CN110468429B - Activation method of silver electrode - Google Patents

Abstract

The invention discloses a method for activating silver electrodes. The aqueous solution is the working electrode solution, and the alkali metal hydroxide aqueous solution is used as the counter electrode solution, and the oxidation reaction is carried out under the conditions of 0-50° C. and current density of 0.1-5A/dm ² , and then the current is reversed to carry out the reduction reaction; (2) the In step (1), the working electrode solution is replaced with an aqueous alkali metal hydroxide solution, and other conditions remain unchanged, and a redox reaction is carried out to obtain an activated silver electrode. The three-dimensional porous structure recast on the surface of the activated silver electrode of the invention has a larger surface area and a stable structure, which can greatly improve the dechlorination activity and stability of the silver electrode, and is beneficial to the dechlorination selectivity of dichloromethane and toxidine.

Description

A kind of activation method of silver electrode

(1) Technical field

The present invention relates to a method for activating a silver electrode.

(2) Background technology

The silver electrode has good electrocatalytic activity for the reductive dechlorination of chlorinated organic compounds, and this good electrocatalytic activity of the silver electrode requires periodic activation treatment to maintain. The activation treatment has two main purposes: (1) to remove the heterometals accumulated on the silver electrode surface during the reductive dechlorination process; (2) to recast the three-dimensional porous structure of the silver electrode surface that collapsed during the reductive dechlorination process.

The commonly used activation treatment processes are as follows: ① Place the silver electrode in an alkaline aqueous solution, first anodize the electrode to form colloidal silver oxide on the surface, and then reverse the polarity to completely reduce the electrode. To activate the effect, this process usually needs to be repeated several times. ② Put a small amount of silver salt (such as silver nitrate) into the alkaline aqueous solution, stir well to make the formed silver oxide particles evenly distributed on the electrode, and then energize to completely reduce the silver oxide particles. ③ Immerse the silver electrode in an alkaline aqueous solution containing an oxidant, so that silver oxide is formed on the surface of the silver electrode, and then electrify to completely reduce the oxide layer on the silver electrode. These three methods are disclosed in US4217185, US4242183 and EP0252520A1, respectively. In fact, these three methods are essentially the same, in which a rough silver oxide layer is first formed on the electrode surface, and then the silver oxide layer is completely reduced, so that a three-dimensional porous structure with good electrocatalytic activity is formed on the surface of the silver electrode. Therefore, the electrocatalytic activities of the active silver electrodes prepared by the above three methods for the reductive dechlorination of chlorinated organic compounds are similar. The disadvantages of such methods are: the low removal rate of heterometals accumulated on the silver electrode surface during reductive dechlorination and the low surface area of the recast three-dimensional porous structure on the silver electrode surface.

US 7666293 and US 8685222 disclose methods for electrochemical redox activation of silver electrodes in alkaline aqueous solutions containing halide ions. The method produces silver halide instead of silver oxide during the oxidation process of silver, and then the silver halide is reduced to elemental silver in the reduction process. The activated silver obtained by this method has a large specific surface area, so that the silver electrode has better catalytic activity for the reductive dechlorination of chlorinated organic compounds. This type of method solves the problem of low surface area of the recast three-dimensional porous structure on the surface of the silver electrode, but also has the problems of low removal rate of miscellaneous metals accumulated on the surface of the silver electrode during the reductive dechlorination process and the easy collapse of the recast three-dimensional porous structure.

(3) Contents of the invention

The purpose of the present invention is to provide a method for activating a silver electrode. First, redox treatment is performed on the silver electrode in an aqueous hydrochloric acid solution, and then further redox treatment is performed on the silver electrode in an aqueous alkali metal hydroxide solution. Cleaner surfaces, more stable three-dimensional structures, and longer-lasting dechlorination activity.

The technical scheme adopted in the present invention is:

The invention provides a method for activating a silver electrode. The method comprises the following steps: (1) acid solution redox: a diaphragm electrolytic cell is used, platinum is used as a counter electrode, silver is used as a working electrode, and silver/silver chloride is used as a reference Electrode, with hydrochloric acid aqueous solution as working electrode solution (deionized water configuration), alkali metal hydroxide aqueous solution (deionized water configuration) as counter electrode solution, under the conditions of 0-50 ℃, current density ^0.1-5A /dm2 Carry out the oxidation reaction until the electrode potential is ≥+0.3V vs. SHE (relative to the standard hydrogen electrode potential), and then reverse the current to perform reduction treatment on the working electrode until the electrode potential reaches ≤-0.3V vs. SHE; (2) Alkaline solution redox : In step (1), the working electrode liquid is replaced with an aqueous alkali metal hydroxide solution (deionized water configuration), other conditions remain unchanged, and the oxidation treatment is carried out under the conditions of 0-50 ° C and a current density of 0.1-5 A/dm ² until The electrode potential reaches ≥+0.6Vvs.SHE; then the current is reversed to reduce the working electrode until the electrode potential reaches ≤-0.4Vvs.SHE to obtain an activated silver electrode.

Further, the mass content of silver in the silver electrode in step (1) is not less than 99%, preferably not less than 99.9%. The mass concentration of the hydrochloric acid aqueous solution is 5-35wt%, preferably 10-20wt%. The concentration of the alkali metal hydroxide aqueous solution is 0.1-2 mol/L, preferably 0.5-1 mol/L.

Further, the alkali metal in the aqueous alkali metal hydroxide solution in steps (1) and (2) is one of the following: LiOH, NaOH, KOH, NH ₄ OH, and in the steps (1) and (2) The alkali metals may be the same or different. The aqueous solution is formulated with deionized water.

Further, in step (1), the oxidation reaction is performed until the electrode potential reaches +0.7～+1.0V vs. SHE; the reduction reaction is performed until the electrode potential reaches -0.3～-0.7V vs. SHE, preferably -0.4～-0.6V vs. SHE.

Further, the current density in step (1) is preferably 0.3-1 A/dm ² , more preferably 0.5-1 A/dm ² .

Further, the redox temperature in step (1) is preferably 20-30°C.

Further, step (1) redox is repeated 1-2 times.

Further, in step (2), the oxidation reaction is performed until the electrode potential reaches +0.6～+1.3V vs. SHE, preferably +1.0～+1.3V vs. SHE; the reduction reaction is performed until the electrode potential reaches -0.4～-1.3V vs. SHE, preferably -1.0～-1.3Vvs.SHE.

Further, the current density in step (2) is preferably 0.3-1 A/dm ² , more preferably 0.5-1 A/dm ² .

Further, the redox temperature in step (2) is preferably 20-30°C.

Further, step (2) redox is repeated 1-2 times.

The activated silver electrode of the invention can realize the efficient dechlorination of dichloromethane into methane, and the highly selective dechlorination of toxidine (I) to prepare 4-amino-3,6-dichloropicolinic acid (molecular formula II).

The method for efficiently dechlorinating dichloromethane into methane by the activated silver electrode of the present invention is as follows: in a non-diaphragm electrolytic cell sealed with an air bag, the silver electrode is used as a cathode, and a magnesium plate, an aluminum plate or a zinc plate is used as an anode; Tetrabutylammonium perchlorate or tetrabutylammonium tetrafluoroborate is used as supporting electrolyte; acetic acid or water is used as proton donor; acetonitrile or DMF is used as solvent; dichloromethane is used as raw material. Under normal temperature and pressure, a certain amount of electricity is introduced, and the electrolysis is stopped when the amount of electricity is sufficient. The conversion of dichloromethane and the yield of methane were determined by gas chromatography. More preferably, the activated silver electrode is used as the cathode, and the magnesium plate with the same area is used as the anode; the acetonitrile solution of 0.1mol/L tetrabutylammonium perchlorate+5wt% acetic acid+20mmol/L dichloromethane is the electrolyte, and the electrolyte is at 25 At -30°C, a current of 1A/dm ² was passed through, and the electrolysis was stopped after 4 hours of reaction to obtain a reaction solution containing methane.

The method for preparing 4-amino-3,6-dichloropicolinic acid (II) by the activated silver electrode of the present invention for the highly selective dechlorination of toxidine (I) is as follows: in an H-type cationic membrane electrolytic cell, using The silver electrode is the cathode, and the platinum sheet of the same area is the anode; the aqueous solution of NaOH is the anolyte, and the aqueous solution with NaOH and toxidine dissolved is the catholyte. Under normal temperature and pressure, a certain amount of electricity is introduced, and the electrolysis is stopped when the amount of electricity is sufficient. Determination of the conversion rate of toxidine and the yield of 4-amino-3,6-dichloropicolinic acid by high performance liquid chromatography, more preferably in an H-type cationic membrane electrolytic cell, with a silver electrode as the cathode, the same area of The platinum sheet is the anode; the 2.0mol/L NaOH aqueous solution is the anolyte (prepared with deionized water), and the aqueous solution of 0.4mol/L NaOH+0.4mol/L dextromethorphan (prepared with deionized water) is the catholyte. At 25-30°C, a current of 5A/dm ² was passed, and after 8 hours of reaction, a reaction solution containing 4-amino-3,6-dichloropicolinic acid was obtained.

The activation method of the silver electrode can be used for the initial activation of the newly made bright silver electrode, and also can be used for the reactivation of the silver electrode whose activity is reduced after the dechlorination reaction. The above two redox processes can be carried out one or more times respectively. For the initial activation of the bright silver electrode, it is preferable to carry out the redox process twice in the hydrochloric acid aqueous solution, and the redox process in the aqueous solution containing alkali metal hydroxide once; The redox process in the aqueous solution was carried out once, and the redox process in the aqueous solution containing the alkali metal hydroxide was carried out once.

Compared with the prior art, the beneficial effects of the present invention are mainly reflected in: (1) the surface area of the three-dimensional porous structure recast on the surface of the silver electrode is larger (the roughness is increased from 55cm ² /cm ² to 74cm ² /cm ² ), the structure is stable (After 40 hours of use, the roughness increased from 38cm ² /cm ² to 71cm ² /cm ² ), which can greatly improve the dechlorination activity of the silver electrode (for the dechlorination reaction of dichloromethane, the recovery of methane in the first reaction (2) the silver electrode surface is in the process of reductive dechlorination during the dechlorination reaction of dichloromethane, the yield of methane increased from 74% to 91% in the fifth reaction. The removal rate of heterometals accumulated in the process is high, which is beneficial to the dechlorination selectivity of dichloromethane and doxidine (in the first use of the activated silver electrode, the selectivity of dichloromethane dechlorination to methane increased from 93% to 100%). 98%; the selectivity of the dechlorination of doxidine to 4-amino-3,6-dichloropicolinic acid rose from 91% to 97%).

(4) Description of drawings

Fig. 1 Schematic diagram of an H-type electrolytic cell with Nafion 117 cation membrane as a diaphragm, the distance between the cathode and anode is about 8cm, the ion membrane is placed in the center, and the area of the ion membrane is 3.14×2×2=12.56cm ² .

Figure 2. Sealed non-membrane cell with gas bag (cathode-anode distance 2 cm).

(5) Specific implementation manner

The present invention is further described below in conjunction with specific embodiment, but the protection scope of the present invention is not limited to this:

All aqueous solutions in the examples of the present invention were prepared with deionized water.

Example 1: Activation method of bright silver electrode

(1) Acid solution redox: In an H-type cationic membrane electrolytic cell with Nafion 117 cationic membrane (as shown in Figure 1), bright silver flakes (purity of 99.9wt%, size of 0.1cm×2.0cm×2.0cm) ) is the working electrode; the platinum sheet of the same area is the counter electrode; silver/silver chloride is the reference electrode. The working electrode chamber is a 10 wt% hydrochloric acid aqueous solution (referred to as 1# electrolyte), and the counter electrode chamber is a 1.0 mol/L sodium hydroxide aqueous solution. The temperature of the aqueous hydrochloric acid solution was controlled to be 20-25°C, and an anodic oxidation current with a current density of 0.5A/dm was first applied to the silver electrode until the electrode potential reached ⁺ 0.7vs.SHE; As the working electrode), a cathodic reduction current with a current density of 0.5 A/dm ² was applied to the silver electrode until the electrode potential reached -0.4 vs. SHE. After completion, the above redox process was repeated once.

(2) Redox of alkaline solution: replace the working electrode chamber solution of step (1) with a 1.0mol/L sodium hydroxide aqueous solution (denoted as 2# electrolyte), the counter electrode chamber remains unchanged, the silver sheet is the working electrode, and the platinum The sheet is the counter electrode, and the temperature of the working electrode chamber is controlled to be 20-25°C. First, an anodizing current with a current density of 0.5A/dm ² is applied to the silver electrode until the electrode potential reaches +1.0vs.SHE; then the current is reversed to apply a current to the silver electrode. Cathodic reduction current at a density of 0.5 A/dm ² until the electrode potential reaches -1.0 vs. SHE. Remove the silver electrode and place it in deionization for later use. The roughness of the silver electrode was measured by using the anodic stripping method of the lead underpotential deposition layer (for the specific method, refer to the literature: Journal of Electroanalytical Chemistry 664 (2012) 39-45), and the roughness was: 74 cm ² /cm ² .

Example 2-7

According to the method of Example 1, the 1# electrolyte and 2# electrolyte, redox current density, redox cut-off potential and reaction temperature in Example 1 were changed to those described in Table 1, and the prepared activated silver roughness was shown in Table 1 .

Table 1 Experimental parameters and roughness of activated silver electrode

Comparative Example 1: Activation method of bright silver electrode

In the H-type cationic membrane electrolytic cell with Nafion 117 cationic membrane (Figure 1), bright silver flakes (purity of 99.9wt%, size of 0.1cm×2.0cm×2.0cm) were used as working electrodes; platinum flakes with the same area were Counter electrode; silver/silver chloride as reference electrode. The working electrode chamber is 0.5mol/L sodium chloride+0.5mol/L sodium hydroxide aqueous solution, and the counter electrode chamber is 1.0mol/L sodium hydroxide aqueous solution. The temperature of the aqueous solution in the working electrode chamber is controlled to be 20-25°C. First, an anodic oxidation current of 0.5A/dm ² is applied to the silver electrode until the electrode potential reaches +0.8vs.SHE; then the silver sheet is used as the counter electrode and the platinum sheet is used as the work. Electrode, a cathodic reduction current of 0.5 A/dm ² was applied to the silver electrode until the electrode potential reached -0.4 vs. SHE. After completion, the above redox process was repeated once. Remove the silver electrode and place it in deionization for later use. The roughness of the silver electrode was measured by using the anodic stripping method of the lead underpotential deposition layer (for the specific method, refer to the literature: Journal of Electroanalytical Chemistry 664 (2012) 39-45), and the roughness was 55 dm ² /cm ² .

Comparative Example 2: Activation method of bright silver electrode

In a non-diaphragm electrolytic cell (100mL beaker), a bright silver sheet (purity of 99.9wt%, size of 0.1cm×2.0cm×2.0cm) is the working electrode; the platinum sheet of the same area is the counter electrode; silver/silver chloride as the reference electrode. A 1.0 mol/L sodium hydroxide aqueous solution is the electrolyte. The temperature of the electrolyte is controlled to be 20-25°C. First, an anodic oxidation current of 0.5A/dm ² is applied to the silver electrode until the electrode potential reaches +1.0vs.SHE; then the silver electrode is used as the counter electrode, and the platinum sheet is used as the working electrode. A cathodic reduction current of 0.5 A/dm ² was applied to the silver electrodes until the electrode potential reached -1.0 vs. SHE. After completion, the above redox process was repeated once. Remove the silver electrode and place it in deionization for later use. The anodic stripping method of lead underpotential deposition layer was used (for the specific method, refer to the literature: Journal of Electroanalytical Chemistry 664 (2012) 39-45) to measure the roughness of the silver electrode, and the roughness was: 21 dm ² /cm ² .

Example 8: Electrochemical dechlorination of dichloromethane (silver electrode is not activated in the middle of batch reaction)

In a sealed non-diaphragm electrolytic cell with an air bag (as shown in Figure 2), the activated silver electrode (geometric size of 0.1 cm × 2.0 cm × 2.0 cm, and purity of 99.9 wt %) prepared by the method described in Example 1 is: Cathode, a magnesium plate with the same area (geometric size of 0.3cm×2.0cm×2.0cm) is the anode; 50mL of acetonitrile solution containing 0.1mol/L tetrabutylammonium perchlorate+5wt% acetic acid+20mmol/L dichloromethane for the electrolyte. At 25-30 °C, a current of 1A/dm ² was passed in, and the electrolysis was stopped after 4 hours of reaction. The methane yield was determined by gas chromatography: 98%; the conversion of dichloromethane was 100%.

After repeating the above-mentioned electrochemical dechlorination process of dichloromethane for 5 times, the roughness of the activated silver electrode after the fifth dechlorination was determined to be 72 dm ² /cm ² . The methane yield in the fifth electrolysis experiment using activated silver was measured by gas chromatography: 91%; the conversion of dichloromethane was 96%.

Gas chromatographic analysis conditions are: HP-INNOWAX (30m x 320μm x 0.25μm) as the separation column; the detector is FID; the hydrogen flow rate is 25mL/min; the oven temperature is 36°C; The inlet heater temperature was 250°C, and the next-wall purge flow was 3mL/min. The detector heating temperature was 250°C, the air flow was 400mL/min, and the makeup flow was 30mL/min.

Comparative Example 3 (Comparative Example 8): Electrochemical dechlorination of dichloromethane (silver electrode is not activated in the middle of batch reaction)

In the sealed non-diaphragm electrolytic cell with air bag (as shown in Figure 2), the activated silver electrode prepared by the method described in Comparative Example 1 (geometric size of 0.1 cm × 2.0 cm × 2.0 cm, purity of 99.9 wt %) is: Cathode, a magnesium plate with the same area (geometric size of 0.3cm×2.0cm×2.0cm) is the anode; 50mL of acetonitrile solution containing 0.1mol/L tetrabutylammonium perchlorate+5wt% acetic acid+20mmol/L dichloromethane for the electrolyte. At 25-30 °C, a current of 1A/dm ² was passed in, and the electrolysis was stopped after 4 hours of reaction. The methane yield was determined by gas chromatography: 93%; the conversion of dichloromethane was 100%. Compared with Example 8, when the activated silver electrode prepared by the method described in Comparative Example 1 was used as the cathode, the methane yield decreased by 5%.

After repeating the above-mentioned electrochemical dechlorination process of dichloromethane for 5 times, the roughness of the activated silver electrode was determined to be 35 dm ² /cm ² . The methane yield in the fifth electrolysis experiment using activated silver was measured by gas chromatography: 74%; the conversion of dichloromethane was 88%. In Comparative Example 8, when the activated silver electrode prepared by the method described in Comparative Example 1 was used continuously as a cathode for the fifth time, the methane yield decreased by 17%, the dichloromethane conversion rate decreased by 8%, and the roughness of the activated silver electrode decreased. 27dm ² /cm ² .

Example 9: Electrochemical Dechlorination of Toxidine (Silver Electrode Not Activated During Batch Reaction)

In the H-type cationic membrane electrolytic cell with Nafion 117 cationic membrane (Fig. 1), the activated silver electrode prepared by the method described in Example 1 (geometric size of 0.1 cm × 2.0 cm × 2.0 cm, purity of 99.9 wt%) It is the cathode, the platinum sheet of the same area (geometric size is 0.1cm×2.0cm×2.0cm) is the anode; 50mL containing 2.0mol/L NaOH aqueous solution is the anolyte, 50mL containing 0.4mol/L NaOH+0.4mol/L Duxiu The defined aqueous solution (prepared with deionized water) is the catholyte. At 25-30°C, a current of 5A/dm ² was passed through, and after 8 hours of reaction, the yield of 4-amino-3,6-dichloropicolinic acid was determined by high performance liquid chromatography: 92%; the conversion of toxidine The rate is 95%.

After repeating the above-mentioned electrochemical dechlorination process of Duxiudine for 5 times, the roughness of the activated silver electrode after the fifth dechlorination was determined to be 71 dm ² /cm ² . The yield of 4-amino-3,6-dichloropicolinic acid in the fifth electrolysis experiment using activated silver was measured by high performance liquid chromatography: 82%.

The high-performance liquid chromatography measurement conditions are as follows: C18 symmetrical column (250mm length_4.6mm i.d., 5mm particle size) is the separation column; acetonitrile/methanol/water (volume ratio 1:3:6) mixed solution containing 30mM phosphoric acid is the mobile phase ; The flow rate is: 1mL/Min; The detection wavelength is 230nm; Waters 2996 PDA is the detector.

Comparative Example 4 (Comparative Example 9): Electrochemical Dechlorination of Toxidine (Silver Electrode Not Activated in the Middle of Batch Reaction)

In the H-type cationic membrane electrolytic cell with Nafion 117 cationic membrane (Fig. 1), the activated silver electrode prepared by the method described in Comparative Example 1 (geometric size of 0.1 cm × 2.0 cm × 2.0 cm, purity of 99.9 wt%) It is the cathode, the platinum sheet of the same area (geometric size is 0.1cm×2.0cm×2.0cm) is the anode; 50mL of the aqueous solution containing 2.0mol/L NaOH is the anolyte, and 50mL contains 0.4mol/L NaOH+0.4mol/L poison The aqueous solution of Xiuding (prepared with deionized water) is the catholyte. At 25-30 °C, a current of 5A/dm ² was passed through, and the yield of 4-amino-3,6-dichloropicolinic acid was determined by high performance liquid chromatography after 8 hours of reaction: 85%; the conversion of toxidine The rate is 93%. In comparison with Example 9, when the activated silver electrode prepared by the method described in Comparative Example 1 was used as a cathode, the yield decreased by 7%, and the conversion rate decreased by 2%.

After repeating the above-mentioned electrochemical dechlorination process of Duxiudine for 5 times, the measured roughness of the activated silver electrodes were respectively: 38 dm ² /cm ² . The yields of 4-amino-3,6-dichloropicolinic acid in the fifth electrolysis experiment using activated silver were determined by high performance liquid chromatography: 73%, respectively. In Comparative Example 9, when the activated silver electrode prepared by the method described in Comparative Example 1 was used continuously as a cathode for the fifth time, the roughness of the activated silver electrode decreased by 33 dm ² /cm ² , and the yield decreased by 9%.

Example 10: Electrochemical Dechlorination of Duxiudine (Intermediate Activation of Silver Electrodes in Batch Reactions)

In the H-type cationic membrane electrolytic cell with Nafion 117 cationic membrane (Fig. 1), the activated silver electrode prepared by the method described in Example 1 (geometric size of 0.1 cm × 2.0 cm × 2.0 cm, purity of 99.9 wt%) It is the cathode, the platinum sheet of the same area (geometrical size is 0.1cm×2.0cm×2.0cm) is the anode; 50mL of the aqueous solution containing 2.0mol/L NaOH is the anolyte, and 50mL contains 0.4mol/L NaOH+0.4mol/L poison The aqueous solution of Xiuding (prepared with deionized water) is the catholyte. At 25-30° C., a current of 5A/dm ² was introduced, and the yield of 4-amino-3,6-dichloropicolinic acid was determined by high performance liquid chromatography after 8 hours of reaction: 93%.

After repeating the above-mentioned electrochemical dechlorination process of toxidine for 5 times (the corresponding silver electrode was activated by the method described in Example 1 before each dechlorination experiment), the measured roughness of the activated silver electrode was: 71 dm ² /cm ² . The yield of 4-amino-3,6-dichloropicolinic acid in the fifth electrolysis experiment using activated silver was measured by high performance liquid chromatography: 93%.

Comparative Example 5 (Comparative Example 10): Electrochemical Dechlorination of Toxidine (Batch Reaction Intermediate Activated Silver Electrode)

In the H-type cationic membrane electrolytic cell with Nafion 117 cationic membrane (Fig. 1), the activated silver electrode prepared by the method described in Comparative Example 1 (geometric size of 0.1 cm × 2.0 cm × 2.0 cm, purity of 99.9 wt%) It is the cathode, the platinum sheet of the same area (geometric size is 0.1cm×2.0cm×2.0cm) is the anode; 50mL of the aqueous solution containing 2.0mol/L NaOH is the anolyte, and 50mL contains 0.4mol/L NaOH+0.4mol/L poison The aqueous solution of Xiuding (prepared with deionized water) is the catholyte. At 25-30° C., a current of 5A/dm ² was introduced, and the yield of 4-amino-3,6-dichloropicolinic acid was determined by high performance liquid chromatography after 8 hours of reaction: 83%. Comparing Example 10, when the activated silver electrode prepared by the method described in Comparative Example 1 was used as a cathode, the yield decreased by 10%.

Repeat the above-mentioned electrochemical dechlorination process of toxidine for 5 times (the corresponding silver electrode was activated by the method described in Comparative Example 1 before each dechlorination experiment), and the roughness of the activated silver electrode was determined to be 50 dm ² /cm ² , respectively. The yield of 4-amino-3,6-dichloropicolinic acid in the fifth electrolysis experiment using activated silver was measured by high performance liquid chromatography: 79%. In Comparative Example 10, when the activated silver electrode prepared by the method described in Comparative Example 1 was used continuously as a cathode for the fifth time, the roughness of the activated silver electrode decreased by 21 dm ² /cm ² , and the yield decreased by 14%.

Claims (10)

1. A method for activating a silver electrode, characterized in that the method is: (1) acid solution redox: a diaphragm electrolytic cell is used, platinum is used as a counter electrode, silver is used as a working electrode, and silver/silver chloride is used as a The reference electrode uses hydrochloric acid aqueous solution as the working electrode solution and alkali metal hydroxide aqueous solution as the counter electrode solution. The oxidation reaction is carried out under the conditions of 0-50°C and current density of 0.1-5A/dm ² to the electrode potential ≥+ 0.3 Vvs . SHE, then reverse the current, and perform a reduction reaction on the working electrode until the electrode potential reaches ≤- 0.3 Vvs. SHE; (2) Alkaline solution redox: Replace the working electrode solution in step (1) with an aqueous alkali metal hydroxide solution, With alkali metal hydroxide aqueous solution as the counter electrode solution, platinum as the counter electrode, silver as the working electrode, the oxidation reaction is carried out under the conditions of 0-50 ℃ and current density of 0.1-5 A/dm ² until the electrode potential reaches ≥+ 0.6 Vvs. SHE; then the current was reversed, and the working electrode was subjected to a reduction reaction until the electrode potential reached ≤- 0.4 Vvs. SHE to obtain an activated silver electrode. 2 . The method of claim 1 , wherein the mass content of silver in the silver electrode in step (1) is not less than 99%. 3 . 3 . The method according to claim 1 , wherein the mass concentration of the hydrochloric acid aqueous solution in step (1) is 5-35 wt %; the concentration of the alkali metal hydroxide aqueous solution is 0.1-2 mol/L. 4 . 4 . The method of claim 1 , wherein the alkali metal in the aqueous alkali metal hydroxide solution in steps (1) and (2) is one of the following: LiOH, NaOH, and KOH. 5 . 5. The method of claim 1, characterized in that in step (1), the oxidation reaction is performed until the electrode potential reaches + 0.7~+ 1.0 V vs. SHE; the reduction reaction is performed until the electrode potential reaches - 0.3~-0.7 V vs. SHE . 6 . The method of claim 1 , wherein in step (1), the current density is 0.3-1 A/dm ² , and the redox temperature is 20-30°C. 7 . 7 . The method of claim 1 , wherein the redox steps of step (1) and step (2) are repeated 1-2 times. 8 . 8. The method of claim 1, characterized in that in step (2) the oxidation reaction is performed until the electrode potential reaches + 0.6~+1.3 V vs. SHE, and the reduction reaction is performed until the electrode potential reaches - 0.4~- 1.3 V vs. SHE. 9 . The method according to claim 1 , wherein the current density in step (2) is all 0.3-1 A/dm ² , and the redox temperature is all 20-30°C. 10 . 10. The method of claim 1, wherein the aqueous solutions are prepared with deionized water.

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