CN111137954B

CN111137954B - Photoelectric cathode, preparation method thereof and method for removing chloroacetic acid contained in water

Info

Publication number: CN111137954B
Application number: CN201911157691.5A
Authority: CN
Inventors: 张弓; 张军; 刘会娟; 吉庆华; 曲久辉
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2019-11-22
Filing date: 2019-11-22
Publication date: 2021-08-03
Anticipated expiration: 2039-11-22
Also published as: CN111137954A

Abstract

The application discloses a photoelectric cathode, a preparation method thereof and a method for removing chloroacetic acid contained in water. The photoelectric cathode is Cu/Cu loaded by metal palladium₂The O/CuO/Pd electrode is prepared by a calcination coupling electrodeposition method. Cu/Cu supported by metal palladium₂The O/CuO/Pd photocathode carries out photoelectrocatalysis treatment on water containing chloroacetic acid so as to remove the chloroacetic acid contained in the water. The method for removing chloroacetic acid contained in water has the advantages of simple operation process, low material price, low treatment cost, higher catalytic performance and good stability, and can be applied to the advanced treatment engineering technology of the tail water of the wastewater containing chloroacetic acid.

Description

Photoelectric cathode, preparation method thereof and method for removing chloroacetic acid contained in water

Technical Field

The application relates to but is not limited to the field of water treatment, in particular to but not limited to a photocathode, a preparation method thereof and a method for removing chloroacetic acid contained in water.

Background

Chloroacetic acid is a common byproduct of drinking water disinfection, and mainly comprises monochloroacetic acid, dichloroacetic acid and trichloroacetic acid. Chloroacetic acid has an extremely adverse effect on human health, particularly its carcinogenic and reproductive toxicity. Chloroacetic acid can cause the decline of the central nervous system of human body and also affect the energy of liver and kidney, and has been proved to have mutagenicity and carcinogenicity in animal experiments and teratogenicity and neurotoxicity. The U.S. environmental protection agency (USEPA) specifies that the maximum allowable concentration of chloroacetic acids in drinking water should be below 60 μ g/L.

The prior technology for removing chloroacetic acid in water mainly comprises a flocculation method, an ion exchange method, an oxidation method, a biological method, an electrochemical reduction method and the like. The electrochemical reduction method has the characteristics of high reaction rate, mild conditions, no need of adding toxic chemical reagents, no secondary pollution and the like, is popular, and more importantly, the electrochemical reduction method can realize selective removal of halogen atoms in the compound. The processing mechanism of the electrochemical reduction method comprises direct reduction and indirect reduction, wherein the direct reduction is realized by cathode direct electron transfer, and the indirect reduction is realized by a hydrogenation (H) reduction process. The metal palladium (Pd) catalyst can be widely applied to an electro-catalytic reduction system because the excellent hydrogen production and hydrogen fixation characteristics can effectively improve the indirect reduction effect. However, due to the lack of effective means for characterizing electrode-water interface active species, the research on electrochemical reduction mechanisms, especially indirect reduction mechanisms, is still at the level of inference. The in-situ generation and action mechanism of the atom H in the electric reduction process are not clear, so that the effective regulation and control of the atom hydrogen are more difficult to realize. Meanwhile, the traditional electrochemical hydrogenation reduction is usually carried out under the inert atmosphere conditions such as nitrogen, and the removal cost is greatly increased.

Disclosure of Invention

The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

The application provides a photocathode which is Cu/Cu loaded by metal palladium₂O/CuO/Pd electrode.

In some embodiments, the photocathode may be a nano-array structure.

In some embodiments, the photocathode may include: cu substrate, Cu coated on the Cu substrate₂An O layer formed on Cu₂A CuO nanorod array on the O layer, and Pd nanoparticles loaded on the CuO nanorods.

In some embodiments, the Pd nanoparticles may range in size from 2nm to 8 nm. For example, it may be 3nm, 4nm, 5nm, 6nm, 7nm, or the like.

The present application also provides a method of making a photocathode as described above, which is a calcination coupled electrodeposition process.

In some embodiments, the calcination coupled electrodeposition process may include the steps of: calcining the Cu sheet; and electrodepositing the calcined Cu sheet in a palladium-containing solution.

In some embodiments, the Cu sheet may be calcined in the range of 300 ℃ to 550 ℃ for 1h to 4 h. For example, the calcination may be carried out at 350 ℃, 400 ℃, 450 ℃, 500 ℃ or the like; calcination can be carried out for 1.5h, 2h, 2.5h, 3h, 3.5h, etc.

In some embodiments, the calcination may be a secondary calcination.

In some embodiments, the Cu sheet may be calcined at a temperature in the range of 300 ℃ to 350 ℃ for 1h to 2h, and then calcined at a temperature in the range of 500 ℃ to 550 ℃ for a further 1h to 2 h. For example, the calcination may be carried out at 310 ℃, 320 ℃, 330 ℃, 340 ℃ or the like, and the calcination may be carried out for 1.2h, 1.5h, 1.8h or the like; then, the mixture is calcined at 510 ℃, 520 ℃, 530 ℃, 540 ℃ and the like for 1.2h, 1.5h, 1.8h and the like.

In some embodiments, electrodeposition can be carried out in a palladium-containing solution having a palladium content of 0.05g/L to 0.1 g/L; for example, the palladium content may be 0.06g/L, 0.07g/L, 0.08g/L, 0.09g/L, and the like.

In some embodiments, the deposition may be continued for 10min to 30min at a voltage ranging from-0.8V to-1.2V. For example, the voltage may be-0.9V, -1.0V, -1.1V, etc.; the deposition time may be 15min, 20min, 25min, etc.

The application also provides a method for removing chloroacetic acid contained in water, which comprises the step of adopting the Cu/Cu supported by the metal palladium₂The O/CuO/Pd photocathode carries out photoelectrocatalysis treatment on water containing chloroacetic acid.

In some embodiments, a cathode voltage of 0.0V to-1.2V may be applied to the photocathode. For example, -0.2V, -0.5V, -0.8V, -1.0V, etc. can be applied.

In some embodiments, the photoelectrocatalytic treatment may be performed under an air atmosphere.

In some embodiments, the water may contain chloroacetic acid in an amount of 0.05mg/L to 5 mg/L. For example, it may be 0.1mg/L, 0.5mg/L, 1mg/L, 1.5mg/L, 2mg/L, 2.5mg/L, 3mg/L, 3.5mg/L, 4mg/L, 4.5mg/L, or the like.

In some embodiments, the chloroacetic acid removed may include one or more of monochloroacetic acid, dichloroacetic acid, trichloroacetic acid.

In some embodiments, the photocathode can be prepared using the methods described above for preparing photocathodes.

Compared with the prior art, the beneficial effect that this application has lies in:

the photocathode provided by the application has the advantages of large contact area, excellent photoelectric conversion performance, ultra-fast photoproduction charge transfer rate and high catalytic performance;

the preparation method of the photocathode is simple in process, and the prepared photocathode is stable in performance;

the method for removing chloroacetic acid contained in water can be carried out in the air atmosphere, is simple in operation process, low in material price, low in treatment cost, high in catalytic performance and good in stability, and can be applied to the advanced treatment engineering technology of the tail water of wastewater containing chloroacetic acid.

Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the application. The objectives and other advantages of the application may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The accompanying drawings are included to provide a further understanding of the claimed subject matter and are incorporated in and constitute a part of this specification, illustrate embodiments of the subject matter and together with the description serve to explain the principles of the subject matter and not to limit the subject matter.

FIG. 1 is a schematic diagram of a process for preparing a photocathode according to an embodiment of the present disclosure;

FIG. 2 is a transmission electron microscope image of a photocathode according to an embodiment of the present application;

FIG. 3 is an elemental analysis diagram of a photocathode according to an embodiment of the present application;

FIG. 4 is a graph showing photoelectric conversion performance of photocathodes of examples and comparative examples of the present application;

FIG. 5 is a graph showing the removal rate constant of trichloroacetic acid contained in water at different cathode voltages for photocathodes of examples and comparative examples of the present application;

fig. 6 is a graph showing the residual ratio of trichloroacetic acid in the process of repeated use of photocathodes of examples and comparative examples of the present application.

Detailed Description

To make the objects, technical solutions and advantages of the present application more apparent, embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without conflict.

The embodiment of the application provides Cu/Cu loaded by metal palladium₂The preparation method of the O/CuO/Pd nano-array photocathode can adopt a calcination coupling electrodeposition method, for example, as shown in FIG. 1.

Firstly, providing a Cu sheet; then calcining the Cu sheet for 1 to 2 hours at the temperature of between 300 and 350 ℃, and then continuously calcining for 1 to 2 hours at the temperature of between 500 and 550 ℃. First firing to form Cu covering the Cu substrate₂O layer, second calcining further in Cu₂An array of CuO nanorods (shown by vertical lines in fig. 1) was formed on the O layer.

Cooling to room temperature, and electrodepositing the calcined Cu sheet in a palladium-containing solution to obtain the Cu/Cu supported by metal palladium₂O/CuO/Pd nano-array photocathode.

Wherein the palladium content in the palladium-containing solution is 0.05 g/L-0.1 g/L, and the deposition is continued for 10 min-30 min under the voltage ranging from-0.8V to-1.2V.

The Cu sheet may be cleaned prior to calcination, for example, the cleaned Cu sheet may be repeatedly washed with dilute hydrochloric acid, ethanol, and deionized water, respectively.

The firing of the Cu sheet may be performed, for example, in a muffle furnace.

Metallic palladium supported Cu/Cu obtained after electrodeposition₂The O/CuO/Pd photocathode can be repeatedly rinsed with deionized water.

The metal palladium-loaded Cu/Cu of the embodiment can be prepared by the calcination coupling electrodeposition method₂The O/CuO/Pd nano-array photocathode is characterized in that the surface of a smooth Cu sheet is subjected to first calcinationSintering and growing to form a layer of compact Cu₂O film layer, followed by a second calcination in Cu₂And (3) continuously forming CuO nanorods on the surface of the O layer in a whole column, and finally, uniformly depositing Pd nanoparticles loaded on the surface of the CuO nanorods through the action of electrodeposition. The layered heterostructure is beneficial to the gradual transmission of electrons and improves the utilization rate of the electrons.

Compared with the method of directly loading metal Pd on a Cu foil, the Cu/Cu loaded with metal Pd in the embodiment of the application has no photocatalysis, larger resistance and lower reaction active sites₂The O/CuO/Pd nano-array photocathode has higher catalytic activity.

Metallic palladium supported Cu/Cu₂The O/CuO/Pd nano-array photocathode can efficiently form rich atomic hydrogen (H) on the surface of Pd under low voltage (for example, -0.5V vs. RHE), and meanwhile, the excessive H effectively reduces dissolved oxygen in water to generate hydrogen peroxide (H)₂O₂) H formed by₂O₂Further catalytic reduction by the Cu substrate generates a large amount of hydroxyl free radicals (. OH), and the generated H and OH can efficiently and synergistically remove chloroacetic acid contained in water. Specifically, H initiates the chloroacetic acid dechlorination reaction, and OH effectively attacks the dechlorination intermediate products. And finally, the chloroacetic acid is efficiently removed through efficient synergistic cooperation of H and OH.

Removing chloroacetic acid contained in water by photoelectrocatalysis, and Cu/Cu loaded by metal palladium can be adopted₂The O/CuO/Pd nano-array photocathode is used as a working electrode, and specifically, the metal palladium-loaded Cu/Cu prepared by the calcination coupling electrodeposition method can be used₂The O/CuO/Pd nano-array photocathode is used as a working electrode, and 0.0V to-1.2V of voltage is applied to the electrode and the operation is carried out at a certain temperature, for example, at normal temperature under the condition of air atmosphere. Can be used for removing chloroacetic acid with the content ranging from 0.05mg/L to 5mg/L, such as monochloroacetic acid, dichloroacetic acid, trichloroacetic acid and the like.

Example 1

Preparation of metallic Palladium-Supported Cu/Cu₂O/CuO/Pd nano-array photocathode.

1) Respectively putting the clean Cu sheet into dilute hydrochloric acid, ethanol and deionized water for repeated cleaning, then putting the cleaned Cu sheet into a muffle furnace, respectively heating the cleaned Cu sheet for 1 hour and 2 hours at constant temperatures of 300 ℃ and 500 ℃, and taking the cleaned Cu sheet out after cooling to room temperature;

2) placing the Cu sheet obtained by calcining in the step 1) in a solution of palladium chloride (the palladium content is 0.05g/L), continuously depositing for 20min under a constant external voltage of-0.8V, finally taking out and repeatedly washing with deionized water to obtain the Cu/Cu supported by metal palladium₂O/CuO/Pd nano-array photocathode.

Comparative example 1

Preparation of Cu/Cu without Metal Palladium support Using the same method as in step 1) of example 1₂O/CuO photocathode.

Comparative example 2

A simple Cu sheet was used as the photocathode.

Performance testing

1、Phase and structure characterization test

For the metallic palladium-supported Cu/Cu prepared in example 1₂And performing phase and structure characterization tests on the O/CuO/Pd nano-array photocathode, and analyzing by a high-resolution transmission electron microscope image and an element analysis image.

The result of the high-resolution transmission electron microscope is shown in FIG. 2, which shows that the metal palladium particles with uniform size distribution are uniformly loaded on Cu/Cu₂On O/CuO, the size of metal palladium particles is 2 nm-8 nm, a good layered heterostructure is formed, and meanwhile, a good one-dimensional array structure can effectively increase the contact area and promote charge transfer.

The elemental analysis results are shown in FIG. 3, and it can be seen that the metal palladium particles are uniformly distributed in Cu/Cu₂O/CuO, and mainly consists of three elements of Cu, O and Pd.

2、Photoelectric conversion performance test

The photocathodes prepared in example 1, comparative example 1 and comparative example 2 were subjected to photoelectric conversion performance tests, respectively.

Photoelectric conversion performance is shown in FIG. 4, and it can be seen that compared with Cu/Cu of comparative example 1 without metal palladium support₂O/CuO photocathode and comparative example2, Cu photocathode of the present application, Cu/Cu supported on metallic palladium prepared in example 1 of the present application₂The O/CuO/Pd photocathode has good photo-electric response performance, namely, the photocathode can efficiently absorb and utilize light energy and convert the light energy into electric energy to generate a large amount of electrons. The photoelectric conversion performance is excellent, the photo-generated charge transfer rate is ultra-fast, and the sunlight can be effectively utilized to realize high-efficiency photoelectric catalytic activity.

3、Photoelectrocatalysis removal chloroacetic acid test

The method comprises the following steps:

1) the photocathodes prepared in example 1, comparative example 1 and comparative example 2 are respectively used as working electrodes, a platinum sheet is used as a counter electrode, silver and silver chloride are used as reference electrodes, a double-chamber H-shaped electrolytic cell is used as a reaction device, the working electrodes and the reference electrodes are arranged in the same reaction electrode chamber, and the working electrode chamber adopts 5mg/L chloroacetic acid solution and 2mM sodium sulfate electrolyte;

2) A150W xenon lamp light source is used for simulating sunlight to provide illumination, the working electrode is continuously illuminated, a certain external bias voltage is applied at the same time, sampling is carried out at regular time, and the removal condition of chloroacetic acid in the solution is detected through ion chromatography.

Chloroacetic acid, the most common, most widely distributed and large amount of chloroacetic acid contained in water, is trichloroacetic acid. In the following test, the removal of chloroacetic acid is described by taking trichloroacetic acid removed as a representative. The removal principle of other chloroacetic acids such as monochloroacetic acid, dichloroacetic acid and the like is the same, and the effect is similar to that of trichloroacetic acid.

Test oneThe following were used:

according to the testing steps for removing chloroacetic acid by photoelectrocatalysis, the external bias voltages of 0.0V, -0.1V, -0.3V, -0.5V and-0.7V are respectively selected, and the influence of the external voltage on the removal of trichloroacetic acid by photoelectrocatalysis is analyzed.

The test results are shown in FIG. 5, and it can be seen that Cu/Cu without metallic Palladium support is compared to Cu/Cu of comparative example 1₂O/CuO photocathode, and Cu photocathode of comparative example 2, Cu/Cu supported on metallic palladium prepared in example 1 of the present application₂The removal efficiency of the O/CuO/Pd photocathode to the trichloroacetic acid is improved within 60min of reaction timeNearly 100 percent, can realize complete dechlorination and removal. Under the action of photoelectricity combined catalysis, Cu/Cu loaded by metal palladium₂The O/CuO/Pd photocathode can realize high-efficiency chloroacetic acid removal efficiency under low voltage, and meanwhile, the load of metal Pd greatly improves the chloroacetic acid removal efficiency.

Test twoThe following were used:

at 25 ℃, under the air atmosphere condition, the removal stability experiment is carried out according to the photoelectrocatalysis chloroacetic acid removal testing steps.

The test results are shown in FIG. 6, and it can be seen that Cu/Cu without metallic Palladium support is compared to Cu/Cu of comparative example 1₂O/CuO photocathode, and Cu photocathode of comparative example 2, Cu/Cu supported on metallic palladium prepared in example 1 of the present application₂The O/CuO/Pd photocathode passes 10 times of cycle tests, most of trichloroacetic acid is removed, and the residual rate is still close to 0, which shows that the photocathode of the embodiment of the application has good stability and reusability, keeps a higher chloroacetic acid removal level in the repeated use process, and realizes the reusability of the system.

Although the embodiments disclosed in the present application are described above, the descriptions are only for the convenience of understanding the present application, and are not intended to limit the present application. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims.

Claims

1. A photocathode, wherein the photocathode is Cu/Cu loaded by metal palladium₂O/CuO/Pd electrode.

2. The photocathode of claim 1, wherein the photocathode is a nano-array structure.

3. The photocathode of claim 1 or 2, wherein the photocathode comprises:

a Cu substrate, Cu coated on the Cu substrate₂An O layer formed on the Cu₂A CuO nanorod array on the O layer, and Pd nanoparticles loaded on the CuO nanorods.

4. The photocathode of claim 3, wherein the Pd nanoparticles are 2nm to 8nm in size.

5. A method of making the photocathode of any one of claims 1-4, which is a calcination coupled electrodeposition process.

6. The method of claim 5, the calcination coupled electrodeposition process comprising the steps of:

calcining the Cu sheet;

and electrodepositing the calcined Cu sheet in a palladium-containing solution.

7. The method of claim 6, wherein the Cu sheet is calcined at a temperature in the range of 300 ℃ to 550 ℃ for 1h to 4 h.

8. The method of claim 6 or 7, wherein the calcining is a secondary calcining;

calcining the Cu sheet for 1 to 2 hours at the temperature of between 300 and 350 ℃, and then continuously calcining for 1 to 2 hours at the temperature of between 500 and 550 ℃.

9. The method according to claim 6 or 7, wherein the electrodeposition is carried out in a palladium-containing solution having a palladium content of 0.05 to 0.1 g/L.

10. The method according to claim 8, wherein the electrodeposition is performed in a palladium-containing solution having a palladium content of 0.05 to 0.1 g/L.

11. The method according to any one of claims 6-7 and 10, wherein the deposition is continued for 10-30 min at a voltage in the range of-0.8V to-1.2V.

12. The method of claim 8, wherein the deposition is continued for 10-30 min at a voltage ranging from-0.8V to-1.2V.

13. The method of claim 9, wherein the deposition is continued for 10-30 min at a voltage ranging from-0.8V to-1.2V.

14. A method for removing chloroacetic acid contained in water, comprising subjecting chloroacetic acid-containing water to a photoelectrocatalytic treatment using the photocathode according to any one of claims 1 to 4.

15. The method of claim 14, wherein a cathode voltage of 0.0V to-1.2V is applied to the photocathode.

16. The method of claim 14 or 15, wherein the photoelectrocatalytic treatment is performed under an air atmosphere.

17. A method according to claim 14 or 15, wherein the water contains chloroacetic acid in an amount of 0.05mg/L to 5 mg/L.

18. The method of claim 16, wherein the water contains chloroacetic acid in an amount of 0.05mg/L to 5 mg/L.

19. The method of any one of claims 14-15 and 18, wherein the removed chloroacetic acid comprises one or more of monochloroacetic acid, dichloroacetic acid, trichloroacetic acid.

20. The method of claim 16, wherein the removed chloroacetic acid comprises one or more of monochloroacetic acid, dichloroacetic acid, trichloroacetic acid.

21. The method of claim 17, wherein the removed chloroacetic acid comprises one or more of monochloroacetic acid, dichloroacetic acid, trichloroacetic acid.