A method for measuring the mass transfer resistance of catalysts in the internal pores of mesoporous carbon

Abstract

The present invention belongs to the technical field of material measurement methods, and specifically relates to a method for measuring the mass transfer resistance of a catalyst in a pore inside a mesoporous carbon. First, the mass transfer resistance of a single pore is analyzed, and the types of mass transfer resistance of a single pore and their mutual relationships are clarified. By constructing a microscopic model of platinum nanoparticles covered with a water film, and combining the concentration of oxygen in the pores and the law of mass transfer flux changes, the mass transfer resistance value of the catalyst in the pore inside the mesoporous carbon is obtained. The method of the present invention can obtain the mass transfer resistance value in a single pore, and provides theoretical guidance for reducing the loading of platinum nanoparticles and promoting the commercialization of proton exchange membrane fuel cells.

Description

Technical Field

[0001] The invention belongs to the technical field of material measurement methods, and in particular relates to a method for measuring the mass transfer resistance of a catalyst in the internal pores of mesoporous carbon. Background Art

[0002] Proton exchange membrane fuel cells have attracted widespread attention due to their high energy conversion efficiency, high power density and zero pollution, but their high cost has seriously hindered their commercialization process. The cathode catalyst layer is an important component of the proton exchange membrane fuel cell. The cathode catalyst layer includes a carbon carrier, an ionomer and platinum nanoparticles. The platinum nanoparticles are catalysts, the carbon carrier is used to load the platinum nanoparticles, and the ionomer is covered on the platinum nanoparticles. Among them, the cost of platinum nanoparticles accounts for half of the total cost of proton exchange membrane fuel cells. However, when the platinum nanoparticle loading is reduced, the strong adsorption of platinum nanoparticles on the sulfonate groups in the ionomer causes a higher local oxygen transfer resistance, which reduces the current output of the battery.

[0003] The method of using mesoporous carbon as a carrier to load catalysts is considered to be an effective method to reduce mass transfer resistance. The schematic diagram of the catalyst inside the mesoporous carbon is shown in Figure 2 As shown, the mesoporous carbon carrier 1 contains pores, a water film 3 is formed in the pores, a portion of the platinum nanoparticles are loaded inside the pores, forming internal platinum nanoparticles 4, and the ionomer cannot penetrate into the pores inside the mesoporous carbon carrier 1 due to size limitations, forming ionomers 2 outside the pores, and the internal platinum nanoparticles 4 avoid being "poisoned" by adsorption of sulfonic acid radicals and obtain higher activity. However, although experiments have proved that the pores in the mesoporous carbon carrier 1 can reduce the mass transfer resistance, the specific value of the mass transfer resistance inside a single pore cannot be measured, which is not conducive to reducing the platinum nanoparticle loading and promoting the commercialization of proton exchange membrane fuel cells. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for measuring the mass transfer resistance of catalysts in the pores of mesoporous carbon. The mass transfer resistance value in a single pore can be obtained by the method of the present invention, providing theoretical guidance for reducing the loading of platinum nanoparticles and promoting the commercialization of proton exchange membrane fuel cells.

[0005] The present invention is specifically implemented through the following technical solutions.

[0006] The present invention performs the following analysis on the mass transfer resistance of a single pore:

[0007] For mesoporous carbon internal pore catalysts, the mass transfer resistance of a single pore inside is divided into the following types:

[0008] (1) Local transport resistance of a single Pt nanoparticle in a pore , which consists of two resistances: the diffusion resistance of oxygen from the pore entrance in the water film to the surface of a single platinum nanoparticle , and the adsorption resistance on the surface of a single Pt nanoparticle in the pore .

[0009] (2) Total resistance of oxygen in a single pore , which consists of two parts: the total diffusion resistance of oxygen in a single pore , and the total resistance due to the adsorption resistance of all Pt nanoparticles within a single pore .

[0010] Based on the above analysis, the present invention provides a method capable of measuring the above-mentioned various resistances. Through the method of the present invention, the values ​​of the above-mentioned various resistances can be quantitatively determined.

[0011] Specifically, the method for measuring the mass transfer resistance of the internal pore catalyst of the mesoporous carbon provided by the present invention comprises the following steps:

[0012] Step 1: Construct a microscopic model of water film covering platinum nanoparticles, and obtain the adsorption resistance of a single platinum nanoparticle surface in the pore based on molecular dynamics simulation .

[0013] Step 2: Obtain the oxygen concentration variation equation and the oxygen mass transfer flux variation equation of the internal pores of the mesoporous carbon through the oxygen diffusion equation of the internal pores of the mesoporous carbon.

[0014] Step 3: Obtain the diffusion resistance generated by oxygen diffusion from the pore entrance in the water film to the surface of a single platinum nanoparticle through the oxygen concentration change equation of the internal pores of the mesoporous carbon and the oxygen mass transfer flux change equation of the internal pores of the mesoporous carbon. , the total diffusion resistance of oxygen in a single pore and the total resistance due to the adsorption resistance of all Pt nanoparticles within a single pore .

[0015] Step 4: Adsorption resistance of a single platinum nanoparticle surface in the pore and the diffusion resistance of oxygen from the pore entrance to the surface of a single platinum nanoparticle in the water film , the local transport resistance of a single platinum nanoparticle in the pore is obtained ; The total resistance due to the adsorption resistance of all Pt nanoparticles within a single pore and the total diffusion resistance of oxygen in a single pore , to obtain the total resistance of oxygen in a single pore .

[0016] Preferably, the microscopic model of the water film covering the platinum nanoparticles includes from top to bottom: an oxygen layer composed of oxygen molecules, a water film layer composed of water molecules, platinum nanoparticles composed of platinum molecules, and a graphite carbon layer composed of carbon molecules, wherein the water film layer completely covers the platinum nanoparticles, and oxygen passes through the water film layer to reach the surface of the platinum nanoparticles. The number of graphite carbon layers is 5. The pores in the graphite carbon layer are covered by condensed liquid water. The pores in the graphite carbon layer are regarded as straight holes with equal cross-sections. The non-equilibrium dissolution resistance generated by oxygen in the dissolution process of the water film layer is ignored.

[0017] The above microscopic model was processed as follows: the potential energy of all molecules in the microscopic model was calculated using the condensed phase optimized molecular force field for atomistic simulation studies; the Newtonian equations of motion were solved using the Verle algorithm with a time step of 1 fs; the long-range electrostatic interactions were calculated using the particle-particle-particle-mesh method with an accuracy of 10 -4 kcal·mol -1 The system temperature was controlled by a North-Hoover thermostat at 353 K with a relaxation time of 0.1 ps. Each microscopic model was simulated in a canonical ensemble for 5 ns of molecular dynamics. After the simulation, the mass transfer flux of oxygen on the surface of platinum nanoparticles was calculated. , using the mass transfer flux of oxygen on the surface of platinum nanoparticles Obtaining the adsorption resistance of a single platinum nanoparticle surface within a pore .

[0018] Preferably, the mass transfer flux of oxygen on the surface of platinum nanoparticles is divided by the interface concentration difference , to obtain the adsorption resistance of a single platinum nanoparticle surface in the pore .

[0019] Preferably, the concentration difference of oxygen through the diffusion path in the water film layer is divided by the mass transfer flux of oxygen on the surface of the platinum nanoparticles. , to obtain the diffusion resistance of a single platinum nanoparticle .

[0020] Preferably, the oxygen diffusion equation in the internal pores of the mesoporous carbon is:

[0021] ;

[0022] ;

[0023] Where y is the distance between different positions in the pore and the bottom of the pore, is the mass transfer flux of oxygen at different positions in the pore, is the current density at different positions in the pore, F is the Faraday constant, is the diffusion coefficient of oxygen in water, is the concentration of oxygen at different locations in the pore.

[0024] The equation for the change of oxygen concentration in the pores of mesoporous carbon is:

[0025] ;

[0026] ;

[0027] In the formula, is the concentration of oxygen at different locations in the pore, is the oxygen concentration on the water film side of the gas-water interface, is the pore depth, y is the distance between different positions in the pore and the bottom of the pore, is the diffusion coefficient of oxygen in water, is the adsorption resistance on the surface of a single platinum nanoparticle in the pore, is the roughness factor within the pores.

[0028] The oxygen mass transfer flux variation equation of the internal pores of mesoporous carbon is:

[0029] ;

[0030] In the formula, is the mass transfer flux of oxygen at different positions in the pore.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention analyzes the mass transfer resistance of a single pore in a mesoporous carbon carrier, clarifies the types of mass transfer resistance of a single pore and their relationships, and obtains the mass transfer resistance value in a single pore by constructing a microscopic model of platinum nanoparticles covered with a water film and combining the concentration of oxygen in the pores and the law of mass transfer flux changes. The present invention overcomes the research scale limitation of experimental measurements and provides a reliable calculation and analysis method for mass transfer resistance, which is conducive to reducing the platinum nanoparticle loading and promoting the commercialization of proton exchange membrane fuel cells.

[0033] The measurement results of the present invention are accurate and reliable, which provides a scientific basis for further optimizing the design of mesoporous carbon catalysts and is conducive to the catalysts showing optimal performance in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of the method for measuring the mass transfer resistance of the catalyst in the internal pores of mesoporous carbon of the present invention.

[0035] Figure 2 Schematic diagram of the catalyst inside the mesoporous carbon pores, where 1 is the mesoporous carbon support, 2 is the ionomer outside the pores, 3 is the water film, and 4 is the internal platinum nanoparticles.

[0036] Figure 3 Schematic diagram of oxygen concentration distribution in the pores.

[0037] Figure 4 This is a graph showing the corresponding relationship between the diffusion resistance of oxygen diffusing from the pore entrance in the water film to the surface of a single platinum nanoparticle and the total diffusion resistance of oxygen diffusing in a single pore.

[0038] Figure 5 Flow chart for calculating the adsorption resistance of a single platinum nanoparticle surface in a pore based on the dichotomy method using experimental data.

[0039] Figure 6 This is a graph showing the change in local transport resistance of a single platinum nanoparticle in a pore when there are multiple platinum nanoparticles in the pore.

[0040] Figure 7 This is the correspondence diagram between the diffusion resistance of a single platinum nanoparticle calculated by molecular dynamics and the diffusion resistance generated by oxygen diffusing from the pore entrance in the water film to the surface of a single platinum nanoparticle.

[0041] Figure 8 This is a graph showing the change in pore resistance with the number of platinum nanoparticles in the pore. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0043] The method for measuring the mass transfer resistance of the internal pore catalyst of the mesoporous carbon provided by the present invention is as follows: Figure 1 As shown, the following steps are included:

[0044] A microscopic model of water film covering platinum nanoparticles was constructed, and the adsorption resistance of a single platinum nanoparticle surface in the pore was obtained based on molecular dynamics simulation. .

[0045] The oxygen diffusion equation of the internal pores of the mesoporous carbon is used to obtain the oxygen concentration variation equation of the internal pores of the mesoporous carbon and the oxygen mass transfer flux variation equation of the internal pores of the mesoporous carbon.

[0046] The diffusion resistance of oxygen from the pore entrance to the surface of a single platinum nanoparticle in the water film was obtained by using the oxygen concentration variation equation of the pores inside the mesoporous carbon and the oxygen mass transfer flux variation equation of the pores inside the mesoporous carbon. , the total diffusion resistance of oxygen in a single pore and the total resistance due to the adsorption resistance of all Pt nanoparticles within a single pore .

[0047] Adsorption resistance across the surface of a single platinum nanoparticle within a pore and the diffusion resistance of oxygen from the pore entrance to the surface of a single platinum nanoparticle in the water film , the local transport resistance of a single platinum nanoparticle in the pore is obtained ; The total resistance due to the adsorption resistance of all Pt nanoparticles within a single pore and the total diffusion resistance of oxygen in a single pore , to obtain the total resistance of oxygen in a single pore .

[0048] The above contents are described in detail below.

[0049] S1. Construct a microscopic model of water film covering platinum nanoparticles and obtain the adsorption resistance of a single platinum nanoparticle surface in the pore based on molecular dynamics simulation .

[0050] The microscopic model of water film covering platinum nanoparticles includes, from top to bottom: an oxygen layer composed of oxygen molecules, a water film layer composed of water molecules, platinum nanoparticles composed of platinum molecules, and a graphite carbon layer composed of carbon molecules. The number of graphite carbon layers is 5. The water film layer completely covers the platinum nanoparticles, and oxygen will pass through the water film layer to reach the surface of the platinum nanoparticles. The holes in the graphite carbon layer are covered by condensed liquid water. The potential energy of all molecules in the model is calculated using the condensed phase optimized molecular force field for atomic simulation studies. The Verret algorithm is used to solve Newton's equations of motion with a time step of 1 fs. The particle-particle-particle-mesh method is used to calculate long-range electrostatic interactions with an accuracy of 10 -4 kcal·mol -1 The system temperature was controlled by a North-Hoover thermostat at 353 K with a relaxation time of 0.1 ps. Each model was simulated in a canonical ensemble for 5 ns of molecular dynamics. After the simulation, the mass transfer flux of oxygen on the surface of the platinum nanoparticles was calculated:

[0051] (1);

[0052] In the formula, is the mass transfer flux of oxygen on the surface of platinum nanoparticles, is the number of oxygen molecules reaching the surface of the platinum nanoparticles, is Avogadro's constant, is the surface area of ​​the platinum nanoparticles, is the mass transfer time.

[0053] Then, the adsorption resistance on the surface of a single platinum nanoparticle in the pore is obtained by dividing the interfacial concentration difference by the mass transfer flux of oxygen on the surface of the platinum nanoparticle:

[0054] (2);

[0055] In the formula, is the adsorption resistance on the surface of a single platinum nanoparticle in the pore, is the concentration of oxygen at the interface between the water film and the platinum nanoparticles, is the concentration of oxygen at the interface between the water film and the platinum nanoparticles, is the mass transfer flux of oxygen on the surface of platinum nanoparticles.

[0056] In addition, the diffusion resistance of a single platinum nanoparticle is obtained by dividing the concentration difference of oxygen diffusion path in the water film layer by the mass transfer flux of oxygen on the surface of the platinum nanoparticle:

[0057] (3);

[0058] In the formula, is the diffusion resistance of a single platinum nanoparticle, is the concentration of oxygen at the interface between gas and water film, is the concentration of oxygen at the interface between the water film and the platinum nanoparticles, is the mass transfer flux of oxygen on the surface of Pt nanoparticles.

[0059] S2. After the molecular dynamics calculation is completed Afterwards, the oxygen diffusion equation in the pores of mesoporous carbon is derived, and the oxygen concentration change equation in the pores of mesoporous carbon and the oxygen mass transfer flux change equation in the pores of mesoporous carbon are obtained. Figure 3 In the figure, the shaded part is the water film layer, and the black curve represents the concentration of oxygen at different positions in the pores. Among them, the oxygen diffusion equation in the pores of mesoporous carbon is:

[0060] (4);

[0061] Where y is the distance between different positions in the pore and the bottom of the pore, is the mass transfer flux of oxygen at different positions in the pore, is the current density at different locations in the pore, F is the Faraday constant.

[0062] (5);

[0063] In the formula, is the diffusion coefficient of oxygen in water, is the concentration of oxygen at different locations within the pore.

[0064] The source term calculation method is:

[0065] (6);

[0066] In the formula, is the volume current density at different positions in the pore, is the adsorption resistance on the surface of a single platinum nanoparticle in the pore, is the hole depth, is the oxygen concentration on the surface of the platinum nanoparticles at different locations in the pore, is the roughness factor in the pores, , is the surface area of ​​a single platinum nanoparticle, is the pore entrance cross-sectional area, n is the number of Pt nanoparticles within the pores.

[0067] The inlet boundary conditions are:

[0068] (7);

[0069] In the formula, is the oxygen concentration at the pore entrance, is the oxygen concentration on the water film side of the gas-water interface.

[0070] The boundary condition at the bottom of the pore is:

[0071] (8);

[0072] in, It refers to the mass transfer flux of oxygen at the bottom of the pore.

[0073] Therefore, the equation for the change of oxygen concentration in the pores of mesoporous carbon can be obtained as follows:

[0074] (9);

[0075] In the formula, is the concentration of oxygen at different locations in the pore, is the oxygen concentration on the water film side of the gas-water interface, is the pore depth, y is the distance between different positions in the pore and the bottom of the pore, , is the intermediate parameter in the calculation process, is the diffusion coefficient of oxygen in water, is the adsorption resistance on the surface of a single platinum nanoparticle in the pore, is the roughness factor within the pores.

[0076] The oxygen mass transfer flux variation equation of the internal pores of mesoporous carbon is:

[0077] (10).

[0078] S3. The diffusion resistance generated by oxygen diffusion from the pore entrance in the water film to the surface of a single platinum nanoparticle is obtained through the oxygen concentration change equation of the internal pores of the mesoporous carbon and the oxygen mass transfer flux change equation of the internal pores of the mesoporous carbon. , the total diffusion resistance of oxygen in a single pore and the total resistance due to the adsorption resistance of all Pt nanoparticles within a single pore .

[0079] The diffusion resistance of oxygen from the pore entrance in the water film to the surface of a single platinum nanoparticle is obtained by dividing the concentration difference of the diffusion path by the mass transfer flux of oxygen at different positions in the pore. :

[0080] (11);

[0081] In the formula, is the diffusion resistance of oxygen from the pore entrance to the surface of platinum nanoparticles at different positions in the water film, and its value is , y is the distance between different positions in the pore and the bottom of the pore, is the concentration of oxygen at different locations in the pore, is the oxygen concentration on the water film side of the gas-water interface, is the mass transfer flux of oxygen at different positions in the pore, is the hole depth, , is the diffusion coefficient of oxygen in water, is the adsorption resistance on the surface of a single platinum nanoparticle in the pore, is the roughness factor within the pores.

[0082] For the total resistance due to the adsorption resistance of all Pt nanoparticles in a single pore , which can be obtained by the pore roughness factor To calculate:

[0083] (12);

[0084] In the formula, is the total resistance due to the adsorption resistance of all Pt nanoparticles in a single pore, is the roughness factor in the pores, is the adsorption resistance on the surface of a single Pt nanoparticle in the pore.

[0085] The total diffusion resistance of oxygen in a single pore can then be calculated :

[0086] (13);

[0087] ;

[0088] In the formula, is the total diffusion resistance of oxygen in a single pore, is the roughness factor in the pores, is the adsorption resistance on the surface of a single platinum nanoparticle in the pore, is the hole depth, is the diffusion coefficient of oxygen in water.

[0089] S4. Adsorption resistance of a single platinum nanoparticle through the pore surface and the diffusion resistance of oxygen from the pore entrance to the surface of a single platinum nanoparticle in the water film , the local transport resistance of a single platinum nanoparticle in the pore is obtained ; The total resistance due to the adsorption resistance of all Pt nanoparticles within a single pore and the total diffusion resistance of oxygen in a single pore , to obtain the total resistance of oxygen in a single pore .

[0090] The partition coefficient of oxygen in water get.

[0091] Local transport resistance of a single platinum nanoparticle in a pore :

[0092] (14).

[0093] The total resistance of oxygen in a single pore :

[0094] (15).

[0095] In addition to the calculation method of the resistance, the present invention also provides a verification method for the calculation results. First, the corresponding relationship between the two diffusion resistances. Since the mass transfer flux of oxygen will also change when it is transported from top to bottom in the pore, the definition , It refers to the mass transfer flux of oxygen at the pore entrance, which transfers the local oxygen flux per unit area of ​​platinum nanoparticles to the local oxygen flux per unit area of ​​pore entrance. Figure 4 As shown in the figure, the areas of the two ranges are equal, that is, the relationship between the two diffusion resistances is obtained:

[0096] (16);

[0097] pass After correction Through the integration and Correspondingly, The calculation method and The interoperability of calculation methods ensures the accuracy and reliability of the model.

[0098] In addition, the total resistance in the hole can be calculated by experimental value. Construct a relationship with the formula:

[0099] (17);

[0100] In the formula, x is the adsorption resistance of a single platinum nanoparticle surface in the pore Then, the Iterations are performed, with a maximum of 100 iterations. When the adsorption resistance deviation obtained from two iterations is less than the tolerance of 10 -6 The loop ends when the output x , which can be compared with the adsorption resistance of a single platinum nanoparticle surface in the pore calculated by molecular dynamics. Compare and verify the accuracy and reliability of adsorption resistance calculation. Figure 5 .

[0101] Finally, the diffusion resistance of a single platinum nanoparticle can be obtained by molecular dynamics calculation in equation (3): The diffusion resistance of oxygen from the pore entrance to the surface of a single platinum nanoparticle in the water film calculated by equation (11) A comparison was made to verify the rationality of the calculation method of the pore resistance of mesoporous carbon.

[0102] Based on the above content, the present invention lists the following embodiments.

[0103] Example 1

[0104] A 9.78 nm deep hole was selected, and the initial number of platinum nanoparticles in the hole was 3, which were placed y =1.9nm, 4.7nm and 7.5nm. The temperature is set to 353 K.

[0105] The molecular dynamics method was used to calculate the above three platinum nanoparticles. Both are 14.6s·m -1 .

[0106] The three platinum nanoparticles are calculated by formula (11): They are: 5.12s·m -1 、3.88s·m -1 and 1.89 s·m-1 Then, the three platinum nanoparticles were calculated by equation (14): ,like Figure 6 As shown. As the platinum nanoparticles penetrate deeper, right The contribution of α gradually decreases because the diffusion path of oxygen increases with the pore depth. Increased accordingly.

[0107] Calculated by dichotomy 14.93 s·m -1 , which is highly consistent with the results obtained by molecular dynamics calculations. Figure 7 Compared with the molecular dynamics calculations in equation (3), The calculated value is , it can be seen that the two values ​​are close and can correspond to each other, which illustrates the rationality of the calculation method.

[0108] Example 2

[0109] A pore with a depth of 9.78 nm was selected, and the number of platinum nanoparticles in the pore gradually increased from 1. The temperature was set to 353K.

[0110] Through molecular dynamics and equation (12), the corresponding values ​​of different numbers of platinum nanoparticles in the pore can be calculated. .

[0111] By using equations (13) and (15), we can calculate the corresponding changes in the number of platinum nanoparticles in the pores: and ,like Figure 8 As shown, Figure 8 The small picture in the upper right corner is A magnified view of the curve. It can be seen that as the number of platinum nanoparticles in the pore increases, the oxygen transmission resistance of the entire pore is significantly reduced, and the corresponding adsorption resistance is also significantly reduced. However, the diffusion resistance of the entire pore is only slightly reduced, because it is difficult for oxygen to reach the bottom of the pore. When the number of platinum nanoparticles is large enough, the diffusion resistance of the pore will even exceed the adsorption resistance.

[0112] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, they are also intended to be included.

Claims

1. A method for measuring the mass transfer resistance of a catalyst in the internal pores of mesoporous carbon, characterized in that: The following steps are involved: A microscopic model of water film covering platinum nanoparticles was constructed, and the adsorption resistance on the surface of a single platinum nanoparticle in the pore was obtained based on molecular dynamics simulation; Through the oxygen diffusion equation of the internal pores of mesoporous carbon, the oxygen concentration variation equation of the internal pores of mesoporous carbon and the oxygen mass transfer flux variation equation of the internal pores of mesoporous carbon are obtained; The diffusion resistance of oxygen from the pore entrance in the water film to the surface of a single platinum nanoparticle, the total diffusion resistance of oxygen in a single pore, and the total resistance caused by the adsorption resistance of all platinum nanoparticles in a single pore are obtained through the oxygen concentration variation equation in the pores of the mesoporous carbon and the oxygen mass transfer flux variation equation in the pores of the mesoporous carbon. The local transport resistance of a single platinum nanoparticle in the pore is obtained by the adsorption resistance on the surface of a single platinum nanoparticle in the pore and the diffusion resistance generated by the diffusion of oxygen from the pore entrance in the water film to the surface of a single platinum nanoparticle. The total resistance of oxygen in a single pore is obtained by the total resistance due to the adsorption resistance of all platinum nanoparticles in a single pore and the total diffusion resistance of oxygen diffusion in a single pore.

2. The method for measuring the mass transfer resistance of the catalyst in the internal pores of mesoporous carbon according to claim 1, characterized in that: The microscopic model of water film covering platinum nanoparticles includes, from top to bottom: an oxygen layer composed of oxygen molecules, a water film layer composed of water molecules, platinum nanoparticles composed of platinum molecules, and a graphite carbon layer composed of carbon molecules, wherein the water film layer completely covers the platinum nanoparticles, and oxygen passes through the water film layer to reach the surface of the platinum nanoparticles.

3. The method for measuring the mass transfer resistance of the catalyst in the internal pores of mesoporous carbon according to claim 2, characterized in that: The condensed phase optimized molecular force field used for atomic simulation research is used to calculate the potential energy of all molecules in the microscopic model, the Verle algorithm is used to solve Newton's equations of motion, the particle-particle-particle-mesh method is used to calculate the long-range electrostatic interactions, and the system temperature is controlled by a North-Hoover thermostat. Molecular dynamics simulation is performed in each microscopic model in the canonical ensemble. After the simulation is completed, the mass transfer flux of oxygen on the surface of platinum nanoparticles is calculated, and the adsorption resistance on the surface of a single platinum nanoparticle in the pore is obtained using the mass transfer flux of oxygen on the surface of platinum nanoparticles.

4. The method for measuring the mass transfer resistance of the catalyst in the internal pores of mesoporous carbon according to claim 2, characterized in that: The pores in the graphitic carbon layer are covered with condensed liquid water.

5. The method for measuring the mass transfer resistance of the catalyst in the internal pores of mesoporous carbon according to claim 2, characterized in that: Ignore the non-equilibrium dissolution resistance caused by oxygen dissolving in the water film layer.

6. The method for measuring the mass transfer resistance of the catalyst in the internal pores of mesoporous carbon according to claim 4, characterized in that: The pores in the graphitic carbon layer are considered as straight holes with equal cross-section.

7. The method for measuring the mass transfer resistance of the catalyst in the internal pores of mesoporous carbon according to claim 1, characterized in that: The oxygen diffusion equation in the pores of mesoporous carbon is: ； ； Where y is the distance between different positions in the pore and the bottom of the pore, is the mass transfer flux of oxygen at different positions in the pore, is the current density at different positions in the pore, F is the Faraday constant, is the diffusion coefficient of oxygen in water, is the concentration of oxygen at different locations in the pore.

8. The method for measuring the mass transfer resistance of catalyst in the internal pores of mesoporous carbon according to claim 1, characterized in that: The equation for the change of oxygen concentration in the pores of mesoporous carbon is: ； ； In the formula, is the concentration of oxygen at different locations in the pore, is the oxygen concentration on the water film side of the gas-water interface, is the pore depth, y is the distance between different positions in the pore and the bottom of the pore, is the diffusion coefficient of oxygen in water, is the adsorption resistance on the surface of a single platinum nanoparticle in the pore, is the roughness factor within the pores.

9. The method for measuring the mass transfer resistance of catalyst in the internal pores of mesoporous carbon according to claim 8, characterized in that: The oxygen mass transfer flux variation equation of the internal pores of mesoporous carbon is: ； In the formula, is the mass transfer flux of oxygen at different positions in the pore.

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