WO2018040685A1 - Method for directionally constructing heterostructure by selectively etching ferroelectric-based photocatalytic material - Google Patents
Method for directionally constructing heterostructure by selectively etching ferroelectric-based photocatalytic material Download PDFInfo
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- WO2018040685A1 WO2018040685A1 PCT/CN2017/089681 CN2017089681W WO2018040685A1 WO 2018040685 A1 WO2018040685 A1 WO 2018040685A1 CN 2017089681 W CN2017089681 W CN 2017089681W WO 2018040685 A1 WO2018040685 A1 WO 2018040685A1
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- 238000005530 etching Methods 0.000 title claims abstract description 26
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- NKZSPGSOXYXWQA-UHFFFAOYSA-N dioxido(oxo)titanium;lead(2+) Chemical compound [Pb+2].[O-][Ti]([O-])=O NKZSPGSOXYXWQA-UHFFFAOYSA-N 0.000 claims abstract description 35
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- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 6
- AJCDFVKYMIUXCR-UHFFFAOYSA-N oxobarium;oxo(oxoferriooxy)iron Chemical compound [Ba]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O AJCDFVKYMIUXCR-UHFFFAOYSA-N 0.000 description 4
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- 241000872931 Myoporum sandwicense Species 0.000 description 3
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical group O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 3
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/02—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the alkali- or alkaline earth metals or beryllium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/14—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of germanium, tin or lead
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/843—Arsenic, antimony or bismuth
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/843—Arsenic, antimony or bismuth
- B01J23/8437—Bismuth
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
- B01J35/39—Photocatalytic properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/03—Precipitation; Co-precipitation
- B01J37/031—Precipitation
- B01J37/035—Precipitation on carriers
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
- B01J37/10—Heat treatment in the presence of water, e.g. steam
Definitions
- the invention relates to the field of photocatalysis, in particular to a method for selectively etching a ferroelectric-based photocatalytic material to orient a heterostructure.
- the spatial separation of photogenerated charges can effectively suppress the bulk recombination of photogenerated carriers and the occurrence of reverse reactions, which is a prerequisite for obtaining high quantum efficiency photocatalysts.
- the ferroelectric material has a spontaneous polarization at a temperature below the Curie temperature, and the spontaneous polarization can be reversed with an external electric field.
- the photocatalyst will generate photo-generated carriers under illumination conditions, and the spontaneous polarization will establish a small electric field inside the crystal grains.
- the electrons and holes are separated by the electric field, and the photo-generated charges can be more effectively promoted to migrate to the catalyst surface. Reduce the recombination rate of photogenerated charge during this bulk transport.
- the surface atomic structure of ferroelectric materials is generally not conducive to the decomposition reaction of water, and even if the photogenerated carriers are effectively separated and transported to the surface by the built-in electric field, the photocatalytic performance cannot be fully exerted due to the surface structure limitation.
- the construction of high catalytically active materials on the surface of ferroelectric materials is an effective means to give full play to the advantages of ferroelectric materials.
- the photogenerated electrons reach the surface to construct high-efficiency hydrogen-generating materials, and the photo-generated holes reach the surface to construct high-efficiency oxygen-generating materials.
- the orientation structure of the heterostructure is beneficial to the directional separation of photogenerated carriers, which can effectively improve the photocatalytic activity of heterostructures.
- a method for selectively etching a ferroelectric-based photocatalytic material to construct a heterostructure by using a ferroelectric field in a semiconductor ferroelectric material to induce a difference in surface charging properties, thereby causing preferentially selective adsorption of a negatively charged acid ion With a positively charged surface, the semiconductor ferroelectric material is placed in an aqueous solution containing an etchant acid, and a selective etching of the surface of the ferroelectric material is achieved by a hydrothermal treatment process, and a heterostructure is oriented on the surface of the ferroelectric substrate material. .
- the ferroelectric material is a variety of ternary or ternary metal compound ferroelectric materials.
- the ferroelectric material is lead titanate, barium titanate or barium ferrite.
- the etchable acid is a variety of inorganic acids or mixed acid solutions thereof.
- the etchable acid is one or a mixture of two or more of hydrofluoric acid, hydrochloric acid, sulfuric acid, and nitric acid.
- the molar concentration of the acid is from 0.1 mM to 5 M.
- the hydrothermal treatment temperature is 30 ° C to 300 ° C, and the hydrothermal treatment time is 10 min to 96 h.
- the invention utilizes the spontaneous polarization of the ferroelectric material to establish a built-in electric field inside the crystal, and the photogenerated electrons and holes are separated by the electric field, and can migrate to the catalyst surface more effectively, thereby reducing the photogenerated charge in the bulk transport process. Compound rate.
- the negatively charged acid ions are preferentially adsorbed on the positively charged surface to realize selective etching of the ferroelectric material surface to construct the heterostructure photocatalyst.
- Selectively build high-efficiency hydrogen production materials on the surface of photogenerated electrons which can effectively improve photo-generated charge separation, improve surface catalytic activity, and greatly improve the photocatalytic activity of heterostructures.
- the invention selectively etches a ferroelectric-based photocatalytic material to construct a heterostructure structure, and uses a ferroelectric material as a precursor to fully utilize the built-in ferroelectric field to effectively separate photo-generated carriers and induce surface charging properties.
- the difference is that the surface of the photogenerated electrons is selectively etched in situ to construct a highly efficient hydrogen generating active surface.
- the two basic processes of bulk transport separation and surface transfer of photogenerated charge in photocatalytic process are considered, which provides an effective reference for constructing high quantum efficiency photocatalyst system.
- FIG. 1 Scanning electron microscopy (SEM) photograph of lead titanate crystals; (a) is a SEM photograph of the original single-domain ferroelectric material lead titanate nanosheet crystals with (001) crystals exposed on the upper and lower surfaces. (b) SEM photograph of the lead titanate crystal after selective etching on the surface of the graph, where only a side (001) crystal plane is convex.
- SEM scanning electron microscopy
- FIG. 1 SEM photograph of the selective photodeposition of Au, MnO x and their co-deposition of lead titanate nano-plate crystals; (a) is a SEM photograph of selective photodeposition of Au by lead titanate crystal; (b) The figure is a SEM photograph of selective photodeposition of MnO x by lead titanate crystal; (c) is a SEM photograph of selective co-deposition of Au and MnO x of lead titanate crystal.
- FIG. 3 SEM photograph of selective photodeposition of Au, MnO x and co-deposition of single-domain ferroelectric material lead-acid (PbTiO 3 ) nano-platelet crystals with hydrofluoric acid selective etching;
- the figure is a selective photodeposition Au of hydrofluoric acid etched lead titanate crystal;
- (b) a selective photodeposition of MnO x of a hydrofluoric acid etched lead titanate crystal;
- the present invention utilizes a ferroelectric field in a semiconductor ferroelectric material (barium titanate, lead titanate, barium ferrite, etc.) to induce a difference in surface charging properties, resulting in preferentially selective adsorption of negatively charged acid ions.
- a method of selectively etching a ferroelectric material to construct a heterostructure photocatalyst is carried out, and the semiconductor ferroelectric material is placed in an aqueous solution containing an etchant acid, and the surface of the ferroelectric material is realized by a hydrothermal treatment process.
- the surface is oriented to construct a heterostructure, and the optimal photocatalytic performance is obtained by adjusting the type and concentration of the acid and the hydrothermal treatment temperature.
- the directional structure of heterogeneous structure is beneficial to the directional separation of photogenerated carriers, and can effectively improve the photocatalytic activity of heterostructures. It is the key research direction in the field of photocatalysis.
- the heterostructure is titanium oxide/lead titanate, titanium oxide/barium titanate, iron oxide/barium ferrite, and the like.
- a certain amount of ternary and ternary metal compound ferroelectric materials (material form: powder or film) are placed in an etchable acidic solution (type of solution: inorganic solution or organic solution), and then transferred to the reaction kettle.
- the inner tank material is PTFE material or other corrosion-resistant material. After sealing, the reaction kettle is heated to a predetermined temperature in an oven for a certain period of time. After cooling, the reaction vessel is opened, and the suspension after the reaction is collected.
- the aqueous solution is dried several times and then dried (the temperature is between 30 and 200 ° C) to obtain a crystal of a ferroelectric material having a convex surface on the surface of the (001) crystal plane, wherein the convex portion is newly formed from the ferroelectric matrix material.
- the ferroelectric material comprises various ternary and ternary metal compounds, such as lead titanate, barium titanate, barium ferrite, and the like.
- the etchable acid includes various inorganic acids and mixed acid solutions thereof, such as hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid, and the like.
- the molar concentration of the acid in the etchable acid aqueous solution is from 0.1 mM to 5 M (preferably from 0.5 mM to 2 M).
- the hydrothermal treatment temperature is from 30 ° C to 300 ° C (preferably from 100 ° C to 300 ° C), and the hydrothermal treatment time is from 10 min to 96 h (preferably from 1 h to 24 h).
- a prepared single-domain ferroelectric material lead titanate (PbTiO 3 ) flake crystal 300 mg (the morphology is shown in FIG. 1a) is weighed, and the single-domain lead titanate flake crystal is of a height. 150nm, length 600 ⁇ 1100nm, the upper and lower surface exposed crystal face is (001) crystal face, with different charges.
- the reactor was sealed, it was placed in an oven at 200 ° C for 3 h, and the reaction sample was taken out, washed with deionized water and dried at 80 ° C to obtain a lead titanate crystal having a convex surface on one side (001) crystal surface, wherein The protrusion is titanium oxide as shown in Fig. 1(b).
- Single-domain ferroelectric material lead titanate (PbTiO 3 ) plate crystal selective photodeposition Au 300mg of prepared ferroelectric material lead titanate crystals is placed in a mixture of 40ml of water and anhydrous methanol (water and anhydrous methanol volume ratio of 1: 3, using the effect of water was mixed with anhydrous methanol to provide electronic sacrificial agent), after 4 HAuCl4 was added thereto, the content of 4 HAuCl4 was 3wt% (HAuCl 4 to provide an optical effect Precursor of the reduction reaction).
- the system was photodeposited for 6 h under a xenon lamp, and the sample was washed with deionized water and dried at 80 ° C as shown in Fig. 2(a).
- Single-domain ferroelectric material lead titanate (PbTiO 3 ) plate crystal selective photodeposition MnO x 300mg of prepared ferroelectric material lead titanate crystals in 50ml containing 0.6g NaIO 3 aqueous solution (using NaIO 3 MnSO 4 ⁇ H 2 O (the role of MnSO 4 ⁇ H 2 O is to provide a precursor for photooxidation), and the content of MnSO 4 ⁇ H 2 O is 4wt. %.
- the system was photodeposited under a xenon lamp for 6 h, and the sample was washed with deionized water and dried at 80 ° C as shown in Figure 2 (b).
- Single-domain ferroelectric material lead titanate (PbTiO 3 ) plate crystal selective co-deposited Au and MnO x 300 mg of prepared ferroelectric material lead titanate crystals were placed in 50 ml of distilled water, and then HAuCl 4 was added thereto.
- MnSO 4 ⁇ H 2 O has a content of HAuCl 4 of 3 wt% and a content of MnSO 4 ⁇ H 2 O of 4 wt%.
- the system was light deposited under a xenon lamp for 6 h, and the sample was washed with deionized water and dried at 80 °C. As shown in Figure 2 (c).
- FIG 2 (c) and FIG. 3 (c) comparative As can be seen, larger crystals after etching, deposited on the surface of Au and MnO x density, more uniform distribution.
- the implementation results show that the invention utilizes the ferroelectric field in the semiconductor ferroelectric material to induce the difference in surface charging properties, so that the negatively charged acid ions are preferentially and selectively adsorbed on the positively charged surface, and the surface of the ferroelectric material can be selectively selectively engraved.
- the eccentricity constructs a heterostructure photocatalyst. Light-emitting single-domain ferroelectric material lead titanate nano-plate crystals built-in electric field effect downloading effective separation, photoreduction deposition of metal Au and photo-oxidation deposition of MnO x can selectively occur in single-domain ferroelectric material titanic acid Lead-like crystals have different charged properties on the (001) crystal plane.
- Hydrofluoric acid selectively etched single-domain ferroelectric material lead titanate (PbTiO 3 ) plate crystal which generates protrusions on the surface of one side (001) crystal surface to form TiO 2 nanoparticles, and hydrofluoric acid is confirmed by selective deposition.
- Etching the lead titanate crystals in an aqueous solution does not destroy the single-domain ferroelectric properties.
- the TiO 2 nanoparticle protrusion on the surface of the lead (001) crystal surface helps to improve the catalytic activity of the (001) crystal plane and further improve the photodegradation hydrogen production efficiency of lead titanate.
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Abstract
A method for directionally constructing a heterostructure by selectively etching a ferroelectric-based photocatalytic material, comprising: by using the feature that a ferroelectric field of a semiconductor ferroelectric material (barium titanate, lead titanate, bismuth ferrite or the like) induces a difference in surface charge property, so that negatively charged acid radical ions are preferentially and selectively adsorbed on a positively charged surface, placing the semiconductor ferroelectric material in a water solution containing etching acid, and selectively etching the surface of the ferroelectric material by means of a hydrothermal treatment process, to directionally construct a heterostructure on the surface of a ferroelectric substrate material. By means of the method, an optimal photocatalytic performance can be obtained by adjusting the type and concentration of acid, and a hydrothermal treatment temperature. The directional construction of a heterostructure facilitates the directional separation of photo-generated carriers, and can effectively improve the photocatalytic activity of the heterostructure.
Description
本发明涉及光催化领域，具体为一种选择性刻蚀铁电基光催化材料以定向构筑异质结构的方法。The invention relates to the field of photocatalysis, in particular to a method for selectively etching a ferroelectric-based photocatalytic material to orient a heterostructure.
光生电荷的空间分离能够有效抑制光生载流子的体相复合以及逆反应的发生，是获得高量子效率光催化剂的先决条件。铁电材料在低于居里温度时具有自发极化作用，而且自发极化强度可以随外电场而反转。光催化剂在光照条件下将产生光生载流子，而自发极化将在晶粒内部建立微小电场，电子和空穴在该电场驱动下分离，并能更有效地促进光生电荷迁移至催化剂表面，减少光生电荷在此体相传输过程中的复合率。但是，铁电材料的表面原子结构通常不利于诱导水的分解反应，即使在光生载流子在内建电场作用下有效分离并输运至表面，其光催化性能受到表面结构限制无法充分发挥。The spatial separation of photogenerated charges can effectively suppress the bulk recombination of photogenerated carriers and the occurrence of reverse reactions, which is a prerequisite for obtaining high quantum efficiency photocatalysts. The ferroelectric material has a spontaneous polarization at a temperature below the Curie temperature, and the spontaneous polarization can be reversed with an external electric field. The photocatalyst will generate photo-generated carriers under illumination conditions, and the spontaneous polarization will establish a small electric field inside the crystal grains. The electrons and holes are separated by the electric field, and the photo-generated charges can be more effectively promoted to migrate to the catalyst surface. Reduce the recombination rate of photogenerated charge during this bulk transport. However, the surface atomic structure of ferroelectric materials is generally not conducive to the decomposition reaction of water, and even if the photogenerated carriers are effectively separated and transported to the surface by the built-in electric field, the photocatalytic performance cannot be fully exerted due to the surface structure limitation.
在铁电材料表面构筑高催化活性材料是充分发挥铁电材料优势的有效手段，在光生电子到达表面构筑高效产氢材料，在光生空穴达到表面构筑高效产氧材料。据此我们提出选择性刻蚀铁电基光催化材料以定向构筑异质结构的方法，异质结构的定向构筑有利于光生载流子的定向分离，可有效提高异质结构的光催化活性。The construction of high catalytically active materials on the surface of ferroelectric materials is an effective means to give full play to the advantages of ferroelectric materials. The photogenerated electrons reach the surface to construct high-efficiency hydrogen-generating materials, and the photo-generated holes reach the surface to construct high-efficiency oxygen-generating materials. Based on this, we propose a method of selectively etching ferroelectric-based photocatalytic materials to construct a heterostructure. The orientation structure of the heterostructure is beneficial to the directional separation of photogenerated carriers, which can effectively improve the photocatalytic activity of heterostructures.
发明内容Summary of the invention
本发明的目的在于提供一种选择性刻蚀铁电基光催化材料以定向构筑异质结构的方法，能够在光生载流子有效分离的条件下，进一步提高铁电材料表面催化活性。It is an object of the present invention to provide a method for selectively etching a ferroelectric-based photocatalytic material to orient a heterostructure, thereby further improving the surface catalytic activity of the ferroelectric material under the condition that the photogenerated carriers are effectively separated.
本发明的技术方案是：The technical solution of the present invention is:
一种选择性刻蚀铁电基光催化材料以定向构筑异质结构的方法，利用半导体铁电材料中的铁电场诱导表面带电属性的差异，导致带负电性的酸根离子优先选择性地吸附在带正电荷表面的特点，将半导体铁电材料放入含有刻蚀性酸的水溶液中，通过水热处理过程实现对铁电材料表面的选择性刻蚀，在铁电基体材料表面定向构筑异质结构。A method for selectively etching a ferroelectric-based photocatalytic material to construct a heterostructure by using a ferroelectric field in a semiconductor ferroelectric material to induce a difference in surface charging properties, thereby causing preferentially selective adsorption of a negatively charged acid ion With a positively charged surface, the semiconductor ferroelectric material is placed in an aqueous solution containing an etchant acid, and a selective etching of the surface of the ferroelectric material is achieved by a hydrothermal treatment process, and a heterostructure is oriented on the surface of the ferroelectric substrate material. .
所述的铁电材料为各种三元或三元以上金属化合物铁电材料。The ferroelectric material is a variety of ternary or ternary metal compound ferroelectric materials.
优选的，所述的铁电材料为钛酸铅、钛酸钡或铁酸铋。Preferably, the ferroelectric material is lead titanate, barium titanate or barium ferrite.
所述的刻蚀性酸为各种无机酸或其混合酸溶液。The etchable acid is a variety of inorganic acids or mixed acid solutions thereof.
优选的，所述的刻蚀性酸为氢氟酸、盐酸、硫酸、硝酸之一或两种以上混合。Preferably, the etchable acid is one or a mixture of two or more of hydrofluoric acid, hydrochloric acid, sulfuric acid, and nitric acid.
所述的刻蚀性酸水溶液中，酸的摩尔浓度为0.1mM～5M。
In the etchable acid aqueous solution, the molar concentration of the acid is from 0.1 mM to 5 M.
所述的水热处理温度为30℃～300℃，水热处理时间为10min～96h。The hydrothermal treatment temperature is 30 ° C to 300 ° C, and the hydrothermal treatment time is 10 min to 96 h.
本发明的设计思想如下：The design idea of the invention is as follows:
本发明利用铁电材料自发极化在晶体内部建立内建电场，光生电子和空穴在该电场驱动下分离，并能更有效地迁移至催化剂表面，减少光生电荷在体相输运过程中的复合率。并且，结合内建电场诱导的表面带电属性的差异，利用带负电性的酸根离子优先选择性地吸附在带正电荷表面，实现对铁电材料表面选择性刻蚀定向构筑异质结构光催化剂。选择性在光生电子到达表面构筑高效产氢材料，可有效提高光生电荷分离的同时，提高表面催化活性，大幅度提高异质结构的光催化活性。The invention utilizes the spontaneous polarization of the ferroelectric material to establish a built-in electric field inside the crystal, and the photogenerated electrons and holes are separated by the electric field, and can migrate to the catalyst surface more effectively, thereby reducing the photogenerated charge in the bulk transport process. Compound rate. Moreover, combined with the difference in surface charge properties induced by the built-in electric field, the negatively charged acid ions are preferentially adsorbed on the positively charged surface to realize selective etching of the ferroelectric material surface to construct the heterostructure photocatalyst. Selectively build high-efficiency hydrogen production materials on the surface of photogenerated electrons, which can effectively improve photo-generated charge separation, improve surface catalytic activity, and greatly improve the photocatalytic activity of heterostructures.
本发明的优点及有益效果是：The advantages and benefits of the present invention are:
本发明选择性刻蚀铁电基光催化材料以定向构筑异质结构的方法，以铁电材料为前驱体，充分利用其内建铁电场有效分离光生载流子的特性以及诱导表面带电属性的差异，选择性地在光生电子到达的表面原位刻蚀构建高效产氢活性表面。同时兼顾了光催化过程中的光生电荷的体相输运分离和表面转移两大基本过程，为构筑高量子效率光催化剂体系提供有效参考。The invention selectively etches a ferroelectric-based photocatalytic material to construct a heterostructure structure, and uses a ferroelectric material as a precursor to fully utilize the built-in ferroelectric field to effectively separate photo-generated carriers and induce surface charging properties. The difference is that the surface of the photogenerated electrons is selectively etched in situ to construct a highly efficient hydrogen generating active surface. At the same time, the two basic processes of bulk transport separation and surface transfer of photogenerated charge in photocatalytic process are considered, which provides an effective reference for constructing high quantum efficiency photocatalyst system.
图1.钛酸铅晶体的扫描电子显微镜(SEM)照片；其中，(a)图是原始单电畴铁电材料钛酸铅纳米片状晶体的SEM照片，上下表面暴露的为(001)晶面；(b)图表面选择性刻蚀后的钛酸铅晶体的SEM照片，只有一侧(001)晶面表面上产生凸起。Figure 1. Scanning electron microscopy (SEM) photograph of lead titanate crystals; (a) is a SEM photograph of the original single-domain ferroelectric material lead titanate nanosheet crystals with (001) crystals exposed on the upper and lower surfaces. (b) SEM photograph of the lead titanate crystal after selective etching on the surface of the graph, where only a side (001) crystal plane is convex.
图2.钛酸铅纳米片状晶体选择性光沉积Au、MnOx及二者共沉积的SEM照片；其中，(a)图是钛酸铅晶体选择性光沉积Au的SEM照片；(b)图是钛酸铅晶体选择性光沉积MnOx的SEM照片；(c)图是钛酸铅晶体选择性共沉积Au和MnOx的SEM照片。Figure 2. SEM photograph of the selective photodeposition of Au, MnO x and their co-deposition of lead titanate nano-plate crystals; (a) is a SEM photograph of selective photodeposition of Au by lead titanate crystal; (b) The figure is a SEM photograph of selective photodeposition of MnO x by lead titanate crystal; (c) is a SEM photograph of selective co-deposition of Au and MnO x of lead titanate crystal.
图3.氢氟酸选择性刻蚀的单电畴铁电材料钛酸铅(PbTiO3)纳米片状晶体的选择性光沉积Au、MnOx及二者共沉积的SEM照片；其中，(a)图是氢氟酸刻蚀的钛酸铅晶体的选择性光沉积Au；(b)图氢氟酸刻蚀的钛酸铅晶体的选择性光沉积MnOx；(c)图是氢氟酸刻蚀的钛酸铅晶体的选择性共沉积Au和MnOx的SEM照片。Figure 3. SEM photograph of selective photodeposition of Au, MnO x and co-deposition of single-domain ferroelectric material lead-acid (PbTiO 3 ) nano-platelet crystals with hydrofluoric acid selective etching; The figure is a selective photodeposition Au of hydrofluoric acid etched lead titanate crystal; (b) a selective photodeposition of MnO x of a hydrofluoric acid etched lead titanate crystal; (c) a picture of hydrofluoric acid SEM photograph of selective co-deposition of Au and MnO x of etched lead titanate crystals.
在具体实施过程中，本发明利用半导体铁电材料(钛酸钡、钛酸铅、铁酸铋等)中的铁电场诱导表面带电属性的差异，导致带负电性的酸根离子优先选择性地吸附在带正电荷表面，实现对铁电材料选择性刻蚀定向构筑异质结构光催化剂方法，将半导体铁电材料放入含有刻蚀性酸的水溶液中，通过水热处理过程实现铁电材料表面的选择性刻蚀，在铁电基体材料表
面定向构筑异质结构，通过调节酸的种类、浓度以及水热处理温度获得最优光催化性能。异质结构的定向构筑有利于光生载流子的定向分离，可有效提高异质结构的光催化活性，是光催化领域的重点研究方向。In a specific implementation process, the present invention utilizes a ferroelectric field in a semiconductor ferroelectric material (barium titanate, lead titanate, barium ferrite, etc.) to induce a difference in surface charging properties, resulting in preferentially selective adsorption of negatively charged acid ions. On a positively charged surface, a method of selectively etching a ferroelectric material to construct a heterostructure photocatalyst is carried out, and the semiconductor ferroelectric material is placed in an aqueous solution containing an etchant acid, and the surface of the ferroelectric material is realized by a hydrothermal treatment process. Selective etching, in the ferroelectric matrix material table
The surface is oriented to construct a heterostructure, and the optimal photocatalytic performance is obtained by adjusting the type and concentration of the acid and the hydrothermal treatment temperature. The directional structure of heterogeneous structure is beneficial to the directional separation of photogenerated carriers, and can effectively improve the photocatalytic activity of heterostructures. It is the key research direction in the field of photocatalysis.
所述的异质结构为氧化钛/钛酸铅、氧化钛/钛酸钡、氧化铁/铁酸钡等。将一定量的三元及三元以上的金属化合物铁电材料(材料形式：粉体或薄膜)放入刻蚀性酸性溶液中(溶液的种类：无机溶液或有机溶液)，然后转入反应釜(内胆材质为聚四氟材料或其它耐腐蚀性材料)中，密闭后将反应釜在烘箱中加热到预定温度，保温一定的时间，冷却后打开反应釜，收集反应后的悬浮液，用水溶液多次清洗后干燥(温度在30～200℃之间)，得到单侧(001)晶面表面有凸起的铁电材料晶体，其中凸起部分为从铁电母体材料上新生成的二元氧化物，从而获得一种独特的由母体材料和凸起物构成的异质结构。The heterostructure is titanium oxide/lead titanate, titanium oxide/barium titanate, iron oxide/barium ferrite, and the like. A certain amount of ternary and ternary metal compound ferroelectric materials (material form: powder or film) are placed in an etchable acidic solution (type of solution: inorganic solution or organic solution), and then transferred to the reaction kettle. (The inner tank material is PTFE material or other corrosion-resistant material). After sealing, the reaction kettle is heated to a predetermined temperature in an oven for a certain period of time. After cooling, the reaction vessel is opened, and the suspension after the reaction is collected. The aqueous solution is dried several times and then dried (the temperature is between 30 and 200 ° C) to obtain a crystal of a ferroelectric material having a convex surface on the surface of the (001) crystal plane, wherein the convex portion is newly formed from the ferroelectric matrix material. A meta-oxide to obtain a unique heterostructure consisting of a parent material and a protrusion.
其中，所述铁电材料包括各种三元及三元以上金属化合物，如：钛酸铅、钛酸钡、铁酸铋等。所述刻蚀性酸包括各种无机酸及其混合酸溶液，如：氢氟酸、盐酸、硫酸、硝酸等。所述刻蚀性酸水溶液中，酸的摩尔浓度为0.1mM～5M(优选为0.5mM～2M)。所述的水热处理温度为30℃～300℃(优选为100℃～300℃)，水热处理时间为10min～96h(优选为1h～24h)。Wherein, the ferroelectric material comprises various ternary and ternary metal compounds, such as lead titanate, barium titanate, barium ferrite, and the like. The etchable acid includes various inorganic acids and mixed acid solutions thereof, such as hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid, and the like. The molar concentration of the acid in the etchable acid aqueous solution is from 0.1 mM to 5 M (preferably from 0.5 mM to 2 M). The hydrothermal treatment temperature is from 30 ° C to 300 ° C (preferably from 100 ° C to 300 ° C), and the hydrothermal treatment time is from 10 min to 96 h (preferably from 1 h to 24 h).
下面结合附图和实施例来详细说明本发明。The invention will be described in detail below with reference to the accompanying drawings and embodiments.
实施例Example
本实施例中，称取已制备好的单电畴铁电材料钛酸铅(PbTiO3)片状晶体300mg(形貌如图1a所示)，单电畴钛酸铅片状晶体尺寸为高度150nm，长度600～1100nm，上下表面暴露晶面为(001)晶面，带不同电荷。将其放入装有氢氟酸水溶液中(摩尔浓度为1M)，转移至以聚四氟乙烯为内衬的80mL不锈钢反应釜中。反应釜密封后，放入烘箱在200℃水热处理3h，取出反应样品，用去离子水清洗并在80℃烘干，得到单侧(001)晶面表面有凸起的钛酸铅晶体，其中凸起物为氧化钛，如图1(b)所示。In this embodiment, a prepared single-domain ferroelectric material lead titanate (PbTiO 3 ) flake crystal 300 mg (the morphology is shown in FIG. 1a) is weighed, and the single-domain lead titanate flake crystal is of a height. 150nm, length 600 ~ 1100nm, the upper and lower surface exposed crystal face is (001) crystal face, with different charges. This was placed in an aqueous solution of hydrofluoric acid (molar concentration of 1 M) and transferred to an 80 mL stainless steel autoclave lined with polytetrafluoroethylene. After the reactor was sealed, it was placed in an oven at 200 ° C for 3 h, and the reaction sample was taken out, washed with deionized water and dried at 80 ° C to obtain a lead titanate crystal having a convex surface on one side (001) crystal surface, wherein The protrusion is titanium oxide as shown in Fig. 1(b).
单电畴铁电材料钛酸铅(PbTiO3)片状晶体选择性光沉积Au：将已制备好的铁电材料钛酸铅晶体300mg放入40ml含水、无水甲醇的混合液中(水与无水甲醇的体积比为1:3，采用水与无水甲醇混合的作用是提供电子牺牲剂)，后向其中加入HAuCl4，使HAuCl4的含量为3wt％(HAuCl4的作用是提供光还原反应的前驱体)。该体系在氙灯下光沉积6h，得到样品用去离子水清洗并在80℃烘干，如图2(a)所示。Single-domain ferroelectric material lead titanate (PbTiO 3 ) plate crystal selective photodeposition Au: 300mg of prepared ferroelectric material lead titanate crystals is placed in a mixture of 40ml of water and anhydrous methanol (water and anhydrous methanol volume ratio of 1: 3, using the effect of water was mixed with anhydrous methanol to provide electronic sacrificial agent), after 4 HAuCl4 was added thereto, the content of 4 HAuCl4 was 3wt% (HAuCl 4 to provide an optical effect Precursor of the reduction reaction). The system was photodeposited for 6 h under a xenon lamp, and the sample was washed with deionized water and dried at 80 ° C as shown in Fig. 2(a).
氢氟酸选择性刻蚀的单电畴铁电材料钛酸铅(PbTiO3)片状晶体的选择性光沉积Au：将已制备好的(001)晶面表面凸起的钛酸铅晶体300mg加入40ml含水、无水甲醇的混合液中
(水与无水甲醇的体积比为1:3)，后向其中加入HAuCl4，使HAuCl4的含量为3wt％。该体系在氙灯下光沉积6h，得到样品用去离子水清洗并在80℃烘干，如图3(a)所示。Selective photodeposition of single-domain ferroelectric material lead titanate (PbTiO 3 ) plate crystals by hydrofluoric acid selective etching Au: Lead crystals of lead titanate having a prepared (001) crystal surface 40 ml of a mixed aqueous solution of anhydrous methanol (1:3 by volume of water and anhydrous methanol) was added, and then HAuCl 4 was added thereto so that the content of HAuCl 4 was 3 wt%. The system was light deposited under a xenon lamp for 6 h, and the sample was washed with deionized water and dried at 80 ° C as shown in Figure 3 (a).
将图2(a)与图3(a)比较可以看出，经刻蚀后的晶体，表面沉积的Au颗粒密度更高。Comparing Fig. 2(a) with Fig. 3(a), it can be seen that the etched crystal has a higher density of Au particles deposited on the surface.
氢氟酸选择性刻蚀的单电畴铁电材料钛酸铅(PbTiO3)片状晶体的选择性光沉积MnOx：将已制备好的(001)晶面表面凸起的钛酸铅晶体300mg加入50ml含0.6g NaIO3水溶液中，后向其中加入MnSO4·H2O，使MnSO4·H2O的含量为4wt％。该体系在氙灯下光沉积6h，得到样品用去离子水清洗并在80℃烘干，如图3(b)所示。Selective photodeposition of MnO x of single-domain ferroelectric material lead titanate (PbTiO 3 ) plate crystals by selective etching of hydrofluoric acid: lead titanate crystals with raised (001) crystal surface 300 mg was added to 50 ml of an aqueous solution containing 0.6 g of NaIO 3 , and then MnSO 4 ·H 2 O was added thereto so that the content of MnSO 4 ·H 2 O was 4% by weight. The system was photodeposited for 6 h under a xenon lamp, and the sample was washed with deionized water and dried at 80 ° C as shown in Figure 3 (b).
单电畴铁电材料钛酸铅(PbTiO3)片状晶体选择性光沉积MnOx：将已制备好的铁电材料钛酸铅晶体300mg放入50ml含0.6g NaIO3水溶液(采用NaIO3的作用是作为空穴牺牲剂)中，后向其中加入MnSO4·H2O(MnSO4·H2O的作用是提供光氧化反应的前驱体)，使MnSO4·H2O的含量为4wt％。该体系在氙灯下光沉积6h，得到样品用去离子水清洗并在80℃烘干，如图2(b)所示。Single-domain ferroelectric material lead titanate (PbTiO 3 ) plate crystal selective photodeposition MnO x : 300mg of prepared ferroelectric material lead titanate crystals in 50ml containing 0.6g NaIO 3 aqueous solution (using NaIO 3 MnSO 4 ·H 2 O (the role of MnSO 4 ·H 2 O is to provide a precursor for photooxidation), and the content of MnSO 4 ·H 2 O is 4wt. %. The system was photodeposited under a xenon lamp for 6 h, and the sample was washed with deionized water and dried at 80 ° C as shown in Figure 2 (b).
将图2(b)与图3(b)比较可以看出，经刻蚀后的晶体，表面沉积的MnOx纳米片分布更加均匀。Comparing Fig. 2(b) with Fig. 3(b), it can be seen that the surface deposited MnO x nanosheets are more evenly distributed after the etched crystal.
单电畴铁电材料钛酸铅(PbTiO3)片状晶体选择性共沉积Au和MnOx：将已制备好的铁电材料钛酸铅晶体300mg放入50ml蒸馏水中，后向其中加入HAuCl4、MnSO4·H2O，使HAuCl4的含量为3wt％、MnSO4·H2O的含量为4wt％。该体系在氙灯下光沉积6h，得到样品用去离子水清洗并在80℃烘干。如图2(c)所示。Single-domain ferroelectric material lead titanate (PbTiO 3 ) plate crystal selective co-deposited Au and MnO x : 300 mg of prepared ferroelectric material lead titanate crystals were placed in 50 ml of distilled water, and then HAuCl 4 was added thereto. MnSO 4 ·H 2 O has a content of HAuCl 4 of 3 wt% and a content of MnSO 4 ·H 2 O of 4 wt%. The system was light deposited under a xenon lamp for 6 h, and the sample was washed with deionized water and dried at 80 °C. As shown in Figure 2 (c).
氢氟酸选择性刻蚀的单电畴铁电材料钛酸铅(PbTiO3)片状晶体的选择性共沉积Au和MnOx：将已制备好的(001)晶面表面凸起的钛酸铅晶体加入50ml蒸馏水中，后向其中加入HAuCl4、MnSO4·H2O，使HAuCl4的含量为3wt％、MnSO4·H2O的含量为4wt％。该体系在氙灯下光沉积6h，得到样品用去离子水清洗并在80℃烘干，如图3(c)所示。Selective co-deposition of Au and MnO x of single-domain ferroelectric material lead titanate (PbTiO 3 ) plate crystals by hydrofluoric acid selective etching: the prepared (001) crystal surface raised titanium titanate The lead crystals were added to 50 ml of distilled water, and then HAuCl 4 and MnSO 4 ·H 2 O were added thereto so that the content of HAuCl 4 was 3 wt%, and the content of MnSO 4 ·H 2 O was 4 wt%. The system was light deposited under a xenon lamp for 6 h, and the sample was washed with deionized water and dried at 80 ° C as shown in Figure 3 (c).
将图2(c)与图3(c)比较可以看出，经刻蚀后的晶体，表面沉积的Au和MnOx密度更大，分布更均匀。FIG 2 (c) and FIG. 3 (c) comparative As can be seen, larger crystals after etching, deposited on the surface of Au and MnO x density, more uniform distribution.
实施结果表明，本发明利用半导体铁电材料中的铁电场诱导表面带电属性的差异，导致带负电性的酸根离子优先选择性地吸附在带正电荷表面，可实现对铁电材料表面选择性刻蚀定向构筑异质结构光催化剂。光照下单电畴铁电材料钛酸铅纳米片状晶体在内建电场作用下载流子有效分离，光还原沉积金属Au和光氧化沉积MnOx可以选择性的发生在单电畴铁电材料钛酸铅片状晶体不同带电属性的(001)晶面上。氢氟酸选择性刻蚀的单电畴铁电材料钛酸铅(PbTiO3)片状晶体，在一面(001)晶面表面产生凸起生成TiO2纳米颗粒，通过选择
性沉积证实氢氟酸水溶液刻蚀钛酸铅晶体并未破坏其单电畴铁电特性。同时，钛酸铅(001)晶面表面的TiO2纳米颗粒凸起有助于提高(001)晶面的催化活性，进一步提高钛酸铅的光分解产氢效率。载流子有效分离和晶体表面光催化活性的提高，二者的有效结合使氢氟酸选择性刻蚀的单电畴铁电材料钛酸铅(PbTiO3)片状晶体的光催化活性大幅度提高，进一步为其它铁电基光催化材料或光电催化器件的设计提供重要参考。
The implementation results show that the invention utilizes the ferroelectric field in the semiconductor ferroelectric material to induce the difference in surface charging properties, so that the negatively charged acid ions are preferentially and selectively adsorbed on the positively charged surface, and the surface of the ferroelectric material can be selectively selectively engraved. The eccentricity constructs a heterostructure photocatalyst. Light-emitting single-domain ferroelectric material lead titanate nano-plate crystals built-in electric field effect downloading effective separation, photoreduction deposition of metal Au and photo-oxidation deposition of MnO x can selectively occur in single-domain ferroelectric material titanic acid Lead-like crystals have different charged properties on the (001) crystal plane. Hydrofluoric acid selectively etched single-domain ferroelectric material lead titanate (PbTiO 3 ) plate crystal, which generates protrusions on the surface of one side (001) crystal surface to form TiO 2 nanoparticles, and hydrofluoric acid is confirmed by selective deposition. Etching the lead titanate crystals in an aqueous solution does not destroy the single-domain ferroelectric properties. At the same time, the TiO 2 nanoparticle protrusion on the surface of the lead (001) crystal surface helps to improve the catalytic activity of the (001) crystal plane and further improve the photodegradation hydrogen production efficiency of lead titanate. The effective separation of carriers and the improvement of photocatalytic activity on the crystal surface, the effective combination of the two, the photocatalytic activity of the single-domain ferroelectric material lead titanate (PbTiO 3 ) plate crystals selectively etched by hydrofluoric acid is greatly improved. It further provides an important reference for the design of other ferroelectric-based photocatalytic materials or photocatalytic devices.
Claims (7)
- 一种选择性刻蚀铁电基光催化材料以定向构筑异质结构的方法，其特征在于：利用半导体铁电材料中的铁电场诱导表面带电属性的差异，导致带负电性的酸根离子优先选择性地吸附在带正电荷表面的特点，将半导体铁电材料放入含有刻蚀性酸的水溶液中，通过水热处理过程实现对铁电材料表面的选择性刻蚀，在铁电基体材料表面定向构筑异质结构。A method for selectively etching a ferroelectric-based photocatalytic material to orient a heterostructure, characterized in that a ferroelectric field in a semiconductor ferroelectric material is used to induce a difference in surface charging properties, resulting in preferential selection of a negatively charged acid ion Sexually adsorbed on a positively charged surface, the semiconductor ferroelectric material is placed in an aqueous solution containing an etchant acid, and the surface of the ferroelectric material is selectively etched by a hydrothermal treatment process to be oriented on the surface of the ferroelectric substrate. Construct a heterogeneous structure.
- 按照权利要求1所述的选择性刻蚀铁电基光催化材料以定向构筑异质结构的方法，其特征在于：所述的铁电材料为各种三元或三元以上金属化合物铁电材料。The method of selectively etching a ferroelectric-based photocatalytic material according to claim 1 for structuring a heterostructure, wherein the ferroelectric material is a ternary or ternary metal compound ferroelectric material. .
- 按照权利要求1所述的选择性刻蚀铁电基光催化材料以定向构筑异质结构的方法，其特征在于：优选的，所述的铁电材料为钛酸铅、钛酸钡或铁酸铋。A method of selectively etching a ferroelectric-based photocatalytic material according to claim 1 for directional construction of a heterostructure, characterized in that preferably, the ferroelectric material is lead titanate, barium titanate or ferric acid. bismuth.
- 按照权利要求1所述的选择性刻蚀铁电基光催化材料以定向构筑异质结构的方法，其特征在于：所述的刻蚀性酸为各种无机酸或其混合酸溶液。The method of selectively etching a ferroelectric-based photocatalytic material according to claim 1 for structuring a heterostructure, wherein the etchant acid is a mixture of various inorganic acids or mixed acid solutions.
- 按照权利要求1所述的选择性刻蚀铁电基光催化材料以定向构筑异质结构的方法，其特征在于：优选的，所述的刻蚀性酸为氢氟酸、盐酸、硫酸、硝酸之一或两种以上混合。The method of selectively etching a ferroelectric-based photocatalytic material according to claim 1, wherein the etchable acid is hydrofluoric acid, hydrochloric acid, sulfuric acid or nitric acid. One or more of them are mixed.
- 按照权利要求1所述的选择性刻蚀铁电基光催化材料以定向构筑异质结构的方法，其特征在于：所述的刻蚀性酸水溶液中，酸的摩尔浓度为0.1mM～5M。The method of selectively etching a ferroelectric-based photocatalytic material according to claim 1, wherein the molar concentration of the acid in the etchable acid aqueous solution is 0.1 mM to 5 M.
- 按照权利要求1所述的选择性刻蚀铁电基光催化材料以定向构筑异质结构的方法，其特征在于：所述的水热处理温度为30℃～300℃，水热处理时间为10min～96h。 The method of selectively etching a ferroelectric-based photocatalytic material according to claim 1 for structuring a heterostructure, wherein the hydrothermal treatment temperature is 30 ° C to 300 ° C, and the hydrothermal treatment time is 10 min to 96 h. .
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