Anode electrode for PEM electrolyzer and method for producing hydrogen

Abstract

The present application relates to an anode electrode for a PEM electrolyzer, and a method for producing hydrogen. An anode electrode for a PEM electrolyzer uses an aqueous solution containing perchlorate, a substrate of the anode electrode comprising, in terms of mass percentage, 22%≤Ni<80%, 95%≤Ni+Fe, and unavoidable impurities, and the aqueous solution containing perchlorate at a concentration of 0.01 mol / L to 1 mol / L; the anode electrode is configured such that, during use of the PEM electrolyzer, at least one surface of the substrate is exposed to the aqueous solution, so that when an anodic polarization potential of 1.4-2.5 VSHE is applied to the anode electrode, a corrosion-resistant passive film can be formed on at least one surface, the passive film comprising nickel oxide and iron oxide, which together account for at least 90% of the passive film in terms of mass percentage. The present application also discloses a PEM electrolyzer, and a steel plate capable of being used to manufacture an anode electrode for a PEM electrolyzer, as well as a use thereof.

Description

Anode electrode for PEM electrolyzer and method for generating hydrogen. Technical Field

[0001] This invention relates to an anode electrode for a PEM electrolyzer and a method for generating hydrogen. The invention also relates to a steel plate suitable for manufacturing the anode electrode and a PEM electrolyzer. Technical Background

[0002] With the rapid development of the global low-carbon economy, the combustion of hydrogen, which does not produce greenhouse gases, and its preparation have attracted widespread attention. Currently, one of the important industrial methods for producing hydrogen is water electrolysis, which can produce hydrogen with a purity of over 99%. Water electrolysis mainly includes the following technologies: alkaline water electrolysis (AWE), solid polymer proton exchange membrane (PEM) water electrolysis, solid polymer anion exchange membrane (AEM) water electrolysis, and solid oxide (SOE) water electrolysis. From a technical perspective, PEM water electrolysis technology is expected to be widely applied due to its advantages such as high current density, small electrolyzer volume, and the absence of corrosive electrolyte solutions.

[0003] However, the PEM electrolyzers currently used in PEM water electrolysis technology face challenges in widespread adoption. During water electrolysis, the hydrogen evolution reaction (HER) occurs at the cathode and the oxygen evolution reaction (OER) occurs at the anode. The theoretical potential for water electrolysis is 1.23V. SHE However, in practical applications, to ensure the above reaction occurs, the applied anodic polarization potential will be higher than 1.23V. SHE This is because electrochemical reactions typically require overcoming an additional energy barrier. Therefore, the anodic polarization potential applied during electrolysis is usually 1.4–2.2 V. SHE (The following will be greater than 1.23V) SHE The anodic polarization potential is referred to as "high potential". On the other hand, although PEM water electrolyzers use pure water as the reactant, the Nafion proton exchange membranes commonly used in industry contain sulfonic acid (-SO3H) groups. These groups release protons in the hydrated state, creating a strongly acidic environment. Therefore, the anode of a PEM electrolyzer needs to withstand a high anodic polarization potential (1.4–2.2V). SHE It also needs to withstand a strong acid environment (usually pH 1-2).

[0004] Only a few metal materials in nature can be resistant to corrosion under such strong acid and high potential conditions, such as titanium (Ti), gold (Au), platinum (Pt), and iridium (Ir). Except for Ti, these metal elements are extremely rare and expensive. However, a pure Ti electrode will generate a dense and poorly conductive passivation film on its surface in situ during actual operation, which increases the internal resistance of the electrolytic cell and reduces the hydrogen production efficiency. Currently, the commercially viable solution is to use a pure Ti anode gas diffusion layer coated with Au or Pt, and then add noble metal iridium oxide (IrO2) nanoparticles as an anode catalyst for electrolytic water hydrogen production. This not only leads to high costs of PEM electrolytic cells, but also makes it difficult for PEM water electrolysis technology to be widely promoted and applied due to the use of rare noble metal materials. At the same time, pure Ti also faces problems such as poor forming ability and high processing cost. Therefore, there is a need to seek a cheap anode material that can be used in PEM electrolytic cells to reduce the cost of PEM electrolytic cells.

[0005] To this end, researchers have conducted research on anode materials suitable for PEM electrolytic cells.

[0006] A research paper by K.P. Yu et al. (Yu K, Feng S, Ding C, et al. A sequential dual-passivation strategy for designing stainless steel used above water oxidation [J]. Materials Today, 2023, 70: 8-16.) reports a sequential dual-passivation strategy for designing stainless steel containing manganese (Fe-20.73Cr-20.2Co-17.7Mn-1.7Si, wt.%) based on the Cr and Mn elements. On the basis of chromium passivation, manganese passivation can protect the specific composition of stainless steel substrate in simulated seawater and 1.9V SHE The following anode polarization potential conditions do not occur corrosion. Although this material is cheaper than the aforementioned noble metals, it is worth noting that the corrosion resistance mechanism in simulated seawater is different from that in strong acid, as the stability of the passivation film in an acidic environment is generally worse than in a neutral environment. Therefore, it cannot be ensured that this material can be used as an anode electrode for long-term stable use in the process of generating hydrogen using a PEM electrolytic cell.

[0007] Larsson et al. (Larsson A, Grespi A, Abbondanza G, et al. The oxygen evolution reaction drives passivity breakdown for Ni-Cr-Mo alloys [J]. Advanced Materials, 2023, 35(39): 2304621) reported a Ni-Cr-Mo alloy (62.3 at.% Ni, 26.3 at.% Cr, and 9.7 at.% Mo) that can undergo the water electrolysis oxygen evolution reaction in both neutral and acidic solution conditions. No Cr-element-derived overpassivation corrosion, which is generally believed to occur, was observed in the alloy under the high-potential conditions of water electrolysis. However, a large amount of hexavalent molybdenum ions (Mo 6+ ) produced in the passive film thereof during this period caused the alloy to undergo significant grain boundary corrosion, indicating that the passivation mechanism based on Cr and Mo elements cannot inhibit the alloy from undergoing significant corrosion or ion elution under strong acid, high-potential conditions.

[0008] In view of the above, there is still a need to improve the PEM water electrolysis technology to be able to produce hydrogen gas stably for a long time at a reduced cost. SUMMARY

[0009] The present application is made in view of the above problems existing in the prior art.

[0010] One of the objects of the present application is to provide an anode electrode for a PEM electrolyzer that uses an aqueous solution containing perchlorate, wherein the base body of the anode electrode contains, in mass percent: 22%≤Ni<80%, 95%≤Ni+Fe, and unavoidable impurities, the aqueous solution containing perchlorate at a concentration of 0.01 mol / L to 1 mol / L,

[0011] wherein the anode electrode is configured such that, during use of the PEM electrolyzer, at least one surface of the base body of the anode electrode is exposed to the aqueous solution, so that a corrosion-resistant passive film can be formed on the at least one surface when an anodic polarization potential of 1.4~2.5V SHE is applied to the anode electrode, the passive film including nickel oxide and iron oxide, both of which account for at least 90% of the passive film in mass percent.

[0012] In one embodiment, the base of the anode electrode contains, in mass percent: 27% < Ni < 42%, 95% < Ni + Fe, and unavoidable impurities. In another embodiment, the base of the anode electrode contains, in mass percent: 29% < Ni < 38%, 95% < Ni + Fe, and unavoidable impurities. In yet another embodiment, the base of the anode electrode contains, in mass percent: 30% < Ni < 36%, 95% < Ni + Fe, and unavoidable impurities, to obtain further improved acid and high potential corrosion resistance.

[0013] In another embodiment, the base of the anode electrode further contains one or more additional alloying elements in a total content of less than 5%, preferably not more than 2%, more preferably not more than 1%. The one or more additional alloying elements can be selected from the group consisting of: P < 0.1%, S < 0.1%, B < 0.1%, N < 0.1%, Si < 1%, C < 1%, Ti < 2%, W < 2%, Al < 2%, V < 2%, Cu < 2%, Zr < 2%, Nb < 2%, REM < 0.1%, for example, C + W + Nb + La + B < 2%.

[0014] Another object of the present application is to provide a PEM electrolyzer employing an aqueous solution containing perchlorate, which comprises:

[0015] a proton exchange membrane;

[0016] an anode electrode, which is the aforementioned anode electrode that realizes both the functions of an anode catalyst and a gas diffusion layer, wherein the anode electrode is configured to provide a flow passage for the aqueous solution within the electrolyzer;

[0017] a cathode electrode that sandwiches the proton exchange membrane with the anode electrode;

[0018] a bipolar plate that is disposed opposite to and spaced apart from the anode electrode and the cathode electrode, which provides a passage for the supply of the aqueous solution and the discharge of the product;

[0019] and

[0020] a reservoir for containing the aqueous solution containing perchlorate to immerse the combined structure of the proton exchange membrane, the anode electrode, and the cathode electrode and the surfaces of the bipolar plate opposite to the anode electrode and the cathode electrode, respectively, wherein the concentration of perchlorate in the aqueous solution is 0.01 to 1 mol / L.

[0021] Still another object of the present application is to provide a method of generating hydrogen gas using a PEM electrolyzer, the method comprising:

[0022] connecting a power source to a cathode electrode and an anode electrode of a PEM electrolyzer, wherein a proton exchange membrane is interposed between the cathode electrode and the anode electrode, the anode electrode comprising, in mass percentage: 22% < Ni < 80%, 95% < Ni + Fe, and inevitable impurities;

[0023] adding an aqueous solution containing perchlorate in a range of 0.01 to 1 mol / L to a reservoir of the PEM electrolyzer; and

[0024] applying an anodic polarization potential in a range of 1.4 to 2.5 V SHE to the anode electrode to produce oxygen gas, while simultaneously producing hydrogen gas at the cathode electrode.

[0025] It is well known that the strongly acidic environment at the anode in a PEM electrolyzer is due to the Nafion proton exchange membrane containing sulfonic acid (-SO3H) groups, which release protons in a hydrated state, thus creating a strongly acidic environment. Therefore, it is common in the art to use a sulfuric acid solution to simulate this strongly acidic environment to test the stability of an anode electrode. Notably, PEM electrolyzers typically use pure water as the aqueous solution without additional ions. In contrast, to reduce the cost of hydrogen production in a PEM electrolyzer, the present application inventively calls for the use of the combination of the anode electrode of the present application and an aqueous solution containing perchlorate in a range of 0.01 to 1 mol / L and having a pH < 7.

[0026] The present inventors have inventively discovered that by using the combination of an aqueous solution containing perchlorate and the above anode electrode, once electrolysis of water is initiated, i.e., an anodic polarization potential in a range of 1.4 to 2.5 V SHE is applied to the anode electrode, the anode electrode is capable of spontaneously forming a dense passivation film on its surface exposed to the aqueous solution, according to the following reactions: 2Fe + 3H2O → Fe(III)2O3 + 6H + ……………….……..(Equation 1) Ni + H2O → Ni(II)O + 2H + …………………………..(Equation 2)

[0027] The Roman numerals in the above brackets represent the chemical valence of the metal elements.

[0028] The passivation film makes the anode electrode have strong corrosion resistance or low total metal ion dissolution rate during electrolysis of water, so that the anode electrode can be used for generating hydrogen gas stably for a long time. Therefore, it will be understood that, since the Nafion proton exchange film will create a strong acid environment, the water solution is essential to contain 0.01-1 mol / L of perchlorate ions at a pH not greater than 7, without necessarily requiring its pH to be 0-2.

[0029] The anode electrode adopts iron-nickel alloy, which significantly reduces the cost of manufacturing the anode electrode. Moreover, since the PEM electrolyzer according to the application adopts the combination of the anode electrode and the water solution, the anode electrode of the application can achieve the technical effect of acid and high potential corrosion resistance without special corrosion prevention treatment on its surface before use, thereby simplifying the manufacturing process and cost of the PEM electrolyzer. Furthermore, the passivation film can be spontaneously formed on the anode electrode according to the application during hydrogen generation, which can protect the anode while realizing the function of the anode catalyst. In other words, the anode electrode according to the application can play the functions of both the anode catalyst and the gas diffusion layer, so that the application of additional anode catalyst can be at least partially reduced or eliminated, thereby further saving cost.

[0030] Yet another object of the application is to provide a steel sheet comprising a base body and a passivation film on at least one surface of the base body, wherein the base body comprises, in mass percent: 22%≤Ni<80%, 95%≤Ni+Fe, and unavoidable impurities, and wherein the passivation film comprises nickel oxide and iron oxide, both in mass percent at least 90% of the passivation film.

[0031] Preferably, the thickness of the passivation film is in the range of 3-12 nm, and the nickel oxide accounts for 30-65% in mass percent in the passivation film.

[0032] Preferably, before the passivation film is generated on the base body of the steel sheet, the base body is heated to 1000-1300℃ in a vacuum environment or a protective atmosphere for 6-20 hours for homogenization treatment.

[0033] The present application also relates to the use of said steel sheet in a PEM electrolyser employing an aqueous solution containing perchlorate. Said steel sheet can be used to make an anode electrode which can be used in a PEM electrolyser employing an aqueous solution containing perchlorate containing perchlorate at a concentration comprised between 0.01 mol / L and 1 mol / L to carry out a process for the production of hydrogen. It will be understood that, as mentioned previously, said passivation film can form spontaneously during the use of the anode electrode in the PEM electrolyser, so that it is also possible to consider making the anode electrode directly from the substrate of the steel sheet described above (i.e. after the homogenisation treatment and before the production of the passivation film thereon).

[0034] The skilled person will understand that all ranges include the end values, and that any range or any value within each interval described above applies to the present application, unless explicitly stated otherwise. For example, the applied potential can be 1.7-2.5 V SHE , 1.8-2.4 V SHE , 1.9-2.5 V SHE , 2.0-2.5 V SHE , 1.95-2.45 V SHE , etc. The content of Ni in the substrate of the anode electrode or of the steel sheet can be 23-60%, 25-41%, 28-55%, 24-50%, 30-70%, etc. BRIEF DESCRIPTION OF DRAWINGS

[0035] The embodiments, features and advantages of the present application will become clear from the following description, taken in conjunction with the accompanying drawings, in which:

[0036] Figure 1 shows a high-resolution transmission electron microscope image of the passivation film obtained for a test specimen S1 according to an embodiment of the present application, kept for 24 hours in a perchloric acid solution at pH = 2 at an anodic polarisation potential of 2.5 V SHE ;

[0037] Figure 2 shows high-resolution transmission electron microscope images of the passivation film obtained for (a) test specimen S5 and (b) test specimen S7 according to embodiments of the present application, kept for 24 hours in a perchloric acid solution at pH = 1 at an anodic polarisation potential of 2.5 V SHE ;

[0038] Figure 3 shows (a) surface corrosion morphology and (b) cross-section corrosion morphology obtained for a comparative test specimen C1 kept for 1 hour in a perchloric acid solution at pH = 1 at an anodic polarisation potential of 2.5 V SHE ;

[0039] Figure 4 shows high-resolution transmission electron microscope images of the passivation film obtained for test specimen S7 according to an embodiment of the present application, kept for 24 hours in a perchloric acid solution ((a) and (b)) and in a sulphuric acid solution ((c) and (d)) at an anodic polarisation potential of 2.5 V SHEobtained by keeping the sample S5 at an anodic polarization potential of 2.5 V for 24 hours in a perchloric acid solution with pH = 1 ;

[0040] Figure 5 shows the X-ray photoelectron spectroscopy of the passivation film obtained by keeping the sample S5 at an anodic polarization potential of 1.0 V SHE , 1.6 V SHE and 2.5 V SHE for 3 hours in a perchloric acid solution with pH = 1 according to an embodiment of the present application;

[0041] Figure 6 shows the element distribution trend diagram of the passivation film obtained by keeping the sample S1 at an anodic polarization potential of 2.5 V SHE for 24 hours in a perchloric acid solution with (a) pH = 2 and (b) pH = 1 according to an embodiment of the present application; and

[0042] Figure 7 shows the element distribution trend diagram of the passivation film obtained by keeping (a) the sample S5 and (b) the sample S7 at an anodic polarization potential of 2.5 V SHE for 24 hours in a perchloric acid solution with pH = 1 according to an embodiment of the present application. DETAILED DESCRIPTION

[0043] The present application will be further described in conjunction with the specific embodiments, and the examples given are only for illustrating the present application, but not for limiting the scope of the present application. The description herein about the content of chemical elements refers to the weight percentage, which is abbreviated as %. Unless specifically indicated, the various preferred schemes can be freely combined as needed. Those skilled in the art will understand that the data and various parameters recorded in the examples are only exemplary, and do not constitute a limitation on the present application.

[0044] Solution preparation

[0045] The perchloric acid (65%), sulfuric acid (98%), ethanol and acetone used are commercially available analytical pure products. All reactant solutions are prepared using deionized water with a resistivity of 18.2 Ωm.

[0046] The perchloric acid solution is prepared from deionized water and perchloric acid, with pH = 0, 1, 2, and containing 1 mol / L, 0.1 mol / L, 0.01 mol / L of perchlorate, respectively. The perchloric acid solution can also contain a small amount of other anions, such as chloride ions, sulfate ions, etc. (<0.1 mol / L), and any metal cations that do not form precipitates with perchlorate, such as sodium ions, iron ions, nickel ions, calcium ions, etc.

[0047] The sulfuric acid solution is prepared from deionized water and 1 mol / L sulfuric acid, with pH = 0.

[0048] The skilled person will understand that in the actual use of a PEM electrolyzer to produce hydrogen, the anode electrode will necessarily be in a strongly acidic environment due to the presence of sulfonic acid groups in the proton exchange membrane, even if the PEM electrolyzer is using pure water for electrolysis. Therefore, the aqueous solution used for the PEM to produce hydrogen does not need to be a solution of perchloric acid, it is sufficient that it has a pH < 7, and it is necessary that it contains perchlorate in a concentration of 0.01-1 mol / L. The solution is configured here with a pH of 0-2 to simulate the strongly acidic environment in which the anode electrode is in the actual use of a PEM electrolyzer. According to the present application, the PEM electrolyzer will use an aqueous solution instead of pure water with a pH < 7 and containing perchlorate in a concentration of 0.01-1 mol / L. In this case, in the actual use, the anode electrode will be in an acidic environment containing perchlorate, the presence of which in sufficient quantity will inhibit the adsorption of sulfonic acid groups on the surface of the anode electrode and promote the adsorption of OH groups, thus promoting the passivation behavior and inhibiting corrosion.

[0049] Sample preparation

[0050] Each steel plate with the components shown in Table 1 was prepared, and the corresponding manufacturing process was as follows:

[0051] a) The high-purity raw materials mixed in the proportions according to Table 1 were melted and solidified in an arc furnace using the method of arc melting to obtain ingots. For alloy price and impurity removal cost considerations, the ingots and thus the steel plate substrate / anode electrode for a PEM electrolyzer can contain no more than 5% of other alloying elements, such as one or more of the following elements: C, Si, B, N, S, P, Ti, Al, W, V, Nb, Ni, Cu, Co, Sn, Sb, Mg, Zr, and rare earth elements (REM), etc., the presence of which does not affect the solution of the technical problems of the present application.

[0052] b) The ingots were subjected to homogenization treatment to make the alloying elements uniformly distributed to obtain the best corrosion resistance. Preferably, the process is: heating the ingot to 1000-1300 °C in a vacuum environment or argon protective atmosphere, holding for 6-20 hours, and then cooling in the furnace. In the present application, homogenization treatment was carried out at 1220 °C for 12 hours. It will be understood that any combination of values within the aforementioned ranges can be used for homogenization treatment. For example, holding at 1100 °C for 15 hours, or at 1250 °C for 4 hours. It is worth noting that the homogenization process is an important prerequisite for the anode electrode of the present application to be able to form a dense passivation film during use. This is because if the material is not uniform, local galvanic cell reactions will occur in the presence of strong acid and high potential, promoting local corrosion and inhibiting the formation of a passivation film.

[0053] c) Cutting several 10 mm x 10 mm x 2 mm blocks from the homogenized ingot;

[0054] d) After surface polishing to brightness using 80, 240, 1200 grit sandpaper, the blocks were sequentially washed with water and ultrasonically cleaned in ethanol solution. The samples were then dried and used as is for electrochemical testing.

[0055] Table 1. Composition of the steel plates of the examples and comparative examples (%; the balance is Fe and other unavoidable impurities)

[0056] Test method

[0057] The example samples S1-S10 and comparative example samples C1-C5 were connected to pure Ti or pure Pt wires by spot welding in order to immerse the samples completely in the solution during testing. The test area of each sample was measured before testing.

[0058] The example samples S1-S10 and comparative example samples C1-C5 were tested by a three-electrode electrochemical test method in this application, using a mercury amalgam electrode (Hg / Hg2SO4) as the reference electrode, the prepared sample as the working electrode (anode), and a platinum sheet electrode as the counter electrode (cathode). Since the electrochemical test was performed in an acidic solution, in the three-electrode system, the mercury amalgam electrode was selected as the reference electrode, and the conversion formula between the mercury amalgam electrode and the standard hydrogen electrode (SHE) is: SHE V Hg / Hg2SO4 + 0.656 V. If not otherwise specified, the potential values described below have been converted to SHE.

[0059] Passivation state test

[0060] The passivation potential given in the second column of Table 2 was applied to the corresponding sample (i.e., the working electrode, which is actually equivalent to the state of the anode electrode of the PEM electrolyzer during water electrolysis) and maintained for 30 minutes, and the current density of each working electrode was recorded and listed in Table 2. The purpose of recording the current at this passivation potential is to check whether the sample has reached a passivation state, and generally requires an average current of no more than a threshold current of 5 μA / cm 2 If it is much larger than this threshold, it indicates that the passivation state of the sample is not complete or no passivation has occurred and more significant corrosion will occur at a higher potential. Within the composition range of the present application, the reason for this situation can be that the homogenization treatment during the manufacture of the sample is not good, resulting in local areas lacking Ni or having too much Ni, so that a current close to the mA level occurs, and the passivation state cannot be reached.

[0061] In the case where the passivation state can be reached, the open circuit potential (OCP) of the sample was measured, and the sample was then subjected to a potentiostatic test at 2.5 V SHEAn anodic polarization potential is applied to the working electrode to determine whether or not overpassivation is present. Generally, if a material is corroding, a visible change in the surface of the material will occur. Thus, if a material does not undergo a visible, rapid dissolution or corrosion, it is considered to be not overpassivated, but rather remains passivated and is able to be used at high potentials.

[0062] These tests ensure that an anode electrode made of a material that meets the requirements is able to spontaneously passivate within the range from the passivation potential to 2.5 V SHE in a PEM electrolyzer using an aqueous solution containing perchlorate ions, so that the desired anodic polarization potential (such as any potential in the range from 1.4 to 2.5 V SHE can be applied directly to the anode electrode when electrolyzing water, without the need for a pretreatment such as prepassivation of the surface of the anode electrode, thereby saving costs.

[0063] Corrosion rate measurement

[0064] When the oxygen evolution reaction occurs on the surface of the anode electrode, the anodic polarization current increases. However, this increase does not mean that the anode electrode is corroding. In order to avoid unnecessary confusion, the present application uses the metal ion elution rate of each sample to represent the corrosion rate. The greater the metal ion elution rate, the more severe the corrosion under the conditions. The ion elution rate is measured using inductively coupled plasma mass spectrometry (ICP-MS), as follows:

[0065] After passivation treatment according to the foregoing, the anodic polarization potential is increased to 2.5 V SHE . On average, 0.5 mL of a solution sample is extracted every 1 hour, and after the solution sample is diluted 100 times, inductively coupled plasma mass spectrometry (ICP-MS) is performed. Each experiment is at least 6 hours long to extract at least 6 samples to obtain an average ion elution rate, which has been corrected according to the dilution factor. The surface morphology of each sample is observed after the test. Each sample is tested at least three times to obtain the final average value. The results are listed in Table 2.

[0066] Passivation film cross-sectional observation

[0067] An anodic polarization potential of 2.5 V SHE is applied to the working electrode in a perchloric acid solution, and a constant potential method is used for 24 hours, and after cleaning and drying, the passivation film to be tested is obtained.

[0068] The thickness of the passivation film obtained is very thin, generally only a few nanometers, so the present application uses a transmission electron microscope (TEM) to observe it, the model of which is Talos F200X, equipped with a high-angle annular dark-field probe (HAADF) and a Super-X EDS spectrometer, with an acceleration voltage of 200 kV. Before observation, a layer of Au-Pd alloy protective layer is plated on the passivation film using the method of ion sputtering, and then the sample is placed in a focused ion beam (FIB) microscope to prepare a TEM sample using the "lift-out method", with an ion acceleration voltage of 30 kV. After the sample is prepared, it is observed in the TEM using a scanning mode (STEM), and HAADF dark field topography images and EDS energy spectrum information are obtained. The average thickness of the passivation film of each sample is measured: at least 3 positions on the cross section of each sample are measured, and then the average value is taken. The average thickness results of each passivation film are listed in Table 3.

[0069] Passivation film related parameter test

[0070] The present application uses X-ray photoelectron spectroscopy (XPS) to obtain the valence state and relative content information of the passivation film on the sample, the instrument model is Thermo Scientific ESCALAB Xi+. Different elements and different valence states of the same element have their characteristic peaks in the spectrum, and the intensity and peak area of the characteristic peaks are related to the content of the specific element, so more detailed composition information about the passivation film can be obtained in combination with the above EDS results, which is listed in Table 3.

[0071] Table 2. Test conditions and results of each sample (using perchloric acid solution)

[0072] Table 3. Passivation film related parameters of each sample (using perchloric acid solution, at 2.5V SHE for 24 hours)

[0073] From the data in Table 2, at a certain passivation potential, both the example samples S1-S10 (equivalent to an anode electrode) of the present application and the comparative example samples C1-C5 obtained a passivation current of 5 μA / cm 2 The following passivation current indicates that the surface of each sample has produced a stable passivation film and no significant corrosion or metal ion dissolution has occurred.

[0074] However, when anodic polarization is carried out at 2.5V SHE The comparative example samples and the example samples according to the present application exhibit significantly different performances.

[0075] Specifically, the average dissolution rate of Fe ions of the example samples S1-S10 does not exceed 200 ppb / h / cm 2Furthermore, the average dissolution rate of Ni ions does not exceed 100 ppb / h / cm. 2 Even in a strongly acidic environment with a pH of 0, under conditions of pH 1–2 (typically, the anode electrode of a PEM electrolyzer is under these conditions), the sum of the average dissolution rates of Fe ions and Ni ions is less than 100 ppb / h / cm². 2 It exhibits excellent corrosion resistance.

[0076] For example, Figure 1 shows the sample S1 of Example 1 in a perchloric acid solution at pH = 2 at 2.5V. SHE A high-resolution transmission electron microscope image of the passivation film obtained after 24 hours of exposure to light is shown. The protective layer is a thin Au-Pd fine-grained film deposited before surface morphology observation to prevent damage to the passivation film. As shown in Figure 1, the passivation film is a dense structure between the substrate and the protective layer, and the boundaries between them are shown by white dashed lines. The thickness of the passivation film is in the range of 3-5 nm, with an average thickness of ~4 nm. No lattice fringes are observed in the passivation film, and the corresponding Fourier transform (FFT) image also shows a typical amorphous pattern. Figure 2 shows (a) sample S5 and (b) sample S7 of the embodiment of the present invention in a perchloric acid solution at pH = 1 at 2.5V. SHE The high-resolution transmission electron microscopy image shows the passivation film obtained after maintaining the anodic polarization potential for 24 hours. As shown, a dense passivation film also exists on the surface of samples S5 and S7, which appears as a layer with high contrast between the substrate and the white Au-Pd protective layer. The average thicknesses of the passivation film in S5 and S7 are approximately 5 nm and approximately 8 nm, respectively. This passivation film protects the substrate of samples S5 and S7 from corrosion, thus exhibiting a very low metal ion dissolution rate.

[0077] After 24 hours, samples S1, S5, and S7 still possessed a dense passivation film, demonstrating their long-term stability under strong acid and high potential, thus making them suitable for long-term hydrogen production processes. This also applies to other embodiments according to the present invention.

[0078] In contrast, comparative samples C1-C5 exhibited faster metal ion dissolution rates, regardless of whether they were Fe or Ni ions, and the final sample surfaces showed a corroded surface morphology. For example, compared to example sample S1, the Fe ion dissolution rate of comparative sample C1 increased by nearly 36.7 times, and the average Ni ion dissolution rate increased by nearly 66.7 times, showing a corrosion trend. Figure 3 shows the reaction of comparative sample C1 in perchloric acid solution at pH 1 at 2.5V. SHEFigure 3 shows the surface corrosion morphology (a) and cross-sectional corrosion morphology (b) of Comparative Sample C1 obtained after 1 hour of anodic polarization at 1.2 V. The surface of C1 has already appeared corrosion features such as corrosion products after 1 hour at high potential, confirming that Comparative Sample C1 is not resistant to corrosion at high potential. This is because the Ni content (21%) of the substrate in C1 is not sufficient to form a complete inner layer of nickel oxide, leading to severe internal oxidation (as shown in Figure 3), thus causing rapid dissolution of ions within the substrate.

[0079] For another example, compared to Example Sample S10, both Fe and Ni ions of Comparative Sample C2 exhibit significantly high dissolution rates, and its final surface morphology also appears corrosion features such as corrosion products. This is because the nickel content (80%) is too high, thus leading to an incomplete and insufficiently dense outer layer of iron oxide, which causes accelerated dissolution of the inner layer of nickel element. Therefore, to ensure the corrosion resistance (i.e. low metal ion dissolution rate) of the anode electrode during electrolysis of water, the present application requires the Ni content of the anode electrode to be in the following range: 22% < Ni < 80%.

[0080] Furthermore, compared to Example Sample S5, Comparative Sample C5 additionally contains 20% of Cr. Cr element is generally considered to cause passivation of steel materials, but the inventors of the present application found that the addition of Cr substantially leads to negative results. Both Fe and Ni ions of Sample C5 exhibit significantly high metal dissolution rates, and its final surface morphology appears corrosion features such as corrosion products. This is because the Cr element at 1.2 V SHE This leads to over-passivation corrosion, causing iron and nickel to fail to form a complete and effective passivation film structure, which cannot inhibit the dissolution of the substrate ions under high potential conditions, thus appearing corrosion morphology. Similarly, Comparative Samples C3 and C4, which respectively contain Mo and Mn elements, also exhibit significantly high metal ion dissolution rates. Therefore, to ensure the corrosion resistance (i.e. low metal ion dissolution rate) of the anode electrode during electrolysis of water, the present application requires the anode electrode to contain as little Cr, Mn, Mo as possible, preferably not containing Cr, Mn, Mo.

[0081] On the other hand, the reason why the various embodiments of the present application are also able to have low metal ion dissolution rates at high potentials of 2.5 V SHE in strong acid is because once the electrolysis of water is started (i.e. high electrolysis potential is applied to the anode electrode), a dense passivation film is spontaneously formed on the surface of the sample by the reaction of perchlorate with the sample, as shown in Figures 1 and 2.

[0082] It is worth noting that the formation of the passivation film in this application has its own unique characteristics. Since the Nafion proton exchange membranes commonly used in industry contain sulfonic acid groups and use ultrapure water as the solution, sulfuric acid solution is typically used as the electrolyte in the prior art to simulate the strongly acidic environment of the anode electrode. However, the passivation film of this invention cannot be formed in a sulfuric acid environment, for the following reasons.

[0083] Figure 4 shows the results of an embodiment of the present invention, in perchloric acid solution ((a) and (b)) and sulfuric acid solution ((c) and (d)) at 2.5V. SHE The surface morphology obtained after maintaining the sample at the anodic polarization potential for 24 hours, with the pH of both the perchloric acid and sulfuric acid solutions being 0. As shown in Figures 4(a) and (b), no obvious corrosion morphology or corrosion products were generated on the surface of sample S7 in the perchloric acid solution. This is because the adsorption capacity of perchlorate ions is very weak, and no adsorption reaction will occur on the sample surface even at very high potentials. Therefore, the reactions shown in Equations 1 and 2 above can be successfully carried out on the sample surface to form a dense passivation film, which effectively reduces the dissolution rate of metal ions, resulting in no obvious corrosion morphology or corrosion products on the sample surface.

[0084] In contrast, as shown in Figures 4(c) and (d), sample S7 corroded in sulfuric acid solution. This is because sulfate ions have a strong adsorption capacity at concentrations greater than 1.8V. SHE At the anodic polarization potential, sulfate ions preferentially adsorb onto the sample surface, producing a loose, porous sulfate product. This product lacks protective properties at high potentials, leading to severe surface corrosion. Therefore, to make the anode electrode of this invention suitable for hydrogen generation in a PEM electrolyzer, appropriate amounts of perchlorate ions must be added to high-purity water to form a dense passivation film on the anode electrode surface; otherwise, the technical effects described in this invention cannot be achieved. Insufficient perchlorate ions are insufficient to prevent the adsorption of sulfonic acid groups from the proton exchange membrane onto the anode electrode surface, thus failing to effectively promote passivation. Therefore, the concentration of added perchlorate ions must be no less than 0.01 mol / L. On the other hand, considering cost, the concentration of added perchlorate ions must be no more than 1 mol / L.

[0085] In view of the above, in order to generate hydrogen at low cost, this application proposes that, on the one hand, the Ni content in the iron-nickel alloy should be reasonably selected (22% ≤ Ni < 80%), and on the other hand, the aqueous solution (pH ≤ 7) should contain perchlorate ions at a concentration of 0.01–1 mol / L. Only through the synergistic effect of these two factors can a corrosion-resistant passivation film be spontaneously generated in situ on the surface of the anode electrode at a high anodic polarization potential (such as a potential suitable for water electrolysis), thereby obtaining an anode electrode resistant to strong acids and high-potential corrosion for long-term stable hydrogen generation.

[0086] The results above indicate that materials such as samples S1-S10 can be used to fabricate anode electrodes for PEM electrolyzers employing aqueous solutions containing perchlorate, wherein the substrate of the anode electrode comprises, by mass percentage: 22% ≤ Ni < 80%, 95% ≤ Ni + Fe, and unavoidable impurities, and the aqueous solution contains perchlorate at a concentration of 0.01–1 mol / L and has a pH ≤ 7.

[0087] The anode electrode is configured such that, during use of the PEM electrolyzer, at least one surface of the anode electrode substrate is exposed to the aqueous solution, such that a voltage of 1.4–2.5V is applied to the anode electrode. SHE When the anodic polarization potential is reached, a corrosion-resistant passivation film can be formed on the at least one surface, the passivation film comprising nickel oxide and iron oxide, which together account for at least 90% of the passivation film by mass percentage.

[0088] Because this anode electrode can spontaneously form a passivation film on its surface under the anodic polarization potential of water electrolysis, it exhibits excellent corrosion resistance during hydrogen production in a PEM electrolyzer without any surface treatment (total Fe+Ni ion dissolution rate not exceeding 300 ppb / h / cm). 2 This simplifies the manufacturing process and reduces the cost of PEM electrolyzers.

[0089] Preferably, the anode electrode contains, by mass percentage: 22% ≤ Ni ≤ 42%, 95% ≤ Ni + Fe, and unavoidable impurities, for the following reasons. As shown in Table 2, S9 and S10, at pH 2, 2.5V SHE The Ni ion dissolution rate is higher than 10 ppb / h / cm. 2 In contrast, samples S1-S7, in a more acidic solution (pH 1) at the same potential, exhibited a Ni ion dissolution rate of no more than 10 ppb / h / cm. 2 This results in superior corrosion resistance. Specifically, compared to S1-S7, the higher Ni content in S9 and S10 promotes the Ni ion dissolution rate. Therefore, to obtain better corrosion resistance, a Ni content in the iron-nickel alloy within the range of 22% to 42% is preferred.

[0090] Furthermore, the total dissolution rate of Fe+Ni ions in samples S1-S7 showed a trend of first decreasing and then increasing with the increase of Ni content. Specifically, from S1 at 86 ppb / h / cm 2 Reduced to 61.8 ppb / h / cm in S3. 2 It was then reduced to 43.2 ppb / h / cm at S5. 2, then presents an ascending trend up to 60.4 ppb / h / cm for S7 2 S5 has the lowest total Fe+Ni ion release rate. The above trend is related to the change of the crystal structure of the matrix. When the Ni content is below 30%, the martensite phase (body-centered cubic structure BCC) present in the matrix decreases gradually with the increase of the Ni content. When the Ni content is greater than 30%, the matrix is entirely composed of austenite phase (face-centered cubic structure FCC). When the Ni content is between 30% and 31%, although the matrix is in FCC structure at room temperature, its stability is weak and it is easy to transform to BCC phase under the influence of the environment, such as mechanical friction, temperature, voltage, etc. For example, the total ion release rate of S4 is slightly greater than that of S5, which is likely due to the transformation of the surface layer to BCC phase introduced during polishing. When the Ni content reaches 33% to 34%, the FCC structure of the matrix is stable enough and no transformation from FCC to BCC will occur unless there are serious environmental factors. Under the same composition, the BCC phase usually has a higher corrosion rate than the FCC phase. Therefore, considering the influence of the Ni content and the crystal structure on the ion dissolution rate, preferably, the matrix of the anode electrode comprises 27%≤ Ni≤ 42%, 95%≤ Ni+Fe, and unavoidable impurities in mass percentage, so as to obtain a total Fe+Ni ion release rate of not more than 65 ppb / h / cm 2 More preferably, the matrix of the anode electrode comprises 29%≤ Ni≤ 38%, 95%≤ Ni+Fe, and unavoidable impurities in mass percentage, so as to obtain a total Fe+Ni ion release rate of not more than 55 ppb / h / cm 2 Still more preferably, the matrix of the anode electrode comprises 30%≤ Ni≤ 36%, 95%≤ Ni+Fe, and unavoidable impurities in mass percentage, so as to obtain a total Fe+Ni ion release rate of not more than 50 ppb / h / cm 2 .

[0091] In addition, it is worth noting that the base of the anode electrode can also contain other elements in addition to Fe and Ni in mass percentage, because a certain amount of other elements will not significantly affect the formation of the passivation film and its corrosion resistance. For non-metallic elements such as P, S, C, Si, B, N, etc., the amount of addition is related to the solid solubility, wherein the content of P, S, B, N is usually less than 0.1%, otherwise it can affect the corrosion resistance of the material at the grain boundary; the content of C and Si is usually not more than 1%, which is helpful to form austenite. These non-metallic elements will not appear in the passivation film, and thus will not significantly affect the passivation film. For metal elements such as Ti, W, Al, V, Cu, Zr, Nb, etc., according to their solid solubility, the content is usually not more than 2%. For rare earth elements (REM) such as La, Ce, Y, Sc, etc., the content is usually less than 0.1%, and these metal elements can appear in the passivation film, but will not significantly affect the formation of the passivation film and its corrosion resistance. Therefore, according to the present application, in addition to Fe and Ni, the base of the anode electrode also contains one or more additional alloying elements in mass percentage, wherein the additional alloying elements can be selected from the group consisting of P≤0.1%, S≤0.1%, B≤0.1%, N≤0.1%, Si≤1%, C≤1%, Ti≤2%, W≤2%, Al≤2%, V≤2%, Cu≤2%, Zr≤2%, Nb≤2%, REM≤0.1% (for example, La≤0.1%, Ce≤0.1%, Y≤0.1%, Sc≤0.1%). Preferably, the total amount of additional alloying elements is not more than 2%, more preferably not more than 1%. The selection of other alloying elements will not affect the main components and structure of the passivation film, and thus will not affect the realization of the technical effects described in the present application.

[0092] Preferably, the base of the anode electrode contains 27%≤Ni≤42% in mass percentage, the balance being Fe, and unavoidable impurities, to obtain a total Fe+Ni ion release rate of not more than 65 ppb / h / cm 2 . More preferably, the base of the anode electrode contains 29%≤Ni≤38% in mass percentage, the balance being Fe, and unavoidable impurities, to obtain a total Fe+Ni ion release rate of not more than 55 ppb / h / cm 2 . Still more preferably, the base of the anode electrode contains 30%≤Ni≤36% in mass percentage, the balance being Fe, and unavoidable impurities, to obtain a total Fe+Ni ion release rate of not more than 50 ppb / h / cm 2 , achieving better acid and high potential corrosion resistance.

[0093] To confirm the specific components in the passivation film, the inventors of the present application performed XPS spectrum analysis on the passivation film of each sample obtained. FIG. 5 shows the XPS spectrum of the passivation film obtained at 1.0 V SHE , 1.6 V SHE , and 2.5 V SHE anodic polarization potential, respectively, according to the embodiment S5 of the present application. As shown in FIG. 5a and b, the Fe element is mainly in the III valence, thus Fe2O3, and the Ni element is mainly in the II valence, thus NiO. This also corresponds to the results of the aforementioned Equation 1 and Equation 2. As shown by the signal of the O1s electron orbit in FIG. 5c, the metallic oxides of Fe2O3 and NiO exist on the surface of the sample of the present application in the range of 1.0 V SHE to 2.5 V SHE anodic polarization potential, which indicates that the passivation behavior of the sample in this interval is continuous and reliable, which provides sufficient guarantee for the sample and the anode electrode made of the material of the sample to have corrosion resistance under high potential conditions.

[0094] According to the semi-quantitative analysis of XPS, the content of iron oxide and nickel oxide in the passivation film of S1-S10 is not less than 90% by mass. Ideally, if the substrate only contains Fe and Ni elements, the passivation film will only contain iron oxide and nickel oxide. However, in actual cases, the substrate contains unavoidable impurities and possibly a small amount of other alloy elements, so the passivation film may contain the participation of these elements. However, since the content of impurities and these other alloy elements is small, the content of iron oxide and nickel oxide in the passivation film is still not less than 90% by mass, which can achieve the technical effect of high potential and strong acid resistance.

[0095] In addition, the content of II valence Ni (NiO) in the passivation film obtained by semi-quantitative analysis of XPS is listed in Table 3. The inventors of the present application found that a complete NiO layer is an important condition for forming an effective passivation film on the samples S1-S10. Too low (so that the inner layer of NiO is incomplete) or too high (so that the outer layer of Fe2O3 is incomplete) NiO content will cause the corrosion resistance rate of the samples S1-S10 to rise. Specifically, through data analysis of the samples S1-S10, it is found that when the content of nickel oxide in the passivation film is not less than 30%, a very effective anti-corrosion effect can be achieved. However, when the content of nickel oxide in the passivation film is greater than 65%, the outer layer of iron oxide is not complete enough, which destroys the stability of the passivation film, resulting in an increase in ion dissolution rate. Therefore, the present application requires that the content of NiO in the passivation film is within 30-65% by mass, more preferably within the range of 35-42%. It is worth noting that the results calculated by XPS data are semi-quantitative analysis results, which should allow an error range of within 10%.

[0096] Figure 6 shows the sample S1 according to an embodiment of the present invention in perchloric acid solutions at 2.5V in (a) pH=2 and (b) pH=1. SHE The elemental distribution trend of the passivation film obtained after maintaining it at the anodic polarization potential for 24 hours is shown in Figure 5. The area indicated by the dashed line in the figure is the passivation film described in this application. Combined with the compositional analysis in Figure 5, it can be seen that the passivation films grown on the substrate of both samples S1 and S5 are mainly composed of nickel oxide and iron oxide. Specifically, NiO is basically continuously distributed and dominant in the portion of the passivation film immediately adjacent to the substrate, and Fe2O3 is basically continuously distributed and dominant in the outermost portion of the passivation film. It should be noted that the inner layer also contains Fe2O3, because the Fe2O3 in the outer layer needs to be formed through Fe atom diffusion during the formation of the passivation film, making it difficult to completely separate from the NiO layer.

[0097] The average thickness of the passivation film for each sample was measured: measurements were taken at at least three locations on the cross-section of each sample, and the average value was calculated. The results are listed in Table 3. For example, the passivation film thicknesses measured at multiple locations for S1 at pH 2 were 3 nm, 5 nm, and 4 nm, with an average thickness of ~4 nm. The passivation film thicknesses measured at multiple locations (not shown) for S1 at pH 1 were 9 nm, 10 nm, 12 nm, 8 nm, and 10 nm, with an average thickness of ~10 nm. Overall, the passivation film thickness according to the present invention is within the range of 3 to 12 nm, and the average thickness is within the range of 4 to 10 nm. Combined with the average ion dissolution rate in Table 2, it can be seen that the passivation film according to the present invention provides corrosion-resistant protection to the substrate of each sample.

[0098] Accordingly, the present invention provides a PEM electrolyzer employing an aqueous solution containing perchlorate, comprising:

[0099] Proton exchange membrane;

[0100] An anode electrode, which is the aforementioned anode electrode, serves as both an anode catalyst and a gas diffusion layer, wherein the anode electrode is configured to provide a flow channel for the aqueous solution within the electrolytic cell;

[0101] A cathode electrode, which cooperates with the anode electrode to sandwich the proton exchange membrane therebetween;

[0102] A bipolar plate, which is disposed opposite to and spaced apart from the anode and cathode electrodes respectively, provides a channel for the supply of aqueous solution and the discharge of products;

[0103] as well as

[0104] A reservoir for containing an aqueous solution containing perchlorate ions to immerse the combined structure of the proton exchange membrane, the anode electrode, and the cathode electrode and the surfaces of the bipolar plates opposite to the anode electrode and the cathode electrode, wherein the concentration of the perchlorate ions in the aqueous solution is 0.01 to 1 mol / L.

[0105] The anode electrode according to the present application realizes the functions of both an anode catalyst and a gas diffusion layer, thereby reducing the cost thereof. The bipolar plate functions to prevent the generated gas from passing through while providing a gas flow passage.

[0106] The present application also provides a method for producing hydrogen gas using a PEM electrolyzer, the method comprising:

[0107] connecting a power source to the cathode electrode and the anode electrode of the PEM electrolyzer, wherein a proton exchange membrane is interposed between the cathode electrode and the anode electrode, and the anode electrode is the aforementioned anode electrode according to the present application;

[0108] adding an aqueous solution containing 0.01 to 1 mol / L of perchlorate ions to the reservoir of the PEM electrolyzer; and

[0109] applying an anode polarization potential of 1.4 to 2.5 V SHE to the anode electrode to produce hydrogen gas.

[0110] Preferably, the concentration of the perchlorate ions is 0.01 to 0.1 mol / L. Preferably, the anode polarization potential is 1.6 to 2.2 V SHE .

[0111] Further, the present application provides a steel sheet comprising a base and a passivation film on at least one surface of the base, wherein the base comprises, in mass percent: 22%≤Ni<80%, 95%≤Ni+Fe, and unavoidable impurities, and wherein the passivation film comprises nickel oxide and iron oxide, both of which account for at least 90% of the passivation film in mass percent.

[0112] Preferably, the average thickness of the passivation film is in the range of 3 to 12 nm, and the proportion of nickel oxide in the passivation film is in the range of 30% to 65%.

[0113] Preferably, before the passivation film is generated on the base of the steel sheet, the base is heated to 1000 to 1300°C in a vacuum environment or a protective atmosphere for 6 to 20 hours for homogenization treatment, so as to avoid the presence of local inhomogeneity in the steel sheet, which will cause a galvanic cell reaction in subsequent use, leading to local corrosion and affecting the formation of the passivation film.

[0114] Preferably, the base of the steel sheet contains Ni in an amount of 27%≤Ni≤42% in mass, more preferably 29%≤Ni≤38%, and even more preferably 30%≤Ni≤36%, in order to have a better corrosion resistance during the use of the PEM electrolyser.

[0115] In some embodiments, the base of the steel sheet further contains one or more additional alloying elements. The one or more additional alloying elements are not more than 2% in mass, selected from the group consisting of P≤0.1%, S≤0.1%, B≤0.1%, N≤0.1%, Si≤1%, C≤1%, Ti≤2%, W≤2%, Al≤2%, V≤2%, Cu≤2%, Zr≤2%, Nb≤2%, and rare earth elements≤0.1%.

[0116] Preferably, the base of the steel sheet contains, in addition to Ni, all Fe and unavoidable impurities in mass, in order to improve the protection effect of the passivation film compared to passivation films containing other impurities.

[0117] The steel sheet can be used to manufacture an anode electrode for a PEM electrolyser using an aqueous solution containing perchlorate, thereby achieving its use in a PEM electrolyser. It will be understood that, as mentioned above, the passivation film can form spontaneously during the use of the anode electrode in the PEM electrolyser, so it is also possible to consider directly using the base of the steel sheet described above to make the anode electrode, as shown in the embodiments.

[0118] The above embodiments and experimental data are intended to illustrate the present application, and it should be clear to those skilled in the art that the present application is not limited to these embodiments, and various modifications can be made without departing from the scope of the present application.

Claims

1. An anode electrode for a PEM electrolyser employing an aqueous solution containing a perchlorate anion, wherein, The base of the anode electrode contains, in mass percentage, 22%≤Ni<80%, 95%≤Ni+Fe, and inevitable impurities, and the aqueous solution contains perchlorate at a concentration of 0.01 mol / L to 1 mol / L, wherein the anode electrode is configured such that at least one surface of the substrate of the anode electrode is exposed to the aqueous solution during use of the PEM electrolyzer such that a corrosion-resistant passive film including nickel oxide and iron oxide, both in a mass percentage of at least 90% of the passive film, is formed on the at least one surface when an anodic polarization potential of 1.4 to 2.5 V is applied to the anode electrode SHE .

2. The anode electrode of claim 1, wherein, The base of the anode electrode contains, in mass percentage, 27%≤Ni≤42%.

3. The anode electrode of claim 1, wherein, The base of the anode electrode contains, in mass percentage, 29%≤Ni≤38%.

4. The anode electrode of claim 1, wherein, The base of the anode electrode contains, in mass percentage, 30%≤Ni≤36%.

5. The anode electrode according to any one of claims 1 to 4, wherein, The base of the anode electrode further contains one or more additional alloying elements.

6. The anode electrode of claim 5, wherein, The one or more additional alloying elements are not more than 2% in mass percentage, and are selected from the group consisting of P≤0.1%, S≤0.1%, B≤0.1%, N≤0.1%, Si≤1%, C≤1%, Ti≤2%, W≤2%, Al≤2%, V≤2%, Cu≤2%, Zr≤2%, Nb≤2%, and rare earth elements≤0.1%.

7. The anode electrode according to any one of claims 1 to 4, wherein The base contains, in mass percentage, all of Fe and inevitable impurities other than Ni.

8. A PEM electrolyzer using an aqueous solution containing perchlorate, comprising: a proton exchange membrane; an anode electrode, which is the anode electrode according to any one of the preceding claims 1 to 7, which functions as both an anode catalyst and a gas diffusion layer, wherein the anode electrode is configured to provide a flow path for the aqueous solution in the electrolyzer; a cathode electrode, which cooperates with the anode electrode to sandwich the proton exchange membrane therebetween; bipolar plates, which are disposed opposite to and spaced apart from the anode electrode and the cathode electrode, respectively, and which provide a path for the supply of the aqueous solution and the discharge of products; a reservoir for containing the aqueous solution containing perchlorate to immerse the combined structure of the proton exchange membrane, the anode electrode, and the cathode electrode, and the surfaces of the bipolar plates opposite to the anode electrode and the cathode electrode, respectively, wherein the concentration of perchlorate in the aqueous solution is 0.01 to 1 mol / L.

9. A method of generating hydrogen gas using a PEM electrolyzer, the method comprising: connecting a power source to a cathode electrode and an anode electrode of a PEM electrolyzer, wherein a proton exchange membrane is sandwiched between the cathode electrode and the anode electrode, and the anode electrode is the anode electrode according to any one of the preceding claims 1 to 7; adding an aqueous solution containing perchlorate at a concentration of 0.01 to 1 mol / L in a reservoir of the PEM electrolyzer; and The base contains, in mass percentage, 22%≤Ni<80%, 95%≤Ni+Fe, and inevitable impurities, and the passivation film contains nickel oxide and iron oxide, both of which account for at least 90% of the passivation film in mass percentage. applying an anodic polarization potential of 1.4 to 2.5 V SHE to the anode electrode to produce oxygen gas, while simultaneously producing hydrogen gas at the cathode electrode.

10. The method of claim 9, wherein, The concentration of the perchlorate is 0.01-0.1 mol / L, and the anode polarization potential is 1.6-2.2 V SHE .

11. A steel sheet comprising a base body and a passivation film on at least one surface of the base body, wherein, The thickness of the passivation film is in the range of 3 to 12 nm, and the content of nickel oxide in the passivation film is 30 to 65% in mass percentage.

12. The steel sheet according to claim 11, wherein, The base contains, in mass percentage, 29%≤Ni≤38%.

13. The steel sheet according to claim 11, wherein, The base contains, in mass percentage, 29%≤Ni≤38%.

14. The steel sheet according to claim 11, wherein said matrix comprising, in mass percentage: 30%≤ Ni ≤ 36%.

15. The steel sheet according to any one of claims 11 to 14, wherein, said matrix, in mass percentage, comprising, in addition to Ni, all of Fe and unavoidable impurities.

16. The steel sheet according to any one of claims 11 to 14, wherein, said matrix further comprising one or more additional alloying elements.

17. The steel sheet according to claim 16, wherein said one or more additional alloying elements, in mass percentage, not being greater than 2% and being selected from the group consisting of: P ≤ 0.1%, S ≤ 0.1%, B ≤ 0.1%, N ≤ 0.1%, Si ≤ 1%, C ≤ 1%, Ti ≤ 2%, W ≤ 2%, Al ≤ 2%, V ≤ 2%, Cu ≤ 2%, Zr ≤ 2%, Nb ≤ 2%, rare earth elements ≤ 0.1%.

18. Use of the steel sheet according to anyone of claims 11 to 17 in a PEM electrolyser employing an aqueous solution containing perchlorate, wherein, said steel sheet being used as an anode electrode for manufacturing said PEM electrolyzer, said aqueous solution containing perchlorate at a concentration of 0.01 mol / L to 1 mol / L.

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