CN110833836A - Two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheet prepared by hydrothermal method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of functionalized nanomaterials, and relates to a two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheet prepared by a hydrothermal method and an application thereof. Firstly, polyol, bismuth source and surfactant are mixed into a solution, then sodium chloride solution is added dropwise, the pH is adjusted to 10-13 with sodium hydroxide solution, and the reaction kettle is hydrothermally reacted at 140 ℃ to 180 ℃ for 2 to 12 hours, After cooling to room temperature, the product was centrifuged and washed with ethanol and deionized water in turn. The invention utilizes a one-step hydrothermal method to prepare two-dimensional ultra-thin materials. Compared with bulk materials, the prepared ultra-thin nanosheets have efficient photocatalytic carbon dioxide reduction performance, which not only provides new ideas for the design and synthesis of functional photocatalytic materials and The method also provides a new way to realize the efficient catalytic reduction of _CO , and provides a theoretical basis for the application of photocatalytic carbon dioxide reduction technology to solve environmental problems and energy shortages caused by the greenhouse effect. The invention has mild and controllable reaction conditions, simple operation, strong practicability, and is convenient for large-scale promotion.

Description

Preparation and application of two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheets by hydrothermal method

technical field

The invention belongs to the technical field of functionalized nanomaterials, and in particular relates to a two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheet prepared by a hydrothermal method and an application thereof.

Background technique

With the rapid development of the economy, human beings have an increasing demand for energy. At present, the most widely used fossil energy is still fossil energy. The use of fossil energy will produce carbon dioxide, sulfur dioxide, etc., carbon dioxide is a greenhouse gas, which will lead to rising global temperature and glaciers. Melting, which in turn makes sea level rise, and sulfur dioxide is the main cause of acid rain, in short, the use of fossil energy will cause serious environmental problems. In addition, fossil energy is increasingly exhausted, and it is urgent to develop and use new and clean energy.

At present, renewable clean energy mainly includes solar energy, hydrogen energy, tidal energy and wind energy. Solar energy is the most widely distributed and the largest renewable energy source. The total energy reaching the earth every second is approximately equal to the energy released by the burning of more than 5 million tons of coal. By using clean, non-polluting solar energy to reduce carbon dioxide to chemical fuels such as hydrocarbons or alcohols, not only the content of carbon dioxide in the atmosphere is reduced, but the resulting product can be recycled. Therefore, photocatalytic reduction of carbon dioxide has a good effect. prospect. The raw materials of this process are simple and easy to obtain, and the direct use of solar energy does not require auxiliary energy consumption, and can truly realize the recycling of carbon, so it is considered to be the most promising technology.

In the photocatalytic reduction of carbon dioxide, catalysts occupy an indispensable position, and catalysts with strong selectivity and high activity will make the utilization of solar energy higher, thereby improving the conversion efficiency of the reaction. Two-dimensional ultrathin nanosheets have a large specific surface area and can effectively promote redox reactions. At the same time, compared with bulk materials, more reactive sites can be exposed, which can effectively improve the catalytic activity of the reaction. Therefore, two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheet materials are expected to greatly improve the performance of photocatalytic reduction of carbon dioxide.

SUMMARY OF THE INVENTION

In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a method for preparing two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheets by a hydrothermal method.

A method for preparing a two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheet material by a hydrothermal method, comprising the following steps:

(1) Add deionized water into the polytetrafluoroethylene-lined reactor, add polyol, bismuth source, and surfactant to mix into a solution, wherein the polyol, bismuth source, surfactant, and deionized water The molar volume ratio is 2～300mmol: 0.5～1.5mmol: 4～16mmol: 25～40ml;

(2) Slowly add sodium chloride solution dropwise to maintain high-speed stirring, wherein the sodium chloride solution concentration is 6.2mmol/L, and the stirring speed is above 1000r/min; Preferably 11.85, stirring continuously for more than 10min; wherein, the sodium hydroxide solution is 2 mol/L; the volume ratio of the mixed solution, sodium chloride solution, and sodium hydroxide solution is 25～40ml: 1～5ml: 0.8～ 1.3ml, preferably 25ml:5ml:1ml;

(3) The reaction kettle is subjected to hydrothermal reaction at 140℃～180℃ for 2～12 hours, preferably 160℃ for 3 hours, cooled to room temperature, the product is centrifuged, and washed with ethanol and deionized water in turn to obtain two-dimensional ultrathin Bismuth-rich bismuth oxychloride nanosheets.

In the preferred disclosure example of the present invention, the polyhydric alcohol in step (1) is mannitol, ethylene glycol or glycerol, preferably mannitol.

In a preferred disclosure example of the present invention, the bismuth source in step (1) is bismuth nitrate, bismuth acetate, bismuth chloride, and bismuth sulfate, preferably bismuth nitrate.

In the preferred disclosure example of the present invention, the surfactant in step (1) is polyvinylpyrrolidone (PVP), cetyltrimethylammonium chloride, ionic liquid, preferably polyvinylpyrrolidone (PVP).

In the preferred disclosure example of the present invention, when the polyol in step (1) is mannitol, the bismuth source is bismuth nitrate, and the surfactant is polyvinylpyrrolidone, the molar volume ratio is 2.5mmol:1mmol:4mmol : 25mL.

The inventors found that when Bi(NO ₃ ) ₃ was added to water, the solution immediately turned into a white suspension, which was due to the hydrolysis of Bi(NO ₃ ) ₃ to form slightly soluble BiONO ₃ . However, when mannitol was added to the aqueous solution first, and then Bi(NO ₃ ) ₃ was added with constant stirring, a clear solution was formed, indicating that the bismuth ions in the solution were coordinated with mannitol to avoid the production of BiONO ₃ . This will be conducive to the uniform nucleation and growth of bismuth oxychloride in the later hydrothermal reaction, which is conducive to the formation of ultra-thin nanostructures. Ethylene glycol, glycerin, etc. can replace mannitol with similar effects. As a synthetic water-soluble polymer compound, polyvinylpyrrolidone (PVP) acts as a surfactant in the synthesis of nanomaterials. In the crystal growth process of nanomaterials, in order to reduce the surface energy of the system, PVP molecules can be strongly adsorbed on a certain crystal plane of the crystal, preventing more nanoparticles from adsorbing and growing on the crystal plane, thereby limiting the crystal in a certain crystal plane. The upward growth of individual crystals eventually leads to the formation of two-dimensional ultrathin structures. Cetyltrimethylammonium chloride and ionic liquid can replace PVP as a surfactant, which is beneficial to the formation of ultra-thin nanostructures of bismuth oxychloride.

According to the powder sample prepared by the present invention, the thickness of the ultra-thin nano-sheet is about 2-3 nm, which confirms that the nano-sheet has an ultra-thin structure.

The crystal structure and phase were studied by X-ray diffraction (XRD). As shown in Figure 1, the diffraction peaks of the sample can be indexed as Bi ₁₂ O ₁₇ Cl ₂ (JCPDS No.370702) in the tetragonal phase, usually oxychlorinated. The chemical formula of bismuth is BiOCl, so it is defined as rich in bismuth. The morphology and size of the samples were characterized by transmission electron microscopy (TEM). As shown in Fig. 2, the low-resolution TEM image shows a two-dimensional sheet-like morphology and almost transparent features, which indicates its ultra-thin nature with a size of around 100–200 nm. The thickness of the nanosheets was further analyzed by atomic force microscopy (AFM) images along with the corresponding height profiles.

Another object of the present application is to apply the prepared material to photocatalytic reduction of carbon dioxide.

The photocatalytic CO ₂ reduction activity of the obtained samples was evaluated by using the Beijing Porphyran labsolar-6a photocatalytic system: 30 mg of photocatalyst powder was suspended in 50 ml of water, and vigorously stirred at 1000 r/min until uniformly dispersed; Vacuum the instrument to keep the temperature of the reaction system at about 5°C to improve the solubility of CO ₂ ; pump pure CO ₂ gas into a 100ml reactor at a pressure of 0.08mpa, using a 300w xenon lamp as the light source, during the irradiation process , the gaseous products of photocatalytic _CO reduction were analyzed with a gas chromatograph (Cotrun GC2002, FID).

To verify the structural advantages of ultrathin nanosheets, _CO photocatalytic reduction experiments were performed to evaluate the photocatalytic activity of the synthesized samples, excluding the influence of sacrificial agents and cocatalysts. Gas chromatographic analysis showed that CO was the main product of Bi ₁₂ O ₁₇ Cl ₂ ultrathin nanosheets and Bi ₁₂ O ₁₇ Cl ₂ bulk, and no by-products such as CH ₄ and CH ₃ OH were detected. As shown in Fig. 4, the yield of CO gradually increases with the increase of irradiation time, and the conversion rate of Bi ₁₂ O ₁₇ Cl ₂ ultrathin nanosheets is about 64.3 μmol·g ^-1 ·h -1 , which is about 64.3 μmol·g -1 ·h ^-1 for Bi ₁₂ O ₁₇ Cl ₂ bulk material (2.3 μmol·g ^-1 ·h ^-1 ) is about 28 times larger. In the control experiments performed under dark, photocatalyst-free conditions, no CO signal was detected, confirming that CO was generated from the photocatalytic reduction of CO _on the photocatalyst.

beneficial effect

The invention utilizes a one-step hydrothermal method to prepare ultra-thin bismuth-rich bismuth oxychloride nanosheet materials with high specific surface area and more active sites. The inventors prepared the two-dimensional ultra-thin material by a simple one-step hydrothermal method by adjusting pH, reaction temperature, etc. Compared with the bulk material, the prepared ultra-thin nanosheets have efficient photocatalytic carbon dioxide reduction performance, which is not only a novel function The design and synthesis of photocatalytic materials provides new ideas and methods, and also provides a new way to achieve efficient catalytic reduction of CO ₂ , and provides a theoretical basis for the application of photocatalytic carbon dioxide reduction technology to solve environmental problems and energy shortages caused by the greenhouse effect. The method has mild and controllable reaction conditions, simple operation, strong practicability, and is convenient for large-scale promotion.

Description of drawings

Fig. 1. the X-ray powder diffraction analysis figure (XRD) of the two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheet material obtained by embodiment 1;

Figure 2. Low magnification field emission transmission image (TEM) of the two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheet material obtained in Example 1;

Figure 3. Atomic force microscopy (AFM) of the two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheet material obtained in Example 1;

Figure 4. Carbon dioxide reduction performance test of the two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheet material obtained in Example 1.

Detailed ways

The present invention will be described in detail below in conjunction with the examples, so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following examples.

Unless otherwise defined, terms (including scientific and technical terms) used herein should be interpreted to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will also be understood that terms used herein should be construed to have meanings consistent with their meanings in the context of this specification and related art and should not be interpreted in an idealized or excessive form unless expressly defined as such herein .

Example 1

A method for preparing a two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheet material by a hydrothermal method, comprising the following steps:

Add 25 mL of deionized water to 50 mL of Teflon lining, keep stirring, add 0.455 g of mannitol, add 0.486 g of bismuth nitrate pentahydrate after complete dissolution, add 0.400 g of polyvinylpyrrolidone after complete dissolution, and then slowly add 5mL contains 0.059 g sodium chloride solution, and 2 mol/L sodium hydroxide solution is added to adjust the pH value of the solution to 11.85. The obtained solution was put into the reaction kettle and then put into an oven, heated at 160 °C for 3 h. The obtained suspension was kept at 13,000 rpm for 3 min with a high-speed centrifuge to separate the solid and liquid, and the solid collection was washed three times with ethanol and deionized water to obtain a two-dimensional ultra-thin bismuth-rich oxychloride. Bismuth nanosheet material.

The obtained two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheets were subjected to _CO2 photocatalytic reduction experiments. With the increase of irradiation time, the yield of _CO gradually increased, and _{the Bi12O17Cl2} ultrathin nanosheets The conversion rate was about 64.1 μmol·g ^-1 ·h ^-1 .

Example 2

A method for preparing a two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheet material by a hydrothermal method, comprising the following steps:

Add 15 mL of deionized water to 25 mL of Teflon lining, keep stirring, add 0.228 g of mannitol, add 0.243 g of bismuth nitrate pentahydrate after complete dissolution, add 0.200 g of polyvinylpyrrolidone after complete dissolution, and then slowly add 2.5mL contains 0.059 g sodium chloride solution, add 2 mol/L sodium hydroxide solution to adjust the pH value of the solution to 11.85. The obtained solution was put into the reaction kettle and then put into an oven, heated at 160 °C for 3 h. The obtained suspension was kept at 13,000 rpm for 3 min with a high-speed centrifuge to separate the solid and liquid, and the solid collection was washed three times with ethanol and deionized water to obtain a two-dimensional ultra-thin bismuth-rich oxychloride. Bismuth nanosheet material.

The obtained two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheets were subjected to _CO2 photocatalytic reduction experiments. With the increase of irradiation time, the yield of _CO gradually increased, and _{the Bi12O17Cl2} ultrathin nanosheets The conversion rate was about 65.0 μmol·g ^-1 ·h ^-1 .

Example 3

A method for preparing a two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheet material by a hydrothermal method, comprising the following steps:

Add 50 mL of deionized water to 100 mL of Teflon lining, keep stirring, add 0.900 g of mannitol, add 0.972 g of bismuth nitrate pentahydrate after complete dissolution, add 0.800 g of polyvinylpyrrolidone after complete dissolution, and then slowly add 10 mL contains 0.059 g sodium chloride solution, and 2 mol/L sodium hydroxide solution is added to adjust the pH value of the solution to 11.85. The obtained solution was put into the reaction kettle and then put into an oven, heated at 160 °C for 3 h. The obtained suspension was kept at 13,000 rpm for 3 min with a high-speed centrifuge to separate the solid and liquid, and the solid collection was washed three times with ethanol and deionized water to obtain a two-dimensional ultra-thin bismuth-rich oxychloride. Bismuth nanosheet material.

The obtained two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheets were subjected to _CO2 photocatalytic reduction experiments. With the increase of irradiation time, the yield of _CO gradually increased, and _{the Bi12O17Cl2} ultrathin nanosheets The conversion rate was about 61.2 μmol·g ^-1 ·h ^-1 .

Example 4

A method for preparing a two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheet material by a hydrothermal method, comprising the following steps:

(1) Add deionized water into the polytetrafluoroethylene-lined reaction kettle, add mannitol, bismuth acetate, and polyvinylpyrrolidone, respectively, and mix them into a solution. The moles of the polyol, bismuth source, surfactant, and deionized water are The volume ratio is 2.5mmol: 1mmol: 4mmol: 25ml;

(2) Slowly add sodium chloride solution dropwise to maintain high-speed stirring, wherein the sodium chloride solution concentration is 6.2 mmol/L, and the stirring speed is above 1000 r/min; continue to drop sodium hydroxide solution, adjust pH to 11.85, and continue stirring more than 10 min; the sodium hydroxide solution is 2 mol/L; the volume ratio of the mixed solution, the sodium chloride solution, and the sodium hydroxide solution is 25ml:5ml:1ml;

(3) The reaction kettle was hydrothermally reacted at 160 °C for 3 hours, cooled to room temperature, the product was centrifuged, and washed with ethanol and deionized water in turn to obtain two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheets.

The obtained two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheets were subjected to _CO2 photocatalytic reduction experiments. With the increase of irradiation time, the yield of _CO gradually increased, and _{the Bi12O17Cl2} ultrathin nanosheets The conversion rate was about 58.3 μmol·g ^-1 ·h ^-1 .

Example 5

A method for preparing a two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheet material by a hydrothermal method, comprising the following steps:

(4) Add deionized water into the polytetrafluoroethylene-lined reaction kettle, add mannitol, bismuth sulfate, and polyvinylpyrrolidone respectively, and mix them into a solution. The moles of the polyol, bismuth source, surfactant, and deionized water are The volume ratio is 2.5mmol: 1mmol: 4mmol: 25ml;

(5) Slowly add sodium chloride solution dropwise to maintain high-speed stirring, wherein the sodium chloride solution concentration is 6.2mmol/L, and the stirring speed is above 1000r/min; continue to drop sodium hydroxide solution, adjust pH to 11.85, and continue stirring more than 10 min; the sodium hydroxide solution is 2 mol/L; the volume ratio of the mixed solution, the sodium chloride solution, and the sodium hydroxide solution is 25ml:5ml:1ml;

(6) The reaction kettle was hydrothermally reacted at 160°C for 3 hours, cooled to room temperature, the product was centrifuged, and washed with ethanol and deionized water in turn to obtain two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheets.

The obtained two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheets were subjected to _CO2 photocatalytic reduction experiments. With the increase of irradiation time, the yield of _CO gradually increased, and _{the Bi12O17Cl2} ultrathin nanosheets The conversion rate was about 65.7 μmol·g ^-1 ·h ^-1 .

Example 6

A method for preparing a two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheet material by a hydrothermal method, comprising the following steps:

(7) Deionized water is added to the polytetrafluoroethylene-lined reactor, and glycerol, bismuth nitrate, and polyvinylpyrrolidone are respectively added to mix into a solution. The molar volume of the polyol, bismuth source, surfactant, and deionized water is The ratio is 300mmol: 1mmol: 4mmol: 25ml;

(8) Slowly add sodium chloride solution dropwise to maintain high-speed stirring, wherein the sodium chloride solution concentration is 6.2 mmol/L, and the stirring speed is above 1000 r/min; continue to drop sodium hydroxide solution, adjust pH to 11.85, and continue stirring more than 10 min; the sodium hydroxide solution is 2 mol/L; the volume ratio of the mixed solution, the sodium chloride solution, and the sodium hydroxide solution is 25ml:5ml:1ml;

(9) The reaction kettle was hydrothermally reacted at 160°C for 3 hours, cooled to room temperature, the product was centrifuged, and washed with ethanol and deionized water in turn to obtain two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheets.

The obtained two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheets were subjected to _CO2 photocatalytic reduction experiments. With the increase of irradiation time, the yield of _CO gradually increased, and _{the Bi12O17Cl2} ultrathin nanosheets The conversion rate is about 60.5μmol·g ^-1 ·h ^-1 .

Example 7

A method for preparing a two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheet material by a hydrothermal method, comprising the following steps:

(10) Deionized water was added to the polytetrafluoroethylene-lined reaction kettle, and mannitol, bismuth nitrate, and cetyltrimethylammonium chloride were respectively added and mixed into a solution. The polyol, bismuth source, surface active The molar volume ratio of the agent and deionized water is 300mmol: 1mmol: 2mmol: 25ml;

(11) Slowly add sodium chloride solution dropwise to maintain high-speed stirring, wherein the sodium chloride solution concentration is 6.2 mmol/L, and the stirring speed is above 1000 r/min; continue to drop sodium hydroxide solution, adjust pH to 11.85, and continue stirring more than 10 min; the sodium hydroxide solution is 2 mol/L; the volume ratio of the mixed solution, the sodium chloride solution, and the sodium hydroxide solution is 25ml:5ml:1ml;

(12) The reaction kettle was hydrothermally reacted at 160°C for 3 hours, cooled to room temperature, the product was centrifuged, and washed with ethanol and deionized water in turn to obtain two-dimensional ultra-thin bismuth-rich bismuth oxychloride nanosheets.

The obtained two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheets were subjected to _CO2 photocatalytic reduction experiments. With the increase of irradiation time, the yield of _CO gradually increased, and _{the Bi12O17Cl2} ultrathin nanosheets The conversion rate is about 62.3 μmol·g ^-1 ·h ^-1 .

The above descriptions are only the embodiments of the present invention, and are not intended to limit the scope of the patent of the present invention. Any equivalent structure or equivalent process transformation made by the description of the present invention, or directly or indirectly applied in other related technical fields, are the same as The principles are included in the scope of patent protection of the present invention.

Claims (10)

1. A method for preparing a two-dimensional ultrathin bismuth-rich bismuth oxychloride nanosheet material by a hydrothermal method is characterized by comprising the following steps:

(1) adding deionized water into a polytetrafluoroethylene lining reaction kettle, respectively adding polyol, a bismuth source and a surfactant, and mixing to obtain a solution, wherein the molar volume ratio of the polyol to the bismuth source to the surfactant to the deionized water is (2-300 mmol): 0.5-1.5 mmol: 4-16 mmol: 25-40 ml;

(2) slowly dropwise adding a sodium chloride solution, and keeping stirring at a high speed, wherein the concentration of the sodium chloride solution is 6.2mmol/L, and the stirring speed is more than 1000 r/min; continuously dropwise adding a sodium hydroxide solution, adjusting the pH value to 10-13, and continuously stirring for more than 10 min; wherein the sodium hydroxide solution is 2 mol/L; the volume ratio of the mixed solution to the sodium chloride solution to the sodium hydroxide solution is 25-40 ml: 1-5 ml: 0.8-1.3 ml;

(3) and carrying out hydrothermal reaction for 2-12 h at 140-180 ℃ in the reaction kettle, cooling to room temperature, centrifuging a product, and sequentially washing with ethanol and deionized water to obtain the catalyst.

2. The hydrothermal process of claim 1, wherein: the polyhydric alcohol in the step (1) is mannitol, ethylene glycol or glycerol, and preferably mannitol.

3. The hydrothermal process of claim 1, wherein: in the step (1), the bismuth source is bismuth nitrate, bismuth acetate, bismuth chloride and bismuth sulfate, and bismuth nitrate is preferred.

4. The hydrothermal process of claim 1, wherein: the surfactant in the step (1) is polyvinylpyrrolidone, hexadecyl trimethyl ammonium chloride and ionic liquid, preferably polyvinylpyrrolidone.

5. The hydrothermal process of claim 1, wherein: when the polyhydric alcohol is mannitol, the bismuth source is bismuth nitrate and the surfactant is polyvinylpyrrolidone in the step (1), the molar volume ratio is 2.5 mmol: 1 mmol: 4 mmol: 25 mL.

6. The hydrothermal process of claim 1, wherein: and (3) continuously dropwise adding the sodium hydroxide solution in the step (2), adjusting the pH value to 11.85, and continuously stirring for more than 10 min.

7. The hydrothermal process of claim 1, wherein: the volume ratio of the mixed solution, the sodium chloride solution and the sodium hydroxide solution in the step (2) is 25ml to 5ml to 1 ml.

8. The hydrothermal process of claim 1, wherein: and (3) carrying out hydrothermal reaction on the reaction kettle for 3 hours at the temperature of 160 ℃.

9. The two-dimensional ultrathin bismuth-rich oxychloride nanosheet material prepared by the method of any one of claims 1 to 8, wherein: the thickness of the ultrathin nanosheet is about 2-3 nm.

10. The use of the two-dimensional ultrathin bismuth oxychloride nanosheet material as defined in claim 9, wherein: it is applied to photocatalytic reduction of carbon dioxide.

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