Titanium fluoride-doped iron oxide photoanode, preparation method and application thereof

Abstract

This invention discloses a titanium fluoride-doped iron oxide photoanode, its preparation method, and its application, belonging to the field of photoelectrochemical technology. The preparation steps of the titanium fluoride-doped iron oxide photoanode are as follows: Conductive glass is placed in a mixture of iron and titanium sources, subjected to a hydrothermal reaction, and calcined to obtain a Ti-Fe₂O₃ photoanode; the Ti-Fe₂O₃ photoanode is then fluorinated to obtain the titanium fluoride-doped iron oxide photoanode. The titanium fluoride-doped iron oxide photoanode prepared by this invention can effectively detect voltage in glucose solutions of different concentrations using photoelectric detection technology. Furthermore, the titanium fluoride-doped iron oxide photoanode exhibits visible light response, higher photoelectric conversion efficiency, higher catalytic oxidation efficiency for organic matter, and long-term operational stability. The titanium fluoride-doped iron oxide photoanode prepared by this invention provides a simple analytical method for the effective voltage detection of glucose.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrochemical technology, and more specifically relates to a titanium fluoride-doped iron oxide photoanode, its preparation method, and its application. Background Technology

[0002] In recent years, photoelectrocatalysis has become an emerging technology due to its advantages such as rapid response and environmental friendliness. Its core lies in using photoanode materials to excite electron-hole pairs under light, and converting the organic matter content into a measurable current signal through redox reactions.

[0003] In recent years, the application of photoelectrocatalysis technology in the detection of chemical oxygen demand (COD) has become a research hotspot. Compared with traditional enzyme sensors, photoelectrochemical sensors employ an enzyme-free catalytic mechanism, offering advantages such as strong anti-interference capabilities and good stability. In environmental monitoring, COD is used to measure the total amount of organic pollutants in water bodies, and glucose, as a model of easily degradable biomass pollutants (such as food wastewater and fermentation wastewater), can indirectly reflect COD levels through its detection. However, traditional enzyme sensors for glucose detection are susceptible to environmental interference and exhibit poor stability. In contrast, photoelectrochemical sensors, by directly detecting glucose, not only simplify the detection process but also significantly improve the reliability and long-term stability of the detection.

[0004] However, existing photoelectrochemical sensors suffer from problems such as insufficient light absorption, rapid carrier recombination, poor corrosion resistance, and low selectivity in glucose oxidation. This invention addresses these issues. Summary of the Invention

[0005] The purpose of this invention is to provide a titanium fluoride-doped iron oxide photoanode, its preparation method, and its application, to solve the problems existing in the prior art. The titanium fluoride-doped iron oxide photoanode prepared by this invention improves conductivity and charge separation efficiency through fluorine doping, broadens light absorption by optimizing the bandgap through titanium doping, enhances stability through a composite structure, and improves glucose oxidation selectivity through surface fluorine modulation, effectively improving sensor performance. This invention enables the preparation of a photoanodes with visible light response, higher photoelectric conversion efficiency, organic matter catalytic oxidation efficiency, and long-term working stability, and their application in glucose detection, providing a new approach for water pollution monitoring.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of this invention is to provide a method for preparing a titanium fluoride-doped iron oxide photoanode, comprising the following steps:

[0008] Conductive glass is placed in a mixture of iron and titanium sources for hydrothermal reaction and calcination to obtain a Ti-Fe2O3 photoanode; the Ti-Fe2O3 photoanode is then fluorinated to obtain a titanium fluoride-doped iron oxide photoanode.

[0009] Preferably, the conductive glass comprises FTO, ITO, or AZO; the iron source comprises one or more of ferric chloride, ferric sulfate, and ferric nitrate; the titanium source comprises one or more of titanium trichloride, titanium sulfate, tetrabutyl titanate, and isopropyl titanate; the preparation steps of the mixture of iron source and titanium source include: first dissolving the iron source in water to obtain an iron source solution, and then adding a titanium source solution to the iron source solution; the concentration of the iron source solution is 0.1–0.3 M; the volume ratio of the iron source solution to the titanium source solution is 4500–5500:1.

[0010] Preferably, the hydrothermal reaction is carried out at a temperature of 90–150°C for 2–4 hours.

[0011] Preferably, the calcination temperature is 650–750°C and the time is 5–15 min.

[0012] Preferably, the fluorination treatment includes: placing the Ti-Fe2O3 photoanode in a solution containing a fluorine source for 10-15 hours.

[0013] Preferably, the fluorine source includes sodium fluoride and / or ammonium fluoride; the concentration of the fluorine-containing solution is 0.1–1 M.

[0014] The titanium fluoride-doped iron oxide photoanode of this invention uses FTO conductive glass as a substrate. A Ti-FeOOH thin film is obtained through a hydrothermal reaction, followed by calcination to obtain a Ti-Fe2O3 photoanode. The titanium fluoride-doped iron oxide photoanode is then prepared through a surface fluorination reaction on the Ti-Fe2O3 photoanode. The titanium fluoride-doped iron oxide photoanode prepared by this invention can effectively detect voltage in glucose solutions of different concentrations using photoelectric detection technology. Furthermore, the titanium fluoride-doped iron oxide photoanode exhibits visible light response, higher photoelectric conversion efficiency, high catalytic oxidation efficiency of organic matter, and long-term operational stability. The titanium fluoride-doped iron oxide photoanode prepared by this invention provides a simple analytical method for effective voltage detection of glucose. Moreover, the preparation method is simple and safe to operate, uses readily available materials, and can be mass-produced.

[0015] The mechanism by which the titanium fluoride-doped iron oxide photoanode of the present invention achieves the above-mentioned technical effects is as follows:

[0016] A titanium fluoride-doped iron oxide photoanode was fabricated using FTO conductive glass as a substrate. Titanium doping modulates the Fe2O3 band structure, narrowing the band gap and broadening visible light absorption. Surface fluorine treatment reduces surface state density and carrier recombination by replacing oxygen sites with fluoride ions, while simultaneously adjusting the conduction band bottom position to optimize charge separation efficiency in the visible light region. The synergistic effect of titanium and fluorine, with the electronegativity of fluorine working in conjunction with the hydroxylation sites generated by titanium, forms a built-in electric field that accelerates photogenerated charge separation, reduces detection energy consumption, and enhances the adsorption and oxidation efficiency of organic matter (such as glucose). This enables highly efficient identification of low-concentration glucose, which not only promotes the application of high-performance photoanode materials in glucose detection but also provides a new technical approach for water pollution monitoring, possessing significant scientific and practical value. Furthermore, the order of preparing the Ti-Fe2O3 photoanode before fluorination is irreversible. If fluorination is performed first, a fluoride layer will form on the iron oxide surface, acting as a barrier to prevent titanium ions from entering the internal crystal lattice. This results in low titanium doping levels, which are only adhering to the surface and cannot effectively optimize the band structure. At the same time, the fluoride layer will disrupt the bonding stability between titanium and iron oxide and reduce the hydroxylation sites that can adsorb glucose, causing a significant decrease in photoanode performance. In other words, if fluorination is performed before loading titanium, the fluoride passivation layer will hinder uniform titanium loading, leading to the failure of band gap optimization, insufficient carrier concentration, increased charge recombination, reduced active sites, a significant decrease in photoanode stability, and deterioration of glucose detection performance.

[0017] This invention limits the concentration of the iron source solution to 0.1–0.3 M, and the volume ratio of the iron source solution to the titanium source solution to 4500–5500:1. When the concentration of the iron source is less than 0.1 M, the Ti-FeOOH film generated by the hydrothermal reaction is too thin, resulting in decreased conductivity; when the concentration of the iron source is greater than 0.3 M, the Ti-FeOOH film generated by the hydrothermal reaction is too thick, also resulting in decreased conductivity. When the amount of titanium source added is insufficient, the titanium content in the Ti-FeOOH film generated by the hydrothermal reaction is too low, leading to poor performance of the calcined iron oxide; when the amount of titanium source added is excessive, the titanium content in the Ti-FeOOH film generated by the hydrothermal reaction is too high, resulting in titanium oxide doping in the calcined iron oxide, which also affects performance.

[0018] This invention limits the hydrothermal reaction temperature to 90–150°C and the reaction time to 2–4 hours. When the reaction temperature is below 90°C, iron oxide cannot grow onto the conductive glass via the hydrothermal reaction; when the reaction temperature is above 150°C, the Ti-FeOOH film generated by the hydrothermal reaction is too thick, affecting the performance of the Ti-Fe2O3 photoanode; when the reaction time is less than 2 hours, the Ti-FeOOH film generated by the hydrothermal reaction is too thin, resulting in decreased conductivity; when the reaction time is greater than 4 hours, the Ti-FeOOH film generated by the hydrothermal reaction is too thick, also leading to decreased conductivity.

[0019] The present invention specifies the calcination temperature as 650–750°C and the retention time as 5–15 min. When the calcination temperature is below 650°C, the crystallinity of Fe2O3 is insufficient; when the calcination temperature is above 750°C, the grains grow excessively, the specific surface area decreases, and the light absorption efficiency decreases. When the retention time is less than 5 min, the precursor decomposition will be incomplete; when the retention time is more than 15 min, the carrier concentration will decrease due to excessive repair of lattice defects.

[0020] This invention limits the concentration of the sodium fluoride solution in the fluorination reaction to 0.1–1 M and the fluorination time to 10–15 h. When the concentration of the sodium fluoride solution is below 0.1 M, fluorine doping is insufficient, and the increase in carrier concentration is limited. When the concentration of the sodium fluoride solution is above 1 M, a fluoride transport barrier is formed on the photoanode surface. When the fluorination time is less than 10 h, fluorine penetration is insufficient and adsorption stability is poor. When the fluorination time is longer than 15 h, excessive fluorine penetration disrupts the lattice periodicity, all of which lead to a deterioration in light absorption and charge separation efficiency.

[0021] The second technical solution of the present invention provides a titanium fluoride-doped iron oxide photoanode prepared by the above preparation method.

[0022] The third technical solution of the present invention provides the application of the above-mentioned titanium fluoride-doped iron oxide photoanode in the preparation of photoelectrochemical sensors.

[0023] The fourth technical solution of the present invention provides a photoelectrochemical sensor, wherein the photoelectrochemical sensor includes the above-mentioned titanium fluoride-doped iron oxide photoanode.

[0024] Fifth technical solution of the present invention: to provide the application of the above-mentioned photoelectrochemical sensor in the field of chemical oxygen demand detection.

[0025] The present invention discloses the following technical effects:

[0026] 1. The titanium fluoride-doped iron oxide photoanode prepared by this invention can effectively detect voltage in glucose solutions of different concentrations by combining photoelectric detection technology. Furthermore, the titanium fluoride-doped iron oxide photoanode has visible light response, higher photoelectric conversion efficiency, and higher organic matter catalytic oxidation efficiency.

[0027] 2. The titanium fluoride-doped iron oxide photoanode prepared by this invention provides a simple analytical method for effective voltage detection of glucose.

[0028] 3. The preparation method of the titanium fluoride-doped iron oxide photoanode described in this invention is simple and safe to operate, the materials are readily available, and it can achieve large-scale production. Attached Figure Description

[0029] Figure 1 The image shows a scanning electron microscope (SEM) image of the Ti-Fe2O3 photoanode prepared in Example 1.

[0030] Figure 2 The image is a scanning electron microscope (SEM) image of the titanium fluoride-doped iron oxide photoanode prepared in Example 1.

[0031] Figure 3 This is a transmission electron microscope (TEM) image of the titanium fluoride-doped iron oxide photoanode prepared in Example 1;

[0032] Figure 4 The image shows the energy dispersive spectroscopy (EDS) analysis of the titanium fluoride-doped iron oxide photoanode prepared in Example 1.

[0033] Figure 5 X-ray diffraction (XRD) patterns of the Ti-Fe2O3 photoanode and the titanium fluoride-doped iron oxide photoanode prepared in Example 1;

[0034] Figure 6 The following are the Fourier Transform Infrared (FT-IR) spectra of the Ti-Fe2O3 photoanode and the titanium fluoride-doped iron oxide photoanode prepared in Example 1.

[0035] Figure 7 X-ray photoelectron spectroscopy (XPS) images of the Ti-Fe2O3 photoanode and the titanium fluoride-doped iron oxide photoanode prepared in Example 1;

[0036] Figure 8 Linear scan voltammetry curve of Ti-Fe2O3 photoanode for application test 1;

[0037] Figure 9 Linear scan voltammetry curve of titanium fluoride-doped iron oxide photoanode for application test 1;

[0038] Figure 10 Linear scan voltammetry curves of the Ti-Fe2O3 photoanode used in test 2;

[0039] Figure 11 Linear scan voltammetry curves of the titanium fluoride-doped iron oxide photoanode used in application test 2;

[0040] Figure 12 The UV-Vis absorption spectra of the Ti-Fe2O3 photoanode and the titanium fluoride-doped iron oxide photoanode in Example 1 are shown.

[0041] Figure 13 The solar irradiance spectra (ASTM G173-03) of the Ti-Fe2O3 photoanode and the titanium fluoride-doped iron oxide photoanode in Example 1, as well as the corresponding photocurrent densities (J / L) of the materials, are shown. abs )picture;

[0042] Figure 14Linear scan voltammetric curves of Ti-Fe2O3 photoanode and titanium fluoride-doped iron oxide photoanode in application test 3;

[0043] Figure 15 To test the charge separation efficiency (Φ) of Ti-Fe2O3 photoanode and titanium fluoride-doped iron oxide photoanode in application test 3. Sep )picture.

[0044] In the above figures, F-Ti-Fe2O3 represents titanium fluoride-doped iron oxide photoanodes. Detailed Implementation

[0045] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0046] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0047] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0048] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0049] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0050] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0051] Unless otherwise specified, all raw materials used in this invention are commercially available products, and the source of these commercially available products does not affect the technical effect of this invention.

[0052] Unless otherwise specified, the room temperature involved in this invention is 25±5℃.

[0053] Example 1

[0054] This embodiment provides a method for preparing a titanium fluoride-doped iron oxide photoanode, the specific steps of which are as follows:

[0055] (1) Dissolve ferric chloride in water to form solution A, wherein the concentration of ferric chloride is 0.15M; and add 12μL of titanium trichloride solution (15.0~20.0% TiCl3 basis in 30% HCl) to solution A. The volume ratio of titanium trichloride solution to solution A is 1:5000. After mixing evenly, electrolyte A is obtained.

[0056] (2) Take a piece of 200×150mm FTO conductive glass and cut it into 20×30mm dimensions using a glass cutting table. Wash it sequentially with acetone, ethanol, and deionized water using ultrasonic cleaning for 15 minutes. After washing, add ethanol and store for later use. Use a multi-point pen to identify the conductive surface of the FTO conductive glass as the front side. Use polyimide tape to partially cover the front side of the FTO conductive glass and also cover the back side.

[0057] (3) Transfer electrolyte A to the reaction vessel, and immerse the attached FTO conductive glass face down in electrolyte A. Then place the reaction vessel in a vacuum drying oven for a water bath reaction at 100°C for 3 hours. After the water bath, a light yellow film forms on the surface of the FTO conductive glass. Remove the polyimide tape, rinse, and dry to obtain FTO conductive glass with a yellow film.

[0058] On a high-temperature resistant corundum sheet, FTO conductive glass with a yellow film measuring 20×30mm is placed, with a distance of 3-5mm between the sheets. Then, the corundum sheet is slowly placed in a muffle furnace for a single calcination at 700℃ for 10 minutes. After the muffle furnace cools to room temperature, the corundum sheet is slowly removed, and the calcined FTO conductive glass is taken out. The surface of the FTO conductive glass is intact and uniform, and it is bright red. After rinsing and drying, Ti-Fe2O3 photoanode is obtained.

[0059] (4) Dissolve sodium fluoride in water to form an electrolyte B with a concentration of 1M. Place the prepared Ti-Fe2O3 photoanode in a petri dish in sequence, pour in electrolyte B to immerse the Ti-Fe2O3 photoanode surface, soak for 12 hours, wash with deionized water and dry to obtain a titanium fluoride doped iron oxide photoanode.

[0060] The scanning electron microscope (SEM) image of the Ti-Fe2O3 photoanode prepared in Example 1 is shown below. Figure 1 As shown, by Figure 1 It can be seen that Ti-Fe2O3 is a vertically grown nanorod with a length of 100-200 nm.

[0061] The scanning electron microscope (SEM) image of the titanium fluoride-doped iron oxide photoanode prepared in Example 1 is shown below. Figure 2 As shown, by Figure 2 It can be seen that F-Ti-Fe2O3 is a vertically grown nanorod with a length of 100-200 nm.

[0062] Transmission electron microscopy (TEM) image of the titanium fluoride-doped iron oxide photoanode prepared in Example 1 is shown below. Figure 3 As shown, by Figure 3 It can be seen that the lattice spacing of Ti-Fe2O3 is 0.272 nm, corresponding to the 024 crystal plane. The amorphous film formed by fluorination is separated from Ti-Fe2O3 by a short white dashed line, thus confirming the successful preparation of titanium fluoride-doped iron oxide photoanode.

[0063] The energy dispersive spectroscopy (EDS) image of the photoanode prepared in Example 1, which is shown below. Figure 4 As shown, by Figure 4 It can be seen that Fe, O, Ti and F elements are all uniformly distributed on the sample surface, confirming the successful preparation of titanium fluoride-doped iron oxide photoanode.

[0064] The X-ray diffraction (XRD) pattern of the Ti-Fe2O3 and titanium fluoride-doped iron oxide photoanode prepared in Example 1 is shown below. Figure 5 As shown, by Figure 5 It can be seen that since fluorination forms an amorphous thin film on the Ti-Fe2O3 surface, the titanium fluoride-doped iron oxide photoanode does not have XRD characteristic peaks.

[0065] The Fourier transform infrared (FT-IR) spectra of the Ti-Fe₂O₃ and titanium fluoride-doped iron oxide photoanodes prepared in Example 1 are shown below. Figure 6 As shown, by Figure 6 It can be known that 500cm -1 750cm -1 The characteristic peak of Ti-Fe2O3 nanorods is 1641 cm⁻¹. -1 3434cm -1 These are characteristic peaks that appear after fluorination.

[0066] The X-ray photoelectron spectroscopy (XPS) spectra of the Ti-Fe2O3 and titanium fluoride-doped iron oxide photoanodes prepared in Example 1 are shown below. Figure 7 As shown, by Figure 7It can be seen that it contains characteristic element peaks of Ti-Fe2O3 and fluoride, confirming the successful preparation of Ti-Fe2O3 and titanium fluoride-doped iron oxide photoanodes.

[0067] Application Test 1

[0068] Linear sweep voltammetry was selected. Under illumination with a lamp on, the Ti-Fe₂O₃ photoanode prepared in Example 1 was used as the working electrode, a platinum mesh as the counter electrode, and an Ag / AgCl electrode as the reference electrode. The electrolyte consisted of glucose solutions of different concentrations prepared on a 0.1M Na₂SO₄ base. The initial potential was 0.8V vs. RHE, the termination potential was 1.8V vs. RHE, and the scan rate was 0.025V / s. -1 The sampling interval was 0.001V, the settling time was 1.5s, and the sensitivity was 1×10⁻⁶. -3 A. The photocurrent of a Ti-Fe2O3 photoanode in glucose solutions with concentrations of 0 M, 0.1 mM, 1 mM, 10 mM, 100 mM, and 1000 mM was tested as a function of potential, and the results were obtained. Figure 8 Linear scan voltammetry curve.

[0069] Linear sweep voltammetry was selected. Under illumination with a light source, the titanium fluoride-doped iron oxide photoanode prepared in Example 1 was used as the working electrode, a platinum mesh as the counter electrode, and an Ag / AgCl electrode as the reference electrode. The electrolyte consisted of glucose solutions of different concentrations prepared on a 0.1M Na₂SO₄ substrate. The initial potential was 0.8V vs. RHE, the termination potential was 1.8V vs. RHE, and the scan rate was 0.025V / s. -1 The sampling interval was 0.001V, the settling time was 1.5s, and the sensitivity was 1×10⁻⁶. -3 A. The photocurrent versus potential variation of a titanium fluoride-doped iron oxide photoanode in glucose solutions of concentrations of 0 M, 0.1 mM, 1 mM, 10 mM, 100 mM, and 1000 mM was tested, and the results were obtained. Figure 9 Linear scan voltammetry curve.

[0070] according to Figure 8 and Figure 9 It can be seen that the current density of the titanium fluoride-doped iron oxide photoanode is 1.41 mA / cm² at 1.8 V vs. RHE. 2 It exhibits a lower electrochemical signal in pure water (0.1 M Na2SO4) and is significantly superior to the Ti-Fe2O3 photoanode (1.25 mA / cm²). 2 It possesses excellent detection signal and better detection gradient.

[0071] Application Test 2

[0072] To further verify the performance of titanium fluoride-doped iron oxide photoanodes and evaluate their applicability to real-world pollutants, this invention also tested potassium hydrogen phthalate solution. Potassium hydrogen phthalate contains a benzene ring structure, making it more difficult to oxidize than glucose, thus allowing for the examination of the responsiveness of titanium fluoride-doped iron oxide photoanodes to complex organic compounds. Furthermore, industrial wastewater often contains aromatic organic compounds, and potassium hydrogen phthalate more closely matches the COD contribution characteristics of such samples, further enabling the assessment of the applicability of titanium fluoride-doped iron oxide photoanodes to real-world pollutants. Specifically:

[0073] Linear scanning voltammetry was selected. Under illumination with a lamp, the Ti-Fe₂O₃ photoanode prepared in Example 1 was used as the working electrode, a platinum mesh as the counter electrode, and an Ag / AgCl electrode as the reference electrode. The electrolyte was potassium hydrogen phthalate solution of different concentrations prepared on a 0.1M Na₂SO₄ substrate. The initial potential was 0.8V vs. RHE, the termination potential was 1.8V vs. RHE, and the scan rate was 0.025V / s. -1 The sampling interval was 0.001V, the settling time was 1.5s, and the sensitivity was 1×10⁻⁶. -3 A. The photocurrent of a Ti-Fe₂O₃ photoanode in potassium hydrogen phthalate solutions with concentrations of 0 M, 0.1 mM, 1 mM, 10 mM, 100 mM, and 500 mM was tested as a function of potential, and the results were obtained. Figure 10 Linear scan voltammetry curve.

[0074] Linear sweep voltammetry was selected. Under illumination with a lamp, the titanium fluoride-doped iron oxide photoanode prepared in Example 1 was used as the working electrode, a platinum mesh as the counter electrode, and an Ag / AgCl electrode as the reference electrode. The electrolyte was potassium hydrogen phthalate solution of different concentrations prepared on a 0.1M Na₂SO₄ substrate. The initial potential was 0.8V vs. RHE, the termination potential was 1.8V vs. RHE, and the scan rate was 0.025V / s. -1 The sampling interval was 0.001V, the settling time was 1.5s, and the sensitivity was 1×10⁻⁶. -3 A. The photocurrent of a Ti-Fe2O3 photoanode as a function of potential was tested at potassium hydrogen phthalate concentrations of 0 M, 0.1 mM, 1 mM, 10 mM, 100 mM, and 500 mM. Figure 11 Linear scan voltammetry curve.

[0075] according to Figure 10 and Figure 11 It can be seen that the current density of the titanium fluoride-doped iron oxide photoanode is 1.40 mA / cm² at 1.8 V vs. RHE. 2 It exhibits a lower electrochemical signal in pure water (0.1 M Na2SO4) and is significantly superior to that of a pure Ti-Fe2O3 photoanode (1.21 mA / cm²).2 It possesses excellent detection signal and better detection gradient.

[0076] Depend on Figures 8-11 It is known that fluorinated titanium fluoride-doped iron oxide photoanodes have better oxidation detection properties and are suitable for COD detection.

[0077] Application Test 3

[0078] Linear scanning voltammetry was selected. Under chopping light, the Ti-Fe2O3 or titanium fluoride-doped iron oxide photoanode prepared in Example 1 was used as the working electrode, a platinum mesh as the counter electrode, and an Ag / AgCl electrode as the reference electrode. The electrolyte was 0.1M Na2SO4 + 0.1M Na2SO3 (hole scavenger). The initial potential was 0.4V vs. RHE, the termination potential was 1.5V vs. RHE, the scan rate was 0.025V / s, the sampling interval was 0.001V, the settling time was 0s, and the sensitivity was 1×10⁻⁶. -3 A. The photocurrent versus potential variation of Ti-Fe2O3 photoanode and titanium fluoride-doped iron oxide photoanode in 0.1M Na2SO4 + 0.1M Na2SO3 was tested, and the results were obtained. Figure 14 Linear scan voltammetry curve.

[0079] Figure 12 The images show the UV-Vis absorption spectra of the Ti-Fe2O3 photoanode and the titanium fluoride-doped iron oxide photoanode in Example 1. Figure 12 It can be seen that titanium fluoride-doped iron oxide photoanodes have better light absorption performance.

[0080] Figure 13 The solar irradiance spectra (ASTM G173-03) of the Ti-Fe2O3 photoanode and the titanium fluoride-doped iron oxide photoanode in Example 1, and the photocurrent density (J) calculated from the ultraviolet-visible absorption spectra of the materials are shown. abs )picture.

[0081] Figure 14 Linear sweep voltammetry curves of Ti-Fe2O3 photoanode and titanium fluoride-doped iron oxide photoanode in application test 3.

[0082] Figure 15 The charge separation efficiency (Φ) was calculated from the linear sweep voltammetry curves of the hole scavengers obtained from the Ti-Fe2O3 photoanode and the titanium fluoride-doped iron oxide photoanode in test 3. Sep )picture.

[0083] Depend on Figures 12-15 It can be seen that the fluorinated titanium fluoride-doped iron oxide photoanode has better light absorption performance and higher J. absThe results demonstrate that the fluorinated titanium fluoride-doped iron oxide photoanode exhibits visible light response and higher photoelectric conversion efficiency. The charge separation efficiency of the fluorinated titanium fluoride-doped iron oxide photoanode is 22.75%, significantly better than that of the Ti-Fe2O3 photoanode (18.21%), confirming its higher charge separation efficiency. High charge separation efficiency can directly reduce the electron-hole recombination rate and improve the catalytic oxidation efficiency of organic matter.

[0084] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0085] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a fluorinated titanium-doped iron oxide photoanode, characterized in that, The preparation method comprises the following steps: placing the conductive glass in a mixed solution of an iron source and a titanium source to perform a hydrothermal reaction, and calcining to obtain a Ti-Fe2O3 photoanode; and performing fluorination treatment on the Ti-Fe2O3 photoanode to obtain the titanium fluoride-doped iron oxide photoanode; the conductive glass comprises FTO, ITO or AZO; the iron source comprises one or more of ferric chloride, iron sulfate and iron nitrate; the titanium source comprises one or more of titanium trichloride, titanium sulfate, tetrabutyl titanate and isopropyl titanate; the preparation step of the mixed solution of the iron source and the titanium source comprises: first dissolving the iron source in water to obtain an iron source solution, and then adding a titanium source solution to the iron source solution; the concentration of the iron source solution is 0.1-0.3M; the volume ratio of the iron source solution to the titanium source solution is 4500-5500:1; the temperature of the hydrothermal reaction is 90-150℃, and the time is 2-4h; the temperature of the calcination is 650-750℃, and the time is 5-15min; the fluorination treatment comprises: placing the Ti-Fe2O3 photoanode in a solution containing a fluorine source for 10-15h; the fluorine source comprises sodium fluoride and / or ammonium fluoride; and the concentration of the solution containing the fluorine source is 0.1-1M. 2.The titanium fluoride-doped iron oxide photoanode prepared by the preparation method of claim 1. 3.The application of the titanium fluoride-doped iron oxide photoanode of claim 2 in preparing a photoelectrochemical sensor.

4. An electrochemical sensor, comprising: The photoelectrochemical sensor comprises the titanium fluoride-doped iron oxide photoanode of claim 2. 5.The application of the photoelectrochemical sensor of claim 4 in the field of chemical oxygen demand detection.

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