CN101602008B - Nano-material composite visible light catalyst and preparation method thereof - Google Patents

Abstract

The invention discloses a novel nano-material composite visible light catalyst and a preparation method thereof, and belongs to the field of fine chemicals. The catalyst comprises the following components in percentage by weight: 0.5 to 5 percent of elemental silver, 5 to 9.5 percent of silver halide, and 90 percent of mesoporous molecular sieve MCM-41 as a carrier. The catalyst has a novel shell-core nanometer structure, and is a visible light catalyst based on metal plasma effect and semiconductor photocatalytic effect. The catalyst is applicable to the fields of environmental pollution control and new energy development, has significant effects of degrading pollutants in water and producing hydrogen through water photolysis, is a catalytic material meeting the requirements of protecting environment and saving energy, overcomes the disadvantages that the prior photocatalyst is poor in the utilization ratio of visible light, low in catalytic activity, difficult to recycle and the like, and is worthy to be developed and applied.

Description

A kind of nano-material composite visible light catalyst and preparation method thereof

Technical field

The present invention relates to a kind of NEW TYPE OF COMPOSITE nanometer visible light catalyst and preparation method thereof, relate in particular to a kind of with the mesopore molecular sieve be carrier have visible light catalyst of shell/nuclear structure and preparation method thereof, belong to field of fine chemical.

Background technology

Semi-conductive multiphase photocatalysis process can at room temperature react, can directly utilize sunshine with it, can be special performances such as mineral products such as carbon dioxide, water, non-secondary pollution with the majority of organic pollutants oxidation Decomposition, be considered to a kind of ideal environment pollution control technology.By solar photolysis water hydrogen, solar energy is stored with the form of fuel hydrogen, and realizes that luminous energy is catalysis material to chemical conversion of energy key.Concerning photocatalytic hydrogen production by water decomposition, the current subject matter that faces is quantum yield (system absorbs the number of certain incident that each photon causes) and to visible light-responded.The key that addresses this problem is exactly selection of catalysts and preparation.The key of conductor photocatalysis technology is efficient, the cheap visible light catalyst of preparation.Traditional following deficiency of conductor photocatalysis material ubiquity: photoelectric transformation efficiency is low, only can absorb shortcomings such as ultraviolet ray; Also there is following deficiency in the existing visible light responsive photocatalyst of having developed: not high, the easy inactivation of quantum efficiency and photochemical corrosion, load and problems such as regeneration and preparation cost.At present means such as mainly compound by surface modification, semiconductor, element doping of prior art and ion injection improve its photocatalytic activity.Therefore, exploring and develop that (or sunshine) novel photocatalysis material is the effective way that improves solar energy utilization ratio in various efficient, stable, the low-cost visible-ranges, is the key of conductor photocatalysis hydrogen production by water decomposition technical development.

Summary of the invention

The object of the present invention is to provide the novel nano composite visible light catalyst that a kind of catalytic efficiency height, stable in properties, cost are low, be easy to separate, another purpose is to provide its preparation method.

The present invention is based on nano metal plasma resonance effect and conductor photocatalysis effect, improve catalytic stability, strengthen, improve quantum yield and the visible light-responded the object of the invention that reaches greatly visible absorption by core-shell structure.Technical scheme is as follows: with mesopore molecular sieve MCM-41 is catalyst carrier, and simple substance silver is core, has the Ag@AgX of core-shell structure as the photochemical catalyst main part for shell, silver halide.Each composition percentage by weight is: 0.5%-5% silver, 5%-9.5% silver halide, 90%MCM-41 molecular sieve; Ethanolic solution or methanol aqueous solution are wetting agent, water in the wetting agent: ethanol or methyl alcohol volume ratio are (v/v) 1: 1.This catalyst is made the gray solid particle of homogeneous, and nanometer particle size is 30-50nm.Described silver halide AgX is silver chlorate, silver bromide.

The principle of the invention is: silver halide is important photosensitive material, as a kind of novel photochemical catalyst, has excellent photocatalytic performance aspect photocatalysis degradation organic contaminant.And metal nanoparticle has unique optical property-surface plasma body resonant vibration, simple substance Ag plays hybridism to semiconductor AgX, make its response light wavelength generation red shift, thereby make energy be lower than its electron transition of near ultraviolet excitation of energy gap, bring out photochemical reaction, and sunshine is stronger at the light of this scope.From practical standpoint, the silver halide catalyst specific surface agent of single component is little, particle diameter is little, and it is very difficult to separate recovery from product, and its application is very limited.The MCM-41 mesopore molecular sieve has high-specific surface area and regular mesopore orbit, and especially in heterogeneous catalysis field, mesopore molecular sieve is usually as catalyst or catalyst carrier.Photochemical catalyst is coated on the MCM-41, can obtains the multifunctional material that existing photocatalysis has mesoporous characteristic property again.Carrier of photocatalyst not only can fixed photocatalyst, prevents the loss of photochemical catalyst, and is easy to reclaim.It has complete band gap at near-infrared and visible region, help to improve effective surface area and the active site position that visible light photocatalysis active promptly increases photochemical catalyst, help right separation of electrons/and increase absorption, improve visible light radiant utilization rate reactant.The two synergy has improved the photocatalysis performance and the quantum efficiency of catalyst effectively.

Its preparation method is as follows:

(1) meso pore silicon oxide material MCM-41's is synthetic: using softex kw (CTAB) as the template agent, be silicon source adding deionized water with ethyl orthosilicate (TEOS), under alkali condition according to CTAB: TEOS: NaOH: H ₂O=1: mass ratio mixed in 7.5: 1.8: 500, and the hydro-thermal of carrying out MCM-41 is synthetic;

(2) with 5.0mL 1.0 * 10 ^-3Mol/L NaCl or KBr solution, 2mL 3.4 * 10 ^-2Mol/L trisodium citrate and 5.0mL distilled water inject beaker, slow Dropwise 5 .0mL2.1 * 10 under magnetic agitation ^-3Mol/LAgNO ₃Solution gets AgX white or faint yellow creaming.

(3) MCM-410.1g and the wetting agent for preparing joined in the nano-silver halide sol solutions, under the lucifuge condition, stir dipping 24h.Wetting agent is ethanolic solution or methanol aqueous solution, water in the wetting agent: ethanol or methyl alcohol volume ratio are (v/v) 1: 1.

(4) in (3), add trisodium citrate, and place Photoreactor, at N ₂Protection is down carried out photoreduction 30min, then with solvent evaporation in the sample and carry out drying, and again at 400 ℃ of following roasting 2h, must the Ag@AgX/MCM-41 medium porosity assembling.

Photochemical catalyst of the present invention is used for the sewage purification and the processing of environmental area, pollutant in the degradation water has good degradation for organic pollution especially, also can be used for the photodissociation hydrogen production process of water, the photolysis water hydrogen effect is remarkable, is the catalysis material that meets environmental protection, energy-conservation requirement.

Compare characteristics such as the novel nano composite visible light catalyst that the present invention makes has visible light catalytic efficient height, and absorption property is strong with common nano-photocatalyst.Overcome the defective of the difficult recovery of present nanocatalyst, inconvenience recycling.Reason is: silver halide has the conductor photocatalysis effect, silver has the metal surface plasma effect, is that shell, silver halide are nuclear with the silver atom cluster, has strengthened visible absorption, silver helps separating of electronics and hole simultaneously, has improved photo-quantum efficiency and catalytic activity.As the duct that the mesoporous material of carrier has bigger specific area and abundant rule, absorption property is strong, is convenient to the enrichment to pollutant, has increased the contact area of catalyst and pollutant simultaneously, has accelerated catalytic degradation speed; Wetting agent has improved the molecular sieve surface wettability, increases catalyst in its cell walls and lip-deep adhering to, solved well in the carrier impregnation process silicon materials in the aqueous solution to the shortcoming a little less than the catalyst adhesive force.Experimental results show that this catalyst result of use is good, is general visible photochemical catalyst (nitrating TiO to the visible light decomposition rate of organic dye waste water ₂) 8 times.The preparation method is easy, and cost is low, the reaction condition gentleness, and development prospect is good.

Description of drawings

Fig. 1 is MCM-41 and Ag@AgCl/MCM-41XRD spectrogram, and wherein (a) is the MCM-41XRD spectrogram; (b) be the Ag@AgCl/MCM-41XRD spectrogram;

Fig. 2 is the FT-IR spectrogram of Ag@AgCl/MCM-41 catalyst;

Fig. 3 is the SEM figure of Ag@AgCl shell nuclear particle.

The specific embodiment

For the present invention is illustrated better, as follows for embodiment:

This nano compounded visible light catalyst is that catalyst carrier is formed by the Ag@AgCl with core-shell structure as photochemical catalyst main part, mesopore molecular sieve MCM-41, and each composition percentage by weight is: 5% silver medal, 5% silver chlorate, 90%MCM-41 molecular sieve; Ethanolic solution is a wetting agent, water in the wetting agent: the ethanol volume ratio is (v/v) 1: 1.Mesopore molecular sieve MCM-41 specific area 420m ²/ g, specific pore volume 1.07cm ³/ g, aperture 2.98nm.

Its preparation method is as follows:

(1) take by weighing proper C TAB and NaOH and be dissolved in the deionized water, electromagnetic agitation is treated to begin slowly to drip TEOS after the solution clarification, dropwises back lasting stir about 6h under 25 ℃.Move in the reactor of teflon gasket, place the synthetic 72h of hydro-thermal in 110 ℃ of drying boxes, then with the reactant suction filtration, spend deionised water, and obtain the MCM-41 mesoporous material in 50 ℃ of dry 12h of vacuum to neutral.CTAB: TEOS: NaOH: H ₂The O mass ratio is 1: 7.5: 1.8: 500.

(2) with 5.0mL 1.0 * 10 ^-3Mol/L NaCl solution, 2mL 3.4 * 10 ^-2Mol/L trisodium citrate and 5.0mL distilled water inject beaker, slow Dropwise 5 .0mL 2.1 * 10 under magnetic agitation ^-3Mol/LAgNO ₃Solution gets the AgCl white precipitate.

(3) MCM-41 0.1g and the wetting agent for preparing joined in the nano silver/silver chloride sol solutions, under the lucifuge condition, stir dipping 24h.Wetting agent is an ethanol water, water in the wetting agent: the ethanol volume ratio is (v/v) 1: 1.

(4) in (3), add trisodium citrate, and place Photoreactor, at N ₂Protection is down carried out photoreduction 30min, then with solvent evaporation in the sample and carry out drying, and again at 400 ℃ of following roasting 2h, must the Ag@AgX/MCM-41 medium porosity assembling.

The photocatalytic degradation experiment is carried out in the photocatalytic degradation reaction unit, in the 100ml mass concentration is to add a certain amount of photochemical catalyst in the 10mg/L methylene blue solution, and the aqueous solution of methylene blue of getting same concentrations is as blank, fully stir, keep catalyst to be in suspended state, dark reaction 0.5h makes system reach adsorption equilibrium.Then solution is placed reaction under the high voltage mercury lamp radiation, keep light source apart from liquid level 20cm, stir by blasting air in the course of reaction, at interval the 20min sampling is centrifugal remove catalyst after, get a certain amount of supernatant, survey its absorbance with ultraviolet-visible spectrophotometer at absorbing wavelength λ=665nm place, according to the variation of absorbance before and after the illumination or light transmittance, ask its degradation rate again.The result shows: 120min is penetrated in illumination, and catalyst reaches 95% to the degradation rate of the methylene blue solution of 10mg/L, and stable in properties, cost low, be easy to separate.

Claims (3)

1. a nano-material composite visible light catalyst is characterized in that, is catalyst carrier with mesopore molecular sieve MCM-41, and simple substance silver is core, has the Ag@AgX of core-shell structure as the photochemical catalyst main part for shell, silver halide; Each composition by weight percentage, content is as follows: 0.5～5% simple substance silver, 5～9.5% silver halide, 90% mesopore molecular sieve MCM-41 carrier; Silver halide is silver chlorate, silver bromide.

2. prepare the method for the described nano-material composite visible light catalyst of claim 1, it is characterized in that, as follows preparation:

(1) meso pore silicon oxide material MCM-41's is synthetic: use softex kw (CTAB) as the template agent, with ethyl orthosilicate (TEOS) is that the silicon source adds deionized water, under alkali condition according to softex kw: ethyl orthosilicate: NaOH: H ₂O=1: mass ratio mixed in 7.5: 1.8: 500, and the hydro-thermal of carrying out MCM-41 is synthetic;

(2) preparation of nano-silver halide colloidal sol: with 5.0mL 1.0 * 10 ^-3Mol/LNaCl or KBr solution, 0.2mL 3.4 * 10 ^-2Mol/L trisodium citrate and 5.0mL distilled water inject beaker, slow Dropwise 5 .0mL 2.1 * 10 under magnetic agitation ^-3Mol/LAgNO ₃Solution gets silver halide white or faint yellow creaming;

(3) loadization of catalyst: the MCM-41 0.1g and the wetting agent that prepare are joined in the nano-silver halide sol solutions, under the lucifuge condition, stir dipping 24h;

(4) in (3), add trisodium citrate, and place Photoreactor, at N ₂Protection is down carried out photoreduction 30min, then with solvent evaporation in the sample and carry out drying, and again at 400 ℃ of following roasting 2h, must the Ag@AgX/MCM-41 medium porosity assembling.

3. prepare the method for the described nano-material composite visible light catalyst of claim 2, it is characterized in that, described wetting agent is ethanol water or methanol aqueous solution, water in the wetting agent: ethanol or methyl alcohol volume ratio are 1: 1.

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