Preparation method of crystalline-amorphous heterojunction photocatalyst

Abstract

This invention discloses a method for preparing crystalline-amorphous heterojunction photocatalysts, belonging to the field of photocatalyst preparation technology, and aims to solve technical problems such as difficulty in controlling the crystalline phase and weak interfacial bonding in existing technologies. This invention employs corresponding amorphous iron oxide introduction mechanisms for zirconium oxide with different crystalline phases to prepare monoclinic zirconium oxide / amorphous iron oxide heterojunctions, tetragonal zirconium oxide / amorphous iron oxide heterojunctions, and cubic zirconium oxide / amorphous iron oxide heterojunctions. The introduction mechanisms include modification mechanisms, competition mechanisms, and auxiliary mechanisms. By finely controlling the amorphous structure of iron oxide and its interfacial bonding with different crystalline zirconium oxides, the controllable construction of crystalline zirconium oxide and amorphous iron oxide heterostructures is achieved.

Description

Technical Field

[0001] This invention relates to the field of photocatalyst preparation technology, and specifically to a method for preparing a crystalline-amorphous heterojunction photocatalyst. Background Technology

[0002] Photocatalysis technology has attracted widespread attention due to its enormous potential in environmental pollution control and new energy development. Semiconductor photocatalysts are central to this field. Zirconia (ZrO2) is widely used as a photocatalytic support or active component due to its high stability, excellent mechanical properties, and suitable band structure. Iron oxide (Fe2O3) is also an important photocatalytic material due to its abundant reserves, low toxicity, and good visible light absorption. Current technologies mainly focus on the construction of crystalline-crystalline heterojunctions, but their preparation usually requires high-temperature calcination, which easily causes phase transformation and agglomeration, resulting in weak interfacial bonding and a reduction in active sites. In contrast, crystalline-amorphous heterojunctions combine high charge transfer efficiency with abundant active sites, exhibiting greater photocatalytic potential. However, due to the difficulty in precisely controlling the interfacial structure and the ease with which the amorphous phase crystallizes, the preparation of stable and efficient crystalline-amorphous heterojunctions remains challenging.

[0003] Based on the research of crystalline-amorphous heterojunction photocatalysts, the existing technology CN120679565A discloses a Ni@NiS2@MoS x / NF composite catalysts, their preparation methods, and applications. This patent proposes a strategy of directional self-assembly combined with an internal Ni source and water dispersion to construct Ni@NiS2@MoS composites with metal / crystalline / amorphous heterostructures. x The method for preparing the / NF composite catalyst mainly includes: (NH4)2Mo3S 13 MoS₂ was obtained by ultrasonic dispersion and self-assembly upon heating of nH₂O in methanol. x A dispersion of powder; acidification treatment of the nickel foam matrix to form acidified nickel foam; subsequently, the acidified nickel foam is immersed in MoS2. x The dispersion is impregnated and dried. This method utilizes a nickel foam matrix as a self-supplying nickel source and activates its surface through acidification to make it compatible with MoS₂. x In-situ chemical reactions were carried out to immobilize NiS2 and amorphous MoS2 on nickel foam. x The construction of Ni-Mo bimetallic active centers was achieved, demonstrating excellent performance in PMS-activated degradation of antibiotics. However, the construction of its crystalline / amorphous heterostructures depends on the self-supplied nickel source characteristics of the nickel foam and the MoS2 phase. x The hydrothermal self-assembly and the crystalline / amorphous heterostructure building mechanism are relatively simple and difficult to be directly extended to other heterostructure systems of crystalline oxides and amorphous iron oxides.

[0004] In conclusion, developing a method for preparing crystalline-amorphous heterojunction photocatalysts that can solve problems such as difficulty in controlling the crystal phase and weak interfacial bonding has significant scientific and practical value. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing crystalline-amorphous heterojunction photocatalysts, aiming to solve the technical problems in existing technologies such as difficulty in controlling the crystalline phase, weak interfacial bonding, and unstable photocatalytic performance. This invention introduces amorphous Fe2O3 by employing modification, competition, and auxiliary mechanisms, respectively, targeting the characteristics of three different crystalline phases of ZrO2: monoclinic, tetragonal, and cubic phases. This strategy achieves controllable construction of the crystalline-amorphous heterojunction interface, thereby effectively optimizing the carrier migration path and surface reactivity, and significantly improving photocatalytic performance and stability.

[0006] The specific technical solution is as follows:

[0007] A method for preparing a crystalline-amorphous heterojunction photocatalyst is characterized in that, for zirconium oxide with different crystal structures, amorphous iron oxide is introduced onto the surface of the zirconium oxide crystal using modification, competition, or auxiliary mechanisms, respectively, to achieve controllable construction of crystalline zirconium oxide / amorphous iron oxide heterojunctions; the zirconium oxide with different crystal structures is monoclinic zirconium oxide, tetragonal zirconium oxide, and cubic zirconium oxide, and the monoclinic zirconium oxide / amorphous iron oxide heterojunction, tetragonal zirconium oxide / amorphous iron oxide heterojunction, and cubic zirconium oxide / amorphous iron oxide heterojunction are prepared respectively using modification, competition, and auxiliary mechanisms.

[0008] Furthermore, the modification mechanism involves utilizing the active sites on the zirconium oxide surface to uniformly distribute iron ions on the zirconium oxide surface through surface complexation and adsorption, forming an amorphous iron oxide layer after mild heat treatment. The competition mechanism involves the difference in nucleation rates and crystallization kinetics between iron ions and zirconium ions during the zirconium oxide crystallization process, causing iron to competitively precipitate in the form of amorphous iron oxide and adhere to the crystalline zirconium oxide surface. The auxiliary mechanism involves using external field-assisted deposition technology to induce the formation of an amorphous iron oxide layer on the zirconium oxide crystal surface, thereby achieving low-temperature amorphous deposition and maintaining the stability of the zirconium oxide matrix crystal phase.

[0009] Furthermore, the preparation steps of the monoclinic zirconium oxide / amorphous iron oxide heterojunction include: dissolving zirconium oxychloride octahydrate in deionized water to prepare a zirconium precursor aqueous solution; hydrothermally reacting the solution at 180°C for 12 hours; obtaining a monoclinic zirconium oxide crystalline carrier after centrifugation, washing, and drying; and then introducing amorphous iron oxide through a modification mechanism, the steps of which include: dispersing monoclinic zirconium oxide in deionized water to prepare a monoclinic zirconium oxide suspension; preparing an aqueous solution of ferric nitrate nonahydrate; adding it dropwise to the monoclinic zirconium oxide suspension; controlling the molar ratio of iron to zirconium in the system to be 0.1; after the addition is complete; adjusting the pH to 3.0 with 0.1 mol / L dilute ammonia; stirring and adsorbing at room temperature for 12 hours; then centrifuging, washing, and drying; and subjecting the obtained precursor powder to precise heat treatment under a nitrogen atmosphere; and obtaining a monoclinic zirconium oxide / amorphous iron oxide heterojunction after cooling.

[0010] Furthermore, the concentration of the zirconium precursor aqueous solution is 0.25 mol / L; the precise heat treatment conditions are: heating to 250°C at a heating rate of 5°C / min and holding for 3 hours to ensure that the iron oxide component maintains its amorphous structure.

[0011] Furthermore, the preparation steps of the tetragonal zirconium oxide / amorphous iron oxide heterojunction include: dissolving zirconium oxychloride octahydrate and a stabilizer in deionized water to prepare a zirconium / stabilizing element precursor aqueous solution with a zirconium ion concentration of 0.25 mol / L; then introducing amorphous iron oxide through a competitive mechanism, the steps of which include: preparing an aqueous solution of ferric nitrate nonahydrate, adding it to the zirconium / stabilizing element precursor aqueous solution, controlling the overall molar ratio of iron to zirconium to be 0.2, slowly adding ammonia water under stirring to adjust the pH of the system to 8.5, so that zirconium and iron co-nucleate to obtain a coprecipitate suspension, and then subjecting it to hydrothermal treatment at 150°C for 12 hours; centrifuging, washing, and drying the hydrothermal product; and then heat-treating the obtained precursor powder in air atmosphere by heating it to 300°C at 5°C / min and holding it at that temperature for 2 hours, and finally obtaining the tetragonal zirconium oxide / amorphous iron oxide heterojunction after cooling.

[0012] Furthermore, the molar ratio of the stabilizing element to zirconium in the zirconium / stabilizing element precursor aqueous solution is 0.03. By doping with the stabilizing element, the tetragonal zirconium oxide structure can be thermodynamically stabilized and its lattice symmetry can be controlled, preventing it from transforming into a monoclinic phase at room temperature.

[0013] Furthermore, the preparation steps of the cubic zirconia / amorphous iron oxide heterojunction include: dissolving zirconium oxychloride octahydrate and a stabilizer in deionized water to prepare a mixed solution with a zirconium ion concentration of 0.25 mol / L, controlling the molar ratio of the stabilizing element to zirconium to be 0.08, adding urea as a slow-release precipitant, controlling the molar ratio of urea to zirconium to be 4, obtaining a highly symmetric cubic zirconia crystalline carrier by microwave rapid crystallization and high-temperature short-time calcination of the obtained mixed solution, and then introducing amorphous iron oxide through an auxiliary mechanism, the steps of which include: depositing an amorphous iron oxide layer on the surface of the cubic zirconia crystalline carrier using pulsed arc deposition technology, thereby obtaining the cubic zirconia / amorphous iron oxide heterojunction.

[0014] Furthermore, the microwave rapid crystallization and high-temperature short-time calcination method specifically involves heating at 800W microwave power for 5 minutes, followed by cooling, washing, and drying, and then heating to 600°C at a heating rate of 10°C / min, holding at that temperature for 10 minutes, and then quickly removing the product.

[0015] Furthermore, the pulsed arc deposition technique uses a pure iron target as the deposition source and a cubic zirconia crystalline support as the deposition substrate, with the system evacuated to a basic vacuum level of 5 × 10⁻⁶. -5 Pa, then an argon / oxygen mixed atmosphere was introduced with a gas flow ratio of 9:1 to stabilize the total pressure of the argon / oxygen mixture at 0.5 Pa. The pulse voltage, current and frequency of the pulsed arc deposition were set to 400 V, 100 A and 10 Hz, respectively, and deposition was carried out for 6 minutes under these conditions.

[0016] Furthermore, the stabilizer is yttrium hexahydrate, which provides trivalent yttrium ions to stabilize the zirconium oxide crystal phase structure and regulate its lattice symmetry.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) Controllable crystalline and amorphous structures: Based on the unique structural characteristics and surface properties of monoclinic, tetragonal, and cubic zirconia, this invention innovatively employs modification, competition, or auxiliary mechanisms to introduce amorphous iron oxide. This targeted strategy not only precisely maintains the stability of the target crystalline structure of the zirconia core material, avoiding the common problem of crystalline phase transformation in traditional high-temperature preparation processes, but also effectively inhibits the crystallization of iron oxide during heterojunction formation, ensuring its stable existence in an amorphous form. This achieves controllable construction of the crystalline-amorphous hetero interface, overcoming the shortcomings of traditional methods in controlling the crystalline phase.

[0019] (2) Strong interface bonding: Modification mechanism, competition mechanism and auxiliary mechanism respectively established effective and tight bonding between ZrO2 and amorphous Fe2O3 at different levels such as surface adsorption, in-situ precipitation and rapid deposition, which enhanced the stability of heterojunction and reduced the risk of interface peeling. Attached Figure Description

[0020] Figure 1 This invention provides three preparation routes for crystalline zirconium oxide / amorphous iron oxide heterojunctions.

[0021] Figure 2 Comparison of X-ray diffraction results of various embodiments and comparative examples of the present invention;

[0022] Figure 3 High-resolution transmission electron microscope image of the product prepared in Example 1 of this invention;

[0023] Figure 4 This is a high-resolution transmission electron microscope image of the product prepared in Example 2 of the present invention;

[0024] Figure 5 This is a high-resolution transmission electron microscope image of the product prepared in Example 3 of the present invention. Detailed Implementation

[0025] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0026] This invention proposes a method for preparing a crystalline-amorphous heterojunction photocatalyst to achieve the controllable construction of a heterostructure of crystalline zirconium oxide and amorphous iron oxide, as shown in the appendix. Figure 1 This paper describes a method for preparing crystalline zirconia / amorphous iron oxide heterojunctions. Based on the structural characteristics and surface properties of three different crystalline zirconia (ZrO2) phases, amorphous iron oxide (Fe2O3) is introduced onto the ZrO2 crystal surface using modification, competition, and auxiliary mechanisms, respectively, to prepare monoclinic zirconia (m-ZrO2) / amorphous Fe2O3 heterojunctions, tetragonal zirconia (t-ZrO2) / amorphous Fe2O3 heterojunctions, and cubic zirconia (c-ZrO2) / amorphous Fe2O3 heterojunctions. The specific preparation steps are as follows:

[0027] 1. Preparation of m-ZrO2 / amorphous Fe2O3 heterojunction photocatalyst

[0028] (1) Preparation of m-ZrO2 crystalline support

[0029] Zirconium oxychloride octahydrate (ZrOCl2·8H2O) was preferred as the zirconium source. A Zr precursor solution with a concentration of 0.25 mol / L was prepared using deionized water as the solvent. This concentration can effectively inhibit the rapid precipitation of Zr(OH)4 and ensure the uniform hydrolysis and crystallization of zirconium species in the system.

[0030] The prepared solution is transferred to a stainless steel reactor lined with polytetrafluoroethylene. The liquid volume in the reactor does not exceed 80% of the total volume of the reactor body to ensure sufficient steam space and pressure regulation margin during the reaction process.

[0031] The reactor was then placed in an oven and subjected to a hydrothermal reaction at 180°C for 12 hours. Within this temperature range, ZrOCl2 was gradually hydrolyzed to form Zr(OH)4, which underwent a dehydration and crystallization reaction under high temperature and pressure.

[0032] After the hydrothermal reaction is completed, the reactor is allowed to cool naturally to room temperature. The product is then centrifuged to remove the supernatant, and washed alternately with deionized water and anhydrous ethanol until the pH of the washing solution is 7 to remove residual chloride ions and unreacted precursors.

[0033] The washed product was dried in a forced-air drying oven at 80°C for 12 hours to obtain a white powdery m-ZrO2 crystalline support.

[0034] (2) Modification mechanism to introduce amorphous Fe2O3

[0035] The modification mechanism utilizes the active sites on the zirconium oxide surface to uniformly distribute iron ions on the zirconium oxide surface through surface complexation and adsorption. After mild heat treatment, an amorphous iron oxide layer is formed, thereby firmly fixing amorphous Fe2O3 onto the surface of the m-ZrO2 crystalline carrier. The specific steps are as follows:

[0036] The prepared m-ZrO2 crystalline support was dispersed in deionized water and ultrasonically dispersed for 30 minutes to form a uniform suspension.

[0037] Using ferric nitrate nonahydrate (Fe(NO3)3·9H2O) as the iron source, it was dissolved in deionized water to prepare Fe 3+ The precursor aqueous solution, under stirring, contains Fe 3+ The solution was slowly added dropwise to the m-ZrO2 suspension, and the Fe / Zr molar ratio in the system was strictly controlled to be 0.1.

[0038] After the addition is complete, adjust the pH of the mixture to 3.0 with 0.1 mol / L dilute ammonia solution. This condition can effectively inhibit Fe. 3+Rapid hydrolysis and precipitation promotes the adsorption of Fe as hydrated ions or small-sized complexes onto the active sites on the ZrO2 surface. The mixture was continuously stirred at room temperature for 12 hours to allow Fe... 3+ The precursor powder was fully adsorbed onto the surface active sites of m-ZrO2. Subsequently, it was centrifuged, washed with deionized water, and dried in a vacuum oven at 60°C for 6 hours to obtain the precursor powder.

[0039] Finally, the dried precursor powder was placed in a tube furnace and heated to 250°C at a heating rate of 5°C / min under a nitrogen atmosphere, and held at that temperature for 3 hours for a light heat treatment. This step removes residual organic matter and surface-adsorbed moisture, and also induces Fe... 3+ The precursor is transformed into amorphous Fe2O3 on the surface of m-ZrO2 at a temperature much lower than the crystallization temperature of Fe2O3, ensuring its amorphous structure. Finally, cooling yields m-ZrO2 / amorphous Fe2O3 heterojunction photocatalyst powder.

[0040] 2. Preparation of t-ZrO2 / amorphous Fe2O3 heterojunction

[0041] (1) Preparation of aqueous solution of zirconium / yttrium (Zr / Y) precursor

[0042] ZrOCl2·8H2O is preferred as the zirconium source, and yttrium nitrate hexahydrate (Y(NO3)3·6H2O) is used as the stabilizer. ZrOCl2·8H2O and Y(NO3)3·6H2O are dissolved in deionized water at a Y / Zr molar ratio of 0.03 to prepare a Zr... 4+ A 0.25 mol / L Zr / Y precursor aqueous solution was used to ensure sufficient dispersion of metal ions. This was achieved by doping with 3 mol% Y. 3+ It can thermodynamically stabilize the t-ZrO2 phase structure and regulate its lattice symmetry, preventing it from transforming into a monoclinic phase at room temperature.

[0043] (2) Competition mechanism introduces amorphous Fe2O3

[0044] The aforementioned competitive mechanism involves the difference in nucleation rates and crystallization kinetics between iron ions and zirconium ions during the zirconium oxide crystallization process. This allows iron to competitively precipitate and adhere to the crystalline zirconium oxide surface in the form of amorphous iron oxide, achieving an effective and tight bond between t-ZrO2 and amorphous Fe2O3. The specific steps are as follows:

[0045] Using Fe(NO3)3·9H2O as the iron source, Fe was prepared. 3+ An aqueous precursor solution was added to the Zr / Y precursor aqueous solution, controlling the overall Fe / Zr molar ratio to be 0.2. The mixture was then slowly added dropwise with 25 wt% concentrated ammonia solution under strong magnetic stirring until the pH reached 8.5. Under these conditions, Fe...3+ With Zr 4+ When a simultaneous hydrolysis reaction occurs, due to the significant difference between the hydrolysis rate and the nucleation rate of the oxides, Zr(OH)4 tends to form crystal nuclei first, while Fe(OH)3 is coated or embedded on its surface in an amorphous co-deposition manner, forming a competitive co-precipitation structure, resulting in a co-precipitate suspension.

[0046] The resulting coprecipitate suspension was transferred to a stainless steel reactor lined with polytetrafluoroethylene, with the filling degree controlled to not exceed 80% of the total volume. The reactor was placed in an oven and subjected to a hydrothermal reaction at 150°C for 12 hours. This temperature is conducive to the preferential growth of Y-doped ZrO2 nuclei and the stable formation of a tetragonal phase structure. During this process, amorphous Fe(OH)3 is partially dehydrated and transformed into amorphous iron oxide, which is fixed on the surface of ZrO2 grains in the form of coating or dot distribution, thereby realizing the in-situ heterostructure construction of crystalline ZrO2 and amorphous iron oxide.

[0047] After the hydrothermal reaction is completed, the reactor is allowed to cool naturally to room temperature. The product is then separated by centrifugation and washed repeatedly with deionized water and ethanol until the pH reaches 7 to remove residual ions and ligands. The washed product is then dried in an 80°C oven for 8 hours. Finally, the dried product is heated to 300°C in air at a heating rate of 5°C / min and held for 2 hours for short-term low-temperature annealing. This process can thoroughly remove residual nitrate and hydroxyl complexes and promote the stable bonding of the amorphous Fe2O3 layer to the t-ZrO2 surface without crystallization transformation.

[0048] After cooling to room temperature, a crystalline Y-stable t-ZrO2 / amorphous Fe2O3 heterojunction photocatalyst powder was obtained.

[0049] 3. Preparation of crystalline / amorphous Fe2O3 heterojunctions of cubic c-ZrO2

[0050] (1) Preparation of c-ZrO2 support

[0051] ZrOCl2·8H2O was preferred as the zirconium source, and Y(NO3)3·6H2O was used as the stabilizer. To promote the formation of cubic ZrO2 phase and suppress the monoclinic phase transition, the Y / Zr molar ratio was controlled at 8 mol%. ZrOCl2·8H2O and Y(NO3)3·6H2O were dissolved in deionized water to prepare ZrO2. 4+ A mixed solution with a concentration of 0.25 mol / L was prepared by adding urea as a slow-release precipitant and controlling the molar ratio of urea to zirconium ions to be 4:1. The solution was stirred until homogeneous. The urea decomposes under heating conditions to generate NH3 and CO2, which can slowly adjust the pH of the system and improve the uniformity of precipitation.

[0052] The mixed solution was placed in a pressure-resistant glass container and then placed in a microwave reaction system. It was heated at 800W for 5 minutes to perform microwave-assisted rapid crystallization. Rapid microwave heating can promote nucleation and phase transformation, forming a preliminary crystalline Y-doped ZrO2 precursor.

[0053] After cooling to room temperature, the product was removed and washed alternately with deionized water and anhydrous ethanol until the pH reached 7. It was then dried at 80°C for 8 hours using a forced-air drying method. The dried product was then heated to 600°C in a muffle furnace at a heating rate of 10°C / min, held at that temperature for 10 minutes, and then quickly removed. This short period of high temperature promotes lattice rearrangement and oxygen vacancy stabilization, ensuring the formation of the c-ZrO2 phase while preventing particle agglomeration, thus obtaining a Y-stable c-ZrO2 crystalline support.

[0054] (2) Auxiliary mechanism to introduce amorphous Fe2O3

[0055] The auxiliary mechanism involves inducing the formation of an amorphous iron oxide layer on the surface of a zirconia crystal using an external field-assisted deposition technique, thereby achieving low-temperature amorphous deposition while maintaining the crystalline phase stability of the zirconia matrix. This invention employs pulsed arc deposition (APD) technology to deposit an amorphous Fe2O3 thin layer on the c-ZrO2 surface. This method can form a high-bonding-strength, defect-rich amorphous oxide layer at low temperatures, making it an effective means of constructing heterogeneous interfaces using an auxiliary mechanism.

[0056] The prepared c-ZrO2 powder was uniformly spread on the sample holder of the APD device as a deposition substrate, and a pure iron target was used as the deposition source. The system was evacuated to a basic vacuum of 5 × 10⁻⁶. -5 The pressure was initially set at 0.5 Pa, followed by the introduction of an argon / oxygen (Ar / O2) mixed atmosphere with a gas flow ratio of 9:1, an Ar flow rate of 90 sccm, and an O2 flow rate of 10 sccm. The total pressure of the Ar / O2 mixture within the reaction chamber was stabilized at 0.5 Pa. The APD pulse voltage was set to 400 V, the current to 100 A, and the frequency to 10 Hz. Deposition was carried out under these conditions for 6 min. The iron oxide formed during deposition was amorphous / non-crystalline and rich in defects. After cooling and removal of the sample within the aforementioned process atmosphere, this disordered oxide formed a continuous, dense thin layer covering the surface of the c-ZrO2 powder, thus constructing a c-ZrO2 / non-crystalline Fe2O3 heterojunction. After deposition, the atmosphere was closed, and the product was removed after the chamber cooled to room temperature, yielding a Y-stable c-ZrO2 / non-crystalline Fe2O3 heterojunction photocatalyst powder.

[0057] Table 1 shows the reagents used in the following examples and comparative examples.

[0058] ;

[0059] Example 1

[0060] Preparation of m-ZrO2 / amorphous Fe2O3 heterostructure

[0061] (1) Preparation of m-ZrO2 crystalline support: ZrOCl2·8H2O (3.22 g, 0.01 mol) was dissolved in 40 mL of deionized water and then transferred to a 50 mL polytetrafluoroethylene-lined stainless steel reactor. The reaction was carried out hydrothermally at 180°C for 12 h. After cooling, the supernatant was removed by centrifugation at 8000 rpm for 5 min. The sample was washed three times each with deionized water and anhydrous ethanol until the pH of the washing solution was 7. The washed sample was dried at 80°C for 12 h to obtain 1.0 g m-ZrO2.

[0062] (2) Introduction of amorphous Fe2O3: m-ZrO2 (0.45 g, 0.005 mol) was dispersed in 50 mL of deionized water to obtain an m-ZrO2 suspension. Separately, Fe(NO3)3·9H2O (0.20 g, 0.0005 mol) was dissolved in 10 mL of deionized water to obtain Fe2O3 suspension. 3+ Precursor solution, Fe 3+ The precursor solution was slowly added dropwise to the m-ZrO2 suspension. After the addition was complete, the pH was adjusted to 3.0 with 0.1 mol / L dilute ammonia. The mixture was magnetically stirred at room temperature for 12 hours, followed by centrifugation. The mixture was then washed twice with deionized water to remove unbound Fe. 3+ The washed sample was vacuum dried at 60°C for 6 hours, and then heated to 250°C at a heating rate of 5°C / min under a nitrogen atmosphere, held for 3 hours, and cooled to room temperature. The resulting sample was designated M-ZF-1.

[0063] Example 2

[0064] Preparation of t-ZrO2 / amorphous Fe2O3 heterojunction

[0065] (1) Preparation of Zr / Y precursor aqueous solution: Weigh ZrOCl2·8H2O (2.5g, 0.008mol) and Y(NO3)3·6H2O (0.092g, 0.00024mol) and dissolve them in 32mL of deionized water to prepare Zr / Y precursor solution.

[0066] (2) Introduction of amorphous Fe2O3: Take Fe(NO3)3·9H2O (0.65g, 0.0016mol) and dissolve it in 10mL of deionized water. Add it to the above Zr / Y precursor solution. Under magnetic stirring, slowly add concentrated ammonia water with a concentration of 25wt% to the Zr / Y precursor solution until the pH is 8.5. Transfer the resulting suspension to a 100mL polytetrafluoroethylene-lined stainless steel reactor and hydrothermally treat it at 150°C for 12 hours. After the reaction is completed, cool it naturally to room temperature, centrifuge it, wash it with deionized water and ethanol until the pH is 7, dry it at 80°C for 8 hours, and finally heat it to 300°C at a heating rate of 5°C / min in air atmosphere, keep it at the temperature for 2 hours, and cool it to obtain Y-stable t-ZrO2 / amorphous Fe2O3 heterojunction photocatalyst powder, which is denoted as T-ZF-1.

[0067] Example 3

[0068] Preparation of c-ZrO2 / amorphous Fe2O3 heterostructure

[0069] (1) Preparation of c-ZrO2 crystalline support: Weigh ZrOCl2·8H2O (2.5g, 0.008mol) and Y(NO3)3·6H2O (0.24g, 0.00063mol), dissolve in 32mL of deionized water, add 1.9g of urea, place the mixed solution in a laboratory microwave oven, heat at 800W for 5 minutes, cool to room temperature and take out the product, wash with deionized water and anhydrous ethanol alternately until pH is 7, dry at 80°C for 8 hours, and finally heat to 600°C in a muffle furnace at a heating rate of 10°C / min, calcine rapidly for 10min and then cool to obtain Y-stable c-ZrO2 powder.

[0070] (2) Introduction of amorphous Fe2O3: The c-ZrO2 powder prepared above is uniformly spread on the APD sample holder, and the system is evacuated to a basic vacuum of 5×10⁻⁶ using a pure Fe target as the source. -5 A gas mixture of Ar / O2 was introduced at a flow rate ratio of Ar:O2 = 9:1, and the total pressure of the mixture was 0.5 Pa. The APD pulse voltage was set to 400 V, the current to 100 A, and the frequency to 10 Hz. After deposition for 6 min, the mixture was cooled to room temperature to obtain Y-stable c-ZrO2 / amorphous Fe2O3 heterojunction photocatalyst powder, denoted as C-ZF-1.

[0071] Sample testing

[0072] Refer to GB / T 30904-2014 "X-ray Diffraction Method for Crystal Structure Analysis of Inorganic Chemical Products".

[0073] 1. X-ray diffraction (XRD)

[0074] Instrument: X-ray diffractometer, equipped with Cu Kα radiation source (λ=1.5406Å).

[0075] Sample preparation: Spread the prepared catalyst powder sample evenly on a low background sample holder, ensuring that the sample surface is flat and the powder layer thickness is moderate in order to obtain a good diffraction signal.

[0076] Parameter settings: tube voltage: 40kV; tube current: 40mA; intensity: 3000cps; scanning range (2θ): 20°-80°; scanning rate: 5° / min; step size: 0.02°; dwell time for each step: 0.5s-1s.

[0077] Data analysis: The crystal phases of each component in the sample were identified by comparison with the Joint Powder Diffraction Standard (JCPDS) cards: m-ZrO2: JCPDS-37-1484, t-ZrO2: JCPDS-80-0965, c-ZrO2: JCPDS-27-0997, α-Fe2O3: JCPDS-33-0664.

[0078] 2. High-resolution transmission electron microscopy (HRTEM)

[0079] Instrument: High-resolution transmission electron microscope.

[0080] Sample preparation: Disperse a small amount of catalyst powder in anhydrous ethanol using ultrasound, add a small drop of suspension to a copper grid coated with an ultrathin carbon film, allow it to dry naturally, and then place it in a sample holder.

[0081] Parameter settings: TEM mode; accelerating voltage: 200kV.

[0082] Data analysis: HRTEM was used to observe the overall morphology, particle size, degree of aggregation, and microstructure of the heterojunction interface of the samples.

[0083] Analysis of Experimental Results

[0084] (1) X-ray diffraction results:

[0085] As attached Figure 2 As shown in Example 1: Preparation of M-ZF-1. The main diffraction peaks of the XRD pattern are located at 2θ=24.2°, 28.2°, 31.5° and 34.5°, consistent with JCPDS-37-1484. The characteristic diffraction peaks of α-Fe2O3 at 2θ=33.1°, 35.6° and 40.9° were not observed. However, a broad and low-intensity band appeared in the 30°-40° region, indicating that Fe2O3 exists in an amorphous form.

[0086] Example 2: T-ZF-1 was prepared. XRD showed characteristic diffraction peaks at 2θ = 30.2°, 35.2°, 50.6° and 60.2°, consistent with JCPDS-80-0965. No characteristic diffraction peaks of α-Fe2O3 were observed. However, a broad and low-intensity band appeared in the 30°-40° region, indicating that Fe2O3 remains amorphous on the t-ZrO2 surface.

[0087] Example 3: C-ZF-1 was prepared. XRD showed characteristic diffraction peaks at 2θ = 30.1°, 35.1°, 50.5° and 60.2°, consistent with JCPDS-27-0997. No characteristic diffraction peaks of α-Fe2O3 were observed. However, a broad and low-intensity band appeared in the 30°-40° region, indicating that Fe2O3 remains amorphous on the c-ZrO2 surface.

[0088] (2) Results of high-resolution transmission electron microscopy:

[0089] As attached Figure 3-5 As shown, the HRTEM images of Examples 1-3 clearly display the lattice fringes of crystalline ZrO2, and a disordered amorphous Fe2O3 outer layer is observed to form on the surface of ZrO2 nanocrystals, with a clear, continuous, and tightly bonded heterostructure interface. This further confirms the successful loading of amorphous Fe2O3 and the effective construction of the crystalline-amorphous heterostructure.

[0090] In summary, this invention successfully prepared a crystalline-amorphous heterojunction photocatalyst with controllable crystalline phase and strong interfacial bonding through crystalline phase control and the introduction of amorphous iron oxide. XRD and HRTEM structural characterization show that the strategy of this invention effectively realizes the construction of crystalline-amorphous heterojunctions, providing a novel and universal approach for the design and development of efficient crystalline-amorphous heterojunction photocatalysts.

Claims

1. A method for preparing a crystalline-amorphous heterojunction photocatalyst, characterized by The crystalline amorphous heterostructure is a monoclinic zirconium oxide / amorphous iron oxide heterostructure. The catalyst preparation steps include: dissolving zirconium oxychloride octahydrate in deionized water to prepare a zirconium precursor aqueous solution; hydrothermally reacting the solution at 180°C for 12 hours; obtaining a monoclinic zirconium oxide crystalline support after centrifugation, washing, and drying; and then introducing amorphous iron oxide through a modification mechanism, the steps of which include: dispersing monoclinic zirconium oxide in deionized water to prepare a monoclinic zirconium oxide suspension; preparing an aqueous solution of ferric nitrate nonahydrate; and adding it dropwise to the monoclinic zirconium oxide suspension. In the controlled system, the molar ratio of iron to zirconium was 0.

1. After the addition was complete, the pH was adjusted to 3.0 with 0.1 mol / L dilute ammonia. The mixture was stirred and adsorbed at room temperature for 12 hours, followed by centrifugation, washing, and drying. The resulting precursor powder was then subjected to precise heat treatment under a nitrogen atmosphere. After cooling, a monoclinic zirconium oxide / amorphous iron oxide heterojunction was obtained. The concentration of the zirconium precursor aqueous solution was 0.25 mol / L. The precise heat treatment conditions were: heating to 250°C at a rate of 5°C / min and holding for 3 hours to ensure that the iron oxide component maintained its amorphous structure.

2. A method for preparing a crystalline-amorphous heterojunction photocatalyst, characterized by The crystalline amorphous heterostructure is a tetragonal zirconium oxide / amorphous iron oxide heterostructure. The catalyst preparation steps include: dissolving zirconium oxychloride octahydrate and yttrium nitrate hexahydrate in deionized water to prepare a zirconium / yttrium precursor aqueous solution with a zirconium ion concentration of 0.25 mol / L; then introducing amorphous iron oxide through a competitive mechanism, the steps of which include: preparing an aqueous solution of ferric nitrate nonahydrate, adding it to the zirconium / yttrium precursor aqueous solution, controlling the overall molar ratio of iron to zirconium to be 0.2, and slowly adding ammonia water under stirring to adjust the pH of the system to 8.5, so that zirconium... The precursor is nucleated with iron to obtain a coprecipitate suspension, which is then subjected to hydrothermal treatment at 150°C for 12 hours. The hydrothermal product is centrifuged, washed, and dried. The resulting precursor powder is then heat-treated in air at a rate of 5°C / min to 300°C and held for 2 hours. After cooling, a tetragonal zirconium oxide / amorphous iron oxide heterostructure is obtained. The molar ratio of yttrium to zirconium in the zirconium / yttrium precursor aqueous solution is 0.

03. By doping with yttrium, the tetragonal zirconium oxide structure can be thermodynamically stabilized and its lattice symmetry can be controlled to prevent it from transforming into a monoclinic phase at room temperature.

3. A method for preparing a crystalline-amorphous heterojunction photocatalyst, characterized by The crystalline amorphous heterostructure is a cubic zirconium oxide / amorphous iron oxide heterostructure. The catalyst preparation steps include: dissolving zirconium oxychloride octahydrate and yttrium nitrate hexahydrate in deionized water to prepare a mixed solution with a zirconium ion concentration of 0.25 mol / L, controlling the molar ratio of yttrium to zirconium at 0.08, adding urea as a slow-release precipitant, controlling the molar ratio of urea to zirconium at 4, obtaining a highly symmetric cubic zirconium oxide crystalline support by microwave rapid crystallization and high-temperature short-time calcination of the obtained mixture, and then introducing amorphous iron oxide through an auxiliary mechanism. The steps include... The process includes: depositing an amorphous iron oxide layer on the surface of a cubic zirconia crystalline support using pulsed arc deposition technology to obtain a cubic zirconia / amorphous iron oxide heterojunction. The microwave rapid crystallization and high-temperature short-time calcination method specifically involves heating at 800W microwave power for 5 minutes, followed by cooling, washing, and drying, then heating to 600℃ at a heating rate of 10℃ / min, holding at that temperature for 10 minutes, and then rapidly removing the sample. The pulsed arc deposition technology uses a pure iron target as the deposition source and a cubic zirconia crystalline support as the deposition substrate. The system is evacuated to a basic vacuum level of 5×10⁻⁶. -5 Pa, then an argon / oxygen mixed atmosphere was introduced with a gas flow ratio of 9:1 to stabilize the total pressure of the argon / oxygen mixture at 0.5 Pa. The pulse voltage, current and frequency of the pulsed arc deposition were set to 400 V, 100 A and 10 Hz, respectively, and deposition was carried out for 6 minutes under these conditions.

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