Low-noble metal long-life dsa anode and preparation method thereof

Abstract

The application discloses a low-noble metal long-service-life DSA anode and a preparation method thereof, and belongs to the technical field of electrochemical catalytic electrode materials. The DSA anode comprises a titanium base and a composite coating formed on the surface of the titanium base, and the composite coating comprises an intermediate layer coating and an active layer coating. The intermediate layer coating is a composite oxide coating containing Ir oxide, Sn oxide and Sb oxide, and the active layer coating is a composite oxide coating containing Ru oxide, Sn oxide and Sb oxide. The loading of noble metal Ir is 0.21-0.30 g / m 2 , and the loading of noble metal Ru is 0.32 g / m 2 . Through the design of the above-mentioned composite coating structure, the electrode can significantly improve the stability and service life of the electrode under the condition of oxygen evolution while maintaining high oxygen evolution catalytic activity, wherein the highest accelerated service life of the electrode calculated according to unit loading can reach 712.46 h·m 2 / g, and the electrode is helpful to reduce the cell voltage, reduce the electrolysis energy consumption and operation cost. In addition, the structure can also improve the utilization efficiency of noble metal and reduce the preparation cost of the electrode.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalysis, specifically relating to a low-precious-metal long-life DSA anode and its preparation method, which can be used in electrochemical water treatment, electrochemical water softening and other electrochemical processes mainly involving oxygen evolution reactions. Background Technology

[0002] Electrochemical water softening technology is a method for removing scale-forming ions such as calcium and magnesium from water through electrolysis. Due to its environmental friendliness and ease of operation, this technology shows application potential in fields such as industrial circulating cooling water treatment. In the core device of this technology, the electrolytic cell, the main electrochemical reaction occurring at the anode is the oxygen evolution reaction (OER). This means that the anode is constantly subjected to a high potential, a strong OER environment, and continuous oxidative attack from reactive oxygen species (such as ·OH), placing extremely stringent requirements on the electrochemical stability and structural durability of the anode coating. Against this backdrop, RuO2 and IrO2, as noble metal oxides, have become the main candidate coating materials due to their excellent OER catalytic activity and stability. RuO2 exhibits good OER catalytic activity, but its electrochemical stability is relatively poor when used alone. In contrast, IrO2 has better electrochemical stability and lifespan advantages, but its cost is higher. The design of the anode material not only needs to consider OER catalytic activity and electrochemical stability but also the amount of noble metal used and manufacturing costs. To more intuitively reflect the lifetime performance corresponding to a unit of precious metal input in different electrodes, a rough evaluation is performed by converting the accelerated lifetime based on the unit equivalent Ir loading. Specifically, the loading of other precious metals (such as Ru, Ta, etc.) in the electrode is converted into an equivalent Ir loading according to their price, and then combined with the actual Ir loading for calculation. This is then used as the unit loading for lifetime conversion. Following this method, CN119859799A discloses a method for preparing a Ti / IrO2-RuO2-SnO2 electrode. This method uses a sol-gel method to improve the surface morphology and electrocatalytic activity of the anode, achieving an accelerated lifetime of approximately 15.85 h·m. 2 CN107829109A discloses a titanium-based iridium dioxide coated electrode and its preparation method. This method employs an intermediate layer strategy to improve the electrode's lifespan, achieving an accelerated lifespan of approximately 111.09 h·m. 2 CN120945431A discloses a Ti / IrO2-SnO2-SbO2 anode. This method uses a gradient brush coating process to improve the thermal stress of the coating, and its accelerated lifetime is approximately 115.00 h·m. 2 / g.

[0003] However, in existing technologies, to extend the service life of DSA anodes, the content of noble metal components (such as Ir and Ru) in the coating is typically increased. While this method can improve electrode stability and lifespan, it also leads to problems such as increased noble metal consumption, higher manufacturing costs, and insufficient noble metal utilization efficiency. Therefore, developing a DSA anode with a longer service life under lower noble metal cost pressures has significant practical application value. Summary of the Invention

[0004] This invention aims to provide a long-life DSA anode with low-precious metal content and its preparation method. By constructing a composite coating structure consisting of an Ir oxide-containing intermediate layer and a Ru oxide-containing active layer, the synergistic effect of the intermediate and active layers is utilized to improve the electrode's stability and lifespan under oxygen evolution conditions while maintaining good oxygen evolution electrocatalytic performance, and to enhance the utilization efficiency of precious metals. To achieve the above objectives, this invention adopts the following technical solution: A low-noble-metal, long-life DSA anode, characterized in that it comprises a titanium substrate and a composite coating formed on the surface of the titanium substrate, wherein the composite coating comprises, from the inside out, an intermediate layer coating and an active layer coating; the intermediate layer coating is a composite oxide coating comprising Ir oxide, Sn oxide and Sb oxide, wherein, based on the total molar amount of the three metal elements Ir, Sn and Sb, the molar percentage of Ir is 7%-10%, the sum of the molar percentages of Sn and Sb is 90%-93%, and the molar ratio of Sn to Sb is 6:1-8:1, and the Ir loading is 0.21-0.30 g / m³. 2 The active layer coating is a composite oxide coating comprising Ru oxide, Sn oxide, and Sb oxide. Specifically, based on the total molar amount of the three metal elements Ru, Sn, and Sb, the molar percentage of Ru is 4%-10%, the sum of the molar percentages of Sn and Sb is 90%-96%, the molar ratio of Sn to Sb is 6:1-8:1, and the Ru loading is 0.13-0.32 g / m³. 2 .

[0005] The thicknesses of the intermediate layer coating and the active layer coating are 5-15 µm and 15-45 µm, respectively.

[0006] The preparation method of the above-mentioned low-noble-metal long-life DSA anode includes the following steps: 1) Pretreatment of the titanium matrix; 2) Prepare alcoholic solutions of chloroiridic acid, tin tetrachloride and antimony trichloride respectively. Mix the three solutions and add concentrated hydrochloric acid to obtain the intermediate layer precursor solution. 3) Prepare alcoholic solutions of ruthenium trichloride, tin tetrachloride and antimony trichloride respectively, mix the three solutions and add concentrated hydrochloric acid to obtain the active layer precursor solution; 4) The intermediate layer precursor solution is coated onto the surface of the pretreated titanium substrate, and the process is repeated several times after drying and calcination to form an intermediate layer coating; then the active layer precursor solution is coated onto the surface of the intermediate layer coating, and the process is repeated several times after drying and calcination to form an active layer coating.

[0007] Preferably, the titanium matrix in step 1) is a plate-shaped or mesh-shaped titanium matrix.

[0008] Preferably, the titanium substrate in step 1) is subjected to sandblasting, ultrasonic degreasing with acetone, etching with oxalic acid aqueous solution, and washing and drying.

[0009] Preferably, the oxalic acid aqueous solution in step 1) has a mass concentration of 10%-20%, an acid etching temperature of 95-100℃, and an etching time of 1-3 hours.

[0010] Preferably, the soluble tin salt in steps 2) and 3) is tin tetrachloride, the soluble antimony salt is antimony trichloride, and the alcohol solution is isopropanol solution.

[0011] Preferably, in step 2), the intermediate layer precursor solution, based on the total molar amount of the three metal elements Ir, Sn and Sb, has a molar percentage of Ir of 7%-10%, a sum of molar percentages of Sn and Sb of 90%-93%, and a molar ratio of Sn to Sb of 6:1-8:1.

[0012] Preferably, in step 3), the active layer precursor solution contains Ru at a molar percentage of 4%-10% and Sn and Sb at a sum of 90%-96% based on the total molar amounts of the three metal elements Ru, Sn and Sb, and the molar ratio of Sn to Sb is 6:1-8:1.

[0013] Preferably, the volume ratio of the mixed solution to concentrated hydrochloric acid in steps 2) and 3) is 15:1 to 30:1.

[0014] Preferably, in step 4), the drying is performed at 80-120°C for 10-15 minutes in an air atmosphere, and the calcination is performed at 450-550°C for 5-15 minutes in an air atmosphere; the intermediate layer coating is repeated 2-8 times, and the active layer coating is repeated 10-15 times; after the last calcination of the active layer, it is then cured at 450-550°C for 1-2 hours.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The low-noble-metal long-life DSA anode of this invention comprises a titanium substrate and a composite coating formed on the surface of the titanium substrate. The composite coating includes an intermediate layer and an active layer. This structural design comprehensively considers the characteristics of different noble metal components in the oxygen evolution reaction (OER) system and their synergistic relationships. Specifically, the Ru oxide in the active layer exhibits good OER catalytic activity. As an outer active component, it promotes the OER reaction, which helps reduce cell voltage, thereby reducing electrolysis energy consumption and operating costs. Simultaneously, it helps reduce the high-potential oxidation load on the electrode surface during long-term electrolysis, playing a positive role in maintaining the long-term performance of the electrode. The Ir oxide in the intermediate layer has good electrochemical stability, which helps improve the structural stability of the composite coating. During multiple coating, drying, and calcination processes, a transition region may form between the intermediate layer and the active layer, possibly accompanied by interdiffusion and local interactions of elements such as Ir and Ru, which also helps improve the stability of the Ru component in the active layer. The above-mentioned composite structure design allows the electrode to maintain good oxygen evolution activity, low cell voltage, and long service life while also being economical. At the same time, the low Ir content design of the intermediate layer is also conducive to improving the utilization efficiency of Ir and reducing the dependence on the high-priced precious metal Ir, thereby reducing the electrode manufacturing cost. Attached Figure Description

[0016] Figure 1 The following are surface topography images of the DSA anode, where a) is the surface topography image of Example 1; b) is the surface topography image of Example 2; c) is the surface topography image of Comparative Example 1; d) is the surface topography image of Comparative Example 2; and e) is the surface topography image of Comparative Example 6.

[0017] Figure 2 This is the polarization curve of the DSA anode.

[0018] Figure 3 These are the accelerated life test results for the DSA anode.

[0019] Figure 4 This is a schematic diagram of the DSA anode structure of this application, wherein 1 is a titanium substrate; 2 is an intermediate coating layer; and 3 is an active coating layer. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The embodiments described are for illustration only and are not intended to limit the scope of protection of the present invention.

[0021] Example 1 1) Titanium matrix pretreatment A titanium sheet with a length of 5 cm, a width of 1.25 cm, a thickness of 0.1 cm, and a purity of 99.9% was selected as the metal substrate and sandblasted. Then, it was ultrasonically treated in acetone solution for 2 h to remove surface oil. After rinsing with deionized water, it was etched in a 10% oxalic acid aqueous solution at 98℃ for 2 h. Finally, it was cleaned with deionized water and dried for later use.

[0022] 2) Preparation of intermediate layer precursor solution First, separate 0.2 mol / L isopropanol solutions of iridium chloro-iridium acid (H₂IrCl₆), tin tetrachloride (SnCl₄), and antimony trichloride (SbCl₃) were prepared. Then, a mixed solution was prepared at a volume ratio of H₂IrCl₆:SnCl₄:SbCl₃ of 8:80.5:11.5. Finally, concentrated hydrochloric acid was added at a volume ratio of 20:1 to obtain the intermediate layer precursor solution. Since the concentration of each precursor solution was 0.2 mol / L, the volume ratio of each precursor solution corresponds to the molar ratio of each metal element.

[0023] 3) Preparation of active layer precursor solution First, 0.2 mol / L isopropanol solutions of ruthenium trichloride (RuCl3), tin tetrachloride (SnCl4), and antimony trichloride (SbCl3) were prepared separately. Then, a mixed solution was prepared at a volume ratio of RuCl3:SnCl4:SbCl3 of 10:78.75:11.25. Finally, concentrated hydrochloric acid was added at a volume ratio of 20:1 to the mixed solution to obtain the active layer precursor solution.

[0024] 4) Coating preparation First, an intermediate layer was prepared. The intermediate layer precursor solution was uniformly coated onto the surface of the titanium substrate using a brush, dried in an oven at 120°C for 10 min, and then immediately transferred to a muffle furnace at 500°C for calcination for 10 min. After the electrode cooled to room temperature, the coating-drying-calcination process was repeated 5 times to obtain the anode substrate with the intermediate layer. Subsequently, the precursor solution was replaced with the active layer solution, and the above coating-drying-calcination process was repeated 10 times. Finally, the electrode was placed in a muffle furnace at 500°C for high-temperature curing for 1 h to obtain the anode of Example 1. The loadings of Ir and Ru were 0.23 g / m³. 2 and 0.32 g / m 2 .

[0025] Example 2 The difference from Example 1 is that the volume ratio of H2IrCl6, SnCl4, and SbCl3 in the intermediate layer precursor solution is 10:78.75:11.25. The molar percentage of Ir, Sn, and Sb is 10%. All other conditions are the same as in Example 1. The loadings of Ir and Ru are 0.30 g / m³. 2 and 0.32 g / m 2 .

[0026] Comparative Example 1 The difference from Example 1 is that no intermediate layer is prepared; only the active layer is prepared. Specifically, the active layer precursor solution is directly coated onto the titanium substrate, and the electrode is prepared entirely according to the active layer preparation process in Example 1 (the same "coating-drying-calcining" process and high-temperature curing process). The Ru loading is 0.32 g / m³. 2 .

[0027] Comparative Example 2 The difference from Example 1 is that no active layer is prepared; only an intermediate layer is prepared. Specifically, after preparing the intermediate layer on the titanium substrate according to Example 1 (completing 5 "coating-drying-calcining" processes), no active layer is coated, and the electrode is directly cured at 500°C for 1 hour to obtain the electrode. The Ir loading is 0.23 g / m². 2 .

[0028] Comparative Example 3 The difference from Example 1 is that the volume ratio of H2IrCl6, TaCl5, and SnCl4 in the precursor solution of the intermediate layer is 8:80.5:11.5. The molar percentages of Ir, Ta, and Sn, based on the total molar amount of the three metal elements, are 8%, 80.5%, and 11.5%, respectively. The volume ratio of H2IrCl6, RuCl3, and SnCl4 in the precursor solution of the active layer is 10:78.75:11.25. The molar percentages of Ir, Ru, and Sn, based on the total molar amount of the three metal elements, are 10%, 78.75%, and 11.25%, respectively. All other conditions are the same as in Example 1. The loadings of Ir, Ta, and Ru are 0.81, 1.64, and 2.65 g / m³, respectively. 2 .

[0029] Comparative Example 4 The difference from Example 1 is that the volume ratio of H2IrCl6, SnCl4, and SbCl3 in the precursor solution of the intermediate layer is 80:40:0. The molar percentages of Ir, Sn, and Sb, based on the total molar amounts of the three metal elements, are 66.7%, 33.3%, and 0%, respectively. The volume ratio of RuCl3, SnCl4, and SbCl3 in the precursor solution of the active layer is 20:20:60. The molar percentages of Ir, Sn, and Sb, based on the total molar amounts of the three metal elements, are 20%, 20%, and 60%, respectively. All other conditions are the same as in Example 1. The loadings of Ir and Ru are 1.540 and 0.631 g / m³, respectively. 2 .

[0030] Comparative Example 5 Unlike Example 1, this comparative example does not employ a layered construction method with an intermediate layer and an active layer. Instead, H₂IrCl₆, RuCl₃, SnCl₄, and SbCl₃ are prepared in the same precursor solution. The total molar percentages of Ir, Ru, Sn, and Sb are 2.67%, 6.67%, 79.33%, and 11.33%, respectively. Except for the coating structure being changed from a layered composite structure to a single-layer mixed structure, all other preparation conditions are the same as in Example 1. The loadings of Ir and Ru are also the same as in Example 1.

[0031] Comparative Example 6 The difference from Example 1 is that the volume ratio of H2IrCl6, SnCl4, and SbCl3 in the intermediate layer precursor solution is 2:85.75:12.25. The molar percentage of Ir, Sn, and Sb is 2%. All other conditions are the same as in Example 1. The loadings of Ir and Ru are 0.06 g / m³. 2 and 0.32 g / m 2 . The electrodes obtained in Examples 1-2 and Comparative Examples 1-2 and 6 were characterized by field emission scanning electron microscopy, such as... Figure 1 As shown. Compared with Comparative Example 1, the composite coatings obtained in Examples 1 and 2 have a denser and more uniform surface, with relatively smaller crack sizes, indicating that the synergistic construction of the intermediate layer and the active layer helps improve the surface morphology and structural integrity of the composite coating. The sample in Comparative Example 2 containing only the intermediate layer has a denser surface, indicating that the intermediate layer has good film-forming properties and can provide a more stable foundation for the subsequent construction of the active layer. Compared with Comparative Example 2, Example 1 still exhibits a certain surface crack structure, indicating that while maintaining good structural integrity, the composite coating still possesses surface features conducive to electrolyte contact.

[0033] Electrochemical performance tests were performed on Examples 1-2 and Comparative Examples 1-2 and 6. A three-electrode system was used, with a test solution of 0.5 mol / L H₂SO₄. The working electrode was the electrode to be tested, the counter electrode was a platinum electrode, and the reference electrode was a saturated calomel electrode. Polarization curves were measured, and the results are as follows: Figure 2 As shown. At a current density of 10 mA / cm² 2 At that time, the oxygen evolution potentials of Examples 1 and 2 were 1.40 V and 1.39 V, respectively, both lower than those of Comparative Example 1 (1.46 V), Comparative Example 2 (1.54 V), and Comparative Example 6 (1.43 V). The composite structure electrodes shown in Examples 1-2 exhibited good oxygen evolution activity, indicating that the composite structure design of the intermediate layer and the active layer can maintain good oxygen evolution electrocatalytic performance while improving electrode stability.

[0034] Accelerated life tests were performed on Examples 1-2 and Comparative Examples 1-6. The electrode under test was the anode, the titanium sheet was the cathode, the electrode spacing was 2 cm, the test conditions were 0.5 mol / L sulfuric acid solution at 25 °C, and the current density was 1 A / cm². 2 The result is as follows Figure 3 As shown. The accelerated lifetimes of Examples 1 and 2 were 214 h and 251 h, respectively; the accelerated lifetimes of Comparative Examples 1, 2, 3, 4, 5, and 6 were 14 h, 139 h, 235 h, 182 h, 118 h, and 25 h, respectively. Calculated based on unit load (after converting the loads of noble metals Ru and Ta in the electrode to equivalent Ir loads according to their prices, and then combining this with the actual Ir load to calculate the lifetime per unit load), the accelerated lifetimes of Examples 1 and 2 were 712.46 h·m, respectively. 2 / g and 709.04 h·m 2 / g; The accelerated life calculated per unit load for Comparative Examples 1, 2, 3, 4, 5, and 6 was 210.95 h·m. 2 / g, 594.02 h·m 2 / g、202.34 h·m 2 / g, 214.92 h·m 2 / g、465.9h·m 2 / g and 197.83 h·m 2 / g. The above results show that Examples 1 and 2 both exhibit longer accelerated lifetimes and higher unit load lifetimes, indicating that the layered composite structure of the intermediate layer / active layer used in this invention can effectively improve the stability of the DSA anode under oxygen evolution conditions and significantly improve the utilization efficiency of precious metals under lower precious metal input conditions. Although Comparative Examples 3 and 4 have longer absolute accelerated lifetimes due to higher precious metal loadings, their unit load lifetimes are significantly lower than those of Examples 1 and 2, indicating that simply increasing the amount of precious metals cannot effectively improve the utilization efficiency of precious metals. In particular, Comparative Example 5, under the same Ir and Ru loadings as Example 1, still has lower accelerated lifetimes and unit load lifetimes than Example 1, further illustrating that the performance improvement of this invention comes not only from the elemental system itself, but also from the layered construction method of the intermediate layer and active layer. Comparative Example 6 shows that even under lower Ir content conditions, this layered composite structure can still maintain a certain degree of electrode stability.

[0035] In summary, this invention constructs a composite coating structure consisting of an intermediate layer and an active layer, enabling the two layers to work synergistically. This improves the stability and lifespan of the electrode while maintaining good oxygen evolution performance, and also helps to improve the utilization efficiency of precious metals and reduce dependence on the high-priced precious metal Ir.

[0036] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the spirit and scope of the present invention, and all such modifications and improvements should fall within the protection scope of the present invention.

Claims

1. A long-life DSA anode made of low-precious metals, characterized in that, The system comprises a titanium substrate and a composite coating formed on the surface of the titanium substrate. The composite coating, from the inside out, includes an intermediate layer coating and an active layer coating. The intermediate layer coating is a composite oxide coating containing Ir oxide, Sn oxide, and Sb oxide, wherein, based on the total molar amount of the three metal elements Ir, Sn, and Sb, the molar percentage of Ir is 7%-10%, the sum of the molar percentages of Sn and Sb is 90%-93%, and the molar ratio of Sn to Sb is 6:1-8:

1. The active layer coating is a composite oxide coating containing Ru oxide, Sn oxide, and Sb oxide, wherein, based on the total molar amount of the three metal elements Ru, Sn, and Sb, the molar percentage of Ru is 4%-10%, the sum of the molar percentages of Sn and Sb is 90%-96%, and the molar ratio of Sn to Sb is 6:1-8:

1.

2. The low-precious-metal long-life DSA anode according to claim 1, characterized in that, The noble metal Ir loading of the low-noble-metal long-life DSA anode is 0.21-0.30 g / m³. 2 The loading of the precious metal Ru is 0.13-0.32 g / m³. 2 .

3. A method for preparing the low-noble-metal long-life DSA anode of claim 1, characterized in that, Includes the following steps: 1) Pretreatment of the titanium matrix; 2) Prepare isopropanol solutions of chloroiridic acid, tin salt and antimony salt respectively. Mix the above three solutions and add concentrated hydrochloric acid to obtain the intermediate layer precursor solution. 3) Prepare isopropanol solutions of ruthenium trichloride, tin salt and antimony salt respectively. Mix the above three solutions and add concentrated hydrochloric acid to obtain the active layer precursor solution. 4) The intermediate layer precursor solution is coated onto the surface of the pretreated titanium substrate, and the process is repeated several times after drying and calcination to form an intermediate layer coating. The active layer precursor solution is then coated onto the surface of the intermediate layer coating, and the process is repeated several times after drying and calcination to form the active layer coating.

4. The preparation method according to claim 3, characterized in that: Step 1) The titanium matrix is ​​a plate-shaped or mesh-shaped titanium matrix.

5. The preparation method according to claim 3, characterized in that: Step 1) The titanium substrate is subjected to sandblasting, ultrasonic degreasing with acetone, etching with oxalic acid aqueous solution, and water washing and drying in sequence; the oxalic acid aqueous solution has a mass concentration of 10%-20%, the acid etching temperature is 95-100℃, and the etching time is 1-3 hours.

6. The preparation method according to claim 3, characterized in that: In step 2), the tin salt in the intermediate layer precursor solution is tin tetrachloride and the antimony salt is antimony trichloride; in step 3), the tin source in the active layer precursor solution is tin tetrachloride and the antimony source is antimony trichloride; the solvents in steps 2) and 3) are both isopropanol.

7. The preparation method according to claim 3, characterized in that: In step 2), the intermediate layer precursor solution contains Ir with a molar percentage of 7%-10% and Sn and Sb with a combined molar percentage of 90%-93%, based on the total molar amount of the three metal elements Ir, Sn and Sb, and the molar ratio of Sn to Sb is 6:1-8:

1.

8. The preparation method according to claim 3, characterized in that: In step 3), the active layer precursor solution contains Ru with a molar percentage of 4%-10% and Sn and Sb with a combined molar percentage of 90%-96%, based on the total molar amount of the three metal elements Ru, Sn and Sb, and the molar ratio of Sn to Sb is 6:1-8:

1.

9. The preparation method according to claim 3, characterized in that: Step 4) Drying is performed at 80-120℃ for 10-15 minutes in air; calcination is performed at 450-550℃ for 5-15 minutes in air; the intermediate layer is coated 3-5 times and the active layer is coated 10-15 times; after the last calcination of the active layer, it is then cured at 450-550℃ for 1-2 hours.

10. The preparation method according to claim 3, characterized in that: In step 2), the volume ratio of the intermediate layer precursor mixture solution to concentrated hydrochloric acid is 15:1-30:

1. In step 3), the volume ratio of the active layer precursor mixture solution to concentrated hydrochloric acid is 15:1-30:1.

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