A method for measuring the oxygen transport resistance in the pores of a porous carbon support in a porous carbon-supported platinum catalyst of a catalytic layer of a proton exchange membrane fuel cell

Abstract

The application discloses a kind of proton exchange membrane fuel cell catalytic layer porous carbon carries platinum catalyst in porous carbon carrier pore oxygen transmission resistance measurement method, it is related to fuel cell technical field, the method is by experimental means, the pore adsorption molecular probe in the porous carbon carrier inside the porous carbon carries platinum catalyst to be detected, so that the pore inside the porous carbon carrier is plugged, then the oxygen local transmission resistance of membrane electrode being made into by the porous carbon carries platinum catalyst that molecular probe is adsorbed in pore and not adsorbed with molecular probe as cathode catalyst respectively is measured, the oxygen local transmission resistance of two is subtracted, the oxygen transmission resistance in the pore of the part being plugged by molecular probe can be obtained;The method is simple to operate, accurate measurement result can be obtained by the method of theory and practice combination, with reliability, can be used as the feasibility means of measuring the oxygen transmission resistance in the pore of the porous carbon carrier in the proton exchange membrane fuel cell catalytic layer porous carbon carries platinum catalyst.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and specifically to a method for measuring the oxygen transport resistance within the pores of a porous carbon support in a porous carbon-supported platinum catalyst in a proton exchange membrane fuel cell catalyst layer. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are crucial for my country's energy structure transformation, and improving their power density is key to achieving high-efficiency hydrogen utilization. Porous carbon supports, due to their unique pore structure, show great potential for increasing battery power density. For example, Toyota's second-generation fuel cell achieved 5.4 kW / L (2.2 A / cm³) by optimizing the pore structure of the carbon support. -2 While achieving a breakthrough in output voltage drop at high current densities (@0.66V), it still faces the common challenge of a sharp drop in output voltage at high current densities.

[0003] Concentration polarization is the main reason for the sharp drop in battery power density at high current densities, with local oxygen transport polarization accounting for about half of the cathode concentration polarization. Currently, there are many experimental measurements of local oxygen transport resistance in solid carbon-supported fuel cells. However, experimental measurement methods for the local oxygen transport process in porous carbon-supported fuel cells remain insufficient, especially the experimental measurement of oxygen transport resistance within the pores of porous carbon supports. This makes it difficult to elucidate the key influencing factors of local oxygen transport in porous carbon-supported fuel cells and their impact mechanisms on battery performance.

[0004] Therefore, how to measure the oxygen transport resistance within the pores of the porous carbon support in the porous carbon platinum catalyst of the proton exchange membrane fuel cell catalyst layer has attracted much attention. Summary of the Invention

[0005] The purpose of this invention is to provide a method for measuring the oxygen transport resistance within the pores of a porous carbon support in a porous carbon platinum catalyst layer of a proton exchange membrane fuel cell, thereby solving the following technical problems:

[0006] How to measure the oxygen transport resistance within the pores of the porous carbon support in the porous carbon platinum catalyst of a proton exchange membrane fuel cell catalyst layer.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] This invention discloses a method for measuring the oxygen transport resistance within the pores of a porous carbon support in a porous carbon platinum catalyst for a proton exchange membrane fuel cell, comprising the following steps:

[0009] Step 1: Obtain the pore size distribution of the porous carbon support in the initial porous carbon-supported platinum catalyst, and select organic molecules with diameters within the pore size distribution range of the porous carbon support as molecular probe 1.

[0010] Step 2: Dissolve the porous carbon-supported platinum catalyst and molecular probe 1 in an organic solvent and ultrasonically disperse for 2 hours. Then, let it stand at 50°C for 10 hours. Then, centrifuge to remove the free molecular probe 1. After vacuum drying, the porous carbon-supported platinum catalyst 1 with molecular probe 1 adsorbed is obtained, and the pore size distribution of the porous carbon support in the porous carbon-supported platinum catalyst 1 is obtained.

[0011] Step 3: Select organic molecules with a diameter larger than the pore size distribution range of the porous carbon support as molecular probe 2, adsorb molecular probe 2 on the surface of the porous carbon platinum catalyst to obtain porous carbon platinum catalyst 2, and ensure that the difference in molecular probe coverage area between the porous carbon platinum catalyst 1 and the porous carbon platinum catalyst 2 is ≤4%.

[0012] Step 4: Use porous carbon-supported platinum catalyst 1 and porous carbon-supported platinum catalyst 2 as cathode catalysts to prepare membrane electrode 1 and membrane electrode 2, respectively.

[0013] Step 5: Measure the limiting current density I of membrane electrode 1 and membrane electrode 2 respectively. lim Through I lim Calculate the total oxygen transport resistance R from the cathode channel inlet through the gas diffusion layer to the surface of the platinum particles within the cathode catalyst layer. total Through R total Calculate the local oxygen transport resistance R local ;

[0014] Step 6: Connect membrane electrode 2 to membrane electrode 1 via R local Subtraction yields the oxygen transport resistance at the sites where molecular probes are adsorbed within the pores of the porous carbon support in the porous carbon-supported platinum catalyst.

[0015] Preferably, in step one, the organic molecules used as molecular probe one and molecular probe two are organic compounds with different sizes that do not have a toxic effect on platinum particles.

[0016] Preferably, the organic compound is any one of benzene, naphthalene, pyrene, tetraphenylporphyrin, and polyaromatic hydrocarbons.

[0017] Preferably, in step two, the organic solvent is an ethanol-chloroform solvent.

[0018] Preferably, in step three, the method for loading molecular probe II onto the surface of porous carbon-supported platinum catalyst II is as follows: the porous carbon-supported platinum catalyst and molecular probe II are dissolved in an organic solvent and ultrasonically dispersed for 2 hours, then allowed to stand at 50°C for 10 hours, then centrifuged to remove free molecular probe II, and vacuum dried to obtain porous carbon-supported platinum catalyst II with adsorbed molecular probes; the concentration of molecular probe II in the organic solvent before and after the absorption process is measured by ultraviolet-visible spectrophotometry to determine the adsorption amount of molecular probe II on the outer surface of porous carbon-supported platinum catalyst II and calculate the coverage area of ​​molecular probe II on the outer surface of porous carbon-supported platinum catalyst II; based on the adsorption amount of molecular probe II and the size of molecular probe I, the coverage area of ​​molecular probe I on the outer surface of porous carbon-supported platinum catalyst I is calculated; the concentration of molecular probe II is adjusted according to the calculation results until the difference between the molecular probe coverage areas on the outer surfaces of porous carbon-supported platinum catalyst I and porous carbon-supported platinum catalyst II is ≤4%.

[0019] The coverage area of ​​molecular probe 2 on the outer surface of porous carbon-supported platinum catalyst 2 was calculated using the following formula:

[0020]

[0021] In the formula: A t,d Q represents the total coverage area of ​​molecular probe II on the outer surface of porous carbon-supported platinum catalyst II. d The adsorption amount of molecular probe II on the outer surface of porous carbon-supported platinum catalyst II is N. A M is Avogadro's constant. d For the molecular probe, A is the relative molecular mass. d The projected area of ​​a single molecular probe;

[0022] The coverage area of ​​molecular probe 1 on the outer surface of porous carbon-supported platinum catalyst 1 is:

[0023]

[0024] In the formula: A t,x M represents the total coverage area of ​​the molecular probe on the outer surface of the porous carbon-supported platinum catalyst. x A is the relative molecular mass of a molecular probe. x The projected area of ​​a single molecular probe.

[0025] Preferably, in step four, the preparation methods of membrane electrode one and membrane electrode two are as follows: a cathode catalyst slurry and an anode catalyst slurry are coated on the cathode side and anode side of the proton exchange membrane, respectively, to form a cathode catalyst layer and an anode catalyst layer, and then a gas diffusion layer is attached to the outside of the cathode catalyst layer and the anode catalyst layer, respectively; wherein, the cathode catalyst slurry is a slurry formed by dissolving the cathode catalyst in Nafion, water and alcohol solution.

[0026] Preferably, in step five, the limiting current density is measured as follows: an oxygen-nitrogen mixture containing 0.5% oxygen is introduced onto the cathode side of the membrane electrode, while hydrogen is introduced onto the anode side, and then a linear sweep voltammetric method is used at 2 mV / s. -1 The scan rate is set, and the current density of the membrane electrode is measured within a voltage range of 0.6V-0.15V, where the maximum current density is I. lim .

[0027] Preferably, in step five, via I lim Calculate R total The calculation formulas include:

[0028]

[0029] In the formula: F is the Faraday constant, Where F is the oxygen concentration in the cathode channel, F is the temperature, R is the universal gas constant, and P is the oxygen concentration in the cathode channel. c P is the total pressure of the cathode inlet gas. water Here, RH represents the partial pressure of water vapor, and RH represents the relative humidity of the air entering the cathode. This represents the volume fraction of oxygen under dry intake conditions.

[0030] Preferably, the R total Including pressure-related resistance R P and resistance R independent of pressure NP The R total R P R NP The calculation formula between them is:

[0031] R total =R P +R NP ;

[0032] The R P Molecular diffusion resistance R MD The R MD Including the oxygen molecule diffusion resistance R of the cathode gas diffusion substrate CGDB,MD Oxygen molecule diffusion resistance R in the cathode microporous layer CMPL,MD Oxygen molecule diffusion resistance R in the cathode catalyst layer CCL,MD The R P The calculation formula is:

[0033] R P =R CGDB,MD +R CMPL,MD +R CCL,MD ;

[0034] The R NP Including Knudsen diffusion resistance R KnuAnd the local oxygen transport resistance R of the cathode catalyst layer local The R Knu Including the oxygen Knudsen diffusion resistance R in the cathode microporous layer CMPL,Knu And the oxygen Knudsen diffusion resistance R in the cathode catalyst layer CCL,Knu The R NP The calculation formula is:

[0035] R NP =R CMPL,Knu +R CCL,Knu +R local .

[0036] Preferably, in step five, through R total Calculate R local The method is as follows: The R local Compared to R Knu It exhibits a stronger temperature change function, distinguishing R based on the nonlinear fitting of temperature. local and R Knu The following relationship formula is obtained:

[0037]

[0038]

[0039] In the formula: A and B are fitting constants.

[0040] The beneficial effects of this invention are:

[0041] This invention employs an experimental method to adsorb molecular probes into the pores of a porous carbon support in a porous platinum-supported carbon catalyst, thereby blocking the pores within the porous carbon support. Then, porous platinum-supported carbon catalysts with and without adsorbed molecular probes are used as cathode catalysts to fabricate membrane electrodes. The local oxygen transport resistance of these electrodes is measured, and the difference between the two local oxygen transport resistances yields the oxygen transport resistance within the pores blocked by the molecular probes. This method is simple to operate, provides accurate measurement results through a combination of theoretical and practical approaches, and is reliable. It can serve as a feasible means to measure the oxygen transport resistance within the pores of a porous carbon support in a proton exchange membrane fuel cell catalyst layer. Attached Figure Description

[0042] The invention will now be further described with reference to the accompanying drawings.

[0043] Figure 1 This is a flowchart of a method for measuring the oxygen transport resistance within the pores of a porous carbon support in a proton exchange membrane fuel cell catalyst layer, as described in this embodiment of the invention.

[0044] Figure 2This is a schematic diagram of the structure of the commercial Premeterk porous carbon-supported platinum catalyst in step one of Embodiment 1 of the present invention;

[0045] Figure 3 This is a pore size distribution diagram of Pt / C in step two of embodiment one of the present invention;

[0046] Figure 4 This is a schematic diagram of the Pt / C-TPP structure in step two of embodiment one of the present invention;

[0047] Figure 5 This is a pore size distribution diagram of Pt / C-TPP in step two of embodiment one of the present invention;

[0048] Figure 6 This is a schematic diagram of the membrane electrode 1 in step four of embodiment one of the present invention;

[0049] Figure 7 This is the limiting current density curve in step five of embodiment one of the present invention;

[0050] Figure 8 In step five of embodiment one of the present invention, R is distinguished based on the nonlinear fitting of temperature. local and R Knu The resulting linear relationship graph;

[0051] Figure 9 In step six of embodiment one of the present invention, the membrane electrode two and the membrane electrode one are connected by R... total The subtraction diagram shows the oxygen transport resistance at the sites where molecular probes are adsorbed within the pores of the porous carbon support. Detailed Implementation

[0052] The technical solutions of 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.

[0053] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0054] Please see Figure 1 This embodiment discloses a method for measuring the oxygen transport resistance within the pores of a porous carbon support in a porous carbon platinum catalyst in a proton exchange membrane fuel cell catalyst layer, comprising the following steps:

[0055] Step 1: Select a commercial Premeterk porous carbon-supported platinum catalyst (hereinafter referred to as Pt / C), the structural diagram of which is shown below. Figure 2 As shown, its aperture distribution was measured, and the results were obtained as follows. Figure 3 The pore size distribution diagram is shown. Based on the pore size distribution of Pt / C, a 2nm diameter organic molecule, tetraphenylporphyrin (hereinafter referred to as TPP), was selected as molecular probe one to fill the pores in Pt / C with a pore diameter of about 2nm.

[0056] Step 2: Add 1.3g of TPP to 1.5mL of ethanol-chloroform solvent to form a mixed solution, wherein the volume ratio of ethanol to chloroform is 1:2. Then add 10mg of Pt / C to the mixed solution to form a catalyst solution. Sonicate the catalyst solution for 2 hours, then let it stand at 50℃ for 10 hours. Remove free TPP by centrifugation, and vacuum dry at 50℃ for 2 hours to obtain Pt / C with TPP adsorbed in the pores and on the surface (hereinafter referred to as Pt / C-TPP). Its structural schematic diagram is shown below. Figure 4 As shown, its aperture distribution diagram is as follows: Figure 5 As shown.

[0057] Step 3: Select organic polyaromatic hydrocarbons (hereinafter referred to as PAHs) with a diameter of 6-8 nm as molecular probe 2. Add PAHs to 1.5 mL of ethanol-chloroform solvent to form a mixed solution, wherein the volume ratio of ethanol to chloroform solvent is ethanol:chloroform = 1:2. Then add 10 mg of Pt / C to the mixed solution to form a catalyst solution. Sonicate the catalyst solution for 2 h, then let it stand at 50 °C for 10 h, then remove the free PAHs by centrifugation, and vacuum dry at 50 °C to obtain Pt / C with PAHs adsorbed on the surface (hereinafter referred to as Pt / C-PAHs).

[0058] The concentration of PAH in the ethanol-chloroform solvent before and after the absorption process was measured by ultraviolet-visible spectrophotometry to determine the amount of PAH adsorbed on the surface of Pt / C-PAH.

[0059] The area of ​​PAH covering the outer surface of Pt / C can be calculated using the following formula:

[0060]

[0061] In the formula: A t,d Q represents the total coverage area of ​​PAH on the outer surface of Pt / C. d The adsorption amount of PAH on the outer surface of Pt / C is N. A M is Avogadro's constant. d A is the relative molecular mass of PAH. d The projected area of ​​a single PAH;

[0062] The area of ​​TPP covering the outer surface of Pt / C can be calculated using the following formula:

[0063]

[0064] In the formula: A t,x M represents the total coverage area of ​​TPP on the outer surface of multiple Pt / C layers. x A is the relative molecular mass of TPP. x The projected area of ​​the TPP;

[0065] Adjust the amount of PAH added to the ethanol-chloroform solvent in this step according to the calculation results until the difference in molecular probe coverage area between Pt / C-TPP and Pt / C-PAH surfaces is ≤4%. For example, in this step, the final amount of PAH added is determined to be 1.5g.

[0066] Step 4: First, prepare membrane electrode 1: Weigh 2.5 mg of Pt / C-TPP and dissolve it in 0.83 mg of Nafion solvent. Add a mixed solution of deionized water and isopropanol (water-to-alcohol volume ratio 1:1), sonicate for 15 minutes, and shear at high speed for 25 minutes to obtain a uniform cathode catalyst slurry. Repeat the above steps with Pt / C to prepare the anode catalyst slurry. Use ultrasonic spraying to spray the cathode and anode catalyst slurries onto the cathode and anode sides of the proton exchange membrane, respectively, to form the cathode and anode catalyst layers. Then, attach carbon paper to the outer surfaces of the cathode and anode catalyst layers to complete the preparation. Figure 6 The membrane electrode 1 is shown; then the membrane electrode 2 is prepared. Compared with the preparation method of the membrane electrode 1, the only difference is that Pt / C-TPP is replaced with Pt / C-PAH. The other steps and conditions are kept the same, and finally the membrane electrode 2 is obtained.

[0067] Step 5: Test the limiting current density I of membrane electrode 2 and membrane electrode 1 using a fuel cell single-cell test platform. lim The humidity was 80%, and a mixture of 0.5% oxygen / nitrogen gas was passed through the cathode while hydrogen gas was introduced at the anode; then, linear sweep voltammetry was used at 2 mV / s. -1 The scan rate was adjusted, and the membrane electrode current density was measured within a voltage range of 0.6V-0.15V to obtain the following results: Figure 7 The limiting current density curve shown is given, where the maximum current density is I. lim To calculate the local oxygen transport resistance, I was measured at four temperatures (338 K, 343 K, 348 K, and 353 K) under four different operating pressures (100 kPa, 140 kPa, 180 kPa, and 220 kPa). lim The cathode gas flow rate was set to 3.78 NL min. -1Meanwhile, the anode gas flow rate was maintained at 0.5 NL min. -1 ; through I lim Calculate the total oxygen transport resistance R from the cathode channel inlet through the gas diffusion layer to the surface of the platinum particles in the cathode catalyst layer. total Its calculation formula includes:

[0068]

[0069] In the formula: F is the Faraday constant, Where is the oxygen concentration in the cathode channel, T is the temperature, R is the universal gas constant, and P is the oxygen concentration in the cathode channel. c P is the total pressure of the cathode inlet gas. water Here, RH represents the partial pressure of water vapor, and RH represents the relative humidity of the air entering the cathode. This represents the volume fraction of oxygen under the condition of dry intake air.

[0070] The R total Including pressure-related resistance R P and resistance R independent of pressure NP The R total R P R NP The calculation formula between them is:

[0071] R total =R P +R NP

[0072] The R P Molecular diffusion resistance R MD The R MD Including the oxygen molecule diffusion resistance R of the cathode gas diffusion substrate CGDBMD Oxygen molecule diffusion resistance R in the cathode microporous layer CMPLMD Oxygen molecule diffusion resistance R in the cathode catalyst layer CCL,MD The R P The calculation formula is:

[0073] R P =R CGDB,MD +R CMPL,MD +R CCL,MD

[0074] The R NP Including Knudsen diffusion resistance R Knu And the local oxygen transport resistance R of the cathode catalyst layer local The R Knu Including the oxygen Knudsen diffusion resistance R in the cathode microporous layer CMPL,Knu And the oxygen Knudsen diffusion resistance R in the cathode catalyst layer CCL,Knu The R NP The calculation formula is:

[0075] R NP =R CMPL,Knu +R CCL,Knu +R local

[0076] The R local Compared to R Knu It exhibits a stronger temperature change function, distinguishing R based on the nonlinear fitting of temperature. local and R Knu , to obtain Figure 8 The linear relationship diagram shown is used to derive the following relationship formula:

[0077]

[0078] In the formula: A and B are fitting constants;

[0079] according to Figure 8 and Figure 9 It can be seen that R of membrane electrode one local The R value is 42.65 s / m. local It is 32.42 s / m.

[0080] Step Six, please refer to Figure 9 Connect membrane electrode two to membrane electrode one's R local Subtraction yields the oxygen transport resistance at the sites where molecular probes are adsorbed within the pores of the porous carbon support in the porous platinum catalyst. Based on... Figure 9 It can be obtained that the oxygen transport resistance at the site where the molecular probe is adsorbed in the porous carbon pores in the embodiment is 10.24 s / m.

[0081] In the description of this invention, it should be understood that the terms "upper," "lower," "left," and "right," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation or specific orientational structure and operation. Therefore, they should not be construed as limitations on the invention. Furthermore, "first" and "second" are only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "multiple" means two or more.

[0082] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for measuring the oxygen transport resistance within the pores of a porous carbon support in a porous carbon platinum catalyst layer of a proton exchange membrane fuel cell, characterized in that, Includes the following steps: Step 1: Obtain the pore size distribution of the porous carbon support in the initial porous carbon-supported platinum catalyst, and select organic molecules with diameters within the pore size distribution range of the porous carbon support as molecular probe 1. Step 2: Dissolve the porous carbon-supported platinum catalyst and molecular probe 1 in an organic solvent and ultrasonically disperse for 2 hours. Then, let it stand at 50°C for 10 hours. Then, centrifuge to remove the free molecular probe 1. After vacuum drying, the porous carbon-supported platinum catalyst 1 with molecular probe 1 adsorbed is obtained, and the pore size distribution of the porous carbon support in the porous carbon-supported platinum catalyst 1 is obtained. Step 3: Select organic molecules with a diameter larger than the pore size distribution range of the porous carbon support as molecular probe 2, adsorb molecular probe 2 on the surface of the porous carbon platinum catalyst to obtain porous carbon platinum catalyst 2, and ensure that the difference in molecular probe coverage area between the porous carbon platinum catalyst 1 and the porous carbon platinum catalyst 2 is ≤4%. Step 4: Use porous carbon-supported platinum catalyst 1 and porous carbon-supported platinum catalyst 2 as cathode catalysts to prepare membrane electrode 1 and membrane electrode 2, respectively. Step 5: Measure the limiting current density I of membrane electrode 1 and membrane electrode 2 respectively. lim Through I lim Calculate the total oxygen transport resistance R from the cathode channel inlet through the gas diffusion layer to the surface of the platinum particles within the cathode catalyst layer. total Through R total Calculate the local oxygen transport resistance R local ; Step 6: Connect membrane electrode 2 to membrane electrode 1 via R local Subtraction yields the oxygen transport resistance at the sites where molecular probes are adsorbed within the pores of the porous carbon support in the porous carbon-supported platinum catalyst.

2. The method for measuring the oxygen transport resistance within the pores of the porous carbon support in the porous carbon platinum catalyst of the proton exchange membrane fuel cell catalyst layer according to claim 1, characterized in that, In step one, the organic molecules used as molecular probe one and molecular probe two are organic compounds with different sizes that do not have a toxic effect on platinum particles.

3. The method for measuring the oxygen transport resistance within the pores of the porous carbon support in the porous carbon platinum catalyst of the proton exchange membrane fuel cell catalyst layer according to claim 2, characterized in that, The organic compound is any one of benzene, naphthalene, pyrene, tetraphenylporphyrin, and polyaromatic hydrocarbons.

4. The method for measuring the oxygen transport resistance within the pores of the porous carbon support in the porous carbon platinum catalyst of the proton exchange membrane fuel cell catalyst layer according to claim 1, characterized in that, In step two, the organic solvent is an ethanol-chloroform solvent.

5. The method for measuring the oxygen transport resistance within the pores of the porous carbon support in the porous carbon platinum catalyst of the proton exchange membrane fuel cell catalyst layer according to claim 1, characterized in that, In step three, the method for loading molecular probe II onto the surface of porous carbon-supported platinum catalyst II is as follows: the porous carbon-supported platinum catalyst and molecular probe II are dissolved in an organic solvent and ultrasonically dispersed for 2 hours, then allowed to stand at 50°C for 10 hours, then centrifuged to remove free molecular probe II, and vacuum dried to obtain porous carbon-supported platinum catalyst II adsorbed with molecular probe II; the concentration of molecular probe II in the organic solvent before and after the absorption process is measured by ultraviolet-visible spectrophotometry to determine the adsorption amount of molecular probe II on the surface of porous carbon-supported platinum catalyst II and calculate the coverage area of ​​molecular probe II on the surface of porous carbon-supported platinum catalyst II; based on the adsorption amount of molecular probe II and the size of molecular probe I, the coverage area of ​​molecular probe I on the surface of porous carbon-supported platinum catalyst I is calculated; the concentration of molecular probe II is adjusted according to the calculation results until the difference in the molecular probe coverage area on the surfaces of porous carbon-supported platinum catalyst I and porous carbon-supported platinum catalyst II is ≤4%.

6. The method for measuring the oxygen transport resistance within the pores of the porous carbon support in the porous carbon platinum catalyst of the proton exchange membrane fuel cell catalyst layer according to claim 1, characterized in that, In step four, the preparation methods for membrane electrode one and membrane electrode two are as follows: a cathode catalyst slurry and an anode catalyst slurry are coated on the cathode side and anode side of the proton exchange membrane, respectively, to form a cathode catalyst layer and an anode catalyst layer, and then a gas diffusion layer is attached to the outside of the cathode catalyst layer and the anode catalyst layer, respectively; wherein, the cathode catalyst slurry is a slurry formed by dissolving the cathode catalyst in Nafion, water and alcohol solution.

7. The method for measuring the oxygen transport resistance within the pores of the porous carbon support in the porous carbon platinum-supported catalyst of the proton exchange membrane fuel cell catalyst layer according to claim 1, characterized in that, In step five, the limiting current density is measured as follows: an oxygen-nitrogen mixture containing 0.5% oxygen is introduced onto the cathode side of the membrane electrode, while hydrogen is introduced onto the anode side. Then, a linear sweep voltammetric method is used at a current density of 2 mV / s. -1 The scan rate is set, and the current density of the membrane electrode is measured within a voltage range of 0.6V-0.15V, where the maximum current density is I. lim .

8. The method for measuring the oxygen transport resistance within the pores of the porous carbon support in the porous carbon platinum catalyst of the proton exchange membrane fuel cell catalyst layer according to claim 1, characterized in that, In step five, via I lim Calculate R total The calculation formulas include: In the formula: F is the Faraday constant, Where is the oxygen concentration in the cathode channel, T is the temperature, R is the universal gas constant, and P is the oxygen concentration in the cathode channel. c P is the total pressure of the cathode inlet gas. water Here, RH represents the partial pressure of water vapor, and RH represents the relative humidity of the air entering the cathode. This represents the volume fraction of oxygen under dry intake conditions.

9. The method for measuring the oxygen transport resistance within the pores of the porous carbon support in the porous carbon platinum catalyst of the proton exchange membrane fuel cell catalyst layer according to claim 8, characterized in that, The R total Including pressure-related resistance R P and resistance R independent of pressure NP The R total R P R NP The calculation formula between them is: R total =R P +R NP ; The R P Molecular diffusion resistance R MD The R MD Including the oxygen molecule diffusion resistance R of the cathode gas diffusion substrate CGDB,MD Oxygen molecule diffusion resistance R in the cathode microporous layer CMPL,MD Oxygen molecule diffusion resistance R in the cathode catalyst layer CCL,MD The R P The calculation formula is: R P =R CGDB,MD +R CMPL,MD +R CCL,MD ; The R NP Including Knudsen diffusion resistance R Knu And the local oxygen transport resistance R of the cathode catalyst layer local The R Knu Including the oxygen Knudsen diffusion resistance R in the cathode microporous layer CMPL,Knu And the oxygen Knudsen diffusion resistance R in the cathode catalyst layer CCL,Knu The R NP The calculation formula is: R NP =R CMPL,Knu +R CCL,Knu +R local 。 10. The method for measuring the oxygen transport resistance within the pores of the porous carbon support in the porous carbon platinum-supported catalyst of the proton exchange membrane fuel cell catalyst layer according to claim 9, characterized in that, In step five, through R total Calculate R local The method is as follows: The R local Compared to R Knu It exhibits a stronger temperature change function, distinguishing R based on the nonlinear fitting of temperature. local and R Knu The following relationship formula is obtained: In the formula: A and B are fitting constants.

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