GB/T 20042.4-2009Proton exchange membrane fuel cell - Part 4: Test method for electrocatalysts (English PDF)

4.2

Pt content test by ICP (inductively coupled plasma spectroscopy) method

The test is performed in accordance with the method as specified in GB/T 15072.7-2008.

4.2.1 Scope of application

This method is suitable for testing Pt content in Pt/C catalysts and Pt alloy catalysts.

4.2.2 Test instruments and equipment

4.2.2.1 Ion-coupled emission spectrometry (ICP)

The minimum detection limit is <= 1 µg/L.

4.2.2.2 Analytical balance

The precision is 0.1 mg.

4.2.2.3 Caliper

The measurement precision is 0.01 mm.

4.2.3 Sample preparation

The sample mass is not less than 2 g.

The sample is placed in a vacuum oven and dried at 80 °C for 12 h.

4.2.4 Reagents and materials

4.2.4.1

Concentrated sulfuric acid (98%), guaranteed reagent.

4.2.4.2

Concentrated hydrochloric acid (37%), guaranteed reagent.

4.2.4.3

Concentrated nitric acid (68%), guaranteed reagent.

4.2.4.4

Secondary distilled water, resistivity >= 18.2 Mohm · cm.

4.2.4.6

Corundum crucible with cover.

4.2.5 Test method

C - Smooth Pt surface adsorption hydrogen peroxide adsorption constant, in

0.21 millicoulombs per square centimeter (0.21 mC/cm2);

v - Scanning speed, in millivolts per second (mV/s);

M - The mass of Pt on the electrode, in grams (g).

TAKE 3 samples as a group, CALCULATE the average value as the test result.

6 Specific surface area, pore volume, pore size distribution test

The test is performed in accordance with the method as specified in GB/T 5816-

1995.

6.1 Instruments and gases

6.1.1

Fully automatic physical adsorption instrument.

6.1.2 Analytical balance

the precision is 0.01 mg.

6.1.3 Test gas

The oil-free high-purity nitrogen gas and helium gas after drying, the purity is not less than 99.999%.

6.2 Test methods

The static nitrogen adsorption capacity method is used to measure the volume of nitrogen adsorbed by the catalyst at different low pressures. At least four test points satisfying the BET linear relationship are measured, and the surface area is calculated using the BET two-parameter equation.

6.2.1 Sample pretreatment and degassing

a) In accordance with the degassing requirements, PLUG the empty sample tube after degassing treatment to weigh it, accurate to 0.01 mg. At this point the mass is recorded as m1;

b) TAKE the appropriate amount of sample and ADD it into the sample tube.

SET the heating temperature (generally less than 200 °C) to heat the sample and EMPTY it. When the heating temperature reaches the set temperature and the system vacuum reaches 1.3 Pa, CONTINUE degassing for at least 4 hours. It is allowed for the sample to be degassed overnight;

c) COOL the degassed sample tube to room temperature, ADD plug to weigh it, accurate to 0.01 mg. This mass is recorded as m2, and the difference to 0.1 mg.

9.3.2

USE a test funnel, POUR a certain amount of sample into the measuring cylinder within 20 s ~ 25 s. The sample volume must exceed the amount required to fill the measurement cylinder full. During the pour-in process, USE a rod to gently knock the measuring cylinder wall at the frequency of 2 ~ 3 times per second, to make the sample compact. If the sample flow is not smooth, it may use a glass rod with a diameter of about 4 mm to clean the funnel discharge port to make it unblocked.

9.3.3

CLOSE the funnel, then RAISE the measuring cylinder by 2 mm ~ 3 mm,

LET it fall down to further compress the sample, REPEAT this operation for 20 times, READ out the sample volume (mL).

9.3.4

WEIGH the total mass of the measuring cylinder and the sample,

RECORD it as M2, accurate to 0.1 mg.

9.4 Data processing

CALCULATE the stack density of the sample in accordance with the formula (10).

Where.

rho - The stack density of the sample, in grams per milliliter or grams per cubic centimeter (g/mL or g/cm3);

M2 - The total mass of the measuring cylinder and the sample, in grams (g);

M1 - The mass of the measuring cylinder, in grams (g);

V - The volume of the sample, in milliliters or cubic centimeters (mL or cm3).

TAKE 3 samples as a group, CALCULATE the average value as the test result.

10.1 Sample preparation

TAKE a certain amount of the catalyst, PLACE it in a vacuum oven at 80 °C to dry it for 12 hours, which is used as a sample to be tested.

The sample mass shall meet the requirements of 3 valid tests.

10.2 Test instrument equipment and materials

connecting the electronic load. Among them, the current meter adjustment precision is not less than 0.01 A; voltmeter range. >= 2V, adjustment time <= 100 ms. H2 mass flow controller (MFC). precision >= ± 1% FS; Air/O2 mass flow controller. precision >= ± 1% FS. Temperature control meter range. room temperature -200 °C, precision >= ± 1 °C. Pressure gauge. precision >= ± 1% FS.

Figure 2 -- Schematic diagram of proton exchange membrane fuel cell test platform

10.2.4 Test gas and water

10.2.4.1

H2. Compressed H2 with a purity>= 99.999%, after bubbling humidification, it is subject to pipeline thermal insulation and enter the test cell, the pipeline temperature is not lower than the humidification temperature.

10.2.4.2

O2. Compressed O2 with a purity >= 99.999%, after bubbling humidification, it is subject to pipeline thermal insulation and enter the test cell, the pipeline temperature is not lower than the humidification temperature.

10.2.4.3 Deionized water for humidification

Conductivity < 0.25 µS/cm.

10.2.5 Gas diffusion layer

The diffusion layer adopts the Sigracet GDL 30BC commercialized by SGL.

10.2.6 Proton conductor

The proton conductors uniformly use the Nafion solution of DE512 model, which is commercially available from DuPont.

10.3 Test procedure

10.3.1 Catalytic layer preparation by screen-printing

10.3.1.1

Based on the anode Pt loading 0.3 mg/cm2, the cathode Pt loading 0.5 mg/cm2, the Pt content in the catalyst, and screen-printing electrode area 50 cm2, CALCULATE the amount of catalyst which is used to prepare the catalyst layer, WEIGH it, accurate to 0.1 mg.

10.3.1.2

After sufficiently wetting the catalyst with a small amount of deionized water, ADD the lower alcohol (ethanol, isopropanol, ethylene glycol, etc.) as a dispersant in accordance with the ratio of W catalyst . W dispersant = 1.15.

DISPERSE the above mixture ultrasonically in an ultrasonic wave, while stirring it clockwise, to ensure that the liquid material is homogeneous along each direction, and free from lump, blocking, or particle.

10.3.1.3

Based on the ratio of the amount of carbon powder in the catalyst to the amount of Nafion at L carbon . L NetNafion = 1.0.8, ADD the 5% Nafion solution two requirements shall be met.

(1) CONTROL and RECORD the pressure at the cathode inlet, to ensure that water in the U-tube does not enter the cell.

(2) The detection gas pressure must be stable. Otherwise, the stable pressure difference cannot be read. It cannot be judged whether the pressure difference i... […]