Preparation method and application of TiO2 nano-array composite electrode

Abstract

The present invention discloses a preparation method and application of a TiO2 nano-array composite electrode, belonging to the technical field of photoelectrocatalytic composite materials. The present invention comprises: (1) ultrasonically washing a titanium foil and then polishing it; (2) electrolytically oxidizing the titanium foil using the titanium foil as an anode and a titanium plate as a cathode, washing the oxidized titanium foil, and then annealing it to obtain anatase-type TiO2 nanotubes; (3) dissolving bismuth nitrate pentahydrate and potassium bromide in ethylene glycol and stirring them, and then adding ferric nitrate nonahydrate to obtain an Fe / BiOBr precursor solution; (4) hydrothermally reacting the Fe / BiOBr precursor solution obtained in step (3) with the anatase-type TiO2 nanotubes obtained in step (2), and then washing and drying the reaction product to obtain a TiO2 nano-array composite electrode. The composite electrode prepared by the present invention has high catalytic activity and achieves efficient degradation of EE2 and CAP by 99.2% and 97.6%, respectively.

Description

Technical Field

[0001] The invention belongs to the technical field of photoelectrocatalytic composite materials and relates to a preparation method of a TiO2 nano-array composite electrode and application thereof. Background Art

[0002] With the rapid development of industrialization and modernization, new pollutants have emerged. New pollutants refer to a class of chemical substances that can be detected in the environment and natural ecosystems, and can pose greater risks and hidden dangers to human health and environmental safety even if they enter at low doses. They mainly include persistent organic pollutants, endocrine disruptors, antibiotics, microplastics, etc. that are controlled by international conventions. Their spread and accumulation in the environment pose a serious threat to the entire ecosystem and human health.

[0003] In aquatic environments, new pollutants mostly exist in the form of mixed pollutants, which may produce synergistic or antagonistic effects, making their treatment more difficult. Photoelectric coupled catalysis, a new advanced oxidation technology that combines photocatalysis with electrocatalysis, can effectively overcome the shortcomings of the photocatalytic process, where photogenerated electron-hole pairs are easily recombinated, while fully leveraging the advantages of electrocatalysis. It also has the advantages of no secondary pollution and is made of inexpensive and readily available materials. Therefore, it has broad application prospects in the treatment of new pollutants.

[0004] TiO2 nanotubes are widely used in photoelectrocatalytic technologies due to their large surface area, sufficient contact with the electrolyte, and excellent chemical stability. They primarily exist in the form of TiO2 nanoarray composite electrodes. However, current TiO2 nanoarray composite electrodes suffer from the problem of the loaded material clogging the tube openings, resulting in a decrease in the composite electrode's light absorption capacity. This ultimately weakens the composite electrode's catalytic activity and affects its ability to treat new pollutants.

[0005] Therefore, it is necessary to provide a preparation method and application of a TiO2 nanoarray composite electrode to avoid clogging of the tube orifice by the loaded material, improve the catalytic activity of the composite electrode, and enable the TiO2 nanoarray composite electrode to have better new pollutant degradation ability. Summary of the Invention

[0006] In order to overcome the problems in the background technology, the TiO2 nanoarray composite electrode prepared by the preparation method of the present invention forms an angle between the Fe-doped BiOBr (Fe / BiOBr) sheet grown on the TiO2 nanotubes and the TiO2 nanotubes, effectively avoiding the situation where the load material blocks the tube mouth, thereby improving the light absorption capacity of the composite electrode, thereby improving the catalytic activity of the TiO2 nanoarray composite electrode, and ultimately improving the catalytic degradation ability of the composite electrode for pollutants.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] In one aspect, the present invention provides a method for preparing a composite electrode in which Fe-doped BiOBr is vertically grown on a TiO2 nanoarray. The method comprises the following steps:

[0009] (1) Ultrasonic cleaning of titanium foil and then polishing;

[0010] (2) using the titanium foil treated in step (1) as an anode and the titanium plate as a cathode to perform electrolytic oxidation, washing the oxidized titanium foil, and then annealing to obtain anatase TiO2 nanotubes;

[0011] (3) dissolving bismuth nitrate pentahydrate and potassium bromide in ethylene glycol and stirring, and then adding ferric nitrate nonahydrate to obtain a Fe / BiOBr precursor solution;

[0012] (4) hydrothermally reacting the Fe / BiOBr precursor solution obtained in step (3) with the anatase TiO2 nanotubes obtained in step (2), and then washing and drying the reaction product to obtain a TiO2 nanoarray composite electrode.

[0013] Preferably, in step (1), the titanium foil is ultrasonically cleaned using acetone, anhydrous ethanol, and ultrapure water in sequence, with each washing lasting 15 to 30 minutes.

[0014] Preferably, in step (1), the polishing liquid used for polishing is prepared from hydrofluoric acid, nitric acid and water in a volume ratio of HF:HNO3:H2O=1:4:5, and the polishing time is 30 to 60 seconds.

[0015] Preferably, in step (2), the electrolyte used for electrolytic oxidation is prepared by water, ethylene glycol, and ammonium fluoride. First, water and ethylene glycol are mixed in a volume ratio of H2O:C2H6O2=1:49 to obtain a solvent, and then ammonium fluoride is added to the solvent in a mass ratio of NH4F:solvent=1:399 to prepare an electrolyte.

[0016] Preferably, in step (2), the electrolytic oxidation voltage is 30 V and the electrolytic oxidation time is 1 to 3 hours.

[0017] Preferably, in step (2), the annealing temperature is 450-550° C., the heating rate is 3-7° C. / min, and the holding time is 1-3 h.

[0018] Preferably, in step (3), the amounts of bismuth nitrate pentahydrate and potassium bromide are equal, the solid-liquid ratios of bismuth nitrate pentahydrate and potassium bromide to ethylene glycol are both 1-3 mmol:500 ml, and the solid-liquid ratio of ferric nitrate nonahydrate to ethylene glycol is 5-7 mmol:5000 ml.

[0019] Preferably, in the step (3), after adding ferric nitrate nonahydrate, stirring is continued for 1 to 3 hours to obtain a Fe / BiOBr precursor solution.

[0020] Preferably, in step (4), the hydrothermal reaction temperature is 100-200° C., and the reaction time is 9-11 h.

[0021] Another aspect of the present invention provides the application of the TiO2 nano-array composite electrode in the degradation of 17α-ethynylestradiol and chloramphenicol.

[0022] Beneficial effects of the present invention:

[0023] 1. The TiO2 nanoarray composite electrode prepared by the present invention can effectively prevent the Fe / BiOBr sheet from clogging the nanotube orifices, improve the light absorption capacity of the composite electrode, and enable the composite electrode to exhibit strong light absorption capacity in the entire visible light band. It has high stability and excellent visible light response, and the composite electrode has a better ability to degrade pollutants.

[0024] 2. The TiO2 nano-array composite electrode prepared by the present invention greatly increases the wettability and exposed specific surface area of ​​the Fe / BiOBr sheet, thereby improving the catalytic activity of the TiO2 nano-array composite electrode and thus enhancing the composite electrode's catalytic degradation ability for pollutants.

[0025] 3. The present invention does not generate secondary pollutants such as toxic heavy metals during the reaction process of degrading new pollutants.

[0026] 4. The composite electrode of the present invention has a highly efficient degradation effect on 17α-ethynylestradiol (EE2) and chloramphenicol (CAP) in water, with degradation rates of 99.2% and 97.6%, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 These are the EDS images of the composite electrodes prepared in Comparative Example 1, Comparative Example 2, and Example 1, where (a) is the composite electrode prepared in Comparative Example 2, (b) is the composite electrode prepared in Comparative Example 1, (c) is the composite electrode prepared in Example 1, and (d1-d6) are the elemental compositions of the composite electrodes in Example 1.

[0028] Figure 2 These are the XRD patterns of the composite electrodes prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0029] Figure 3 The cyclic voltammetry (CV) curves of the composite electrodes prepared in Example 1, Comparative Example 1, and Comparative Example 2 are shown.

[0030] Figure 4 These are the UV-visible diffuse reflectance spectra of the composite electrodes prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0031] Figure 5 This is a comparison chart of the degradation effects of the composite electrodes prepared in Example 1, Comparative Example 1, and Comparative Example 2 in a mixed system. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below with reference to specific embodiments.

[0033] In the embodiments and comparative examples of the present invention, chemical reagents not specifically described are

[0034] Example 1

[0035] This example prepares a TiO2 nano-array composite electrode according to the following steps:

[0036] (1) High-purity titanium foil (Ti≥99.99%, thickness 0.3 mm) was cut into 3.0*4.0 cm rectangles. The cut titanium foil was placed in acetone, anhydrous ethanol and ultrapure water for ultrasonic washing for 15 min respectively.

[0037] (2) The titanium foil was then immersed in a polishing solution with a volume ratio of HF:HNO3:H2O=1:4:5 and chemically polished for 35 seconds.

[0038] (3) The polished titanium foil was used as the anode and the titanium plate was used as the cathode. The two were placed in an electrolyte and oxidized at an oxidation voltage of 30 V for 2 h. The electrolyte was prepared by mixing water and ethylene glycol at a volume ratio of H2O:C2H6O2=1:49 to obtain a solvent. Ammonium fluoride was then added to the solvent at a mass ratio of NH4F:solvent=1:399.

[0039] (4) After the electrolytically oxidized titanium foil is rinsed with ultrapure water, the titanium foil is placed in a muffle furnace for annealing. The muffle furnace is set to heat up to 450°C at a heating rate of 5°C / min, kept warm for 2 hours, and then cooled naturally to obtain anatase-type titanium dioxide nanotubes.

[0040] (5) 0.2 mmol of Bi(NO3)3·5H2O and KBr were dissolved in 50 mL of C2H6O2, and then 0.06 mmol of Fe(NO3)3·9H2O was added to the mixed solution under magnetic stirring for 1 h to obtain a Fe / BiOBr precursor solution;

[0041] (6) The Fe / BiOBr precursor solution was then transferred to a 100 mL polytetrafluoroethylene liner loaded with anatase titanium dioxide nanotubes, and the Fe / BiOBr precursor solution and anatase titanium dioxide nanotube mixture were heated to 160°C and maintained for 10 h. After sufficient cooling, the reaction product was rinsed several times with anhydrous ethanol and ultrapure water alternately, and then placed in a vacuum drying oven and vacuum dried at 60°C for 6 h to obtain a TiO2 nanoarray composite electrode. The nanoarray composite electrode prepared in this example is recorded as F / B-TNTAs.

[0042] The F / B-TNTAs prepared in this example were subjected to transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, cyclic voltammetry, UV-light diffuse reflection, and degradation effect experiments. The results were as follows: Figure 1-5 shown.

[0043] Example 2

[0044] This example prepares a TiO2 nano-array composite electrode according to the following steps:

[0045] (1) High-purity titanium foil (Ti ≥ 99.99%, thickness 0.3 mm) was cut into 3.0 × 5.0 cm rectangles. The cut titanium foil was ultrasonically washed in acetone, anhydrous ethanol, and ultrapure water for 30 min each.

[0046] (2) The titanium foil was then immersed in a polishing solution with a volume ratio of HF:HNO3:H2O=1:4:5 and chemically polished for 60s;

[0047] (3) The polished titanium foil was used as the anode and the titanium plate was used as the cathode, and the electrodes were placed in an electrolyte solution and oxidized at an oxidation voltage of 30 V for 1 h.

[0048] (4) After the electrolytically oxidized titanium foil is rinsed with ultrapure water, the titanium foil is placed in a muffle furnace for annealing. The muffle furnace is set to heat up to 500°C at a heating rate of 3°C / min, kept at this temperature for 3 hours, and then cooled naturally to obtain anatase titanium dioxide nanotubes;

[0049] (5) 0.1 mmol of Bi(NO3)3·5H2O and KBr were dissolved in 50 mL of C2H6O2, and then 0.05 mmol of Fe(NO3)3·9H2O was added to the mixed solution under magnetic stirring for 3 h to obtain a Fe / BiOBr precursor solution;

[0050] (6) The Fe / BiOBr precursor solution was then transferred to a 100 mL polytetrafluoroethylene liner loaded with titanium dioxide nanotubes. The Fe / BiOBr precursor solution and anatase titanium dioxide nanotube mixture were heated to 200 °C and maintained for 9 h. After sufficient cooling, the reaction product was alternately rinsed several times with anhydrous ethanol and ultrapure water, and then placed in a vacuum drying oven and vacuum dried at 60 °C for 6 h to obtain a nanoarray composite electrode.

[0051] The nanoarray composite electrode prepared in this example has similar performance to that of Example 1.

[0052] Example 3

[0053] This example prepares a TiO2 nano-array composite electrode according to the following steps:

[0054] (1) High-purity titanium foil (Ti ≥ 99.99%, thickness 0.3 mm) was cut into 2.0 × 5.0 cm rectangles and ultrasonically washed in acetone, anhydrous ethanol, and ultrapure water for 20 min each.

[0055] (2) The titanium foil was then immersed in a polishing solution with a volume ratio of HF:HNO3:H2O=1:4:5 and chemically polished for 30s;

[0056] (3) The polished titanium foil was used as the anode and the titanium plate was used as the cathode, and the electrodes were placed in an electrolyte solution and oxidized at an oxidation voltage of 30 V for 3 h.

[0057] (4) After the electrolytically oxidized titanium foil is rinsed with ultrapure water, the titanium foil is placed in a muffle furnace for annealing. The muffle furnace is set to heat up to 550°C at a heating rate of 7°C / min, kept at this temperature for 1 hour, and then cooled naturally to obtain anatase titanium dioxide nanotubes;

[0058] (5) 0.3 mmol of Bi(NO3)3·5H2O and KBr were dissolved in 50 mL of C2H6O2, and then 0.07 mmol of Fe(NO3)3·9H2O was added to the mixed solution under magnetic stirring for 2 h to obtain a Fe / BiOBr precursor solution;

[0059] (6) The Fe / BiOBr precursor solution was then transferred to a 100 mL polytetrafluoroethylene liner loaded with titanium dioxide nanotubes. The Fe / BiOBr precursor solution and titanium dioxide nanotube mixture was heated to 100 °C and maintained for 11 h. After sufficient cooling, the reaction product was alternately rinsed several times with anhydrous ethanol and ultrapure water, and then placed in a vacuum drying oven and vacuum dried at 60 °C for 6 h to obtain a nanoarray composite electrode.

[0060] The nanoarray composite electrode prepared in this example has similar performance to that of Example 1.

[0061] Comparative Example 1

[0062] In this comparative example, a nano-array composite electrode was prepared using the same method as in Example 1, except that the loading material in this comparative example was not doped with Fe. The nano-array composite electrode prepared in this comparative example was denoted as B-TNTAs.

[0063] The B-TNTAs prepared in this comparative example were subjected to transmission electron microscopy scanning, energy dispersive X-ray spectroscopy experiment, X-ray diffraction, cyclic voltammetry scanning, UV-light diffuse reflection, and degradation effect experiment. The results are as follows: Figure 1-5 shown.

[0064] Comparative Example 2

[0065] In this comparative example, the nanoarray electrode was prepared using the same method as in Example 1, except that the titanium dioxide nanoarray electrode in this comparative example was not loaded with Fe / BiOBr. The nanoarray electrode prepared in this comparative example is denoted as TNTAs.

[0066] The TNTAs prepared in this comparative example were subjected to transmission electron microscopy scanning, energy dispersive X-ray spectroscopy experiment, X-ray diffraction, cyclic voltammetry scanning, UV-light diffuse reflection, and degradation effect experiments. The results were as follows: Figure 1-5 shown.

[0067] pass Figure 1 (a) It can be seen that the preparation method of the present invention can successfully prepare a nanoarray electrode composed of highly dense and ordered nanotube arrays with an average tube diameter of 100 nm.

[0068] pass Figure 1 (b) It can be seen that the gaps between the mouths of TiO2 nanotubes can provide a certain space for the growth of BiOBr sheets, and after the BiOBr sheets grow, the tubular structure of TiO2 nanotubes is not destroyed. Figure 1(b) It can also be observed that there is an angle between the BiOBr sheet and the TiO2 nanotubes (most of which are 90°). The BiOBr sheet does not cover or block the TiO2 nanotube openings. The average thickness of the BiOBr sheet is 25-40 nm.

[0069] pass Figure 1 (c) It can be seen that the introduction of iron doping does not affect the growth direction and structure of the load material. The Fe / BiOBr sheet still maintains an angle with the TiO2 nanotubes, and most of the angles are 90°. The Fe / BiOBr sheet does not cover the TiO2 nanotube openings, effectively avoiding the problem of excessive blockage of the tube openings by the load material, which would cause a decrease in light absorption capacity. This shows that the preparation method of the present invention is relatively stable and can successfully prepare nanoarray composite electrodes with an angle between the Fe / BiOBr sheet and the TiO2 nanotubes.

[0070] Since the radius of the iron ion Relative to the bismuth ion radius The introduction of iron makes the growth of BiOBr crystals limited by shrinkage, and the size is reduced (e.g. Figure 1 (d1)), the average thickness is reduced to 6-12 nm.

[0071] pass Figure 1 (d1-d6) It can be seen that the Ti, O, Bi, Br and Fe elements are uniformly present in the nanoarray composite electrode prepared by the present invention, proving that the preparation method of the present invention can prepare the TiO2 nanoarray composite electrode loaded with Fe / BiOBr.

[0072] pass Figure 2 It can be seen that the TNTAs in Comparative Example 2 correspond one-to-one to the anatase crystal plane standard card (JCPDS 89-4921), showing an anatase-type material. The B-TNTAs in Comparative Example 1 are still anatase-type, but due to the relatively low percentage of BiBOr, the relevant characteristic diffraction peaks (JCPDS 0393) are not obvious, resulting in the inability to clearly represent them in the figure. The diffraction peaks of F / B-TNTAs in Example 1 are significantly increased, indicating that the introduction of Fe further increases the crystallization strength of TNTAs, and the catalytic performance of the composite electrode is improved.

[0073] pass Figure 3It can be seen that the TNTAs in Comparative Example 2 did not show an oxidation peak, indicating that its electrochemical activity was poor. The B-TNTAs in Comparative Example 1 showed a clear oxidation peak at around 0.17 v, indicating that it had certain electrochemical activity. The oxidation peak value of F / B-TNTAs in Example 1 was further improved relative to that of Comparative Example 1, and a reduction peak appeared at -1.26 v, indicating that Example 1 had better electrochemical performance than Comparative Example 1 and also had redox ability.

[0074] pass Figure 4 It can be seen that due to the light scattering caused by cracks on the surface, the TNTAs of Comparative Example 2 have a weak absorption band at 400-800nm, and the band gap absorption edge of the B-TNTAs of Comparative Example 1 has a slight red shift, and the light absorption ability is weak. However, the F / B-TNTAs in Example 1 show strong light absorption ability in the entire visible light band, among which BiOBr and Fe 3+ The electron transition between the conduction band (CB) is one of the influencing factors.

[0075] pass Figure 5 As can be seen, the F / B-TNTAs of Example 1 exhibited stronger catalytic activity in photoelectrocatalysis, achieving 99.2% and 97.6% efficient degradation of EE2 and CAP, respectively. The performance of EE2 degradation by either photocatalysis or electrocatalysis alone was inferior to that of photoelectrocatalysis, as CAP degradation primarily relied on the electrochemical reduction of the photocathode.

[0076] In summary, the present invention prepares a TiO2 nanoarray composite electrode with an angle formed between the Fe / BiOBr sheet and the TiO2 nanotubes, which effectively enhances the light absorption capacity of the TiO2 nanotubes and improves the catalytic activity of the composite electrode. Ultimately, the composite electrode has a high efficiency in treating new pollutants and can achieve efficient degradation of both EE2 and CAP.

[0077] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a TiO2 nano-array composite electrode, characterized by: The preparation method comprises the following steps: (1) Ultrasonic cleaning of titanium foil and then polishing; (2) using the titanium foil treated in step (1) as an anode and the titanium plate as a cathode to perform electrolytic oxidation, washing the oxidized titanium foil, and then annealing to obtain anatase TiO2 nanotubes; (3) dissolving bismuth nitrate pentahydrate and potassium bromide in ethylene glycol and stirring, and then adding ferric nitrate nonahydrate to obtain a Fe / BiOBr precursor solution; (4) hydrothermally reacting the Fe / BiOBr precursor solution obtained in step (3) with the anatase TiO2 nanotubes obtained in step (2), and then washing and drying the reaction product to obtain a TiO2 nanoarray composite electrode.

2. The preparation method according to claim 1, wherein: In the step (1), the titanium foil is ultrasonically cleaned using acetone, anhydrous ethanol, and ultrapure water in sequence, with each washing lasting 15 to 30 minutes.

3. The preparation method according to claim 1, wherein: In the step (1), the polishing liquid used for polishing is prepared from hydrofluoric acid, nitric acid and water in a volume ratio of HF:HNO3:H2O=1:4:5, and the polishing time is 30 to 60 seconds.

4. The preparation method according to claim 1, wherein: In the step (2), the electrolyte used for electrolytic oxidation is prepared from water, ethylene glycol, and ammonium fluoride. First, water and ethylene glycol are mixed in a volume ratio of H2O:C2H6O2=1:49 to obtain a solvent, and then ammonium fluoride is added to the solvent in a mass ratio of NH4F:solvent=1:399 to prepare the electrolyte.

5. The preparation method according to claim 1, wherein: In the step (2), the electrolytic oxidation voltage is 30 V, and the electrolytic oxidation time is 1 to 3 hours.

6. The preparation method according to claim 1, wherein: In the step (2), the annealing temperature is 450-550° C., the heating rate is 3-7° C. / min, and the holding time is 1-3 h.

7. The preparation method according to claim 1, wherein: In the step (3), the amounts of bismuth nitrate pentahydrate and potassium bromide are equal, the solid-liquid ratios of bismuth nitrate pentahydrate and potassium bromide to ethylene glycol are both 1-3 mmol:500 ml, and the solid-liquid ratio of ferric nitrate nonahydrate to ethylene glycol is 5-7 mmol:5000 ml.

8. The preparation method according to claim 1, wherein: In the step (3), after adding ferric nitrate nonahydrate, stirring is continued for 1 to 3 hours to obtain a Fe / BiOBr precursor solution.

9. The preparation method according to claim 1, wherein: In the step (4), the hydrothermal reaction temperature is 100-200° C., and the reaction time is 9-11 hours.

10. Use of the TiO2 nanoarray composite electrode prepared by the preparation method according to any one of claims 1 to 9 in the degradation of 17α-ethynylestradiol and chloramphenicol.

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