Pecod sensor based on hydrogenated tungsten trioxide / titanium dioxide nanometer array and preparation method and application thereof

Abstract

This invention belongs to the field of PECOD sensor technology, specifically relating to a PECOD sensor based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray, its fabrication method, and its applications. This invention attaches a layer of titanium dioxide nanorods to a hydrogenated tungsten trioxide nanoplate film, which not only absorbs a wider range of spectra but also promotes photogenerated electrons under illumination. ‑ -h + The above-mentioned PECOD sensor exhibits higher photocatalytic activity and is simple to prepare. Under illumination, the sensor utilizes light and current to photocatalyze organic matter, enabling the determination of COD in wastewater. This eliminates the need for toxic and corrosive reagents, saving time and reagent costs, and avoiding health risks to testing personnel and secondary environmental pollution.

Description

Technical Field

[0001] This invention relates to the field of PECOD sensor technology, specifically to a PECOD sensor based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray, its preparation method, and its application. Background Technology

[0002] Chemical oxygen demand (COD) refers to the amount of oxidant required to oxidize substances in a water sample under specific conditions. COD is often used as an indicator of the amount of organic matter in water; the lower the COD value, the less polluted the water. Traditional methods typically use strong oxidants such as dichromates or permanganates to oxidize and degrade organic matter in water or wastewater to estimate COD. This method not only suffers from low sensitivity, low accuracy, large sample size, and high cost, but also results in the consumption of large amounts of toxic reagents (such as HgSO4) and corrosive reagents (such as concentrated H2SO4). Therefore, finding a simple and environmentally friendly COD detection method is of practical value.

[0003] Photoelectrocatalytic oxidation can be used to immobilize semiconductor photocatalysts on a conductive substrate as the working electrode, and then combine them with electrocatalytically active materials to form a composite electrode. This composite electrode generates electrons under light excitation. - -h + h generated on the electrode surface + Free radicals such as ·OH oxidize organic matter in solution, while photogenerated e - The oxidized component is reduced by flowing through the external circuit to the opposite electrode, due to e - The unidirectional flow further hindered e - and h + The combination of these components can improve catalytic efficiency. Photoelectric devices based on photoelectrochemical oxidation inherit the advantages of high efficiency and low energy consumption of photocatalysis, and the sensitivity, speed, and miniaturization of electrochemical technology, showing promising prospects in the detection field. However, developing a simple, inexpensive, and sensitive photoelectrode material for detecting COD in water using photoelectrochemical oxidation remains a challenge. Summary of the Invention

[0004] The first objective of this invention is to provide a PECOD sensor based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray to solve at least one of the aforementioned technical problems.

[0005] A second objective of this invention is to provide a method for preparing a PECOD sensor based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray obtained by the above-described preparation method, in order to solve at least one of the aforementioned technical problems.

[0006] A third objective of the present invention is to provide an application of the above-mentioned PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarrays to solve at least one of the above-mentioned technical problems.

[0007] This invention uses glucose as a detection substrate instead of organic pollutants in wastewater for testing.

[0008] According to a first aspect of the present invention, a PECOD sensor based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray is provided, wherein the PECOD sensor comprises a layer of titanium dioxide nanorods attached to a hydrogenated tungsten trioxide nanoplate film.

[0009] The PECOD sensor based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray of the present invention, by attaching a layer of titanium dioxide nanorods to a thin film of hydrogenated tungsten trioxide nanoplates, not only absorbs a wider range of spectra, but also promotes photogenerated electrons under illumination. - -h + Separation results in higher photocatalytic activity.

[0010] In some embodiments, hydrogenated WO3 nanoplate films are prepared by calcining FTO conductive glass on which WO3 nanoplates have grown, cooling it down, and then performing a second calcination treatment in an atmosphere of argon-hydrogen mixed gas. After cooling to room temperature, hydrogenated WO3 nanoplate films are obtained.

[0011] According to a second aspect of the present invention, a method for fabricating a PECOD sensor based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray is provided, the method comprising the following steps:

[0012] S1. Fluorine-doped tin oxide conductive glass is ultrasonically treated with acetone, deionized water, and anhydrous ethanol in sequence. Then, the fluorine-doped tin oxide conductive glass is rinsed with deionized water and dried to obtain a conductive substrate.

[0013] S2. Dissolve sodium tungstate dihydrate in deionized water, slowly add hydrochloric acid solution and stir until a suspension containing a pale yellow flocculent precipitate is obtained. Add ammonium oxalate to the suspension and continue stirring until the suspension becomes clear. Add deionized water and stir to obtain the precursor solution.

[0014] S3. Transfer the precursor solution to the liner of Teflon, place the conductive substrate against the container wall of Teflon with the conductive side facing down into the precursor solution for hydrothermal reaction, cool to room temperature, rinse the first reaction product with deionized water and dry to obtain FTO conductive glass with WO3 nanoplates grown.

[0015] S4. Calcine the FTO conductive glass with WO3 nanoplates grown on it, cool it to room temperature, and then perform a second calcination treatment in an atmosphere of argon-hydrogen mixed gas, cool it to room temperature, and obtain hydrogenated WO3 nanoplate film.

[0016] S5. The hydrogenated WO3 nanoplate film is placed in a mixed solution containing glycerol, anhydrous ethanol and tetrabutyl titanate, and treated at 160-180℃ for 10-12h. After cooling to room temperature, the second reaction product is washed multiple times with deionized water and ethanol, and then calcined after natural drying to obtain the PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray.

[0017] This invention grows tungsten trioxide nanoarrays on FTO conductive glass using a solvothermal method, then hydrogenates the tungsten trioxide through high-temperature calcination, and finally bonds hole-filled titanium dioxide nanorods to the hydrogenated tungsten trioxide using a sol-gel method. The preparation method is simple, and the hydrogenated tungsten trioxide bonds firmly and stably to the FTO conductive glass. Compared to tungsten trioxide nanoarrays, this invention improves the crystallinity of the tungsten trioxide nanosheets through calcination, followed by a second calcination treatment in an argon-hydrogen mixed gas atmosphere to hydrogenate the tungsten trioxide, introducing oxygen vacancies that trap electrons. This not only allows the nanoarrays to absorb a wider range of light, including visible light and part of the ultraviolet light, enhancing the photocatalytic activity of tungsten trioxide, but also promotes photogenerated electrons under illumination. - -h + Separation. Titanium dioxide, as a hole-blocking material, promotes the generation of electrons. - -h + e - The titanium dioxide flows to the counter electrode, while h + The titanium dioxide blocks the flow, thus facilitating the photoelectrocatalytic process. - -h + Separation, at the same time h + It can capture OH groups in water molecules - This process generates free radicals such as ·OH, which promote the oxidation of organic matter in water through photoelectrocatalysis. The photoelectric material prepared by this method has a wide linear range and a low detection limit, enabling rapid detection of COD in water. It is simple to operate and has high sensitivity.

[0018] In some implementations, the ultrasound time in step S1 is 20 minutes.

[0019] In some embodiments, in step S2, during the process of dissolving sodium tungstate dihydrate in deionized water, the amount of sodium tungstate dihydrate used is 0.23–0.46 g, and the amount of deionized water used is 30–60 mL.

[0020] In some embodiments, in step S2, the hydrochloric acid solution can be 10-20 mL of 3 mol / L hydrochloric acid solution, the amount of ammonium oxalate is 0.2-0.4 g, and the amount of deionized water used in the process of adding deionized water to obtain the precursor solution is 30-60 mL.

[0021] In some embodiments, in step S2, the stirring time for slowly adding hydrochloric acid solution while stirring is 5–10 minutes, and the stirring time for adding ammonium oxalate to the suspension while continuing to stir is 8–12 minutes. Stirring is then applied to the solution containing WO4. 2- Hydrochloric acid solution is slowly added to the aqueous solution. Due to the precipitation of tungstic acid, the solution gradually becomes a suspension containing a pale yellow flocculent precipitate. Then, ammonium oxalate is added to the suspension. Ammonium oxalate acts as a directing agent to control the growth of tungstic acid crystals, so that the grown tungstic acid crystals have a nanosheet structure.

[0022] In some embodiments, in step S3, the hydrothermal reaction temperature is 120–140°C and the reaction time is 10–11 h; the drying process is to keep the product in an oven at 60–70°C for 1–2 h.

[0023] In some embodiments, the method for calcining the FTO conductive glass with WO3 nanoplatelets grown in step S4 can be to calcine it in a muffle furnace at a calcination temperature of 450-460°C and a heating rate of 4-5°C / min for 1-2 hours.

[0024] In some embodiments, the second calcination treatment in step S4 can be carried out by calcining in a tube furnace at a calcination temperature of 250-350°C and a heating rate of 2-3°C / min for 2-3 hours.

[0025] In some embodiments, in step S4, the volume ratio of argon to hydrogen in the argon-hydrogen mixture can be 92:8. Here, argon acts as an inert gas for protection, while hydrogen acts as a reducing agent to hydrogenate the FTO conductive glass on which WO3 nanoplatelets have been grown.

[0026] In some embodiments, in step S5, the volume ratio of glycerol, anhydrous ethanol and tetrabutyl titanate in the mixed solution is (1-10):(20-30):(0.3-0.5).

[0027] In some embodiments, in step S5, the calcination process is carried out at 400-450°C for 2-3 hours.

[0028] In step S1 of the present invention, there are no requirements on the size of the conductive substrate; it is sufficient to place the conductive substrate against the container wall of the Teflon.

[0029] In step S3 of the present invention, there is no requirement for the amount of precursor solution used; it is sufficient to place the conductive substrate with the conductive side facing down into the precursor solution for hydrothermal reaction.

[0030] According to a third aspect of the present invention, an application is provided for a PECOD sensor based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray prepared by the above preparation method, which can be used to detect COD in wastewater.

[0031] The PECOD sensor prepared by the method of this invention can be used to detect COD in wastewater. The COD value can be estimated by the linear relationship between the net photocurrent value and the theoretical COD. The entire detection process does not require the addition of toxic or corrosive reagents, and it is simple to operate and highly sensitive.

[0032] The beneficial effects of this invention include:

[0033] (1) In this invention, hydrogenated tungsten trioxide nanoarrays are grown on a conductive substrate by a solvothermal method and a high-temperature calcination method, and then holed titanium dioxide nanorods are bonded to hydrogenated tungsten trioxide by a sol-gel method. The preparation method is simple, and the hydrogenated tungsten trioxide is firmly bonded to the conductive substrate with good stability.

[0034] (2) The tungsten trioxide of this invention, after hydrogenation to introduce oxygen vacancies to capture electrons, not only absorbs a wider range of spectra, including visible light and part of ultraviolet light, but also promotes photogenerated electrons under illumination. - -h + Separation; titanium dioxide, as a hole-blocking material, promotes the generation of e. - -h + e - The titanium dioxide flows to the counter electrode, while h + The titanium dioxide blocks the flow, thus facilitating the photoelectrocatalytic process. - -h + Separation, at the same time h + It can capture OH groups in water molecules - This process generates free radicals such as ·OH, thereby promoting the oxidation of organic matter in water through photoelectrocatalysis. The photoelectric material prepared by this method exhibits a wide linear range and a low detection limit, enabling rapid detection of COD in water.

[0035] (3) Compared with traditional methods for detecting COD in wastewater, the PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray of this invention, when applied to detect COD in wastewater, utilizes photoelectrocatalytic oxidation to oxidize and degrade organic matter present in the water or wastewater. The COD value can be estimated through the linear relationship between net photocurrent and theoretical COD. The operation is simple and highly sensitive. The entire process does not require the use of toxic or corrosive reagents, which not only saves time and reagent costs but also avoids impacting the health of testing personnel and causing secondary pollution to the environment. Attached Figure Description

[0036] Figure 1 These are magnified scanning electron microscope images of the products prepared in different steps of Example 1 of the present invention. Figure 1 (a) is a scanning electron microscope image of the hydrogenated WO3 nanoplate film prepared in steps (1)-(4) of Example 1 of the present invention; Figure 1 (b) is a scanning electron microscope image of titanium dioxide on a PECOD sensor based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray;

[0037] Figure 2 The image shows a scanning electron microscope image of the tungsten trioxide / titanium dioxide array on the PECOD sensor based on the tungsten trioxide / titanium dioxide nanoarray prepared in Example 1 of this invention.

[0038] Figure 3 Linear scanning voltammogram of the PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray prepared in Example 1 of the present invention under light and dark conditions;

[0039] Figure 4 The current response diagram of the PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray prepared in Example 1 of the present invention with solutions of different glucose concentrations;

[0040] Figure 5 The PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray prepared in Example 1 of this invention and the photoelectrodes prepared in Comparative Examples 1-3 are shown in the graphs of net photocurrent versus glucose concentration with solutions of different glucose concentrations.

[0041] Figure 6 For the present invention Figure 5 The linear relationship between net photocurrent and theoretical COD obtained from data calculation is plotted. Detailed Implementation

[0042] The present invention will now be described in further detail with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto. The raw materials and reagents involved in the following embodiments are all commercially available.

[0043] In the following embodiments, the fluorine-doped tin oxide conductive glass is cut into 2×5cm pieces. 2 Blocky.

[0044] Example 1

[0045] This embodiment provides a method for fabricating a PECOD sensor based on a tungsten trioxide / titanium dioxide nanoarray, including the following steps:

[0046] (1) The fluorine-doped tin oxide conductive glass was ultrasonically treated with acetone, deionized water and anhydrous ethanol for 20 min each, then rinsed with deionized water and dried in an oven to obtain a conductive substrate, which was then stored for later use.

[0047] (2) Dissolve 0.23g sodium tungstate dihydrate in 30mL of deionized water, slowly add 10mL of 3mol / L hydrochloric acid solution and stir for a period of time until a suspension containing a pale yellow flocculent precipitate is obtained. Then add 0.2g ammonium oxalate to the suspension and continue stirring for 10min until the suspension becomes clear. Then add 30mL of deionized water and stir for 10min to obtain the precursor solution.

[0048] (3) Take 30 mL of precursor solution and transfer it to a 50 mL Teflon liner. Place the conductive substrate against the Teflon container wall with the conductive side facing down in the precursor solution. Perform a hydrothermal reaction at 120 °C for 10 h. Cool to room temperature and repeatedly wash the conductive substrate containing the tungsten trioxide nanoarray with deionized water and ethanol several times to obtain the first reaction product. Dry it in a constant temperature oven for 1 h to obtain FTO conductive glass with WO3 nanoplates grown on it.

[0049] (4) The FTO conductive glass with WO3 nanoplates grown on it was first placed in a muffle furnace at 450℃ and a heating rate of 5℃ / min for 1h. After cooling to room temperature, it was transferred to a high-temperature resistant crucible boat and placed in a tube furnace with a gas atmosphere containing argon and hydrogen. The second calcination treatment was carried out in the tube furnace at 250℃ and a heating rate of 2℃ / min for 2h. After cooling to room temperature, hydrogenated WO3 nanoplate film was obtained.

[0050] (5) The hydrogenated WO3 nanoplate film was placed in a mixed solution containing 5 mL glycerol, 25 mL anhydrous ethanol and 300 μL tetrabutyl titanate and treated at 180 °C for 10 h. After cooling to room temperature, the second reaction product was washed multiple times with deionized water and ethanol. After natural drying, it was calcined in a muffle furnace at 400 °C for 3 h to obtain the PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray.

[0051] The surface morphology of tungsten trioxide and titanium dioxide on the PECOD sensor based on the prepared tungsten trioxide / titanium dioxide nanoarray was observed using scanning electron microscopy. The results are as follows: Figure 1 and Figure 2 As shown, where Figure 1 (a) is a scanning electron microscope image of the hydrogenated WO3 nanoplate film prepared in steps (1)-(4) of Example 1 of the present invention; Figure 1 (b) is a scanning electron microscope image of titanium dioxide on the PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray prepared in Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the tungsten trioxide / titanium dioxide array on the PECOD sensor prepared in Example 1 of this invention. Figure 1 (a) It can be seen that the growth and distribution of the tungsten trioxide nanoarray on the FTO conductive glass are relatively uniform, and the surface morphology of the tungsten trioxide after step (4) is nanosheet-like; from Figure 1 (b) It can be seen that after step (5), titanium dioxide is loaded onto tungsten trioxide in the form of nanorods; Figure 2 and Figure 1 The comparison shows that the titanium dioxide nanorods are relatively uniformly covered on the original smooth surface of the tungsten trioxide array, indicating that the tungsten trioxide / titanium dioxide nanoarray was successfully synthesized on a conductive substrate by the sol-gel method.

[0052] Example 2

[0053] This embodiment provides a method for fabricating a PECOD sensor based on a tungsten trioxide / titanium dioxide nanoarray, including the following steps:

[0054] (1) The fluorine-doped tin oxide conductive glass was ultrasonically treated with acetone, deionized water and anhydrous ethanol for 20 min each, then rinsed with deionized water and dried in an oven to obtain a conductive substrate, which was then stored for later use.

[0055] (2) Dissolve 0.46g sodium tungstate dihydrate in 30mL of deionized water, slowly add 10mL of 3mol / L hydrochloric acid solution and stir for a period of time until a suspension containing a pale yellow flocculent precipitate is obtained. Then add 0.4g ammonium oxalate to the suspension and continue stirring for 10min until the suspension becomes clear. Then add 30mL of deionized water and stir for 10min to obtain the precursor solution.

[0056] (3) Take 30 mL of precursor solution and transfer it to a 50 mL Teflon liner. Place the conductive substrate against the Teflon container wall with the conductive side facing down in the precursor solution. Perform a hydrothermal reaction at 120 °C for 10 h. Cool to room temperature and wash the first reaction product several times with deionized water and ethanol. Dry in a constant temperature oven for 1 h to obtain FTO conductive glass with WO3 nanoplates grown on it.

[0057] (4) The FTO conductive glass with WO3 nanoplates was first placed in a muffle furnace at 400℃ and a heating rate of 5℃ / min for 1h. After the conductive substrate containing hydrogenated tungsten trioxide nanoarray was cooled to room temperature, the FTO conductive glass with WO3 nanoplates was transferred to a high-temperature resistant crucible boat and placed in a tube furnace with a gas atmosphere containing argon and hydrogen. The second calcination treatment was carried out in the tube furnace at 350℃ and a heating rate of 3℃ / min for 2h. After cooling to room temperature, hydrogenated WO3 nanoplate film was obtained.

[0058] (5) The hydrogenated WO3 nanoplate film was placed in a mixed solution containing 10 mL glycerol, 20 mL anhydrous ethanol and 500 μL tetrabutyl titanate and treated at 200 °C for 12 h. After cooling to room temperature, the second reaction product was washed multiple times with deionized water and ethanol. After natural drying, it was calcined in a muffle furnace at 350 °C for 2 h to obtain the PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray.

[0059] Example 3

[0060] This embodiment provides an application of a PECOD sensor based on a tungsten trioxide / titanium dioxide nanoarray, which can be used to detect the content of organic pollutants in water bodies, including the following steps:

[0061] (1) Prepare a set of standard solutions of detection substrates of different concentrations, including blank standard samples, and drop the standard solutions of detection substrates of different concentrations onto the PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray prepared in Example 1 or 2 respectively.

[0062] (2) A three-electrode system was formed by using a PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The net photocurrent of the substrate under illumination was detected in the electrolyte using the linear scanning voltammetry of an electrochemical workstation, and a linear relationship graph of net photocurrent and concentration was plotted.

[0063] (3) The wastewater is drop-coated onto the PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray prepared in Example 1 or 2. The net photocurrent of the wastewater is detected according to step (2), and a linear relationship graph of net photocurrent-concentration is plotted. The content of the electrolyzed organic compounds is obtained from the linear relationship graph, and the COD of the wastewater is indirectly calculated.

[0064] The detection substrate can be an organic compound, and preferably, it can be either glucose or glutaric acid.

[0065] Comparative Example 1

[0066] This comparative example provides a method for preparing a photoelectrode based on a tungsten trioxide / titanium dioxide nanoarray. The difference from Example 1 is that step (4) is not included in this comparative example.

[0067] Comparative Example 2

[0068] This comparative example provides a method for preparing a photoelectrode based on a hydrogenated tungsten trioxide nanoarray. The difference between this comparative example and Example 1 is that step (5) is not included.

[0069] Comparative Example 3

[0070] This comparative example provides a photoelectrode based on a tungsten trioxide nanoarray. The difference from Example 1 is that this comparative example does not include steps (4)-(5).

[0071] The following are application tests of the PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray prepared by the method of Example 1 and the photoelectrodes prepared by the methods of Comparative Examples 1-3.

[0072] This invention uses glucose as the detection substrate instead of organic pollutants in wastewater for application testing, and the electrolyte used is a 0.5 mol / L Na2SO4 solution.

[0073] Experimental Example 1

[0074] This experimental example utilizes linear scanning voltammetry on an electrochemical workstation. The PECOD sensor based on a tungsten trioxide / titanium dioxide nanoarray, prepared in Example 1, was selected as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, forming a three-electrode system. The electrochemical workstation was set with an initial potential of 0V, a termination potential of 1.2V, a scan rate of 0.1V / s, a sampling interval of 0.001V, a settling time of 2s, and a sensitivity of 1×10⁻⁶. -3 A. The changes in current as a function of potential of the PECOD sensor in an electrolyte without glucose were tested under both light and dark conditions. The results are as follows: Figure 3 As shown. From Figure 3It can be seen that the photocurrent density of the PECOD sensor under illumination is significantly higher than that under darkness, indicating that due to the photocatalytic reaction of the hydrogenated tungsten trioxide / titanium dioxide nanoarray, more photogenerated electrons are generated on the surface of the PECOD sensor under illumination to participate in the electrochemical reaction.

[0075] Experimental Example 2

[0076] This experimental example uses a three-electrode system and a chronoamperometry method to test the relationship between photocurrent and organic matter concentration in the photoelectrocatalytic process of organic matter using a PECOD sensor based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray.

[0077] Glucose standard solutions with concentrations of 0.00625 mmol / L, 0.125 mmol / L, 0.25 mmol / L, 0.5 mmol / L, 0.75 mmol / L, 1 mmol / L, 1 mmol / L, 1.5 mmol / L, 2 mmol / L, 2.5 mmol / L, and 3 mmol / L, as well as a blank standard without glucose, were prepared respectively.

[0078] The PECOD sensor based on a tungsten trioxide / titanium dioxide nanoarray prepared in Example 1 was selected as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode to form a three-electrode system. The electrochemical workstation was set with an initial potential of 0V, a termination potential of 1.4V, a scan rate of 0.1V / s, a sampling interval of 0.001V, a settling time of 2s, and a sensitivity of 1×10⁻⁶. -3 A, under simulated solar radiation (AM1.5G, 300mW / cm²) 2 The current change over time of the PECOD sensor and solutions of different concentrations of glucose, including blank standard, during the photoelectrocatalysis process were tested under illumination conditions, and the results are as follows: Figure 4 As shown. From Figure 4 It can be seen that the PECOD sensor (H-WO3 / TiO2) generates photocurrent under illumination due to the photocatalytic reactions of both hydrogenated tungsten trioxide and titanium dioxide. The current generated under illumination is significantly higher than that under darkness. Simultaneously, the photocurrent density increases with increasing glucose concentration in the solution, indicating that glucose participates in the photocatalytic reaction. As the glucose concentration increases, glucose molecules provide more reaction sites for photogenerated holes, allowing these holes to be consumed more effectively, thus improving the photocatalytic efficiency. This also demonstrates the high sensitivity of the PECOD sensor in detecting glucose concentration in solution. Furthermore, the photocurrent density detected at the same glucose concentration remains essentially unchanged over time, indicating that the photocatalytic reaction between the PECOD sensor and organic matter is relatively stable within a certain period.

[0079] Experimental Example 3

[0080] This experimental example uses a three-electrode system and a chronoamperometry method to test the photoelectrochemical catalysis effect of the photoelectrodes prepared in Example 1 and Comparative Examples 1-3 on organic compounds.

[0081] Glucose standard solutions with concentrations of 0.00625 mmol / L, 0.125 mmol / L, 0.25 mmol / L, 0.75 mmol / L, 1 mmol / L, 1 mmol / L, 1.5 mmol / L, 2 mmol / L, and 2.5 mmol / L, as well as a blank standard without glucose, were prepared respectively.

[0082] The photoelectrodes prepared in Example 1 and Comparative Examples 1-3 were used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode to form a three-electrode system. The electrochemical workstation was set with an initial potential of 0V, a termination potential of 1.2V, a scan rate of 0.1V / s, a sampling interval of 0.001V, a settling time of 2s, and a sensitivity of 1×10⁻⁶. -3 A. Test different working electrodes under simulated solar radiation (AM1.5G, 300mW / cm²). 2 The current variation over time during photoelectrocatalysis was investigated under illumination conditions and with solutions of different glucose concentrations, including blank standards. The relationship between net photocurrent and glucose concentration at different working electrodes was plotted, and the results are shown below. Figure 5 As shown. From Figure 5 It can be seen that, compared with the photoelectrodes prepared in Comparative Examples 1-3, the PECOD sensor (H-WO3 / TiO2) based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray prepared in Example 1 exhibits the highest net photocurrent when reacting with a glucose solution of the same concentration. This indicates that the PECOD sensor prepared by this method generates more photogenerated electrons on its surface to participate in the electrochemical reaction under the same illumination conditions, resulting in higher electron transfer efficiency and higher glucose degradation efficiency. This allows it to degrade organic matter and thus reduce COD in wastewater. Furthermore, the net photocurrent of the PECOD sensor based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray prepared in Example 1 changes significantly with variations in glucose concentration. This demonstrates that the PECOD sensor based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray prepared in Example 1 has high sensitivity to changes in glucose concentration and can be used as a highly sensitive PECOD sensor for detecting theoretical COD in wastewater.

[0083] use Figure 5 Photocurrent data from the PECOD sensor at different concentrations of glucose solutions were used to plot the linear relationship between the net photocurrent of glucose molecules and the theoretical COD. Figure 6 As shown. From Figure 6 It can be seen that when the PECOD sensor detects glucose standard solutions of different concentrations, the net photocurrent (Ic) is... A ) and theoretical COD (COD Th It shows a high positive correlation.

[0084] According to Fick's law, the molar concentration of organic matter, C... b With net current I net The relationship is shown in equation (I).

[0085]

[0086] Due to the theoretical COD and C b The calculation formula is:

[0087]

[0088] According to equations (I) and (II), we can obtain I net The formula for calculating ThCOD is:

[0089]

[0090] Among them, I net is the net photocurrent (μA) generated during the photoelectrocatalytic process, n is the number of electrons transferred when the organic matter is mineralized, A is the area of ​​the working electrode, F is the Faraday constant, D is the diffusion coefficient of the organic matter, δ represents the thickness of the Nernst diffusion layer, and C b C represents the molar concentration of organic matter (mol / L). m denoted as ρ, where ρ is the mass concentration of the organic compound (mg / L), and M is the molar mass of the organic compound.

[0091] Because of I A The net photocurrent (mA / cm²) generated per unit area during the photoelectrocatalysis process in this invention. 2 COD Th The theoretical COD (mg / L) of this invention satisfies:

[0092] I net =I A ×A×κ, Equation (IV)

[0093] COD Th = [ThCOD] × α, Equation (V)

[0094] Substituting equations (IV) and (V) into equation (III) yields:

[0095]

[0096] Equation (VI) shows that, according to Fick's law, the net photocurrent is directly proportional to the theoretical COD, and the result is consistent with... Figure 6 They corroborate each other.

[0097] Where a and b are the net photocurrent-theoretical COD curves, respectively. Figure 6 The slope and intercept of ) , κ is I net with I A The unit conversion factor between [ThCOD] and the theoretical COD of this invention is α.

[0098] Therefore, according to Figure 6 The linear relationship between net photocurrent and theoretical COD is known. By detecting the net photocurrent in water using a three-electrode system, the COD value can be calculated based on this linear relationship. In summary, the PECOD sensor of this invention can be used as a working electrode, utilizing a three-electrode system to oxidize organic matter in water and record detailed current change data. The organic matter content in the water can be indirectly calculated through the linear relationship between net photocurrent and theoretical COD, such as for detecting COD values ​​in wastewater.

[0099] Therefore, compared with the prior art, the beneficial effects of the present invention are: the PECOD sensor prepared by the present invention, loaded with hydrogenated tungsten trioxide and titanium dioxide, can not only absorb a wider range of spectra, but also has higher photocatalytic activity. Simultaneously, by using a three-electrode system to detect current changes through an electrochemical workstation, and by indirectly calculating the organic matter content in the water body through the relationship between the net photocurrent and theoretical COD during the photoelectrocatalytic process, the PECOD sensor can be used for COD detection in wastewater.

[0100] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method for fabricating a PECOD sensor based on a tungsten trioxide / titanium dioxide nanoarray, characterized in that, Its preparation method includes the following steps: S1. Fluorine-doped tin oxide conductive glass is ultrasonically treated with acetone, deionized water, and anhydrous ethanol in sequence. Then, the fluorine-doped tin oxide conductive glass is rinsed with deionized water and dried to obtain a conductive substrate. S2. Dissolve sodium tungstate dihydrate in deionized water, slowly add hydrochloric acid solution and stir until a suspension is obtained, add ammonium oxalate to the suspension and continue stirring until the suspension becomes clear, add deionized water and stir to obtain the precursor solution. S3. Transfer the precursor solution to the liner of Teflon, place the conductive substrate against the container wall of Teflon with the conductive side facing down into the precursor solution for hydrothermal reaction, cool to room temperature, rinse the first reaction product with deionized water and dry to obtain FTO conductive glass with WO3 nanoplates grown. S4. Calcine the FTO conductive glass with WO3 nanoplates grown on it, cool it to room temperature, and then perform a second calcination treatment in an atmosphere of argon-hydrogen mixed gas. After cooling to room temperature, hydrogenated WO3 nanoplate film is obtained. S5. The hydrogenated WO3 nanoplate film is placed in a mixed solution containing glycerol, anhydrous ethanol and tetrabutyl titanate, and treated at 160~180℃ for 10~12h. After cooling to room temperature, the second reaction product is washed multiple times with deionized water and ethanol, and then calcined after natural drying to obtain the PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray. In step S4, the second calcination treatment is carried out in a tube furnace at a temperature of 250~350℃ and a heating rate of 2~3℃ / min for 2~3h.

2. The method for fabricating a PECOD sensor based on a tungsten trioxide / titanium dioxide nanoarray according to claim 1, characterized in that, In step S2, during the process of dissolving sodium tungstate dihydrate in deionized water, the amount of sodium tungstate dihydrate used is 0.23~0.46g, and the amount of deionized water used is 30~60mL. The hydrochloric acid solution is 10-20 mL of 3 mol / L hydrochloric acid solution, the amount of ammonium oxalate is 0.2-0.4 g, and the amount of deionized water used in the process of adding deionized water to obtain the precursor solution is 30-60 mL.

3. The method for fabricating a PECOD sensor based on a tungsten trioxide / titanium dioxide nanoarray according to claim 1, characterized in that, In step S2, the stirring time for slowly adding hydrochloric acid solution and stirring is 5-10 minutes, and the stirring time for adding ammonium oxalate to the suspension and continuing to stir is 8-12 minutes.

4. The method for fabricating a PECOD sensor based on a tungsten trioxide / titanium dioxide nanoarray according to claim 1, characterized in that, In step S3, the hydrothermal reaction temperature is 120~140℃ and the reaction time is 10~11h; the drying process is to keep the product in an oven at 60~70℃ for 1~2h.

5. The method for fabricating a PECOD sensor based on a tungsten trioxide / titanium dioxide nanoarray according to claim 4, characterized in that, In step S4, the method for calcining the FTO conductive glass with WO3 nanoplatelets is to calcine it in a muffle furnace at a temperature of 450~460℃ and a heating rate of 4~5℃ / min for 1~2 hours.

6. The method for fabricating a PECOD sensor based on a tungsten trioxide / titanium dioxide nanoarray according to claim 1, characterized in that, In step S5, the volume ratio of glycerol, anhydrous ethanol and tetrabutyl titanate in the mixed solution is (1~10):(20~30):(0.3~0.5).

7. The method for fabricating a PECOD sensor based on a tungsten trioxide / titanium dioxide nanoarray according to claim 1, characterized in that, In step S5, the calcination process involves calcining at 400~450℃ for 2~3 hours.

8. A PECOD sensor based on a hydrogenated tungsten trioxide / titanium dioxide nanoarray, characterized in that, The PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray was prepared according to any one of claims 1 to 7.

9. The application of the PECOD sensor based on hydrogenated tungsten trioxide / titanium dioxide nanoarray as described in claim 8 in the detection of organic pollutant content in water.

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