Preparation method of composite semiconductor materials and sensor electrodes

Abstract

This disclosure relates to a method for preparing a composite semiconductor material and a sensor electrode, and pertains to the field of semiconductor material preparation technology. The method includes: 1. Adding a bismuth source, a lanthanum source, and a cerium source to a first sodium citrate solution to obtain a first solution; the amount of sodium citrate is greater than the sum of the amounts of bismuth, lanthanum, and cerium; adding a vanadium source to a second sodium citrate solution to obtain a second solution; the molar ratio of bismuth, lanthanum, and cerium is (7-9):(0.5-1.5):(0.5-1.5); 2. Adding the second solution to the first solution in batches to obtain a third solution; 3. Adjusting the pH of the third solution to 4-8, and then performing a hydrothermal reaction to obtain La / Ce-BiVO4; 4. Dispersing La / Ce-BiVO4 in water, and adding a cobalt source, NH4F, and CO(NH2)2, and reacting to obtain a precursor; 5. Calcining the precursor to obtain the composite semiconductor material.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor material preparation technology, and more specifically, to a method for preparing a composite semiconductor material and a sensor electrode. Background Technology

[0002] Photoelectrochemical sensors have become a research hotspot due to their advantages such as simple operation, easy miniaturization, low cost, high sensitivity, and rapid response, and are widely used in food detection, immunoassay, DNA analysis, and industrial and agricultural fields. Currently, researchers mostly utilize the characteristic of N-type semiconductors being easily oxidized by holes to design sensors. However, when used for actual sample detection, on the one hand, some coexisting reducing substances can cause significant interference, such as ascorbic acid, cysteine, uric acid, and dopamine. On the other hand, strategies for improving photoanode sensors are very limited, and the selectivity for coexisting substances is poor. In contrast, P-type semiconductors are unaffected by reducing substances and show great potential in developing more versatile biosensors.

[0003] BiVO4 is a common inorganic pigment widely used due to its suitable band gap (2.4–2.5 eV), which is close to the central spectrum of solar energy (2.6 eV), exhibiting excellent visible light absorption. In addition, its non-toxic, inexpensive, stable, and environmentally friendly properties make it suitable as a substitute for toxic elements such as lead, chromium, and cadmium in optoelectronic materials, enabling the fabrication of safe and non-toxic PEC biosensors. BiVO4 also possesses acousto-optic conversion, photocatalytic activity, and ionic conductivity. These properties give BiVO4 broad prospects for development in biosensors, photoelectrochemical hydrolysis, organic degradation, and photoelectric conversion. Although BiVO4 is an important inorganic optoelectronic material with excellent photoelectric properties, the high charge recombination rate and low incident light absorption of pure BiVO4 limit its photoelectrochemical development.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this disclosure is to overcome the shortcomings of the prior art and provide a method for preparing composite semiconductor materials and sensor electrodes. By using sodium citrate as a template, a cobalt tetroxide-coated bismuth vanadate-doped composite material is prepared. This material is a nanowire array with a large specific surface area and can be used as an excellent material for preparing sensor electrodes.

[0006] According to a first aspect of this disclosure, a method for preparing a composite semiconductor material is provided, comprising the following steps:

[0007] S1. Obtain the first solution and the second solution;

[0008] Obtaining the first solution includes: obtaining a first sodium citrate solution, wherein the first sodium citrate solution is a nitric acid solution containing dissolved sodium citrate; adding a bismuth source, a lanthanum source, and a cerium source to the first sodium citrate solution to obtain the first solution;

[0009] Wherein, the amount of sodium citrate in the first sodium citrate solution is N, the amount of bismuth in the bismuth source is x, the amount of lanthanum in the lanthanum source is y, and the amount of cerium in the cerium source is z, then N > x + y + z.

[0010] Obtaining the second solution includes: obtaining a second sodium citrate solution, wherein the second sodium citrate solution is a nitric acid solution containing dissolved sodium citrate; adding a vanadium source to the second sodium citrate solution to obtain the second solution; wherein the amount of vanadium in the vanadium source is A, then x:y:z:A=(7~9):(0.5~1.5):(0.5~1.5):10, and x+y+z=A;

[0011] S2. Add the second solution to the first solution in batches to obtain the third solution;

[0012] S3. Adjust the pH value of the third solution to 4-8, and then carry out the first hydrothermal reaction to obtain lanthanum and cerium-doped bismuth vanadate.

[0013] S4. Disperse the lanthanum and cerium-doped bismuth vanadate obtained in step S3 in water to obtain a lanthanum and cerium-doped bismuth vanadate suspension.

[0014] A second hydrothermal reaction was carried out in a lanthanum and cerium-doped bismuth vanadate suspension with the addition of a cobalt source, NH4F and CO(NH2)2 to obtain a precursor; wherein the molar ratio of cobalt source, NH4F and CO(NH2)2 was 1:(1~2):(1~10).

[0015] S5. The precursor obtained in step S4 is placed in a reaction vessel and heated and calcined to obtain a cobalt tetroxide-coated lanthanum and cerium-doped bismuth vanadate composite semiconductor material.

[0016] In one exemplary embodiment of this disclosure, in step S1, the molar ratio of bismuth, lanthanum, and cerium is 8:1:1.

[0017] In an exemplary embodiment of this disclosure, in step S4, the molar ratio of the cobalt source, NH4F, and CO(NH2)2 is 1:2:5.

[0018] In an exemplary embodiment of this disclosure, in step S1, the bismuth source is Bi(NO3)3·5H2O, the lanthanum source is La(NO3)3·6H2O, the cerium source is Ce(NO3)3·6H2O, and the vanadium source is NH4VO3;

[0019] In step S4, the cobalt source is Co(NO3)2·6H2O.

[0020] In an exemplary embodiment of this disclosure, in step S5, the mass ratio of cobalt tetroxide to lanthanum and cerium-doped bismuth vanadate coated with cobalt tetroxide is (20-40):100.

[0021] In one exemplary embodiment of this disclosure, in step S3, the pH value of the third solution is adjusted to 7 using sodium hydroxide.

[0022] In an exemplary embodiment of this disclosure, in step S3, the first hydrothermal reaction involves placing the pH-adjusted third solution in a reaction vessel and performing a hydrothermal reaction at a temperature of 120–200°C for 12–24 hours.

[0023] In step S4, the second hydrothermal reaction involves placing a lanthanum and cerium-doped bismuth vanadate suspension containing a cobalt source, NH4F, and CO(NH2)2 in a reaction vessel and hydrothermally reacting it for 3 to 12 hours at a temperature of 90 to 160°C.

[0024] In step S5, the heating and calcination involves placing the precursor in a muffle furnace and heating it to 300-500°C at a heating rate of 1-10°C / min, and calcining it for 2-5 hours.

[0025] According to a second aspect of this disclosure, a method for preparing a composite semiconductor material is also provided, comprising the following steps:

[0026] S1. Obtain the fourth and fifth solutions;

[0027] Obtaining the fourth solution includes: obtaining a third sodium citrate solution, wherein the third sodium citrate solution is a nitric acid solution containing dissolved sodium citrate; adding a bismuth source and a cerium source to the third sodium citrate solution to obtain the fourth solution;

[0028] Wherein, the amount of sodium citrate in the third sodium citrate solution is N, the amount of bismuth in the bismuth source is x, and the amount of cerium in the cerium source is z, then N > x + z.

[0029] Obtaining the fifth solution includes: obtaining a fourth sodium citrate solution, wherein the fourth sodium citrate solution is a nitric acid solution containing sodium citrate; adding a vanadium source to the fourth sodium citrate solution to obtain the fifth solution; wherein the amount of vanadium in the vanadium source is A, then x:z = (7~9):(0.5~1.5), and x+z = A;

[0030] S2. Add the fifth solution to the fourth solution in batches to obtain the sixth solution;

[0031] S3. Adjust the pH value of the sixth solution to 4-8, and then carry out the first hydrothermal reaction to obtain cerium-doped bismuth vanadate.

[0032] S4. Disperse the cerium-doped bismuth vanadate obtained in step S3 in water to obtain a cerium-doped bismuth vanadate suspension.

[0033] A cobalt source, NH4F and CO(NH2)2 were added to a cerium-doped bismuth vanadate suspension to carry out a second hydrothermal reaction to obtain a precursor; wherein the molar ratio of cobalt source, NH4F and CO(NH2)2 was 1:(1~2):(1~10).

[0034] S5. The precursor obtained in step S4 is placed in a reaction vessel and heated and calcined to obtain a cobalt tetroxide-coated cerium-doped bismuth vanadate composite semiconductor material.

[0035] According to a third aspect of this disclosure, a method for preparing a composite semiconductor material is also provided, comprising the following steps:

[0036] S1. Obtain the seventh and eighth solutions;

[0037] Obtaining the seventh solution includes: obtaining a fifth sodium citrate solution, wherein the fifth sodium citrate solution is a nitric acid solution containing dissolved sodium citrate; adding a bismuth source and a lanthanum source to the fifth sodium citrate solution to obtain the seventh solution;

[0038] Wherein, the amount of sodium citrate in the fifth sodium citrate solution is N, the amount of bismuth in the bismuth source is x, and the amount of lanthanum in the lanthanum source is y, then N > x + y.

[0039] Obtaining the eighth solution includes: obtaining a sixth sodium citrate solution, wherein the sixth sodium citrate solution is a nitric acid solution containing sodium citrate; adding a vanadium source to the sixth sodium citrate solution to obtain the eighth solution; wherein the amount of vanadium in the vanadium source is A, then x:y = (7~9):(0.5~1.5), and x+y = A;

[0040] S2. Add the eighth solution to the seventh solution in batches to obtain the ninth solution;

[0041] S3. Adjust the pH value of the ninth solution to 4-8, and then carry out the first hydrothermal reaction to obtain lanthanum-doped bismuth vanadate.

[0042] S4. Disperse the lanthanum-doped bismuth vanadate obtained in step S3 in water to obtain a lanthanum-doped bismuth vanadate suspension.

[0043] A second hydrothermal reaction was carried out in a lanthanum-doped bismuth vanadate suspension by adding a cobalt source, NH4F and CO(NH2)2 to obtain a precursor; wherein the molar ratio of cobalt source, NH4F and CO(NH2)2 was 1:(1~2):(1~10).

[0044] S5. The precursor obtained in step S4 is placed in a reaction vessel and heated and calcined to obtain a cobalt tetroxide-coated lanthanum-doped bismuth vanadate composite semiconductor material.

[0045] According to a fourth aspect of this disclosure, a sensor electrode is also provided, comprising a composite semiconductor material prepared by the above-described preparation method.

[0046] The method for preparing composite semiconductor materials disclosed herein involves adding lanthanum and / or cerium sources in a specific ratio to prepare lanthanum and / or cerium-doped bismuth vanadate, and then growing cobalt tetroxide in situ on the lanthanum and / or cerium-doped bismuth vanadate to obtain a composite semiconductor material with a three-dimensional needle-like nanowire array structure. This preparation method is simple, efficient, and suitable for industrial mass production.

[0047] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0048] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0049] Figure 1 This is a scanning electron microscope image of a Co3O4@La / Ce-BiVO4 composite semiconductor material in one embodiment of this disclosure.

[0050] Figure 2 This is an X-ray diffraction pattern of a Co3O4@La / Ce-BiVO4 composite semiconductor material in one embodiment of this disclosure.

[0051] Figure 3This is a comparison of nitrogen adsorption-desorption curves of Co3O4@La / Ce-BiVO4 composite semiconductor material and La / Ce-BiVO4 material in some embodiments of this disclosure.

[0052] Figure 4 This is a comparison of the JV test curves of the Co3O4@La / Ce-BiVO4 electrode and the La / Ce-BiVO4 electrode in some embodiments of this disclosure.

[0053] Figure 5 For some embodiments of this disclosure, electrochemical impedance spectroscopy comparison spectra of Co3O4@La / Ce-BiVO4 electrode and La / Ce-BiVO4 electrode are presented.

[0054] Figure 6 This is a comparison of the it curves for stability testing of the Co3O4@La / Ce-BiVO4 electrode and the La / Ce-BiVO4 electrode in some embodiments of this disclosure. Detailed Implementation

[0055] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore their detailed description will be omitted.

[0056] The terms “a,” “the,” and “the” are used to indicate the existence of one or more elements / components / etc.; the terms “including” and “having” are used to indicate an open-ended inclusion and to mean that there may be other elements / components / etc. in addition to the listed elements / components / etc.; the terms “first,” “second,” and “third,” etc., are used only as markers and are not a limitation on the number of objects.

[0057] BiVO4, as an important inorganic optoelectronic material, possesses excellent photoelectric properties. However, the high charge recombination rate and low incident light absorption of pure BiVO4 limit its development in photoelectrochemistry. To overcome this limitation, most studies have focused on modifying BiVO4 by altering its morphology and structure, exposing special crystal planes, ion doping, noble metal loading, or heterojunctions, thereby promoting charge separation and improving photocatalytic activity and photoelectric efficiency.

[0058] This disclosure provides a method for preparing a composite semiconductor material. By preparing cobalt tetroxide-coated lanthanum and cerium-doped bismuth vanadate, a three-dimensional needle-like nanowire array composite semiconductor material is obtained. The method includes the following steps:

[0059] S1. Obtain the first solution and the second solution.

[0060] Obtaining the first solution includes: obtaining a first sodium citrate solution, which is a nitric acid solution containing dissolved sodium citrate. A bismuth source, a lanthanum source, and a cerium source are added to the first sodium citrate solution to obtain the first solution. Wherein, the amount of sodium citrate in the first sodium citrate solution is N, the amount of bismuth in the bismuth source is x, the amount of lanthanum in the lanthanum source is y, and the amount of cerium in the cerium source is z, then N > x + y + z.

[0061] Obtaining the second solution includes: obtaining a second sodium citrate solution, which is a nitric acid solution containing dissolved sodium citrate. A vanadium source is added to the second sodium citrate solution to obtain the second solution. Wherein, the amount of bismuth in the bismuth source is x, the amount of lanthanum in the lanthanum source is y, the amount of cerium in the cerium source is z, and the amount of vanadium in the vanadium source is A. Then, the molar ratio of bismuth, lanthanum, cerium, and vanadium satisfies x:y:z:A = (7-9):(0.5-1.5):(0.5-1.5):10, and x + y + z = A.

[0062] Furthermore, the molar ratio of bismuth, lanthanum, cerium, and vanadium can be x:y:z:A = 8:1:1:10. For example, the molar ratio of bismuth, lanthanum, cerium, and vanadium can also be 7:1.5:1.5:10, or 7.5:1.5:1:10, or 7.8:1:1.2:10, or 7.8:0.7:1.5:10, or 8:1.5:0.5:10, or 8.4:0.7:0.9:10, or 8.8:0.5:0.7:10, or 9:0.5:0.5:10.

[0063] In one example, the concentrations of sodium citrate in the first and second sodium citrate solutions are the same, and the volume fractions of nitric acid solution are the same. Thus, the total sodium citrate can be weighed and dissolved in nitric acid solution to prepare a total sodium citrate solution. When preparing the first and second solutions, the first and second sodium citrate solutions are measured out according to the required amounts. Alternatively, the first and second sodium citrate solutions can be prepared separately.

[0064] In one example, the volume fraction of the nitric acid solution is 10% to 30%. The nitric acid solution is used to ensure the complete dissolution of the bismuth, lanthanum, and cerium sources, and facilitates their removal during subsequent calcination, avoiding the introduction of impurities that are difficult to remove. For example, the volume fraction of the nitric acid solution can be 10%, 15%, 20%, 25%, or 30%.

[0065] In one embodiment of this disclosure, the bismuth source is Bi(NO3)3·5H2O, the lanthanum source is La(NO3)3·6H2O, the cerium source is Ce(NO3)3·6H2O, and the vanadium source is NH4VO3. The bismuth, lanthanum, and cerium sources are all nitrates, and the vanadium source is ammonium metavanadate. This ensures that during subsequent reactions, when heated to high temperatures, both nitrate and ammonium ions are oxidized and released as gases, thus not increasing impurities in the final reaction products and simplifying the experimental procedure.

[0066] S2. Add the second solution to the first solution in batches and stir to obtain the third solution.

[0067] S3. Adjust the pH value of the third solution to 4-8, and then carry out the first hydrothermal reaction to obtain lanthanum and cerium co-doped bismuth vanadate (La / Ce-BiVO4).

[0068] In one example, sodium hydroxide solution can be used to adjust the pH of the third solution. Sodium citrate is used in step S1, thus using sodium hydroxide during pH adjustment prevents the introduction of new impurities throughout the preparation process. Further, the pH of the third solution is adjusted to pH = 7. For example, the pH of the third solution can be adjusted to pH = 4, pH = 5, pH = 5.5, pH = 6, pH = 6.5, pH = 7, pH = 7.5, pH = 8, etc.

[0069] For example, the aqueous solution containing solid La / Ce-BiVO4 obtained after the first hydrothermal reaction is removed by vacuum filtration to obtain solid La / Ce-BiVO4. In this way, sodium ions dissolved in the water in the reaction system can be removed without adding an additional impurity removal step.

[0070] In one embodiment of this disclosure, the first hydrothermal reaction can be carried out in a reaction vessel. After the pH of the third solution is adjusted, it is placed in the reaction vessel and the hydrothermal reaction is carried out for 12 to 24 hours at a temperature range of 120–200°C. For example, the reaction conditions for the first hydrothermal reaction in the reaction vessel are as follows: 16 hours at 120°C; or 24 hours at 130°C; or 18 hours at 140°C; or 20 hours at 120°C; or 14 hours at 150°C; or 22 hours at 160°C; or 12 hours at 170°C; or 20 hours at 180°C; or 18 hours at 190°C; or 15 hours at 200°C, etc.

[0071] S4. Disperse the lanthanum and cerium-doped bismuth vanadate obtained in step S3 in water to obtain a lanthanum and cerium-doped bismuth vanadate suspension. In this way, the lanthanum and cerium-doped bismuth vanadate (La / Ce-BiVO4) suspension is in a dispersed but insoluble state in aqueous solution, which facilitates subsequent coating with cobalt tetroxide (Co3O4).

[0072] A second hydrothermal reaction is carried out by adding a cobalt source, NH4F, and CO(NH2)2 to a lanthanum- and cerium-doped bismuth vanadate suspension to obtain the precursor. The molar ratio of the cobalt source, NH4F, and CO(NH2)2 is 1:(1–2):(1–10). In one example, the cobalt source is Co(NO3)2·6H2O. Thus, using cobalt nitrate facilitates the release of nitrate ions as gas during the high-temperature reaction, without introducing impurities.

[0073] In one embodiment of this disclosure, the molar ratio of the cobalt source, NH4F, and CO(NH2)2 can be 1:2:5. For example, the molar ratio of the cobalt source, NH4F, and CO(NH2)2 can also be 1:1:5, or 1:1.2:8, or 1:1.5:6, or 1:1.8:10, or 1:2:1.5, or 1:2:7, or 1:1.5:1, or 1:1.8:2, or 1:1:4, or 1:1.6:9, etc.

[0074] In one embodiment of this disclosure, the second hydrothermal reaction can be carried out in a reactor. A lanthanum- and cerium-doped bismuth vanadate suspension containing a cobalt source, NH4F, and CO(NH2)2 is added to the reactor, and the hydrothermal reaction is carried out at a temperature of 90–160°C for 3–12 hours. For example, the reaction conditions for the second hydrothermal reaction can be: 6 hours at 90°C, 8 hours at 100°C, 3 hours at 110°C, 5 hours at 120°C, 12 hours at 130°C, 4 hours at 140°C, 10 hours at 150°C, 7 hours at 160°C, 9 hours at 110°C, or 6 hours at 120°C, etc.

[0075] S5. The precursor obtained in step S4 is placed in a reaction vessel and heated and calcined to obtain a cobalt tetroxide-coated lanthanum and cerium-doped bismuth vanadate composite semiconductor material.

[0076] In one embodiment of this disclosure, the mass ratio of cobalt tetroxide (Co3O4) to lanthanum / cerium-doped bismuth vanadate (La / Ce-BiVO4) in the cobalt tetroxide-coated lanthanum / cerium-doped bismuth vanadate (Co3O4@La / Ce-BiVO4) is (20-40):100. For example, the mass ratio of Co3O4 to La / Ce-BiVO4 can be 20:100, 25:100, 30:100, 35:100, or 40:100, etc.

[0077] In one embodiment of this disclosure, in step S5, the precursor is placed in a reaction vessel and heated and calcined, which can be done by placing the precursor in a muffle furnace and reacting it at a temperature of 300-500°C for 2-5 hours. For example, the calcination in a muffle furnace can be carried out at 300°C for 3 hours; or at 320°C for 2 hours; or at 350°C for 4 hours; or at 400°C for 2 hours; or at 380°C for 2 hours; or at 450°C for 3.5 hours; or at 500°C for 2.5 hours; or first at 300°C for 1 hour, then at 400°C for 2 hours; or first at 350°C for 2 hours, then at 450°C for 2 hours; or first at 400°C for 1 hour, then at 500°C for 3 hours; or first at 380°C for 2 hours, then at 450°C for 1 hour, etc.

[0078] For example, the heating rate of the muffle furnace can be 1 to 10 °C / min. For instance, the target temperature can be reached at heating rates of 1 °C / min, 2 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, and 10 °C / min.

[0079] The method for preparing the composite semiconductor material provided in this disclosure involves adding lanthanum and cerium sources in the aforementioned proportions to prepare lanthanum- and cerium-doped bismuth vanadate, and then growing and coating cobalt tetroxide in situ on the lanthanum- and cerium-doped bismuth vanadate to obtain a Co3O4@La / Ce-BiVO4 composite semiconductor material with a three-dimensional needle-like nanowire array structure. This preparation method is simple, efficient, and suitable for industrial mass production. The composite semiconductor material prepared by the above method utilizes an np heterojunction, where electrons are transferred to the n-type component and holes are transferred to the p-type component, enabling Co3O4@La / Ce-BiVO4 to generate a stable current.

[0080] This disclosure also provides a method for preparing a composite semiconductor material, which obtains a three-dimensional needle-like nanowire array composite semiconductor material by preparing cobalt tetroxide-coated cerium-doped bismuth vanadate. The method includes the following steps:

[0081] S1. Obtain the fourth and fifth solutions;

[0082] Obtaining the fourth solution includes: obtaining a third sodium citrate solution, wherein the third sodium citrate solution is a nitric acid solution containing dissolved sodium citrate. A bismuth source and a cerium source are added to the third sodium citrate solution to obtain the fourth solution. Wherein, the amount of sodium citrate in the third sodium citrate solution is N, the amount of bismuth in the bismuth source is x, and the amount of cerium in the cerium source is z, then N > x + z.

[0083] Obtaining the fifth solution includes: obtaining a fourth sodium citrate solution, wherein the fourth sodium citrate solution is a nitric acid solution containing dissolved sodium citrate. A vanadium source is added to the fourth sodium citrate solution to obtain the fifth solution. Wherein, the amount of vanadium in the vanadium source is A, satisfying x:z = (7~9):(0.5~1.5), and x+z = A.

[0084] In one embodiment of this disclosure, the bismuth source is Bi(NO3)3·5H2O, the cerium source is Ce(NO3)3·6H2O, and the vanadium source is NH4VO3. The molar ratio of Bi(NO3)3·5H2O to Ce(NO3)3·6H2O can be 7:1.5, or 7.5:1, or 7.8:1.2, or 7.8:1.5, or 8:0.5, or 8.4:0.9, or 8.8:0.7, or 9:0.5.

[0085] S2. Add the fifth solution to the fourth solution in batches to obtain the sixth solution.

[0086] S3. Adjust the pH of the sixth solution to 4-8, then perform the first hydrothermal reaction to obtain cerium-doped bismuth vanadate. Further, adjust the pH of the sixth solution to pH=7. For example, the pH of the sixth solution can be adjusted to pH=4, pH=5, pH=5.5, pH=6, pH=6.5, pH=7, pH=7.5, pH=8, etc.

[0087] S4. Disperse the cerium-doped bismuth vanadate obtained in step S3 in water to obtain a cerium-doped bismuth vanadate suspension. Add cobalt source, NH4F and CO(NH2)2 to the cerium-doped bismuth vanadate suspension to carry out a second hydrothermal reaction to obtain the precursor. The molar ratio of cobalt source, NH4F and CO(NH2)2 is 1:(1~2):(1~10).

[0088] In one embodiment of this disclosure, the cobalt source can be Co(NO3)2·6H2O. The molar ratio of Co(NO3)2·6H2O, NH4F, and CO(NH2)2 can be 1:2:3. For example, the molar ratio of Co(NO3)2·6H2O, NH4F, and CO(NH2)2 can also be 1:1:5, or 1:1.2:8, or 1:1.5:6, or 1:1.8:10, or 1:2:1.5, or 1:2:7, or 1:1.5:1, or 1:1.8:2, or 1:1:4, or 1:1.6:9, etc.

[0089] S5. The precursor obtained in step S4 is placed in a reaction vessel and heated and calcined to obtain a cobalt tetroxide-coated cerium-doped bismuth vanadate (Co3O4@Ce-BiVO4) composite semiconductor material.

[0090] The selection of bismuth source, cerium source, and vanadium source in the above-mentioned preparation method of cobalt tetroxide-coated cerium-doped bismuth vanadate composite semiconductor material, and the preparation principle are basically the same as those of the preparation method of Co3O4@La / Ce-BiVO4 composite semiconductor material, and will not be repeated here.

[0091] This disclosure also provides a method for preparing a composite semiconductor material, which obtains a three-dimensional needle-like nanowire array composite semiconductor material by preparing cobalt tetroxide-coated lanthanum-doped bismuth vanadate. The method includes the following steps:

[0092] S1. Obtain the seventh and eighth solutions;

[0093] Obtaining the seventh solution includes: obtaining a fifth sodium citrate solution, wherein the fifth sodium citrate solution is a nitric acid solution containing dissolved sodium citrate. A bismuth source and a lanthanum source are added to the fifth sodium citrate solution to obtain the seventh solution. Wherein, the amount of sodium citrate in the fifth sodium citrate solution is N, the amount of bismuth in the bismuth source is x, and the amount of lanthanum in the lanthanum source is y, then N > x + y.

[0094] Obtaining the eighth solution includes: obtaining a sixth sodium citrate solution, wherein the sixth sodium citrate solution is a nitric acid solution containing dissolved sodium citrate. A vanadium source is added to the sixth sodium citrate solution to obtain the eighth solution. Wherein, the amount of vanadium in the vanadium source is A, and the molar ratio of bismuth to lanthanum satisfies x:y = (7-9):(0.5-1.5), and x + y = A.

[0095] In one embodiment of this disclosure, the bismuth source is Bi(NO3)3·5H2O, the lanthanum source is La(NO3)3·6H2O, and the vanadium source is NH4VO3. For example, the molar ratio of Bi(NO3)3·5H2O to La(NO3)3·6H2O can be 7:1.5, or 7.5:1.5, or 7.8:1, or 7.8:0.7, or 8:1.5, or 8.4:0.7, or 8.8:0.5, or 9:0.5.

[0096] S2. Add the eighth solution to the seventh solution in batches to obtain the ninth solution.

[0097] S3. Adjust the pH value of the ninth solution to 4-8, and then carry out the first hydrothermal reaction to obtain lanthanum-doped bismuth vanadate.

[0098] S4. Disperse the lanthanum-doped bismuth vanadate obtained in step S3 in water to obtain a lanthanum-doped bismuth vanadate suspension. Add cobalt source, NH4F and CO(NH2)2 to the lanthanum-doped bismuth vanadate suspension to carry out a second hydrothermal reaction to obtain the precursor. The molar ratio of cobalt source, NH4F and CO(NH2)2 is 1:(1~2):(1~10).

[0099] S5. The precursor obtained in step S4 is placed in a reaction vessel and heated and calcined to obtain a cobalt tetroxide-coated lanthanum-doped bismuth vanadate (Co3O4@La-BiVO4) composite semiconductor material.

[0100] The selection of bismuth source, lanthanum source, and vanadium source in the above-mentioned preparation method of cobalt tetroxide-coated lanthanum-doped bismuth vanadate composite semiconductor material, as well as the preparation principle, are basically the same as those of the Co3O4@La / Ce-BiVO4 composite semiconductor material, and will not be repeated here.

[0101] This disclosure also provides a sensor electrode comprising a cobalt tetroxide-coated lanthanum and / or cerium-doped bismuth vanadate composite semiconductor material prepared by any of the methods described in the above-described preparation method embodiments. This sensor electrode can be used as an electrode for a biosensor or other types of sensors. Since this sensor electrode possesses any of the composite semiconductor materials prepared according to the embodiments corresponding to the above-described preparation methods, it exhibits the same beneficial effects, which will not be elaborated further here.

[0102] The following examples further illustrate the preparation method of composite semiconductor materials, and demonstrate the characteristics of cobalt tetroxide-coated lanthanum and cerium-doped bismuth vanadate composite semiconductor materials and the sensor electrodes prepared therefrom.

[0103] Example 1

[0104] Dissolve 5.6g of sodium citrate in a 20% (v / v) nitric acid solution, then add 3.88g of Bi(NO3)3·5H2O, 0.433g of La(NO3)3·6H2O, and 0.434g of Ce(NO3)3·6H2O. Stir until Bi(NO3)3·5H2O, La(NO3)3·6H2O, and Ce(NO3)3·6H2O are fully dissolved to obtain the first solution.

[0105] Dissolve 5.6g of sodium citrate in a 20% nitric acid solution, then add 1.17g of NH4VO3 and stir until the NH4VO3 is fully dissolved to obtain a second solution.

[0106] The second solution is slowly added to the first solution, and the mixture is stirred to obtain the third solution.

[0107] After adjusting the pH value by adding 6.0 g of sodium hydroxide to the third solution, the third solution was then placed in a hydrothermal environment at 180 °C for 24 h. After filtration, lanthanum and cerium co-doped bismuth vanadate (La / Ce-BiVO4) was obtained.

[0108] Weigh 1.6g of La / Ce-BiVO4 powder and stir to disperse it in 105mL of water to obtain a La / Ce-BiVO4 suspension.

[0109] Add 4.35g Co(NO3)2·6H2O, 1.2g NH4F, and 4.5g CO(NH2)2 to a La / Ce-BiVO4 suspension, and place it in a reactor for hydrothermal treatment at 120℃ for 10h to obtain the precursor.

[0110] The precursor was placed in a muffle furnace and heat-treated at 350°C for 3 hours to obtain a cobalt tetroxide-coated lanthanum and cerium-doped bismuth vanadate (Co3O4@La / Ce-BiVO4) composite semiconductor material.

[0111] Example 2

[0112] Dissolve 5.6g of sodium citrate in a 20% (v / v) nitric acid solution, then add 3.88g of Bi(NO3)3·5H2O, 0.433g of La(NO3)3·6H2O, and 0.434g of Ce(NO3)3·6H2O. Stir until Bi(NO3)3·5H2O, La(NO3)3·6H2O, and Ce(NO3)3·6H2O are fully dissolved to obtain the first solution.

[0113] Dissolve 5.6g of sodium citrate in a 20% nitric acid solution, then add 1.17g of NH4VO3 and stir until the NH4VO3 is fully dissolved to obtain a second solution.

[0114] The second solution is slowly added to the first solution, and the mixture is stirred to obtain the third solution.

[0115] 6.0 g of sodium hydroxide was added to the third solution to adjust the pH value. The third solution was then placed in a hydrothermal environment at 180 °C for 24 h. After filtration, lanthanum and cerium co-doped bismuth vanadate (La / Ce-BiVO4) was obtained.

[0116] Lanthanum and cerium co-doped bismuth vanadate was placed in a muffle furnace and heat-treated at 350°C for 3 hours to obtain La / Ce-BiVO4 material.

[0117] Example 3

[0118] Dissolve 5.6g of sodium citrate in a 20% nitric acid solution, then add 4.36g of Bi(NO3)3·5H2O and 0.434g of Ce(NO3)3·6H2O, and stir until Bi(NO3)3·5H2O and Ce(NO3)3·6H2O are fully dissolved to obtain the fourth solution.

[0119] Dissolve 5.6g of sodium citrate in a 20% nitric acid solution, then add 1.17g of NH4VO3 and stir until the NH4VO3 is fully dissolved to obtain the fifth solution.

[0120] The fifth solution was added to the fourth solution in batches and stirred to obtain the sixth solution.

[0121] After adjusting the pH value by adding 6.0 g of sodium hydroxide to the sixth solution, the sixth solution was placed in a reaction vessel and subjected to the first hydrothermal reaction at 180 °C for 24 h. After filtration, cerium-doped bismuth vanadate (Ce-BiVO4) was obtained.

[0122] Weigh 1.6g of Ce-BiVO4 powder and stir to disperse it in 105mL of water to obtain a Ce-BiVO4 suspension.

[0123] 4.35g Co(NO3)2·6H2O, 1.2g NH4F, and 4.5g CO(NH2)2 were added to a Ce-BiVO4 suspension and placed in a reactor for hydrothermal treatment at 120℃ for 10h to obtain the precursor.

[0124] The precursor was placed in a muffle furnace and heat-treated at 350°C for 3 hours to obtain a cobalt tetroxide-coated cerium-doped bismuth vanadate (Co3O4@Ce-BiVO4) composite semiconductor material.

[0125] X-ray diffraction analysis showed that the Co3O4@Ce-BiVO4 material obtained in this embodiment has the same nanowire array structure as the Co3O4@La / Ce-BiVO4 obtained in Example 1.

[0126] Example 4

[0127] Dissolve 5.6g of sodium citrate in a 20% nitric acid solution, then add 4.36g of Bi(NO3)3·5H2O and 0.433g of La(NO3)3·6H2O. Stir until Bi(NO3)3·5H2O and La(NO3)3·6H2O are fully dissolved to obtain the seventh solution.

[0128] Dissolve 5.6g of sodium citrate in a 20% nitric acid solution, then add 1.17g of NH4VO3 and stir until the NH4VO3 is fully dissolved to obtain the eighth solution.

[0129] The eighth solution was added to the seventh solution in batches and stirred to obtain the ninth solution.

[0130] After adjusting the pH value by adding 6.0 g of sodium hydroxide to the ninth solution, the ninth solution was placed in a reaction vessel and hydrothermally heated at 180 °C for 24 h. After filtration, lanthanum co-doped bismuth vanadate (La-BiVO4) was obtained.

[0131] Weigh 1.6g of La-BiVO4 powder and stir to disperse it in 105mL of water to obtain a La-BiVO4 suspension.

[0132] Add 4.35g Co(NO3)2·6H2O, 1.2g NH4F, and 4.5g CO(NH2)2 to a La-BiVO4 suspension, place it in a reactor, and hydrothermally heat it at 120℃ for 10h to obtain the precursor.

[0133] The precursor was placed in a muffle furnace and heat-treated at 350°C for 3 hours to obtain a cobalt tetroxide-coated lanthanum-doped bismuth vanadate (Co3O4@La-BiVO4) composite semiconductor material.

[0134] X-ray diffraction analysis showed that the Co3O4@La-BiVO4 material obtained in this embodiment has the same nanowire array structure as the Co3O4@La / Ce-BiVO4 obtained in Example 1.

[0135] Furthermore, BiVO4 materials, La-BiVO4 materials, and Ce-BiVO4 materials can also be prepared using the preparation methods provided in the embodiments of this disclosure. Examples 5-7 are used as examples for illustration.

[0136] Example 5

[0137] Dissolve 5.6g of sodium citrate in a 20% nitric acid solution, then add 4.85g of Bi(NO3)3·5H2O and stir until fully dissolved to obtain the tenth solution;

[0138] Dissolve 5.6g of sodium citrate in a 20% nitric acid solution, then add 1.17g of NH4VO3 and stir until fully dissolved to obtain the eleventh solution.

[0139] The eleventh solution was added in batches to the tenth solution, and the mixture was stirred to obtain the twelfth solution. After adjusting the pH value with 6.0 g of sodium hydroxide, the solution was placed in a reaction vessel and subjected to a hydrothermal reaction at 180 °C for 24 h. Subsequently, the solution was calcined in a muffle furnace at 350 °C to obtain BiVO4 material.

[0140] Example 6

[0141] Dissolve 5.6g of sodium citrate in a 20% nitric acid solution, then add 4.36g of Bi(NO3)3·5H2O and 0.434g of Ce(NO3)3·6H2O, and stir until Bi(NO3)3·5H2O and Ce(NO3)3·6H2O are fully dissolved to obtain the fourth solution.

[0142] Dissolve 5.6g of sodium citrate in a 20% nitric acid solution, then add 1.17g of NH4VO3 and stir until the NH4VO3 is fully dissolved to obtain the fifth solution.

[0143] The fifth solution was added to the fourth solution in batches and stirred to obtain the sixth solution.

[0144] After adjusting the pH value by adding 6.0 g of sodium hydroxide to the sixth solution, the sixth solution was placed at 180 °C for the first hydrothermal reaction for 24 h. After filtration, cerium-doped bismuth vanadate (Ce-BiVO4) was obtained.

[0145] Example 7

[0146] Dissolve 5.6g of sodium citrate in 20% dilute nitric acid, then add 4.36g of Bi(NO3)3·5H2O and 0.433g of La(NO3)3·6H2O, and stir until Bi(NO3)3·5H2O and La(NO3)3·6H2O are fully dissolved to obtain the seventh solution.

[0147] Dissolve 5.6g of sodium citrate in 20% dilute nitric acid, then add 1.17g of NH4VO3 and stir until the NH4VO3 is fully dissolved to obtain the eighth solution.

[0148] The eighth solution was added to the seventh solution in batches and stirred to obtain the ninth solution.

[0149] After adjusting the pH value by adding 6.0 g of sodium hydroxide to the ninth solution, the ninth solution was then subjected to hydrothermal treatment at 180 °C for 24 h to obtain lanthanum co-doped bismuth vanadate (La-BiVO4).

[0150] Results Analysis

[0151] The composite semiconductor materials prepared in Examples 1 and 2 were tested and analyzed.

[0152] I. Characterization of Co3O4@La / Ce-BiVO4 composite semiconductor materials

[0153] 1. Analysis of Scanning Electron Microscopy Results

[0154] The Co3O4@La / Ce-BiVO4 composite semiconductor material obtained in Example 1 was analyzed by scanning electron microscopy (SEM), and the results are as follows: Figure 1 As shown, the Co3O4@La / Ce-BiVO4 composite semiconductor material exhibits a three-dimensional needle-like nanowire array. Each "flower" in the flower-like nanowire array has a similar morphology and size, and the resulting nanowires are uniform in size, approximately 2 micrometers. The nanoarray structure of the Co3O4@La / Ce-BiVO4 composite semiconductor material can effectively increase the specific surface area of ​​the composite semiconductor material, improve the effective contact area of ​​electrodes prepared using this material, and thus enhance testing efficiency.

[0155] 2. X-ray diffraction analysis (XRD)

[0156] The crystal structure of the Co3O4@La / Ce-BiVO4 composite semiconductor material obtained in Example 1 was analyzed by X-ray diffraction (XRD), and the results are as follows: Figure 2 As shown. The diffraction peaks with 2θ values ​​at 18.85°, 28.85°, 30.54°, 34.38°, 35.19°, 39.91°, 42.40°, 46.00°, 46.82°, 47.25°, 50.00°, 50.26° and 53.21° correspond to the diffraction peaks of the crystal planes (110), (011), (121), (040), (200), (002), (141), (2l1), (101), (132), (240), (042), (202), (222) and (161) of BiVO4, respectively. Meanwhile, diffraction peaks (101), (220), (311), (222), (400), (422), (5l1), and (440) appear at 2θ values ​​of 19.0°, 31.1°, 36.8°, 38.6°, 44.8°, 55.6°, 59.3°, and 65.2°, which are characteristic diffraction peaks of Co3O4.

[0157] 3. Specific Surface Area Test (BET)

[0158] The Co3O4@La / Ce-BiVO4 composite semiconductor material obtained in Example 1 and the La / Ce-BiVO4 material obtained in Example 2 were subjected to nitrogen isothermal adsorption-desorption, and the obtained nitrogen adsorption-desorption curves are shown below. Figure 3 As shown. Before nitrogen isothermal adsorption-desorption, both materials were degassed at 120°C for 1 hour to remove impurities. According to the IUPAC classification standard, the nitrogen adsorption-desorption curves of the materials prepared in Examples 1 and 2 both belong to Category IV, i.e., mesoporous or macroporous adsorption curves. By comparison, the specific surface area of ​​the La / Ce-BiVO4 material is 6.7 m². 2 / g, while the specific surface area of ​​the Co3O4@La / Ce-BiVO4 composite semiconductor material is 18.1m². 2 / g. This indicates that Co3O4@La / Ce-BiVO4 has a large specific surface area. Taking the preparation of electrodes using Co3O4@La / Ce-BiVO4 as an example, it helps to increase the contact area of ​​the electrode, thereby improving the testing efficiency and sensitivity.

[0159] II. Photoelectric Performance Testing and Analysis of Co3O4@La / Ce-BiVO4 Composite Semiconductor Materials

[0160] The electrode prepared using the Co3O4@La / Ce-BiVO4 composite semiconductor material obtained in Example 1 is a Co3O4@La / Ce-BiVO4 electrode; the electrode prepared using the La / Ce-BiVO4 material obtained in Example 2 is a La / Ce-BiVO4 electrode.

[0161] 1. JV Testing and Result Analysis

[0162] A traditional three-electrode system was used, with a Co3O4@La / Ce-BiVO4 electrode as the working electrode, a platinum sheet electrode as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode. The electrolyte was a 0.5M Na2SO4 solution. The results are as follows: Figure 4 As shown in the figure, the photocurrent of the Co3O4@La / Ce-BiVO4 electrode gradually increases with increasing scanning voltage. Meanwhile, Figure 4 In the figure, the JV curve shows a linear increasing trend, which will enable the biosensor prepared by the Co3O4@La / Ce-BiVO4 electrode to have good detection sensitivity.

[0163] 2. Electrochemical impedance spectroscopy test and analysis

[0164] The migration and separation properties of photogenerated carriers can be characterized by electrochemical impedance spectroscopy. The AC impedance spectroscopy was also performed using a three-electrode system, with a Co3O4@La / Ce-BiVO4 electrode as the working electrode, a saturated silver / silver chloride electrode as the reference electrode, and a platinum sheet electrode as the counter electrode. The parameters were set as follows: initial voltage was the open-circuit voltage, high frequency 100000Hz, low frequency 0.1Hz, amplitude 20mV, 50mL of 0.5M Na2SO4 solution was added to the quartz electrolytic cell, and the light source was a 300W xenon lamp (model PLS-SXE300C) manufactured by Beijing Pofilai Co., Ltd.

[0165] In electrochemical impedance spectroscopy (EIS), the Nynquist plot is generally used for analysis. In the high-frequency region, the dynamics are controlled, and the graph is represented by an arc. The smaller the radius of this arc, the lower the impedance, and the faster the reaction rate at the electrode surface. In other words, the smaller the radius of the arc in the electrochemical impedance spectroscopy, the more efficient the separation of electrons and holes at the corresponding electrode, and the faster the separation and transport of charge at the electrode surface, resulting in better photoelectric performance. The electrochemical impedance spectroscopy results after mathematical fitting are shown below. Figure 5 As shown, under visible light irradiation, the radius of the Nynquist plot of the electrochemical impedance spectroscopy of the Co3O4@La / Ce-BiVO4 electrode is smaller than that of the La / Ce-BiVO4 electrode. This indicates that the Co3O4@La / Ce-BiVO4 composite semiconductor material is more effective in separating photogenerated electron-hole pairs. In other words, the charge migration rate on the surface of the Co3O4@La / Ce-BiVO4 electrode is faster, the recombination rate of electrons and holes is lower, and it exhibits superior optoelectronic performance.

[0166] 3. Stability Testing and Analysis

[0167] Backlighting was used, and a voltage of 0.62V was applied (vs. saturated Ag / AgCl electrode). For example... Figure 6 As shown, the current of the La / Ce-BiVO4 electrode and the Co3O4@La / Ce-BiVO4 electrode gradually decreases after being subjected to an external bias and light, and then the current tends to stabilize. Compared with the La / Ce-BiVO4 electrode, the Co3O4@La / Ce-BiVO4 electrode has a higher photocurrent density after stabilization. This shows that the Co3O4@La / Ce-BiVO4 composite semiconductor material has greater application value in the synthesis of composite electrodes.

[0168] It should be noted that although the steps of the method for preparing the composite semiconductor material in this disclosure are described in a specific order in the accompanying drawings, this does not require or imply that these steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0169] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. A method of producing a composite semiconductor material, characterized by, The method comprises the following steps: S1, obtaining a first solution and a second solution; The first solution comprises: obtaining a first sodium citrate solution, wherein the first sodium citrate solution is a nitric acid solution in which sodium citrate is dissolved; adding a bismuth source, a lanthanum source and a cerium source into the first sodium citrate solution to obtain the first solution; In the first sodium citrate solution, the amount of substance of sodium citrate is N, the amount of substance of bismuth in the bismuth source is x, the amount of substance of lanthanum in the lanthanum source is y, and the amount of substance of cerium in the cerium source is z, and N > x + y + z; The second solution comprises: obtaining a second sodium citrate solution, wherein the second sodium citrate solution is a nitric acid solution in which sodium citrate is dissolved; adding a vanadium source into the second sodium citrate solution to obtain the second solution; wherein the amount of substance of vanadium in the vanadium source is A, and x:y:z:A = (7-9):(0.5-1.5):(0.5-1.5):10 and x + y + z = A are satisfied; S2, adding the second solution into the first solution in batches to obtain a third solution; S3, adjusting the pH value of the third solution, and after the pH value of the third solution is adjusted to 4-8, performing a first hydrothermal reaction to obtain lanthanum and cerium doped bismuth vanadate; S4, dispersing the lanthanum and cerium doped bismuth vanadate obtained in step S3 in water to obtain a lanthanum and cerium doped bismuth vanadate suspension; adding a cobalt source, NH4F and CO(NH2)2 into the lanthanum and cerium doped bismuth vanadate suspension to perform a second hydrothermal reaction to obtain a precursor; wherein the molar ratio of the cobalt source, NH4F and CO(NH2)2 is 1:(1-2):(1-10); S5, placing the precursor obtained in step S4 in a reaction container to heat and calcine to obtain a three-cobalt-tetroxide-coated lanthanum and cerium doped bismuth vanadate composite semiconductor material.

2. The method of claim 1, wherein the semiconductor material is a compound semiconductor material. In step S1, the molar ratio of the bismuth element, the lanthanum element and the cerium element is 8:1:

1.

3. The method of claim 1, wherein the semiconductor material is a compound semiconductor material. In step S4, the molar ratio of the cobalt source, NH4F and CO(NH2)2 is 1:2:

5.

4. The method of claim 1, wherein the semiconductor material is a compound semiconductor material. In step S1, the bismuth source is Bi(NO3)3·5H2O, the lanthanum source is La(NO3)3·6H2O, the cerium source is Ce(NO3)3·6H2O, and the vanadium source is NH4VO3. In step S4, the cobalt source is Co(NO3)2·6H2O.

5. The method of claim 1, wherein the semiconductor material is a compound semiconductor material. In step S5, the mass ratio of the three-cobalt-tetroxide to the lanthanum and cerium doped bismuth vanadate in the three-cobalt-tetroxide-coated lanthanum and cerium doped bismuth vanadate is (20-40):

100.

6. The method of claim 1-5, wherein the method further comprises: In step S3, the pH value of the third solution is adjusted by using sodium hydroxide to adjust the pH value of the third solution to 7.

7. The method of claim 6, wherein the semiconductor material is a compound semiconductor material. In step S3, the first hydrothermal reaction is to place the third solution after the pH value is adjusted into a reaction kettle, and the hydrothermal reaction is performed at a temperature of 120-200℃ for 12-24h. In step S4, the second hydrothermal reaction is to place the lanthanum and cerium doped bismuth vanadate suspension into which the cobalt source, NH4F and CO(NH2)2 are added into a reaction kettle, and the hydrothermal reaction is performed at a temperature of 90-160℃ for 3-12h. In step S5, the heating calcination is to place the precursor in a muffle furnace, heat to 300-500℃ at a heating rate of 1-10℃ / min, and calcine for 2-5h.

8. A method of producing a composite semiconductor material, characterized by, The method comprises the following steps: S1, obtaining a seventh solution and an eighth solution; The obtaining of the seventh solution comprises: obtaining a fifth sodium citrate solution, the fifth sodium citrate solution being a nitric acid solution in which sodium citrate is dissolved; and adding a bismuth source and a lanthanum source into the fifth sodium citrate solution to obtain the seventh solution; Wherein, the amount of substance of sodium citrate in the fifth sodium citrate solution is N, the amount of substance of bismuth in the bismuth source is x, and the amount of substance of lanthanum in the lanthanum source is y, and N>x+y; The obtaining of the eighth solution comprises: obtaining a sixth sodium citrate solution, the sixth sodium citrate solution being a nitric acid solution in which sodium citrate is dissolved; and adding a vanadium source into the sixth sodium citrate solution to obtain the eighth solution; wherein the amount of substance of vanadium in the vanadium source is A, and x:y=(7-9):(0.5-1.5) is satisfied, and x+y=A; S2, adding the eighth solution into the seventh solution in batches to obtain a ninth solution; S3, adjusting the pH value of the ninth solution, and after the pH value of the ninth solution is adjusted to 4-8, performing a first hydrothermal reaction to obtain lanthanum-doped bismuth vanadate; S4, dispersing the lanthanum-doped bismuth vanadate obtained in step S3 in water to obtain a lanthanum-doped bismuth vanadate suspension; In the lanthanum-doped bismuth vanadate suspension, a cobalt source, NH4F and CO(NH2)2 are added, and a second hydrothermal reaction is performed to obtain a precursor; wherein the molar ratio of the cobalt source, NH4F and CO(NH2)2 is 1:(1-2):(1-10); S5, placing the precursor obtained in step S4 in a reaction container to perform heating calcination to obtain a cobalt trioxide four-oxygen-coated cerium-doped bismuth vanadate composite semiconductor material.

9. A method of producing a composite semiconductor material, characterized by, The method comprises the following steps: S1, obtaining a seventh solution and an eighth solution; The obtaining of the seventh solution comprises: obtaining a fifth sodium citrate solution, the fifth sodium citrate solution being a nitric acid solution in which sodium citrate is dissolved; and adding a bismuth source and a lanthanum source into the fifth sodium citrate solution to obtain the seventh solution; Wherein, the amount of substance of sodium citrate in the fifth sodium citrate solution is N, the amount of substance of bismuth in the bismuth source is x, and the amount of substance of lanthanum in the lanthanum source is y, and N>x+y; The obtaining of the eighth solution comprises: obtaining a sixth sodium citrate solution, the sixth sodium citrate solution being a nitric acid solution in which sodium citrate is dissolved; and adding a vanadium source into the sixth sodium citrate solution to obtain the eighth solution; wherein the amount of substance of vanadium in the vanadium source is A, and x:y=(7-9):(0.5-1.5) is satisfied, and x+y=A; S2, adding the eighth solution into the seventh solution in batches to obtain a ninth solution; S3, adjusting the pH value of the ninth solution, and after the pH value of the ninth solution is adjusted to 4-8, performing a first hydrothermal reaction to obtain lanthanum-doped bismuth vanadate; S4, dispersing the lanthanum-doped bismuth vanadate obtained in step S3 in water to obtain a lanthanum-doped bismuth vanadate suspension; A cobalt source, NH4F and CO(NH2)2 are added into the lanthanum-doped bismuth vanadate suspension to perform a second hydrothermal reaction to obtain a precursor; wherein the molar ratio of the cobalt source, NH4F and CO(NH2)2 is 1:(1-2):(1-10). S5, heating and calcining the precursor obtained in step S4 in a reaction container to obtain a lanthanum-doped bismuth vanadate composite semiconductor material coated with cobalt tetroxide.

10. A sensor electrode, characterized by The composite semiconductor material prepared by the preparation method of any one of claims 1-9.

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