CN108217852B

CN108217852B - Lead dioxide electrode used as anode in electrocatalytic sewage treatment and preparation method thereof

Info

Publication number: CN108217852B
Application number: CN201810025550.7A
Authority: CN
Inventors: 黎学明; 满帅帅; 包河彬; 杨海峰; 曾韬; 陈金; 熊林利; 罗晓玉
Original assignee: Chongqing University
Current assignee: Chongqing University
Priority date: 2018-01-11
Filing date: 2018-01-11
Publication date: 2020-09-25
Anticipated expiration: 2038-01-11
Also published as: CN108217852A

Abstract

Lead dioxide electrode with long service life and high catalytic activity, and SnO₂‑Sb₂O₃As a bottom layer, α -PbO₂As an intermediate layer, and β -PbO₂Prepared as a surface active layer. The lead dioxide obtained by the method is compact and uniform, has small particles and has large specific surface area. Meanwhile, the surface active layer has strong adhesive force and is not easy to fall off; the surface is smooth and firm, can resist acid and alkali corrosion, and has good catalytic activity and service life. In addition, the method has the advantages of simple process conditions, low cost and stable performance of the obtained product, is suitable for industrial production, can be widely applied to the field of sewage treatment by an electrocatalytic oxidation technology, and has a far-reaching market prospect.

Description

Lead dioxide electrode used as anode in electrocatalytic sewage treatment and preparation method thereof

Technical Field

The invention relates to a lead dioxide electrode which can be used as an anode for electrocatalytic sewage treatment.

Background

The problem of sewage treatment has been the focus of research. With the development of industrial technology, the amount of polluted waste water discharged from industry is increasing day by day, which makes water resources, which are otherwise in short supply, more tense. Most of these pollutants are organic pollutants which, when discharged into water, can cause damage to the ecological environment. Among a plurality of sewage treatment technologies, the electrocatalytic oxidation method has low requirements on equipment, high treatment speed, simple and convenient operation, cleanness, no pollution and easy large-scale application, and is an environment-friendly technology. Has been paid extensive attention in recent years, and is an important development direction in the field of sewage treatment in the future. The nature of the anode electrode material has a critical influence on the efficiency of the electrocatalytic oxidation process.

The titanium-based dimensionally stable electrode is a metal oxide with catalytic activity prepared on a titanium substrate in a thermal deposition or electrodeposition mode, has good catalytic activity, is corrosion-resistant, simple to prepare and good in chemical stability, and is widely applied to an electrochemical oxidation technology. The lead dioxide electrode is simple to prepare, low in cost and good in conductivity, so that the lead dioxide electrode has a good application prospect in the field of electrocatalytic oxidation.

PbO₂Electrodes, while having numerous advantages, also face several problems. Such as PbO₂The coating has large internal stress inside, and nascent oxygen generated in the electrolytic process is easy to diffuse to the substrate through the surface layer, so that the substrate is passivated, the coating falls off, the electrochemical stability of the electrode is reduced, and the service life of the electrode is prolonged. Therefore, the electrode has important significance in ensuring the catalytic activity of the electrode and simultaneously having longer service life.

Disclosure of Invention

An object of the present invention is to provide a method for preparing a lead dioxide electrode, which can effectively improve the service life of the electrode without reducing the catalytic activity.

The preparation method of the lead dioxide electrode comprises the following steps:

providing a titanium substrate, polishing, degreasing, cleaning, and placing in absolute ethyl alcohol for later use;

taking out the titanium substrate and drying, and brushing a bottom layer on the titanium substrate by using coating liquid, wherein the coating liquid comprises the following components: 3-25 mL of n-butyl alcohol, 0.1-8 mL of concentrated hydrochloric acid, 0.5-10 g of stannic chloride pentahydrate and 0.1-8 g of antimony trichloride;

repeatedly brushing the bottom layer for 5-10 times, drying after each brushing, and finally roasting for 2-4h under the conditions of 450-500 ℃;

preparation of α -PbO on the bottom layer by electrodeposition₂An intermediate layer having a current density of 5mA/cm²～65mA/cm^2,The total electrodeposition time is 1-2 h, the electrodeposition temperature is 30-80 ℃, the electrode spacing is 2cm, and the electrodeposition solution comprises 0.1-1 mol/L of PbO and 1-10 mol/L of NaOH; and

continuing the electrodeposition method at α -PbO₂Preparation of β -PbO on the intermediate layer₂A surface active layer having a current density of 20mA/cm²～85mA/cm²The total electrodeposition time is 1-2 h, the electrodeposition temperature is 25-100 ℃, the electrode spacing is 2cm, and the electrodeposition solution comprises 0.1-1 mol/L Pb (NO3)2, 0.05-2 mol/L HBO3, 0.5-2 g/L NaF, 10-100 mg/L Graphene Oxide (GO) and 10-100 mg/L nano SiC.

The method takes lead nitrate, boric acid, sodium fluoride, graphene and nano silicon carbide as components of the surface active layer electrodeposition liquid, and takes SnO₂-Sb₂O₃As a bottom layer, α -PbO₂As the intermediate layer, a uniform and compact lead dioxide electrode is prepared by a specific method.

The cathode used in the electrodeposition of the intermediate layer and the surface active layer can be selected from a graphite sheet, a copper sheet, a titanium sheet, a stainless steel sheet and a platinum sheet, the anode can be a titanium sheet or a titanium net, the cathode and the anode plates can be made of different or same materials, and the size of the cathode and the anode plates is preferably 1 × 4cm²。

Degreasing cleaning of the titanium substrate may include: ultrasonic cleaning in acetone, ethanol and deionized water for 5-15 min.

According to a preferred embodiment of the invention, the mass ratio of tin tetrachloride to antimony trichloride in the coating solution is 10: 1. this primer layer has excellent bonding properties and can be passed through α -PbO₂The intermediate layer improves the bonding force with the surface active layer and alleviates the generation of electrodeposition distortion.

The invention also provides the lead dioxide electrode prepared by the method. The lead dioxide electrode can be used as an anode in electrocatalytic sewage treatment.

In a preferred embodiment of the invention, the doping amount of the graphene oxide is 20-60 mg/L, and the doping amount of the nano silicon carbide is 10-50 mg/L. The purpose of doping the nano silicon carbide and the graphene oxide is to promote the two to generate a synergistic effect, and the electrode life of the lead dioxide is prolonged while filling the internal vacancy of the lead dioxide, controlling the appearance of the lead dioxide and ensuring the catalytic activity.

The invention not only improves the service life of the lead dioxide electrode, but also does not reduce the catalytic activity of the electrode.

In addition, the invention also achieves the purpose of controlling the appearance of the lead dioxide by adding two substances of nano silicon carbide and graphene oxide and controlling the mixing proportion of the two substances. The obtained lead dioxide is compact and uniform, has small particles and has larger specific surface area. Meanwhile, the surface active layer has strong adhesive force and is not easy to fall off. The surface is smooth and firm, can resist acid and alkali corrosion, and has good catalytic activity and service life.

In addition, the method has the advantages of simple process conditions, low cost and stable performance of the obtained product, is suitable for industrial production, can be widely applied to the field of sewage treatment by an electrocatalytic oxidation technology, and has a far-reaching market prospect.

Drawings

FIG. 1 is a scanning electron micrograph of an underlayer made by a coating pyrolysis process on a titanium mesh substrate;

FIG. 2 shows α -PbO₂Scanning electron microscopy of the intermediate layer;

FIG. 3 is a scanning electron microscope image of a composite electrode without doping of nano-silicon carbide and graphene oxide;

fig. 4 is a scanning electron microscope image of the composite electrode doped with nano silicon carbide and graphene oxide simultaneously.

Detailed Description

The method for producing a lead dioxide electrode according to the present invention will be described in further detail with reference to the following examples and drawings, which are not intended to limit the present invention.

Example 1

And ultrasonically cleaning the titanium mesh for 15min by acetone, ethanol and deionized water respectively, and taking out and naturally drying. Then thermally decomposing by coatingTi/SnO prepared on surface of titanium mesh₂A Sb bottom layer, wherein the coating liquid comprises 5ml of n-butyl alcohol, 3ml of concentrated hydrochloric acid, 3g of stannic chloride and 0.3g of antimony trichloride. And when the coating liquid is completely dissolved into a uniform and transparent state, dipping the coating liquid by a brush and coating the coating liquid on the titanium mesh. Then placing the mixture in an electric heating constant temperature drying oven to dry for 15min at the temperature of 120 ℃, and then taking out to brush again. After repeating this for 8 times, the resultant was calcined in a muffle furnace at 500 ℃ for 2 hours.

The electrodeposition method is continued to deposit a layer α -PbO on the surface of the electrode₂An intermediate layer. The used electrodeposition solution is 0.1mol/L PbO and 4mol/L NaOH, and the used current density is 40mA/cm². The temperature is 30 ℃, and the electrodeposition is carried out for 1 h.

Then continuing to electrodeposit on the surface of the electrode to obtain β -PbO₂The surface active layer was formed using a bath of 0.5mol/LPb (NO)₃)₂、0.05mol/L HBO₃0.1g/LNaF, the current density used was 20mA/cm². And carrying out electro-deposition for 1h at the temperature of 60 ℃ to obtain the undoped lead dioxide electrode.

And analyzing and representing the surface appearance and the catalytic performance of the electrode by using a Scanning Electron Microscope (SEM) and an ultraviolet spectrophotometer.

As shown in fig. 1, it can be seen that the primer layer prepared by the coating pyrolysis method is uniformly cracked to substantially cover the titanium substrate. Thereby, the bonding force between the substrate and each layer can be enhanced, and the passivation of the substrate can be prevented.

As shown in FIG. 2, it can be seen that α -PbO was obtained by the electrodeposition method₂The existence of the intermediate layer can relieve the electrodeposition distortion of the surface coating and strengthen the substrate and β -PbO₂The bonding force between the surface active layers.

As shown in FIG. 3, it can be seen that undoped β -PbO was obtained by the electrodeposition method₂The surface active layer has non-uniform particles and larger particles, which reduces β -PbO₂Thereby affecting the catalytic performance thereof, and β -PbO₂The surface cracks, which undoubtedly reduce the difficulty of the solution entering the interior of the electrodeAnd affects its useful life.

At a temperature of 50 ℃, the current density is 60mA/cm²The electrode area is 2cm²Catalytic degradation experiments were performed on 2, 4-diaminotoluene (TDA) using undoped lead dioxide electrodes. Wherein the initial concentration of TDA is 0.3 g/L. The TDA degradation rate was found to be 76.6%.

The life of the electrode was tested by accelerated life testing. The tested electrode is taken as an anode, a copper sheet is taken as a cathode, and a constant current method is adopted to keep the current density at 2A/cm²The electrode spacing was 2cm at 2mol/L H₂SO₄The life test experiment is carried out, and the electrode deactivation standard is that the voltage is increased to 10V. As a result, it was found that the lifetime of the undoped electrode was 12 hours.

Example 2

The same procedure was followed, analogously to example 1, to obtain a primer layer and α -PbO₂An electrode with an intermediate layer, and β -PbO obtained on the surface of the electrode by an electrochemical deposition method₂The surface active layer is formed by using 0.5mol/L Pb (NO) as electrodeposition solution₃)₂、0.05mol/L HBO₃0.1g/LNaF, 50mg/L Graphene Oxide (GO) and 20mg/L nano SiC; the current density used was 20mA/cm². The temperature is 60 ℃, and the novel lead dioxide composite electrode can be obtained after electrodeposition for 1 h.

The surface morphology and the catalytic performance of the electrode were analyzed and characterized by a Scanning Electron Microscope (SEM) and an ultraviolet spectrophotometer, as shown in FIG. 4, it can be seen that β -PbO on the surface of the composite electrode simultaneously doped with nano-silicon carbide and graphene oxide obtained by the electrodeposition method₂The particles are uniform and compact, and the particle size is small. This will increase the effective catalytic surface of the electrode and improve the catalytic performance. Meanwhile, the surface-doped nano silicon carbide and the graphene oxide can cooperate with each other to supplement electrode surface vacancies, repair the vacancies and prolong the service life of the electrode. The catalytic degradation experiment and the life test were carried out in the same manner as in example 1, and it was found that the degradation rate of TDA was as high as 88.5% and the electrode life was as high as 57 hours after 3 hours of degradation.

Through comparison of the embodiments, it can be found that when the surface of the electrode is doped with the nano silicon carbide and the graphene oxide, the service life of the electrode can be obviously prolonged, and meanwhile, the high catalytic activity of the electrode is ensured. The service life of the doped electrode is improved by 4.75 times, and the catalytic activity is also improved by 1.16 times. Therefore, the technical problem that the service life of the electrode and the catalytic performance of the electrode are difficult to obtain simultaneously is solved, and the method has wide market application prospect.

Claims

1. A method of making a lead dioxide electrode for use as an anode in electrocatalytic wastewater treatment comprising:

preparation of α -PbO on the bottom layer by electrodeposition₂An intermediate layer having a current density of 5mA/cm²~65mA/cm²The total electrodeposition time is 1-2 h, the electrodeposition temperature is 30-80 ℃, the electrode spacing is 2cm, and the electrodeposition solution comprises 0.1-1 mol/L of PbO and 1-10 mol/L of NaOH; and

continuing the electrodeposition method at α -PbO₂Preparation of β -PbO on the intermediate layer₂A surface active layer having a current density of 20mA/cm²~85mA/cm²The total electrodeposition time is 1-2 h, the electrodeposition temperature is 25-100 ℃, the electrode spacing is 2cm, and the electrodeposition solution has a Pb (NO) content of 0.1-1 mol/L₃)₂、0.05~2 mol/L HBO₃0.5-2 g/L NaF, 10-100 mg/L graphene oxide and 10-100 mg/L nano SiC.

2. The method according to claim 1, wherein the cathode used for electrodeposition is selected from the group consisting of a graphite sheet, a copper sheet, a titanium sheet, a stainless steel sheet and a platinum sheet, and the anode is a titanium sheet or a titanium mesh.

3. The production method according to claim 1, wherein degreasing cleaning of the titanium substrate comprises: ultrasonic cleaning in acetone, ethanol and deionized water for 5-15 min.

4. The production method according to claim 1, wherein the mass ratio of tin tetrachloride to antimony trichloride in the coating liquid is 10: 1.

5. A lead dioxide electrode prepared according to one of the methods of claims 1 to 4.