Cu2O p-n homojunction composite photocatalytic nitrogen fixation material as well as preparation method and application thereof

Abstract

The invention relates to the field of photoelectric energy materials, in particular to a Cu2O p-n homojunction composite photocatalytic nitrogen fixation material, a preparation method and application, the method comprises the following steps: adding Pr (NO3) 3 and n-type I-Cu2O into a Cu2O reaction solution or adding KI and p-type Pr-Cu2O into the Cu2O reaction solution, and carrying out hydrothermal reaction to obtain the Cu2O p-n homojunction composite photocatalytic nitrogen fixation material. According to the method, a Cu2O p-n homojunction composite structure is constructed, a built-in electric field formed by p-type and n-type semiconductor interfaces is utilized, separation of photo-generated electrons and holes is accelerated, photo-generated carrier recombination is effectively inhibited, the stability and catalytic efficiency of the material are improved, and the problems of low catalytic activity and poor stability when Cu2O is used as a catalyst for synthesizing ammonia through light nitrogen fixation are solved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of photoelectric energy materials, in particular to a Cu2O p-n homojunction composite photocatalytic nitrogen fixation material, a preparation method and application. BACKGROUND

[0002] Nitrogen is an essential element for life and is widely present in the atmosphere in the form of nitrogen gas (N2). However, the two nitrogen atoms in the nitrogen molecule have a very stable triple bond, making it extremely inert in chemical properties and difficult for organisms to directly utilize. Therefore, converting nitrogen gas into nitrogen-containing compounds such as ammonia (NH3) is of great significance to agricultural production and industrial development.

[0003] Currently, the Haber-Bosch process is mainly used for large-scale industrial production of ammonia. Since its industrialization in 1913, it has been the mainstream technology for global ammonia production. The basic principle is to use iron-based catalysts to promote the reaction of nitrogen and hydrogen to produce ammonia under harsh conditions of high temperature and high pressure. Although the Haber-Bosch process has achieved great success in the field of ammonia production, providing a solid material basis for global food production and chemical industry, from the perspective of energy consumption, the Haber-Bosch process is an extremely energy-consuming process. With the increasing global energy demand and the increasing scarcity of energy resources, this high-energy production method undoubtedly puts great pressure on energy supply and exacerbates the severity of the global energy crisis.

[0004] Solar energy is a rich renewable energy source with the advantages of wide distribution, no pollution, and sustainability. Photocatalytic nitrogen fixation technology cleverly uses solar energy as the energy source for the reaction, avoiding dependence on traditional fossil fuels and fundamentally solving the problems of energy consumption and environmental pollution. Compared with traditional nitrogen fixation technology, photocatalytic nitrogen fixation technology provides a new way of thinking and approach to solve the traditional nitrogen fixation problem with its unique advantages. This technology uses solar energy, a clean and renewable energy source, as the driving force to convert nitrogen and water into ammonia under mild conditions of normal temperature and pressure, realizing true "green nitrogen fixation". The core of photocatalytic nitrogen fixation technology is the photocatalyst, which can initiate a series of complex chemical reactions under the excitation of solar energy to realize the conversion of nitrogen to ammonia. Currently, common photocatalysts mainly include metal oxides and semiconductor materials.

[0005] Among the many materials that can be used for photocatalysis, cuprous oxide (Cu2O) stands out as a typical narrow-band semiconductor. Its band gap (Eg) is approximately between 2.0-2.2 eV, which makes Cu2O with a narrow band gap have excellent absorption capacity in the visible light range. Since visible light accounts for a large proportion of the solar spectrum, Cu2O can be effectively excited by visible light, thus successfully initiating photocatalytic reactions and providing an adequate energy source for the photocatalytic process. Moreover, Cu2O has a unique electronic structure that facilitates the generation and separation of photo-generated carriers, to some extent, promoting the progress of photocatalytic reactions. At the same time, Cu2O also has the significant advantages of low cost and easy preparation, with abundant and low-cost copper sources, and simple preparation methods such as chemical precipitation, electrochemical deposition, and hydrothermal synthesis, which do not require complex equipment and harsh reaction conditions, making it easy to mass-produce, which lays a solid foundation for its promotion in practical applications. Based on the above advantages, Cu2O has rapidly become a research hotspot in the field of photocatalytic nitrogen fixation, attracting the attention and investment of numerous researchers.

[0006] Although Cu2O shows promising prospects in photocatalytic nitrogen fixation, it still faces some key problems that need to be solved as a photocatalyst. Among them, the high recombination probability of photo-generated electron-hole pairs is one of the main factors restricting the improvement of its photocatalytic performance. During the photocatalytic reaction process, Cu2O absorbs photons to produce photo-generated electrons and holes, which should participate in reactions such as the reduction of nitrogen and the oxidation of water. However, due to the strong Coulomb attraction within Cu2O and defects in the crystal structure, photo-generated electrons and holes are prone to recombine in a short time, greatly reducing the number of effective carriers that can participate in the reaction, thus severely reducing the photocatalytic activity. In addition, the stability of Cu2O during the photocatalytic reaction process is also poor, and under the action of light and reaction medium, its crystal structure is easily changed, and the surface properties will gradually deteriorate, thus leading to a rapid decline in photocatalytic performance with the extension of reaction time, which is difficult to meet the long-term stable operation requirements of practical applications. These problems greatly limit the further development and large-scale application of Cu2O in the field of photocatalytic nitrogen fixation, therefore, how to effectively reduce the recombination rate of photo-generated electron-hole pairs, improve the photocatalytic activity, and enhance the stability, has become an important problem that needs to be overcome in the current research of Cu2O photocatalysis. SUMMARY

[0007] In view of the problems that Cu2O as a catalyst has low catalytic activity and poor stability due to high recombination probability of photo-generated electron-hole pairs and low carrier concentration in the synthesis of ammonia by photocatalytic nitrogen fixation in the prior art, the present application provides a Cu2O p-n homojunction composite photocatalytic nitrogen fixation material, a preparation method and applications.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for preparing a Cu2O pn homojunction composite photocatalytic nitrogen fixation material, comprising: Pr(NO3)3 and n-type I-Cu2O are added to the Cu2O reaction solution, or KI and p-type Pr-Cu2O are added to the Cu2O reaction solution, and a hydrothermal reaction is carried out to obtain a Cu2O pn homojunction composite photocatalytic nitrogen fixation material; The n-type I-Cu2O is obtained by adding KI to a Cu2O reaction solution and performing a hydrothermal reaction, and the p-type Pr-Cu2O is obtained by adding Pr(NO3)3 to a Cu2O reaction solution and performing a hydrothermal reaction.

[0009] Optionally, the Cu2O reaction solution is obtained by: Evenly mixing the copper acetate solution, the NaOH solution and the glucose solution to obtain a first mixed solution; Polyvinyl pyrrolidone is added to the first mixed solution to obtain a Cu2O reaction solution.

[0010] Optionally, the concentration of the copper acetate solution is 0.15-0.25 g / mL; the concentration of the NaOH solution is 0.7-0.9 mol / L; the concentration of the glucose solution is 1-1.5 mol / L; the volume ratio of the copper acetate solution, the NaOH solution and the glucose solution is 3:1:1; the concentration of polyvinyl pyrrolidone after adding polyvinyl pyrrolidone to the first mixed solution is 0.01-0.04 g / mL.

[0011] Optionally, the n-type I-Cu2O is prepared by adding KI to a Cu2O reaction solution and performing a hydrothermal reaction, comprising: KI is added to the Cu2O reaction solution, and the reaction is carried out at 80°C to 100°C for 10 to 18 hours to obtain n-type I-Cu2O; wherein, after the KI is added to the Cu2O reaction solution, the concentration of the KI is 0.0002 to 0.0004 g / mL.

[0012] Optionally, the p-type Pr-Cu2O is prepared by adding Pr(NO3)3 to a Cu2O reaction solution and performing a hydrothermal reaction, comprising: Pr(NO3)3 is added to the Cu2O reaction solution, and the reaction is carried out at 80°C to 100°C for 10 to 18 hours to obtain p-type Pr-Cu2O; wherein, after adding Pr(NO3)3 to the Cu2O reaction solution, the concentration of Pr(NO3)3 is 0.0002 to 0.0006 g / mL.

[0013] Optionally include: Pr(NO3)3 and n-type I-Cu2O are added to the Cu2O reaction solution and subjected to a hydrothermal reaction to obtain a Cu2O pn homojunction composite photocatalytic nitrogen fixation material; Among them, after adding Pr(NO3)3 and n-type I-Cu2O to the Cu2O reaction solution, the concentration of Pr(NO3)3 is 0.0002~0.0006 g / mL, and the concentration of n-type I-Cu2O is 0.0002~0.0008 g / mL.

[0014] Optionally include: KI and p-type Pr-Cu2O are added to the Cu2O reaction solution and subjected to a hydrothermal reaction to obtain a Cu2O pn homojunction composite photocatalytic nitrogen fixation material; Wherein, after adding KI and p-type Pr-Cu2O to the Cu2O reaction solution, the concentration of KI is 0.0002-0.0004 g / mL, and the concentration of p-type Pr-Cu2O is 0.0002-0.0008 g / mL.

[0015] Optionally, the method of adding Pr(NO3)3 and n-type I-Cu2O to the Cu2O reaction solution or adding KI and p-type Pr-Cu2O to the Cu2O reaction solution and performing a hydrothermal reaction to obtain the Cu2O pn homojunction composite photocatalytic nitrogen fixation material is: Pr(NO3)3 and n-type I-Cu2O are added to the Cu2O reaction solution, or KI and p-type Pr-Cu2O are added to the Cu2O reaction solution, and a hydrothermal reaction is carried out at 80°C to 100°C for 10 to 18 hours to obtain a Cu2O pn homojunction composite photocatalytic nitrogen fixation material.

[0016] The present invention also provides a Cu2O pn homojunction composite photocatalytic nitrogen fixation material, which is prepared using the above preparation method.

[0017] For example, the application of the Cu2O pn homojunction composite photocatalytic nitrogen fixation material in photocatalytic nitrogen fixation.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The application provides a preparation method of Cu2O p-n homojunction composite photocatalytic nitrogen fixation material.

[0019] The application provides a Cu2O p-n homojunction composite photocatalytic nitrogen fixation material, which is prepared by the above method. A built-in electric field is formed at the interface of the p-type and n-type Cu2O in the Cu2O p-n homojunction composite photocatalytic nitrogen fixation material, photo-generated electrons migrate from the conduction band of the n-type Cu2O to the valence band of the p-type Cu2O, and holes migrate in the opposite direction. This directional migration effectively inhibits the electron-hole recombination, prolongs the carrier lifetime, and at the same time, the combination of the p-type Pr-Cu2O and the n-type I-Cu2O may form a synergistic light absorption effect, enhance the utilization efficiency of the material to visible light, realize the overall optimization of N2 reduction thermodynamics, carrier separation kinetics, surface reaction activity and material stability, and provide a key band engineering strategy for the design of high-efficiency and stable photocatalytic nitrogen fixation material.

[0020] The Cu2O p-n homojunction composite photocatalytic nitrogen fixation material is applied to photocatalytic nitrogen fixation. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 XRD patterns of Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared for embodiments 1 to 3 of the present application.

[0022] Figure 2 XRD patterns of Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared for embodiments 5 to 8 of the present application.

[0023] Figure 3 Comparison of XRD patterns of Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared for embodiments 1 and 7 of the present application.

[0024] Figure 4 XPS patterns of Cu2O p-n homojunction composite photocatalytic nitrogen fixation material prepared for embodiment 7 of the present application, wherein a is a full spectrum, b is an O 1s high-resolution spectrum, c is a Cu 2p high-resolution spectrum, d is an I 3d high-resolution spectrum, and e is a Pr 3d high-resolution spectrum.

[0025] Figure 5 SEM images of Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared for embodiments 1 and 7 of the present application, wherein a is an SEM image of Cu2O p-n homojunction composite photocatalytic nitrogen fixation material prepared for embodiment 1, b is an SEM image of Cu2O p-n homojunction composite photocatalytic nitrogen fixation material prepared for embodiment 7, c is an SEM image of n-type I-Cu2O, d is an SEM image of p-type Pr-Cu2O, and e is an EDAX image of Cu2O p-n homojunction composite photocatalytic nitrogen fixation material prepared for embodiment 7.

[0026] Figure 6These are BET analysis diagrams of the Cu2O pn homojunction composite photocatalytic nitrogen-fixing materials prepared in Examples 1, 7, and 8 of the present invention, wherein a is the N2 adsorption-desorption isotherm and pore size distribution diagram of n-type I-Cu2O, b is the N2 adsorption-desorption isotherm and pore size distribution diagram of the Cu2O pn homojunction composite photocatalytic nitrogen-fixing material prepared in Example 1, c is the N2 adsorption-desorption isotherm and pore size distribution diagram of the Cu2O pn homojunction composite photocatalytic nitrogen-fixing material prepared in Example 7, and d is the N2 adsorption-desorption isotherm and pore size distribution diagram of the Cu2O pn homojunction composite photocatalytic nitrogen-fixing material prepared in Example 8.

[0027] Figure 7 The UV-Vis DRS analysis diagrams of Cu2O, Cu2O pn homojunction composite photocatalytic nitrogen fixation materials prepared in Example 1 and Example 7 of the present invention, wherein a is the UV-Vis DRS diagram, and b is (αhν) 2 -hν diagram.

[0028] Figure 8 The photoluminescence spectra of homojunction particles of n-type I-Cu2O and Cu2O pn homojunction composite photocatalytic nitrogen fixation materials prepared in Examples 1, 7 and 8 of the present invention.

[0029] Figure 9 Graphs showing the electrochemical performance of n-type I-Cu2O and Cu2O pn homojunction composite photocatalytic nitrogen fixation materials prepared in Examples 1 and 7 of the present invention, where a is the photoinduced current-time image and b is the AC impedance curve.

[0030] Figure 10 Mott-Schottky plots of I-Cu2O and the Cu2O pn homojunction composite photocatalytic nitrogen-fixing materials prepared in Examples 1 and 7 of the present invention, wherein a is the Mott-Schottky plot of n-type I-Cu2O, b is the Mott-Schottky plot of the Cu2O pn homojunction composite photocatalytic nitrogen-fixing material prepared in Example 1, and c is the Mott-Schottky plot of the Cu2O pn homojunction composite photocatalytic nitrogen-fixing material prepared in Example 7.

[0031] Figure 11The degradation curve of moxifloxacin by n-type I-Cu2O and Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared in Example 1 and Example 7 of the present application, wherein a is the degradation curve of moxifloxacin by n-type I-Cu2O, b is the degradation curve of moxifloxacin by Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared in Example 1 of the present application, and c is the degradation curve of moxifloxacin by Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared in Example 7 of the present application.

[0032] Figure 12 The degradation rate curve and kinetic curve in the process of photocatalytic degradation of moxifloxacin by n-type I-Cu2O and Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared in Example 1 and Example 7 of the present application, wherein a is the degradation rate curve, and b is the kinetic curve.

[0033] Figure 13 The degradation rate curve in the process of photocatalytic degradation of norfloxacin (NOR) by n-type I-Cu2O and Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared in Example 1 and Example 7 of the present application, wherein a is the degradation curve of I-Cu2O for norfloxacin, b is the degradation curve of Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared in Example 1 of the present application for norfloxacin, and c is the degradation curve of Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared in Example 7 of the present application for norfloxacin.

[0034] Figure 14 The degradation rate curve and kinetic curve in the process of photocatalytic degradation of norfloxacin by I-Cu2O and Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared in Example 1 and Example 7 of the present application, wherein a is the degradation rate curve, and b is the kinetic curve.

[0035] Figure 15 The stability test result graph of Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared in Example 7 of the present application, wherein a is the XRD spectrum after 5 times of reuse, and b is the photocatalytic degradation rate graph after 5 times of reuse.

[0036] Figure 16 The UV-visible light degradation of norfloxacin by Cu2O p-n homojunction composite photocatalytic nitrogen fixation materials prepared in Example 7 of the present application with different capture agents, wherein a is the UV-visible light degradation of norfloxacin with MT added, b is the UV-visible light degradation of norfloxacin with IPA added, c is the UV-visible light degradation of norfloxacin with BQ added, and d is the degradation rate curve.

[0037] Figure 17The VB-XPS spectrum of the Cu2O p-n homojunction composite photocatalytic nitrogen fixation material prepared for Example 7.

[0038] Figure 18 The photocatalytic mechanism diagram of the Cu2O p-n homojunction composite photocatalytic nitrogen fixation material of the present application. DETAILED DESCRIPTION

[0039] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0040] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0041] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0042] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "horizontal", "inner" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the present application is used, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0043] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0044] In the description of the embodiments of the present application, it also needs to be explained that, unless explicitly specified and limited, if the terms "arrange", "install", "connect", "connect" appear, they should be understood in a broad sense, for example, they can be fixedly connected, or can be detachably connected, or integrally connected; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium, or can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0045] The present application will be further described in detail below in conjunction with specific embodiments, which are an explanation of the present application rather than a limitation.

[0046] Reference Figure 1 The present application discloses a preparation method of Cu2O p-n homojunction composite photocatalytic nitrogen fixation material, comprising: The copper acetate solution, the NaOH solution and the glucose solution are mixed uniformly to obtain a first mixed solution, specifically, the copper acetate solution with a concentration of 0.15-0.25 g / mL is added with the NaOH solution with a concentration of 0.7-0.9 mol / L and the glucose solution with a concentration of 1-1.5 mol / L, so that the volume ratio of the copper acetate solution, the NaOH solution and the glucose solution is 3:1:1, to obtain the first mixed solution; it is noted that when the NaOH solution is added, the addition rate of the NaOH solution is controlled at 0.1-0.3 mL / s, and stirring is performed while adding, polyvinylpyrrolidone is added to the first mixed solution, so that the concentration of the polyvinylpyrrolidone is 0.01-0.04 g / mL, and ultrasonic mixing is performed to obtain a Cu2O reaction solution; Pr(NO3)3 and n-type I-Cu2O are added to the Cu2O reaction solution or KI and p-type Pr-Cu2O are added to the Cu2O reaction solution, and hydrothermal reaction is performed at 80-100°C for 10-18h to obtain the Cu2O p-n homojunction composite photocatalytic nitrogen fixation material. In the Cu2O p-n homojunction composite photocatalytic nitrogen fixation material obtained by adding Pr(NO3)3 and n-type I-Cu2O to the Cu2O reaction solution and performing hydrothermal reaction, after Pr(NO3)3 and n-type I-Cu2O are added to the Cu2O reaction solution, the concentration of Pr(NO3)3 is 0.0002-0.0006 g / mL, and the concentration of n-type I-Cu2O is 0.0002-0.0008 g / mL. In the Cu2O p-n homojunction composite photocatalytic nitrogen fixation material obtained by adding KI and p-type Pr-Cu2O to the Cu2O reaction solution and performing hydrothermal reaction, after KI and p-type Pr-Cu2O are added to the Cu2O reaction solution, the concentration of KI is 0.0002-0.0004 g / mL, and the concentration of p-type Pr-Cu2O is 0.0002-0.0008 g / mL.

[0047] The n-type I-Cu2O is prepared by adding KI into the Cu2O reaction solution and performing hydrothermal reaction, including: KI is added into the Cu2O reaction solution, and reacted at 80-100°C for 10-18h to obtain the n-type I-Cu2O; wherein after the KI is added into the Cu2O reaction solution, the concentration of the KI is 0.0002-0.0004 g / mL.

[0048] The p-type Pr-Cu2O is prepared by adding Pr(NO3)3 into the Cu2O reaction solution and performing hydrothermal reaction, including: Pr(NO3)3 is added into the Cu2O reaction solution, and reacted at 80-100°C for 10-18h to obtain the p-type Pr-Cu2O; wherein after the Pr(NO3)3 is added into the Cu2O reaction solution, the concentration of the Pr(NO3)3 is 0.0002-0.0006 g / mL.

[0049] Example 1 0.6 g copper acetate is dissolved in 30 mL deionized water, 10.0 mL of 0.8 mol / L NaOH solution is slowly added dropwise, 10 mL of 1.1 mol / L glucose solution and 1 g of polyvinylpyrrolidone are added after ultrasonic treatment for 10 min to obtain a Cu2O reaction solution.

[0050] 0.02 g Pr(NO3)3 is weighed and added into the above Cu2O reaction solution, ultrasonic oscillation is performed for 30 min, 10 mg of n-type I-Cu2O is added, and reacted at 90°C for 14 h, and then washed with anhydrous ethanol and deionized water alternately for 3 times, and dried to obtain a Cu2O p-n homojunction composite photocatalytic nitrogen fixation material, which is recorded as M1.

[0051] The preparation method of the n-type I-Cu2O is as follows: 0.6 g of copper acetate Cu(CH3COO)2 is dissolved in 30 mL of deionized water, 10 mL of 0.8 mol / L NaOH solution is slowly added dropwise, 10 mL of 1.1 mol / L glucose solution is added after ultrasonic treatment for 10 min, 1 g of polyvinylpyrrolidone is added, ultrasonic treatment is performed for 20 min, KI is added to make the concentration of the KI be 0.0003 g / mL, ultrasonic oscillation is performed for 30 min, and reacted at 90°C for 24 h. After cooling to room temperature, washed with anhydrous ethanol and deionized water alternately for 3 times, and dried in an oven with a temperature of 60°C to obtain the n-type I-Cu2O, which is recorded as S2.

[0052] Example 2 0.6 g of copper acetate was dissolved in 30 mL of deionized water, and 10.0 mL of 0.8 mol / L NaOH solution was slowly added dropwise. After ultrasonication for 10 min, 10 mL of 1.1 mol / L glucose solution and 1 g of polyvinylpyrrolidone were added to obtain a Cu2O reaction solution.

[0053] 0.02 g Pr(NO3)3 was weighed and added to the above Cu2O reaction solution. After ultrasonic vibration for 30 min, 20 mg of n-type I-Cu2O was added and reacted at 90°C for 14 h. After alternating centrifugation and washing with anhydrous ethanol and deionized water for 3 times, the mixture was dried to obtain a Cu2O pn homojunction composite photocatalytic nitrogen fixation material, which was recorded as M2.

[0054] The preparation method for n-type I-Cu2O is as follows: 0.6 g of copper acetate (Cu(CH3COO)2) was dissolved in 30 mL of deionized water, 10 mL of 0.8 mol / L NaOH solution was slowly added dropwise, and after sonication for 10 minutes, 10 mL of 1.1 mol / L glucose solution was added. 1 g of polyvinylpyrrolidone was added and sonicated for 20 minutes. Then, KI was added to a concentration of 0.0003 g / mL, and sonication was continued for 30 minutes. The reaction was carried out at 90°C for 24 hours. After cooling to room temperature, the mixture was washed three times with anhydrous ethanol and deionized water, and then placed in an oven at 60°C for drying to obtain n-type I-Cu2O, which was designated as S2.

[0055] Example 3 0.6 g of copper acetate was dissolved in 30 mL of deionized water, and 10.0 mL of 0.8 mol / L NaOH solution was slowly added dropwise. After ultrasonication for 10 min, 10 mL of 1.1 mol / L glucose solution and 1 g of polyvinylpyrrolidone were added to obtain a Cu2O reaction solution.

[0056] 0.02 g Pr(NO3)3 was weighed and added to the above Cu2O reaction solution. After ultrasonic vibration for 30 min, 30 mg of n-type I-Cu2O was added and reacted at 90°C for 14 h. After alternating centrifugation and washing with anhydrous ethanol and deionized water for three times, the mixture was dried to obtain a Cu2O pn homojunction composite photocatalytic nitrogen fixation material, which was recorded as M3.

[0057] The preparation method of the n-type I-Cu2O is as follows: 0.6 g of copper acetate Cu(CH3COO)2 is dissolved in 30 mL of deionized water, 10 mL of NaOH solution with a concentration of 0.8 mol / L is slowly added dropwise, 10 mL of glucose solution with a concentration of 1.1 mol / L is added after ultrasonic treatment for 10 min, 1 g of polyvinylpyrrolidone is added, ultrasonic treatment is performed for 20 min, KI is added so that the concentration of the KI is 0.0003 g / mL, ultrasonic oscillation is performed for 30 min, and reaction is performed at 90°C for 24 h. After being cooled to room temperature, the n-type I-Cu2O is obtained by alternately centrifugally cleaning three times with anhydrous ethanol and deionized water, and drying in an oven with a temperature of 60°C, and is denoted as S2.

[0058] Example 4 The Cu2O reaction solution is obtained by dissolving 0.6 g of copper acetate in 30 mL of deionized water, slowly adding dropwise 10 mL of NaOH solution with a concentration of 0.8 mol / L, and adding 10 mL of glucose solution with a concentration of 1.1 mol / L and 1 g of polyvinylpyrrolidone after ultrasonic treatment for 10 min.

[0059] 0.015 g of KI is weighed and added into the Cu2O reaction solution, ultrasonic oscillation is performed for 30 min, 10 mg of p-type Pr-Cu2O is added, reaction is performed at 90°C for 14 h, after being cooled to room temperature, the Cu2O p-n homojunction composite photocatalytic nitrogen fixation material is obtained by alternately centrifugally cleaning three times with anhydrous ethanol and deionized water, and drying, and is denoted as N1.

[0060] The preparation method of the p-type Pr-Cu2O is as follows: The Cu2O reaction solution is obtained by dissolving 0.6 g of copper acetate in 30 mL of deionized water, slowly adding dropwise 10 mL of NaOH solution with a concentration of 0.8 mol / L, and adding 10 mL of glucose solution with a concentration of 1.1 mol / L and 1 g of polyvinylpyrrolidone after ultrasonic treatment for 10 min.

[0061] Example 5 The Cu2O reaction solution is obtained by dissolving 0.6 g of copper acetate in 30 mL of deionized water, slowly adding dropwise 10 mL of NaOH solution with a concentration of 0.8 mol / L, and adding 10 mL of glucose solution with a concentration of 1.1 mol / L and 1 g of polyvinylpyrrolidone after ultrasonic treatment for 10 min.

[0062] Take 0.015 g of KI and add it to the Cu2O reaction solution described above, ultrasonic oscillation for 30 min, add 10 mg of p-type Pr-Cu2O, react at 90℃ for 14 h, after cooling to room temperature, use anhydrous ethanol and deionized water alternately for 3 times, dry, get Cu2O p-n homojunction composite photocatalytic nitrogen fixation material, recorded as N1.

[0063] The preparation method of the p-type Pr-Cu2O is: Dissolve 0.6 g of copper acetate in 30 mL of deionized water, slowly drop 10 mL of 0.8 mol / L NaOH solution, ultrasonic for 10 min, then add 10 mL of 1.1 mol / L glucose solution and 1 g of polyvinylpyrrolidone, ultrasonic for 20 min, then add Pr(NO3)3, so that the concentration of KI is 0.0004 g / mL, ultrasonic oscillation for 30 min, react at 90℃ for 24 h. After cooling to room temperature, use anhydrous ethanol and deionized water alternately for 3 times, dry in an oven with a temperature of 60℃, get n-type I-Cu2O, recorded as R2.

[0064] Example 6 Dissolve 0.6 g of copper acetate in 30 mL of deionized water, slowly drop 10 mL of 0.8 mol / L NaOH solution, ultrasonic for 10 min, then add 10 mL of 1.1 mol / L glucose solution and 1 g of polyvinylpyrrolidone, get Cu2O reaction solution.

[0065] Take 0.015 g of KI and add it to the Cu2O reaction solution described above, ultrasonic oscillation for 30 min, add 10 mg of p-type Pr-Cu2O, react at 90℃ for 14 h, after cooling to room temperature, use anhydrous ethanol and deionized water alternately for 3 times, dry, get Cu2O p-n homojunction composite photocatalytic nitrogen fixation material, recorded as N1.

[0066] The preparation method of the p-type Pr-Cu2O is: 0.6 g copper acetate was dissolved in 30 mL deionized water, 10 mL NaOH solution with a concentration of 0.8 mol / L was slowly added dropwise, 10 mL glucose solution with a concentration of 1.1 mol / L was added after ultrasonic treatment for 10 min, 1 g of polyvinylpyrrolidone was added, and Pr(NO3)3 was added after ultrasonic treatment for 20 min, so that the concentration of KI was 0.0004 g / mL, and ultrasonic oscillation was performed for 30 min, and reaction was performed at 90°C for 24 h. After cooling to room temperature, the product was washed with anhydrous ethanol and deionized water alternately for 3 times, and then dried in an oven at 60°C to obtain n-type I-Cu2O, which was denoted as R2.

[0067] Example 7 0.6 g copper acetate was dissolved in 30 mL deionized water, 10 mL NaOH solution with a concentration of 0.8 mol / L was slowly added dropwise, 10 mL glucose solution with a concentration of 1.1 mol / L was added after ultrasonic treatment for 10 min, and 1 g of polyvinylpyrrolidone was added to obtain a Cu2O reaction solution.

[0068] 0.015 g of KI was weighed and added to the Cu2O reaction solution, ultrasonic oscillation was performed for 30 min, 30 mg of p-type Pr-Cu2O was added, and reaction was performed at 90°C for 14 h. After cooling to room temperature, the product was washed with anhydrous ethanol and deionized water alternately for 3 times, and then dried to obtain a Cu2O p-n homojunction composite photocatalytic nitrogen fixation material, which was denoted as N3.

[0069] The preparation method of the p-type Pr-Cu2O is as follows: 0.6 g copper acetate was dissolved in 30 mL deionized water, 10 mL NaOH solution with a concentration of 0.8 mol / L was slowly added dropwise, 10 mL glucose solution with a concentration of 1.1 mol / L was added after ultrasonic treatment for 10 min, 1 g of polyvinylpyrrolidone was added, and Pr(NO3)3 was added after ultrasonic treatment for 20 min, so that the concentration of KI was 0.0004 g / mL, and ultrasonic oscillation was performed for 30 min, and reaction was performed at 90°C for 24 h. After cooling to room temperature, the product was washed with anhydrous ethanol and deionized water alternately for 3 times, and then dried in an oven at 60°C to obtain n-type I-Cu2O, which was denoted as R2.

[0070] Example 8 0.6 g copper acetate was dissolved in 30 mL deionized water, 10 mL NaOH solution with a concentration of 0.8 mol / L was slowly added dropwise, 10 mL glucose solution with a concentration of 1.1 mol / L was added after ultrasonic treatment for 10 min, and 1 g of polyvinylpyrrolidone was added to obtain a Cu2O reaction solution.

[0071] Take 0.015 g of KI and add it to the reaction solution of Cu2O described above, ultrasonic oscillation for 30 min, add 40 mg of p-type Pr-Cu2O, and react at 90℃ for 14 h. After cooling to room temperature, use anhydrous ethanol and deionized water alternately for centrifugal cleaning for 3 times, and dry to obtain a Cu2O p-n homojunction composite photocatalytic nitrogen fixation material, which is recorded as N4.

[0072] The preparation method of the p-type Pr-Cu2O is as follows: Dissolve 0.6 g of copper acetate in 30 mL of deionized water, slowly drop 10 mL of NaOH solution with a concentration of 0.8 mol / L, add 10 mL of glucose solution with a concentration of 1.1 mol / L after ultrasonic oscillation for 10 min, add 1 g of polyvinylpyrrolidone, and ultrasonic oscillation for 20 min. Then, add Pr(NO3)3 so that the concentration of KI is 0.0004 g / mL, ultrasonic oscillation for 30 min, and react at 90℃ for 24 h. After cooling to room temperature, use anhydrous ethanol and deionized water alternately for centrifugal cleaning for 3 times, and dry in an oven with a temperature of 60℃ to obtain n-type I-Cu2O, which is recorded as R2.

[0073] Example 9 Different from example 1, when preparing the Cu2O reaction solution, the concentration of copper acetate solution is 0.15 g / mL, the concentration of NaOH solution is 0.7 mol / L, and the addition amount of polyvinylpyrrolidone is 0.5 g; and the addition amount of Pr(NO3)3 is 0.01 g. The preparation method of n-type I-Cu2O is unchanged.

[0074] Example 10 Different from example 1, when preparing the Cu2O reaction solution, the concentration of copper acetate solution is 0.25 g / mL, the concentration of NaOH solution is 0.9 mol / L, and the addition amount of polyvinylpyrrolidone is 1.5 g; and the addition amount of Pr(NO3)3 is 0.03 g. The preparation method of n-type I-Cu2O is unchanged.

[0075] Example 11 Different from example 5, the addition amount of KI is 0.01 g, the temperature of hydrothermal reaction is 100℃, and the time is 12 h. The preparation method of p-type Pr-Cu2O is unchanged.

[0076] Example 12 Different from example 5, the addition amount of KI is 0.02 g, the temperature of hydrothermal reaction is 80℃, and the time is 18 h. The preparation method of p-type Pr-Cu2O is unchanged.

[0077] To further illustrate the beneficial effects of the present application, examples 1-8 are characterized and performance tested: XRD analysis of p-n Cu2O homojunction composite photocatalytic nitrogen fixation materials under different n-type I-Cu2O addition amounts, see Figure 1 It can be found from the figure that the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material does not change the diffraction peak position of the p-type Pr-Cu2O particles. The diffraction peak intensity of the (111) crystal plane of the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material is greatly improved compared with the sample p-type Pr-Cu2O. With the increase of the content of n-type I-Cu2O, the diffraction peak intensity of the (111) crystal plane of the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material first increases and then decreases. When 10 mg of n-type I-Cu2O is added, the (111) crystal plane diffraction peak of the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material is the highest, and the ratio of the diffraction peak intensity of the (111) crystal plane to the (200) crystal plane is the largest. Therefore, the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material obtained by adding 10 mg of S2 particles has the optimal stability and photocatalytic performance.

[0078] XRD analysis of p-n Cu2O homojunction composite photocatalytic nitrogen fixation materials under different p-type Pr-Cu2O addition amounts, see Figure 2 It can be found from the figure that different addition methods do not change the crystal form of Cu2O particles, and the diffraction peak positions correspond to the (110), (111), (200), (220), and (311) crystal planes of Cu2O, respectively. It can be found that the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material does not change the diffraction peak position of Cu2O, which is still consistent with the Cu2O standard card (JCPDS NO 05-0667). With the increase of the content of p-type Pr-Cu2O (R2) particles, the diffraction peak intensity of the (111) crystal plane of the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material first increases and then decreases compared with the sample R2. The (111) crystal plane diffraction peak of the samples N3 and N4 prepared by adding 30 mg and 40 mg is higher. After comparison, the (111) crystal plane diffraction peak of N3 is the highest, and the ratio of the diffraction peak intensity of the (111) crystal plane to the (200) crystal plane is the largest. Therefore, the p-n Cu2O obtained by adding 30 mg of R2 particles when preparing S2 particles has the optimal stability and photocatalytic performance.

[0079] M1 prepared in Example 1 and N3 prepared in Example 7 were selected for comparative analysis, see Figure 3The peak positions of the samples prepared by different addition methods are consistent with the Cu2O standard card (JCPDS NO05-0667), and no other impurity peaks appear, indicating that the prepared samples are of high purity. N3 has a higher (111) crystal plane diffraction peak, so when preparing the optimal n-type semiconductor S2, adding 30 mg of the optimal p-type semiconductor R2 particles to prepare sample N3 has even better photocatalytic performance.

[0080] XPS analysis of N3 prepared in Example 7 is performed, see Figure 4 , from the figure, we can observe the peaks of Cu 2p, O 1s, I 3d and Pr 3d, which shows that the prepared N3 is composed of O, Cu, I and Pr elements, which further confirms the successful preparation of pn Cu2O homojunction composite photocatalytic nitrogen fixation material. From the high-resolution spectrum of O 1s, three peaks were obtained after XPS Peak fitting, among which the peak at the binding energy of 529.9 eV corresponds to oxygen in the Cu2O lattice; the peak at the binding energy of 531.1eV is the oxygen vacancy defect. The larger the peak value, the larger the oxygen defect, which indicates that the adsorption performance of the prepared composite particles is stronger; the peak at the binding energy of 532.1eV corresponds to the chemical adsorption on the surface of N3. The high-resolution XPS spectrum of Cu 2p, and after XPSPeak fitting, two peaks were obtained, the two peaks at 932.2 and 952.1eV, which correspond to the Cu 2p 3 / 2 and Cu 2p 1 / 2 binding energies of Cu2O, respectively, which shows that the copper element in the sample is in the form of Cu + The high-resolution XPS spectrum of I 3d shows that the binding energies at 619.2 and 630.6 eV correspond to I - I 3d 5 / 2 and I 3d 3 / 2 orbitals, which also shows that iodine is I - The high-resolution XPS spectrum of Pr 3d shows that the binding energies at 931.9 and 951.7 eV correspond to those of Pr 4+ Pr 3d 5 / 2 and Pr 3d 3 / orbitals, combined with this also shows that praseodymium is successfully doped into the sample and is in the form of Pr 4+ exists in the form of .

[0081] SEM analysis was performed on M1 and N3 prepared in Example 1 and Example 7, see Figure 5It can be seen from the figure that R2 microparticles present a spherical shape with surface concave-convex defects, and most of M1 microparticles present a spherical shape, with a small number of cubic microparticles and the corners being smoothed. This is because the S2 additive amount is too small and the melt crystal phenomenon occurs. It can be seen from the SEM spectrum of N3 that S2 microparticles present a cubic morphology, M1 particles are relatively uniform, and there is a p-n nodular surface, which also indicates that the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material is successfully prepared. Therefore, compared with sample M1, N3 has more obvious p-n nodular surface, which also indicates that sample N3 has better performance.

[0082] The prepared p-n Cu2O homojunction composite photocatalytic nitrogen fixation material was subjected to BET analysis, and M1, N3 and N4 prepared in the above examples were subjected to BET analysis test, and the results are shown in Figure 6 It can be observed from the figure that the prepared sample increases gently at the low pressure end, and at this time, N2 molecules are adsorbed in a single layer to a multi-layer, so it belongs to type IV. These isotherms show H3 type hysteresis ring, indicating that the microparticles are aggregated to form a slit-shaped micropore. It can be seen from the figure that the surface area of M1, N3 and N4 is greatly increased compared with Cu2O microparticles. The average pore diameter of S2, M1, N3 and N4 is 123.63, 58.97, 22.32, 59.65 nm respectively. The specific surface area of S2, M1, N3 and N4 is 2.34, 4.91, 18.44, 8.31 m 2 / g, wherein N3 has the largest specific surface area, which also indicates that the active site is increased and the photocatalytic activity is enhanced, which is consistent with the above SEM analysis conclusion.

[0083] In order to further test the influence of composite modification and adding method on the band gap of the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material, UV-Vis DRS analysis was performed on the samples before and after modification of the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material, and the analysis results are shown in Figure 7 It can be seen that the absorption boundary of the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material is blue-shifted, which indicates that the band gap is increased, so that the carrier concentration is improved. The problem of low actual photocatalytic efficiency of cuprous oxide is fundamentally solved. The band gap of S2, M1 and N3 is 2.03, 2.05 and 2.07 eV respectively, which is consistent with the above absorption boundary analysis. The band gap of sample N3 is the largest, which is more conducive to the separation of photo-generated electron-hole pairs, and the photocatalytic activity is the strongest, which is also consistent with the above characterization analysis conclusion.

[0084] In order to explore the electron transfer kinetics and the recombination of photo-generated electron-hole pairs of the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material after composite modification, the samples were subjected to PL test. The test results are shown in Figure 8 It can be observed that the shape and trend of the photoluminescence spectrum of S2 are basically the same, but there is a slight blue shift, and the fluorescence intensity is significantly reduced. The lower the fluorescence intensity, the higher the carrier concentration of the sample, and the better the photoelectric performance. The PL peak of sample N3 is the lowest, which is also much lower than that of the single-element doped modified sample, which indicates that the composite modified sample N3 has the best photocatalytic performance. The slight blue shift of the PL peak is consistent with the above UV-Vis DRS analysis conclusion, which further confirms that the band gap of N3 is increased, the carrier concentration is high, and the photoelectric performance is excellent.

[0085] In order to further understand the electrochemical performance of the samples, they were subjected to alternating current impedance and photocurrent test, and the results are shown in Figure 9 As shown in the figure, the photo-generated current density of M1 and N3 is significantly higher than that of S2, which indicates that composite modification can improve the photocatalytic performance of the sample. The current intensity of the sample rises rapidly when the light is on, and decreases when the light is off, but it can be found that the photo-generated current of the microparticles slightly decreases with the passage of time under the alternating operation of light on and light off, which also indicates that a small amount of photo-induced corrosion of the electrons in the composite sample occurs under the induction of light, and there is a certain stability. The photo-generated current density of sample N3 is the largest, which also indicates that the carrier concentration of sample N3 is the highest. As can be seen from the curves of alternating current impedance of S2, M1 and N3, the curves are roughly semicircular, which also symbolizes the charge transfer, and the diameter of the semicircle is equal to the charge transfer resistance of the sample on the interface. The diameter of the arc of N3 is the smallest, representing that it has the smallest alternating current impedance value, and its charge is easier to transfer, and its photo-generated electron-hole separation effect is the best, and its photoelectric performance is the best. The above conclusion is the same as the characterization results of the photocurrent.

[0086] Referring to Figure 10From the Mott-Schottky curves of S2, N3 and M1, it can be seen that the slope of the measured S2 is positive, which is the electron-conducting n-type cuprous oxide particles. After adding the p-type Pr-Cu2O particles with a negative Mott-Schottky curve slope, the slopes of the curves of samples N3 and N4 are positive in the first half and negative in the second half, which also indicates that the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material is successfully prepared. Through analysis, it is found that the size of the slope in the M-S curve graph is closely related to the concentration of carriers. The smaller the slope, the greater the concentration of carriers, and thus the gap between the Fermi level and the valence band of the prepared sample is further reduced. According to the curve slope of the Mott-Schottky curve, the flat band potential and carrier concentration of each sample are calculated, and it is found through comparison that the carrier concentration of the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material is greatly improved compared with S2, which also indicates that the composite modification can further improve the photocatalytic performance of the sample.

[0087] In order to quantitatively test the photocatalytic performance of M1 and N3, under visible light irradiation, moxifloxacin and norfloxacin were used as target degradation substances to explore their photocatalytic efficiency, cycle stability efficiency and photocatalytic degradation mechanism. See Figure 11 From the figure, it can be observed that the ultraviolet absorption spectrum of moxifloxacin changes obviously, and the intensity of the characteristic absorption peak gradually decreases with the increase of light irradiation time. Among them, the degradation of moxifloxacin solution by M1 and N3 is greatly improved. This indicates that M1 and N3 can better photocatalytically degrade 20 mg / L moxifloxacin solution than S2 and pure Cu2O samples. The degradation rates of samples S2, M1 and N3 on moxifloxacin are 78.8%, 87.8% and 90.5% respectively. Among them, the degradation rate of sample N3 on moxifloxacin solution is the highest, which can reach more than 90%, which is 11.7% higher than that of sample S2 after iodine doping modification, and 25.3% higher than that of pure cuprous oxide. It indicates that the composite modification can further broaden the light response range of the sample, which is consistent with the above analysis test results.

[0088] See Figure 12 It can be seen that the catalytic effect of the composite modified sample is greatly improved compared with the single element doped modified sample, among which the degradation rate of sample N3 is the highest and can reach 90.5%. The degradation process of moxifloxacin by S2, N3 and M1 can be described by the pseudo-first-order kinetic model, and the fitting degree R 2 of the samples is 0.9832, 0.9843 and 0.9841 respectively, which also indicates that the data has a good linear relationship, and the degradation rate constants of the samples are 0.0088, 0.0091 and 0.0090 min -1 respectively. Among them, sample N3 has the highest linear fitting degree and degradation rate.

[0089] Referring to Figure 13 From the figure, it can be found that with the increase of illumination time, the characteristic peak of norfloxacin at 270 nm is very obviously reduced, which shows that the sample after composite modification still has good degradation effect on norfloxacin in addition to moxifloxacin, which also indicates that the sample after composite modification has universality on the degradation of antibiotics. The degradation efficiency of samples S2, N3 and M1 on moxifloxacin reaches 86.5%, 92.1% and 88.7% respectively. Among them, the degradation efficiency of sample N3 on norfloxacin solution is the highest, even higher than the degradation rate on moxifloxacin solution, which is improved by 5.6% compared with sample S2 after iodine doping modification, and improved by 20.9% compared with the catalytic effect of pure cuprous oxide, which also shows that the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material enhances the photocatalytic property, which is consistent with the above test conclusion.

[0090] Referring to Figure 14 From the figure, it can be obviously seen that the catalytic effect of the sample after composite modification is greatly improved compared with the single element doping modified sample, among which the degradation rate of sample N3 can reach 90.5%. The degradation process of samples S2, N3 and M1 on moxifloxacin can be described by the pseudo-first-order kinetic model, and the fitting degrees R 2 of the samples are 0.9981, 0.9947 and 0.9903 respectively, which shows that the data has very good linear relationship, and the degradation rate constants of the samples are 0.0094 min -1 , 0.0124 min -1 and 0.0107 min -1 respectively. Among them, the degradation rate of sample N3 is the largest.

[0091] In order to further explore the stability of the sample after composite modification, 20 mg / L norfloxacin solution was used as the target degradation liquid, and the degradation efficiency of sample N3 in 5 cycles was studied. Referring to Figure 15 , it can be found from the image that the cycle experiment does not change the peak position of the sample diffraction peak, which is still Cu2O crystal, and the diffraction peak at (111) crystal face is slightly reduced, which shows that the sample still has high catalytic degradation performance after five cycles. From the degradation efficiency graph of N3 sample in 5 cycles, it can be obviously seen that the increase of cycle times has little effect on the degradation rate of the sample on norfloxacin, and the photocatalytic efficiency of the sample after 5 cycles is 86.2%, which is only reduced by 5.9%, which also shows that the p-n Cu2O homojunction composite photocatalytic nitrogen fixation material has good stability and can be used repeatedly.

[0092] To further explore the contribution of different active species to the photocatalytic degradation rate of norfloxacin, different active species quenchers were added in the photocatalytic experiment to determine the contribution of different active species to the degradation of norfloxacin. During the degradation process, three kinds of capture agents, methanol (MT), isopropyl alcohol (IPA) and p-benzoquinone (BQ) were added as scavengers of holes (h + ), hydroxyl radicals (·OH) and superoxide radicals (·O2-), respectively. See Figure 16 It can be seen that when MT, IPA and BQ are added, the degradation efficiency of sample N3 on norfloxacin decreases from 92.1% to 51.4%, 31.2% and 33.5%, which indicates that h + , ·OH and ·O 2- act synergistically during the degradation process, and ·OH and ·O 2- are the main active species in the photocatalytic degradation process.

[0093] To further explore the effect of composite modification on the band structure of the sample, VB XPS test was performed on sample N3, and the results are shown in Figure 17 . After fitting, it is determined that the valence band (VB) of sample N3 is 1.78 eV. Combined with the fitting of the band gap, the conduction band (CB) of sample N3 is calculated to be -0.29 eV. To explore the reliability of the above experimental results, the conduction band position and valence band position of the semiconductor material are calculated, and the theoretical VB and CB positions of Cu2O particles are obtained as 1.85 eV and -0.17 eV, respectively. The VB and CB positions of R2 particles are 1.81 eV and -0.25 eV, respectively. By comparison, it is found that the difference between the theoretical calculation value and the measured value is small, which further confirms the reliability of the experimental results.

[0094] See Figure 18 , combined with the above capture agent experiment, the photocatalytic degradation mechanism is inferred. Under light irradiation, electrons in the valence band jump to the conduction band under photoexcitation, high-activity electrons are generated in the conduction band, and positive holes are generated in the valence band. The electron has strong reducing property, and the hole has strong oxidizing property, which induces the reaction of organic matter. Among them, the p-n homojunction is formed, and the electron transfer process first migrates from the n-type Cu2O semiconductor material to the surface of the p-type semiconductor material. The praseodymium ion can act as a photogenerated electron-hole trap to capture photogenerated electrons, thereby improving the separation efficiency of the photogenerated electron-hole pair. At the same time, the holes generated by the electron transition in the p-type semiconductor are firmly attracted by the iodine ions doped in the n-type semiconductor material, thereby increasing the concentration of carriers and further improving the photocatalytic performance of the sample.

[0095] The application provides a Cu2O p-n homojunction composite photocatalytic nitrogen fixation material, which is prepared by the above preparation method, and a built-in electric field is formed at the interface of the p-type and n-type Cu2O in the Cu2O p-n homojunction composite photocatalytic nitrogen fixation material, photoexcitation generated electrons migrate from the conduction band of the n-type Cu2O to the valence band of the p-type Cu2O, and holes migrate in the opposite direction, and the directional migration effectively inhibits the electron-hole recombination, prolongs the carrier lifetime, meanwhile, the composite of the p-type Pr-Cu2O and the n-type I-Cu2O may form a synergistic light absorption effect, enhances the utilization efficiency of the material on visible light, realizes the comprehensive optimization of the N2 reduction thermodynamics, carrier separation kinetics, surface reaction activity and material stability, and provides a key band engineering strategy for the design of high-efficiency and stable photocatalytic nitrogen fixation materials.

[0096] The application of the above Cu2O p-n homojunction composite photocatalytic nitrogen fixation material in photocatalytic nitrogen fixation, the Cu2O p-n homojunction composite photocatalytic nitrogen fixation material has a wider light absorption range, a lower carrier recombination probability, a good stability and a good recycling, has a better light utilization, a better oxidation and reduction capacity and a lower energy barrier in photocatalytic nitrogen fixation, and provides a feasible scheme for replacing the industrial Haber-Bosch method (high temperature and high pressure, high energy consumption), and promotes the development of high-efficiency and stable photocatalytic nitrogen fixation.

[0097] The above only describes the preferred embodiments of the application, and does not use to limit the technical solutions of the application in any way, and those skilled in the art should understand that the technical solutions can be simply modified and replaced without departing from the spirit and principles of the application, and the modifications and replacements also belong to the protection scope covered by the claims.

Claims

1. A method for preparing a Cu2O pn homojunction composite photocatalytic nitrogen fixation material, characterized in that: include: Pr(NO3)3 and n-type I-Cu2O are added to the Cu2O reaction solution, or KI and p-type Pr-Cu2O are added to the Cu2O reaction solution, and a hydrothermal reaction is carried out to obtain a Cu2O pn homojunction composite photocatalytic nitrogen fixation material; The n-type I-Cu2O is obtained by adding KI to a Cu2O reaction solution and performing a hydrothermal reaction, and the p-type Pr-Cu2O is obtained by adding Pr(NO3)3 to a Cu2O reaction solution and performing a hydrothermal reaction.

2. The method for preparing the Cu2O pn homojunction composite photocatalytic nitrogen fixation material according to claim 1, characterized in that: The method for obtaining the Cu2O reaction solution is: The copper acetate solution, the NaOH solution and the glucose solution are mixed uniformly to obtain a first mixed solution; Polyvinyl pyrrolidone is added to the first mixed solution to obtain a Cu2O reaction solution.

3. The method for preparing the Cu2O pn homojunction composite photocatalytic nitrogen fixation material according to claim 2, characterized in that: The concentration of the copper acetate solution is 0.15 to 0.25 g / mL; the concentration of the NaOH solution is 0.7 to 0.9 mol / L; the concentration of the glucose solution is 1 to 1.5 mol / L; the volume ratio of the copper acetate solution, the NaOH solution, and the glucose solution is 3:1:1; and the concentration of polyvinyl pyrrolidone after adding polyvinyl pyrrolidone to the first mixed solution is 0.01 to 0.04 g / mL.

4. The method for preparing the Cu2O pn homojunction composite photocatalytic nitrogen fixation material according to claim 1, wherein: The n-type I-Cu2O is prepared by adding KI to a Cu2O reaction solution and performing a hydrothermal reaction, comprising: KI is added to the Cu2O reaction solution, and the reaction is carried out at 80°C to 100°C for 10 to 18 hours to obtain n-type I-Cu2O; wherein, after the KI is added to the Cu2O reaction solution, the concentration of the KI is 0.0002 to 0.0004 g / mL.

5. The method for preparing the Cu2O pn homojunction composite photocatalytic nitrogen fixation material according to claim 1, characterized in that: The p-type Pr-Cu2O is prepared by adding Pr(NO3)3 to a Cu2O reaction solution and performing a hydrothermal reaction, comprising: Pr(NO3)3 is added to the Cu2O reaction solution, and the reaction is carried out at 80°C to 100°C for 10 to 18 hours to obtain p-type Pr-Cu2O; wherein, after adding Pr(NO3)3 to the Cu2O reaction solution, the concentration of Pr(NO3)3 is 0.0002 to 0.0006 g / mL.

6. The method for preparing the Cu2O pn homojunction composite photocatalytic nitrogen fixation material according to claim 1, wherein: include: Pr(NO3)3 and n-type I-Cu2O are added to the Cu2O reaction solution and subjected to a hydrothermal reaction to obtain a Cu2O pn homojunction composite photocatalytic nitrogen fixation material; Among them, after adding Pr(NO3)3 and n-type I-Cu2O to the Cu2O reaction solution, the concentration of Pr(NO3)3 is 0.0002~0.0006g / mL, and the concentration of n-type I-Cu2O is 0.0002~0.0008 g / mL.

7. The method for preparing the Cu2O pn homojunction composite photocatalytic nitrogen fixation material according to claim 1, characterized in that: include: KI and p-type Pr-Cu2O are added to the Cu2O reaction solution and subjected to a hydrothermal reaction to obtain a Cu2O pn homojunction composite photocatalytic nitrogen fixation material; Wherein, after adding KI and p-type Pr-Cu2O to the Cu2O reaction solution, the concentration of KI is 0.0002-0.0004 g / mL, and the concentration of p-type Pr-Cu2O is 0.0002-0.0008 g / mL.

8. The method for preparing the Cu2O pn homojunction composite photocatalytic nitrogen fixation material according to claim 1, wherein: The method of adding Pr(NO3)3 and n-type I-Cu2O to the Cu2O reaction solution or adding KI and p-type Pr-Cu2O to the Cu2O reaction solution and performing a hydrothermal reaction to obtain the Cu2O pn homojunction composite photocatalytic nitrogen fixation material is as follows: Pr(NO3)3 and n-type I-Cu2O are added to the Cu2O reaction solution, or KI and p-type Pr-Cu2O are added to the Cu2O reaction solution, and a hydrothermal reaction is carried out at 80°C to 100°C for 10 to 18 hours to obtain a Cu2O pn homojunction composite photocatalytic nitrogen fixation material.

9. A Cu2O pn homojunction composite photocatalytic nitrogen fixation material, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the Cu2O pn homojunction composite photocatalytic nitrogen fixation material according to claim 9 in photocatalytic nitrogen fixation.

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