A method for testing the utilization rate of the anode catalyst in a PEM electrolyzer

Abstract

The present application relates to a method for testing the utilization rate of an anode catalyst in a PEM electrolyzer. The method includes: performing a rotating disk electrode test to obtain the specific double-layer capacitance C of an ideal model system with a catalyst utilization rate of 100% dl,RDE max ; performing a PEM electrolyzer test to obtain the specific double-layer capacitance C of the anode catalyst layer dl,MEA ; calculating the anode catalyst utilization rate U. The method of the present application can test the actual utilization rate of the anode metal oxide catalyst in the PEM electrolyzer, so as to guide the optimization of the anode catalyst layer through the catalyst utilization rate of the anode catalyst layer, and provide a guiding basis for the optimization of the PEM electrolyzer in aspects such as reducing the loading of the anode catalyst layer.

Description

Technical Field

[0001] The present application relates to a method for testing the utilization rate of an anode catalyst in a PEM electrolyzer. Background Art

[0002] PEM (Proton Exchange Membrane) electrolysis of water has the advantages of being structurally compact, having a clean working environment, and a fast response speed, and has become one of the key technical options for renewable energy conversion and storage. However, PEM electrolysis of water relies on expensive noble metal materials, especially the metal iridium (Ir) on which the anode catalyst depends. The annual output is only about 7 tons, which is about 1 / 30 of the Pt output. The key challenge in the research and development of PEM electrolysis of water is to continuously reduce the amount of Ir used in the anode. Currently, there are mainly two ways: one is to improve the catalyst activity, and the other way is to improve the utilization rate of Ir. As the core component of PEM electrolysis of water, the membrane electrode is the place where the electrochemical reaction occurs, and its microstructure directly determines the efficiency and cost of the electrolyzer. The anodic oxygen evolution reaction in the PEM electrolysis of water is an electrode process with very slow kinetics. Therefore, the anode catalyst layer of the membrane electrode requires a high catalyst loading. A high-loading membrane electrode often leads to the stacking of catalysts inside the catalytic layer. Perfluorosulfonic acid resin (such as Nafion) needs to be added as a catalyst binder in the anode catalyst layer. Due to the uneven distribution of perfluorosulfonic acid resin in the catalytic layer, some catalysts will be wrapped, resulting in the fact that this part of the catalyst does not form a good interface with the electrolyte, leading to a low specific loading of the actually participating catalysts and resulting in the waste of Ir. Therefore, at the levels of the membrane electrode and the electrolyzer, the key thing to optimize is the catalyst utilization rate. However, different catalysts have different chemical properties, and many stable IrO2 do not have the characteristic peaks like those of platinum (Pt) metal. Therefore, it is very difficult to test the actual utilization rate of IrO2 by referring to the method for calculating the Pt utilization rate in the fuel cell field (Kazuma Shinozaki (2011) Journal of The Electrochemical Society, 158(5) B467 - B475.).

[0003] The literature (Journal of The Electrochemical Society, 162(12) F1292 - F1298(2015)) proposes a method for testing the utilization rate of IrO2 in PEM electrolysis of water. The membrane electrode is immersed in a solution containing zinc ions, so that the zinc ions are adsorbed on the surface of IrO2, and the pseudocapacitance generated by the adsorbed zinc ions is calculated by cyclic voltammetry to calculate the utilization rate of Ir. This method is not applicable to specific working conditions, and other substances such as Zn 2+ are adsorbed in the membrane electrode, and after the adsorption of Zn 2+ and after the adsorption of Zn 2+It is difficult to remove from the membrane, and the membrane electrode cannot be tested repeatedly.

[0004] Currently, the optimization of many membrane electrodes and electrolytic cells is basically based on the differences in macroscopic performance, which cannot directly reflect the specific conditions of the anode catalyst layer, resulting in a small performance optimization space, a lack of theoretical guidance, and it is difficult to commercialize electrolytic cells with ultra-low Ir loading. The development of low-Ir loading electrolytic cells urgently requires a non-destructive test method for catalyst utilization under operating conditions, using the actual catalyst utilization as the basis for optimizing the membrane electrode preparation process. Summary of the Invention

[0005] This application provides a method for testing the utilization rate of the anode catalyst in a PEM electrolytic cell, including:

[0006] S1 Conduct a rotating disk electrode test, including:

[0007] S11 Form a catalyst layer in the central area of the rotating disk electrode with the anode catalyst to be tested to obtain a rotating disk electrode with a catalyst layer;

[0008] S12 Use the rotating disk electrode with the catalyst layer as the working electrode to determine the specific double-layer capacitance C dl,RDE ;

[0009] S13 By reducing the catalyst loading per unit area on the rotating disk electrode, repeat the above S11 and S12 to obtain the specific double-layer capacitance C of the 100% ideal model system of catalyst utilization dl,RDE max ;

[0010] S2 Conduct a PEM electrolytic cell test, including:

[0011] S21 Construct a PEM electrolytic cell, where the anode catalyst to be tested forms the anode catalyst layer of the PEM electrolytic cell;

[0012] S22 Conduct a cyclic voltammetry test on the PEM electrolytic cell at a voltage sweep rate v1 to measure the double-layer capacitance current density I c1 of the anode catalyst layer, and calculate the specific double-layer capacitance C dl,MEA of the anode catalyst layer according to the following formula (1):

[0013] C dl,MEA = I c1 / v1 m1 catalyst (1)

[0014] Among them, the double-layer capacitance current density I c1 of the anode catalyst layer is in mA / cm 2 count,

[0015] The catalyst loading per unit area in the anode catalyst layer, m1 catalyst is in mg / cm 2 .

[0016] The voltage scan rate v1 is in V / s,

[0017] The specific double-layer capacitance C of the anode catalyst layer dl,MEA is in F / g;

[0018] S3 calculates the anode catalyst utilization U according to Equation (2),

[0019] U = C dl,MEA / C dl,RDE max (2).

[0020] In one embodiment, in the rotating disk electrode test, cyclic voltammetry tests are performed at different voltage scan rates v to obtain different voltammetric cyclic curves under the same liquid electrolyte system conditions, and the specific double-layer capacitance C is calculated by formula (3) dl,RDE :

[0021] C dl,RDE = I c / v m catalyst (3)

[0022] wherein, the double-layer capacitance current density I of the working electrode c is in mA / cm 2 .

[0023] The catalyst loading per unit area on the rotating disk electrode, m catalyst is in mg / cm 2 .

[0024] The voltage scan rate v is in V / s,

[0025] The specific double-layer capacitance C dl,RDE is in F / g.

[0026] In one embodiment, the voltage range for the rotating disk electrode test is 0.1 - 0.6 V.

[0027] In one embodiment, in the rotating disk electrode test, the specific double-layer capacitance C is determined according to the electrochemical impedance spectroscopy (EIS) dl,RDE .

[0028] In one embodiment, in the rotating disk electrode test, the liquid electrolyte system is selected from sulfuric acid solution, perchloric acid solution, sodium hydroxide solution, and potassium hydroxide solution.

[0029] In one embodiment, the PEM electrolyzer comprises a cathode plate, a cathode porous transport layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, an anode porous transport layer, and an anode plate that are in contact in sequence, wherein the cathode porous transport layer is selected from carbon paper, the cathode catalyst layer contains Pt / C, and the anode porous transport layer is selected from titanium-based porous materials.

[0030] In one embodiment, hydrogen is introduced into the cathode region of the PEM electrolyzer, and the cathode catalyst layer is used as a reference electrode.

[0031] In one embodiment, the voltage of the anode of the PEM electrolyzer relative to the cathode ranges from 0.1 V to 0.6 V.

[0032] The method of the present application does not require the use of additional substances for characterizing and calculating the catalyst utilization rate. Instead, it can perform non-destructive testing under operating conditions without introducing external impurities. The method of the present application can test the actual utilization rate of the catalyst of the anode metal oxide in the PEM electrolyzer, so as to guide the optimization of the anode catalyst layer through the catalyst utilization rate of the anode catalyst layer, and provide a guiding basis for the optimization of the PEM electrolyzer in aspects such as reducing the loading of the anode catalyst layer. Description of the Drawings

[0033] Figure 1 Shows a schematic structural diagram of an electrolytic cell;

[0034] Figure 2 Shows a simplified equivalent RC circuit diagram;

[0035] Figure 3 Shows the Nyquist diagram obtained by EIS testing;

[0036] Figure 4 Shows the curve of the real part of the impedance and the double-layer capacitance in EIS testing;

[0037] Figure 5 Shows the structure of the PEM electrolyzer;

[0038] Figure 6 Shows the specific double-layer capacitance C obtained by rotating disk electrode testing with different catalyst loadings dl,RDE ;

[0039] Figure 7Show the test results of the anode catalyst layers with different Nafion contents in Examples 1-4 under PEM electrolyzed water conditions. Among them, a1 and a2 are the voltage-current density curves and voltage-double layer current density curves at different voltage scanning rates when testing with a catalyst layer containing 5% Nafion; b1 and b2 are the voltage-current density curves and voltage-double layer current density curves at different voltage scanning rates when testing with a catalyst layer containing 10% Nafion; c1 and c2 are the voltage-current density curves and voltage-double layer current density curves at different voltage scanning rates when testing with a catalyst layer containing 30% Nafion; d1 and d2 are the voltage-current density curves and voltage-double layer current density curves at different voltage scanning rates when testing with a catalyst layer containing 50% Nafion.

[0040] Figure 8 Show that under 80 °C, PEM electrolyzed water tests are carried out by changing the Nafion content in the anode catalyst layer, and the specific double layer capacitance with different Nafion contents and the catalyst utilization rate with different Nafion contents are obtained.

[0041] Figure 9 Show the polarization curves of the anode catalyst layers with different Nafion contents obtained in Examples 1-4;

[0042] Figure 10 Show the cyclic voltammetry test diagrams of the anode catalyst layers with different Nafion contents obtained in Examples 1-4. Detailed implementation mode

[0043] The present application will be further described in detail below with reference to the accompanying drawings and examples. Through these descriptions, the features and advantages of the present application will become clearer and more definite.

[0044] The special term "exemplary" here means "serving as an example, embodiment or illustrative". Any embodiment described as "exemplary" here does not have to be construed as superior to or better than other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings do not have to be drawn to scale unless otherwise specified.

[0045] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0046] The present application provides a method for testing the anode catalyst utilization rate in a PEM electrolyzer, including:

[0047] S1 Conduct a rotating disk electrode test, including:

[0048] S11 Form a catalyst layer in the central region of the rotating disk electrode with the anode catalyst to be tested, obtaining a rotating disk electrode with a catalyst layer;

[0049] S12 Use the rotating disk electrode with the catalyst layer as the working electrode to determine the specific double-layer capacitance C dl,RDE ;

[0050] S13 By reducing the loading of the catalyst per unit area on the rotating disk electrode, repeat the above S11 and S12 to obtain the specific double-layer capacitance C of the ideal model system with a catalyst utilization rate of 100% dl,RDE max ;

[0051] S2 Conduct a PEM electrolyzer test, including:

[0052] S21 Construct a PEM electrolyzer, wherein the anode catalyst to be tested forms the anode catalyst layer of the PEM electrolyzer;

[0053] S22 Conduct a cyclic voltammetry test on the PEM electrolyzer at a voltage scan rate v1 to measure the double-layer capacitance current density I c1 of the anode catalyst layer, and calculate the specific double-layer capacitance C of the anode catalyst layer according to the following formula (1) dl,MEA :

[0054] C dl,MEA = I c1 / v1 m1 catalyst (1)

[0055] Wherein, the double-layer capacitance current density I c1 of the anode catalyst layer is in mA / cm 2 ;

[0056] The loading m1 of the catalyst per unit area in the anode catalyst layer catalyst is in mg / cm 2 ;

[0057] The voltage scan rate v1 is in V / s,

[0058] The specific double-layer capacitance C dl,MEA of the anode catalyst layer is in F / g;

[0059] S3 Calculate the anode catalyst utilization rate U according to formula (2),

[0060] U = C dl,MEA / C dl,RDE max (2).

[0061] In one embodiment, forming the catalyst layer in the central region of the rotating disk electrode includes:

[0062] Disperse the catalyst powder into a mixed system of water / isopropanol, use Nafion as a binder, disperse it into a uniform slurry, drop it onto the central area of the rotating disk electrode, and form a uniform catalyst layer after drying.

[0063] During the test, the loading of the catalyst powder is 0.005 - 0.2 mg / cm 2 , based on the total area of the active region of the working electrode. Generally speaking, the thickness of the catalyst layer can be 0.05 - 0.5 μm. When comparing the activities of different catalysts, in order to reflect the consistency of the data, usually the loadings of different catalysts and the thickness of the catalyst layer are kept the same. Or, normalization is carried out according to the loading and thickness.

[0064] In one embodiment, using the rotating disk electrode with the catalyst layer as the working electrode, the specific double - layer capacitance C can be determined by cyclic voltammetry tests. dl,RDE During the cyclic voltammetry test in the rotating disk electrode test, it can be carried out in the electrolytic cell shown in Figure 1 .

[0065] As Figure 1 shown, this electrolytic cell includes:

[0066] An electrolytic cell cavity 1, in which a rotating disk electrode 11 is arranged;

[0067] A counter - electrode cavity 2, in which a counter - electrode 21 is arranged; and

[0068] A reference - electrode cavity 3;

[0069] Wherein, the counter - electrode cavity 2 and the reference - electrode cavity 3 are respectively located on both sides of the electrolytic cell cavity 1, and are both in fluid communication with the electrolytic cell cavity 1;

[0070] Wherein, the reference - electrode cavity 3 includes:

[0071] An air inlet pipe 32 communicating with the reference - electrode cavity 3, used to introduce gas into the reference - electrode cavity 3;

[0072] A reference electrode 31, the end of the reference electrode 31 is adjacent to the interface 33 between the air inlet pipe 32 and the side wall of the reference - electrode cavity 3.

[0073] As Figure 1As shown in the figure, the electrolytic cell cavity 1 can adopt a spherical electrolytic cell. The counter electrode cavity 2 is connected to the bottom of the spherical electrolytic cell cavity 1 through a U-shaped tube 22. The bottom end of the reference electrode cavity 3 is also connected to the bottom of the spherical electrolytic cell cavity 1. Due to the principle of the U-shaped tube, the electrolyte will fill the counter electrode cavity 2 and the reference electrode cavity 3, which can reduce the amount of electrolyte used. The reference electrode cavity 3 also has feet 36 for supporting the reference electrode cavity 3.

[0074] When used in this application, the gas introduced is hydrogen, and the rotating disk electrode 11 can be immersed in the electrolyte. In order to disperse the introduced gas, especially hydrogen, into uniform and dense small bubbles, a gas distributor 34 is also provided at a position in the inlet pipe 32 near the interface 33. Preferably, the gas distributor 34 is a sintered glass filter.

[0075] In one embodiment, a sealing member 35 is further provided at the top of the reference electrode cavity 3.

[0076] When used in this application, the reference electrode 31 is a platinum electrode. In this application, the platinum electrode can include conductive materials with metallic platinum such as platinum sheets, platinum wires, platinum meshes, platinum-coated titanium felts, and platinum-coated carbon papers. Since hydrogen can be introduced through the inlet pipe 32 and combined with this platinum electrode, a reversible hydrogen electrode can be constructed in the reference electrode cavity 3.

[0077] When used in this application, the counter electrode 21 can be a series of common counter electrodes such as carbon paper, carbon rod, platinum wire, and platinum sheet.

[0078] As described above, in the rotating disk electrode test, the reference electrode 31 is a platinum electrode, and hydrogen can be introduced through the inlet pipe 32, so that a reversible hydrogen electrode can be constructed in the reference electrode cavity 3. During the test, using the reversible hydrogen electrode as the reference electrode for the electrochemical process has good stability and reproducibility, and at the same time avoids the system contamination problems that other reference electrodes may bring (such as: saturated calomel electrode and silver / silver chloride electrode will introduce Cl - ion contamination to the system), and also avoids the calibration and instability problems of other reference electrodes at different temperatures. In this application, the platinum electrode can include conductive materials with metallic platinum such as platinum sheets, platinum wires, platinum meshes, platinum-coated titanium felts, and platinum-coated carbon papers.

[0079] As described above, in order to disperse the introduced gas, especially hydrogen, into uniform and dense small bubbles, a gas distributor 34 is also provided at a position in the inlet pipe 32 near the interface 33. Preferably, the gas distributor 34 is a sintered glass filter. The hydrogen gas flow can form mist-like bubbles after passing through the sintered glass filter, reducing the disturbance. The hydrogen in the reference electrode cavity is quickly saturated, thus forming a stable reversible hydrogen electrode with the platinum electrode. The hydrogen gas introduction flow rate can be 20 mL / min, and after introducing for 5 - 10 minutes, it can reach saturation.

[0080] After that, a cyclic voltammetry test can be carried out. During the measurement, a certain amount of hydrogen is introduced, for example, the hydrogen flow rate can be 5 mL / min. During the test, an electrolyte is injected into the electrolytic cell, and the electrolyte can be sulfuric acid solution, perchloric acid solution, sodium hydroxide solution, potassium hydroxide solution, etc.

[0081] In the rotating disk electrode test, during the cyclic voltammetry test, cyclic voltammetry tests are carried out at different voltage sweep rates v to obtain different cyclic voltammograms under the condition of the same liquid electrolyte system, and the specific double-layer capacitance C is calculated by formula (3). dl,RDE :

[0082] C dl,RDE = I c / v m catalyst (3)

[0083] Among them, the double-layer capacitance current density I of the working electrode c is in mA / cm 2 counting,

[0084] the loading m of the catalyst per unit area on the rotating disk electrode catalyst is in mg / cm 2 counting,

[0085] the voltage sweep rate v is in V / s,

[0086] the specific double-layer capacitance C dl,RDE is in F / g.

[0087] In the above process, the double-layer capacitance current density I of the working electrode at different voltage sweep rates v can be obtained according to the cyclic voltammogram c (in mA / cm 2 counting), and then the specific double-layer capacitance C is calculated according to formula (3). dl,RDE .

[0088] Reduce the catalyst loading and repeat the above test process. When the measured value of the specific double-layer capacitance C dl,RDE changes little with the decrease of the catalyst loading (the change value is less than or equal to 10%), it can be considered that the measured value of the specific double-layer capacitance C dl,RDE reaches a constant, and the catalyst utilization rate in the ultra-low loading catalytic layer (0.1 μm) in the ideal liquid phase model is 100%, and the specific double-layer capacitance C of the ideal model system is obtained. dl,RDEmax .

[0089] In one embodiment, the voltage range of the cyclic voltammetry test for the rotating disk electrode test is the non-Faraday region of the metal oxide, which can be 0.2 - 0.6 V, including but not limited to this.

[0090] In one embodiment, in the rotating disk electrode test, the specific double-layer capacitance C can be determined according to the electrochemical impedance spectroscopy (EIS). dl,RDE The following describes the method for measuring the specific double-layer capacitance according to EIS.

[0091] Since the electrochemical impedance is a vector, it is often written in complex form, which consists of a real part and an imaginary part. The electrochemical impedance written in complex form is

[0092] Z = Z′ + jZ″

[0093] where Z is the electrochemical impedance, Z′ (Ω / cm 2 ) is its real part, Z″ (Ω / cm 2 ) is its imaginary part, and j is the imaginary unit

[0094] Based on the simplified equivalent RC circuit diagram (as shown in Figure 2 ):

[0095] R Ω (Ω / cm 2 ) is the resistance in the system, R ct (Ω / cm 2 ) is the charge transfer resistance, and C dl (F / cm 2 ) is the double-layer capacitance in the system. The double-layer capacitance is calculated by the following formula:

[0096]

[0097] Through the Nyquist diagram obtained by EIS test (as shown in Figure 3 ), the data of the real part Z′ and the imaginary part Z″ are obtained. Plotting the above data, with the vertical axis being C dl , and the horizontal axis being Z′, as the frequency decreases, when C dl approaches the maximum value, this value is the specific double-layer capacitance C dl,RDE of the catalytic layer, as shown in Figure 4 . Then, reduce the loading of the catalyst per unit area on the rotating disk electrode, repeat the above process, and obtain the specific double-layer capacitance C dl,RDE max of the ideal model system with 100% catalyst utilization.

[0098] The method of the present application further includes performing PEM electrolyzer tests. To perform PEM electrolyzer device tests, it is first necessary to construct a PEM electrolyzer device.

[0099] First step: Prepare a qualified proton exchange membrane PEM loaded with a catalyst. The catalyst can be made into a uniformly dispersed slurry by ball milling and then scrape-coated onto a PTFE substrate. Then, the catalyst layer can be transferred to the proton exchange membrane by hot pressing and transfer printing.

[0100] The catalyst can be dispersed in the slurry for preparing a membrane electrode assembly (MEA) to prepare catalyst layers with different Nafion contents. For example, the Nafion content can be 5%-50%. The content of Nafion is based on the total weight of the catalyst layer. In one embodiment, the proton exchange membrane can use a Nafion membrane.

[0101] Second step: Assemble the prepared membrane electrode assembly (MEA) into a PEM electrolyzer. The structure of the PEM electrolyzer is as Figure 5 shown, including a cathode bipolar plate CBP, a cathode porous transport layer CPTL, a cathode catalyst layer CCL, a proton exchange membrane PEM (membrane electrode assembly MEA), an anode catalyst layer ACL, an anode porous transport layer APTL, and an anode bipolar plate ABP in contact in sequence. As Figure 5 shown, water is introduced from the anode, and the generated H2 is released from the cathode. The cathode bipolar plate CBP, the cathode porous transport layer CPTL, and the cathode catalyst layer CCL can use a titanium plate, carbon paper, and Pt / C respectively. The anode porous transport layer APTL can use a titanium-based porous material, such as platinum-plated titanium felt, titanium felt, sintered titanium, etc. The anode bipolar plate ABP can use a titanium plate, etc.

[0102] Deionized water (with a conductivity less than 1 μS / cm) at 80 °C is introduced into the anode, and the membrane is wetted by passing water for 12 h. The protons in the membrane are fully activated by alternately operating at different current densities.

[0103] In one embodiment, hydrogen is introduced into the cathode region of the PEM electrolyzer, and the cathode catalyst layer is used as a reference electrode. The H2 flow rate can be 50 mL / min.

[0104] In one embodiment, the voltage range of the anode relative to the cathode catalyst layer is in the non-Faraday region of the metal oxide, which can be 0.1 - 0.6 V, including but not limited to this. Cyclic voltammetry is used for testing at different scan rates (0.01, 0.02, 0.03, 0.04, 0.05, 0.06 V / s). Thus, the double-layer capacitance current density I c1 of the anode catalyst layer is measured, and the specific double-layer capacitance C dl,MEA is calculated according to the following formula (1):

[0105] C dl,MEA = I c1 / v1 m1catalyst (1)

[0106] Among them, the double-layer capacitance current density I of the anode catalyst layer c1 is in mA / cm 2 .

[0107] The loading m1 of the catalyst per unit area in the anode catalyst layer catalyst is in mg / cm 2 .

[0108] The voltage scanning rate v1 is in V / s,

[0109] The specific double-layer capacitance C dl,MEA is in F / g;

[0110] Thus, the utilization rate U of the anode catalyst can be calculated according to Equation (2),

[0111] U = C dl,MEA / C dl,RDE max (2).

[0112] In this application, the anode catalyst can be selected from respective commercial catalysts, such as various anode metal oxide catalysts applied to PEM water electrolysis for hydrogen production, such as IrO2, IrO2 / TiO2, RuO2, RuO2 / TiO2, etc. When performing PEM tests, appropriate test conditions can be selected according to actual working conditions. For example, the temperature can be 20 - 90 °C and is not limited to normal temperature conditions.

[0113] After the electrode contacts the electrolyte solution, a double layer will be formed at the interface, and thus it can be approximately equivalent to the electrochemically active area of the electrode. The method of this application defines the utilization rate of the catalyst in the ultra-low loading catalytic layer (0.1 μm) in the ideal liquid phase model as 100%, uses the double-layer capacitance measured by it as a benchmark to compare the double-layer capacitance obtained from the membrane electrode test under actual working conditions, and then obtains the utilization rate of the catalyst under actual working conditions. In PEM water electrolysis, only at the three-phase interface (i.e., the interface of proton, electron pathway, and water-gas transmission) is the real active site, and only at the three-phase interface is there a double-layer capacitance response, which thus perfectly fits the calculation of the catalyst utilization rate. Characterizing the membrane electrode through the utilization rate can avoid the problem of waste of active sites caused by excessive stacking of catalysts or uneven distribution of perfluorosulfonic acid resin in actual working conditions, and thus optimize the performance under actual working conditions.

[0114] The method of the present application does not require the use of additional substances for characterizing and calculating the catalyst utilization rate. Instead, it can perform non-destructive testing under operating conditions without introducing external impurities. The method of the present application can test the actual utilization rate of the catalyst of the anode metal oxide in the PEM electrolyzer, so that the optimization of the anode catalyst layer can be guided by the catalyst utilization rate of the anode catalyst layer, providing a guiding basis for reducing the loading of the anode catalyst layer.

[0115] Example

[0116] Example 1

[0117] The catalyst for this test is commercial IrO n (OH) x / TiO2 supported catalyst (Shanghai Heraeus Industrial Technology Co., Ltd., 5011898), the noble metal mass content is 45% Ir.

[0118] First, in the Figure 1 electrolytic cell, the test is carried out according to the above-mentioned ideal 100% catalyst model system test method, and the rotating disk electrode test is carried out by reducing the catalyst loading. Calculate C of different loadings according to formula (3) dl,RDE , and the results are as Figure 6 shown. From Figure 6 obtain the extreme value C of the specific double-layer capacitance C dl,RDE of the 100% ideal model system of the catalyst utilization rate dl,RDE max .

[0119] Disperse the catalyst in the slurry for preparing the membrane electrode assembly (MEA), and prepare a catalyst layer with a Nafion mass content of 5%. The Nafion weight percentage is based on the total weight of the catalyst layer. Thermally press and transfer the catalyst layer onto the proton exchange membrane, and carry out device testing in the Figure 5 PEM electrolyzer, and carry out cyclic voltammetry testing at different voltage scan rates (0.01, 0.02, 0.03, 0.04, 0.05, 0.06 V / s), and the results are as Figure 7 shown. Figure 7 Among them, a1 is the voltage-current density diagram obtained by carrying out cyclic voltammetry testing at different voltage scan rates in the 0.5 - 0.6 V electrochemical window using the catalyst layer containing 5% Nafion; a2 is the double-layer current density at different scan rates obtained in a1, and according to the formula C dl,MEA = I c1 m1 catalyst / v1 perform linear regression on it to obtain the voltage scan rate-double-layer capacitance current density diagram (abbreviated as double-layer current density in the figure), where the slope is the obtained specific double-layer capacitance. Thus, according to Figure 7The specific double-layer capacitance C of the catalyst layer with 5% Nafion content is obtained from a1 and a2 in dl,MEA , and then the anodic catalyst utilization U on the PEM electrolysis membrane electrode is calculated according to Equation (2). The results are shown in Table 1 and Figure 8 .

[0120] Example 2

[0121] The catalyst for this test is commercial IrO n (OH) x / TiO2 supported catalyst (Shanghai Heraeus Industrial Technology Co., Ltd., 5011898), and the noble metal mass content is 45% Ir.

[0122] First, in the Figure 1 electrolytic cell, the test is carried out according to the above-mentioned ideal 100% catalyst model system test method, and the rotating disk electrode test is carried out by reducing the catalyst loading. The C of different loadings is calculated according to Formula (3) dl,RDE , and the results are as Figure 6 shown. From Figure 6 , the specific double-layer capacitance C of the 100% ideal model system of catalyst utilization is obtained dl,RDE extreme value C dl,RDE max .

[0123] The catalyst is dispersed in the slurry for preparing the membrane electrode (MEA), and a catalyst layer with 10% Nafion mass content is prepared. The Nafion weight percentage is based on the total weight of the catalyst layer. The catalyst layer is hot-pressed and transferred onto the proton exchange membrane, and in the Figure 5 PEM electrolytic cell, the device test is carried out, and cyclic voltammetry tests are carried out at different voltage sweep rates (0.01, 0.02, 0.03, 0.04, 0.05, 0.06 V / s). The results are as Figure 7 shown. Figure 7 , where b1 is the voltage-current density diagram obtained by cyclic voltammetry test at different voltage sweep rates in the 0.5 - 0.6 V electrochemical window using the catalyst layer containing 10% Nafion; b2 is the double-layer current density at different sweep rates obtained in b1. According to the formula C dl,MEA = I c1 m1 catalyst / v1, a linear regression is performed on it to obtain the voltage sweep rate - double-layer capacitance current density diagram (abbreviated as double-layer current density in the figure), where the slope is the obtained specific double-layer capacitance. Thus, according to Figure 7 the b1 and b2 in dl,MEA , the specific double-layer capacitance C of the catalyst layer with 10% Nafion content is obtained, and then the anodic catalyst utilization U on the PEM electrolysis membrane electrode is calculated according to Equation (2). The results are shown in Table 1 andFigure 8 。

[0124] Example 3

[0125] The catalyst for this test was a commercial IrO n (OH) x / TiO2 supported catalyst (Shanghai Heraeus Industrial Technology Co., Ltd., 5011898), the noble metal mass content was 45% Ir.

[0126] First, in the Figure 1 electrolytic cell, the test was carried out according to the above-mentioned ideal 100% catalyst model system test method, and the rotating disk electrode test was carried out by reducing the catalyst loading. Calculate C at different loadings according to formula (3) dl,RDE , and the results are as Figure 6 shown. From Figure 6 , the specific double-layer capacitance C of the 100% ideal model system of catalyst utilization was obtained dl,RDE extreme value C dl,RDE max 。

[0127] The catalyst was dispersed in the slurry for preparing the membrane electrode assembly (MEA) to prepare a catalyst layer with a Nafion mass content of 30%, and the Nafion weight percentage was based on the total weight of the catalyst layer. The catalyst layer was hot-pressed and transferred onto the proton exchange membrane, and device tests were carried out in the Figure 5 PEM electrolytic cell, and cyclic voltammetry tests were carried out at different voltage sweep rates (0.01, 0.02, 0.03, 0.04, 0.05, 0.06 V / s). The results are as Figure 7 shown. In Figure 7 , c1 is the voltage-current density diagram obtained by cyclic voltammetry test at different voltage sweep rates in the 0.5 - 0.6 V electrochemical window using a catalyst layer containing 30% Nafion; c2 is the double-layer current density at different sweep rates obtained in c1, and according to the formula C dl,MEA = I c1 m1 catalyst / v1, a linear regression was performed on it to obtain the voltage sweep rate - double-layer capacitance current density diagram (abbreviated as double-layer current density in the figure), where the slope is the obtained specific double-layer capacitance. Thus, according to Figure 7 c1 and c2 in, the specific double-layer capacitance C of the catalyst layer with 30% Nafion content was obtained dl,MEA , and then the anode catalyst utilization U on the PEM electrolysis membrane electrode was calculated according to formula (2). The results are shown in Table 1 and Figure 8 。

[0128] Example 4

[0129] The catalyst for this test was a commercial IrOn (OH) x / TiO2 supported catalyst (Shanghai Heraeus Industrial Technology Co., Ltd., 5011898), the noble metal mass content is 45% Ir.

[0130] First, in the Figure 1 electrolytic cell, the test is carried out according to the above-mentioned ideal 100% catalyst model system test method, and the rotating disk electrode test is carried out by reducing the catalyst loading. Calculate C with different loadings according to formula (3) dl,RDE , and the results are as Figure 6 shown. From Figure 6 the specific double-layer capacitance C of the 100% ideal model system of catalyst utilization is obtained dl,RDE extreme value C dl,RDE max .

[0131] Disperse the catalyst in the slurry for preparing the membrane electrode assembly (MEA), and prepare a catalyst layer with a Nafion mass content of 50%. The Nafion weight percentage is based on the total weight of the catalyst layer. Thermally press and transfer the catalyst layer onto the proton exchange membrane, and in Figure 5 the PEM electrolytic cell, device testing is carried out, and cyclic voltammetry testing is carried out at different voltage sweep rates (0.01, 0.02, 0.03, 0.04, 0.05, 0.06 V / s). The results are as Figure 7 shown. In Figure 7 , d1 is the voltage-current density diagram obtained by cyclic voltammetry testing at different voltage sweep rates in the 0.5 - 0.6 V electrochemical window using the catalyst layer containing 50% Nafion; d2 is the double-layer current density at different sweep rates obtained in d1. According to the formula C dl,MEA =I c1 m1 catalyst / v1, a linear regression is performed on it to obtain the voltage sweep rate-double-layer capacitance current density diagram (abbreviated as double-layer current density in the figure), where the slope is the obtained specific double-layer capacitance. Thus, according to Figure 7 d1 and d2 in dl,MEA , the specific double-layer capacitance C of the catalyst layer with 50% Nafion content is obtained, and then the anode catalyst utilization U on the PEM electrolyzed water membrane electrode is calculated according to formula (2). The results are shown in Table 1 and Figure 8 .

[0132] It is known that in the PEM electrolyzed water anode catalyst layer, increasing the Nafion content of the catalyst layer shows a trend of first increasing and then decreasing in the catalyst utilization. Through the above-mentioned examples, by changing the Nafion content of the anode catalyst layer, the test by this method conforms to the expected results, as shown in Table 1.

[0133] Table 1

[0134]

[0135] At different current densities, in Figure 5 the PEM electrolyzer cell shown, the anode catalyst layers with different Nafion contents obtained in Examples 1-4 were tested. At each current density, the test was carried out for 2 minutes of residence, and an average value was taken by taking a point every 15 seconds to obtain a polarization curve graph, as Figure 9 shown. As Figure 9 shown, the performance of the anode catalyst layers with 5% Nafion content and 10% Nafion content is similar, followed by 30% Nafion, and the worst performance is the anode catalyst layer with 50% Nafion content. The results are consistent with the trend of catalyst utilization rate tested by this method, verifying the accuracy and applicability of this method.

[0136] In Figure 5 the PEM electrolyzer cell shown, the anode catalyst layers with different Nafion contents obtained in Examples 1-4 were electrochemically tested by cyclic voltammetry. The scanning rate was 100 mV / s, and the scanning electrochemical window range was 0.3 - 1.5 V. The cyclic voltammetry test graphs of the anode catalyst layers with different Nafion contents are as Figure 10 shown. As described in the above Examples 1-4, as the Nafion content of the anode catalyst layer increases, the active sites in the catalyst layer will be covered by excessive Nafion, resulting in a decrease in activity. As shown by the cyclic voltammetry test Figure 10 it can be obtained that the performance of the anode catalyst layers with 5% Nafion content and 10% Nafion content is similar, followed by 30% Nafion, and the worst performance is the anode catalyst layer with 50% Nafion content. The results are consistent with the trend of catalyst utilization rate tested by this method, verifying the accuracy and applicability of this method.

[0137] The above has described the present application in combination with preferred embodiments. However, these embodiments are only exemplary and only serve an illustrative role. On this basis, various substitutions and improvements can be made to the present application, and these all fall within the protection scope of the present application.

Claims

1. A method for testing the utilization rate of the anode catalyst in a PEM electrolyzer, comprising: S1 Conducting a rotating disk electrode test, including: S11 Form a catalyst layer in the central region of the rotating disk electrode with the anode catalyst to be tested, obtaining a rotating disk electrode with a catalyst layer, where the loading of the catalyst powder is 0.005 - 0.2 mg / cm 2 , and the thickness of the catalyst layer is 0.05 - 0.5 μm; S12 uses the rotating disk electrode with a catalyst layer as the working electrode to determine the specific double-layer capacitance C dl,RDE ; By reducing the catalyst loading per unit area on the rotating disk electrode and repeating the above S11 and S12, the specific double-layer capacitance C of the ideal model system with 100% catalyst utilization is obtained. dl,RDEmax ; S2 Conducting a PEM electrolyzer test, including: S21 Constructing a PEM electrolyzer, wherein the anode catalyst to be tested forms the anode catalyst layer of the PEM electrolyzer; S22 Perform a cyclic voltammetry test on the PEM electrolyzer at a voltage scan rate v1 to measure the double-layer capacitance current density I of the anode catalyst layer c1 , and calculate the specific double-layer capacitance C of the anode catalyst layer according to the following formula (1) dl,MEA :[[]]END]] C dl,MEA = I c1 / (v1 m1 catalyst ) (1) Among them, the double-layer capacitance current density I of the anode catalyst layer c1 is in mA / cm 2 counting The catalyst loading per unit area in the anode catalyst layer, m1 catalyst in mg / cm 2 2 The voltage sweep rate v1 is in V / s, Specific double-layer capacitance C of the anode catalyst layer dl,MEA in F / g; S3 Calculating the utilization rate U of the anode catalyst according to formula (2), U = C dl,MEA / C dl,RDEmax (2).

2. The method according to claim 1, wherein, In the rotating disk electrode test, cyclic voltammetry tests are performed at different voltage sweep rates v to obtain different voltammetric cyclic curves under the conditions of the same liquid electrolyte system, and the specific double-layer capacitance C is calculated by formula (3). dl,RDE : C dl,RDE = I c / (v m catalyst ) (3) Among them, the double-layer capacitance current density I of the working electrode c is in mA / cm 2 counting The loading m of the catalyst per unit area on the rotating disk electrode catalyst in mg / cm 2 counted The voltage sweep rate v is in V / s, Specific capacitance C dl,RDE is in F / g.

3. The method according to claim 1, wherein The voltage range for the rotating disk electrode test is 0.1 - 0.6V.

4. The method according to claim 1, wherein In the rotating disk electrode test, the specific double-layer capacitance C is determined according to the electrochemical impedance spectrum dl,RDE .

5. The method according to claim 2, wherein In the rotating disk electrode test, the liquid electrolyte system is selected from sulfuric acid solution, perchloric acid solution, sodium hydroxide solution, potassium hydroxide solution.

6. The method according to claim 1, wherein, The PEM electrolyzer includes a cathode plate, a cathode porous transport layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, an anode porous transport layer, and an anode plate in contact in sequence, wherein the cathode porous transport layer is selected from carbon paper, the cathode catalyst layer contains Pt / C, and the anode porous transport layer is selected from titanium-based porous materials.

7. The method according to claim 6, wherein, Hydrogen is introduced into the cathode region of the PEM electrolyzer, and the cathode catalyst layer is used as the reference electrode.

8. The method according to claim 7, wherein The voltage range of the anode of the PEM electrolyzer relative to the cathode is 0.1 - 0.6V.

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