Novel oxysulfide and light absorption regulation and control method thereof

Abstract

The invention provides a novel oxysulfide and a light absorption property regulation and control method thereof, the chemical formula of the novel oxysulfide is SrGaSbO3S, the novel oxysulfide belongs to an orthorhombic system Pnma, has a two-dimensional layered structure, and is formed by alternately stacking [GaSbO3S] < 2-> and interlayer Sr < 2 + > ions. The material is placed in molten alkali metal halide for annealing treatment, and an amorphous layer is formed on the surface due to ion topology corrosion, so that the optical band gap of the material is obviously narrowed and is reduced to 1.69 eV from 2.11 eV, and the color is changed into orange from light yellow. The oxysulfide and the band gap regulation and control method thereof have important significance in application in the fields of photocatalysis, photoelectric conversion and the like.

Description

Technical Field

[0001] This invention belongs to the field of inorganic materials, specifically relating to a method for preparing inorganic oxygen sulfide crystals and regulating their light absorption. Background Technology

[0002] Oxysulfides are a promising class of heteroanionic compounds, characterized by the simultaneous presence of O in their crystal structure. 2⁻ and S 2⁻ Two anions. These oxysulfides, with their different structural dimensions, have become ideal candidate materials for numerous applications, ranging from quantum materials such as superconductors to functional materials such as optoelectronics, thermoelectric conversion, and nonlinear optics (NLO). They exhibit unique coordination chemistry properties, stemming from the formation of heteroanions [MO] promoted by metal ions (M) with suitable bonding preferences. x S y ] Element. Furthermore, by using highly electronegative cations (such as alkali metal ions A... + Alkaline earth metal ions (Ae) 2+ and rare earth metal ions Ln 3+ By introducing these building blocks as structural templates into these compounds, the spatial arrangement and connection modes of these building blocks can be effectively controlled. This method can further increase the diversity of structures and bonding, thus paving the way for the structural and functional design of oxysulfide systems.

[0003] With the energy crisis and environmental problems becoming increasingly prominent, visible light, as a clean and renewable new energy source, has become a research hotspot in the field of materials science due to its efficient capture and conversion. The light absorption properties of oxysulfides and their heteroanions [MO]... x S y The electronic structure of the basic unit is closely related, O 2⁻ and S 2⁻ The electronegativity difference and orbital interactions allow for flexible adjustment of the band structure of oxysulfides through structural modulation. This can be achieved by optimizing the type of metal ion M and regulating [MO]. x S yBy adjusting the O / S ratio in the basic unit, introducing appropriate doping elements and structural templates, and controlling the surface composition (such as adjusting the surface O / S element ratio, modifying functional surface species, and constructing surface heterostructures), the light absorption range of oxysulfides can be precisely controlled, expanding it into the visible light region. Simultaneously, the surface light absorption efficiency and the surface separation characteristics of photogenerated carriers can be optimized, further improving the capture and utilization efficiency of visible light. Furthermore, rationally controlling the crystal structure and electronic state distribution of oxysulfides can reduce the recombination probability of photogenerated carriers, enhance the separation and transport capabilities of photogenerated charges, and thus improve their energy conversion performance under visible light drive. This lays the foundation for their practical applications in solar photocatalytic water splitting, visible light photoelectric conversion, and photothermal conversion, promoting the efficient utilization and development of clean and renewable energy. Summary of the Invention

[0004] This invention proposes a novel method for preparing oxysulfide crystals and regulating their light absorption.

[0005] In a first aspect, the present invention provides a novel oxysulfide SrGaSbO3S, belonging to the orthorhombic crystal system, with space group [missing information]. Pnma The oxysulfide has a layered structure, consisting of [GaSbO3S]. 2- Anion layer and Sr 2+ Alternating cation layers are stacked to form a two-dimensional layer, wherein [GaSbO3S] 2- The layer is composed of [GaO2S2]. 3- Tetrahedral chains and [SbO3] 2- The triangular pyramids are connected by sharing a common vertex. Among them, [GaO2S] 3- The chain is composed of [GaO2S2]. 5- Tetrahedra are formed by sharing a common vertex S atom. Adjacent [GaO2S] 3- The chains are connected by [SbO3]. 3- The groups are interconnected and share O atoms.

[0006] Secondly, the present invention provides a method for preparing the above-mentioned novel oxygen sulfide, comprising placing raw materials containing Sr, Ga, Sb, O and S elements under vacuum conditions, holding them at 600-800°C for more than 24 hours, and then cooling them down.

[0007] The molar ratio of Sr, Ga, Sb, O, and S in the raw material is (1~1.5):1:1:(3~3.5):1.

[0008] The high-temperature reaction may include heating from room temperature to 600-800°C within 10 hours.

[0009] The high-temperature reaction may include heating to 700-800°C and holding at that temperature for 24-72 hours, then cooling to 500°C within 24-72 hours, and then naturally cooling to room temperature.

[0010] In the above preparation process, fluxes can be added to the reaction raw materials. Fluxes include, but are not limited to, alkali metal halides such as KCl, KI, RbCl, CsI, etc., to promote crystal growth.

[0011] Thirdly, the present invention provides a surface modification method for the above-mentioned oxysulfide, namely, annealing the material in a molten alkali metal halide flux to regulate the light absorption properties of the material.

[0012] The annealing process described herein includes, but is not limited to, AX (A = Na, K, Rb, Cs; X = Cl, Br, I).

[0013] The annealing process includes heating to 700-800°C at a rate of 70-80°C / hour.

[0014] The annealing process includes holding at the target temperature for 6 to 48 hours, followed by rapid cooling to room temperature.

[0015] Fourthly, the present invention provides a use of the above-mentioned oxygen sulfide for photocatalytic decomposition of water and degradation of organic pollutants.

[0016] In summary, this invention provides an oxygen sulfide with a novel crystal structure and a method for controlling its light absorption properties. This novel oxygen sulfide, SrGaSbO3S, has a two-dimensional layered structure, consisting of [GaSbO3S]. 2- Anion layer and Sr 2+ The material is formed by alternating stacks of cation layers. Annealing it in a molten alkali metal halide flux induces a crystalline-to-amorphous transition on the crystal surface. After this treatment, the band gap of the material significantly narrows, decreasing from approximately 2.11 eV to approximately 1.69 eV, while its crystal morphology changes from an initial rod-like shape to a unique beak-like end morphology. This invention provides an effective strategy for precisely controlling the surface states, electronic structure, and crystal morphology of heteroanionic materials through topological dissolution, and holds promise for photocatalytic water splitting and degradation of organic pollutants. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the crystal structure of the novel oxygen sulfide SrGaSbO3S of this invention; Figure 2 The powder X-ray diffraction pattern and ultraviolet-visible diffuse reflectance pattern of the novel oxygen sulfide SrGaSbO3S of this invention are shown below. Figure 3The images show powder X-ray diffraction patterns of the novel oxygen sulfide SrGaSbO3S after annealing, as well as comparisons of the band gaps of SrGaSbO3S after annealing at different times, theoretically calculated SrGaSbO3S, and the original untreated SrGaSbO3S.

[0018] Figure 4 This is a schematic diagram of the novel oxygen sulfide SrGaSbO3S of the present invention and SrGaSbO3S with a unique beak-like end morphology after annealing. Figure 5 GaSbO3S with a unique beak-like end morphology after annealing 3+ In-depth analysis of XPS charts; Figure 6 The images show the photocatalytic degradation of Rhodamine B before and after SrGaSbO3S surface treatment. Detailed Implementation

[0019] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0020] Implementation Form 1 The oxygen sulfide SrGaSbO3S in this embodiment belongs to the orthorhombic crystal system, space group [space group missing]. Pnma Composed of [GaSbO3S] 2- Anion layer and Sr 2+ The crystal structure is formed by alternating stacked cation layers, with Sr, Ga, Sb, O, and S having oxidation states of +2, +3, +3, -2, and -2, respectively. [GaSbSO3] 2- The layer is composed of [GaO2S2]. 3- Tetrahedral chains and [SbO3] 2- The triangular pyramids are connected by sharing a common vertex. Among them, [GaO2S] 3- The chain is composed of [GaO2S2]. 5- Tetrahedra are formed by sharing a common vertex S atom. Adjacent [GaO2S] 3- The chains are connected by [SbO3]. 3- The groups are interconnected and share O atoms. The cell parameters of SrGaSbO3S are... a = 5.9472(5) Å, b =5.5610(5), c = 15.0969(14) Å, α = β = γ = 90°, Z = 2, and its crystallographic data are shown in Table 1.

[0021] Table 1 Crystallographic data of SrGaSbO3S Molecular formula <![CDATA[SrGaSbO3S]]> molecular weight 718.30 Space Group Pnma a (Å) 5.9472(5) b (Å) 5.5610(5) c (Å) 15.0969(14) <![CDATA[Volume (Å 3 )]]> 499.29(8) <![CDATA[Density (g·cm -3 )]]> 4.778 The following is an exemplary description of the preparation method of the novel oxygen sulfide SrGaSbO3S of the present invention.

[0022] Step 1: Weigh 0.1197 g of strontium sulfide, 0.0937 g of gallium trioxide, 0.1458 g of antimony trioxide, and 1.000 g of cesium iodide, mix them thoroughly, and grind them evenly. The reaction vessel can be a quartz tube. This tube should be kept at 10... −3 Under a vacuum of mbar, the sample is flame-sealed and placed in a muffle furnace. The temperature is increased to 800 °C at a rate of 156 °C / hour using a high-temperature solid-state reaction method. After reaching 800 °C, the temperature is held for 48 hours and then cooled to 20 °C at a rate of 32.5 °C / hour. This process enables the growth of larger crystal sizes.

[0023] Step 2: The mixture obtained in Step 1 was first washed with deionized water, and then treated with acetone. After drying, rod-shaped SrGaSbO3S crystals were obtained.

[0024] Implementation Form 2 This embodiment describes a surface modification method for SrGaSbO3S, which involves using high-temperature molten salt annealing to induce a transformation from a crystalline to an amorphous state on the sample surface. By reconstructing the surface, the light absorption properties of the material are modulated, thereby significantly enhancing its ability to absorb visible light.

[0025] The following describes an exemplary method for surface modification of the oxysulfides of the present invention.

[0026] Step 1: The obtained rod-shaped SrGaSbO3S crystals are mixed with molten alkali metal halide flux AX (A = Na, K, Rb, Cs; X = Cl, Br, I) at a molar ratio of 1:3. The mixture is sealed in a quartz tube under vacuum, heated to 750 °C for 10 hours, then maintained for 6, 24, or 48 hours, and finally rapidly cooled to room temperature.

[0027] Step 2: The mixture obtained in Step 1 is first washed with deionized water, and then treated with acetone. After drying, SrGaSbO3S with an amorphous layer covering the surface and a unique beak-like tip is obtained.

[0028] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0029] In the following embodiments, unless otherwise specified, the reagents, materials and instruments used are all conventional reagents, materials and instruments, and are commercially available. The reagents involved can also be synthesized by conventional synthesis methods.

[0030] Example 1 Weigh out 0.1197 g of strontium sulfide, 0.0937 g of gallium trioxide, 0.1458 g of antimony trioxide, and 1.000 g of cesium iodide, mix them thoroughly and grind them evenly. Place the mixture in a quartz tube and heat it at 10°C. −3 The quartz tube was then flame-sealed under a vacuum of mbar. It was subsequently placed in a muffle furnace and heated to 800°C at a rate of 156°C / hour using a high-temperature solid-state reaction method. After reaching 800°C, the temperature was held for 48 hours, and then cooled to 20°C at a rate of 32.5°C / hour. The product was removed from the quartz tube, washed with deionized water, and then treated with acetone. After drying, rod-shaped SrGaSbO3S crystals were obtained.

[0031] Example 2 Physical property characterization: (1) The structure of the sample prepared in Example 1 was characterized by single-crystal X-ray diffraction, and the structural analysis results are as follows: Figure 1 As shown. Figure 1 This is a structural diagram of the novel oxysulfide SrGaSbO3S prepared in Example 1. As can be seen from the diagram, SrGaSbO3S has a layered structure, consisting of [GaSbO3S]. 2- Anion layer and Sr 2+ The cation layers are formed by alternating stacking.

[0032] (2) The phase composition and crystallinity of the sample prepared in Example 1 were measured using a powder X-ray diffractometer. The scanning rate and range were 5.6 ° / min and 10-70 °, respectively. The scanning results are as follows: Figure 2 As shown in figure a. The band gap of the SrGaSbO3S crystal was determined using ultraviolet-visible diffuse reflectance spectroscopy, and the characterization results are as follows. Figure 2 As shown in b.

[0033] Example 3 0.1 g of SrGaSbO3S crystals were weighed and mixed with CsI at a molar ratio of 1:3. The mixture was sealed in a quartz tube under vacuum and heated to 750 °C for 10 hours, then maintained for 48 hours, and finally rapidly cooled to room temperature. After breaking the quartz tube, the resulting mixture was first washed with deionized water and then treated with acetone. After drying, SrGaSbO3S with an amorphous layer covering the surface and a unique beak-like tip was obtained.

[0034] Example 4 Physical property characterization: (1) The phase composition and crystallinity of the sample prepared in Example 3 were measured using a powder X-ray diffractometer. The scanning rate and range were 5.6 ° / min and 10 -70 °, respectively. Figure 3 (a) X-ray diffraction was used to measure the phase composition and crystallinity of SrGaSbO3S with a unique beak-shaped amorphous surface prepared in Example 3. It can be seen that no additional peaks appeared in the spectrum after annealing, indicating that this process has topological properties. (2) The band gap of SrGaSbO3S crystals after annealing for different times was determined by UV-Vis diffuse reflectance spectroscopy, and the characterization results are as follows. Figure 3 As shown in (b), it can be seen from the figure that the band gap of the crystal gradually decreases as the annealing time increases.

[0035] (3) Figure 4 (a) is a schematic diagram of the morphological changes of SrGaSbO3S before and after annealing. It can be seen that after annealing, the original regular sheet-like shape was transformed into crystals with unique beak-like ends. Figure 4 (b) shows the morphology of the SrGaSbO3S sample prepared in Example 1 as characterized by transmission electron microscopy. It can be seen that the sample has clear lattice fringes. Figure 4 (c) shows the morphology of the annealed SrGaSbO3S sample prepared in Example 1 as characterized by transmission electron microscopy. It can be seen that the lattice fringes on the sample surface are not particularly clear. This is because Ga... 3+ Dissolution on the crystal surface parallel to the b-axis leads to the transformation of the crystal into an amorphous state.

[0036] (4) Figure 5 Using Ar + The XPS analysis image of the surface of the SrGaSbO3S crystal after etching and annealing shows that Ga... 3+ As etching time increased, the intensity changed systematically, indicating that the Ga on the crystal surface after annealing... 3+ Dissolution behavior.

[0037] Example 5 Performance Testing of Photocatalytic Degradation of Organic Dyes by SrGaSbO3S Oxysulfide and its Surface-Modified Products (1) Catalyst sample: Raw SrGaSbO3S sample (the product of claim 1, prepared by the method of claim 2 or 3) Modified SrGaSbO3S sample (prepared by the method described in claim 4 or 5: SrGaSbO3S crystal and CsI are mixed at a mass ratio of 1:0.5, vacuum sealed in a quartz tube, kept at 750℃ for 24 h and then quenched, washed with deionized water and acetone and then vacuum dried) (2) Target pollutant: Rhodamine B (RhB, analytical grade), prepared as a 10 mg / L aqueous solution as a simulated organic pollutant.

[0038] (3) Light source: 300 W xenon lamp (equipped with AM 1.5G filter to simulate sunlight, visible light wavelength range 400–780 nm).

[0039] (4) Experimental steps For dark adsorption equilibrium, 50 mg of the original SrGaSbO3S sample and the modified SrGaSbO3S sample were weighed and added to 50 mL of a 10 mg / L Rhodamine B aqueous solution. The mixture was magnetically stirred at 300 rpm for 30 min in the dark to allow the dye molecules to reach adsorption-desorption equilibrium on the catalyst surface.

[0040] The photocatalytic degradation reaction was carried out under a 300W xenon lamp, with the distance between the light source and the liquid surface maintained at 15 cm, and under continuous stirring. Samples were taken at 0, 10, 20, 30, 40, and 50 min of illumination. After filtering through a 0.22 μm aqueous filter membrane, the absorbance was measured at the characteristic wavelength of 554 nm using a UV-Vis spectrophotometer.

[0041] Concentration calculation is based on the Lambert-Beer law, converting absorbance values ​​into dye concentration. The dye residue rate is represented by the ratio of observed concentration to initial concentration (C / C0), which is used to evaluate the photocatalytic degradation efficiency.

[0042] (5) Experimental Results and Analysis Dark adsorption stage: After stirring in the dark for 30 min, the residual concentration of Rhodamine B in both the original and modified samples remained above 95%, indicating that the effect of dark adsorption on the degradation process is negligible.

[0043] Visible light degradation stage: The original SrGaSbO3S sample: after 50 min of visible light irradiation, the Rhodamine B residue rate was about 12%, and the degradation efficiency was 88%.

[0044] Modified SrGaSbO3S sample: After 50 min of visible light irradiation, the Rhodamine B residue rate dropped to below 1%, and the degradation efficiency exceeded 99%; at 20 min, a degradation rate of about 80% was achieved, showing superior visible light photocatalytic activity.

[0045] Reasons for performance differences: The photocatalytic performance of the modified sample is significantly improved because the surface amorphization treatment described in claim 4 reduces the optical band gap of the material, thereby greatly improving the efficiency of capturing and utilizing visible light.

[0046] (6) Conclusion This embodiment demonstrates that the SrGaSbO3S oxysulfide described in claim 1 has the performance of visible light photocatalytic degradation of organic dyes. After surface modification by the methods described in claims 4-5, its catalytic efficiency is significantly improved, and it can be applied to the field of photocatalytic degradation of organic pollutants.

Claims

1. A novel oxysulfide, characterized in that: (1) Its chemical formula is SrGaSbO3S, which belongs to the orthorhombic crystal system. Pnma Space group. (2) From [GaSbO3S] 2- Interlayer Sr 2+ It is formed by alternating stacking of ions. (3) The valence state of Sr is +2, the valence state of Sb is +3, the valence state of Ga is +3, the valence state of O is -2, and the valence state of S is -2.

2. A method for preparing the oxysulfide according to claim 1, characterized in that: Raw materials containing Sr, Ga, Sb, O, and S elements are placed under vacuum and kept at 600–800°C for more than 24 hours before being cooled.

3. The preparation method according to claim 2, characterized in that, Includes the following steps: (1) In a glove box, strontium sulfide, antimony trioxide, gallium trioxide and cesium iodide are mixed and ground evenly and put into a quartz tube. After vacuum sealing, the mixture is heated to 700 ~ 800 °C and kept at this temperature for more than 24 hours before cooling down. (2) The product obtained in step one is first washed with deionized water, then treated with acetone, and dried to obtain the material.

4. A method for surface modification of oxysulfides according to claim 1, characterized in that, Selective leaching of ions from the material surface leads to surface amorphization, significantly reducing the material's optical band gap.

5. The surface modification method according to claim 4, characterized in that, Includes the following steps: (1) Mix SrGaSbO3S crystal with one or more of the alkali metal halides AX (A = Na, K, Rb, Cs; X = Cl, Br, I), seal the mixture in a quartz tube under vacuum, heat to 700 ~ 800 ℃, maintain for 6 ~ 48 hours, and finally cool rapidly to room temperature. (2) The mixture obtained in step one is first washed with deionized water, then treated with acetone, and dried to obtain the modified material.

6. The application of the oxysulfide according to any one of claims 1 to 5 in photocatalytic water splitting and degradation of organic pollutants.

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