Method for determining the platinum content in an automotive stack

Abstract

The application discloses a kind of determination methods of the platinum content in automobile electric pile, the method is dissolved in aqua regia medium to automobile electric pile using microwave digestion instrument, ensure that the platinum in electric pile can be completely dissolved, after dissolving the sample to be measured is transferred into 100mL volumetric flask, with water constant volume, on inductively coupled plasma emission spectrometer to determine the platinum content, obtain the test result.Compared with the original ashing decomposition activated carbon sample pretreatment process, the application has sample complete dissolution, simple analysis process.Compared with the determination of platinum content by spectrophotometry, the application has high determination sensitivity, fast determination speed, small interference, wide linear range, and can realize multi-element joint measurement and other characteristics.The application can extend the determination of platinum content in carbon material.

Description

Technical Field

[0001] This invention belongs to the field of chemical analysis, specifically relating to a method for determining the platinum content in automotive fuel cell stacks. Background Technology

[0002] The fuel cell stack is the most critical component of a fuel cell and the core of its power system. During operation, hydrogen and oxygen are introduced through inlets and distributed to the bipolar plates of each cell via the main gas channel. From there, they are evenly distributed to the electrodes via the bipolar plates and then contact the catalyst through the electrode support for electrochemical reactions. Currently, activated carbon-supported catalysts are commonly used, including supported heterogeneous catalysts with platinum group metals (Pt, Pd, Rh, Ru) as the catalytic active components. The content and distribution of the active components in the catalyst directly affect its activity, selectivity, and lifetime. Current methods for determining platinum content include the ammonium chloroplatinate gravimetric method and galvanostatic titration, primarily used for high platinum content. Low platinum content is mainly detected using atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry (ICP-AES), and X-ray fluorescence spectrometry. By reviewing published papers and other relevant materials, previous researchers have used chemical methods to convert platinum into more stable platinum (+Ⅳ). They utilized the reaction of stannous chloride with platinum (+Ⅳ) in dilute hydrochloric acid solution to produce a yellow-orange complex, and then measured the wavelength at the maximum absorption peak using a UV-Vis spectrophotometer to calculate the platinum content. Alternatively, they used a step-heating method to ashing and decomposing activated carbon in the automotive fuel cell stack, then dissolved the platinum in aqua regia after reducing the residue, and added yttrium internal standard to control instrument drift to determine the platinum content. Another method involved using high-purity platinum as a standard, creating a standard curve, and verifying it with analytical grade chloroplatinic acid. The platinum content in the automotive fuel cell stack was calculated based on the difference between the analytical results and the given values. However, these methods are complex, and the colorimetric and extraction organic reagents used in spectrophotometry are prone to environmental pollution. Furthermore, the electrodes contain 1-5% fluorinated resins, which are flammable, and the ashing and decomposing of activated carbon poses a fire risk. Summary of the Invention

[0003] The purpose of this invention is to solve the technical problems existing in the prior art and provide a method for determining the platinum content in automotive fuel cell stacks that has a short sample pretreatment process, thorough sample dissolution, and rapid and accurate measurement results.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for determining the platinum content in an automotive fuel cell stack includes the following steps:

[0006] (1) Weigh 0.1~1.0g of the fuel cell sample that has been dried to constant weight in an oven at 100±5℃ into a digestion tube, add 10~100mL of aqua regia, cover the tube, place it in the reaction chamber of a microwave digester, and digest it according to the following process conditions:

[0007] First segment, temperature: 0~50℃, time: 5min;

[0008] Second stage, temperature: 50~110℃, time: 5min;

[0009] Third segment, temperature: 110℃, time: 10min;

[0010] Fourth stage, temperature: 110~150℃, time: 5min;

[0011] Fifth segment, temperature: 150℃, time: 5min;

[0012] Section 6, Temperature: 150~180℃, Time: 5min;

[0013] Section 7, Temperature: 180℃, Time: 15min;

[0014] (2) After the microwave digestion apparatus has finished reacting and the pressure has been safely released, transfer the solution in the digestion tube into a 100-500 mL volumetric flask, cool it, dilute it to the mark with water, and shake well.

[0015] (3) Plotting the working curve: Transfer 0.00 mL, 0.50 mL, 2.50 mL, 5.00 mL, 15.00 mL, and 25.00 mL of 20 mg / L platinum standard solution into corresponding 100 mL volumetric flasks, and dilute to volume with 10% aqua regia to obtain working curve standard solutions with concentrations of 0 mg / L, 0.1 mg / L, 0.5 mg / L, 1 mg / L, 3 mg / L, and 5 mg / L, respectively; and measure the standard solutions with inductively coupled plasma atomic emission spectrometry (ICP-AES), and the instrument automatically plots the working curve;

[0016] (4) Sample determination: Dilute the solution prepared in (2) by 10 times and measure it at the Pt:265.945nm spectral line on an inductively coupled plasma spectrometer. Then, the test result of platinum in the stack can be calculated according to the working curve drawn in (3).

[0017] In step 4) above, the mass fraction of platinum is calculated using the following formula:

[0018]

[0019] In the formula:

[0020] The mass fraction of ω(β)-platinum, expressed in %

[0021] c - Platinum concentration obtained from the working curve, in mg / L;

[0022] V - constant volume, in milliliters (L);

[0023] m - The mass of the sample required to prepare the determination solution, in mg;

[0024] The analysis results are expressed to two decimal places.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] This invention employs a microwave digester to dissolve automotive fuel cell stacks in aqua regia, ensuring complete dissolution of platinum. The dissolved sample is then placed in a 100mL volumetric flask, diluted to volume, and shaken thoroughly before being analyzed using an inductively coupled plasma atomic emission spectrometer (ICP-AES) to determine the platinum content. Compared to the traditional activated carbon ashing pretreatment process, this invention offers advantages such as thorough sample dissolution and elimination of fire hazards during operation. Compared to spectrophotometric determination of platinum content, this invention features high sensitivity, fast measurement speed, minimal interference, wide linear range, no environmental pollution, and the ability to perform multi-element simultaneous analysis. This invention can also be extended to determine the content of other precious metals in automotive fuel cell stacks. Attached Figure Description

[0027] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0028] See Figure 1 The present invention provides a method for determining the platinum content in an automotive fuel cell stack, comprising the following steps: (1) Weigh 0.1000g of a sample that has been dried to constant weight in an oven at 100℃±5℃ into a microwave digestion tube, add 10mL of freshly prepared aqua regia, tighten the cap appropriately, place the digestion tube in the reaction chamber of the microwave digestion instrument, and operate according to the conditions listed in Table 1.

[0029] Table 1 Experimental conditions for microwave digestion apparatus

[0030]

[0031] (2) After the microwave digestion instrument has finished reacting and the pressure has been safely released, transfer the solution in the digestion tube into a 100mL volumetric flask, cool it, dilute it to the mark with water, and shake it well; (3) Under the experimental conditions of inductively coupled plasma atomic emission spectrometer, determine the emission intensity values ​​of Pt element in the standard grade solution and the sample solution in sequence, plot the working curve by computer and automatically print out the measurement results.

[0032] Example 1

[0033] For Toyota fuel cell stack No. 1, the sample was dried to constant weight in an oven at 100℃±5℃. 0.1000g of the sample was weighed into a microwave digestion tube, and 10mL of freshly prepared aqua regia was added. The cap was tightened appropriately, and the digestion tube was placed in the reaction chamber of the microwave digester. The sample dissolution was started according to the set program. After the microwave digestion reaction was completed and the pressure was safely released, the solution in the digestion tube was transferred to a 100mL volumetric flask, cooled, and diluted to the mark with water. The solution was then shaken well. The test sample and standard sample were analyzed together using an inductively coupled plasma atomic emission spectrometer (ICP-AES). The platinum content analysis results are shown in Table 2 below.

[0034] Table 2 Analytical results of sample 1

[0035]

[0036] Example 2

[0037] For Toyota fuel cell stack No. 2, the sample was dried to constant weight in an oven at 100℃±5℃. 0.1000g of the sample was weighed into a microwave digestion tube, and 10mL of freshly prepared aqua regia was added. The cap was tightened appropriately, and the digestion tube was placed in the reaction chamber of the microwave digester. The sample dissolution was started according to the set program. After the microwave digestion reaction was completed and the pressure was safely released, the solution in the digestion tube was transferred to a 100mL volumetric flask, cooled, and diluted to the mark with water. The solution was then shaken well. The test sample and standard sample were analyzed together using an inductively coupled plasma atomic emission spectrometer (ICP-AES). The platinum content analysis results are shown in Table 3 below.

[0038] Table 3 Analytical results of sample No. 2

[0039]

[0040] Example 3

[0041] For Toyota fuel cell stack No. 3, the sample was dried to constant weight in an oven at 100℃±5℃. 0.1000g of the sample was weighed into a microwave digestion tube, and 10mL of freshly prepared aqua regia was added. The cap was tightened appropriately, and the digestion tube was placed in the reaction chamber of the microwave digester. The sample dissolution was started according to the set program. After the microwave digestion reaction was completed and the pressure was safely released, the solution in the digestion tube was transferred to a 100mL volumetric flask, cooled, and diluted to the mark with water. The solution was then shaken well. The test sample and standard sample were analyzed together using an inductively coupled plasma atomic emission spectrometer (ICP-AES). The platinum content analysis results are shown in Table 4 below.

[0042] Table 4 Analytical results of sample No. 2

[0043]

Claims

1. A method for determining the platinum content in an automotive fuel cell stack, characterized in that, Includes the following steps: (1) Weigh 0.1~1.0g of the fuel cell stack sample that has been dried to constant weight in an oven at 100±5℃ into a digestion tube, add 10~100mL of aqua regia, cover the tube, place it in the reaction chamber of a microwave digester, and digest it according to the following process conditions: First segment, temperature: 0~50℃, time: 5min; Second stage, temperature: 50~110℃, time: 5min; Third segment, temperature: 110℃, time: 10min; Fourth stage, temperature: 110~150℃, time: 5min; Fifth segment, temperature: 150℃, time: 5min; Section 6, Temperature: 150~180℃, Time: 5min; Section 7, Temperature: 180℃, Time: 15min; (2) After the microwave digestion apparatus has finished reacting and the pressure has been safely released, transfer the solution in the digestion tube into a 100-500 mL volumetric flask, cool it, dilute it to the mark with water, and shake well. (3) Construction of working curves: Transfer 0.00 mL, 0.50 mL, 2.50 mL, 5.00 mL, 15.00 mL and 25.00 mL of 20 mg / L platinum standard solution into the corresponding 100 mL volumetric flasks, and dilute to volume with 10% aqua regia to obtain working curve standard solutions with concentrations of 0 mg / L, 0.1 mg / L, 0.5 mg / L, 1 mg / L, 3 mg / L and 5 mg / L, respectively. The standard solution was measured using an inductively coupled plasma atomic emission spectrometer, and the instrument automatically plotted the working curve. (4) Sample determination: Dilute the solution prepared in (2) by 10 times and measure it at the Pt:265.945nm spectral line on an inductively coupled plasma spectrometer. Then, the concentration of platinum in the stack can be obtained according to the working curve drawn in step (3).

2. The method for determining the platinum content in an automotive fuel cell stack according to claim 1, characterized in that: In step 4), the mass fraction of platinum is calculated using the following formula: In the formula: The mass fraction of ω(β)-platinum, expressed in % c - Platinum concentration obtained from the working curve, in mg / L; V - constant volume, in milliliters (L); m - The mass of the sample required to prepare the determination solution, in mg; The analysis results are expressed to two decimal places.

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