Heterojunction material for negative ion release head and preparation method and application thereof

Abstract

The invention belongs to the technical field of functional materials, and discloses a heterojunction material for a negative ion release head as well as a preparation method and application of the heterojunction material. The heterojunction material comprises zinc ferrite, graphene and tungsten oxide, wherein the zinc ferrite and the tungsten oxide are jointly anchored on the surface and between layers of the graphene through chemical bonding. According to the heterojunction material, the band gap splitting characteristic of zinc ferrite and tungsten oxide is utilized, charge separation is effectively promoted, excessive consumption of a single component is restrained, high-concentration, controllable and stable negative ion release is achieved under external electric field or thermal excitation, and meanwhile the service life of the material is remarkably prolonged; in addition, the preparation method of the material combines coprecipitation with a hydrothermal / solvothermal method, the process is simple, and large-scale production is easy. The invention further provides a negative ion release head made of the material, and the negative ion release head can be widely applied to the fields of air purifiers, air conditioners, fresh air systems, wearable equipment and the like and has the advantages of being environmentally friendly, high in efficiency and long in service life.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, and specifically relates to a heterojunction material for a negative ion emission head, its preparation method, and its application. Background Technology

[0002] Negative ions, especially negative oxygen ions, are widely recognized for their positive effects on air purification and improving human health. Traditional negative ion release technologies mainly rely on corona discharge, radioactive element irradiation, and natural mineral materials such as tourmaline.

[0003] Corona discharge can generate high concentrations of negative ions, but it is usually accompanied by the formation of byproducts such as ozone and nitrogen oxides, which are harmful to the human body. While radioactive element methods are efficient and stable, they pose potential safety risks and raise concerns about public acceptance. Negative ion materials based on natural minerals generally have low negative ion release efficiency, and their release concentration is greatly affected by the environment, resulting in limited stability and lifespan.

[0004] In recent years, some semiconductor materials have been used for negative ion release. For example, invention patent CN120350561A discloses a negative ion material obtained by combining titanium dioxide with other minerals. However, such materials are mostly single semiconductor composites, which suffer from problems such as high electron-hole recombination rates, stringent triggering conditions for negative ion release (usually requiring ultraviolet light excitation), and uncontrollable release efficiency. With long-term use, the material may experience structural failure due to over-excitation, leading to a sharp drop in negative ion release concentration and a short lifespan.

[0005] Therefore, there is an urgent need in this field to develop a novel functional material that can efficiently release negative ions under mild conditions (such as weak electric fields or thermal energy) without the presence of harmful byproducts, with high negative ion release efficiency, strong controllability, long service life, and no harmful byproducts. Summary of the Invention

[0006] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention provides a heterojunction material for a negative ion releasing head, which can stably release high concentrations of negative ions under an external electric field or thermal excitation, and the release process is controllable and has a long service life.

[0007] The present invention also provides a method for preparing the above-mentioned heterojunction material, which is simple in process, controllable in conditions, and easy to realize industrial production.

[0008] The present invention also provides a negative ion releasing head, which has a simple structure and excellent negative ion releasing efficiency.

[0009] This invention also provides applications of the above-mentioned heterojunction material and negative ion emission head, which can be widely used in various air treatment and health devices.

[0010] In a first aspect, the present invention provides a heterojunction material comprising zinc ferrite, graphene, and tungsten oxide, wherein the zinc ferrite and tungsten oxide are chemically bonded together and anchored on the surface and between layers of the graphene.

[0011] Specifically, the heterojunction material of the present invention has the following characteristics: Structural features: Zinc ferrite and tungsten oxide, in the form of nanoparticles, are anchored together on the surface and between layers of graphene through strong chemical bonds (such as Fe-OC and WOC bonds), forming a unique three-dimensional heterojunction network structure. As a conductive substrate with a high specific surface area, graphene not only provides a huge load space but also constitutes a highly efficient electron transport channel.

[0012] Bandgap engineering characteristics: Zinc ferrite and tungsten oxide possess bandgap splitting characteristics, which to some extent inhibit the migration of charge carriers at the heterojunction interface, generating mutually restraining built-in electric fields. This "bandgap splitting characteristic" effectively promotes the separation of photogenerated or electrogenerated electron-hole pairs and inhibits material pulverization or failure caused by excessive charge accumulation in a single component. From a macroscopic perspective, this mechanism enhances the controllability of negative ion release efficiency and significantly extends the service life of the negative ion release head.

[0013] Performance characteristics: The heterojunction material can continuously and stably release concentrations greater than 50 × 10⁻⁵ under external low-intensity electric fields (e.g., 1-5 V / μm) or medium-low temperature thermal excitation (e.g., 40-80℃). 4 pcs / cm 3 Negative ions.

[0014] Preferably, the surface and interlayer of the graphene are further loaded with rare earth oxides.

[0015] Specifically, the present invention can further adjust the band structure of the material by introducing rare earth elements and provide more oxygen vacancies as active sites for the generation of negative ions.

[0016] Preferably, the heterojunction material comprises, by mass percentage: 5%-20% graphene, 30%-60% zinc ferrite, 30%-60% tungsten oxide, and 0.5%-5% rare earth oxides.

[0017] Preferably, the rare earth oxide includes at least one of cerium oxide (CeO2), lanthanum oxide (La2O3), and yttrium oxide (Y2O3).

[0018] Preferably, the zinc ferrite has a particle size of 10-200 nm.

[0019] Preferably, the tungsten oxide has a particle size of 20-200 nm.

[0020] Specifically, the present invention controls the particle size of zinc ferrite and tungsten oxide within a suitable range, so that the nanoparticles have high surface activity and a suitable quantum size effect.

[0021] Preferably, the specific surface area of ​​the graphene is 300-800 m². 2 / g. The graphene is porous graphene obtained by reducing graphene oxide. This porous structure greatly increases the specific surface area of ​​the material, providing more active sites for the construction of heterojunctions and the release of negative ions.

[0022] Preferably, the raw materials for preparing the heterojunction material include graphene oxide, iron source, zinc source, tungsten source, rare earth salt, precipitant and water.

[0023] Preferably, the iron source includes ferric nitrate and / or ferric chloride.

[0024] Preferably, the zinc source includes zinc nitrate and / or zinc acetate.

[0025] Preferably, the tungsten source includes sodium tungstate and / or ammonium metatungstate.

[0026] Preferably, the rare earth salt includes rare earth nitrate and / or rare earth chloride.

[0027] Preferably, the precipitant includes at least one of ammonia, urea, and sodium hydroxide solution.

[0028] In a second aspect, the present invention provides a method for preparing the heterojunction material described in the first aspect, comprising the following steps: Graphene oxide was dispersed in water to obtain a graphene oxide dispersion. Iron source, zinc source, tungsten source and graphene oxide dispersion are mixed and stirred to obtain mixed dispersion; A precipitant is added to the mixed dispersion, and the pH value is controlled at 8-10 to carry out a co-precipitation reaction to obtain a mixed slurry. The mixed slurry is transferred to a hydrothermal reactor for hydrothermal / solvothermal reaction. After the hydrothermal / solvothermal reaction is completed, the product is cooled, filtered, washed, and dried. The dried product is calcined under an inert gas or nitrogen-hydrogen mixed atmosphere to obtain the heterojunction material.

[0029] Preferably, the method for preparing the heterojunction material includes the following steps: a. Preparation of graphene oxide dispersion: Graphene oxide is dispersed in deionized water and ultrasonically treated for 1-3 hours to obtain a graphene oxide dispersion with uniform concentration. b. Precursor mixing: Add the iron source, zinc source and tungsten source to the graphene oxide dispersion in step a according to the designed stoichiometric ratio, and stir continuously at 40-60℃ for 2-4 hours to make it uniformly mixed to obtain a mixed dispersion. c. Coprecipitation and loading: Under continuous stirring, a precipitant is slowly added dropwise to the mixed dispersion from step b, and the pH of the reaction system is controlled between 8 and 10 to carry out a coprecipitation reaction and obtain a mixed slurry; this process allows the hydroxide or basic salt precursor of metal ions to be uniformly deposited on the surface and between layers of graphene oxide. d. Hydrothermal / solvothermal reaction: The mixed slurry obtained in step c is transferred to a polytetrafluoroethylene-lined hydrothermal reactor and reacted at 120-200℃ for 6-24 hours. During this process, zinc ferrite and tungsten oxide nanocrystals are generated in situ from the precursor. At the same time, the hydrothermal environment will partially reduce the graphene oxide, restore its conductivity, and strengthen the chemical bonds between the components. e. Post-processing: After the reaction in step d is completed, the product is naturally cooled to room temperature, filtered, and washed multiple times with deionized water and ethanol to remove impurities. Then, it is vacuum dried at 60-100℃ for 6-12 hours. f. Calcination: Under the protection of an inert gas (such as argon) or a nitrogen-hydrogen mixed atmosphere, the dried product is calcined at 300-500°C for 2-5 hours to obtain the heterojunction material. This step aims to further crystallize the semiconductor nanoparticles, completely reduce graphene oxide, and form a stable heterojunction structure.

[0030] Preferably, rare earth salts are added and mixed in step b.

[0031] In a third aspect, the present invention provides a negative ion releasing head, comprising a substrate and a functional material layer attached to the substrate, wherein the functional material layer contains the heterojunction material described in the first aspect of the present invention.

[0032] Preferably, the functional material layer further contains a conductive agent and a binder.

[0033] Preferably, the conductive agent includes at least one of acetylene black, Ketjen black, and carbon nanotubes.

[0034] Preferably, the adhesive comprises at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and sodium silicate.

[0035] In a fourth aspect, the invention provides the application of the heterojunction material described in the first aspect or the negative ion releasing head described in the third aspect in air purifiers, fresh air systems, air conditioners, negative ion generators, or wearable health devices.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows: High negative ion release efficiency: The heterojunction material provided by this invention possesses a unique three-dimensional heterojunction structure and a highly conductive graphene network, which greatly promotes charge separation and transport, enabling the material to release >50×10⁻⁶ negative ions under a mild electric field or thermal excitation. 4 pcs / cm 3 High concentration of negative ions.

[0037] Controllability and long lifespan: This invention utilizes the heterojunction formed by the band gap splitting characteristics of zinc ferrite and tungsten oxide to effectively suppress excessive charge accumulation and rapid loss of single components, achieving "intelligent" control of the negative ion release process, avoiding premature material failure, and significantly extending service life.

[0038] Environmentally friendly and safe: The heterojunction material provided by this invention does not produce harmful byproducts such as ozone during the entire negative ion release process, making it safe and reliable.

[0039] The preparation process is mature: The coprecipitation combined with hydrothermal / solvothermal method adopted in this invention is simple, mild, and has low equipment requirements. The components are mixed at the molecular / atomic level, and the heterojunction structure is uniform and stable, which is very suitable for large-scale production.

[0040] Wide range of applications: The heterojunction material provided by this invention can be easily made into a coating and applied to various forms of negative ion emission heads to meet diverse needs from large-scale air purification equipment to personal wearable devices. Detailed Implementation

[0041] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments can be obtained from conventional means or by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0042] Example 1 A heterojunction material includes zinc ferrite, graphene, tungsten oxide and cerium oxide, wherein zinc ferrite and tungsten oxide are chemically bonded together and anchored on the surface and between layers of graphene, and cerium oxide is loaded on the surface and between layers of graphene.

[0043] The preparation method of the above heterojunction material includes the following steps: a. Preparation of graphene oxide dispersion: 100 mg of graphene oxide was dispersed in 60 mL of deionized water and ultrasonically treated for 2 hours to obtain a uniformly dispersed graphene oxide dispersion. b. Precursor mixing: Ferric nitrate (Fe(NO3)3·9H2O, corresponding to 0.02 mol of zinc ferrite), zinc nitrate (Zn(NO3)2·6H2O, corresponding to 0.02 mol of zinc ferrite), sodium tungstate (Na2WO4·2H2O, corresponding to 0.03 mol of tungsten oxide) and cerium nitrate (Ce(NO3)3·6H2O, cerium oxide accounts for 2% of the total mass of the heterojunction material) are added sequentially to the graphene oxide dispersion in step a. The mixture is stirred continuously in a 50°C water bath for 3 hours to ensure uniform mixing and allow the metal ions to be fully adsorbed on the graphene oxide to obtain a mixed dispersion. c. Co-precipitation and loading: Under continuous stirring, 1 mol / L ammonia solution was slowly added dropwise to the mixed dispersion from step b to adjust the pH to 9.5. A large amount of precipitate was observed to form. Stirring was continued for 2 hours to obtain the mixed slurry. d. Hydrothermal reaction: The mixed slurry obtained in step c is transferred to a polytetrafluoroethylene-lined hydrothermal reactor and reacted at 200°C for 6 hours; e. Post-processing: After the reaction in step d is completed, the product is naturally cooled to room temperature, filtered, and washed multiple times with deionized water and ethanol to remove impurities. Then, it is vacuum dried at 80°C for 12 hours. f. Calcination: The precursor powder dried in step e is placed in a tube furnace and calcined at 400°C for 3 hours under an argon atmosphere. After natural cooling, the heterojunction material is obtained. The calculated mass percentages of the components in the heterojunction material are approximately: 10% graphene, 45% zinc ferrite, 43% tungsten oxide, and 2% cerium oxide.

[0044] Example 2 A heterojunction material includes zinc ferrite, graphene, tungsten oxide, and lanthanum oxide, wherein zinc ferrite and tungsten oxide are chemically bonded together and anchored on the surface and between layers of graphene, and lanthanum oxide is loaded on the surface and between layers of graphene.

[0045] The preparation method of the above heterojunction material includes the following steps: a. Preparation of graphene oxide dispersion: Graphene oxide was dispersed in 60 mL of deionized water and ultrasonically treated for 2 hours to obtain a uniformly dispersed graphene oxide dispersion. b. Precursor mixing: Add ferric nitrate, zinc nitrate, sodium tungstate and cerium nitrate sequentially to the graphene oxide dispersion from step a, and stir continuously in a 50°C water bath for 3 hours to mix evenly, so that the metal ions are fully adsorbed on the graphene oxide to obtain a mixed dispersion. c. Co-precipitation and loading: Under continuous stirring, 1 mol / L ammonia solution was slowly added dropwise to the mixed dispersion from step b to adjust the pH to 9.5. A large amount of precipitate was observed to form. Stirring was continued for 2 hours to obtain the mixed slurry. d. Hydrothermal reaction: The mixed slurry obtained in step c is transferred to a polytetrafluoroethylene-lined hydrothermal reactor and reacted at 160°C for 18 hours; e. Post-processing: After the reaction in step d is completed, the product is naturally cooled to room temperature, filtered, and washed multiple times with deionized water and ethanol to remove impurities. Then, it is vacuum dried at 80°C for 12 hours. f. Calcination: The precursor powder dried in step e is placed in a tube furnace and calcined at 350°C for 4 hours under an argon atmosphere. After natural cooling, a heterojunction material is obtained. The mass percentage of its components is approximately: 20% graphene, 39.5% zinc ferrite, 40% tungsten oxide, and 0.5% lanthanum oxide.

[0046] Example 3 A heterojunction material includes zinc ferrite, graphene, tungsten oxide and yttrium oxide, wherein zinc ferrite and tungsten oxide are chemically bonded together and anchored on the surface and between layers of graphene, and yttrium oxide is loaded on the surface and between layers of graphene.

[0047] The preparation method of the above heterojunction material includes the following steps: a. Preparation of graphene oxide dispersion: Graphene oxide was dispersed in 60 mL of deionized water and ultrasonically treated for 2 hours to obtain a uniformly dispersed graphene oxide dispersion. b. Precursor mixing: Add ferric nitrate, zinc nitrate, sodium tungstate and cerium nitrate sequentially to the graphene oxide dispersion from step a, and stir continuously in a 50°C water bath for 3 hours to mix evenly, so that the metal ions are fully adsorbed on the graphene oxide to obtain a mixed dispersion. c. Co-precipitation and loading: Under continuous stirring, 1 mol / L ammonia solution was slowly added dropwise to the mixed dispersion from step b to adjust the pH to 9.5. A large amount of precipitate was observed to form. Stirring was continued for 2 hours to obtain the mixed slurry. d. Hydrothermal reaction: The mixed slurry obtained in step c is transferred to a polytetrafluoroethylene-lined hydrothermal reactor and reacted at 120°C for 24 hours; e. Post-processing: After the reaction in step d is completed, the product is naturally cooled to room temperature, filtered, and washed multiple times with deionized water and ethanol to remove impurities. Then, it is vacuum dried at 80°C for 12 hours. f. Calcination: The precursor powder dried in step e is placed in a tube furnace and calcined at 500°C for 2 hours under an argon atmosphere. After natural cooling, a heterojunction material is obtained. The mass percentage of its components is approximately: 5% graphene, 30% zinc ferrite, 60% tungsten oxide, and 5% yttrium oxide.

[0048] Example 4 A heterojunction material comprising zinc ferrite, graphene, and tungsten oxide, wherein zinc ferrite and tungsten oxide are chemically bonded together and anchored on the surface and between layers of graphene.

[0049] The preparation method of the above heterojunction material includes the following steps: a. Preparation of graphene oxide dispersion: 100 mg of graphene oxide was dispersed in 60 mL of deionized water and ultrasonically treated for 2 hours to obtain a uniformly dispersed graphene oxide dispersion. b. Precursor mixing: Ferric nitrate (Fe(NO3)3·9H2O, corresponding to 0.04 mol of zinc ferrate), zinc nitrate (Zn(NO3)2·6H2O, corresponding to 0.04 mol of zinc ferrate), and sodium tungstate (Na2WO4·2H2O, corresponding to 0.02 mol of tungsten oxide) were added sequentially to the graphene oxide dispersion from step a. The mixture was stirred continuously in a 50°C water bath for 3 hours until homogeneous, so that the metal ions were fully adsorbed onto the graphene oxide to obtain a mixed dispersion. c. Co-precipitation and loading: Under continuous stirring, 1 mol / L ammonia solution was slowly added dropwise to the mixed dispersion from step b to adjust the pH to 9.5. A large amount of precipitate was observed to form. Stirring was continued for 2 hours to obtain the mixed slurry. d. Hydrothermal reaction: The mixed slurry obtained in step c is transferred to a polytetrafluoroethylene-lined hydrothermal reactor and reacted at 200°C for 6 hours; e. Post-processing: After the reaction in step d is completed, the product is naturally cooled to room temperature, filtered, and washed multiple times with deionized water and ethanol to remove impurities. Then, it is vacuum dried at 80°C for 12 hours. f. Calcination: The precursor powder dried in step e is placed in a tube furnace and calcined at 400°C for 3 hours under an argon atmosphere. After natural cooling, the heterojunction material is obtained. The calculated mass percentages of the components in the heterojunction material are approximately: 10% graphene, 60% zinc ferrite, and 30% tungsten oxide.

[0050] Comparative Example 1 (Preparation of pure-phase zinc ferrite nanoparticles) The preparation method of zinc ferrite nanoparticles includes the following steps: According to the raw material addition amount in Example 1, ferric nitrate and zinc nitrate were added to deionized water and stirred continuously in a 50°C water bath for 3 hours. Then, 1 mol / L ammonia solution was slowly added dropwise to adjust the pH value to 9.5. A large amount of precipitate was observed to form. Stirring was continued for 2 hours to obtain a mixed slurry. The above-mentioned mixed slurry was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 200°C for 6 hours. After the reaction was completed, the product was naturally cooled to room temperature, filtered, and washed multiple times with deionized water and ethanol to remove impurities. Then it was vacuum dried at 80°C for 12 hours. The dried powder was placed in a tube furnace and calcined at 400°C for 3 hours under an argon atmosphere. After natural cooling, zinc ferrite nanoparticles were obtained.

[0051] Comparative Example 2 (Preparation of pure-phase tungsten oxide nanoparticles) The preparation method of tungsten oxide nanoparticles includes the following steps: According to the raw material addition amount in Example 1, sodium tungstate was added to deionized water and stirred continuously in a 50°C water bath for 3 hours. Then, 1 mol / L ammonia solution was slowly added dropwise to adjust the pH value to 9.5. A large amount of precipitate was observed to form. Stirring was continued for 2 hours to obtain a mixed slurry. The above-mentioned mixed slurry was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 200°C for 6 hours. After the reaction was completed, the product was naturally cooled to room temperature, filtered, and washed multiple times with deionized water and ethanol to remove impurities. Then it was vacuum dried at 80°C for 12 hours. The dried powder was placed in a tube furnace and calcined at 400°C for 3 hours under an argon atmosphere. After natural cooling, tungsten oxide nanoparticles were obtained.

[0052] Comparative Example 3 (Preparation of Graphene) The preparation method of graphene includes the following steps: According to the amount of raw materials added in Example 1, graphene oxide was dispersed in deionized water and ultrasonically treated for 2 hours to obtain graphene oxide dispersion. The above graphene oxide dispersion was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 200°C for 6 hours. After the reaction was completed, the product was naturally cooled to room temperature, filtered, and washed multiple times with deionized water and ethanol to remove impurities. Then it was vacuum dried at 80°C for 12 hours. The dried powder was placed in a tube furnace and calcined at 400°C for 3 hours under an argon atmosphere. After natural cooling, graphene was obtained.

[0053] Comparative Example 4 (Preparation of pure-phase zinc ferrite / tungsten oxide heterostructure nanoparticles) A method for preparing zinc ferrite / tungsten oxide heterojunction nanoparticles includes the following steps: According to the raw material addition amount in Example 1, ferric nitrate, zinc nitrate and sodium tungstate were added to deionized water and stirred continuously in a 50°C water bath for 3 hours. Then, 1 mol / L ammonia solution was slowly added dropwise to adjust the pH value to 9.5. A large amount of precipitate was observed to form. Stirring was continued for 2 hours to obtain a mixed slurry. The above-mentioned mixed slurry was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 200°C for 6 hours. After the reaction was completed, the product was naturally cooled to room temperature, filtered, and washed multiple times with deionized water and ethanol to remove impurities. Then it was vacuum dried at 80°C for 12 hours. The dried powder was placed in a tube furnace and calcined at 400°C for 3 hours under an argon atmosphere. After natural cooling, zinc ferrite / tungsten oxide heterojunction nanoparticles were obtained.

[0054] Comparative Example 5 (Preparation of pure-phase graphene / tungsten oxide heterostructure nanoparticles) A method for preparing graphene / tungsten oxide heterostructure nanoparticles includes the following steps: According to the amount of raw materials added in Example 1, graphene oxide was dispersed in deionized water and ultrasonically treated for 2 hours to obtain graphene oxide dispersion. Sodium tungstate was added to the above graphene oxide dispersion, and the mixture was stirred continuously in a 50°C water bath for 3 hours. Then, 1 mol / L ammonia solution was slowly added dropwise to adjust the pH value to 9.5. A large amount of precipitate was observed to form. The mixture was stirred for another 2 hours to obtain a mixed slurry. The above-mentioned mixed slurry was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 200°C for 6 hours. After the reaction was completed, the product was naturally cooled to room temperature, filtered, and washed multiple times with deionized water and ethanol to remove impurities. Then it was vacuum dried at 80°C for 12 hours. The dried powder was placed in a tube furnace and calcined at 400°C for 3 hours under an argon atmosphere. After natural cooling, graphene / tungsten oxide heterostructure nanoparticles were obtained.

[0055] Comparative Example 6 (Preparation of pure-phase graphene / zinc ferrite heterostructure nanoparticles) A method for preparing graphene / zinc ferrite heterostructure nanoparticles includes the following steps: According to the amount of raw materials added in Example 1, graphene oxide was dispersed in deionized water and ultrasonically treated for 2 hours to obtain graphene oxide dispersion. Sodium tungstate was added to the above graphene oxide dispersion, and the mixture was stirred continuously in a 50°C water bath for 3 hours. Then, 1 mol / L ammonia solution was slowly added dropwise to adjust the pH value to 9.5. A large amount of precipitate was observed to form. The mixture was stirred for another 2 hours to obtain a mixed slurry. The above-mentioned mixed slurry was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 200°C for 6 hours. After the reaction was completed, the product was naturally cooled to room temperature, filtered, and washed multiple times with deionized water and ethanol to remove impurities. Then it was vacuum dried at 80°C for 12 hours. The dried powder was placed in a tube furnace and calcined at 400°C for 3 hours under an argon atmosphere. After natural cooling, graphene / zinc ferrite heterostructure nanoparticles were obtained.

[0056] Performance testing and effect verification The materials obtained in Examples 1-4 and Comparative Examples 1-6 were mixed with 5% conductive carbon black and 5% polyvinylidene fluoride (PVDF) binder, and N-methylpyrrolidone (NMP) was used as a solvent to form a slurry. The slurry was coated onto an aluminum mesh substrate (as a negative ion release head) and dried at 80°C to form the final product.

[0057] The prepared negative ion releasing head was placed at 1m 3 In a sealed test chamber, a DC electric field of 3V / μm was applied, and the negative ion concentration was measured at a distance of 30cm from the release head using a negative ion concentration meter (COM-3200PRO). The test results are shown in Table 1 below.

[0058] Table 1. Results of negative ion concentration test

[0059] Note: The lifespan retention rate in Table 1 is the ratio of the negative ion concentration after 1000 hours of aging to the initial negative ion concentration.

[0060] As shown in Table 1, the heterojunction materials prepared in Examples 1-4 of this invention exhibit significantly higher negative ion release concentrations under the same excitation conditions compared to Comparative Examples 1-6. More importantly, after 1000 hours of continuous operation, the negative ion release concentration retention rate (lifetime retention rate) of the material of this invention is over 90%, while that of Comparative Examples 1-6 decreases by more than 30%. This fully demonstrates the significant advancements of the heterojunction material of this invention in terms of high release efficiency and long service life.

[0061] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A heterojunction material, characterized in that, It includes zinc ferrite, graphene, and tungsten oxide, wherein the zinc ferrite and tungsten oxide are chemically bonded together and anchored on the surface and between layers of the graphene.

2. The heterojunction material according to claim 1, characterized in that, The surface and interlayer of the graphene are also loaded with rare earth oxides.

3. The heterojunction material according to claim 2, characterized in that, The heterojunction material comprises, by mass percentage: 5%-20% graphene, 30%-60% zinc ferrite, 30%-60% tungsten oxide, and 0.5%-5% rare earth oxides.

4. The heterojunction material according to claim 2, characterized in that, The rare earth oxides include at least one of cerium oxide, lanthanum oxide, and yttrium oxide.

5. The heterojunction material according to claim 1, characterized in that, The zinc ferrite has a particle size of 10-200 nm; and / or the tungsten oxide has a particle size of 20-200 nm.

6. The heterojunction material according to claim 1, characterized in that, The specific surface area of ​​the graphene is 300-800 m². 2 / g.

7. The method for preparing the heterojunction material according to any one of claims 1-6, characterized in that, Includes the following steps: Graphene oxide was dispersed in water to obtain a graphene oxide dispersion. Iron source, zinc source, tungsten source and graphene oxide dispersion are mixed and stirred to obtain mixed dispersion; A precipitant is added to the mixed dispersion, and the pH value is controlled at 8-10 to carry out a co-precipitation reaction to obtain a mixed slurry. The mixed slurry is transferred to a hydrothermal reactor for hydrothermal / solvothermal reaction. After the hydrothermal / solvothermal reaction is completed, the product is cooled, filtered, washed, and dried. The dried product is calcined under an inert gas or nitrogen-hydrogen mixed atmosphere to obtain the heterojunction material.

8. The preparation method according to claim 7, characterized in that, The hydrothermal reaction temperature is 120-200℃; and / or the hydrothermal reaction time is 6-24h.

9. A negative ion releasing head, characterized in that, It includes a substrate and a functional material layer attached to the substrate, wherein the functional material layer contains the heterojunction material according to any one of claims 1-6.

10. The application of the heterojunction material according to any one of claims 1-6 or the negative ion releasing head according to claim 9 in air purifiers, fresh air systems, air conditioners, negative ion generators or wearable health devices.

Images