A method for the preparation of a shape-stable electrode interlayer by alternate oxidation and reduction

Abstract

The present application belongs to the field of environmental electrocatalysis, and particularly relates to a method for preparing an intermediate layer of shape-stable electrodes by alternate oxidation and reduction. The existing shape-stable electrodes have problems such as not being tightly combined with the base material, being easily oxidized, bubbling, and falling off, and the general strategy to solve the problems is to increase the intermediate layer. However, the existing preparation method of the intermediate layer is complicated, low in efficiency, and seriously pollutes the environment. The present application innovatively realizes the deposition of praseodymium oxide and samarium oxide on the surface of a titanium base by the method of alternate oxidation and reduction, and forms a heavily doped semiconductor of a praseodymium-samarium composite metal oxide solid solution through a high-temperature calcination process. The praseodymium-samarium composite metal oxide has extremely high mechanical strength, excellent combination ability with the base and the surface active layer, and excellent corrosion and oxidation resistance as the intermediate layer of the shape-stable electrode. The method can be used for large-scale batch preparation of electrocatalytic shape-stable electrodes for water treatment, and has the advantages of short process, simple process, low energy consumption, and less pollution.

Description

1. Technical Field

[0001] The present invention belongs to the field of environmental electrocatalysis and specifically relates to a method for preparing a dimensionally stable electrode intermediate layer by alternating redox reactions. This method deposits praseodymium oxide and samarium oxide on the surface of a titanium substrate using an alternating redox process to form a heavily doped semiconductor comprising a praseodymium-samarium composite metal oxide solid solution. This significantly improves the bonding between the intermediate layer and the substrate and active surface layer, as well as its corrosion and oxidation resistance. The method has the advantages of a short process, simple technology, low energy consumption, and minimal pollution. 2. Background Technology

[0002] Electrochemical water treatment technology has gained widespread recognition and application in the advanced treatment of industrial wastewater due to its advantages, including ease of operation, ease of deployment, process flexibility, and thorough treatment results. This technology is particularly well-suited for complex components in industrial wastewater that are difficult to treat using traditional methods, effectively catalyzing the decomposition and deep purification of various toxic organic compounds in industrial wastewater, regardless of their type and nature. Electrocatalytic advanced oxidation technology has demonstrated tremendous potential and prospects for the advanced treatment of industrial wastewater generated by industries such as the chemical, petrochemical, pesticide, and coking industries.

[0003] However, despite the many advantages of electrocatalytic advanced oxidation technology, it still faces some challenges and limitations in its actual engineering application. First, the life of the electrocatalytic electrode is short, which increases the operating cost and maintenance difficulty. Second, the energy efficiency of the technology needs to be improved to reduce energy consumption and operating costs. Finally, the low degree of systematization also limits its promotion and popularization in large-scale applications. In electrocatalytic water treatment technology, electrode materials play a vital role. It is a key factor in realizing electrochemical reactions and improving electrolysis efficiency. Therefore, factors such as the performance, stability and production cost of electrode materials directly affect the widespread application of electrochemical advanced oxidation methods in industrial wastewater treatment. In order to improve the overall performance and efficiency of electrocatalytic advanced oxidation technology, in-depth research on the preparation, modification and optimization of electrode materials is needed to overcome the limitations of existing technologies and promote their widespread application in the field of industrial wastewater treatment.

[0004] Dimensionally stable electrodes, as a type of inactive electrode material, have a history of more than 70 years in industrial applications. Their notable features include high oxygen evolution overpotential, excellent corrosion resistance and cost-effectiveness. However, the internal distortion problem of traditional dimensionally stable electrodes leads to limitations such as large stress in the deposited layer, insufficient coating stability and short service life. These defects restrict their widespread application in wastewater treatment. The original titanium-based dimensionally stable electrodes were prepared by directly electrodepositing metal oxides on a titanium substrate. However, after anodic polarization, titanium oxide with poor conductivity is easily formed at the interface between the substrate and the coating, causing the coating to fall off and the anode to fail. These problems are mainly reflected in the uneven quality of the coating, weak bonding with the substrate and short anode life. Therefore, in-depth research and technological innovation are needed to address these challenges in order to improve the performance and stability of dimensionally stable electrodes in environmental governance.

[0005] To improve the bonding strength between the titanium substrate and the coating and extend the service life of the anode, researchers in the field of environmental materials have successfully developed a titanium-based lead dioxide anode containing an intermediate layer. Patent CN201110044764.7 describes a technique for preparing a tantalum-containing intermediate layer on a titanium substrate by thermal decomposition. This intermediate layer effectively enhances the protection of the titanium substrate, delays the passivation process, and significantly improves the stability and service life of the oxide electrode. Patent CN201110195199.4 discloses a method for coating tin-antimony oxide on the surface of a titanium plate as an intermediate layer. This method significantly improves the oxygen evolution potential of the electrode, effectively extends its service life, and improves the current efficiency of the electrocatalytic oxidation reaction system. Patent CN201310153286.2 demonstrates a method for preparing a metal oxide anode with a cold-sprayed tantalum intermediate layer. This process is simple and reliable, and the resulting electrode has the characteristics of high operating current density, high breakdown potential, good stability, and long service life. In their master's thesis, Li Haibao et al. reported on the preparation of Ti / lead oxide electrodes with a tin-antimony interlayer. The study found that the introduction of the interlayer significantly improved the electrode's electrochemical, catalytic, and electrochemical lifespan. However, currently available interlayers are either produced using expensive physical deposition methods, which are extremely costly and impose significant limitations on electrode size. Lower-cost tin-antimony oxide coatings can only be prepared using a sol-gel method, which typically requires 20–50 manual coatings and a complex drying and calcining process. The preparation of a single electrode can take 10 hours or even longer, generating waste gases containing large amounts of nitrogen oxides, carbon dioxide, and fly ash, resulting in severe secondary pollution.

[0006] Analysis of current challenges in preparing interlayers for dimensionally stable electrocatalytic electrodes highlights the urgent need for a new method that can reduce production costs, simplify the process, automate production, and minimize secondary pollution. This novel interlayer preparation method could replace traditional processes with a novel formulation and process, improving electrocatalytic electrode production efficiency, reducing production costs, and increasing economic benefits. Furthermore, it could contribute to improving environmental quality, protecting human health, and facilitating sustainable social development. 3. Summary of the Invention

[0007] The present invention addresses the problems existing in the prior art and aims to provide a method for preparing a dimensionally stable electrode intermediate layer by using an alternating redox process. This method deposits praseodymium oxide and samarium oxide on the surface of a titanium substrate using an alternating redox process to form a heavily doped semiconductor comprising a praseodymium-samarium composite metal oxide solid solution. This significantly improves the bonding between the intermediate layer and the substrate and active surface layer, as well as its corrosion and oxidation resistance. The method offers advantages such as a short process flow, simple technology, low energy consumption, and minimal pollution.

[0008] In order to achieve the above-mentioned object, the technical solution of the present invention is a method for preparing a dimensionally stable electrode intermediate layer by alternating redox reactions, characterized in that it comprises the following steps:

[0009] Step 1: Select a titanium plate of appropriate area as the substrate, polish it with 20-mesh, 200-mesh, and 800-mesh sandpaper until smooth to remove the surface oxide layer, then place it in a 10% oxalic acid aqueous solution and boil it for 30 minutes, and then store it in a 1% oxalic acid aqueous solution for later use;

[0010] Step 2: preparing electroplating solutions containing praseodymium and samarium elements, respectively, wherein the mass ratio of the praseodymium electroplating solution is praseodymium nitrate: nitric acid: sodium lauryl sulfate: water = 24:10:0.24:100, and the mass ratio of the samarium electroplating solution is samarium nitrate: nitric acid: pyrophosphoric acid: water = 35:24:0.25:100, mixing and stirring them until completely clarified and then setting aside;

[0011] Step 3: Place two titanium plates of equal area described in Step 1 in the praseodymium electroplating solution described in Step 2, connect them to the two ends of a periodically commutated DC power supply, set the commutation period to 5 seconds, the duty cycle to 1:1, and continue the treatment for 30 minutes;

[0012] Step 4: Place the titanium plate with praseodymium plated on the surface obtained in step 3 in the samarium electroplating solution, set the switching period to 10 seconds, the duty cycle to 1:1, and continue the treatment for 30 minutes;

[0013] Step 5: Repeat steps 3 and 4 4 times to alternately form praseodymium and samarium coatings on the surface of the titanium plate through redox reactions;

[0014] Step 6: calcining the titanium substrate on which praseodymium and samarium were deposited in step 5 at a high temperature, wherein the calcination temperature is controlled at 1000° C. to 1200° C. and the calcination time is 2 to 4 hours to form a heavily doped semiconductor of a praseodymium-samarium composite metal oxide solid solution;

[0015] Step 7: Cooling the calcined titanium substrate to obtain a dimensionally stable electrode having a praseodymium-samarium composite metal oxide intermediate layer.

[0016] The above technical solution is further defined as follows: in the alternating redox deposition process in step 3, the current density is 50 mA / cm 2 Up to 150mA / cm 2 .

[0017] The above technical solution is further defined as follows: the high-temperature calcination treatment in step six is ​​carried out in an oxidizing atmosphere, and the calcination heating rate is 5° C. / min to 10° C. / min.

[0018] The above technical solution is further defined as follows: the bonding strength between the intermediate layer of praseodymium-samarium composite metal oxide and the titanium substrate in step seven should be greater than 20 MPa.

[0019] The above technical solution is further defined as follows: after step seven, a surface active layer is further coated on the praseodymium-samarium composite metal oxide intermediate layer to form a complete dimensionally stable electrode.

[0020] The above technical solution is further defined as follows: the surface active layer of the dimensionally stable electrode is at least one of metal oxides, noble metals or alloys thereof.

[0021] The present invention is beneficial in that:

[0022] 1. Improved electrode stability: Through an alternating redox process, praseodymium oxide and samarium oxide are densely deposited on the titanium substrate, forming a praseodymium-samarium composite metal oxide solid solution as the intermediate layer of a dimensionally stable electrode. This structure significantly improves the electrode's mechanical strength and reduces oxidation, blistering, and shedding, thereby significantly enhancing its stability and durability.

[0023] 2. Simplified preparation process: Compared with the traditional intermediate layer preparation method, the alternating redox process of the present invention is simpler, has a shorter process, and can

[0024] Low consumption and less secondary pollution. This not only improves preparation efficiency, but also reduces production costs, making mass production of dimensionally stable electrodes possible.

[0025] 3. Enhanced corrosion and oxidation resistance: The praseodymium-samarium composite metal oxide, as an intermediate layer, not only enhances the bonding ability with the substrate and the surface active layer, but also imparts excellent corrosion and oxidation resistance to the electrode. This enables the electrode to operate stably and long-term in applications such as water treatment, reduces maintenance and replacement frequency, and improves overall economic benefits. IV. Description of the Figures

[0026] In order to more clearly illustrate the specific embodiments of the present invention, the following briefly describes the drawings used in the description of the specific embodiments.

[0027] Figure 1 This is a scanning electron microscope image of the praseodymium-samarium composite metal oxide intermediate layer prepared in Example 1 of the present invention.

[0028] Figure 2 This is an X-ray diffraction image of the praseodymium-samarium composite metal oxide intermediate layer prepared in Example 1 of the present invention.

[0029] Figure 3 These are AC impedance spectra of titanium-based electrodes with a traditional antimony-doped tin oxide (tin-antimony composite metal oxide) intermediate layer, a praseodymium-samarium composite metal oxide intermediate layer, and a lead oxide / praseodymium-samarium composite metal oxide intermediate layer in Example 2 of the present invention.

[0030] Figure 4 This is a time-voltage variation diagram of the accelerated life experiment of the titanium-based ruthenium-iridium electrode with an antimony-doped tin oxide intermediate layer and the titanium-based ruthenium-iridium electrode with a praseodymium-samarium composite metal oxide intermediate layer in Example 3 of the present invention.

[0031] Figure 5 The treatment effects of 15 mg / L sulfamethoxazole on a titanium-based electrode with a lead oxide / antimony-doped tin oxide intermediate layer and a titanium-based electrode with a lead oxide / praseodymium-samarium composite metal oxide intermediate layer were compared. V. Specific Implementation Methods

[0032] The present invention is described in detail below with reference to the accompanying drawings and embodiments:

[0033] Example 1:

[0034] A method for preparing a dimensionally stable electrode intermediate layer by alternating redox reactions comprises the following steps: first, selecting a titanium plate of suitable area as a substrate, polishing it with 20-mesh, 200-mesh, and 800-mesh sandpaper until smooth to remove the surface oxide layer, then placing it in a 10% oxalic acid aqueous solution and boiling it for 30 minutes, and then storing it in a 1% oxalic acid aqueous solution for later use; respectively preparing electroplating solutions containing praseodymium and samarium, wherein the mass ratio of the praseodymium electroplating solution is praseodymium nitrate: : nitric acid: sodium lauryl sulfate: water = 24:10:0.24:100, the mass ratio formula of samarium electroplating solution is samarium nitrate: nitric acid: pyrophosphoric acid: water = 35:24:0.25:100, respectively, mixed until completely clarified and set aside; take two titanium plates of equal area described in the previous steps and place them in the praseodymium electroplating solution, respectively connect them to the two ends of a periodic commutation DC power supply, set the commutation period to 5s, the duty cycle to 1:1, continue the treatment for 30min, and the current density to 50mA / cm 2 Up to 150mA / cm 2 Then, the titanium plate with praseodymium on its surface was placed in the samarium electroplating solution, with a switching period of 10 seconds, a duty cycle of 1:1, and a continuous treatment of 30 minutes at a current density of 50 mA / cm 2 Up to 150mA / cm 2 ; Repeat the operation 4 times to alternately form praseodymium and samarium coatings on the surface of the titanium plate through redox reactions; The titanium substrate on which praseodymium and samarium are deposited is subjected to a high-temperature calcination treatment, the calcination treatment being carried out in an oxidizing atmosphere at a calcination heating rate of 5°C / min to 10°C / min, the calcination temperature being controlled at 1000°C-1200°C, and the calcination time being 2h to 4h to form a heavily doped semiconductor of a praseodymium-samarium composite metal oxide solid solution; Finally, the calcined titanium substrate is cooled to obtain a shape-stable electrode having a praseodymium-samarium composite metal oxide intermediate layer (see Figure 1 and Figure 2 ), where the bonding strength between the praseodymium-samarium composite metal oxide intermediate layer and the titanium substrate should be greater than 20 MPa. After the praseodymium-samarium composite metal oxide intermediate layer is obtained, a surface active layer should be further coated thereon to form a complete, dimensionally stable electrode. The surface active layer is composed of at least one of a metal oxide, a precious metal, or an alloy thereof.

[0035] Example 2

[0036] The titanium-based electrode with a dimensionally stable electrode intermediate layer, i.e., a praseodymium-samarium composite metal oxide intermediate layer, obtained in Example 1, was further used to prepare a lead oxide active electrode by electrodeposition. The binding force of the lead oxide active electrode was 26.27 MPa. The resistivity of the lead oxide active electrode was measured by AC impedance spectroscopy. The results were as follows: Figure 3 As shown, its resistivity is 2.78 micro-ohm·m, which is 20% lower than that of the traditional antimony-doped tin oxide electrode intermediate layer.

[0037] Example 3

[0038] The titanium-based ruthenium-iridium electrode was prepared by electrodeposition using the praseodymium-samarium composite metal oxide obtained in Example 1 as the intermediate layer. The current density was controlled to be 10 A / cm in a 1 mol / L hydrochloric acid aqueous solution. 2 , conduct enhanced life test, the results are as follows Figure 4 As shown, the enhanced life is 46% longer than that of the titanium-based ruthenium-iridium electrode with antimony-doped tin oxide as the electrode intermediate layer.

[0039] Example 4

[0040] The titanium-pole lead oxide electrode was prepared by electrodeposition using the dimensionally stable electrode intermediate layer obtained in Example 1, i.e., the praseodymium-samarium composite metal oxide, as the intermediate layer. The catalytic activity was evaluated by treating the electrode with 15 mg / L sulfamethoxazole. The results are shown in FIG. Figure 5 As shown, after 15 minutes of reaction, the conversion rate of sulfamethoxazole was 98.2%. Under the same operating conditions, the conversion rate of sulfamethoxazole on the titanium lead oxide electrode with antimony-doped tin oxide as the electrode intermediate layer was 82.4%.

[0041] The specific embodiments described above are only used to specifically illustrate the spirit of the present invention, and the scope of protection of the present invention is not limited thereto. For those skilled in the art, it is of course possible to easily make other embodiments by changing, replacing or modifying the technical contents disclosed in this specification, and these other embodiments should all be included in the scope of protection of the present invention.

Claims

1. A method for preparing a dimensionally stable electrode intermediate layer by alternating redox reactions, characterized in that: The method comprises the following steps: Step 1: Select a titanium plate of appropriate area as the substrate, polish it with 20-mesh, 200-mesh, and 800-mesh sandpaper until smooth to remove the surface oxide layer, then boil it in a 10% oxalic acid aqueous solution for 30 minutes, and store it in a 1% oxalic acid aqueous solution for later use; Step 2: Prepare electroplating solutions containing praseodymium and samarium respectively, wherein the mass ratio of the praseodymium electroplating solution is praseodymium nitrate: nitric acid: sodium lauryl sulfate: water = 24: 10:0.24:100, the mass ratio of samarium plating solution is samarium nitrate: nitric acid: pyrophosphoric acid: water = 35: 24：0.25：100； Step 3: Place two titanium plates described in step 1 in the praseodymium electroplating solution described in step 2, connect them to the two ends of a periodically commutated DC power supply, set the commutation period to 5 seconds, the duty cycle to 1:1, and continue the treatment for 30 minutes; Step 4: Place the titanium plate with praseodymium plated on the surface obtained in step 3 in the samarium electroplating solution, set the switching period to 10 seconds, the duty cycle to 1:1, and continue the treatment for 30 minutes; Step 5: Repeat steps 3 and 4 4 times to alternately form praseodymium and samarium coatings on the surface of the titanium plate through redox reactions; Step 6: calcining the titanium substrate on which praseodymium and samarium were deposited in step 5 at a high temperature, wherein the calcination temperature is controlled at 1000° C. to 1200° C. and the calcination time is 2 to 4 hours to form a heavily doped semiconductor of a praseodymium-samarium composite metal oxide solid solution; Step 7: Cooling the calcined titanium substrate to obtain a dimensionally stable electrode having a praseodymium-samarium composite metal oxide intermediate layer.

2. The method for preparing a dimensionally stable electrode intermediate layer by alternating redox according to claim 1, wherein the deposition current density in step 3, step 4, and step 5 is 50 mA / cm 2 Up to 150mA / cm 2 .

3. A method for preparing a dimensionally stable electrode intermediate layer by alternating redox according to claim 1, wherein the high-temperature calcination treatment in step 6 is carried out in an oxidizing atmosphere at a calcination heating rate of 5°C / min to 10°C / min.

4. The method for preparing a dimensionally stable electrode intermediate layer by alternating redox according to claim 1, wherein the bonding strength between the praseodymium-samarium composite metal oxide intermediate layer and the titanium substrate in step 7 is greater than 20 MPa.

5. The method for preparing a dimensionally stable electrode intermediate layer by alternating redox according to claim 1, further comprising, after step 7, further coating a surface active layer on the praseodymium-samarium composite metal oxide intermediate layer to form a complete dimensionally stable electrode. 6 . The method for preparing a dimensionally stable electrode intermediate layer by alternating redox according to claim 5 , wherein the surface active layer is at least one of a metal oxide, a noble metal or an alloy thereof.

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