Perovskite nanowire photocatalyst as well as preparation method and application thereof

Abstract

The invention relates to a perovskite nanowire photocatalyst and a preparation method and application thereof.The preparation method comprises the following steps that a substrate is coated with a Pb precursor solution, first annealing is conducted, a substrate containing a Pb precursor layer is obtained, then the substrate containing the Pb precursor layer is placed in a CsX solution to be subjected to standing, and the Pb precursor layer is obtained; the preparation method comprises the following steps: carrying out primary annealing on a perovskite CsPbX3 nanowire photocatalyst precursor to obtain a perovskite CsPbX3 nanowire photocatalyst precursor, and carrying out secondary annealing on the perovskite CsPbX3 nanowire photocatalyst precursor to obtain the perovskite CsPbX3 nanowire photocatalyst, wherein X in the CsX solution comprises any one or a combination of at least two of Cl <->, Br <-> and I <->; the perovskite nanowire photocatalyst with excellent photoelectric conversion capability is prepared by adopting a solution method, shows excellent catalytic activity and high selectivity when being used for catalyzing alcohol directional oxidation and aldehyde condensation reaction, and provides an innovative path for green synthesis of high-added-value fine chemicals; wide industrial application prospects are shown in the field of manufacturing of high-end chemicals such as medical intermediates and spices.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of perovskite synthesis and photocatalytic application, and particularly relates to a perovskite nanowire photocatalyst and a preparation method and application thereof. BACKGROUND

[0002] At present, the selective oxidation of alcohols to prepare carbonyl compounds (aldehydes / ketones) and the condensation reaction of aldehydes play an irreplaceable core role in the field of fine chemical synthesis. However, the current mainstream catalysts (such as TiO2, Bi2WO6 and other wide-bandgap oxide semiconductors) generally face the dual bottlenecks of high synthesis cost and insufficient catalytic activity, which not only limits the feasibility of industrial application, but also makes it difficult to meet the demand for high selectivity conversion of alcohol oxidation reaction and aldehyde condensation reaction. Therefore, developing a new type of photocatalyst with low-cost controllable preparation, stable catalytic process and outstanding product selectivity has become a research direction that needs to be broken through in the field of alcohol directional oxidation and aldehyde condensation reaction.

[0003] Halide perovskite materials have shown great application potential in many optoelectronic conversion fields such as light-emitting diodes, solar cells, photodetectors, lasers and photocatalysis due to their excellent light absorption coefficient, carrier diffusion length and fluorescence quantum yield. Semiconductor nanowires exhibit one-dimensional charge and photon transport characteristics, and can be used for the next generation of optoelectronic devices. Compared with semiconductor nanosheets, quantum dots or thin films, semiconductor nanowires exhibit more excellent photocatalytic performance, and semiconductor nanowires are also an excellent platform for exploring phenomena at the nanoscale. However, due to the ion characteristics of perovskite materials, the kinetic disorder is stronger, and the solubility in water and polar solvents is higher, and the energy barrier for forming crystals is lower, which makes it easier to synthesize and ion exchange at low temperature, thereby providing a new opportunity for growing perovskite nanostructures.

[0004] However, the current research and photocatalytic application of perovskite nanostructures still face many challenges. In terms of preparation, the traditional nanostructure preparation method has problems such as complex process and high cost, which makes it difficult to mass-produce perovskite nanostructures. For example, CN110767811A discloses a MAPbI3 single crystal nanowire photodetector and a preparation method. One-dimensional lead iodide single crystal nanowires are grown by chemical vapor deposition under the catalysis of metal nanometer islands. Then, the lead iodide single crystal nanowires are converted into MAPbI3 single crystal nanowires by chemical vapor deposition. The MAPbI3 nanowire photodetector is prepared by transferring the MAPbI3 nanowires to a glass substrate and evaporating electrodes. The equipment used in the chemical deposition in this preparation method is too complex, and the high-temperature operation requires higher requirements for instruments and equipment, which is not suitable for mass production and limits its further application in optoelectronic devices.

[0005] To overcome these limitations, researchers have recently begun exploring more convenient strategies for synthesizing perovskite nanowires and more stable perovskite photocatalytic materials. CsPbBr3 stands out among many perovskite materials due to its large absorption coefficient, high photoluminescence quantum yield, and better environmental stability. Furthermore, solution methods have become a popular approach for perovskite synthesis due to their simplicity and low cost, but they still have many drawbacks.

[0006] For example, CN109775750B discloses a solution method for preparing all-inorganic perovskite CsPbBr3 nanowires and upconversion luminescent materials. The method uses a proportional mixture of oleylamine, oleic acid, and octadecene as a solvent, adds lead and cesium sources as reactants, and conducts the reaction in a water-free environment. Subsequently, through stages of heating, holding, and cooling, the nucleation, growth, and maturation of the nanowires are completed. After the reaction, solid-liquid separation is performed to remove solvent residues, thus obtaining all-inorganic perovskite CsPbBr3 nanowires. Although this method avoids high-temperature operation and requires no complex equipment, meeting the requirements for mass production, it introduces ligands during the preparation process, and the synthesis operation is still not simplified enough.

[0007] For example, CN113856755A discloses a CsPbBr 3-x I x A quantum dot@COF-5 composite photocatalyst material, which combines COF-5 with CsPbBr 3-x I x Quantum dot composites form heterojunction structures, enhancing the photocatalytic CO2 reduction efficiency and improving CO2 photocatalytic reduction performance. However, its performance in CsPbBr... 3-x I x The introduction of ligands in the synthesis of quantum dots complicates the catalytic system and makes it difficult to study the catalytic process. In addition, CsPbBr3 has diverse crystal structures. CsPbBr3 with excellent photoelectric properties has a high degree of crystal symmetry, making it difficult to form a one-dimensional structure without the participation of ligands. However, CsPbBr3 crystal forms with low crystal symmetry are metastable at room temperature, which makes the synthesis of one-dimensional CsPbBr3 nanostructures without ligands even more difficult.

[0008] Therefore, how to provide a perovskite nanowire photocatalyst and its preparation method, which has advantages such as large light absorption coefficient, long carrier diffusion length and high fluorescence quantum yield, and whose preparation method is simple, requires no ligand addition and no complex equipment, and can achieve highly selective conversion when used for alcohol-directed oxidation and / or aldehyde condensation reactions, is an urgent problem to be solved in this field. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a perovskite nanowire photocatalyst, its preparation method, and its application. The perovskite nanowire photocatalyst exhibits excellent photoelectric conversion capabilities and demonstrates high conversion rates and high selectivity when applied to alcohol-directed oxidation and / or aldehyde condensation reactions. Furthermore, the preparation method is simple in process, requires no additional ligands, and necessitates no complex equipment, making it easy for mass production.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a method for preparing a perovskite nanowire photocatalyst, the method comprising the following steps:

[0012] A Pb precursor solution is coated onto a substrate and subjected to a first annealing to obtain a substrate containing a Pb precursor layer. The substrate containing the Pb precursor layer is then placed in a CsX solution and allowed to stand to obtain a perovskite CsPbX3 nanowire photocatalyst precursor. The perovskite CsPbX3 nanowire photocatalyst precursor is then subjected to a second annealing to obtain a perovskite CsPbX3 nanowire photocatalyst.

[0013] In the CsX solution, X includes Cl. - ,Br - Or I - Any one or at least two of the above, wherein typical but non-limiting combinations include Cl - and Br - Combination, Br - and I - Combination or Cl - and I - Combinations, etc.

[0014] This invention employs a solution method to first prepare a perovskite nanowire photocatalyst precursor with low crystal symmetry and relatively weak photoelectric performance. Then, based on a material structure-activity relationship regulation strategy, a structural phase transition is induced in the perovskite nanowire photocatalyst precursor through heating, i.e., a second annealing, transforming it from a δ-phase (orthogonal) to a γ-phase (orthogonal), thereby enhancing photoelectric conversion capacity and improving its photocatalytic activity and selectivity. The preparation method can obtain a one-dimensional nanowire structured perovskite nanowire photocatalyst without the addition of ligands, and the process is simple, requires no complex equipment, and is easy to mass-produce.

[0015] Preferably, the Pb precursor solution contains PbM2, wherein M includes Cl. - ,Br - I - or CH3COO - Any one or at least two of the following; wherein typical but non-limiting combinations include Cl - and Br- Combinations, etc., Br - and I - Combination or I - and CH3COO - Combinations, etc.

[0016] Preferably, the concentration of the Pb precursor solution is 0.1~2 mol / L, for example, it can be 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L or 2 mol / L, etc., and is preferably 0.1~1 mol / L.

[0017] Preferably, the concentration of the CsX solution is 2~16 mg / mL, for example, it can be 2 mg / mL, 5 mg / mL, 8 mg / mL, 10 mg / mL, 12 mg / mL, 15 mg / mL or 16 mg / mL, etc., and more preferably 3~6 mg / mL.

[0018] Preferably, the mass ratio of PbM2 in the Pb precursor layer to CsX in the CsX solution is (0.001~0.01):1, for example, it can be 0.001:1, 0.003:1, 0.005:1, 0.008:1 or 0.01:1, etc.

[0019] Preferably, the coating method includes spin coating and / or drop coating, with spin coating being the preferred method.

[0020] Preferably, the spin coating speed is 2000~4000 r / min, for example, it can be 2000 r / min, 2500 r / min, 3000 r / min, 3500 r / min or 4000 r / min, etc.

[0021] Preferably, the spin coating time is 30~60s, for example, it can be 30s, 35s, 40s, 45s, 50s, 55s or 60s.

[0022] Preferably, the temperature of the first annealing is 50~150℃, for example, it can be 50℃, 80℃, 100℃, 130℃ or 150℃, and is more preferably 100~150℃.

[0023] The present invention further optimizes the first annealing temperature to be 100~150℃, which is beneficial to the uniform distribution of the Pb precursor layer. If the first annealing temperature is too high, the solvent of the Pb precursor solution will evaporate too quickly, thereby affecting the uniformity of the Pb precursor layer. If the first annealing temperature is too low, the solvent of the Pb precursor solution will evaporate too slowly, thereby affecting the efficiency.

[0024] Preferably, the first annealing time is 5 to 30 minutes, for example, it can be 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes.

[0025] Preferably, the preparation method further includes plasma treatment of the substrate before coating.

[0026] Preferably, the settling temperature is 0~100℃, for example, it can be 0℃, 10℃, 20℃, 22℃, 24℃, 26℃, 28℃, 30℃, 32℃, 35℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃, etc., preferably 20~35℃.

[0027] The present invention further preferably uses a settling temperature of 20~35℃, which is beneficial to the growth of perovskite. If the settling temperature is too low, the growth rate of perovskite will be too slow, thus affecting efficiency. If the settling temperature is too high, the morphology of perovskite will be difficult to control, thus making it impossible to form a uniform one-dimensional nanowire structure.

[0028] Preferably, the settling time is 1 to 48 hours, for example, it can be 1 hour, 5 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours or 48 hours, and preferably 4 to 24 hours.

[0029] Preferably, the temperature of the second annealing is 100~300℃, for example, it can be 100℃, 120℃, 150℃, 180℃, 200℃, 220℃, 250℃, 280℃ or 300℃, etc., preferably 150~200℃.

[0030] The present invention further preferably uses a second annealing temperature of 150~200℃, which is beneficial to achieve the phase transformation of the perovskite CsPbX3 nanowire photocatalyst precursor. If the second annealing temperature is too low, the perovskite CsPbX3 nanowire photocatalyst precursor will not be able to achieve phase transformation. If the second annealing temperature is too high, the perovskite CsPbX3 nanowire photocatalyst precursor will decompose.

[0031] Preferably, the second annealing time is 1 to 20 minutes, for example, it can be 1 minute, 2 minutes, 5 minutes, 10 minutes, 15 minutes, 18 minutes or 20 minutes, and preferably 5 to 10 minutes.

[0032] In a second aspect, the present invention provides a perovskite nanowire photocatalyst, which is prepared by the method for preparing perovskite nanowire photocatalyst described in the first aspect.

[0033] The perovskite nanowire photocatalyst of this invention has a one-dimensional nanowire structure with uniform size distribution, and has advantages such as large light absorption coefficient, long carrier diffusion length and high fluorescence quantum yield.

[0034] Preferably, the perovskite nanowire photocatalyst has the chemical formula CsPbX3, wherein X includes Cl. - ,Br - Or I - Any one or at least two of the above, wherein typical but non-limiting combinations include Cl - and Br - Combination, Br - and I - Combination or Cl - and I - Combinations, etc.

[0035] Preferably, the crystal structure of the perovskite nanowire photocatalyst includes a γ phase.

[0036] Preferably, the aspect ratio of the nanowire structure in the perovskite nanowire photocatalyst is (15~40):1, for example, it can be 15:1, 20:1, 25:1, 30:1, 35:1 or 40:1, etc.

[0037] Thirdly, the present invention provides a method for preparing aldehydes by alcohol oxidation, wherein the method employs the perovskite nanowire photocatalyst described in the second aspect.

[0038] The method for preparing aldehydes by alcohol oxidation provided by the present invention uses the perovskite nanowire photocatalyst described in the second aspect, which achieves efficient conversion of alcohols and high selectivity in preparing the corresponding aldehyde products.

[0039] It is worth noting that the perovskite nanowire photocatalyst described in this invention is widely applicable to the oxidation of common alcohols (aromatic alcohols and / or fatty alcohols) to aldehydes, or the oxidation of fatty alcohols to ketones. This invention primarily uses the oxidation of benzyl alcohol to benzaldehyde as an example. The mechanism by which the perovskite nanowire photocatalyst catalyzes the oxidation of alcohols to aldehydes is as follows: during the reaction, the CH bonds in the holes of the perovskite nanowire photocatalyst are activated, oxidizing to RC·HOH, while simultaneously generating H₂. + Electrons reduce oxygen to superoxide anion radicals; simultaneously, superoxide anion radicals and H+... + HOO· is generated by combination; further, RC·HOH reacts with HOO· to ​​generate an aldehyde. Preferably, the method includes the following steps: a mixed alcohol solution and the perovskite nanowire photocatalyst undergo a first catalytic reaction, followed by a first separation to obtain the corresponding aldehyde product.

[0040] Preferably, the alcohol in the alcohol solution includes aromatic alcohols and / or fatty alcohols.

[0041] Preferably, the aromatic alcohol comprises benzyl alcohol and / or p-methylbenzyl alcohol.

[0042] Preferably, the fatty alcohol includes n-hexanol.

[0043] Preferably, the solvent in the alcohol solution includes any one or a combination of at least two of toluene, cyclohexane, acetonitrile, methanol, or ethanol, wherein typical but non-limiting combinations include combinations of toluene and cyclohexane, combinations of cyclohexane and acetonitrile, or combinations of toluene and acetonitrile, etc., preferably acetonitrile.

[0044] Preferably, the concentration of the alcohol solution is 3~10 μmol / mL, for example, it can be 3 μmol / mL, 4 μmol / mL, 5 μmol / mL, 8 μmol / mL or 10 μmol / mL.

[0045] Preferably, the amount of the perovskite nanowire photocatalyst is 0.1~20 mg / mL, for example, it can be 0.1 mg / mL, 0.5 mg / mL, 1 mg / mL, 5 mg / mL, 8 mg / mL, 10 mg / mL, 12 mg / mL, 15 mg / mL, 18 mg / mL or 20 mg / mL, etc.

[0046] Preferably, the light source used in the first catalytic reaction includes ultraviolet light and / or visible light.

[0047] Preferably, the time for the first catalytic reaction is 0.1 to 2 hours, for example, it can be 0.1 hours, 0.5 hours, 1 hour, 1.2 hours, 1.5 hours, 1.8 hours or 2 hours.

[0048] Preferably, the first separation includes a first centrifugation and a first rotary evaporation performed sequentially.

[0049] Preferably, the rotation speed of the first centrifuge is 6000~10000 r / min, for example, it can be 6000 r / min, 7000 r / min, 8000 r / min, 9000 r / min or 10000 r / min, etc.

[0050] Preferably, the first centrifugation time is 1 to 5 minutes, for example, it can be 1 minute, 2 minutes, 3 minutes, 4 minutes or 5 minutes.

[0051] Preferably, the temperature of the first rotary evaporation is 40~80℃, for example, it can be 40℃, 50℃, 60℃, 70℃ or 80℃.

[0052] Preferably, the first rotary evaporation time is 1 to 10 minutes, for example, it can be 1 minute, 3 minutes, 5 minutes, 7 minutes, 9 minutes or 10 minutes.

[0053] Fourthly, the present invention provides a method for the condensation of aldehydes, wherein the method employs the perovskite nanowire photocatalyst described in the second aspect.

[0054] The aldehyde condensation method provided by this invention uses the perovskite nanowire photocatalyst described in the second aspect to achieve selective and efficient aldehyde condensation.

[0055] It is worth noting that the perovskite nanowire photocatalyst described in this invention is widely applicable to the condensation reaction of common aldehydes (aromatic aldehydes and aliphatic aldehydes, such as benzaldehyde, p-methoxybenzaldehyde, cinnamaldehyde, n-pentanal or n-butyraldehyde, etc.). This invention mainly uses the condensation reaction of benzaldehyde as an example to demonstrate the process.

[0056] The mechanism of the condensation reaction of aldehydes catalyzed by the perovskite nanowire photocatalyst is as follows: the condensation reaction generates H+ by activating water in the holes of the perovskite nanowire photocatalyst. + The generated H + It combines with aldehydes and gains electrons to produce RC·HOH; the electrons reduce oxygen to superoxide anion radicals; it further reacts with RC=O to generate aldehyde condensation products (e.g., 2 molecules of benzaldehyde condense to give 1 molecule of benzoin); furthermore, the aldehyde condensation products can be further oxidized (e.g., benzoin can be further oxidized to benzoyl).

[0057] Preferably, the condensation method includes the following steps: a second catalytic reaction is carried out between a mixed aldehyde solution and the perovskite nanowire photocatalyst, followed by a second separation to obtain the corresponding aldehyde condensation product.

[0058] If the aldehyde in the aldehyde solution is benzaldehyde, then the corresponding aldehyde condensation product is benzoin. If the reaction time is extended, the benzoin will be oxidized to benzoyl.

[0059] Preferably, the aldehydes in the aldehyde solution include aromatic aldehydes and / or aliphatic aldehydes.

[0060] Preferably, the aromatic aldehyde includes benzaldehyde and / or p-methylbenzaldehyde.

[0061] Preferably, the fatty aldehyde includes n-pentanal.

[0062] Preferably, the solvent in the aldehyde solution includes any one or a combination of at least two of toluene, cyclohexane, acetonitrile, methanol, or ethanol, wherein typical but non-limiting combinations include combinations of toluene and cyclohexane, combinations of cyclohexane and acetonitrile, or combinations of toluene and methanol, etc., preferably acetonitrile.

[0063] Preferably, the concentration of the aldehyde solution is 5~15 μmol / mL, for example, it can be 5 μmol / mL, 8 μmol / mL, 10 μmol / mL, 12 μmol / mL or 15 μmol / mL.

[0064] Preferably, the amount of the perovskite nanowire photocatalyst is 0.1~20 mg / mL, for example, it can be 0.1 mg / mL, 0.5 mg / mL, 1 mg / mL, 5 mg / mL, 8 mg / mL, 10 mg / mL, 12 mg / mL, 15 mg / mL, 18 mg / mL or 20 mg / mL, etc.

[0065] Preferably, the light source for the second catalytic reaction includes ultraviolet light and / or visible light.

[0066] Preferably, the time for the second catalytic reaction is 5 to 60 minutes, for example, 5 minutes, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, or 60 minutes.

[0067] Preferably, the second separation includes a second centrifugation and a second rotary evaporation performed sequentially.

[0068] Preferably, the rotation speed of the second centrifuge is 6000~10000 r / min, for example, it can be 6000 r / min, 7000 r / min, 8000 r / min, 9000 r / min or 10000 r / min, etc.

[0069] Preferably, the second centrifugation time is 1 to 5 minutes, for example, it can be 1 minute, 2 minutes, 3 minutes, 4 minutes or 5 minutes.

[0070] Preferably, the temperature of the second rotary evaporation is 40~80℃, for example, it can be 40℃, 50℃, 60℃, 70℃ or 80℃.

[0071] Preferably, the second rotary evaporation time is 1 to 10 minutes, for example, it can be 1 minute, 3 minutes, 5 minutes, 7 minutes, 9 minutes or 10 minutes.

[0072] Compared with the prior art, the present invention has at least the following beneficial effects:

[0073] (1) The preparation method of the perovskite nanowire photocatalyst provided by the present invention adopts the solution method. First, a perovskite nanowire photocatalyst precursor with low crystal symmetry and weak photoelectric performance is prepared. Then, the perovskite nanowire photocatalyst precursor is induced to undergo a structural phase transition by heating, i.e., second annealing, so that it changes from the δ phase (orthogonal) to the γ phase (orthogonal), thereby obtaining a one-dimensional nanowire structure with uniform size distribution, thereby improving the photoelectric conversion ability. The preparation method does not require the addition of ligands, and the process is simple, does not require complex equipment, and is easy to scale up.

[0074] (2) The perovskite nanowire photocatalyst provided by the present invention has a one-dimensional nanowire structure and a uniform size distribution, exhibiting excellent photoelectric conversion ability and is widely used in the field of photocatalysis.

[0075] (3) The method for preparing benzaldehyde by alcohol oxidation provided by the present invention uses the above-mentioned perovskite nanowire photocatalyst, which takes into account both high conversion rate and high selectivity. For example, in the reaction of benzaldehyde oxidation to benzaldehyde, the conversion rate of benzyl alcohol is preferably increased to more than 99.8%, and the selectivity of benzaldehyde is preferably increased to more than 99.8%.

[0076] (4) The condensation method of aldehyde provided by the present invention uses the above-mentioned perovskite nanowire photocatalyst to achieve highly selective condensation of aldehyde. For example, in the condensation reaction of benzaldehyde, the conversion rate of benzaldehyde is preferably increased to more than 99.8%, and the selectivity of benzoin is preferably increased to more than 99.8%. Attached Figure Description

[0077] Figure 1 This is a SEM image of the perovskite nanowire photocatalyst precursor described in Example 1 of this invention.

[0078] Figure 2 This is a SEM image of the perovskite nanowire photocatalyst described in Example 1 of this invention.

[0079] Figure 3 The images show the XRD patterns of the perovskite nanowire photocatalyst precursor and the perovskite nanowire photocatalyst described in Example 1 of this invention.

[0080] Figure 4 This is the photoluminescence spectrum of the perovskite nanowire photocatalyst precursor and the perovskite nanowire photocatalyst described in Example 1 of the present invention.

[0081] Figure 5 This is the ultraviolet-visible absorption spectrum of the perovskite nanowire photocatalyst precursor and the perovskite nanowire photocatalyst described in Example 1 of this invention.

[0082] Figure 6This is a Tauc diagram of the perovskite nanowire photocatalyst precursor and the perovskite nanowire photocatalyst described in Example 1 of this invention.

[0083] Figure 7 This is the 1H NMR spectrum of the benzaldehyde product obtained in Application Example 1.1 of this invention.

[0084] Figure 8 This is the 1H NMR spectrum of benzoin, the benzaldehyde condensation product obtained in Application Example 1.2 of this invention.

[0085] Figure 9 This is the 1H NMR spectrum of benzoyl, the benzaldehyde condensation product obtained in Application Example 1.3 of this invention. Detailed Implementation

[0086] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0087] The substrates used in the following examples are all plasma-treated substrates.

[0088] In the following examples, deuterated DMSO was selected as the deuterated reagent for the proton NMR spectroscopy test.

[0089] I. Implementation Examples

[0090] Example 1

[0091] This embodiment provides a method for preparing a perovskite nanowire photocatalyst, the method comprising the following steps:

[0092] 15 μL of PbI₂ solution (1 mol / L, anhydrous DMF) was spin-coated onto a substrate (spin-coating speed 3000 r / min, spin-coating time 60 s), and then subjected to a first annealing at 130 °C for 20 min to obtain a substrate containing a PbI₂ layer. The substrate was then cooled to room temperature (25 °C), and then placed in a CsBr solution (4 mg / mL, anhydrous methanol) and allowed to stand at 25 °C for 24 h to obtain a perovskite nanowire photocatalyst precursor. This precursor was then subjected to a second annealing at 170 °C for 10 min to obtain the perovskite nanowire photocatalyst, namely perovskite CsPbBr. 2.961 I 0.039 Nanowire photocatalysts;

[0093] The mass ratio of PbI2 in the PbI2 layer to CsBr in the CsBr solution is 0.003:1.

[0094] This embodiment also provides a perovskite nanowire photocatalyst, which is prepared using the preparation method described in this embodiment and has the chemical formula CsPbBr. 2.961 I 0.039 Its microstructure is a nanowire structure with an aspect ratio of 20:1.

[0095] like Figure 1 and Figure 2 As shown, it can be seen that the microstructure of the perovskite nanowire photocatalyst precursor and the perovskite nanowire photocatalyst are consistent, both being nanowire structures, indicating that the microstructure of the perovskite nanowire photocatalyst precursor did not change before and after the phase transition.

[0096] like Figure 3 As shown, it can be seen that the XRD diffraction peaks of the perovskite nanowire photocatalyst precursor before the second annealing correspond one-to-one with the standard card (PDF#97-002-8312), and the XRD diffraction peaks of the perovskite nanowire photocatalyst after the second annealing correspond one-to-one with the standard card (PDF#97-009-7851), indicating that the perovskite CsPbBr 2.961 I 0.039 Nanowire photocatalysts have been successfully prepared.

[0097] like Figures 4 to 6 As shown, it can be seen that by transforming the δ-phase (orthorhombic) perovskite nanowire photocatalyst precursor into a γ-phase (orthorhombic) perovskite nanowire photocatalyst through the second annealing, the optical performance is significantly improved. Figure 4 It can be seen that the photoluminescence band of the perovskite nanowire photocatalyst precursor before the second annealing, i.e. before the phase change, is 500~800nm; and the photoluminescence band of the perovskite nanowire photocatalyst after the second annealing, i.e. after the phase change, is 510~560nm. Figure 5 It can be seen that the absorption edge of the perovskite nanowire photocatalyst precursor before the second annealing (i.e., before the phase transition) is around 430 nm, indicating weak light utilization; while the absorption edge of the perovskite nanowire photocatalyst after the second annealing (i.e., after the phase transition) is around 540 nm, indicating strong light utilization. Figure 6 It can be seen that the band gap of the perovskite nanowire photocatalyst precursor before the second annealing, i.e. before the phase change, is 2.9 eV; and the band gap of the perovskite nanowire photocatalyst after the second annealing, i.e. after the phase change, is 2.32 eV.

[0098] Example 2

[0099] This embodiment provides a method for preparing a perovskite nanowire photocatalyst, the method comprising the following steps:

[0100] 20 μL of PbI₂ solution (concentration 0.8 mol / L, solvent anhydrous DMF) was spin-coated onto a substrate (spin-coating speed 2500 r / min, spin-coating time 60 s), and subjected to a first annealing at 130℃ for 20 min to obtain a substrate containing a PbI₂ layer. The substrate was then cooled to room temperature (28℃), and placed in a CsBr solution (concentration 3 mg / mL, solvent anhydrous methanol) and allowed to stand at 35℃ for 30 h to obtain a perovskite nanowire photocatalyst precursor. This precursor was then subjected to a second annealing at 170℃ for 10 min to obtain the perovskite nanowire photocatalyst, namely perovskite CsPbBr. 2.928 I 0.072 Nanowire photocatalysts;

[0101] The mass ratio of PbI2 in the PbI2 layer to CsBr in the CsBr solution is 0.004:1.

[0102] This embodiment also provides a perovskite nanowire photocatalyst, which is prepared using the preparation method described in this embodiment and has the chemical formula CsPbBr. 2.928 I 0.072 Its microstructure is a nanowire structure with an aspect ratio of 25:1.

[0103] Example 3

[0104] This embodiment provides a method for preparing a perovskite nanowire photocatalyst, the method comprising the following steps:

[0105] 15 μL of PbI₂ solution (0.2 mol / L, DMF solvent) was drop-coated onto a substrate, and a first annealing was performed at 100 °C for 30 min to obtain a substrate containing a PbI₂ layer. The substrate was then cooled to room temperature (26 °C), and placed in a CsBr solution (6 mg / mL, methanol solvent) and allowed to stand at 30 °C for 16 h to obtain a perovskite nanowire photocatalyst precursor. This precursor was then subjected to a second annealing at 200 °C for 5 min to obtain the perovskite nanowire photocatalyst, namely perovskite CsPbBr. 2.880 I 0.120 Nanowire photocatalysts;

[0106] The mass ratio of PbI2 in the PbI2 layer to CsBr in the CsBr solution is 0.005:1.

[0107] This embodiment also provides a perovskite nanowire photocatalyst, which is prepared using the preparation method described in this embodiment and has the chemical formula CsPbBr. 2.880I 0.120 Its microstructure is a nanowire structure with an aspect ratio of 25:1.

[0108] Example 4

[0109] This embodiment provides a method for preparing a perovskite nanowire photocatalyst. The preparation method is the same as in Example 1, except that the mass ratio of PbI2 in the PbI2 layer to CsBr in the CsBr solution is 0.0001:1.

[0110] Example 5

[0111] This embodiment provides a method for preparing a perovskite nanowire photocatalyst. The preparation method is the same as in Example 1, except that the mass ratio of PbI2 in the PbI2 layer to CsBr in the CsBr solution is 0.015:1.

[0112] Example 6

[0113] This embodiment provides a method for preparing a perovskite nanowire photocatalyst. The preparation method is the same as in Example 1, except that the standing temperature is 15°C.

[0114] Example 7

[0115] This embodiment provides a method for preparing a perovskite nanowire photocatalyst. The preparation method is the same as in Example 1, except that the standing temperature is 40°C.

[0116] Example 8

[0117] This embodiment provides a method for preparing a perovskite nanowire photocatalyst. The preparation method is the same as in Example 1, except that the second annealing temperature is 130°C.

[0118] Example 9

[0119] This embodiment provides a method for preparing a perovskite nanowire photocatalyst. The preparation method is the same as in Example 1, except that the second annealing temperature is 350°C.

[0120] II. Comparative Example

[0121] Comparative Example 1

[0122] This comparative example provides a method for preparing a perovskite nanowire photocatalyst. The preparation method does not use a substrate, but directly mixes the PbI2 solution and the CsBr solution and allows them to stand. The rest of the method is the same as in Example 1.

[0123] The method described in this comparative example, which involves directly mixing the PbI2 solution and the CsBr solution and allowing them to stand, cannot produce perovskite materials.

[0124] III. Application Examples

[0125] Application Example 1.1

[0126] This application example provides a method for preparing benzaldehyde by the oxidation of benzyl alcohol. The method uses the perovskite CsPbBr4 described in Example 1. 2.961 I 0.039 The nanowire photocatalyst process includes the following steps:

[0127] Mix 10 mL of benzyl alcohol solution (concentration 5 μmol / mL, solvent acetonitrile) and 5 mg of the perovskite CsPbBr 2.961 I 0.039 The nanowire photocatalyst was used, and the first catalytic reaction was carried out by irradiation with a 405nm LED light source for 1 hour to obtain a mixed solution containing benzaldehyde. The mixed solution containing benzaldehyde was then centrifuged at 8000 r / min for 3 minutes. The organic phase was collected and subjected to a first rotary evaporation at 50°C for 5 minutes to obtain the benzaldehyde product.

[0128] like Figure 7 The image shows the 1H NMR spectrum of the benzaldehyde product obtained in this application example. It can be seen that the characteristic peak of benzaldehyde appears in the 1H NMR spectrum, and there are no characteristic peaks of other substances besides benzyl alcohol and benzaldehyde. In addition, the characteristic peak intensity of benzaldehyde is very high, indicating that the raw material benzyl alcohol is about to be completely converted into benzaldehyde.

[0129] Application Example 1.2

[0130] This application example provides a condensation method for benzaldehyde, wherein the condensation method uses the perovskite CsPbBr4 described in Example 1. 2.961 I 0.039 The nanowire photocatalyst process includes the following steps:

[0131] Mix 10 mL of benzaldehyde solution (concentration 10 μmol / mL, solvent acetonitrile) and the perovskite CsPbBr 2.961 I 0.039 The nanowire photocatalyst was used, and a second catalytic reaction was carried out by irradiation with a 405nm LED light source for 10 min to obtain a mixed solution containing benzoin. The mixed solution containing benzoin was then centrifuged for a second time at 7000 r / min for 4 min. The organic phase was collected and then rotary evaporated at 60℃ for a second time for 8 min to obtain benzoin.

[0132] like Figure 8The image shows the 1H NMR spectrum of benzoin, the benzaldehyde condensation product obtained in this application example. It can be seen that the characteristic peak of benzaldehyde has disappeared in the 1H NMR spectrum, indicating that benzaldehyde has been almost completely converted. In addition, the peak position and peak shape in the 1H NMR spectrum are consistent with the peak characteristics of benzoin, indicating that benzaldehyde has been almost completely converted into benzoin.

[0133] Application Example 1.3

[0134] The benzaldehyde condensation method provided in this application example is the same as that in Application Example 1.2, except that the second catalytic reaction is carried out by irradiating with a 405nm LED light source for 60 minutes.

[0135] like Figure 9 The figure shows the 1H NMR spectrum of benzoyl obtained in this application example. It can be seen that the characteristic peak of benzaldehyde has disappeared in the 1H NMR spectrum, indicating that benzaldehyde has been completely converted. In addition, as can be seen from Application Example 1.2, benzaldehyde will first be converted into benzoin. However, no benzoin NMR peak appears in the 1H NMR spectrum, and the peak position and peak shape in the 1H NMR spectrum are consistent with the peak characteristics of benzoyl, indicating that benzaldehyde has been completely converted into benzoin and further oxidized to benzoyl.

[0136] Application Example 2.1

[0137] This application example provides a method for preparing benzaldehyde by oxidation of benzyl alcohol. The method uses the perovskite CsPbBr4 described in Example 2. 2.928 I 0.072 The nanowire photocatalyst process includes the following steps:

[0138] Mix 5 mL of benzyl alcohol solution (concentration 10 μmol / mL, solvent acetonitrile) and 5 mg of the perovskite CsPbBr 2.928 I 0.072 The nanowire photocatalyst was used, and the first catalytic reaction was carried out by irradiation with a 405nm LED light source for 1 hour to obtain a mixed solution containing benzaldehyde. The mixed solution containing benzaldehyde was then centrifuged at 6000 r / min for 5 min, the organic phase was collected, and the mixture was rotary evaporated at 40℃ for 10 min to obtain the benzaldehyde product.

[0139] Application Example 2.2

[0140] This application example provides a condensation method for benzaldehyde, wherein the condensation method uses the perovskite CsPbBr4 described in Example 2. 2.928 I 0.072 The nanowire photocatalyst process includes the following steps:

[0141] Mix 5 mL of benzaldehyde solution (concentration 15 μmol / mL, solvent acetonitrile) and 10 mg of the perovskite CsPbBr 2.928 I 0.072 The nanowire photocatalyst was used, and a second catalytic reaction was carried out by irradiation with a 405nm LED light source for 10 min to obtain a mixed solution containing benzoin. The mixed solution containing benzaldehyde condensation product was then centrifuged for 5 min at a speed of 5000 r / min. The organic phase was collected and then rotary evaporated at 50℃ for 6 min to obtain the benzaldehyde condensation product.

[0142] Application Examples 3.1 to 9.1

[0143] The methods for preparing benzaldehyde by oxidation of benzyl alcohol provided in Application Examples 3.1 to 9.1 are the same as those in Application Example 1.1, except that they use the perovskite nanowire photocatalysts provided in Examples 3 to 9 respectively.

[0144] Application Examples 3.2 to 9.2

[0145] The condensation methods for benzaldehyde provided in Application Examples 3.2 to 9.2 are the same as those in Application Example 1.2, except that they use the perovskite nanowire photocatalysts provided in Examples 3 to 9 respectively.

[0146] IV. Comparative Application Examples

[0147] Comparative application example 1.1

[0148] This comparative application example provides a method for preparing benzaldehyde by oxidation of benzyl alcohol. Except for the use of the perovskite nanowire photocatalyst provided in Comparative Example 1, the method is the same as that in Application Example 1.1.

[0149] Compare and contrast with example 1.2

[0150] This comparative application example provides a condensation method for benzaldehyde, which is the same as that in application example 1.2 except that the perovskite nanowire photocatalyst provided in comparative example 1 is used.

[0151] V. Tests and Results

[0152] ① The conversion rate of benzyl alcohol and the selectivity of benzaldehyde in Application Examples 1.1 to 8.1 and Comparative Application Example 1.1 were tested and calculated (reaction at 25℃ for 60 min). The results are shown in Table 1.

[0153] Table 1

[0154]

[0155] Note: "-" in Table 1 indicates that there is no relevant data.

[0156] ② The conversion rate of benzaldehyde and the selectivity of benzoin in the above application examples 1.2 to 9.2 and the comparison application example 1.2 were tested and calculated (reaction at 25℃ for 10 min). The results are shown in Table 2.

[0157] Table 2

[0158]

[0159] Note: "-" in Table 2 indicates that there is no relevant data.

[0160] The data in Table 1 and Table 2 show that:

[0161] (1) As can be seen from the combined application examples 1.1 to 3.1 and 1.2 to 3.2, the perovskite nanowire photocatalysts prepared by the preparation methods described in Examples 1 to 3 of the present invention exhibit excellent catalytic activity and selectivity in the reaction of benzyl alcohol oxidation to benzaldehyde, with a conversion rate of benzyl alcohol of up to 99.8% and a selectivity of benzaldehyde of up to 99.8%; they also exhibit excellent catalytic activity in the condensation reaction of benzaldehyde, with a conversion rate of benzaldehyde of up to 99.8% and a selectivity of the target product of up to 99.8%.

[0162] (2) Combining Application Examples 1.1 and 4.1 to 9.1, and Application Examples 1.2 and 4.2 to 9.2, it can be seen that the preparation method of the present invention can further improve the photoelectric conversion capability of the obtained perovskite nanowire photocatalyst by further optimizing the mass ratio of PbM2 in the Pb precursor layer to CsX in the CsX solution to (0.001 to 0.01):1, or further optimizing the standing temperature to 20 to 35°C, or further optimizing the second annealing temperature to 150 to 200°C, thereby further improving the catalytic activity and selectivity in the oxidation of benzyl alcohol to benzaldehyde and the benzaldehyde condensation reaction.

[0163] (3) Combining Application Example 1.1 with Comparative Application Example 1.1, and Application Example 1.2 with Comparative Application Example 1.2, it can be seen that since the preparation method described in Comparative Example 1 cannot prepare perovskite nanowire catalyst materials, it cannot catalyze the oxidation of benzyl alcohol to benzaldehyde and the condensation reaction of benzaldehyde.

[0164] In summary, this invention first prepares a δ-phase (orthorhombic) perovskite nanowire photocatalyst precursor by solution method, and then transforms it into a γ-phase (orthorhombic) perovskite nanowire photocatalyst through a second annealing process, thereby improving the photoelectric conversion capability. It exhibits excellent photocatalytic activity and selectivity in the reaction of benzyl alcohol oxidation to benzaldehyde and the condensation reaction of benzaldehyde.

[0165] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a perovskite nanowire photocatalyst, characterized in that, The preparation method includes the following steps: A Pb precursor solution is coated onto a substrate and subjected to a first annealing to obtain a substrate containing a Pb precursor layer. The substrate containing the Pb precursor layer is then placed in a CsX solution and allowed to stand to obtain a perovskite CsPbX3 nanowire photocatalyst precursor. The perovskite CsPbX3 nanowire photocatalyst precursor is then subjected to a second annealing to obtain a perovskite CsPbX3 nanowire photocatalyst. In the CsX solution, X includes Cl. - ,Br - Or I - Any one or at least two of them.

2. The preparation method according to claim 1, characterized in that, The Pb precursor solution contains PbM2 as the Pb precursor, where M includes Cl. - ,Br - I - or CH3COO - Any one or at least two of them; Preferably, the concentration of the Pb precursor solution is 0.1~2 mol / L, more preferably 0.1~1 mol / L; Preferably, the concentration of the CsX solution is 2~16 mg / mL, more preferably 3~6 mg / mL; Preferably, the mass ratio of PbM2 in the Pb precursor layer to CsX in the CsX solution is (0.001~0.01):

1.

3. The preparation method according to claim 1 or 2, characterized in that, The coating method includes spin coating and / or drop coating, preferably spin coating; Preferably, the spin coating speed is 2000~4000 r / min; Preferably, the spin coating time is 30-60 seconds; Preferably, the temperature of the first annealing is 50~150℃, more preferably 100~150℃; Preferably, the first annealing time is 5~30 min; Preferably, the preparation method further includes plasma treatment of the substrate before coating.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The temperature for static setting is 0~100℃, preferably 20~35℃; Preferably, the settling time is 1~48h, more preferably 4~24h; Preferably, the temperature of the second annealing is 100~300℃, more preferably 150~200℃; Preferably, the second annealing time is 1~20 min, more preferably 5~10 min.

5. A perovskite nanowire photocatalyst, characterized as follows: The perovskite nanowire photocatalyst is prepared using the preparation method of the perovskite nanowire photocatalyst according to any one of claims 1 to 4.

6. The perovskite nanowire photocatalyst according to claim 5, characterized in that, The perovskite nanowire photocatalyst has the chemical formula CsPbX3, wherein X includes Cl. - ,Br - Or I - Any one or at least two of them; Preferably, the crystal structure of the perovskite nanowire photocatalyst includes a γ phase; Preferably, the aspect ratio of the nanowire structure in the perovskite nanowire photocatalyst is (15~40):

1.

7. A method for preparing aldehydes by alcohol oxidation, characterized in that, The method is carried out using the perovskite nanowire photocatalyst described in claim 5 or 6.

8. The method according to claim 7, characterized in that, The method includes the following steps: The mixed alcohol solution and the perovskite nanowire photocatalyst undergo a first catalytic reaction, followed by a first separation to obtain the corresponding aldehyde product; Preferably, the alcohol in the alcohol solution includes aromatic alcohols and / or fatty alcohols; Preferably, the aromatic alcohol comprises benzyl alcohol and / or p-methylbenzyl alcohol; Preferably, the fatty alcohol includes n-hexanol; Preferably, the solvent in the alcohol solution includes any one or a combination of at least two of toluene, cyclohexane, acetonitrile, methanol, or ethanol, with acetonitrile being the most preferred. Preferably, the concentration of the alcohol solution is 3~10 μmol / mL; Preferably, the amount of the perovskite nanowire photocatalyst is 0.1~20 mg / mL; Preferably, the light source used in the first catalytic reaction includes ultraviolet light and / or visible light; Preferably, the first catalytic reaction takes 0.1 to 2 hours.

9. A method for the condensation of an aldehyde, characterized in that, The condensation method is carried out using the perovskite nanowire photocatalyst described in claim 5 or 6.

10. The condensation method according to claim 9, characterized in that, The shrinkage method includes the following steps: The mixed aldehyde solution and the perovskite nanowire photocatalyst undergo a second catalytic reaction, followed by a second separation to obtain the corresponding aldehyde condensation product; Preferably, the aldehydes in the aldehyde solution include aromatic aldehydes and / or aliphatic aldehydes; Preferably, the aromatic aldehyde includes benzaldehyde and / or p-methylbenzaldehyde; Preferably, the fatty aldehyde includes n-pentanal; Preferably, the solvent in the aldehyde solution includes any one or a combination of at least two of toluene, cyclohexane, acetonitrile, methanol, or ethanol, with acetonitrile being the preferred solvent. Preferably, the concentration of the aldehyde solution is 5~15 μmol / mL; Preferably, the amount of the perovskite nanowire photocatalyst is 0.1~20 mg / mL; Preferably, the light source for the second catalytic reaction includes ultraviolet light and / or visible light; Preferably, the second catalytic reaction takes 5 to 60 minutes.

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