Self-supporting electrode for hydrogen production by electrolysis of water and method for its preparation and use

Abstract

The application belongs to the field of electrolysis of water, and particularly relates to a self-supporting electrode for hydrogen production by electrolysis of water and a preparation method and application thereof, wherein the preparation method of the self-supporting electrode for hydrogen production by electrolysis of water comprises the following steps: hydrothermal treatment of a titanium substrate in an alkali solution, and then calcination treatment in an oxygen-containing gas at a temperature T1 to form a titanium dioxide array in situ on the surface of the titanium; the temperature T1 is 300-700 DEG C; a first Ir solution is added to the titanium dioxide array, and then first-stage heat treatment is carried out in a hydrogen-containing atmosphere at a temperature T2 to obtain a first-stage modified array; a second Ir solution is added to the first-stage modified array, and then second-stage heat treatment is carried out in an oxygen-containing atmosphere at a temperature T3 to obtain the self-supporting electrode for hydrogen production by electrolysis of water. The method can obtain excellent activity and stability at a low Ir loading.

Description

Technical Field

[0001] This invention belongs to the field of energy-saving hydrogen production through water electrolysis, specifically relating to the field of electrodes for water electrolysis. Background Technology

[0002] Iridium, a precious metal, is frequently used as a catalyst in the oxygen evolution reaction (OER) of acidic water electrolysis; however, its high cost remains a major challenge. Developing novel catalysts and optimizing catalyst layer structures are two approaches to address this issue and improve iridium utilization. Employing support materials is a practical strategy, as it reduces particle agglomeration and provides additional thickness to the catalyst layer, thereby enhancing its stability. Titanium dioxide, exhibiting electrochemical stability at high voltages, is considered a promising support for OER catalysts.

[0003] Existing technologies have also reported some schemes for modifying or loading noble metals using titanium dioxide as a carrier. For example, patent document CN110327920A discloses a single-atom catalyst and its preparation method and application. The preparation method includes the following steps: S1: reducing titanium dioxide nanomaterials to obtain defective titanium dioxide nanomaterials; S2: adding the defective titanium dioxide nanomaterials and ammonium carbonate to a solution containing a noble metal source until the pH is 8-10, reacting, and separating to obtain the precursor; the molar ratio of the noble metal to the titanium dioxide nanomaterials in the noble metal source is 1:480-520; S3: calcining the precursor at 100-400 °C for 2-4 h to obtain the single-atom catalyst.

[0004] The patent document with publication number CN104269274A discloses a method for preparing a titanium / titanium dioxide microcone-nanowire electrode. The method includes: (1) electrochemically anolyzing a titanium substrate and then calcining it to obtain a titanium / titanium dioxide microcone electrode; (2) hydrothermally treating the titanium / titanium dioxide microcone electrode obtained in step (1) in an alkaline solution, then treating it with an acid solution, and then calcining it.

[0005] With low iridium loading, activity loss occurs. Simultaneously, titanium oxidizes in air, forming a thin, dense titanium dioxide passivation film. This film has extremely poor conductivity, severely hindering electron transport. Furthermore, if the catalyst is directly loaded onto a smooth metal surface, it is easily detached during vigorous bubble formation. Moreover, under acidic conditions, the OER of iridium-based catalysts further increases the risk of active component detachment.

[0006] In summary, the existing iridium-based catalysts still exhibit unsatisfactory OER catalytic activity and stability under low loading and acidic conditions. The industry needs to implement multi-level structural design and synergistic modification schemes for the substrate to achieve high catalytic activity with low loading. Summary of the Invention

[0007] To address the problem that the OER catalytic activity and stability of existing iridium-based catalysts under acidic conditions are not ideal, the primary objective of this invention is to provide a method for preparing a self-supporting electrode for hydrogen production by water electrolysis, aiming to obtain a self-supporting electrode for hydrogen production by water electrolysis with low Ir loading and excellent hydrogen production activity and interfacial stability under acidic conditions.

[0008] The second objective of this invention is to provide a self-supporting electrode for hydrogen production by water electrolysis prepared by the aforementioned method and its application in hydrogen production by water electrolysis.

[0009] Existing precious metal-loaded water electrolysis hydrogen production electrodes mostly require high precious metal loading to achieve good hydrogen production activity, which increases the preparation cost. Furthermore, the loading stability between existing precious metals and the substrate is not ideal, and they are prone to detachment during water electrolysis, resulting in unsatisfactory hydrogen production stability. To address this problem, this invention, after in-depth research, provides the following improvement:

[0010] A method for preparing a self-supporting electrode for hydrogen production by water electrolysis, comprising the following steps:

[0011] Step 1:

[0012] The titanium substrate is hydrothermally treated in an alkaline solution, followed by calcination at a temperature T1 containing oxygen gas to form a titanium dioxide array in situ on the titanium surface; the temperature T1 is 300~700 ℃.

[0013] Step 2:

[0014] A first Ir solution was added to the titanium dioxide array, followed by a first heat treatment at a temperature T2 in a hydrogen atmosphere to obtain a modified array.

[0015] A second Ir solution was added to a modified array, followed by a second heat treatment at a temperature of T3 in an oxygen-containing atmosphere to obtain a self-supporting electrode for hydrogen production by water electrolysis.

[0016] The Ir concentration in the first Ir solution is 0.01~0.4 mol / L, and the Ir concentration in the second Ir solution is 4~15 times that of the first Ir solution; the Ir added to the first Ir solution accounts for 5%~20% of the total Ir weight.

[0017] Temperatures T2 and T3 are 300~700 ℃.

[0018] This invention innovatively forms a titanium dioxide array in situ on a titanium substrate beforehand, then pre-combines it with a low-concentration first Ir solution and performs a first-stage calcination treatment in a hydrogen-containing atmosphere, followed by combination with a high-concentration gradient second Ir solution and treatment in an oxygen-containing atmosphere. This synergistic effect of the two-stage Ir concentration gradient combination and the two-stage gas exchange calcination treatment (hydrogen followed by oxygen) induces stable Ir loading and improves activity exposure characteristics. Thus, excellent hydrogen production activity can be obtained with a relatively low Ir loading. Furthermore, it effectively improves the Ir combination stability and catalytic stability.

[0019] In this invention, the titanium substrate is a metallic titanium substrate, preferably titanium felt, titanium foam, titanium sheet or titanium mesh;

[0020] Preferably, the solute in the alkaline solution includes at least one of potassium hydroxide and sodium hydroxide;

[0021] Preferably, the concentration of the solute in the alkaline solution is 0.1~5 mol / L; further, it can be 0.5~4 mol / L; even further, it can be 0.8~1.2 mol / L.

[0022] Preferably, the temperature of the hydrothermal reaction is 110~250 ℃, and more preferably 120~200 ℃;

[0023] Preferably, the hydrothermal reaction time is 1 to 25 hours; more preferably, it can be 2 to 20 hours.

[0024] Preferably, the oxygen-containing gas is air;

[0025] Preferably, the temperature T1 is 400~550 ℃.

[0026] Preferably, the heat preservation time at temperature T1 is 0.5~10 h, and more preferably 1~5 h.

[0027] In this invention, a relatively dilute first Ir solution is pre-calcined in a hydrogen-containing atmosphere. This helps to stabilize the active sites embedded in the titanium dioxide array in advance, which in turn facilitates the subsequent induced deposition of Ir and the construction of a highly stable fusion interface, improves the exposure of active sites, and improves catalytic activity and catalytic stability.

[0028] In this invention, the first Ir solution is added to the titanium dioxide array by drop coating.

[0029] Preferably, the titanium dioxide array is preheated to 100~200 °C, and then the first Ir solution is drop-coated while it is still hot.

[0030] Studies have shown that the preferred scheme can further optimize the gradient structure, which is expected to further improve the activity and stability of its OER.

[0031] The solute in the first Ir solution includes at least one of iridium chloroacetic acid, iridium acetate, and iridium chloride, wherein the Ir concentration is 0.01~0.1 mol / L; more specifically, it can be 0.01~0.05 mol / L.

[0032] The weight ratio of titanium substrate to Ir in the first Ir solution is 8000~12000:1; further, it can be 9000~11000:1.

[0033] Furthermore, the Ir added to the first Ir solution accounts for 8% to 15% of the total Ir weight.

[0034] In this invention, the volume fraction of hydrogen in the hydrogen-containing atmosphere is 1% to 20%; more specifically, it can be 5% to 15%.

[0035] Preferably, the temperature T2 is 500~650 ℃; more preferably, it can be 550~600 ℃.

[0036] Preferably, the heat preservation time at temperature T2 is 1~10 h; more preferably, it can be 1~5 h.

[0037] In this invention, the second Ir solution is added to a modified array by drop-coating;

[0038] In this invention, an innovative two-stage composite method with increasing Ir concentration is adopted, which, together with the aforementioned gas-switching roasting mechanism, helps to improve the loading interface structure of Ir and improve its loading stability. In addition, it also helps to improve the high-quality exposure of its active sites, thereby improving its hydrogen production activity and stability.

[0039] The solute in the second Ir solution includes at least one of chloroiridium acid, iridium acetate, and iridium chloride, wherein the Ir concentration is 5 to 10 times that in the first Ir solution.

[0040] In this invention, the total weight of Ir element in the first Ir solution and the second Ir solution is 0.05% to 0.15% of the total weight of titanium element; more specifically, it can be 0.07% to 0.12%.

[0041] In this invention, the oxygen volume fraction in the oxygen-containing atmosphere is 5% to 30%, and considering cost, it can be further used as air;

[0042] Preferably, the temperature T3 is 300~500 ℃; more preferably, it can be 350~450 ℃.

[0043] Preferably, the heat preservation time at temperature T3 is 1~6 h, and more preferably 2~4 h;

[0044] In this invention, the Ir loading in the self-supporting electrode can be as low as 0.1~0.15 mg / cm³. 2 .

[0045] The present invention also provides a self-supporting electrode for hydrogen production by water electrolysis prepared by the above preparation method.

[0046] In this invention, the preparation method can endow the prepared material with special physicochemical properties, and the electrode prepared by the method can obtain excellent hydrogen production activity even with low Ir loading, while also taking into account excellent stability.

[0047] The present invention also provides an application of the self-supporting electrode for hydrogen production by water electrolysis prepared by the above preparation method, which is used as an electrode for hydrogen production by water electrolysis.

[0048] Beneficial effects

[0049] This invention innovatively forms a titanium dioxide array in situ on a titanium substrate beforehand, and then induces stable loading of Ir and high interfacial stability of Ir by combining two-stage calcination treatment with two-stage gradient Ir concentrations, followed by hydrogen and then oxygen. This allows for excellent hydrogen production activity with a relatively low Ir loading. In addition, it can effectively improve the Ir recombination stability and catalytic stability.

[0050] The electrode described in this invention can have an Ir loading as low as 0.1 mg / cm³. 2 In addition, it also exhibits excellent hydrogen production activity and catalytic stability.

[0051] The catalyst provided by this invention exhibits particularly outstanding catalytic activity in the oxygen evolution reaction at high current densities, which can meet the performance requirements of actual industrial production. Attached Figure Description

[0052] Figure 1 This is an SEM image of the surface of the titanium metal felt substrate obtained in step (1) of Example 1;

[0053] Figure 2 This is an SEM image of the surface of the titanium metal felt substrate obtained in step (2) of Example 1;

[0054] Figure 3 This is an SEM image of the surface of the titanium felt electrode obtained in step (3) of Example 1;

[0055] Figure 4 The above are SEM-EDS images of the surface of the titanium felt electrode obtained in step (3) of Example 1, where (a) is an SEM morphology image, (b) is an O element distribution image, (c) is a Ti element distribution image, and (d) is an Ir element surface distribution image.

[0056] Figure 5 The images are TEM-EDS images of the titanium felt electrode obtained in step (3) of Example 1, where (a) is a TEM morphology image, (b) is an elemental surface distribution image of O, (c) is an elemental surface distribution image of Ti, and (d) is an elemental surface distribution image of Ir.

[0057] Figure 6 The titanium felt electrode (IrO) obtained in step (3) of Example 1 x @TiO x Comparative Example 2 (IrO2@TiO) x The test diagrams for the working electrode are shown below, where (a) is the polarization curve, (b) is the Tafel slope, (c) is the cyclic voltammogram of Comparative Example 2, and (d) is the cyclic voltammogram of Example 1.

[0058] Figure 7 The titanium felt electrode obtained in step (3) of Example 1 is subjected to a temperature of 100 mA cm⁻¹. -2 The voltage versus time curve during the oxygen evolution reaction at a current density;

[0059] Figure 8 The titanium felt electrode (IrO) obtained in step (3) of Example 1 x @TiO x Comparative Example 2 (IrO2@TiO) x The electron paramagnetic resonance spectrum of ).

[0060] Figure 9 The following are polarization curves for each embodiment and comparative example. Detailed Implementation

[0061] The present invention will be further described below with reference to specific implementation examples. The following embodiments do not limit the scope of the present invention; any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0062] Electrochemical performance tests were conducted on either a Gamry Reference 600 or Gamry Interface 1010E electrochemical workstation equipped with a standard three-electrode system. The tests used a three-electrode electrolytic cell with a self-supported catalyst (geometric surface area of ​​1 cm²). 2 A platinum sheet electrode was used as the working electrode, and a mercury-mercurous sulfate electrode was used as the reference electrode. The main electrochemical performance tests were conducted at 25°C in a 0.5 mol / L sulfuric acid electrolyte solution. The LSV curve scan rate was set to 5 mV·s. -1 Automatic iR compensation was employed. In the CV test, 20 mV·s⁻¹ was used. -1The scanning rate was set, and the reaction was performed in the oxygen evolution reaction zone for 1000 cycles. The stability of the catalyst was determined by comparing the potential changes before and after the cycles. In the constant current test, a constant current was applied to the catalyst, and the voltage change curve over time was recorded.

[0063] Example 1

[0064] Step (1): Using titanium felt as a substrate, it was immersed in a 1 mol / L potassium hydroxide solution, then placed in an oven at 200 ℃ (hydrothermal temperature) for 2 h, and subsequently calcined in a muffle furnace (air atmosphere) at 500 ℃ (calcination temperature) for 2 h to form a titanium dioxide array on the surface of the titanium substrate. The SEM image of this array is shown below. Figure 1 ;

[0065] Step (2): The titanium felt treated in step (1) was drop-coated with an iridium acetate solution (0.01 mol / L; the weight ratio of metallic titanium felt to Ir was 10000:1) onto the surface of a hot titanium felt (temperature 150±20 ℃) ​​(the surface with the titanium dioxide array), and then placed in a tube furnace and kept at 600 ℃ in an argon / hydrogen atmosphere (hydrogen gas fraction of 10%) for 2 h; the morphology of the surface of the treated titanium felt is shown in the figure. Figure 2 ;

[0066] Step (3): Drop-coat the surface of the titanium felt obtained in step (2) (the surface with Ir composite in step (2)) with a 0.1 mol / L iridium acetate solution; the weight ratio of metallic titanium felt to Ir is 1000:1, and then place it in a muffle furnace (air atmosphere) at 350 ℃ for 2 h to obtain a metallic titanium felt electrode (IrO). x @TiO x The Ir loading was 0.13 mg / cm³. 2 The morphology and elemental distribution of the obtained titanium felt electrode surface are shown in the figures below. Figure 3 , Figure 4 , Figure 5 As shown.

[0067] The titanium felt substrate (IrO) obtained in step (3) x @TiO x ) was directly used as the working electrode, and its oxygen evolution reaction performance was tested respectively. Figure 6 ) and long-term stable performance ( Figure 7 ).

[0068] contrast Figure 1 , Figure 2 , Figure 3It can be observed that the titanium surface is corroded under high temperature and high pressure alkaline environment, forming a rough micro-nano array structure, which greatly increases its specific surface area. This provides more anchoring sites for subsequent loading of catalytically active materials. Furthermore, the gradient Ir composite and two-stage gas-changing treatment further improve the orderliness and stabilize the microstructure. Figure 4 , Figure 5 It can be observed that the iridium nanoparticles were successfully and uniformly dispersed on the support. From Figure 6 , Figure 7 It can be observed that the titanium felt-supported iridium oxide catalyst obtained in Example 1 exhibits excellent catalytic activity for the oxygen evolution reaction, requiring only 197 mV and 269 mV to reach 10 mA cm⁻¹, respectively. -2 and 100 mA cm -2 The current density, IrO with a specific structure x @TiO x The catalyst exhibits superior current output in the high potential range, indicating stronger intrinsic catalytic activity. Comparing the CV curves after the first and 1000th cycles, the current density shows only a slight decrease after 1000 cycles, demonstrating the catalyst's excellent electrochemical durability. Simultaneously, it can achieve current output at 100 mA cm⁻¹. -2 The oxygen evolution reaction was stably catalyzed at a current density for over 500 h. Figure 8 It can be observed that a characteristic absorption peak appears in the magnetic field range of approximately 3510-3520 G, among which IrO x The signal peak intensity of @TiO2 is significantly higher than that of IrO2@TiO x , indicating that IrO x @TiO2 contains more paramagnetic oxygen vacancy sites; these oxygen vacancies can usually serve as active sites for OER, and the difference in their concentration reflects the difference between the two catalysts in terms of surface electronic structure and the number of catalytic active sites.

[0069] Example 2

[0070] Compared with Example 1, the only difference is that in step (1), the hydrothermal temperature is 120 ℃, the time is 4 h, the calcination temperature is 450 ℃, and the holding time for calcination is 3 h. All other operations and parameters are the same as in Example 1.

[0071] Example 3

[0072] Compared with Example 1, the only difference is that in step (1): a titanium sheet is used as the substrate, which is immersed in a 4 mol / L potassium hydroxide solution and then placed in an oven at 200 °C for 20 h; and then placed in a muffle furnace at 500 °C (air atmosphere) for 4 h.

[0073] Step (2): After the titanium sheet (titanium dioxide array surface) was treated in step (1), a chloroiridium acid solution (0.02M; the weight ratio of metallic titanium sheet and Ir is 10500:1) was dropped onto it, and then it was placed in a tube furnace and kept at 550 °C in an argon / hydrogen atmosphere (where the hydrogen gas integral is 15%) for 2 h.

[0074] Step (3): Drop-coat the surface of the titanium substrate (titanium dioxide array surface) obtained in step (2) with a 0.15 mol / L chloroiridium acid solution, with a weight ratio of titanium metal felt to Ir of 1500:1; then place it in a muffle furnace (air atmosphere) at 450 ℃ and keep it warm for 4 h.

[0075] The titanium substrate obtained in step (3) was used directly as the working electrode to test its oxygen evolution reaction performance.

[0076] Example 4

[0077] Compared with Example 1, the only difference is that in step 2, the titanium felt treated in step 1 is not preheated and kept warm. That is, it is dropped onto the iridium acetate solution at room temperature and then placed in a tube furnace for treatment. All other operations and parameters are the same as in Example 1.

[0078] Comparative Example 1

[0079] Compared with Example 1, the only difference is that in step 1, 1M sulfuric acid is used instead of the 1M potassium hydroxide solution, and all other operations and parameters are the same as in Example 1.

[0080] Comparative Example 2

[0081] Compared with Example 1, the only difference is that in step 2, the iridium acetate solution was not dropped on, but the iridium acetate solution in this step and the iridium acetate solution in step 3 were mixed and added together. That is, the total Ir added and other operating conditions are the same as in Example 1, and a titanium metal felt electrode (IrO2@TiOx) is obtained.

[0082] Comparative Example 3

[0083] Compared with Example 1, the only difference is that in step 2, the argon / hydrogen atmosphere is replaced with Ar gas, and all other operations and parameters are the same as in Example 1.

[0084] Comparative Example 4

[0085] Compared with Example 1, the only difference is that the iridium acetate solution used in steps 2 and 3 is replaced. That is, in step 2, the high concentration (0.1M) iridium acetate solution of the original step 3 is used; in step 3, the low concentration (0.01M) iridium acetate solution of the original step 2 is used. All other operations and parameters are the same as in Example 1.

[0086] The test results for each embodiment and comparative example are shown in Table 1:

[0087]

[0088] As can be seen from the examples and comparative examples in Table 1, pre-forming a titanium dioxide array in situ on a titanium substrate, followed by a two-stage calcination treatment based on two gradient Ir concentrations (hydrogen followed by oxygen), can induce stable Ir loading and high interfacial stability recombination, effectively improving Ir recombination stability and catalytic stability.

[0089] Furthermore, as demonstrated in Examples 1 and 4, preheating the array and then applying the first Ir solution while it is still hot can further strengthen the structure and improve the OER performance of the material.

Claims

1. A method for preparing a self-supporting electrode for hydrogen production by water electrolysis, characterized in that the steps include... include: Step 1: The titanium substrate is hydrothermally treated in an alkaline solution, followed by calcination at a temperature T1 containing oxygen gas to form a titanium dioxide array in situ on the titanium surface; the temperature T1 is 300~700 ℃. Step 2: A first Ir solution was added to the titanium dioxide array, followed by a first heat treatment at a temperature T2 in a hydrogen atmosphere to obtain a modified array. A second Ir solution was added to a modified array, followed by a second heat treatment at a temperature of T3 in an oxygen-containing atmosphere to obtain a self-supporting electrode for hydrogen production by water electrolysis. The Ir concentration in the first Ir solution is 0.01~0.4 mol / L, and the Ir concentration in the second Ir solution is 4~15 times that of the first Ir solution; the Ir added to the first Ir solution accounts for 5%~20% of the total Ir weight. Temperatures T2 and T3 are 300~700 ℃.

2. The method for preparing the self-supporting electrode for hydrogen production by water electrolysis as described in claim 1, characterized in that, The titanium substrate can be titanium felt, titanium foam, titanium sheet, or titanium mesh; The solute in the alkaline solution includes at least one of potassium hydroxide and sodium hydroxide; The concentration of the solute in the alkaline solution is 0.1~5 mol / L; The hydrothermal reaction temperature is 110~250 ℃; The hydrothermal reaction time is 1~25 h; The oxygen-containing gas is air; The heat preservation time at temperature T1 is 0.5~10 h.

3. The method for preparing the self-supporting electrode for hydrogen production by water electrolysis as described in claim 1, characterized in that, The first Ir solution was added to the titanium dioxide array by drop-coating; The solute in the first Ir solution includes at least one of iridium chloroacetic acid, iridium acetate, and iridium chloride, wherein the Ir concentration is 0.01~0.1 mol / L; The weight ratio of titanium substrate to Ir in the first Ir solution is 8000~12000:

1.

4. The method for preparing the self-supporting electrode for hydrogen production by water electrolysis as described in claim 1, characterized in that, The volume fraction of hydrogen in a hydrogen-containing atmosphere is 1% to 20%. The heat preservation time at temperature T2 is 1~10 h.

5. The method for preparing a self-supporting electrode for hydrogen production by water electrolysis as described in any one of claims 1 to 4, characterized in that, The titanium dioxide array is preheated to 100~200 °C, and then the first Ir solution is drop-coated while it is still hot.

6. The method for preparing the self-supporting electrode for hydrogen production by water electrolysis as described in claim 1, characterized in that, The second Ir solution was added to a modified array by drop-coating. The solute in the second Ir solution includes at least one of chloroiridium acid, iridium acetate, and iridium chloride, wherein the Ir concentration is 5 to 10 times that in the first Ir solution.

7. The method for preparing a self-supporting electrode for hydrogen production by water electrolysis as described in claim 1, characterized in that, The total Ir element weight is 0.05% to 0.15% of the total titanium element weight.

8. The method for preparing a self-supporting electrode for hydrogen production by water electrolysis as described in claim 1, characterized in that, The oxygen volume fraction in an oxygen-containing atmosphere is 5% to 30%. The heat preservation time at temperature T3 is 1~6 h.

9. A self-supporting electrode for hydrogen production by water electrolysis, prepared by the method according to any one of claims 1 to 8.

10. The application of a self-supporting electrode for hydrogen production by water electrolysis prepared by the method according to any one of claims 1 to 8, characterized in that, It is used as an electrode for the electrolysis of water to produce hydrogen.

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