LEAD DIOXIDE-CARBON NANOTUBE ADSORPTIVE ELECTROCHEMICAL SUBMICROELECTRODE AND PREPARATION METHOD AND USE THEREOF

Abstract

The present invention relates to the technical field of electrocatalytic electrode preparation, and discloses a lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode, a preparation method, and use thereof. The electrochemical submicroelectrode according to the present invention comprises multiple layers of orderly arranged spherical lead dioxide submicroholes communicating with each other, where the carbon nanotubes are partially or completely inserted (in the form of twigs) in the lead dioxide hole and in the wall of the hole. The combined effect of adsorption and catalysis inside the submicroreactor effectively solves the problems of low catalytic efficiency and diffusion control associated with the conventional flat lead dioxide electrode, thus greatly improving the electrochemical catalytic performance of the electrode.

Claims

1. A lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode, comprising multiple layers of orderly arranged spherical lead dioxide submicroholes communicating with each other, wherein the carbon nanotubes are partially or completely inserted in the lead dioxide hole and in the wall of the hole.

2. The lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode according to claim 1, wherein the size of the hole is 0.3-10 μm.

3. A method for preparing a lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode, comprising: settling a spherical template adhered with carbon nanotubes down to a substrate to form a film, then preparing a lead dioxide active layer in the gaps between the spherical template by electrodeposition, and finally dissolving the template to obtain the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode.

4. The method for preparing a lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode according to claim 3, wherein the substrate is one selected from antimony tin oxide conductive glass, a titanium plate, foamed titanium, foamed nickel, and a graphite plate.

5. The method for preparing a lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode according to claim 3, wherein the spherical template is one or more selected from polystyrene microspheres and polyacrylic acid microspheres.

6. The method for preparing a lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode according to claim 3, comprising the following steps: Step 1: mixing a polystyrene dispersion and a carbon nanotube dispersion; and heating, to obtain a mixed dispersion with carbon nanotubes adhered to the surface of the polystyrene microsphere template; Step 2: dripping the mixed dispersion in Step 1 on the surface of the antimony tin oxide conductive glass, and drying, to allow the polystyrene microsphere template adhered with carbon nanotubes to form a thin film; Step 3: preparing a lead dioxide active layer in the gaps between the polystyrene microsphere template in the film in Step 2 by electrodeposition; and Step 4: dissolving the polystyrene microsphere template in an organic solvent to obtain the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode.

7. The method for preparing a lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode according to claim 6, wherein the weight ratio of polystyrene and carbon nanotube in the mixed dispersion in Step 1 is (1-3):1; and/or the heating temperature after mixing the polystyrene and carbon nanotubes in Step 1 is 80-180° C., and the heating time is 10-60 min.

8. The method for preparing a lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode according to claim 7, wherein the weight fractions of the polystyrene dispersion and the carbon nanotube dispersion in Step 1 are the same, and within the range of 0.1 to 1%.

9. The method for preparing a lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode according to claim 7, wherein in Step 2, the mixed dispersion is dripped on the surface of the antimony tin oxide conductive glass in an amount of 0.1-1 mL/cm.sup.2; and/or the drying temperature in Step 2 is 40-80° C., and the drying time is 0.5-2 hrs; and/or in Step 3, the electrodeposition current is 5-30 mA/cm.sup.−2, the electrodeposition time is 5-30 min, and the temperature is 30-70° C.; and/or the organic solvent in Step 4 is one selected from tetrachloroethane, styrene, isopropane, benzene, chloroform, xylene, toluene, carbon tetrachloride, or methyl ethyl ketone.

10. Use of the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode according to claim 1 in removing pollutants in water.

11. The method for preparing a lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode according to claim 4, comprising the following steps: Step 1: mixing a polystyrene dispersion and a carbon nanotube dispersion; and heating, to obtain a mixed dispersion with carbon nanotubes adhered to the surface of the polystyrene microsphere template; Step 2: dripping the mixed dispersion in Step 1 on the surface of the antimony tin oxide conductive glass, and drying, to allow the polystyrene microsphere template adhered with carbon nanotubes to form a thin film; Step 3: preparing a lead dioxide active layer in the gaps between the polystyrene microsphere template in the film in Step 2 by electrodeposition; and Step 4: dissolving the polystyrene microsphere template in an organic solvent to obtain the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode.

12. The method for preparing a lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode according to claim 5, comprising the following steps: Step 1: mixing a polystyrene dispersion and a carbon nanotube dispersion; and heating, to obtain a mixed dispersion with carbon nanotubes adhered to the surface of the polystyrene microsphere template; Step 2: dripping the mixed dispersion in Step 1 on the surface of the antimony tin oxide conductive glass, and drying, to allow the polystyrene microsphere template adhered with carbon nanotubes to form a thin film; Step 3: preparing a lead dioxide active layer in the gaps between the polystyrene microsphere template in the film in Step 2 by electrodeposition; and Step 4: dissolving the polystyrene microsphere template in an organic solvent to obtain the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is an SEM image of the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode obtained in Example 1 of the present invention.

[0030] FIG. 2 is a diagram showing the hole size distribution of (a) a lead dioxide electrode prepared by a traditional method and (b) the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode obtained in Example 1 of the present invention.

[0031] FIG. 3 shows an adsorption equilibrium diagram for ferulic acid by the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode (PbO.sub.2 submicroreactor) prepared in Example 1 and CF-PbO.sub.2, 3D-PbO.sub.2, CNTs/PbO.sub.2 and PbO.sub.2-CNTs prepared in Comparative Examples 1A-1D.

[0032] FIG. 4 shows the removal efficiency of ferulic acid over time by the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode (PbO.sub.2 submicroreactor) prepared in Example 1 and CF-PbO.sub.2, 3D-PbO.sub.2, CNTs/PbO.sub.2 and PbO.sub.2-CNTs prepared in Comparative Examples 1A-1D of the present invention.

[0033] FIG. 5 is a graph showing the repeated adsorption of ferulic acid by the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode (PbO.sub.2 submicroreactor) prepared in Example 1 and PbO.sub.2-CNTs prepared in Comparative Example 1D of the present invention.

[0034] FIG. 6 shows an adsorption equilibrium diagram of bisphenol A, salicylic acid, and carbamazepine by the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode (PbO.sub.2 submicroreactor) prepared in Example 1 of the present invention.

DETAILED DESCRIPTION

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of the present invention. The term “and/or” as used herein includes any and all combinations of one or more related listed items.

[0036] Where no specific conditions are given in the examples, conventional conditions or conditions recommended by the manufacturer are followed. The reagents or instruments for which no manufacturers are noted are all common products commercially available from the market.

[0037] As used herein, the term “about” is used to provide flexibility and imprecision related to a given term, metric, or value. Those skilled in the art can easily determine the degree of flexibility of specific variables.

[0038] The concentrations, amounts, and other values are presented in a range format herein. It should be understood that such a range format is used only for convenience and brevity, and should be flexibly interpreted as including not only the values explicitly stated as the limits of the range, but also all individual values or subranges covered within the range, as if each value and subrange are explicitly stated. For example, a numerical range of about 1 to about 4.5 should be interpreted as not only including the explicitly stated limit values of 1 to about 4.5, but also including individual numbers (such as 2, 3, 4) and subranges (such as 1 to 3, 2 to 4). The same principle applies to a range that only states one value, for example “less than about 4.5” should be interpreted as including all the above-mentioned values and ranges. In addition, the interpretation should apply regardless of the range or the breadth of features described.

[0039] The present invention will be further described below with reference to specific embodiments.

Example 1

[0040] The antimony tin oxide conductive glass was cut into a size of 5*5 cm, and washed with acetone, ethanol and water. A 0.25 wt % dispersion of polystyrene microspheres with a diameter of 0.6 μm and a 0.25% dispersion of carbon nanotubes were mixed at a weight ratio of 2:1, and then heated in a water bath at 80° C. for 1 hr. 2.5 mL of the mixed dispersion was dripped onto the cleaned antimony tin oxide conductive glass. Then the sample was dried in an oven at 40° C., to form a film of polystyrene microspheres adhered with carbon nanotubes on the surface of antimony tin oxide conductive glass. The prepared sample was used as the anode, a stainless steel plate of the same size was used as the cathode, the distance between the two electrodes was controlled to 0.5 cm. The magnetic stirrer was turned on, and constant current electrodeposition on the anode was carried out in an electrodeposition solution. The electrodeposition solution was an aqueous solution containing 0.5 mol/L lead nitrate and 0.2 mol/L nitric acid, the current density was 5 mAcm.sup.−2, the electrodeposition time was 30 min, and the temperature was controlled to 55° C. Then the anode was removed, rinsed with deionized water, and soaked in toluene for 8 hrs to dissolve the polystyrene microspheres. The sample was removed, rinsed, and dried to obtain the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode.

[0041] FIG. 1 is an SEM image of the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode obtained in this example. It can be seen from FIG. 1 that after the polystyrene microspheres are dissolved, the lead dioxide-carbon nanotube composite active layer can retain a complete inverse opal-like structure. It can be seen that the carbon nanotubes and lead dioxide in the skeleton are well combined to form a structure similar to asbestos. The edge of the skeleton is burr-like, which increases the exposure of the carbon nanotubes and greatly increases the adsorption capacity and specific surface area of the electrode, thus facilitating the adsorption of pollutants on the catalytic surface of the electrode.

Comparative Example 1A—Conventional Flat Lead Dioxide Electrode (CF-PbO.SUB.2.)

[0042] According to A. Ansari, D. Nematollahi, A comprehensive study on the electrocatalytic degradation, electrochemical behavior and degradation mechanism of malachite green using electrodeposited nanostructured beta-PbO.sub.2 electrodes, Water Res, 144 (2018) 462-473, a conventional flat lead dioxide electrode (CF-PbO.sub.2) was prepared. The specific steps were as follows. The antimony tin oxide conductive glass was cut into a size of 5*5 cm, and washed with acetone, ethanol and water. The treated conductive glass was used as the anode, a stainless steel plate of the same size was used as the cathode, the distance between the two electrodes was controlled to 0.5 cm. The magnetic stirrer was turned on, and constant current electrodeposition on the anode was carried out in an electrodeposition solution. The electrodeposition solution was an aqueous solution containing 0.5 mol/L lead nitrate and 0.2 mol/L nitric acid, the current density was 5 mAcm.sup.−2, the electrodeposition time was 30 min, and the temperature was controlled to 55° C. Then the anode was removed, and rinsed with deionized water. The sample was removed, rinsed, and dried to obtain a conventional flat lead dioxide electrode.

Comparative Example 1B—Three Dimensional Ordered Porous Lead Dioxide Electrode (3D-PbO.SUB.2.)

[0043] According to Liu S, Wang Y, Zhou X, et al. Improved degradation of the aqueous flutriafol using a nanostructure macroporous PbO.sub.2 as reactive electrochemical membrane[J]. Electrochimica Acta, 2017, 253: 357-367, a three dimensional ordered porous lead dioxide electrode (3D-PbO.sub.2) was prepared. The specific steps were as follows. The antimony tin oxide conductive glass was cut into a size of 5*5 cm, and washed with acetone, ethanol and water. 2.5 mL of a 0.17 wt % dispersion of polystyrene microspheres with a diameter of 0.6 μm was dripped onto the cleaned antimony tin oxide conductive glass. Then the sample was dried in an oven at 40° C., to form a film of polystyrene microspheres on the surface of antimony tin oxide conductive glass. The prepared sample was used as the anode, a stainless steel plate of the same size was used as the cathode, the distance between the two electrodes was controlled to 0.5 cm. The magnetic stirrer was turned on, and constant current electrodeposition on the anode was carried out in an electrodeposition solution. The electrodeposition solution was an aqueous solution containing 0.5 mol/L lead nitrate and 0.2 mol/L nitric acid, the current density was 5 mAcm.sup.−2, the electrodeposition time was 30 min, and the temperature was controlled to 55° C. Then the anode was removed, rinsed with deionized water, and soaked in toluene for 8 hrs to dissolve the polystyrene microspheres. The sample was removed, rinsed, and dried to obtain a three dimensional ordered porous lead dioxide electrode.

Comparative Example 1C—Carbon Nanotube/Lead Dioxide Composite Electrode (CNTs/PbO.SUB.2.)

[0044] The specific steps for preparing a carbon nanotube/lead dioxide composite electrode (CNTs/PbO.sub.2) were as follows. The antimony tin oxide conductive glass was cut into a size of 5*5 cm, and washed with acetone, ethanol and water. 2.5 mL of a 0.08% dispersion of carbon nanotubes was dripped onto the cleaned antimony tin oxide conductive glass. Then the sample was dried in an oven at 40° C., to form a film of carbon nanotubes on the surface of antimony tin oxide conductive glass. The prepared sample was used as the anode, a stainless steel plate of the same size was used as the cathode, the distance between the two electrodes was controlled to 0.5 cm. The magnetic stirrer was turned on, and constant current electrodeposition on the anode was carried out in an electrodeposition solution. The electrodeposition solution was an aqueous solution containing 0.5 mol/L lead nitrate and 0.2 mol/L nitric acid, the current density was 5 mAcm.sup.−2, the electrodeposition time was 30 min, and the temperature was controlled to 55° C. Then the anode was removed, and rinsed with deionized water, to obtain a carbon nanotube/lead dioxide composite electrode.

Comparative Example 1D—Lead Dioxide-Carbon Nanotube Adsorptive Electrode (PbO.SUB.2.-CNTs)

[0045] According to Zhou X, Liu S, Xu A, et al. A multi-walled carbon nanotube electrode based on porous Graphite-RuO.sub.2 in electrochemical filter for pyrrole degradation[J]. Chemical Engineering Journal, 2017, 330: 956-964, a lead dioxide-carbon nanotube adsorptive electrode (PbO.sub.2-CNTs) was prepared. The specific preparation steps were as follows. The antimony tin oxide conductive glass was cut into a size of 5*5 cm, and washed with acetone, ethanol and water. The treated conductive glass was used as the anode, a stainless steel plate of the same size was used as the cathode, the distance between the two electrodes was controlled to 0.5 cm. The magnetic stirrer was turned on, and constant current electrodeposition on the anode was carried out in an electrodeposition solution. The electrodeposition solution was an aqueous solution containing 0.5 mol/L lead nitrate and 0.2 mol/L nitric acid, the current density was 5 mAcm.sup.−2, the electrodeposition time was 30 min, and the temperature was controlled to 55° C. Then the anode was removed, and rinsed with deionized water. 2.5 mL of a 0.08% dispersion of carbon nanotubes (containing 0.5% polyacrylonitrile binder) was dripped on the prepared sample, and then the sample was dried in an oven at 60° C. to prepare a lead dioxide-carbon nanotube adsorptive electrode.

[0046] Table 1 shows the specific surface areas of the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode (PbO.sub.2 submicroreactor) prepared in Example 1 and CF-PbO.sub.2, 3D-PbO.sub.2, CNTs/PbO.sub.2 and PbO.sub.2-CNTs prepared in Comparative Examples 1A-1D tested by BET.

TABLE-US-00001 TABLE 1 Specific surface area of the samples in Example 1 and Comparative Examples 1A-1D PbO.sub.2 Sample CF-PbO.sub.2 3D-PbO.sub.2 CNTs/PbO.sub.2 PbO.sub.2-CNTs submicroreactor Specific surface area 0.89 36.51 2.96 79.62 76.56 (m.sup.2/g)

[0047] It can be seen from the data in Table 1 that when no carbon nanotube and polystyrene template are not introduced in Comparative Example 1A, the specific surface area of CF-PbO.sub.2 is small and is only 0.89 m.sup.2/g. When only the polystyrene template is introduced to produce three-dimensional ordered pores, the specific surface area of 3D-PbO.sub.2 in Comparative Example 1B is greatly increased to 36.51 m.sup.2/g. In Comparative Example 1C, when only carbon nanotubes are introduced, the specific surface area of the carbon nanotube/lead dioxide composite electrode (CNTs/PbO.sub.2) is increased to 2.96 m.sup.2/g. Since most of the carbon nanotubes contributing to the specific surface area are covered by lead dioxide, resulting in a small specific surface area. In Comparative Example 1D, by simply adhering the carbon nanotubes to the surface of the lead dioxide electrode, the specific surface area of the lead dioxide-carbon nanotube adsorptive electrode (PbO.sub.2-CNTs) is increased to 79.62 m.sup.2/g. Although the specific surface area of the electrode is greatly improved, it is achieved only by simply adhering the carbon nanotubes to the surface of the electrode. The electrode prepared by this method has a short life and the carbon nanotube adhered to the surface is easy to fall off. In Example 1, when the polystyrene template is used to introduce both the porous structure and the carbon nanotubes, the specific surface area reaches 76.56 m.sup.2/g. It can be seen that although part of the carbon nanotubes is covered by lead dioxide, the specific surface area still maintains a high value due to the protection from the template. Because the wall of the hole is formed by carbon nanotube and lead dioxide, the life of the electrode is prolonged and the carbon nanotube is prevented from falling off.

[0048] FIG. 2 is a diagram showing the hole size distribution of (a) the CF-PbO.sub.2 electrode obtained in Comparative Example 1A and (b) the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode obtained in Example 1 of the present invention. It can be seen from FIG. 2 that the obtained lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode has more micropores and mesopores, which are beneficial to the increase of the specific surface area of the electrode.

Example 2

[0049] The adsorptions for ferulic acid by the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode (PbO.sub.2 submicroreactor) prepared in Example 1 and CF-PbO.sub.2, 3D-PbO.sub.2, CNTs/PbO.sub.2 and PbO.sub.2-CNTs prepared in Comparative Examples 1A-1D were compared.

[0050] The specific method was as follows. 300 mL of simulant wastewater containing 40 mg/L ferulic acid was prepared, and the prepared electrode and a stainless steel plate were respectively used as the anode and cathode respectively. The size of the anode was 5 cm*5 cm, the geometric surface area was 25 cm.sup.2, and the thickness was 0.1 cm. The geometric sizes of the cathode were the same as those of the anode. The anode and cathode were connected by a titanium wire to a positive and negative electrode of a power supply respectively. Ferulic acid was adsorbed and the adsorption performances of several electrodes for ferulic acid were compared.

[0051] FIG. 3 shows an adsorption equilibrium diagram for ferulic acid by the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode prepared in Example 1 and CF-PbO.sub.2, 3D-PbO.sub.2, CNTs/PbO.sub.2 and PbO.sub.2-CNTs prepared in Comparative Examples 1A-1D. It can be seen from FIG. 3 that within 120 min, where no carbon nanotubes are introduced, the adsorption capacities of CF-PbO.sub.2 and 3D-PbO.sub.2 are very small. After the introduction of carbon nanotubes, the adsorption capacity of CNTs/PbO.sub.2 is still very small, because the carbon nanotubes are almost completely covered by lead dioxide. The concentration of the ferulic acid solution is decreased from 40 mg/L to 16 mg/L or less at about 50 min by the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode and PbO.sub.2-CNTs merely by virtue of adsorption. This indicates that the carbon nanotubes in the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode obtained in Example 1 of the present invention is not affected by lead dioxide coverage, and the adsorption is still obvious.

Example 3

[0052] 300 mL of simulant wastewater containing 40 mg/L ferulic acid was prepared, and 0.05M Na.sub.2SO.sub.4 was added as an electrolyte. The lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode prepared in Example 1 and the CF-PbO.sub.2, 3D-PbO.sub.2, CNTs/PbO.sub.2 and PbO.sub.2-CNTs prepared in Comparative Examples 1A-1D were respectively used as the anode, and a stainless steel plate was used as the cathode to degrade ferulic acid. The current density was controlled to 20 mA/cm.sup.2, and the degradation performances of the five electrodes for ferulic acid were compared.

[0053] FIG. 4 shows the removal efficiency of ferulic acid over time by the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode prepared in Example 1 and CF-PbO.sub.2, 3D-PbO.sub.2, CNTs/PbO.sub.2 and PbO.sub.2-CNTs prepared in Comparative Examples 1A-1D of the present invention. It can be seen from FIG. 4 that after 1 hr of electrolysis, the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode has better electrocatalytic performance, and ferulic acid is almost completely removed. In contrast, the removal efficiency by CF-PbO.sub.2, 3D-PbO.sub.2, CNTs/PbO.sub.2 and PbO.sub.2-CNTs is 45%, 75%, 60% and 80% respectively. It is to be noted that although the specific surface area of PbO.sub.2-CNTs is greater than that of the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode prepared in Example 1, the carbon nanotubes in PbO.sub.2-CNTs continue to fall off with the elapse of the electrolysis time, which limits the removal rate of ferulic acid.

Example 4

[0054] 300 mL of simulant wastewater containing 40 mg/L ferulic acid was prepared, and 0.05M Na.sub.2SO.sub.4 was added as an electrolyte. At a current density of 20 mA/cm.sup.2, the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode was repeatedly used 10 times to degrade ferulic acid to investigate the in-situ desorption capacity of the electrode adsorption layer.

[0055] FIG. 5 is a graph showing the repeated adsorption of ferulic acid by the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode prepared in Example 1 and PbO.sub.2-CNTs prepared in Comparative Example 1D of the present invention. It can be seen that after 10 times of repeated use, the adsorption effect of PbO.sub.2-CNTs decreases significantly, and the adsorption effect is almost 0 at the third time. This may be caused by the falling off of carbon nanotubes during the electrolysis process. However, the adsorption effect of lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode has no obvious decrease after 10 times of repeated use, indicating that the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode prepared in the present invention can effectively adsorb organic pollutants and oxidize them in situ.

Example 5

[0056] 300 mL of simulant wastewater containing 40 mg/L Bisphenol-A, salicylic acid or carbamazepine was respectively prepared. The lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode was used as the anode and a stainless steel plate was used as the cathode. Bisphenol A, salicylic acid, and carbamazepine were adsorbed respectively, and the adsorption performances of the electrode for various pollutants were compared.

[0057] FIG. 6 shows an adsorption equilibrium diagram of bisphenol A, salicylic acid, and carbamazepine by the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode (PbO.sub.2 submicroreactor) prepared in Example 1 of the present invention. It can be seen from FIG. 6 that within 60 min, the concentration of the Bisphenol-A, salicylic acid and carbamazepine solution is decreased from 40 mg/L to 25 mg/L by the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode merely by virtue of adsorption. This indicates that the lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrode obtained in Example 1 of the present invention has good adsorption for various pollutants.

[0058] In some embodiments, a spherical template with a size of any value from 0.3 to 10 μm, excluding 0.6 μm, is also used to prepare lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrodes with various hole sizes following the same method as that in Example 1.

[0059] In some embodiments, the template and carbon nanotube are introduced at a weight ratio of polystyrene to carbon nanotube of (1-3):1, excluding 1:1, to prepare lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrodes having various amounts of inserted carbon nanotubes following the same method as that in Example 1.

[0060] In some embodiments, a polystyrene dispersion and a carbon nanotube dispersion of the same concentration in percent by weight in the range of 0.1 to 1% are used to prepare lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrodes having various densities of holes and carbon nanotubes following the same method as that in Example 1.

[0061] In some embodiments, after the polystyrene and carbon nanotube are mixed, the heating temperature is 80-180° C. and the heating time is 10-60 min, to prepare lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrodes following the same method as that in Example 1.

[0062] In some embodiments, the mixed dispersion of polystyrene and carbon nanotube is dripped to the surface of the antimony tin oxide conductive glass in an amount of 0.1-1 mL/cm.sup.2, to prepare lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrodes following the same method as that in Example 1.

[0063] In some embodiments, after the mixed dispersion is dripped on the cleaned antimony tin oxide conductive glass, the drying temperature is 40-80° C., and the drying time is 0.5-2 hrs, to prepare lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrodes following the same method as that in Example 1.

[0064] In some embodiments, during the preparation of the lead dioxide active layer, the electrodeposition current is 5 −30 mA/cm.sup.−2, the electrodeposition time is 5-30 min and the temperature is 30-70° C., to prepare lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrodes following the same method as that in Example 1.

[0065] In some embodiments, the organic solvent is one selected from tetrachloroethane, styrene, isopropane, benzene, chloroform, xylene, toluene, carbon tetrachloride, and methyl ethyl ketone to remove the polystyrene microsphere template, so as to prepare lead dioxide-carbon nanotube adsorptive electrochemical submicroelectrodes following the same method as that in Example 1.

[0066] The above description is merely a schematic description of the present invention and implementations thereof, and is not restrictive. The embodiment only shows one of the implementations of the present invention, and the actual structure is not limited to thereto. Therefore, similar structures and embodiments designed by a person of ordinary skill in the art as inspired by the disclosure herein without departing from the spirit of the present invention and without creative efforts shall fall within the protection scope of the present invention.