CN104294311A - Making method of platinum iridium oxide alloy electrode - Google Patents

Abstract

The invention discloses a making method of a platinum iridium oxide alloy electrode. The method includes the following steps: heating and stirring a platinum salt and sodium nitrate mixed solution to 55-65DEG C, carrying out evaporating crystallization, drying, grinding, calcining to obtain a mixture, washing the mixture by water to remove impurities, carrying out full wet grinding, and dispersing the wet ground mixture in a solvent to obtain a platinum dioxide solution; dispersing an iridium salt in the solvent, adding the platinum dioxide solution, adjusting the pH value to 14 by using sodium hydroxide, and dissolving and dispersing to obtain a coating solution; and coating a titanium plate with the coating solution, drying, calcining at 400-700DEG C, and cooling in air to obtain the platinum iridium oxide alloy electrode. The above platinum iridium oxide titanium anode electrocatalysis material prepared in the invention has the characteristics of fine crystsal grains and honeycomb shape; and the anodic chlorine evolution electrocatalytic activity is high, and the service life is long, so the electrode is suitable for preparing electrolyzed oxidizing water, and the use cost is reduced.

Description

A kind of preparation method of platinum iridium oxide alloy electrode

technical field

The invention belongs to the technical field of electrode materials, and in particular relates to a preparation method of a platinum-iridium oxide alloy titanium anode.

Background technique

In the electrochemical industry, the key technology is the research and development of electrode materials in the electrolytic cell. The composition and structure of the anode material determine its electrochemical activity and stability. In the chlor-alkali industry, seawater electrolysis and oxidative electrolysis water preparation, the three are all realized by electrolysis of sodium chloride solution, but the concentration of sodium chloride solution is very different, respectively 25wt%, 2-5wt% and 0.05- 0.1wt%, such a large concentration difference causes the difference in electrocatalytic reaction type and electrolysis efficiency, so the requirements for anode materials will also be different. Especially in the preparation of oxidized electrolyzed water, because the content of chloride ions is very small, there is not only chlorine evolution reaction at the anode, but also a large amount of oxygen evolution reaction. How to adjust the reaction selectivity between the two to improve the electrolysis efficiency of chlorine evolution reaction, It has a vital impact on the sterilization efficiency of oxidized electrolyzed water and the service life of electrodes.

At present, the Ru-based noble metal oxide electrodes widely used in the chlor-alkali industry have a difference of only 100mV between the chlorine evolution potential and the oxygen evolution potential, so when the chloride ion content is low, a large amount of oxygen evolution current will be generated, thereby destroying the metal oxide coating. The oxygen-deficient solid solution in the layer reduces the electrolytic efficiency and service life. Compared with Ru-based and other metal oxide electrodes, the chlorine and oxygen evolution activities of Ir-based metal oxides are slightly lower than Ru, but the service life of the electrodes will be greatly increased, but it is still difficult to meet the practical conditions under this special condition. Use needs. In order to further improve its electrolysis efficiency and service life, some inert oxides can be introduced into the active layer to provide chemical stability; such as TiO ₂ , Ta ₂ O ₅ , SiO ₂ , SnO ₂ and so on. In addition, some researchers have introduced Pt elemental substance into IrO ₂ to improve electrode stability, but metal Pt has a face-centered cubic structure, while IrO ₂ has a rutile structure, so there is a difference in co-solubility between the two, and PtO ₂ Like _IrO2 , it has a rutile structure, and it has a high oxygen evolution overpotential. If _PtO2 is added to _IrO2 , it can form a better solid solution structure, thereby reducing the oxygen evolution activity of the electrode material and improving the oxygen evolution overpotential. Chlorine selectivity improves electrode life.

At present, there are very few studies on the preparation of anode electrode materials for oxidized electrolyzed water. Among them, Zeng Xinping et al. (Journal of Tongji University (Natural Science Edition), 2011, 39(9): 1318-1323) reported the preparation of RuO ₂ by thermal decomposition. -SnO ₂ -TiO ₂ electrode, studies have shown that when the Ru content is 25%, its chlorine evolution activity is the best; but the life of the electrode strengthening test is only 105min, which cannot meet the actual use requirements, and the article does not report that the electrode is prepared for oxidation electrolysis water properties. In 2012, Zeng Xinping et al. (Journal of Electroanalytical Chemistry 677–680(2012) 133–138) studied the influence of Sn content on the electrolysis efficiency of the prepared oxidized electrolyzed water and the enhanced life of the electrode. The research showed that when the Sn content is less than When the content is 10%, the electrolysis efficiency is higher; when the content is 5%, the life of the intensive test is the longest, but it is only 85min, which cannot meet the actual use requirements. In 2013, Yu Hao of Chongqing University (Master's thesis of Chongqing University, 2013) prepared platinum-titanium electrodes and ruthenium-iridium electrodes, and found that the performance of oxidative electrolysis of water prepared by ruthenium-iridium electrodes was better than that of platinum-titanium electrodes. In addition, the actual service life of the platinum-titanium electrode reaches 1800h, while the actual service life of the ruthenium-iridium electrode with high iridium content reaches 2000h. Although the actual service life of the ruthenium-iridium electrode is higher than that of the platinum-titanium electrode, it still does not meet the requirements of the national standard GB-28234-2011 on the service life of electrode materials (greater than 3000h).

Contents of the invention

The purpose of the present invention is to provide a method for preparing a titanium-based platinum-iridium oxide alloy titanium anode to address the deficiencies in the prior art, and the electrocatalytic activity and stability of the obtained platinum-iridium oxide alloy electrode are significantly improved.

In order to achieve the above purpose, the following technical solutions are adopted:

A preparation method of a platinum-iridium oxide alloy electrode, comprising the following steps:

1) heating and stirring the mixed solution of platinum salt and sodium nitrate at 55-65°C, evaporating and crystallizing, drying, grinding, and roasting to obtain the mixture, washing with water to remove impurities, then fully wet grinding, and dispersing in a solvent to obtain a platinum dioxide solution;

2) Disperse the iridium salt into the solvent, and then add the above-mentioned platinum dioxide solution so that the metal ion concentration is 0.05-0.3 mol·L ^-1 , adjust the pH value of the solution to 14 with sodium hydroxide, dissolve and disperse to obtain a coating solution ;

3) Uniformly coat the coating solution on the titanium plate, dry it, then bake it at 400-700°C, and cool it in the air; the process of coating, drying, roasting and cooling is cycled 5-20 times to obtain platinum Iridium oxide alloy electrodes.

According to the above scheme, the platinum salt is H ₂ PtCl ₆ , K ₂ PtCl ₆ , Na ₂ PtCl ₆ , (NH ₄ ) ₂ PtCl ₆ , PtCl ₄ , Pt(NH ₃ ) ₂ (NO ₃ ) ₂ , PtCl ₂ ( PhCN) ₂ or PtCl ₂ (P(C ₆ H ₅ ) ₃ ) ₂ .

According to the above scheme, the iridium salt is Na ₂ IrCl ₆ , K ₂ IrCl ₆ , H ₂ IrCl ₆ , IrCl ₃ , IrCl ₄ , IrI ₄ or Ir(OAC) ₃ .

According to the above scheme, the metal ion concentration of the platinum salt in step 1) in the mixed solution is 0.05-0.3 mol·L ^-1 , and the concentration of sodium nitrate is 0.4-2.4 mol·L ^-1 .

According to the scheme, the solvent described in step 1) and step 2) is any one or a mixture of ethanol, n-butanol, Virahol, hydrochloric acid solution, nitric acid solution.

According to the above scheme, the dissolving and dispersing process described in step 2) is to alternately perform ultrasonic treatment and stirring treatment, and each time takes 3-10 hours for 30 minutes.

According to the above scheme, the calcination temperature of step 1) and step 3) is 500°C.

According to the above scheme, the molar ratio of platinum to iridium in step 2) is 1:1.

The beneficial effects of the present invention are:

The obtained platinum-iridium oxide-titanium anode electrocatalytic material has fine grains and honeycomb-like characteristics;

The anode has high electrocatalytic activity for chlorine analysis and long service life, is more suitable for the preparation of oxidized electrolyzed water, and reduces the use cost.

Description of drawings

Fig. 1: the field emission scanning electron microscope picture of different ratio platinum iridium oxide alloy titanium anode in embodiment 1;

Fig. 2: X-ray diffraction patterns of different proportions of platinum-iridium oxide alloy titanium anodes in Example 1.

Detailed ways

The following specific examples further illustrate the technical solutions of the present invention, but are not intended to limit the protection scope of the present invention.

The preparation process of the titanium-based platinum-iridium oxide alloy electrode of the present invention is as follows:

(1) Pretreatment of titanium substrate: sandblasting, degreasing, ultrasonic acid etching, cleaning, drying;

(2) Preparation of platinum dioxide: heat and stir the mixed solution of platinum salt and sodium nitrate at 55-65°C, evaporate and crystallize, dry, grind, and roast to obtain the mixture, then carry out sufficient wet grinding, and disperse in the solvent to obtain platinum dioxide Platinum solution; the metal ion concentration of the platinum salt is 0.05-0.3mol·L ^-1 , and the concentration of sodium nitrate is 0.4-2.4mol·L ^-1 ; the roasting process is sintering at 500°C for 30min.

(3) Configuration of the coating solution: disperse the iridium salt into the solvent, then add the above-mentioned platinum dioxide solution to make the metal ion concentration 0.05-0.3mol·L ^-1 , then adjust the pH value of the solution to 14 with sodium hydroxide , dissolved and dispersed to obtain a coating solution.

(4) Uniformly coat the coating solution on the titanium plate, dry it, then bake it at 400-700°C, and cool it in the air; the process of coating, drying, roasting and cooling is cycled 5-20 times to obtain Platinum iridium oxide alloy electrode.

Among them, the platinum salt can be H ₂ PtCl ₆ , K ₂ PtCl ₆ , Na ₂ PtCl ₆ , (NH ₄ ) ₂ PtCl ₆ , PtCl ₄ , Pt(NH ₃ ) ₂ (NO ₃ ) ₂ , PtCl ₂ (PhCN) ₂ or PtCl ₂ (P(C ₆ H ₅ ) ₃ ) ₂ .

The iridium salt may be Na ₂ IrCl ₆ , K ₂ IrCl ₆ , H ₂ IrCl ₆ , IrCl ₃ , IrCl ₄ , IrI ₄ or Ir(OAC) ₃ .

Optimally, the process of dissolving and dispersing in the above step (3) is to alternately perform ultrasonic treatment and stirring treatment, and each time takes 3-10 hours for 30 minutes.

Optimally, the roasting process in step 4) is preferably roasted at 500° C. for 10 min.

Optimally, in step 3), the molar ratio of platinum to iridium is preferably 1:1.

Example 1

A 10cm×5cm TA1 titanium plate was first sandblasted, then washed with 10% sodium carbonate solution for 10 minutes under the action of ultrasonic waves to remove oil, then washed with deionized water under the action of ultrasonic waves, and then washed with 10wt% oxalic acid Activated at 96°C for 40min, finally rinsed with deionized water, dried in the air, and stored in absolute ethanol.

Dissolve 2.590g of H ₂ PtCl ₆ in 50mL of ethanol and isopropanol solvent with a volume ratio of 1:1, so that the metal ion concentration in the solution is 0.1mol·L ^-1 , and stir evenly. Then add 3.400 g of solid sodium nitrate to the solution, stir and heat to 60° C., and keep stirring until the solvent evaporates completely. The mixture was then completely dried in an oven at 80°C to obtain a dry salt mixture, which was thoroughly ground in an agate mortar to make it evenly mixed. Then, it was calcined in a tube furnace at 500°C for 30 minutes with a heating rate of 5°C·min ^-1 to obtain a mixture of salts. After cooling the mixture to room temperature, it was washed several times with excess deionized water to remove excess salt. Then add 5ml of a mixed solution of absolute ethanol and isopropanol with a volume ratio of 1:1, and after fully wet grinding, carry out ultrasonic dispersion for 30min to obtain a platinum dioxide solution.

Disperse 0.515g of H ₂ IrCl ₆ into 5mL of a mixed solvent of ethanol and isopropanol at a volume ratio of 1:1, and stir to disperse evenly. Then, 0.00 mL, 0.25 mL, 1.00 mL, and 4.00 mL of the platinum dioxide solutions obtained above were added respectively to obtain platinum-iridium oxide alloys with different molar ratios. In addition, 5.00 mL, 7.25 mL, 14.00 mL and 41.00 mL of a mixed solvent of ethanol and isopropanol with a volume ratio of 1:1 were added respectively, so that the concentration of metal ions in the solution was 0.1 mol·L ^-1 . Then ultrasonically disperse for 30 min, add a few drops of 2 mol·L ^-1 NaOH to adjust the pH value of the solution to 14, carry out ultrasonic stirring alternately for 3 h to fully dissolve and disperse, and thus obtain a coating solution.

Put the prepared coating solution into a special container, uniformly cover the coating solution on the pretreated titanium plate by dipping and pulling method, the pulling speed is 2cm·min ^-1 ; then put it in a drying oven at 80°C Dry for 10 minutes until the surface coating solution is dried; then put it into the muffle furnace and bake it at 500°C for 10 minutes to produce an oxide coating on the surface; then take it out of the muffle furnace and cool it in the air . Such a cycle of coating, drying, sintering, and cooling is repeated 20 times. For the last time, the annealing time was 1 h, and platinum-iridium oxide alloy titanium anodes with different molar ratios were obtained.

Electrochemical tests were performed on the platinum-iridium oxide alloy titanium anodes obtained in Example 1 with different molar ratios. The method is as follows, carried out on the CHI700D electrochemical workstation, the electrolytic cell adopts a three-electrode system, the auxiliary electrode is a carbon paper electrode, the reference electrode is a reversible hydrogen reference electrode or a saturated calomel electrode, and the working electrode is a platinum-iridium oxide with different molar ratios. Alloy titanium anode (apparent area 1cm ² ). The oxygen evolution polarization curve was measured in 0.5mol·L ^-1 H ₂ SO ₄ solution at 25°C, and the chlorine evolution polarization curve of the electrode was measured in saturated NaCl solution (6mol·L ^-1 ). As shown in Table 1.

Table 1

It can be seen from Table 1 that when the platinum-iridium oxide alloy electrode is formed, its chlorine evolution activity is significantly improved, and its current density at 1.6V is 1.52, 2.18 and 1.86 times that of the iridium dioxide electrode, of which iridium platinum The chlorine evolution activity is the highest when the molar ratio is 1:1; while the chlorine evolution current density decreases with the increase of Pt content, indicating that the oxygen evolution activity decreases gradually, which is beneficial to improve the service life of the electrode.

In the self-made ionic membrane electrolyzer, the anode uses the platinum-iridium oxide alloy titanium anode (effective area 1 cm ² ) obtained in Example 1 with different molar ratios, and the cathode is a pure titanium plate. In the middle, a cation exchange membrane is used to divide the electrolytic cell into an anode area and a cathode area, each with a volume of 100 mL. during electrolysis. Add NaCl solution with a concentration of 1g·L ^-1 as the electrolyte, the current density is 100mA·cm ^-2 , the distance between the electrodes is 4cm, electrolysis is performed for 30min, and oxidized electrolyzed water is obtained in the anode area, and the available chlorine content, pH and oxidation potential are measured . As shown in table 2.

Table 2

As can be seen from Table 2, after the platinum-iridium oxide alloy is formed, the available chlorine content in the oxidized electrolyzed water obtained by its electrolysis is obviously higher than that of the iridium dioxide electrode, which is due to the improvement of their chlorine-analysis reaction activity, which is consistent with the results in Table 1 Consistent with each other, the available chlorine content is the largest when the molar ratio of platinum to iridium is 1:1. In addition, the change of platinum-iridium composition has little effect on the pH value and oxidation potential value of oxidized electrolyzed water obtained by electrolysis.

The field emission scanning electron microscope pictures of the platinum-iridium oxide alloy titanium anode with different ratios obtained in Example 1 are shown in Figure 1. Figure 1(a) is the SEM image of _IrO2 , which shows the characteristics of a typical oxide coating, showing obvious cracks, and fine crystal particles can be observed. Figure 1(b), Figure 1(c) and Figure 1(d) are the SEM images of platinum-iridium molar ratios of 1:4, 1:1 and 4:1, respectively. Different from the SEM image of IrO ₂ , the platinum-iridium oxide alloy has an obvious honeycomb shape, and no obvious cracks can be observed, which is beneficial to improve the service life of the electrode. When the content of iridium is high, obvious, a large number of fine crystal particles can be observed, which is beneficial to increase its electrocatalytic active area.

The X-ray diffraction patterns of the platinum-iridium oxide alloy titanium anode with different ratios obtained in Example 1 are shown in Figure 2. It can be seen from the figure that IrO ₂ is a typical rutile phase crystal _structure . Compared with the JCPDS 15-0870 standard card, its diffraction peaks at 27.8°, 34.7°, 53.9° and 66.6° are (110), ( 101), (211), (112) and other crystal plane characteristic peaks. And when IrO ₂ is mixed with PtO ₂ , after forming a solid solution, it has an obvious (101) crystal plane diffraction peak at 34.1°, which is a typical feature of rutile crystals. In addition, characteristic peaks of (002), (211) and (112) crystal planes can also be observed. The above characterization shows that since both IrO ₂ and PtO ₂ are rutile crystals with the same symmetry and similar lattice constants, they can form mixed crystals in a wide range of ratios.

Example 2

A 10cm×5cm TA1 titanium plate was first sandblasted, then washed with 10% sodium carbonate solution for 10 minutes under the action of ultrasonic waves to remove oil, then washed with deionized water under the action of ultrasonic waves, and then washed with 10wt% oxalic acid Activated at 96°C for 40min, finally rinsed with deionized water, dried in the air, and stored in absolute ethanol.

Dissolve 2.590g of H ₂ PtCl ₆ in 50mL of ethanol and isopropanol solvent with a volume ratio of 1:1, so that the metal ion concentration in the solution is 0.1mol·L ^-1 , and stir evenly. Then add 3.400 g of solid sodium nitrate to the solution, stir and heat to 60° C., and keep stirring until the solvent evaporates completely. The mixture was then completely dried in an oven at 80°C to obtain a dry salt mixture, which was thoroughly ground in an agate mortar to make it evenly mixed. Then, it was calcined in a tube furnace at 500°C for 30 minutes with a heating rate of 5°C·min ^-1 to obtain a mixture of salts. After cooling the mixture to room temperature, it was washed several times with excess deionized water to remove excess salt. Then add 5ml of a mixed solution of absolute ethanol and isopropanol with a volume ratio of 1:1, and after fully wet grinding, carry out ultrasonic dispersion for 30min to obtain a platinum dioxide solution.

Disperse 0.515g of H ₂ IrCl ₆ into 5mL of a mixed solvent of ethanol and isopropanol at a volume ratio of 1:1, and stir to disperse evenly. Then, 1.00 mL of the platinum dioxide solution obtained above was added to obtain a platinum-iridium oxide alloy with a molar ratio of 1:1. In addition, 14.00 mL of a mixed solvent of ethanol and isopropanol with a volume ratio of 1:1 was added to make the concentration of metal ions in the solution 0.1 mol·L ^-1 . Then ultrasonically disperse for 30 min, add a few drops of 2 mol·L ^-1 NaOH to adjust the pH value of the solution to 14, carry out ultrasonic stirring alternately for 3 h to fully dissolve and disperse, and thus obtain a coating solution.

Put the prepared coating solution into a special container, uniformly cover the coating solution on the pretreated titanium plate by dipping and pulling method, the pulling speed is 2cm·min ^-1 ; then put it in a drying oven at 80°C Dry for 10 minutes until the surface coating solution is dried; then put it into the muffle furnace and bake it at 400-700 ° C for 10 minutes to make the surface produce an oxide coating; then take it out of the muffle furnace and place it in the Cool in the air. Such a cycle of coating, drying, sintering, and cooling is repeated 20 times. For the last time, the annealing time was 1 h, and platinum-iridium oxide alloy titanium anodes under different heat treatment temperatures were obtained.

Electrochemical tests were performed on platinum-iridium oxide alloy titanium anodes with different firing temperatures. The method is as follows, carried out on the CHI700D electrochemical workstation, the electrolytic cell adopts a three-electrode system, the auxiliary electrode is a carbon paper electrode, the reference electrode is a reversible hydrogen reference electrode or a saturated calomel electrode, and the working electrode is a platinum-iridium oxide with different molar ratios. Alloy titanium anode (apparent area 1cm ² ). The oxygen evolution polarization curve was measured in 0.5mol·L ^-1 H ₂ SO ₄ solution at 25°C, and the chlorine evolution polarization curve of the electrode was measured in saturated NaCl solution (6mol·L ^-1 ). as shown in Table 3. It can be seen from Table 3 that the electrocatalytic activities of chlorine evolution and oxygen evolution of platinum-iridium oxide alloy electrodes obtained by heat treatment at different temperatures are different, and they first increase and then decrease with the increase of heat treatment temperature. This is because when the heat treatment temperature is low, as the heat treatment temperature increases, the crystal form of the electrode surface is more complete, so the electrocatalytic activity is improved; but when the heat treatment temperature is further increased, the electrode surface appears agglomeration and sintering, which greatly reduces the electrode surface. Electrocatalytic active area, so its chlorine and oxygen evolution current density decreases.

table 3

In the self-made ion-exchange membrane electrolyzer, the anode adopts platinum-iridium oxide alloy titanium anode (effective area 1cm ² ) with different firing temperatures, and the cathode is a pure titanium plate. In the middle, a cation exchange membrane is used to divide the electrolytic cell into an anode area and a cathode area, each with a volume of 100 mL. during electrolysis. Add NaCl solution with a concentration of 1g·L ^-1 as the electrolyte, the current density is 100mA·cm ^-2 , the distance between the electrodes is 4cm, electrolysis is performed for 30min, and oxidized electrolyzed water is obtained in the anode area, and the available chlorine content, pH and oxidation potential are measured . As shown in Table 4.

Table 4

It can be seen from Table 4 that the oxidized electrolyzed water is prepared by using platinum-iridium oxide alloy electrodes obtained at different heat treatment temperatures as anodes. The available chlorine content is the largest at ℃, which is consistent with the changes of chlorine and oxygen evolution currents in Table 3, indicating that the optimum preparation temperature is 500 ℃.

Example 3

A 10cm×5cm TA1 titanium plate was first sandblasted, then washed with 10% sodium carbonate solution for 10 minutes under the action of ultrasonic waves to remove oil, then washed with deionized water under the action of ultrasonic waves, and then washed with 10wt% oxalic acid Activated at 96°C for 40min, finally rinsed with deionized water, dried in the air, and stored in absolute ethanol.

Dissolve 2.590g of H ₂ PtCl ₆ in 25mL of ethanol and n-butanol solvent with a volume ratio of 1:1, so that the metal ion concentration in the solution is 0.2mol·L ^-1 , and stir evenly. Then add 3.400 g of solid sodium nitrate to the solution, stir and heat to 60° C., and keep stirring until the solvent evaporates completely. The mixture was then completely dried in an oven at 80°C to obtain a dry salt mixture, which was thoroughly ground in an agate mortar to make it evenly mixed. Then, it was calcined in a tube furnace at 500°C for 30 minutes with a heating rate of 5°C·min ^-1 to obtain a mixture of salts. After cooling the mixture to room temperature, it was washed several times with excess deionized water to remove excess salt. Then add 5ml of a mixed solution of absolute ethanol and isopropanol with a volume ratio of 1:1, and after fully wet grinding, carry out ultrasonic dispersion for 30min to obtain a platinum dioxide solution.

Disperse 0.515g of H ₂ IrCl ₆ into 5mL of a mixed solvent of ethanol and n-butanol at a volume ratio of 1:1, and stir to disperse evenly. Then, 1.00 mL of the platinum dioxide solution obtained above was added to obtain a platinum-iridium oxide alloy with a molar ratio of 1:1. In addition, 4.00 mL of a mixed solvent of ethanol and isopropanol with a volume ratio of 1:1 was added to make the concentration of metal ions in the solution 0.2 mol·L ^-1 . Then ultrasonically disperse for 30 min, add a few drops of 2mol·L ^-1 NaOH to adjust the pH value of the solution to 14, carry out ultrasonic stirring alternately for 6 h to fully dissolve and disperse, and thus obtain a coating solution.

Put the prepared coating solution into a special container, uniformly cover the coating solution on the pretreated titanium plate by dipping and pulling method, the pulling speed is 4cm·min ^-1 ; then put it in a drying oven at 80°C Dry for 10 minutes until the surface coating solution is dried; then put it into the muffle furnace and bake it at 500°C for 10 minutes to produce an oxide coating on the surface; then take it out of the muffle furnace and cool it in the air . Such a cycle of coating, drying, sintering, and cooling is repeated 20 times. For the last time, the annealing time is 1 h, and a platinum-iridium oxide alloy titanium anode is obtained. In the self-made ionic membrane electrolyzer, the electrode is used as an anode material (effective area 1cm ² ), and the cathode is a pure titanium plate. In the middle, a cation exchange membrane is used to divide the electrolytic cell into an anode area and a cathode area, each with a volume of 100 mL. during electrolysis. Add NaCl solution with a concentration of 1g·L ^-1 as the electrolyte, the current density is 100mA·cm ^-2 , the distance between the electrodes is 4cm, electrolyze for 30min, and the oxidized electrolyzed water is obtained in the anode area, and the available chlorine content is 162.46mg.L ^-1 , pH value is 2.21 and oxidation potential is 1170mV.

Example 4

A 10cm×5cm TA1 titanium plate was first sandblasted, then washed with 10% sodium carbonate solution for 10 minutes under the action of ultrasonic waves to remove oil, then washed with deionized water under the action of ultrasonic waves, and then washed with 10wt% oxalic acid Activated at 96°C for 40min, finally rinsed with deionized water, dried in the air, and stored in absolute ethanol.

Dissolve 2.430g of K ₂ PtCl ₆ in 25mL of ethanol and hydrochloric acid solvent with a volume ratio of 1:1, so that the metal ion concentration in the solution is 0.2mol·L ^-1 , and stir evenly. Then add 3.400 g of solid sodium nitrate to the solution, stir and heat to 60° C., and keep stirring until the solvent evaporates completely. The mixture was then completely dried in an oven at 80°C to obtain a dry salt mixture, which was thoroughly ground in an agate mortar to make it evenly mixed. Then it was calcined in a tube furnace at 500°C for 30min with a heating rate of 5°C·min- ¹ to obtain a mixture of salts. After cooling the mixture to room temperature, it was washed several times with excess deionized water to remove excess salt. Then add 5ml of a mixed solution of absolute ethanol and isopropanol with a volume ratio of 1:1, and after fully wet grinding, carry out ultrasonic dispersion for 30min to obtain a platinum dioxide solution.

Disperse 0.559g Na ₂ IrCl ₆ into 5mL of a mixed solvent of ethanol and isopropanol with a volume ratio of 1:1, and stir to disperse evenly. Then, 1.00 mL of the platinum dioxide nano-solution obtained above was added to obtain a platinum-iridium oxide alloy with a molar ratio of 1:1. In addition, 4.00 mL of a mixed solvent of ethanol and isopropanol with a volume ratio of 1:1 was added to make the concentration of metal ions in the solution 0.2 mol·L ^-1 . Then ultrasonically disperse for 30 min, add a few drops of 2mol·L ^-1 NaOH to adjust the pH value of the solution to 14, carry out ultrasonic stirring alternately for 6 h to fully dissolve and disperse, and thus obtain a coating solution.

Put the prepared coating solution into a special container, uniformly cover the coating solution on the pretreated titanium plate by dipping and pulling method, the pulling speed is 8cm·min ^-1 ; then put it in a drying oven at 80°C Dry for 20 minutes until the surface coating solution is dried; then put it into the muffle furnace and bake it at 500°C for 20 minutes to produce an oxide coating on the surface; then take it out of the muffle furnace and cool it in the air . Such a cycle of coating, drying, sintering, and cooling is repeated 20 times. For the last time, the annealing time is 1 h, and a platinum-iridium oxide alloy titanium anode is obtained. In the self-made ionic membrane electrolyzer, the electrode is used as an anode material (effective area 1cm ² ), and the cathode is a pure titanium plate. In the middle, a cation exchange membrane is used to divide the electrolytic cell into an anode area and a cathode area, each with a volume of 100 mL. during electrolysis. Add NaCl solution with a concentration of 1g·L ^-1 as the electrolyte, the current density is 100mA·cm ^-2 , the distance between the electrodes is 4cm, and the electrolysis takes 30min to obtain oxidized electrolyzed water in the anode area, and the available chlorine content is 169.04mg.L ^-1 , pH value is 2.25 and oxidation potential is 1163mV

Example 5

A 10cm×5cm TA1 titanium plate was first sandblasted, then washed with 10% sodium carbonate solution for 10 minutes under the action of ultrasonic waves to remove oil, then washed with deionized water under the action of ultrasonic waves, and then washed with 10wt% oxalic acid Activated at 96°C for 40min, finally rinsed with deionized water, dried in the air, and stored in absolute ethanol.

Dissolve 2.590g of H ₂ PtCl ₆ in 25mL of ethanol and isopropanol solvent with a volume ratio of 1:1, so that the metal ion concentration in the solution is 0.2mol·L ^-1 , and stir evenly. Then add 3.400 g of solid sodium nitrate to the solution, stir and heat to 60° C., and keep stirring until the solvent evaporates completely. The mixture was then completely dried in an oven at 80°C to obtain a dry salt mixture, which was thoroughly ground in an agate mortar to make it evenly mixed. Then, it was calcined in a tube furnace at 500°C for 30 minutes with a heating rate of 5°C·min ^-1 to obtain a mixture of salts. After cooling the mixture to room temperature, it was washed several times with excess deionized water to remove excess salt. Then add 5ml of a mixed solution of absolute ethanol and isopropanol with a volume ratio of 1:1, and after fully wet grinding, carry out ultrasonic dispersion for 30min to obtain a platinum dioxide solution.

Disperse 0.299g of _IrCl3 into 5mL of a mixed solvent of ethanol and isopropanol with a volume ratio of 1:1, and stir to disperse evenly. Then, 1.00 mL of the platinum dioxide solution obtained above was added to obtain a platinum-iridium oxide alloy with a molar ratio of 1:1. In addition, 4.00 mL of a mixed solvent of ethanol and isopropanol with a volume ratio of 1:1 was added to make the concentration of metal ions in the solution 0.2 mol·L ^-1 . Then ultrasonically disperse for 30 min, add a few drops of 2mol·L ^-1 NaOH to adjust the pH value of the solution to 14, carry out ultrasonic stirring alternately for 6 h to fully dissolve and disperse, and thus obtain a coating solution.

Put the prepared coating solution into a special container, uniformly cover the coating solution on the pretreated titanium plate by dipping and pulling method, the pulling speed is 5cm·min ^-1 ; then put it in a drying oven at 80°C Dry for 30 minutes until the surface coating solution is dried; then put it into the muffle furnace and bake it at 500°C for 20 minutes to produce an oxide coating on the surface; then take it out of the muffle furnace and cool it in the air . Such a cycle of coating, drying, sintering, and cooling is repeated 20 times. For the last time, the annealing time was 1h, and the platinum-iridium oxide alloy titanium anode was obtained, and the enhanced life test and electrolytic efficiency measurement were carried out.

Intensified experimental life test: 2cm×2cm Ti plate is used as cathode, 1cm×1cm Ir _0.5 Pt _0.5 O ₂ /Ti obtained in Example 5 and pure iridium dioxide obtained in Example 1 are used as anode respectively, and the electrolyte is 0.5mol· L ^-1 H ₂ SO ₄ , temperature 40°C, current density 2A·cm ^-2 .

Electrolysis efficiency measurement: the chloride ion content in the initial solution was 607mg·L ^-1 , the solution volume was 120mL, the current density was 100mA·cm ^-2 , the electrode area was 1cm ² , and the electrolysis time was 0.5h. The anode uses Ir _0.5 Pt _0.5 O ₂ /Ti obtained in Example 5 and pure iridium dioxide obtained in Example 1, respectively. The determination of chloride ion content after electrolysis adopts the potentiometric titration method, the working electrode is an Ag electrode, and the reference electrode is a double-salt bridge saturated calomel electrode. And the electrolysis efficiency was calculated by the remaining chloride ion content in the solution. The results are shown in Table 5.

table 5

It can be seen from Table 5 that the strengthening life of the platinum-iridium oxide alloy is 350h, which is 3.5 times that of the iridium dioxide electrode, indicating that the platinum-iridium oxide alloy electrode effectively improves the service life of the electrode and makes it more practical. Since the current density of oxidized electrolyzed water is only 0.1-0.2A·cm ^-2 in actual preparation, its actual service life is calculated according to the formula to be 8791h, which meets the requirements of the national standard GB-28234-2011. In addition, dilute sodium chloride solution was electrolyzed to prepare oxidized electrolyzed water, and the chloride ion content after electrolysis was measured and the electrolysis efficiency was calculated. As shown in Table 5, the residual chloride ion content was less than that of dioxide Iridium electrode, so its electrolysis efficiency is higher, and it is more suitable as an anode material for electrolysis of oxidized electrolyzed water.

Claims (8)

1. a preparation method of platinum-iridium oxide alloy electrode is characterized in that comprising the following steps: 1) heating and stirring the mixed solution of platinum salt and sodium nitrate at 55-65°C, evaporating and crystallizing, drying, grinding, and roasting to obtain the mixture, washing with water to remove impurities, then fully wet grinding, and dispersing in a solvent to obtain a platinum dioxide solution; 2) Disperse the iridium salt into the solvent, and then add the above-mentioned platinum dioxide solution so that the metal ion concentration is 0.05-0.3 mol·L ^-1 , adjust the pH value of the solution to 14 with sodium hydroxide, dissolve and disperse to obtain a coating solution ; 3) Uniformly coat the coating solution on the titanium plate, dry it, then bake it at 400-700°C, and cool it in the air; the process of coating, drying, roasting and cooling is cycled 5-20 times to obtain platinum Iridium oxide alloy electrode. 2. The preparation method of the platinum-iridium oxide alloy electrode as claimed in claim 1, wherein the platinum salt is H ₂ PtCl ₆ , K ₂ PtCl ₆ , Na ₂ PtCl ₆ , (NH ₄ ) ₂ PtCl ₆ , PtCl _4. Pt(NH ₃ ) ₂ (NO ₃ ) ₂ , PtCl ₂ (PhCN) ₂ or PtCl ₂ (P(C ₆ H ₅ ) ₃ ) ₂ . 3. The preparation method of the platinum-iridium oxide alloy electrode as claimed in claim 1, wherein the iridium salt is Na ₂ IrCl ₆ , K ₂ IrCl ₆ , H ₂ IrCl ₆ , IrCl ₃ , IrCl ₄ , IrI ₃ or Ir(OAC) ₃ . 4. The method for preparing a platinum-iridium oxide alloy electrode as claimed in claim 1, characterized in that the concentration of the metal ion of the platinum salt in the mixed solution in step 1) is 0.05-0.3mol L ^-1 , adding nitric acid The sodium concentration is 0.4-2.4 mol·L ^-1 . 5. the preparation method of platinum-iridium oxide alloy electrode as claimed in claim 1, is characterized in that step 1) and step 2) described solvent is any of ethanol, n-butanol, Virahol, hydrochloric acid solution, nitric acid solution One or a mix of both. 6. The preparation method of platinum-iridium oxide alloy electrode as claimed in claim 1, characterized in that the dissolution and dispersion process in step 2) is alternately ultrasonic treatment and stirring treatment, each 30min takes 3-10h. 7. The method for preparing a platinum-iridium oxide alloy electrode as claimed in claim 1, characterized in that the calcination temperature of step 1) and step 3) is 500°C. 8. The preparation method of platinum-iridium oxide alloy electrode as claimed in claim 1, characterized in that in step 2), the molar ratio of platinum to iridium is 1:1.