Device and method for detecting catalyst loading capacity on membrane electrode
阅读说明：本技术 一种膜电极上催化剂载量的检测装置及方法 (Device and method for detecting catalyst loading capacity on membrane electrode ) 是由 刘建国 周扬 李佳 于 2020-12-01 设计创作，主要内容包括：本发明公开了一种膜电极上催化剂载量的检测装置及方法,装置包括电源、样品台以及固定在样品台上的膜电极,膜电极上设置有用于与电源连接的探头电源的正负极通过导线与探头连接；电源上并联有用于给膜电极施加电压的电压控制系统,电源与探头之间还串联有用于收集膜电极上施加电压后产生电流信号的电流收集系统。将待测膜电极置于样品台上,利用电压控制系统对膜电极施加电压,并通过电流收集系统得到该电压下通过膜电极的电流值,通过载量-电流标准曲线对催化层中催化剂含量进行定量。本发明不会对电极造成结构破坏,检测速度快,检测结果精确。(The invention discloses a device and a method for detecting the catalyst loading capacity on a membrane electrode, wherein the device comprises a power supply, a sample stage and a membrane electrode fixed on the sample stage, wherein the membrane electrode is provided with a positive electrode and a negative electrode of a probe power supply for connecting with the power supply, and the positive electrode and the negative electrode of the probe power supply are connected with a probe through leads; the power supply is connected in parallel with a voltage control system for applying voltage to the membrane electrode, and a current collecting system for collecting current signals generated after the voltage is applied to the membrane electrode is also connected in series between the power supply and the probe. And (3) placing the membrane electrode to be tested on a sample table, applying voltage to the membrane electrode by using a voltage control system, obtaining the current value passing through the membrane electrode under the voltage by using a current collection system, and quantifying the content of the catalyst in the catalyst layer by using a load-current standard curve. The invention can not cause structural damage to the electrode, has high detection speed and accurate detection result.)
1. The utility model provides a detection device of catalyst loading capacity on membrane electrode which characterized in that: the device comprises a power supply (1), a sample table (5) and a membrane electrode fixed on the sample table, wherein a probe (4) used for being connected with the power supply is arranged on the membrane electrode, and the positive electrode and the negative electrode of the power supply (1) are connected with the probe (4) through leads; the power supply (1) is connected in parallel with a voltage control system (2) for applying voltage to the membrane electrode, and a current collecting system (3) for collecting current signals generated after the voltage is applied to the membrane electrode is also connected in series between the power supply (1) and the probe (4).
2. The method for detecting the catalyst loading on the membrane electrode according to claim 1, comprising the steps of:
step one, preparing a loading capacity-current standard curve chart according to a CCM (continuous current reference) membrane with a known catalyst loading capacity;
placing the membrane electrode to be tested on a sample table, and applying voltage to the membrane electrode by using a voltage control system;
step three, the current collecting system detects the current value passing through the membrane electrode under the voltage according to the voltage applied in the step two;
and step four, converting the current value obtained in the step three into the loading capacity of the catalyst on the membrane electrode according to the loading capacity-current standard curve chart obtained in the step one, and obtaining the detection result of the loading capacity of the catalyst on the membrane electrode.
3. The method for detecting the catalyst loading on the membrane electrode according to claim 2, wherein in the first step, the specific preparation of the loading-current standard curve chart comprises the following steps:
the first step is as follows: applying a controllable voltage to the CCM membrane with known catalyst loading capacity, and measuring the current value passing through the CCM membrane under the voltage by a current collection system;
the second step is that: changing the catalyst loading capacity of the CCM, and repeating the operation of the first step to obtain the current values of the CCM with different loading capacities under the controllable voltage;
the third step: and according to the test result of the second step, carrying capacity-current standard curve graphs are obtained through linear fitting.
4. The method for detecting the amount of catalyst supported on a membrane electrode according to claim 3, wherein: and the voltage applied in the step two is consistent with the controllable voltage value applied when the loading capacity-current standard curve chart is prepared in the step one.
5. The method for detecting the amount of catalyst supported on a membrane electrode according to claim 3 or 4, wherein: the controllable voltage range is 0-30V.
6. The method for detecting the amount of catalyst supported on a membrane electrode according to claim 3, wherein: the catalyst loading range of the CCM membrane is 0.1-0.5 mg/cm2。
7. The method for detecting the amount of catalyst supported on a membrane electrode according to claim 6, wherein: the catalyst is a conductor which takes metal elements as active substances and comprises one or more than two of Pt/C, Pt-M/C, Pt black; wherein M is one or more of Co, Fe and Ni.
8. The method for detecting the amount of catalyst supported on a membrane electrode according to claim 2, wherein: the detection area of the film to be detected is 1-900 cm2。
Technical Field
The invention relates to a method for detecting the catalyst loading capacity, in particular to a device and a method for quantifying the catalyst loading capacity on a membrane electrode production line of a fuel cell.
Background
A fuel cell is an energy conversion device that oxidizes and reduces hydrogen and oxygen, respectively, through an electrochemical reaction process, releasing electrical energy, and producing water as a byproduct. The fuel cell mainly comprises a cathode and an anode and an electrolyte membrane, wherein the anode of the cell generates oxidation reaction; the cathode of the cell is subjected to a reduction reaction, and the cathode and the anode work together to enable the fuel cell to generate a complete electrochemical reaction. The internal structure of the fuel cell is formed by connecting dozens to hundreds of membrane electrodes and bipolar plates in series in sequence, wherein the membrane electrode is a core component of the fuel cell, is a place for electrochemical reaction in the cell and consists of an ion exchange membrane, a catalyst layer and a gas diffusion layer. The membrane electrode structure comprises a first generation gas diffusion electrode, a second generation CCM type electrode, a third generation thin layer ordered structure electrode and the like according to different preparation processes of the catalyst layer, and the second generation CCM type membrane electrode is still widely applied at present. With the rapid development of fuel cell technology, the preparation process of the membrane electrode is also developed from the small-scale monolithic preparation process in a laboratory to the continuous preparation process of a professional production line, and higher requirements are also provided for quality monitoring in the membrane electrode preparation process in order to ensure the consistency of the membrane electrode preparation in batches.
A traditional method for determining the catalyst loading capacity of a membrane electrode is mainly an off-line determination method, and a patent with the application number of 200610046299.X discloses a method for determining the platinum loading capacity of the membrane electrode of a proton exchange membrane fuel cell. The off-line testing method is suitable for determining the Pt loading of the membrane electrode prepared in a laboratory research stage, and when the membrane electrode is continuously produced, the off-line testing method not only destroys the continuity of a product, but also has no timeliness, and influences the efficiency of continuous production of the electrode. With the further development of detection technology, in recent years, X-ray fluorescence spectroscopy (XRF) technology has been applied to fuel cell membrane electrode assembly line quantification of catalyst loading. Because the platinum element is used as the core of the catalyst commonly used in the current fuel cell, the determination of the amount of the platinum element is mainly used as the standard during online detection. Usually, the catalyst is only present in the catalyst layer of the membrane electrode, and the method mainly aims at detecting the prepared catalyst layer. Specifically, an X-ray fluorescence spectrometer is introduced into a membrane electrode production line, a quantitative identification of platinum elements on a two-dimensional area is carried out by the spectrometer, the platinum elements in the prepared catalyst layer are quantified, and then the catalyst loading of the produced membrane electrode is determined. The XRF can also be used for nondestructive detection, but the operation speed of a membrane electrode production line is high, the XRF detection speed is low, and the detection result is easy to be inaccurate.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a device capable of measuring the catalyst content of a membrane electrode prepared on a membrane electrode production line on line; the second purpose of the invention is to provide a detection method of the device.
The technical scheme is as follows: the invention relates to a device for detecting the catalyst loading capacity on a membrane electrode, which comprises a power supply, a sample table and a membrane electrode fixed on the sample table, wherein the membrane electrode is provided with a probe used for being connected with the power supply, and the positive electrode and the negative electrode of the power supply are connected with the probe through leads; the power supply is connected in parallel with a voltage control system for applying voltage to the membrane electrode, and a current collecting system for collecting current signals generated after the voltage is applied to the membrane electrode is also connected in series between the power supply and the probe.
The invention also provides a detection method of the device for detecting the catalyst loading capacity on the membrane electrode, which comprises the following steps:
step one, preparing a loading capacity-current standard curve chart according to a CCM (continuous current reference) membrane with a known catalyst loading capacity;
placing the membrane electrode to be tested on a sample table, and applying voltage to the membrane electrode by using a voltage control system;
step three, the current collecting system detects the current value passing through the membrane electrode under the voltage according to the voltage applied in the step two;
and step four, converting the current value obtained in the step three into the loading capacity of the catalyst on the membrane electrode according to the loading capacity-current standard curve chart obtained in the step one, and obtaining the detection result of the loading capacity of the catalyst on the membrane electrode.
Further, the specific preparation of the standard curve graph of loading capacity-current comprises the following steps:
the first step is as follows: applying a controllable voltage to the CCM membrane with known catalyst loading capacity, and measuring the current value passing through the CCM membrane under the voltage by a current collection system;
the second step is that: changing the catalyst loading capacity of the CCM, and repeating the operation of the first step to obtain the current values of the CCM with different loading capacities under the controllable voltage;
the third step: and according to the test result of the second step, carrying capacity-current standard curve graphs are obtained through linear fitting.
Further, the voltage applied in step two is consistent with the controllable voltage value applied when the loading capacity-current standard curve chart is prepared in step one.
Furthermore, the controllable voltage range is 0-30V.
Further, the catalyst loading range of the CCM membrane is 0.1-0.5 mg/cm2。
Furthermore, the catalyst is a conductor which takes metal elements as active substances and comprises one or more than two of Pt/C, Pt-M/C, Pt black; wherein M is one or more of Co, Fe and Ni.
Further, the detection area of the film to be detected is 1-900 cm2。
The working principle is as follows: the invention utilizes the direct current excitation technology to carry out on-line quantification on the catalyst loading capacity of the electrode, the membrane electrode performance is mainly controlled by controlling the catalyst loading capacity in the membrane electrode production process, the thicknesses of catalyst layers with different catalyst loading capacities are different, and the corresponding resistances are also different. Because the catalysts commonly used in the current fuel cell are all conductors, the catalysts are only present in the catalyst layer of the membrane electrode, and the method mainly aims at detecting the prepared catalyst layer. And applying voltage to the membrane electrode to measure current, quantifying the content of the catalyst in the catalyst layer through a loading capacity-current standard curve, and entering the next step of the electrode reaching the detection index, or else, scrapping or reworking.
Has the advantages that: compared with the prior art, the invention has the following remarkable characteristics: 1. the invention provides a method for quantifying the catalyst content in a membrane electrode on line on a membrane electrode production line, which is characterized in that after the preparation step of a catalyst layer, a direct current excitation technology is introduced, and the catalyst content of the prepared catalyst layer is quantified on line, so that the catalyst content consistency of the prepared catalyst layer is ensured; 2. compared with an offline detection method, the method does not cause structural damage to the electrode, and the tested electrode can still be normally used; 3. compared with an XRF detection method, the method can rapidly quantify the content of the catalyst in the prepared catalyst layer, and has the advantages of high detection speed and accurate detection result.
Drawings
FIG. 1 is a schematic diagram of the structure of the apparatus of the present invention;
FIG. 2 is a standard load-current curve fitted for example 1;
FIG. 3 is a standard load-current curve fitted for example 2;
FIG. 4 is a standard load-current curve fitted for example 3;
FIG. 5 is a comparative error plot for examples 1-3;
FIG. 6 is a graph comparing the performance of the membrane electrode before and after application of a voltage according to the present invention.
Detailed Description
The invention is further illustrated by the following examples and figures.
Referring to fig. 1, the device for detecting the catalyst loading capacity on the membrane electrode comprises a power supply 1, a sample stage 5 and a membrane electrode fixed on the sample stage, wherein the membrane electrode is flatly placed on the sample stage 5, a probe 4 for connecting with the power supply is arranged on the membrane electrode, the power supply adopts a PS-305 model power supply, the positive electrode and the negative electrode of the power supply are respectively connected with the probe 4 through leads, a voltage control system 2 is connected in parallel on the power supply 1, specifically, a PS-305 model voltmeter (the measuring range is 0-30V) is adopted, a current collection system 3 is connected in series between the power supply 1 and the probe 4, specifically, a precision ammeter (the measuring range is 0-5A) is adopted, the voltage is applied to the membrane electrode during actual detection to measure the current, and the catalyst.
Example 1
Firstly, three CCM membranes with the area of 3cm multiplied by 7cm are selected for direct current excitation, wherein the catalyst carrying capacity of each CCM membrane is 0.1mg/cm2、0.2mg/cm2And 0.3mg/cm2. The CCM membrane was fixed by a jig so as not to be deformed, and a circuit diagram was connected as shown in FIG. 1, and a controllable voltage of 12V was applied to the CCM membrane. The current value at 12V was recorded from a precision ammeter and the data obtained are shown in table 1 below.
Table 1 load-current data summary table
Load capacity (mg/cm)2)
Current (mA)
0.1
6.35
0.2
9.6
0.3
16.8
The load and current were linearly fitted according to the data in table 1 to obtain the load-current standard curve of fig. 2, which is expressed as Y-54.30X, R20.99018; wherein X is the catalyst loading and Y represents the current.
Placing a membrane electrode to be tested on a sample table, wherein the catalyst on the membrane electrode to be tested is Pt/C, the detection area of the membrane to be tested is 3cm multiplied by 7cm, connecting a circuit diagram according to the graph 1 to carry out direct current excitation, applying voltage of 12V, repeating for 5 times to obtain 5 groups of current values of 10.64mA, 10.76mA, 10.85mA, 10.96mA and 11.08mA respectively, and obtaining corresponding 5 groups of loading amounts of 0.196mg/cm respectively on a loading amount-current standard curve of the graph 22，0.198mg/cm2，0.200mg/cm2，0.202mg/cm2，0.204mg/cm2(ii) a For the obtained five groupsThe loading amounts are summed and averaged to obtain a loading amount value, i.e., a measured loading amount value of 0.200mg/cm2。
Referring to the results shown in fig. 6, the membrane electrode performance did not change much before and after the voltage was applied. When no voltage is applied, the open-circuit voltage of the membrane electrode is 0.885V, and the maximum power density is 569.25mW/cm2After voltage application, the membrane electrode open-circuit voltage is 0.908V, and the maximum power density is 553.74mW/cm2. The open circuit voltage and the maximum power density of the device are not obviously changed, which shows that the method is a nondestructive test and does not cause damage on the performance of raw materials.
Example 2
Firstly, three CCM membranes with the area of 5cm multiplied by 8cm are selected for direct current excitation, wherein the catalyst carrying capacity of each CCM membrane is 0.1mg/cm2、0.2mg/cm2And 0.3mg/cm2. The CCM membrane was fixed by a jig so as not to be deformed, and a circuit diagram was connected as shown in FIG. 1, and a controllable voltage of 20V was applied to the CCM membrane. The current value at 20V was recorded from a precision ammeter, and the data obtained are shown in Table 2 below.
Table 2 load-current data summary table
Load capacity (mg/cm)2)
Current (mA)
0.1
11.18
0.2
17.58
0.3
29.43
The loading and current were linearly fitted according to the data in table 2 to obtain the loading-current standard curve of fig. 3, which is expressed as Y-96.14X, R20.99364; wherein X is the catalyst loading and Y represents the current.
Placing a membrane electrode to be tested on a sample table, connecting a circuit diagram according to the graph 1 to perform direct current excitation, applying a voltage of 20V, repeating the steps for 5 times to obtain 5 groups of current values of 35.62mA, 37.75mA, 38.47mA, 39.50mA and 40.48mA respectively, and obtaining corresponding 5 groups of load values of 0.371mg/cm on a load capacity-current standard curve of the graph 32，0.393mg/cm2，0.400mg/cm2，0.411mg/cm2，0.421mg/cm2(ii) a The obtained five groups of loading are summed and averaged, and the obtained loading value, namely the measured loading value is 0.399mg/cm2。
Example 3
Firstly, three CCM membranes with the area of 3cm multiplied by 7cm are selected for direct current excitation, wherein the catalyst carrying capacity of each CCM membrane is 0.1mg/cm2、0.2mg/cm2And 0.4mg/cm2. The CCM membrane was fixed by a jig so as not to be deformed, and a circuit diagram was connected as shown in FIG. 1, and a controllable voltage of 8V was applied to the CCM membrane. The current value at this 8V voltage was recorded from a precision ammeter and the data obtained are shown in table 3 below.
Table 3 load-current data summary table
Load capacity (mg/cm)2)
Current (mA)
0.1
3.93
0.2
5.88
0.4
13.72
The load and current were linearly fitted according to the data in table 1 to obtain the load-current standard curve of fig. 4, where Y is 34.29X, R20.9869; wherein X is the catalyst loading and Y represents the current.
Placing a membrane electrode to be tested on a sample table, wherein the catalyst on the membrane electrode to be tested is Pt/C, the detection area of the membrane to be tested is 3cm multiplied by 7cm, connecting a circuit diagram according to the graph 1 to carry out direct current excitation, applying the voltage of 8V, repeating the steps for 5 times to obtain 5 groups of current values of 10.29mA, 10.36mA, 10.36mA, 10.53mA and 10.60mA respectively, and obtaining corresponding 5 groups of loading amounts of 0.300mg/cm respectively on a loading amount-current standard curve of the graph 42，0.302mg/cm2，0.302mg/cm2，0.307mg/cm2，0.309mg/cm2(ii) a The obtained five groups of loading capacity are summed and averaged, and the obtained loading capacity value, namely the measured loading capacity value is 0.304mg/cm2。
Example 4
Referring to FIG. 5, as can be seen from the comparison of the measured loading values with the actual loading values of examples 1-3, example 1 measured the platinum loading of the catalyst to be 0.203mg/cm by the ICP method2And 0.200mg/cm as measured by a DC excitation method2The error is 0.003mg/cm2. Similarly, example 2 has an error of 0.003mg/cm2Example 3 error 0.002mg/cm2Specific numerical values are summarized in the following table, and in general, the method has high precision and the error is not more than 0.005mg/cm2And the method has higher feasibility in the actual production process.
ICP method
Direct current excitation method
Error of the measurement
0.203mg/cm2
0.200mg/cm2
0.003mg/cm2
0.402mg/cm2
0.399mg/cm2
0.003mg/cm2
0.302mg/cm2
0.304mg/cm2
0.002mg/cm2
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