A kind of Bi 25 FeO 40 Piezoelectric catalyst and its preparation method and application

Abstract

The present invention provides a Bi 25 FeO 40 A piezoelectric catalyst and its preparation method and application, the preparation method comprising the following steps: step 1: dissolving a bismuth source and an iron source in ethylene glycol at a molar ratio of 1:1, and then adding water to form a precursor solution; step 2: adjusting the pH value of the precursor solution to 9-11 with NH3·H2O under stirring, precipitating a precipitate, and washing and drying the precipitate in sequence; step 3: mixing the precipitate with a NaOH solution, performing a hydrothermal reaction, and after the reaction is completed, washing and drying in sequence to obtain Bi 25 FeO 40 Piezoelectric catalyst. The Bi obtained by the preparation method 25 FeO 40 Piezoelectric catalysts have enhanced piezoelectric polarization properties and have a strong ability to degrade pollutants under dark conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of piezoelectric catalytic material preparation, specifically a Bi 25 FeO 40 Piezoelectric catalyst, preparation method and application thereof. Background Art

[0002] Photocatalysts can harness the photogenerated charges from solar energy to form active free radicals that initiate catalytic reactions, potentially combating environmental pollution. However, photocatalytic reactions can only occur in areas with abundant daylight, not in the dark. Piezoelectric catalysts with energy storage properties, strong polarization electric field strength, and defects such as variable-valence ions and oxygen vacancies can utilize mechanical forces to release stored electrons and holes and generate piezoelectric charges in the dark, potentially enabling efficient dark-catalytic reactions.

[0003] Bi 25 FeO 40 As a common bismuth ferrite-based catalyst, the special spin characteristics of the Fe atoms in its structure lead to its weak piezoelectric effect. However, the weak polarization electric field strength makes its own stored charge concentration low and the generated piezoelectric charge small, thus showing weak dark catalytic performance. Chinese patent CN111185184B discloses that a bismuth source and an iron source are dissolved in ethylene glycol, and then titrated with KOH to prepare a bismuth ferrite catalyst with visible light degradation performance. 25 FeO 40 Due to the uniform complexation of ethylene glycol, it has no ability to degrade methylene blue water pollutants under dark conditions. The literature (Chemical Engineering Journal 429 (2022) 132130) discloses that 4 μm cubic structure Bi was prepared by hydrothermal method using nitric acid as solvent and KOH as mineralizer. 25 FeO 40 , tetracycline is degraded under visible light, but nitric acid prevents the hydrolysis of nitrates and cannot form variable valence ions, resulting in its inability to degrade under dark conditions. Chinese patent CN 110975874BA discloses that a bismuth source and an iron source are dissolved in water, then added dropwise to ethanol containing a surfactant, and KOH solution is added dropwise to prepare a Fe-containing ion through a hydrothermal reaction. 3+ / Fe 2+ A rod-shaped Bi2O3 assembled from nanoparticles of variable valence ions 25 FeO 40, has the performance of visible light-Fenton degradation of tetracycline, but the degradation performance is weak under dark conditions. Chinese patents CN102101700B and CN102091632A reported that ethylene glycol was used as solvent, and after the iron source and bismuth source were dissolved, a mother salt solution was obtained. The precursor was obtained by titration with ammonia water, washing and aging. The microwave hydrothermal method was used to prepare Bi with a porous cubic structure of about 10 μm. 25 FeO 40 -BiFeO3 powder and Bi with a flake structure of about 10 nm 25 FeO 40 The powder has no defects such as variable valence ions or oxygen vacancies due to the uniform complexation of ethylene glycol, which makes it unable to degrade pollutants under dark conditions. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides a Bi 25 FeO 40 Piezoelectric catalyst and its preparation method and application, Bi obtained by the preparation method 25 FeO 40 Piezoelectric catalysts have enhanced piezoelectric polarization properties and have a strong ability to degrade pollutants under dark conditions.

[0005] The present invention is achieved through the following technical solutions:

[0006] A kind of Bi 25 FeO 40 The preparation method of the piezoelectric catalyst comprises the following steps:

[0007] Step 1: Dissolve the bismuth source and the iron source in ethylene glycol at a molar ratio of 1:1, and then add water to form a precursor solution;

[0008] Step 2: Under stirring, adjust the pH value of the precursor solution to 9-11 with NH3·H2O to precipitate, and wash and dry the precipitate in sequence;

[0009] Step 3: Mix the precipitate with NaOH solution and conduct hydrothermal reaction. After the reaction is completed, wash and dry in sequence to obtain Bi 25 FeO 40 Piezoelectric catalyst.

[0010] Preferably, in step 1, the iron source is Fe(NO3)3·6H2O or FeCl3·6H2O.

[0011] Preferably, in step 1, the bismuth source is Bi(NO3)3·5H2O or BiCl3·6H2O.

[0012] Preferably, in step 1, the total concentration of the iron source and the bismuth source in ethylene glycol is 0.04-0.4 mol / L.

[0013] Preferably, in step 1, the volume ratio of ethylene glycol to water is 50:(40-90).

[0014] Preferably, in step 3, the concentration of the added NaOH solution is 6-10 mol / L.

[0015] Preferably, in step 3, the hydrothermal reaction temperature is 120-160° C., and the hydrothermal reaction time is 8-20 h.

[0016] The present invention provides Bi obtained by the preparation method 25 FeO 40 Piezoelectric catalyst, the Bi 25 FeO 40 The piezoelectric catalyst has a bismuthite structure, a cubic crystal system, a 123 space group, and a microscopic morphology composed of square nanosheets and nanoparticles.

[0017] The present invention provides the Bi 25 FeO 40 Application of piezoelectric catalysts in catalytic degradation of organic pollutants.

[0018] Preferably, the catalytic degradation of organic pollutants is carried out in the dark.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention dissolves the iron source and the bismuth source in ethylene glycol, adds a certain amount of water, and hydrolyzes part of the ethylene glycol to produce acetaldehyde and ethanol, forming Bi in the solution. 3+ and Fe 3+ Complexation with ethylene glycol and Bi 3+ and Fe 3+ The two complex systems are complexed with ethanol, and the two complex systems polymerize to form an uneven coordination system, which is hydrothermally crystallized to form Bi 3+ and Fe 3+ Square nanosheet structure and Bi complex system with ethylene glycol 3+ and Fe 3+ The nanoparticle structure of the complex with ethanol has different crystallization rates due to the uneven coordination system, forming a Bi 3+ / Bi 5+ 、Fe 2+ / Fe 3+ Bi with variable valence ions and oxygen vacancies 25 FeO 40 , making Bi 25 FeO 40The electrons and holes are stored, and the coexistence of the electrons and holes leads to the formation of a polarized electric field. The present invention utilizes the different crystallization rates caused by the uneven coordination system to make the Bi prepared by the present invention 25 FeO 40 It has strong piezoelectric properties and can release stored electrons and holes under mechanical stress in dark conditions to degrade and mineralize organic pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 Bi prepared in Examples 1-6 of the present invention 25 FeO 40 XRD pattern of .

[0023] Figure 2 The Bi prepared in Example 3 of the present invention 25 FeO 40 SEM image of .

[0024] Figure 3 The Bi prepared in Example 3 of the present invention 25 FeO 40 TEM image of.

[0025] Figure 4 The Bi prepared in Example 3 of the present invention 25 FeO 40 HRTEM image of.

[0026] Figure 5 Bi prepared in Examples 1-4 of the present invention 25 FeO 40 O 1s high-resolution XPS pattern.

[0027] Figure 6 Bi prepared in Examples 1-4 of the present invention 25 FeO 40 Fe 2p high-resolution XPS pattern.

[0028] Figure 7 Bi prepared in Examples 1-4 of the present invention 25 FeO 40 Bi 4f high-resolution XPS pattern.

[0029] Figure 8Bi prepared in Examples 1-6 of the present invention 25 FeO 40 Piezoelectric current diagram generated by eddy current shear force.

[0030] Figure 9 The Bi prepared in Example 1 of the present invention 25 FeO 40 Phase change diagram.

[0031] Figure 10 The Bi prepared in Example 2 of the present invention 25 FeO 40 Phase change diagram.

[0032] Figure 11 The Bi prepared in Example 3 of the present invention 25 FeO 40 Phase change diagram.

[0033] Figure 12 The Bi prepared in Example 4 of the present invention 25 FeO 40 Phase change diagram.

[0034] Figure 13 The Bi prepared in Example 1 of the present invention 25 FeO 40 Amplitude variation diagram.

[0035] Figure 14 The Bi prepared in Example 2 of the present invention 25 FeO 40 Amplitude variation diagram.

[0036] Figure 15 The Bi prepared in Example 3 of the present invention 25 FeO 40 Amplitude variation diagram.

[0037] Figure 16 The Bi prepared in Example 4 of the present invention 25 FeO 40 Amplitude variation diagram.

[0038] Figure 17 The Bi prepared in Example 3 of the present invention 25 FeO 40 Absorbance curve of 20 mg / L methylene blue in dark conditions.

[0039] Figure 18 The Bi prepared in Example 3 of the present invention 25 FeO 40 EPR pattern of holes under dark conditions.

[0040] Figure 19 Bi prepared in Examples 1-6 of the present invention 25 FeO 40 Degradation curve of 20 mg / L tetracycline under dark conditions.

[0041] Figure 20 The Bi obtained in Example 3 of the present invention is prepared 25 FeO 40 TOC removal efficiency of 40 mg / L tetracycline under dark conditions.

[0042] Figure 21 The Bi prepared in Example 3 of the present invention 25 FeO 40 Cyclic degradation of 20 mg / L tetracycline under dark conditions.

[0043] Figure 22 The Bi prepared in Example 3 of the present invention 25 FeO 40 Figure 4. Active species capture under dark conditions.

[0044] Figure 23 The Bi obtained in Example 3 of the present invention is prepared 25 FeO 40 LC-MS spectrum of the reaction solution after degrading 20 mg / L tetracycline for 5 min under dark conditions.

[0045] Figure 24 The Bi obtained in Example 3 of the present invention is prepared 25 FeO 40 LC-MS spectrum of the reaction solution after degradation of 20 mg / L tetracycline in dark conditions for 30 min.

[0046] Figure 25 The Bi obtained in Example 3 of the present invention is prepared 25 FeO 40 Absorbance changes of the degradation of a mixed solution of 20 mg / L ciprofloxacin, 10 mg / L rhodamine B, 20 mg / L methylene blue, 10 mg / L methylene orange, and 20 mg / L tetracycline in the dark. DETAILED DESCRIPTION

[0047] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0048] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0049] It should be noted that the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise specified, the numbering of each method step is merely a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the invention. Changes or adjustments to their relative relationships, without substantially changing the technical content, should also be considered within the scope of the invention.

[0050] The Bi of the present invention 25 FeO 40 The preparation method of the piezoelectric catalyst comprises the following steps:

[0051] Step 1: Dissolve the bismuth source and the iron source in ethylene glycol at a molar ratio of 1:1. After complete dissolution, add water to form a precursor solution.

[0052] Step 2: Under stirring, adjust the pH value of the precursor solution to 9-11 with NH3·H2O to quickly produce a precipitate, and then wash and dry the precipitate in sequence;

[0053] Step 3: Mix the above precipitate with NaOH solution and conduct hydrothermal reaction. After the reaction is completed, wash and dry in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0054] In the present invention, the iron source is preferably Fe(NO3)3·6H2O or FeCl3·6H2O. The bismuth source is preferably Bi(NO3)3·5H2O or BiCl3·6H2O.

[0055] In step 1 of the present invention, the total concentration of the iron source and the bismuth source in the ethylene glycol is 0.04-0.4 mol / L. The volume ratio of the added ethylene glycol to water is 50:(40-90).

[0056] In step 3 of the present invention, the concentration of the added NaOH solution is 6-10 mol / L, the hydrothermal reaction temperature is 120-160° C., and the hydrothermal reaction time is 8-20 h.

[0057] The Bi prepared by the present invention 25 FeO 40It has a soft bismuth mineral structure, cubic crystal system, 123 space group, and its microscopic morphology is composed of square nanosheets and nanoparticles. It has piezoelectric properties and can store electrons and holes at the same time. 25 FeO 40 , d 33 The value is 1.25 ~7.43 nm·V -1 , the largest d 33 The value is 7.43 nm / V, and the maximum concentrations of stored electrons and holes are 13.18 μmol·g -1 and 129.15 μmol·g -1 .

[0058] The Bi prepared by the present invention 25 FeO 40 In dark conditions 25 FeO 40 Mechanical strain occurs to release stored electron holes and generate piezoelectric charges, which have a good degradation effect on antibiotics and mixed pollutants and have good cycle stability.

[0059] Preferably, the antibiotic is tetracycline. The mixed pollutant is a mixed pollutant of tetracycline, ciprofloxacin, methylene blue, rhodamine B and methylene orange.

[0060] Example 1

[0061] Step 1: Dissolve Fe(NO3)3·6H2O and Bi(NO3)3·5H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.06 mol / L. After complete dissolution, add 90 mL of deionized water to form a precursor solution.

[0062] Step 2: Under stirring, adjust the pH value of the precursor solution to 10 with NH3·H2O to quickly produce a precipitate, and then wash and dry the precipitate in sequence;

[0063] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 6 mol / L NaOH solution was added and kept at 160 °C for 20 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0064] Example 2

[0065] Step 1: Dissolve Fe(NO3)3·6H2O and Bi(NO3)3·5H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.08 mol / L. After complete dissolution, add 90 mL of deionized water to form a precursor solution.

[0066] Step 2: Under stirring, adjust the pH value of the precursor solution to 10 by adding NH3·H2O to quickly generate a precipitate, and then wash and dry the precipitate in turn;

[0067] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 6 mol / L NaOH solution was added and kept at 160 ° C for 20 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0068] Example 3

[0069] Step 1: Dissolve Fe(NO3)3·6H2O and Bi(NO3)3·5H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.1 mol / L. After complete dissolution, add 90 mL of deionized water to form a precursor solution.

[0070] Step 2: Under stirring, adjust the pH value of the precursor solution to 10 with NH3·H2O to quickly produce a precipitate, and then wash and dry the precipitate in sequence;

[0071] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 6 mol / L NaOH solution was added and kept at 160 °C for 20 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0072] Example 4

[0073] Step 1: Dissolve Fe(NO3)3·6H2O and Bi(NO3)3·5H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.2 mol / L. After complete dissolution, add 90 mL of deionized water to form a precursor solution.

[0074] Step 2: Under stirring, adjust the pH value of the precursor solution to 10 with NH3·H2O to quickly produce a precipitate, and then wash and dry the precipitate in sequence;

[0075] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 6 mol / L NaOH solution was added and kept at 160 °C for 20 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0076] Example 5

[0077] Step 1: Dissolve Fe(NO3)3·6H2O and Bi(NO3)3·5H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.3 mol / L. After complete dissolution, add 90 mL of deionized water to form a precursor solution.

[0078] Step 2: Under stirring, adjust the pH value of the precursor solution to 10 with NH3·H2O to quickly produce a precipitate, and then wash and dry the precipitate in sequence;

[0079] Step 3: The precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 6 mol / L NaOH solution was added and kept at 160 °C for 20 h. After the reaction was completed, the precipitate was washed and dried in sequence to obtain Bi 25 FeO 40 Piezoelectric catalyst.

[0080] Example 6

[0081] Step 1: Dissolve Fe(NO3)3·6H2O and Bi(NO3)3·5H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.4 mol / L. After complete dissolution, add 90 mL of deionized water to form a precursor solution.

[0082] Step 2: Under stirring, adjust the pH value of the precursor solution to 10 with NH3·H2O to quickly produce a precipitate, and then wash and dry the precipitate in sequence;

[0083] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 6 mol / L NaOH solution was added and kept at 160 °C for 20 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0084] Example 7

[0085] Step 1: Dissolve Fe(NO3)3·6H2O and Bi(NO3)3·5H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.06 mol / L. After complete dissolution, add 60 mL of deionized water to form a precursor solution.

[0086] Step 2: Under stirring, the pH value of the precursor solution is adjusted to 9 by adding NH3·H2O to quickly generate a precipitate, which is then washed and dried in turn;

[0087] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 6 mol / L NaOH solution was added and kept at 160 °C for 20 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0088] Example 8

[0089] Step 1: Dissolve FeCl3·6H2O and Bi(NO3)3·5H2O in a 1:1 molar ratio at a concentration of 0.04 mol / L in 50 mL of ethylene glycol. After complete dissolution, add 80 mL of deionized water to form a precursor solution.

[0090] Step 2: Under stirring, adjust the pH value of the precursor solution to 10.2 by adding NH3·H2O to quickly generate a precipitate, and then wash and dry the precipitate in turn;

[0091] Step 3: The precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 8 mol / L NaOH solution was added and kept at 120 °C for 8 h. After the reaction was completed, the precipitate was washed and dried in sequence to obtain Bi 25 FeO 40 Piezoelectric catalyst.

[0092] Example 9

[0093] Step 1: Dissolve FeCl3·6H2O and BiCl3·6H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.15 mol / L. After complete dissolution, add 70 mL of deionized water to form a precursor solution.

[0094] Step 2: Under stirring, adjust the pH value of the precursor solution to 10.3 by adding NH3·H2O to quickly generate a precipitate, and then wash and dry the precipitate in sequence;

[0095] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 8 mol / L NaOH solution was added and kept at 160 °C for 10 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0096] Example 10

[0097] Step 1: Dissolve FeCl3·6H2O and BiCl3·6H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.08 mol / L. After complete dissolution, add 70 mL of deionized water to form a precursor solution.

[0098] Step 2: Under stirring, adjust the pH value of the precursor solution to 9.5 by adding NH3·H2O to quickly generate a precipitate, and then wash and dry the precipitate in sequence;

[0099] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 7 mol / L NaOH solution was added and kept at 150 °C for 12 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0100] Example 11

[0101] Step 1: Dissolve FeCl3·6H2O and BiCl3·6H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.07 mol / L. After complete dissolution, add 70 mL of deionized water to form a precursor solution.

[0102] Step 2: Under stirring, the pH value of the precursor solution is adjusted to 10.8 by adding NH3·H2O to quickly generate a precipitate, which is then washed and dried in sequence;

[0103] Step 3: The precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 9 mol / L NaOH solution was added and kept at 130 °C for 9 h. After the reaction was completed, the precipitate was washed and dried in sequence to obtain Bi 25 FeO 40 Piezoelectric catalyst.

[0104] Example 12

[0105] Step 1: Dissolve FeCl3·6H2O and Bi(NO3)3·5H2O in a 1:1 molar ratio at a concentration of 0.25 mol / L in 50 mL of ethylene glycol. After complete dissolution, add 70 mL of deionized water to form a precursor solution.

[0106] Step 2: Under stirring, adjust the pH value of the precursor solution to 9.8 by adding NH3·H2O to quickly generate a precipitate, and then wash and dry the precipitate in sequence;

[0107] Step 3: The precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 7 mol / L NaOH solution was added and kept at 130 °C for 8 h. After the reaction was completed, the precipitate was washed and dried in sequence to obtain Bi 25 FeO 40 Piezoelectric catalyst.

[0108] Example 13

[0109] Step 1: Dissolve Fe(NO3)3·6H2O and BiCl3·6H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.09 mol / L. After complete dissolution, add 50 mL of deionized water to form a precursor solution.

[0110] Step 2: Under stirring, adjust the pH value of the precursor solution to 9.5 by adding NH3·H2O to quickly generate a precipitate, and then wash and dry the precipitate in sequence;

[0111] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 8 mol / L NaOH solution was added and kept at 140 °C for 11 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0112] Example 14

[0113] Step 1: Dissolve Fe(NO3)3·6H2O and BiCl3·6H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.08 mol / L. After complete dissolution, add 30 mL of deionized water to form a precursor solution.

[0114] Step 2: Under stirring, adjust the pH value of the precursor solution to 10.3 by adding NH3·H2O to quickly generate a precipitate, and then wash and dry the precipitate in turn;

[0115] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 7.5 mol / L NaOH solution was added and kept at 145 °C for 15 h. After the reaction was completed, Bi was washed and dried in sequence. 25 FeO 40 Piezoelectric catalyst.

[0116] Example 15

[0117] Step 1: Dissolve FeCl3·6H2O and Bi(NO3)3·5H2O in a 1:1 molar ratio at a concentration of 0.07 mol / L in 50 mL of ethylene glycol. After complete dissolution, add 80 mL of deionized water to form a precursor solution.

[0118] Step 2: Under stirring, adjust the pH value of the precursor solution to 11 by adding NH3·H2O to quickly generate a precipitate, and then wash and dry the precipitate in sequence;

[0119] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 9 mol / L NaOH solution was added and kept at 120 °C for 8 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0120] Example 16

[0121] Step 1: Dissolve Fe(NO3)3·6H2O and BiCl3·6H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.08 mol / L. After complete dissolution, add 50 mL of deionized water to form a precursor solution.

[0122] Step 2: Under stirring, adjust the pH value of the precursor solution to 10.3 by adding NH3·H2O to quickly generate a precipitate, and then wash and dry the precipitate in sequence;

[0123] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 9 mol / L NaOH solution was added and kept at 150 °C for 20 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0124] Example 17

[0125] Step 1: Dissolve Fe(NO3)3·6H2O and BiCl3·6H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.09 mol / L. After complete dissolution, add 60 mL of deionized water to form a precursor solution.

[0126] Step 2: Under stirring, adjust the pH value of the precursor solution to 9.6 by adding NH3·H2O to quickly generate a precipitate, and then wash and dry the precipitate in sequence;

[0127] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 9 mol / L NaOH solution was added and kept at 120 °C for 8 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0128] Example 18

[0129] Step 1: Dissolve FeCl3·6H2O and Bi(NO3)3·5H2O in a 1:1 molar ratio at a concentration of 0.4 mol / L in 50 mL of ethylene glycol. After complete dissolution, add 60 mL of deionized water to form a precursor solution.

[0130] Step 2: Under stirring, adjust the pH value of the precursor solution to 9.5 by adding NH3·H2O to quickly generate a precipitate, and then wash and dry the precipitate in sequence;

[0131] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 7 mol / L NaOH solution was added and kept at 160 °C for 8 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0132] Example 19

[0133] Step 1: Dissolve Fe(NO3)3·6H2O and BiCl3·6H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.05 mol / L. After complete dissolution, add 40 mL of deionized water to form a precursor solution.

[0134] Step 2: Under stirring, adjust the pH value of the precursor solution to 9 by adding NH3·H2O to quickly generate a precipitate, and then wash and dry the precipitate in sequence;

[0135] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 6 mol / L NaOH solution was added and kept at 120 °C for 8 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0136] Example 20

[0137] Step 1: Dissolve Fe(NO3)3·6H2O and Bi(NO3)3·5H2O in 50 mL of ethylene glycol at a molar ratio of 1:1 and a concentration of 0.08 mol / L. After complete dissolution, add 70 mL of deionized water to form a precursor solution.

[0138] Step 2: Under stirring, the pH value of the precursor solution is adjusted to 10.5 by adding NH3·H2O to quickly generate a precipitate, which is then washed and dried in turn;

[0139] Step 3: The above precipitate was transferred to a polytetrafluoroethylene reactor, and 40 ml of 8 mol / L NaOH solution was added and kept at 160 °C for 15 h. After the reaction was completed, it was washed and dried in sequence to prepare Bi 25 FeO 40 Piezoelectric catalyst.

[0140] The above conclusions and mechanisms are explained in detail below.

[0141] Figure 1 Bi prepared in Examples 1, 2, 3, 4, 5 and 6 of the present invention 25 FeO 40 The XRD pattern of the piezoelectric catalyst shows that the strong diffraction peaks at 2θ=24.7°, 27.6°, 30.4° and 32.9° correspond to Bi 25 FeO 40 (PDF#46-0416) has (220), (310), (222) and (321) crystal planes, indicating that the sample prepared in the present invention is Bi2O3 with a soft bismuthite structure. 25 FeO 40 , belongs to the cubic crystal system and 123 space group.

[0142] Figure 2 and Figure 3 Bi prepared in Example 1 of the present invention 25 FeO 40 From the SEM and TEM images, it can be observed that the microstructure is composed of square nanosheets of about 500 nm and amorphous nanoparticles. Figure 4 Bi prepared in Example 3 of the present invention 25 FeO 40 From the HRTEM image, clear lattice fringes can be observed, and the lattice spacing is 3.22 nm, corresponding to Bi 25 FeO 40 (310) crystal plane.

[0143] Figure 5 Bi prepared in Examples 1, 2, 3 and 4 of the present invention 25 FeO 40 The high-resolution O 1s spectrum of Example 1, Example 2, Example 3 and Example 4 has three peaks at about 5310.1 eV, 531.6 eV and 532.3 eV, which correspond to lattice oxygen, oxygen vacancies and surface adsorbed hydroxyl oxygen, respectively. The peak areas of the Bi prepared in Example 1, Example 2, Example 3 and Example 4 are calculated. 25 FeO 40 The oxygen vacancy contents of the samples were 27.24%, 22.8%, 47.59% and 41.52%, respectively. The presence of oxygen vacancies improved the charge storage capacity.

[0144] Figure 6 Bi prepared in Examples 1, 2, 3 and 4 of the present invention 25 FeO 40 The high-resolution Fe2p spectrum shows that the peak at around 710.2 eV corresponds to Fe 2+The peaks at around 713.2 eV and 724.8 eV correspond to Fe 3+ , calculated by peak area, the Bi prepared in Example 1, Example 2, Example 3 and Example 4 25 FeO 40 Fe 2+ The contents are 21.62%, 66.27%, 14.06% and 44.87% respectively. Figure 7 Bi prepared in Examples 1, 2, 3 and 4 of the present invention 25 FeO 40 The high-resolution Bi 4f peak can be divided into two pairs of double peaks, 158.62 / 163.97 eV and 159.64 / 165 eV are respectively attributed to the +3-valent bismuth ion and the +5-valent bismuth ion. The Bi prepared in Example 1, Example 2, Example 3 and Example 4 is calculated by peak area. 25 FeO 40 Bi 3+ The contents are 73.92%, 61.46%, 67.38% and 56.21% respectively, Bi 5+ The contents are 26.08%, 38.54%, 32.62% and 43.79% respectively. 2+ / Fe 3+ 、Bi 3+ / Bi +5 The existence of variable valence ion defects further increases the 25 FeO 40 The ability to store charge.

[0145] Figure 8 Bi prepared in Examples 1, 2, 3, 4, 5 and 6 of the present invention 25 FeO 40 Under dark conditions, applying eddy current shear force forms a current response, and turning off the eddy current shear force does not cause a current response, which proves that the Bi prepared by the present invention can be 25 FeO 40 It exhibits an obvious piezoelectric current response under dark conditions, indicating that it has piezoelectric properties.

[0146] Figure 9 、 Figure 10 、 Figure 11 and Figure 12 Bi prepared in Example 1, Example 2, Example 3 and Example 4 of the present invention are 25 FeO 40 The phase change diagram shows that after applying a 10 V deflection voltage, the phase angle flips by about 180°, proving that the dipole can be easily transformed by an external electric field.

[0147] Figure 13 、 Figure 14 、 Figure 15 and Figure 16 Bi prepared in Example 1, Example 2, Example 3 and Example 4 of the present invention are 25 FeO 40 The amplitude change diagram shows a typical "butterfly-shaped curve" under the action of the electric field, which produces a strain-electric field hysteresis phenomenon, proving that it has an obvious piezoelectric response. The d 33 The values ​​are 1.25 nm·V -1 、5.88 nm·V -1 、7.43 nm·V -1 and 6.36 nm·V -1 , Example 3 has a stronger piezoelectric effect, which is consistent with the piezoelectric current results.

[0148] Figure 17 Bi prepared in Example 3 of the present invention 25 FeO 40 The absorbance curve of 20 mg / L methylene blue in dark conditions can be used to calculate the stored electron concentration of methylene blue. The electron concentration released after 30 minutes of dark reaction is 13.18 μmol·g -1 . Figure 18 Bi prepared in Example 3 of the present invention 25 FeO 40 The EPR of holes at different times under dark conditions was calculated based on the spin number. The hole concentration released after 20 min in the dark was 129.15 μmol·g -1 This shows that due to Bi 25 FeO 40 The existence of the polarization electric field promotes the separation of electrons and holes, and realizes the simultaneous storage of electrons and holes.

[0149] Figure 19 Bi prepared in Examples 1, 2, 3, 4, 5 and 6 of the present invention 25 FeO 40 The degradation curve of 20 mg / L tetracycline under dark conditions shows that after 5 min in dark conditions, the degradation rates of Example 1, Example 2, Example 3, Example 4, Example 5 and Example 6 are 37.80%, 46.06%, 52.73%, 49.74%, 46.30% and 26.60% respectively. This is due to the mechanical force of the samples stored in Bi 25 FeO 40 Rapid release of electrons and holes. In 5-30 min, due to Bi25 FeO 40 The piezoelectric effect of the mechanical force will generate piezoelectric charges to participate in the catalytic degradation reaction. After 30 minutes, the Bi prepared in Example 1, Example 2, Example 3, Example 4, Example 5 and Example 6 25 FeO 40 The degradation rates of tetracycline can reach 52.10%, 62.58%, 81.30%, 72.30%, 74.25% and 36.30% respectively. 25 FeO 40 The degradation rate of tetracycline was the highest at 5 min and 30 min, which was attributed to its excellent charge storage capacity and piezoelectric effect.

[0150] Figure 20 Bi prepared in Example 3 of the present invention 25 FeO 40 TOC removal rate of 40 mg / L tetracycline under dark conditions. 25 FeO 40 Under dark conditions, the removal rate of 40 mg / L tetracycline can reach 71.04% after 5 minutes and 71.78% after 30 minutes, indicating that Bi 25 FeO 40 It has a strong mineralization ability for tetracycline.

[0151] Figure 21 Bi prepared in Example 3 of the present invention 25 FeO 40 In the cyclic degradation diagram of 20 mg / L tetracycline under dark conditions, the degradation rate of the first cycle is 81.3%. Although the stored charge is continuously consumed as the number of cycles increases, the degradation rate can still reach 57.65% after five cycles, which shows that the Bi prepared by the present invention is 25 FeO 40 Has good cycle stability.

[0152] Figure 22 The Bi prepared in Example 3 of the present invention 25 FeO 40 Active species capture diagram under dark conditions. Tert-butyl alcohol, p-benzoquinone, sodium oxalate and copper sulfate are respectively used as ·OH, ·O2 - 、h + and e - The capture agent, compared with the degradation rate of 81.3% without the introduction of the capture agent, after adding the capture agent, the Bi prepared in Example 3 25 FeO 40The degradation rates of ·OH, ·O2 - 、h + and e - play a role in the degradation process.

[0153] Figure 23 and Figure 24 They are respectively Bi obtained in Preparation Example 3 of the present invention 25 FeO 40 LC-MS images of the reaction solution after 5 min and 30 min of degradation of 20 mg / L tetracycline under dark conditions. At 5 min of dark reaction, intermediates with mass-to-charge ratios (m / z) of 64, 102, 110, 139, 163, 195, 326, 383, 427, and 437 were detected in the tetracycline degradation solution; after 30 min, intermediates with m / z of 64, 120, 122, 163, 219, and 306 were detected. The disappearance of molecules with large mass-to-charge ratios indicated that Bi 25 FeO 40 The actual mineralization degradation process of tetracycline.

[0154] Figure 25 Bi prepared in Example 3 of the present invention 25 FeO 40 The absorbance change diagram of the degradation of a mixed solution of 20 mg / L ciprofloxacin, 10 mg / L rhodamine B, 20 mg / L methylene blue, 10 mg / L methylene orange and 20 mg / L tetracycline under dark conditions. As time goes by, the absorption intensity gradually weakens. After 30 minutes of reaction, the absorption intensity decreases significantly, indicating that the prepared Bi 25 FeO 40 Piezoelectric catalysts are universally applicable to water pollutants and can degrade antibiotics and dyes.

[0155] The Bi prepared by the present invention 25 FeO 40 Piezoelectric catalysts have strong polarization electric fields, oxygen vacancies and variable valence ion defects, which improve the ability to store charge and generate piezoelectric charge. Under mechanical force in dark conditions, Bi 25 FeO 40 Piezoelectric catalysts have the ability to efficiently mineralize antibiotics and universally degrade a variety of water pollutants.

[0156] The above is only one embodiment of the present invention, not all or the only embodiment. Any equivalent transformation of the technical solution of the present invention made by ordinary technicians in this field after reading the specification of the present invention is covered by the claims of the present invention.

Claims

1. A Bi 25 FeO 40 A method for preparing a piezoelectric catalyst, characterized in that: The following steps are involved: Step 1: Dissolve a bismuth source and an iron source in ethylene glycol at a molar ratio of 1:1, and then add water to form a precursor solution; wherein the total concentration of the iron source and the bismuth source in the ethylene glycol is 0.04-0.4 mol / L; and the volume ratio of ethylene glycol to water is 50:(40-90); Step 2: Under stirring, adjust the pH value of the precursor solution to 9-11 with NH3·H2O to precipitate, and wash and dry the precipitate in sequence; Step 3: Mix the precipitate with NaOH solution and conduct hydrothermal reaction. After the reaction is completed, wash and dry in sequence to obtain Bi 25 FeO 40 Piezoelectric catalyst; wherein the concentration of the NaOH solution is 6-10 mol / L; the hydrothermal reaction temperature is 120-160° C., and the hydrothermal reaction time is 8-20 h.

2. Bi according to claim 1 25 FeO 40 A method for preparing a piezoelectric catalyst, characterized in that: In step 1, the iron source is Fe(NO3)3·6H2O or FeCl3·6H2O.

3. Bi according to claim 1 25 FeO 40 A method for preparing a piezoelectric catalyst, characterized in that: In step 1, the bismuth source is Bi(NO3)3·5H2O or BiCl3·6H2O.

4. Bi obtained by the preparation method according to any one of claims 1 to 3 25 FeO 40 A piezoelectric catalyst, characterized in that The Bi 25 FeO 40 The piezoelectric catalyst has a bismuthite structure, a cubic crystal system, a 123 space group, and a microscopic morphology composed of square nanosheets and nanoparticles.

5. Bi according to claim 4 25 FeO 40 The application of piezoelectric catalyst in catalytic degradation of organic pollutants is characterized by: The catalytic degradation of organic pollutants is carried out under dark conditions.

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