deviation coefficient k (k=ρreal / ρref) of the current substrate area in real time.

[0028] (3) Surface cleaning pretreatment: The substrate surface is cleaned by atomized spraying of deionized water at a pressure of 0.3MPa, then dewatered by air knife with a wind speed of 30m / s, and then enters an infrared drying zone with a length of 1.5m. The surface temperature is controlled at 95℃ to ensure that the moisture content of the substrate is less than 0.1% before coating.

[0029] (4) Adaptive dynamic coating: The slurry is pumped into the slit coating die head, and the lip gap of the coating head is set to 100 μm, and the gasket thickness is 80 μm. The control system performs feedforward control according to the deviation coefficient k in step (2), sets the base flow rate Qbase, and the dynamic flow rate calculation formula is Qtarget=Qbase×(1+0.3×(1 k)), where the permeation compensation coefficient α is set to 0.3. When the substrate is detected to be too thin (k<1), the pump speed is automatically increased to compensate for the liquid absorption. The wet film thickness is controlled to be approximately 110 μm, and the final dry film platinum loading is approximately 1.0 mg / cm2.

[0030] (5) Gradient high temperature curing: The coated electrode is passed through a three-zone oven in sequence: the first zone temperature is 100℃, and it is held for 3 minutes to evaporate the solvent; the second zone temperature is 260℃, and it is held for 5 minutes to remove the surfactant; the third zone temperature is 340℃, and it is held for 10 minutes to complete the PTFE sintering and curing.

[0031] (6) Load closed-loop test: After curing, measure the weight and thickness of the electrode again and calculate the actual load. If the load deviation at a single point exceeds ±5%, it is marked as a defective product.

[0032] (7) Laser trimming: A picosecond laser (wavelength 1064nm), power 20W, frequency 100kHz, and cutting speed 1000mm / s are used. Before cutting, the DXF file is accessed by recognizing the QR code through the vision system, and the actual coordinates of the marked points are extracted using the Otsu algorithm and affine transformation is performed to correct the path. At the same time, based on the thickness data fed back by the laser thickness gauge, when the local thickness exceeds the average by 5%, the laser power is automatically increased by 3% to ensure through-cutting.

[0033] Example 2: This embodiment provides a method for fabricating a high-load phosphoric acid fuel cell electrode based on feedforward control, suitable for low-speed precision production, including the following steps: (1) Catalyst slurry preparation: Deionized water and isopropanol were mixed at a volume ratio of 1:1. Platinum-carbon catalyst was dispersed in a solvent, and polytetrafluoroethylene concentrated dispersion (Pt / C to PTFE mass ratio of 8:2 to increase the catalytic activity ratio) was added, along with 0.5% of the modified thickener powder A obtained in Preparation Example 1, accounting for 0.5% of the total weight of the slurry. The total solid content was controlled at 35 wt% (high solid content formulation). The mixture was dispersed at 2000 rpm for 45 minutes and then degassed under vacuum for 20 minutes to obtain a catalyst slurry with a viscosity of 450 cP.

[0034] (2) Substrate feeding and feedforward data acquisition: The feeding speed of the carbon paper substrate is controlled at 1.0 m / min (low speed mode). The reference surface density ρref is set to 110 g / m2. The deviation coefficient k is calculated in real time.

[0035] (3) Surface cleaning pretreatment: A normal pressure plasma cleaner is used instead of water washing. The plasma generated by the argon / oxygen mixed gas is used to bombard the surface of the substrate. The power is set to 1000W and the treatment distance is 10mm to remove organic pollutants and moderately increase the surface energy.

[0036] (4) Adaptive dynamic coating: Set the coating head lip gap to 250 μm. Implement feedforward control and set the penetration compensation coefficient α to 0.5 (high sensitivity). The dynamic flow rate calculation formula is Qtarget = Qbase × (1 + 0.5 × (1 For thicker substrates, the flow rate was significantly adjusted to ensure consistent high loading. The wet film thickness was controlled at approximately 260 μm, and the final dry film platinum loading was approximately 4.5 mg / cm².

[0037] (5) Gradient high temperature curing: the first temperature zone is 80℃, and the temperature is held for 5 minutes (low temperature slow baking prevents the thick coating from cracking); the second temperature zone is 240℃, and the temperature is held for 8 minutes; the third temperature zone is 330℃, and the temperature is held for 15 minutes.

[0038] (6) Load closed-loop detection: Same as in Example 1, with the tolerance range set to ±3%.

[0039] (7) Laser finishing: A UV nanosecond laser (wavelength 355nm), power 10W, frequency 50kHz, and cutting speed 500mm / s are used. The visual alignment logic is the same as in Example 1, with a focus on positive compensation of laser energy for areas with thick coatings.

[0040] Example 3: This embodiment provides a method for fabricating a thin-coated phosphoric acid fuel cell electrode based on feedforward control, suitable for high-speed mass production, including the following steps: (1) Catalyst slurry preparation: Deionized water and isopropanol were mixed at a volume ratio of 1:3. Platinum-carbon catalyst was dispersed in a solvent, and polytetrafluoroethylene concentrated dispersion (Pt / C to PTFE mass ratio of 6:4 to improve hydrophobicity) was added, along with 0.1% by weight of the modified thickener powder C obtained in Preparation Example 3. The total solids content was controlled at 15 wt% (low viscosity formulation). The mixture was dispersed at 5000 rpm for 30 minutes and then degassed under vacuum for 10 minutes to obtain a low viscosity slurry with a viscosity of 60 cP.

[0041] (2) Substrate feeding and feedforward data acquisition: The feeding speed of the carbon paper substrate is controlled at 5.0 m / min (high-speed mode). The reference surface density ρref is set to 90 g / m2. The deviation coefficient k is calculated in real time.

[0042] (3) Surface cleaning pretreatment: 0.5MPa high-pressure water mist spraying is used, combined with a double-stage high-power air knife (wind speed 40m / s) and a 2.0m long infrared drying tunnel (temperature 105℃) to meet the rapid drying requirements of high-speed production lines.

[0043] (4) Adaptive dynamic coating: Set the coating head lip gap to 60 μm. Implement feedforward control and set the penetration compensation coefficient α to 0.1. The dynamic flow rate calculation formula is Qtarget = Qbase × (1 + 0.1 × (1 Due to the low viscosity and high speed of the slurry, the flow rate was mainly fine-tuned to compensate for the differences in microporosity of the substrate. The wet film thickness was controlled at approximately 65 μm, and the final dry film platinum loading was approximately 0.5 mg / cm².

[0044] (5) Gradient high temperature curing: the first temperature zone is 120℃, and the temperature is held for 2 minutes (rapid volatilization); the second temperature zone is 280℃, and the temperature is held for 3 minutes; the third temperature zone is 360℃, and the temperature is held for 5 minutes (rapid sintering).

[0045] (6) Load closed-loop detection: Same as Example 1.

[0046] (7) Laser finishing: A picosecond laser with a power of 30W, a frequency of 200kHz, and a cutting speed of 2000mm / s is used. High-frequency pulses are used to adapt to the high-speed cutting requirements, and the dynamic path interpolation function of the vision system is enabled. When coating bubble defects are detected, the path is automatically fine-tuned to avoid them within the tolerance range.

[0047] Comparative example: Comparative Example 1: Compared with Example 1, the difference is that no feedforward control mechanism is used. Specifically, during the coating process in step (4), the feed pump always maintains a constant base flow rate Qbase and is not dynamically adjusted according to the substrate surface density deviation coefficient k measured in step (2). The remaining steps and parameters are the same as in Example 1.

[0048] Comparative Example 2: Compared with Example 1, the difference is that a hysteresis feedback control mechanism is used instead of real-time feedforward control. Specifically, the system uses the load deviation data measured in step (6) of the previous electrode to adjust the coating flow rate of the current electrode in step (4), instead of relying on the real-time weight data of the current substrate. The remaining steps and parameters are the same as in Example 1.

[0049] Comparative Example 3: Compared with Example 1, the difference is that: in step (7) laser trimming, no visual compensation algorithm and power linkage adjustment are used. Specifically, during cutting, only mechanical blocks are used for physical positioning, without image acquisition and affine transformation correction; and the laser maintains a constant power output of 20W, without dynamic power compensation according to the change of coating thickness. The remaining steps and parameters are the same as in Example 1.

[0050] Comparative Example 4: Compared with Example 1, the difference is that in step (1) slurry preparation, an equal mass of commercially available sodium carboxymethyl cellulose (CMC, viscosity 1000-1500 cP) was used to replace the graphene oxide modified thickener powder B obtained in Example 2. The remaining steps and parameters are the same as in Example 1.

[0051] Comparative Example 5: Compared with Example 1, the difference is that the infrared drying zone is omitted in the surface cleaning pretreatment step (3). Specifically, the substrate is directly entered into the coating process after being washed with water and dehydrated by an air knife, without deep heat drying treatment. The remaining steps and parameters are the same as in Example 1.

[0052] Test example: Test Example 1: Experimental steps: Based on the process parameters set in Example 1 (medium speed / standard feedforward), Example 2 (low speed / high load), Example 3 (high speed / thin coating), and Comparative Example 1 (no feedforward) and Comparative Example 2 (hysteresis feedback), continuous coating production was carried out, with 1000 electrode units continuously prepared in each experiment. The final catalyst loading data for each electrode was recorded using an online production line monitoring system, and the process capability index (Cpk) and relative standard deviation (RSD) were calculated. The upper limit of the specification was set to 1.05 times the target value, and the lower limit was set to 0.95 times the target value. Subsequently, 50 samples were randomly selected from the finished products of Example 1, Example 3, and Comparative Example 3 (no vision / no power linkage) for cutting quality inspection. A 2D image measuring instrument was used to measure the coordinate deviations of the electrode's outer contour and internal flow channel feature points from the design drawings, and the proportion of deviations within the ±0.05mm tolerance range was statistically analyzed. Simultaneously, the width of the heat-affected zone (HAZ) was measured using a metallographic microscope at three locations: the straight segment of the cutting edge, the corner, and the fine part of the flow channel, and the average value was calculated.

[0053] Test data: Table 1: Statistical data on process capability of electrode catalyst loading Table 2: Statistical data on dimensional accuracy and edge quality of laser cutting

[0054] Results Analysis and Conclusions: Based on the test data in Tables 1 and 2, the effectiveness of this technical solution is analyzed as follows: Regarding the consistency of catalyst loading, Table 1 shows that the Cpk value of Example 1 is 1.45, while that of Comparative Example 1 is 0.62, with an RSD of 4.87%. The areal density and porosity of the hydrophobic carbon paper substrate exhibit localized inhomogeneities. In the constant flow rate coating mode of Comparative Example 1, fluctuations in the substrate's liquid absorption capacity led to fluctuations in the final loading. Example 1 employed a feedforward control mechanism, using the substrate weight as an input variable and adjusting the feed pump flow rate in real time through a permeation compensation algorithm to offset the influence of physical differences in the substrate. Although Comparative Example 2 introduced a feedback mechanism, there was a spatial lag between the coating position and the measurement position, making it unable to correct for the instantaneous fluctuations in the current substrate. Its Cpk value was 0.91, failing to meet the stability standard of Cpk greater than 1.33.

[0055] Regarding processing accuracy and edge quality, Table 2 shows that the dimensional pass rate of Example 1 was 100%, and the width of the heat-affected zone was controlled below 20 μm; the dimensional pass rate of Comparative Example 3 was 62%, with a maximum deviation close to 0.15 mm. Flexible electrode materials undergo slight deformation during transport, and simple mechanical positioning cannot eliminate such errors. Example 1 corrected the deviation between the cutting path and the actual material position using the Otsu algorithm and affine transformation strategy. Furthermore, Comparative Example 3 showed a heat-affected zone width of 85.4 μm accompanied by carbonization, indicating that constant power cutting is difficult to adapt to electrodes with uneven thickness. Example 1 adjusted the laser power based on thickness gauge data, increasing energy in thicker areas and decreasing energy in thinner areas, ensuring penetration while reducing edge thermal damage.

[0056] Test Example 2: Experimental steps: This test evaluated the electrochemical performance and coating physical properties of the electrodes prepared in Examples 1 to 3 and Comparative Examples 4 and 5. First, the electrode under test was used as the cathode, and assembled into a membrane electrode assembly (MEA) using a standard platinum-carbon anode (platinum loading 0.5 mg / cm²) and a phosphoric acid-doped polybenzimidazole (PBI) proton exchange membrane at 150°C and 3 MPa under hot-pressing conditions. The MEA was placed in a single-cell test fixture and connected to an electrochemical workstation. The test conditions were set as follows: cell temperature 160°C, atmospheric pressure, pure hydrogen gas flowing through the anode, air flowing through the cathode, and constant gas utilization. After the cell open-circuit voltage stabilized, a current-voltage scan was performed at a rate of 10 mV / s, and the current density and peak power density at 0.6 V were recorded. Second, the coating adhesion was evaluated using a 180-degree peel strength test. The electrode sample was cut into 20 mm wide strips, adhered to the catalyst layer surface using standard pressure-sensitive tape, and rolled three times with a standard roller. The sample was fixed in a tensile testing machine and peeled at a speed of 300 mm / min. The average load was recorded and the peel strength per unit width was calculated. At the same time, the number of pinholes or coating detachment points with a diameter greater than 0.5 mm per 100 cm² electrode area was counted by transmissive light observation, and the defect density was calculated.

[0057] Test results: Table 3: Comparison of Electrochemical Performance and Physical Stability of Electrodes

[0058] Results Analysis and Conclusions: Based on the data in Table 3, the performance differences and mechanisms of each group of samples are analyzed as follows: Regarding the relationship between electrochemical performance and slurry composition, the current density at 0.6V in Example 1 was 0.684 A / cm², significantly higher than the 0.512 A / cm² in Comparative Example 4. Comparative Example 4 used conventional CMC as a thickener. CMC is mainly composed of an insulating cellulose skeleton, which easily retains ash after high-temperature carbonization, increasing the electronic resistance of the catalyst layer (ohmic impedance reaching 185 mΩ·cm²) and potentially covering the catalyst's active sites. The graphene oxide-modified thickener used in Example 1 underwent a reduction reaction during heat treatment, reducing the graphene oxide sheets to a highly conductive graphene network. This not only constructed an effective electron transport channel but also optimized the gas diffusion path through PEG segment pore formation, thereby reducing ohmic impedance and improving mass transfer efficiency.

[0059] Regarding the impact of the drying process on the integrity of the coating structure, Comparative Example 5 showed a precipitous drop in performance data, with a current density of only 0.286 A / cm², extremely low peel strength (0.35 N / cm), and a defect density as high as 18 defects / 100cm². This group did not undergo deep infrared drying after cleaning, resulting in residual moisture inside the micropores of the substrate. During the subsequent high-temperature curing process, due to the skin formation on the coating surface, the internal moisture rapidly vaporized, generating high pressure, which destroyed the uncured binder network, causing the microstructure of the catalyst layer to become loose, cracked, and even macroscopically delaminated. This structural defect not only led to the detachment of the active material but also significantly increased the contact resistance. Example 1 employed a strict infrared gradient drying process, ensuring absolute dryness of the substrate before coating and orderly evaporation of the solvent during the curing process, thereby forming a dense, uniform, and strongly adherent catalyst layer structure.

[0060] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A phosphoric acid fuel cell electrode, characterized in that, The catalyst slurry comprises the following raw materials: a hydrophobic carbon paper substrate and a catalyst slurry; the catalyst slurry contains a solvent and solid components dispersed in the solvent, the solid components including a platinum-carbon catalyst, polytetrafluoroethylene (PTFE), and a modified thickener; wherein the total solid content of the catalyst slurry is 15wt%~35wt%; the dry weight ratio of the platinum-carbon catalyst to PTFE is 6:4 to 8:2; the amount of the modified thickener added is 0.1%~0.5% of the total weight of the catalyst slurry; the modified thickener is methoxy polyethylene glycol amine-grafted graphene oxide, and its preparation method includes: activating the carboxyl groups of a graphene oxide dispersion with 1-3-dimethylaminopropyl-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide, then adding methoxy polyethylene glycol amine with a number average molecular weight of 1000~5000, reacting under conditions of pH 8.0 and temperature 60℃, and obtaining the product after dialysis and drying.

2. The method for preparing a phosphoric acid fuel cell electrode according to claim 1, characterized in that, Includes the following steps: S1. Catalyst slurry preparation: The platinum-carbon catalyst, polytetrafluoroethylene dispersion and modified thickener are dispersed in a solvent to prepare a catalyst slurry; S2. Substrate feeding and data acquisition: The hydrophobic carbon paper substrate is conveyed, and the real-time weight of the substrate is collected in real time. The surface density deviation coefficient of the current substrate area is calculated based on the set reference surface density. S3. Surface cleaning pretreatment: Cleaning and drying the surface of the substrate; S4. Adaptive dynamic coating: The catalyst slurry is coated onto the substrate surface. The control system performs feedforward control based on the areal density deviation coefficient in step 2 to adjust the flow rate of the coating feed pump or the lip gap of the coating head in real time. S5. Gradient high-temperature curing: The coated wet electrode is heat-treated sequentially through the solvent evaporation zone, the surfactant removal zone, and the sintering and curing zone. S6. Laser trimming: Using a laser to cut the cured electrode.

3. The method for preparing a phosphoric acid fuel cell electrode according to claim 2, characterized in that, In step 1, the preparation process of the catalyst slurry is as follows: after mixing and premixing the components, high shear dispersion is carried out at a speed of 2000 rpm to 5000 rpm for 30 to 45 minutes, followed by vacuum degassing under negative pressure.

4. The method for preparing a phosphoric acid fuel cell electrode according to claim 2, characterized in that, In step 3, the surface cleaning pretreatment method is as follows: deionized water atomized spray cleaning, followed by air knife dehydration and infrared drying; wherein, the temperature of the infrared drying zone is 95℃~105℃, and the moisture content of the substrate before coating is less than 0.1%.

5. The method for preparing a phosphoric acid fuel cell electrode according to claim 2, characterized in that, In step 3, the surface cleaning pretreatment method is as follows: using an atmospheric pressure plasma cleaner to bombard the surface with a mixture of argon and oxygen.

6. The method for preparing a phosphoric acid fuel cell electrode according to claim 2, characterized in that, In step 4, the specific method of feedforward control is as follows: set the basic flow rate and the permeation compensation coefficient, calculate the target flow rate using the permeation compensation algorithm, and adjust the pump speed; wherein, the value range of the permeation compensation coefficient is 0.1~0.5; and the areal density deviation coefficient is the ratio of the real-time areal density of the substrate to the reference areal density.

7. The method for preparing a phosphoric acid fuel cell electrode according to claim 2, characterized in that, In step 4, during the adaptive dynamic coating process, the lip gap of the coating head is set to 60 micrometers to 250 micrometers, and the wet film thickness is controlled to be 65 micrometers to 300 micrometers.

8. The method for preparing a phosphoric acid fuel cell electrode according to claim 2, characterized in that, In step 5, the temperature of the gradient high-temperature curing is set as follows: the temperature of the solvent evaporation zone is 80℃~120℃, the temperature of the surfactant removal zone is 240℃~280℃, and the temperature of the sintering curing zone is 330℃~360℃.

9. The method for preparing a phosphoric acid fuel cell electrode according to claim 2, characterized in that, In step 6, the specific method of laser trimming includes: identifying the marked points on the electrodes through a vision system, extracting the actual coordinates using the Otsu algorithm, and performing an affine transformation to obtain the corrected cutting path.

10. A method for preparing a phosphoric acid fuel cell electrode according to claim 2, characterized in that, In step 6, during the laser trimming process, local thickness data of the electrode is acquired simultaneously. When the local thickness exceeds the average value by 5%, the laser power is increased by 3%.

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