On-line measurement method for resistivity of ion resin

Abstract

The invention discloses an on-line measurement method for the resistivity of ion resin. And spraying an ion resin solution on the proton membrane layer by layer by using the supporting effect of the proton membrane, and further preparing a membrane electrode for online measurement of high-frequency impedance. And the resistivity of the ion resin is calculated by controlling the thickness of the sprayed resin layer, so that the problem of online measurement of the resistivity of the ion resin is solved. The purpose of simply, conveniently and accurately evaluating the conductivity of the ion resin dispersion is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogen production by water electrolysis and fuel cell, and particularly relates to an on-line measurement method of ion resin resistivity. BACKGROUND

[0002] At present, CCM technology is commonly used in the membrane electrode of PEM hydrogen production electrolyzer and proton exchange membrane fuel cell. The CCM is a composite thin film component composed of a cathode catalyst layer, a proton exchange membrane and an anode catalyst layer. The proton exchange membrane is composed of ion resin, and the cathode and anode catalyst layers are both composed of ion resin and catalyst. In the CCM, the ion resin plays a role in conducting protons, so analyzing the proton conduction capacity of the ion resin is important for improving the performance of the cell. The proton exchange membrane has a single composition, a flat shape and a tough and solid texture, so the measurement of the proton resistance of the proton exchange membrane is relatively simple, and a national standard has been issued. However, in the catalyst layer, the catalyst layer is formed by coating the mixed slurry of ion resin solution and catalyst, so after the catalyst layer is dried and formed, the ion resin and the catalyst particles (electron conductor) are in a random mixed state, and the measurement of the proton resistivity is interfered by the electron resistance and the interface capacitance at the same time, so it is very difficult to implement. At present, there are mainly two methods for evaluating the ion resin resistance characteristics of the catalyst layer. First, the ion resin solution used for the catalyst layer is recast into a film, and the evaluation method of the proton exchange membrane is used for the measurement. The recast film can be used for off-line resistivity measurement, but due to its low strength and complex film forming process, it is difficult to measure on-line in the cell, which limits further research. Second, hydrogen-nitrogen impedance spectrum is used for on-line measurement, and the ion resistance of the catalyst layer is calculated through the fitting of the equivalent circuit. The fitting of the equivalent circuit is based on the “transmission line model”, and the uniformity in the thickness direction of the electrode is required to be high. With the current development trend of thinning the catalyst layer, the size effect of the raw material poses a great challenge to the uniformity, and the actual results deviate from the model, so it is difficult to measure the standard line, and therefore a large error is introduced. SUMMARY

[0003] In view of this, the purpose of the present application is to provide an on-line measurement method of ion resin resistivity for evaluating the conductive characteristics of ion resin in PEM electrolyzer and fuel cell. The on-line measurement method of ion resin resistivity provided by the present application uses the support of the proton membrane to composite the ion resin to be measured in the form of a thin film inside the fuel cell, and obtains the proton conduction performance of the ion resin for the catalyst layer in the actual cell environment through on-line measurement.

[0004] The technical scheme of the present application is as follows:

[0005] An on-line measurement method of ion resin resistivity, comprising the following steps:

[0006] S1, spray ion resin solution on the surface of the plurality of proton membranes, respectively, by controlling the spraying amount, and after drying, obtain a plurality of proton membranes with different thickness of ion resin attached layer;

[0007] S2, prepare each proton membrane into a membrane electrode, respectively;

[0008] S3, assemble each membrane electrode into a single cell, respectively, and perform high-frequency impedance test to obtain a plurality of different impedance values;

[0009] S4, linearly fit the impedance values with the thickness of the ion resin attached layer to obtain the slope and intercept;

[0010] S5, calculate the resistivity and interface resistance of the ion resin attached layer according to the intercept and slope, wherein:

[0011] ρ = a × S;

[0012] r = (b - R mem ) × S;

[0013] ρ: resistivity of the ion resin attached layer; a: slope; S: cell area; b: intercept; R mem : proton membrane body resistance.

[0014] In step S1, there are three groups of proton membranes with different thickness of ion resin attached layer, and the thicknesses are 2-5um, 8-10um and 15-20um, respectively.

[0015] In step S3, the test conditions are: cell temperature 60-80℃; relative humidity 40-100%; pressure 100-150kPa abs ; cell current constant at 1A cm -2 .

[0016] The preparation method of the ion resin solution in step S1 includes the following steps: diluting the ion resin with a diluent to an ion resin solution with a mass concentration of 1%-10%; the diluent includes water-NPA.

[0017] In step S1, the ion resin includes a short-chain ion resin with EW between 600-900, or a long-chain ion resin with EW between 1000-1100.

[0018] In step S2, the assembly method of the membrane electrode includes the following steps:

[0019] The proton membrane with ion resin attached layer is respectively compounded with cathode catalyst layer and anode catalyst layer on both sides to form a membrane electrode, wherein the cathode catalyst layer is arranged close to the ion resin attached layer.

[0020] The cathode catalyst layer is a thin layer composed of ion resin and catalyst, and the platinum loading is 0.1-0.4mg / cm2 .

[0021] In the cathode catalytic layer, the ion resin is perfluorosulfonic acid resin, and the catalyst is platinum carbon catalyst; the platinum loading is 0.1-0.4 mg / cm.

[0022] The anode catalytic layer is a thin layer composed of ion resin and catalyst, and the platinum loading is 0.05-0.1 mg / cm 2 .

[0023] In the anode catalytic layer, the ion resin is perfluorosulfonic acid resin, and the catalyst is platinum carbon catalyst, and the platinum loading is 0.05-0.1 mg / cm 2 .

[0024] The application of the ion resin resistivity on-line measurement method in the fuel cell also belongs to the protection scope of the present application.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] 1. The present application designs an ion resin resistivity on-line measurement method, which can be directly implemented in a fuel cell, and reflects the state of the ion resin in a real cell environment;

[0027] 2. The present application designs an ion resin resistivity direct measurement method, which does not involve equivalent circuit fitting of hydrogen nitrogen impedance spectrum, reduces the requirements for samples, simplifies the measurement procedure, and improves the success rate of data;

[0028] 3. The present application can also measure the interface resistance of the ion resin in the proton exchange membrane and the catalytic layer. BRIEF DESCRIPTION OF DRAWINGS

[0029] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the accompanying drawings:

[0030] Figure 1 is a structural schematic diagram of a proton membrane;

[0031] Figure 2 is a structural schematic diagram of a membrane electrode. DETAILED DESCRIPTION

[0032] The present application will be described in detail below with reference to the embodiments. The following embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be pointed out that, for those skilled in the art, without departing from the concept of the present application, a number of adjustments and improvements can be made. These all belong to the protection scope of the present application.

[0033] In the following examples:

[0034] The membrane electrode in the technical solution of the present application has a structure of one proton membrane and two catalytic layers, and the catalytic layers are carried on both sides of the proton membrane.

[0035] Figure 1 The structure of the proton membrane is shown in the schematic diagram.

[0036] Figure 2 The structure of the membrane electrode is shown in the schematic diagram.

[0037] The cathode catalytic layer is a thin layer composed of an ion resin and a catalyst, the ion resin is a perfluorosulfonic acid resin, and the catalyst is a platinum-carbon catalyst; the platinum loading is 0.1-0.4 mg / cm 2 .

[0038] The anode catalytic layer is a thin layer composed of an ion resin and a catalyst, and the platinum loading is 0.05-0.1 mg / cm 2 .

[0039] The ion resin information is as follows:

[0040]

[0041]

[0042] Preparation Example 1 Membrane Electrode A

[0043] S1, take No. 1 ion resin, dilute the water-NPA mixed solution (1:1 by vol.) to 1% concentration (mass fraction) to prepare No. 1 ion resin solution;

[0044] S2, spray No. 1 resin solution on Gore M765.08 type proton membranes respectively and dry to form ion resin attached layer proton membranes; spray three groups of samples respectively, control the spraying amount to make the ion resin attached layer thickness of the three groups of samples reach 5 um, 10 um and 15 um respectively, and each group of samples is repeated three times;

[0045] S3, assemble the membrane electrode by using a thermal compounding process; the assembly method is as follows:

[0046] Compound the cathode catalytic layer and the anode catalytic layer on both sides of each sample to make three groups of membrane electrodes, and the active area is 25 cm 2 , wherein the cathode catalytic layer is close to the ion resin attached layer.

[0047] Preparation Example 2 Membrane Electrode B

[0048] S1, take No. 2 ion resin, dilute the water-NPA mixed solution (1:1 by vol.) to 1% concentration (mass fraction) to prepare No. 2 ion resin solution;

[0049] S2, spray the No. 2 resin solution on the Gore M765.08 type proton membrane respectively and dry to form an ion resin attached layer of the proton membrane; spray three groups of samples respectively, and by controlling the spraying amount, the ion resin attached layer thickness of the three groups of samples is respectively 5 um, 10 um and 15 um, and each group of samples is repeated three times;

[0050] S3, assemble the membrane electrode by using a thermal compounding process; the assembly method is as follows:

[0051] Compound the cathode catalytic layer and the anode catalytic layer on both sides of each sample to make three groups of membrane electrodes, and the active area is 25 cm 2 , wherein the cathode catalytic layer is close to the ion resin attached layer.

[0052] Example 1

[0053] A method for online measuring the ion resin conductivity is provided, comprising the following steps

[0054] 1. Assemble the membrane electrode prepared in Preparation Examples 1 and 2 with the gas diffusion layer, the flow field plate, the current collector plate and the fixed assembly into a fuel cell, and after activation, maintain the cell at a current density of 1 A / cm 2 , test the high frequency resistance HFR of the cell; the HFR value can be directly read from the fixed frequency hydrogen-air impedance, and there is no requirement for the impedance spectrum line shape;

[0055] Test conditions:

[0056] The cell temperature is 80℃, the relative humidity is 100%, and the pressure is 150 kPa abs ;

[0057] After activation of the membrane electrode, the cell current is kept at 1 A cm -2 , and the HFR is recorded

[0058] 2. Make a linear graph of the high frequency resistance results of the membrane electrode prepared in Preparation Examples 1 and 2 and the thickness of the ion resin attached layer thereof, to obtain the intercept and slope of the fitting straight line;

[0059] 3. Calculate the resistivity and interface resistance of the ion resin attached layer according to the intercept and slope; wherein the slope a multiplied by the cell area S is the resistivity p of the attached resin layer; after the intercept b is subtracted from the proton membrane body resistance R mem , multiplied by the cell area S, it is equal to the interface resistance r of the resin layer / proton membrane. The proton membrane body resistance R mem is the high frequency resistance value of the pure proton membrane (3) without the attached resin layer. Figure 2

[0060] p = a x S;

[0061] r = (b - R mem ​)×S;

[0062] ρ: Resistivity of the additional resin layer;

[0063] a: slope;

[0064] S: Battery area;

[0065] b: intercept;

[0066] R mem : Proton membrane bulk resistance;

[0067] The test results are shown in Table 1.

[0068] Table 1

[0069] Slope a Intercept b Resistivity p Interface resistance r mohm pm -1 ]]> mohm mohm cm mohmcm 2 ]]> Preparation Example 1 0.037 2.07 9.14 x 10 6 ]]> 6.77 Preparation Example 2 0.078 2.01 1.96x10 7 ]]> 5.13

[0070] Example 2

[0071] 1. The membrane electrode prepared in Examples 1 and 2 were assembled into fuel cells with a gas diffusion layer, a flow field plate, a current collector, and a stationary assembly, respectively. After activation, the cell was maintained at 1 A / cm. 2 The current density is used to test the high-frequency impedance of the battery; the HFR (high-frequency impedance) value can be directly read from the fixed-frequency hydrogen-air impedance, and there are no requirements for the impedance spectrum shape.

[0072] Test conditions:

[0073] Battery temperature 80℃; relative humidity 40%; pressure 150kPa abs ;

[0074] After activating the membrane electrode, the battery current is kept constant at 1 A cm⁻¹. -2 Record HFR;

[0075] 2. Plot a linear relationship between the high-frequency impedance results of the membrane electrodes prepared in Examples 1 and 2 and the thickness of their ion exchange resin coating to obtain the intercept and slope of the fitted line.

[0076] 3. Calculate the resistivity and interfacial resistance of the ion exchange resin layer based on the intercept and slope. The resistivity ρ of the additional resin layer is obtained by multiplying the slope a by the cell area S; the resistivity R of the proton exchange membrane is obtained by subtracting the intercept b from the intercept. mem Then, multiply by the battery area S, which equals the resin layer / proton exchange membrane interface resistance r. The proton exchange membrane bulk resistance R... mem That is, a pure proton membrane without an additional resin layer ( Figure 2 The high-frequency impedance value of 3) in the figure.

[0077] ρ = a × S;

[0078] r=(bR mem )×S;

[0079] p: resistivity of the additional resin layer;

[0080] a: slope;

[0081] S: battery area;

[0082] b: intercept;

[0083] R mem： Proton membrane bulk resistance

[0084] Test results Table 2

[0085] Table 2

[0086]

[0087] The specific embodiments of the present application have been described. It is to be understood that the application is not limited to the specific embodiments described above and various modifications or changes can be made by those skilled in the art without departing from the spirit and scope of the application as defined in the claims.

Claims

1. An online method for measuring the resistivity of ion exchange resin, characterized in that, Includes the following steps: S1. Spray ion exchange resin solution onto the surface of multiple proton exchange membranes respectively. By controlling the amount of spraying, multiple sets of proton exchange membranes with ion exchange resin coatings of different thicknesses are obtained after drying. S2. Prepare membrane electrodes from each proton membrane; S3. Assemble each membrane electrode into a single cell and perform high-frequency impedance testing to obtain multiple sets of different impedance values. S4. Linearly fit the impedance value with the thickness of the ion exchange resin coating to obtain the slope and intercept. S5. Calculate the resistivity and interfacial resistance of the ion-exchange resin coating based on the intercept and slope, where: ρ = a × S; r=(b-R mem )×S; ρ: Resistivity of the ion-exchange resin coating; a: Slope; S: Cell area; b: Intercept; R mem : Proton membrane bulk resistance.

2. The online measurement method for the resistivity of ion exchange resin according to claim 1, characterized in that, In step S1, there are three sets of proton exchange membranes with ion exchange resin coatings of different thicknesses, namely 2-5 μm, 8-10 μm, and 15-20 μm.

3. The online measurement method for the resistivity of ion exchange resin according to claim 1, characterized in that, In step S3, the test conditions for high-frequency impedance are: battery temperature 60-80℃; relative humidity 40-100%; pressure 100-150kPa. abs The battery current remains constant at 1A cm. -2 .

4. The online measurement method for the resistivity of ion exchange resin according to claim 1, characterized in that, The preparation method of the ion exchange resin solution in step S1 includes the following steps: The ion exchange resin is diluted with a diluent to a mass concentration of 1%-10% to form an ion exchange resin solution; the diluent includes water-NPA.

5. The online measurement method for the resistivity of ion exchange resin according to claim 1, characterized in that, In step S1, the ion exchange resin includes a short-chain ion exchange resin with an EW between 600 and 900, or a long-chain ion exchange resin with an EW between 1000 and 1100.

6. The online measurement method for the resistivity of ion exchange resin according to claim 1, characterized in that, In step S2, the assembly of the membrane electrode includes the following steps: A membrane electrode is formed by bonding a cathode catalytic layer and an anode catalytic layer to both sides of a proton exchange membrane with an ion exchange resin coating, wherein the cathode catalytic layer is attached to the ion exchange resin coating.

7. The online measurement method for the resistivity of ion exchange resin according to claim 6, characterized in that, The cathode catalyst layer is a thin layer composed of ion exchange resin and catalyst, with a platinum loading of 0.1-0.4 mg / cm³. 2 .

8. The online measurement method for the resistivity of ion exchange resin according to claim 6, characterized in that, The anode catalyst layer is a thin layer composed of ion exchange resin and catalyst, with a platinum loading of 0.05-0.1 mg / cm³. 2 .

9. The application of the online measurement method for the resistivity of ion exchange resin as described in any one of claims 1-8 in fuel cells.

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