CN203164294U - Apparatus for testing conductivity and membrane electrode impedance of power material - Google Patents

Abstract

The utility model relates to an apparatus for testing conductivity and membrane electrode impedance of a power material, wherein the apparatus can meet requirements of two kinds of measurement modes. In the terms of the measurement mode for conductivity of the powder material, a prepared tested powder press block sample is placed in a small tested sample chamber; a die is assembled to carry out testing, thereby respectively obtaining the electron impedance and the total impedance of the powder; an impedance parallel connection formula is combined to obtain proton impedance; and the electron conductivity, the proton conductivity, and the total conductivity are obtained by calculation. And in the terms of the measurement mode for membrane electrode impedance, a prepared tested membrane electrode sample is placed in a small tested sample chamber; and a die is assembled to carry out testing, thereby obtaining the impedance of the membrane electrode. According to the utility model, the testing apparatus is configured with a temperature controlling casing tube and a humidification pipeline. The conductivity and the membrane electrode impedance of the powder material in different temperature and humidity environments can be tested. The apparatus with the simple structure is easy to operate; and the measurement result is precise. Moreover, the testing apparatus is suitable for conductivity testing of a mixed charged powder material and membrane electrode impedance testing in a simulated PEM water electrolytic tank environment; and thus the feasibility, the essentiality and the importance of the device are highlighted.

Description

A testing device for the electrical conductivity of powder materials and the impedance of membrane electrodes

technical field

The utility model relates to a device for testing the properties of materials, in particular to a device for testing the conductivity of powder materials and the impedance of membrane electrodes.

Background technique

At present, mixed charged powder materials with both electron and proton conductivity, because they can significantly optimize the electron and proton channel transport capabilities of proton exchange membrane fuel cells and water electrolysis cell membrane electrodes, and then improve the interface reaction characteristics, have been widely studied by many researchers. Used for catalytic layer modification materials and catalyst carrier materials. Among them, the measurement of the electronic and proton conductivity properties of powder materials is an indispensable physical parameter in the process of evaluating the application of powder materials. Therefore, it is extremely critical to optimize the selection of catalytic materials and the preparation process of membrane electrodes through conductivity testing to improve the performance of proton exchange membrane fuel cells or water electrolysis cells.

At present, the methods for testing the conductivity of powder materials mainly include the compact method and the four-probe method. In the results published in the "Journal of East China University of Science and Technology", Qin Changyong et al. added ATO powder into the cavity of the tablet press and formed it under a certain pressure to obtain a compact. Then, the resistance value at both ends of the compact was measured by a multimeter, and the powder Bulk conductivity, this method is easy to operate, but the error is large, and the ionic conductivity of the mixed charged powder material cannot be measured; Chen Weizhong et al. in their invention patent (application number: 200810216653. The tablet press was compacted, and the test device was connected after the metal powder was coated on both sides of the compact. The electronic and ion conductivity of the mixed charged powder material was obtained by the DC shunt method and the AC impedance method. The metal powder reduced the compaction. The contact resistance with the wire, this method has a high test accuracy, but it cannot measure the electronic and ionic conductivity characteristics of the mixed charged powder material at different temperatures and humidity. In addition, the membrane electrode prepared by mixing charged powder materials has both electron conduction and proton conductivity, and its thickness is about 70-200 μm, which requires high test accuracy, and temperature and humidity have a great impact on the impedance of the membrane electrode. The influence makes the measurement of membrane electrode impedance more difficult. Most researchers test the membrane electrode impedance in a single cell. The three-electrode method is used to test the AC impedance of the working electrode, and the electron and proton impedance obtained by the equivalent circuit fitting have large errors. Because the impedance value includes the line, the salt bridge to the electrolyte resistance of the working electrode, etc., not only the test process is complicated, but also a lot of material waste is caused, and the test cost is high.

Based on the work of many researchers,

Contents of the invention

The purpose of the utility model is to solve many problems existing in the impedance test of the conductivity of the powder material and the prepared membrane electrode, and provide a device and method for testing the conductivity of the electron and proton of the powder material and the membrane electrode prepared therefrom. The utility model obtains the electron and proton conductivity of the powder material and the impedance of the membrane electrode prepared by the designed mold and the electrochemical workstation. Moreover, the sample preparation steps are simple, the error is small, and it can more truly reflect the electron and proton conductivity of different catalytic materials under different temperature and humidity conditions.

The technical solution of the utility model is: a testing device for the conductivity of powder materials and the impedance of membrane electrodes, the device includes an upper pressing rod, an upper fastening screw, a temperature control sleeve, a base and a lower fastening screw;

The upper end of the upper pressure rod is provided with an upper terminal, the lower end of the upper pressure rod is inserted into the temperature control sleeve, and the upper pressure rod and the temperature control sleeve are fixed by the upper fastening screw , the contact part between the upper pressure rod and the temperature control sleeve is provided with a polytetrafluoroethylene sleeve for insulation;

One side of the lower base is provided with a lower terminal, and the lower base and the temperature control sleeve are fixed by the lower fastening screw;

The upper pressing rod is provided with an upper humidifying passage for the inlet and outlet of water vapor, and the lower base is provided with a lower humidification passage for the inlet and outlet of water vapor.

Further, the material of the upper pressing rod, the upper fastening screw, the temperature control sleeve, the base and the lower fastening screw is annealed 316L stainless steel, carbon steel, bearing steel or chromium 12 material.

The beneficial effects of the utility model are: due to the adoption of the above technical scheme, the device for testing the conductivity of the powder material and the impedance of the prepared membrane electrode provided by the utility model can test the electrons and protons of the powder material at different temperatures and humidity. Conductivity and membrane electrode impedance, the test operation is simple and easy to master; on the basis of obtaining high-precision test results, the test process does not use large-scale sophisticated and complex equipment, and the cost is low.

Description of drawings

Fig. 1a is a schematic cross-sectional view of the application of the measurement device of the present invention to measure the mixed conductivity of electrons and protons.

Fig. 1b is a schematic cross-sectional view of the application of the test membrane electrode of the measuring device of the present invention.       

Fig. 2 is a schematic diagram of the sandwich structure of the mixed conductive powder briquettes of tested electrons and protons.

Figure 3 is a schematic diagram of the sandwich structure of the tested membrane electrode.

Fig. 4a is a simulated equivalent circuit diagram of an AC impedance test in a specific embodiment of the present invention.

Fig. 4b is a simplified diagram of an analog equivalent circuit of an AC impedance test in a specific embodiment of the present invention.

FIG. 5 is the conductivity data of ATO powder at different temperatures obtained according to the powder conductivity measurement mode of Example 1. FIG.

Fig. 6 is the electrical conductivity data of the mixed charged powder material ATO-SnP ₂ O ₇ powder obtained under different conditions according to the powder electrical conductivity measurement mode of Example 2.

Accompanying drawing 7 is the impedance data of membrane electrodes prepared by different mixed charged powders obtained according to the membrane electrode impedance measurement mode of Example 3.

In the figure: 1: upper pressure rod, 2: upper terminal, 3: fastening screw, 4: temperature control sleeve, 5: PTFE sleeve, 6: upper humidification channel, 7: powder to be tested Press block, 8: lower humidification channel, 9: lower terminal, 10: base, 11: lower fastening screw, 12: membrane electrode to be tested, 71: upper stainless steel mesh, 72: mixed conductive powder of electron and proton to be tested Body compact, 73: lower stainless steel mesh, 121: carbon paper, 122: anode catalytic layer, 123: Nafion membrane, 124: cathode catalytic layer, 125: carbon paper.

Detailed ways

Below in conjunction with accompanying drawing and example the utility model is described in further detail.

As shown in Figure 1a and Figure 1b, the utility model is a test device for the conductivity of powder materials and the impedance of membrane electrodes. The device includes an upper pressing rod 1, an upper fastening screw 3, a temperature control sleeve 4, a base 10 and Lower fastening screw 11;

The upper end of the upper pressure rod 1 is provided with an upper terminal 2, the lower end of the upper pressure rod 1 is inserted into the temperature control sleeve 4, and the upper pressure rod 1 and the temperature control sleeve 4 pass through The upper fastening screw 3 is fixed, and the contact part of the upper pressing rod 1 and the temperature control sleeve 4 is provided with a polytetrafluoroethylene sleeve 5 for insulation;

One side of the lower base 10 is provided with a lower terminal 9, and the lower base 10 and the temperature control sleeve 4 are fixed by the lower fastening screw 11;

The upper pressing rod 1 is provided with an upper humidification channel 6 for the inlet and outlet of water vapor, and the lower base 10 is provided with a lower humidification channel 8 for the inlet and outlet of water vapor.

，计算可得粉体材料电子电导率以及总电导率（电子电导率与质子电导率共同影响），其中

为电子电导率或总电导率，L为压片厚度，R为电阻，S为压片面积。上述的总阻抗等效于混合荷电粉体材料中电子、质子传导引起阻抗的并联总阻抗，其等效电路可以参照附图4a，其中R_int、R_i、R_e分别为界面阻抗、电子传导引起阻抗、质子传导引起阻抗，W为Warburg阻抗、C_cell为空间几何电容，C_int为界面电容。由于阻抗测试过程没有电化学反应以及界面阻抗和界面电容为定值，等效电路可以简化为附图4b，总阻抗、电子阻抗、质子阻抗的关系可通过等效电阻公式表示，其中电子阻抗、总阻抗分别可通过直流极化曲线测试与交流阻抗测试获得。 The utility model provides a device for testing the electron and proton conductivity of powder materials and the impedance of the prepared membrane electrode. The powder material or the prepared membrane electrode is placed in the sample chamber to be tested, connected to an electrochemical workstation, and then polarized by direct current. Curve test and AC impedance test respectively obtain the impedance caused by electron conduction and the total impedance caused by electron and proton conduction, and according to the conductivity formula

, the electronic conductivity and the total conductivity of the powder material can be calculated (the electronic conductivity and the proton conductivity are jointly affected), where

is the electronic conductivity or total conductivity, L is the thickness of the tablet, R is the resistance, and S is the area of the tablet. The above-mentioned total impedance is equivalent to the parallel total impedance of the impedance _caused by _electron and _proton conduction in the mixed charged powder material. Impedance caused by conduction, impedance caused by proton conduction, W is Warburg impedance, C _cell is space geometry capacitance, C _int is interface capacitance. Since there is no electrochemical reaction in the impedance test process and the interface impedance and interface capacitance are fixed values, the equivalent circuit can be simplified to Figure 4b, and the relationship between total impedance, electronic impedance, and proton impedance can be expressed by the equivalent resistance formula , where the electronic impedance and the total impedance can be obtained by the DC polarization curve test and the AC impedance test respectively.

Example 1

Grind the ATO powder material with electronic conductivity, obtain a certain particle size powder conductive material with a 200-mesh sieve, weigh 0.5 g, dry it in a vacuum oven at 80 °C for 12 h, and briquette.

Then, the dried ATO powder material was placed in a commercial briquetting machine to prepare briquettes, the diameter of the briquettes was 10 mm, and the thickness of the briquettes was measured by a vernier caliper.

Take out the briquetting block, assemble the porous stainless steel mesh-briquetting block 7-stainless steel mesh according to Figure 2, and obtain the tested sample with a sandwich structure. As shown in Figure 1a, it is placed in the sample chamber which is composed of the upper pressing rod 1, the base 10 and the temperature control sleeve 4, and the pressing block 7 is compressed by the upper fastening screw 2 and the lower fastening screw 11, The torque of each screw is 1 N m.

The test temperature of the sample chamber can be controlled through the temperature control sleeve 4; the humidity of the sample chamber can be controlled through the humidification channel 6 and the lower humidification channel 8;

Connect the upper terminal 2 and the lower terminal 9 to the VMP2 electrochemical workstation in a two-electrode manner, conduct a DC polarization curve test, obtain its electronic impedance R _e by measuring the relationship between the current and the voltage, and then combine the thickness L of the compact, the thickness of the compact The area S on the surface, according to the conductivity calculation formula Calculate the electronic conductivity of the powder, and finally obtain the electronic conductivity of the ATO powder material at different temperatures.

The voltage range of the DC polarization curve test process is 0-10 V, and the response current range is 0-2 A.

As shown in Figure 5, the electrical conductivity of the ATO powder material at different temperatures is obtained by controlling the temperature through the temperature control sleeve. It can be found that the electrical conductivity of the ATO powder material does not change as the temperature increases. This is because ATO is electron Conductive phase, little affected by temperature.

Example 2

The test material is replaced with ATO-SnP ₂ O ₇ mixed charged powder material with both electronic and proton conductivity, the powder material is ground, and a certain particle size powder material is obtained with a 200-mesh sieve, weighing 0.5 g Place it in a vacuum oven at 80 °C for 12 h and wait for briquetting.

The dried ATO-SnP ₂ O ₇ powder material was placed in a commercial briquetting machine to prepare briquettes with a diameter of 10 mm, and the thickness of the briquettes was measured by a vernier caliper.

Take out the briquetting block, assemble the porous stainless steel mesh-briquetting block-stainless steel mesh according to Figure 2, and obtain the tested sample with a sandwich structure. As shown in Figure 1a, it is placed in the sample chamber which is composed of the upper pressing rod 1, the base 10 and the temperature control sleeve 4, and the pressing block 7 is pressed by the upper fastening screw 2 and the lower fastening screw 11 Compression is performed with a torque of 1 N m for each screw.

The test temperature of the sample chamber can be controlled through the temperature control sleeve 4; the humidity of the sample chamber can be controlled through the humidification channel 6 and the lower humidification channel 8;

Connect the upper terminal 2 and the lower terminal 9 to the VMP2 electrochemical workstation in a two-electrode manner, measure the electronic impedance and total impedance through the DC polarization curve test and the AC impedance test, and then combine the thickness of the compact and the cross-sectional area of the compact, according to The equivalent resistance formula is used to calculate the proton impedance, and finally the total conductivity, electron and proton conductivity of the ATO-SnP ₂ O ₇ powder material at different temperatures and humidity.

The voltage range of the DC polarization curve test process is 0-10 V, and the response current range is 0-2 A.

The condition of AC impedance test is that its frequency range is 10 Hz-100 KHz and its amplitude is 10 mV.

It can be found from accompanying drawing 6 that for the mixed charged powder material, temperature and humidity have a great influence on its total conductivity, which is mainly because the conductivity of the proton-conducting phase in the mixed charged powder material increases with the increase of temperature. Large, the conductivity of the proton-conducting phase increases in a humidified environment, which in turn leads to an increase in the total conductivity. Expressed by the _equivalent resistance formula 1/R = 1/R _i + 1/R _e calculation, table 1 shows the proton conductivity, electronic conductivity, and total conductivity of the powder materials measured in accompanying drawing 6 under different test conditions data.

Table 1

The doping ratio of SnP ₂ O ₇ in ATO-SnP ₂ O ₇ is 20%:

Example 3

In this example, the catalysts IrO ₂ /ATO and IrO ₂ /Cs _1.5 HWA–ATO are used to prepare membrane electrodes, and the specific methods are as follows:

First, the above-mentioned catalyst and 5% PTFE emulsion are mixed in a certain volume of isopropanol in a certain proportion, and the spray slurry is obtained after hundreds of times of ultrasonication in an ice bath, and then the PTFE film is used as the substrate, and the catalytic layer is prepared by heating and spraying. As shown in accompanying drawing 3, finally, the PTFE film with the anode catalytic layer 142, the Nafion membrane 143, and the PTFE film with the cathode catalytic layer 144 are hot-pressed at a pressure of 750 N cm ^-2 at a temperature of 135°C, and the PTFE film is peeled off to obtain The measured membrane electrode. Among them, MEA-1 and MEA-2 are membrane electrodes prepared by IrO ₂ /ATO and IrO ₂ /Cs _1.5 HWA-ATO catalysts, respectively.

Claims (2)

1. The proving installation of a kind of electrical conductivity of powdered material and membrane electrode impedance is characterized in that, this device comprisesUpperpush rod (1), tighten screw rod (3), temperature control sleeve pipe (4), base (10) and following fastening screw (11);

Upper end one side of described upperpush rod (1) is provided with binding post (2), insert in the described temperature control sleeve pipe (4) lower end of described upperpush rod (1), described upperpush rod (1) is fixed by the described screw rod (3) that tightens with described temperature control sleeve pipe (4), and the teflon sleeve (5) of insulating effect is played in described upperpush rod (1) and described temperature control sleeve pipe (4) contact portion setting;

One side of described lower end base (10) is provided with down binding post (9), and described lower end base (10) is fixed by described fastening screw (11) down with described temperature control sleeve pipe (4);

Described upperpush rod (1) is provided with for adding wet channel (6) on the inlet and outlet piping of water vapor, and described lower end base (10) is provided with the following wet channel (8) that adds for the inlet and outlet piping of water vapor.

2. proving installation as claimed in claim 1, it is characterized in that, described upperpush rod (1), tighten screw rod (3), temperature control sleeve pipe (4), base (10) and following fastening screw (11) material for through the 316L of annealing in process stainless steel, carbon steel, bearing steel or chromium 12 materials.

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