CN100522350C

CN100522350C - Hydrothermal method for preparing superstructure visible light responsive Bi2WO6 photcatalyst

Info

Publication number: CN100522350C
Application number: CNB2006101179813A
Authority: CN
Inventors: 王文中; 张丽莎; 周林
Original assignee: Shanghai Institute of Ceramics of CAS
Current assignee: Shanghai Institute of Ceramics of CAS
Priority date: 2006-11-03
Filing date: 2006-11-03
Publication date: 2009-08-05
Anticipated expiration: 2026-11-03
Also published as: CN1951557A

Abstract

The invention relates to a method for preparing Bi2WO6 optical catalyst which can respond visible light. Wherein, said method comprises that (1), preparing the forward body with Bi2WO6 structure at nanometer size that mixing the reactants or adding surface activator (P123, PVP, CTAB), mixing uniformly; (2), under 120-240Deg. C, reacting the forward body in water heating condition for 4-24h, eccentrically separating the product, washing and drying at 30-150Deg. C, to obtain the powder; then sintering the powder at 300-750Deg. C for 1-10h, to obtain the final catalyst. The invention has low cost, while the inventive catalyst high tens time degrade efficiency than TiO2 (P25).

Description

The Bi of superstructure visible light responsive 2WO 6The hydrothermal preparing process of photochemical catalyst

Technical field

The present invention relates to utilize Hydrothermal Preparation to have the Bi of superstructure ₂WO ₆, have superstructure with the catalyst of this method preparation, and have visible light photocatalysis efficient efficiently.

Background technology

Energy crisis and environmental problem are the most serious problems that faces this century, and the environmental problem that particularly poisonous persistent organic pollutants (as halides, agricultural chemicals, dyestuff etc.) cause has become influences human survival and healthy significant problem.Directly utilizing solar energy these organic pollutions of degrading by photocatalysis is the most friendly approach that are expected to solve this two hang-up.This method is unfavorable uses the artificial energy source, and thoroughly mineralising organic pollution and non-secondary pollution are a kind of green environment improvement technology with broad prospect of application, have become at present one of active research direction the most.Present industrial photocatalysis flow process all adopts TiO basically ₂Based photocatalyst.Because TiO ₂Band gap be 3.2eV, only can be excited, thereby visible light photocatalysis efficient is low excessively by ultraviolet light (only account for solar energy 3.8%).And visible light accounts in the solar energy 43% energy, therefore, researches and develops new and effective visible light responsive photocatalytic material, be to utilize solar energy to realize the key of optical catalytic environment purification, and also be inexorable trend and the developing direction that practicability is further moved towards in photocatalysis.

Be different from the titanium dioxide of doping, Bi ₂WO ₆Have at visible region and more precipitous can be with ABSORPTION EDGE, show that their visible absorption results from the band-to-band transition of itself, but not the effect of impurity energy level, avoided the formed complex centre of impurity effectively and reduce catalytic efficiency.This photochemical catalyst has unique layer structure simultaneously, catalytic reaction is mainly carried out in interlayer space, play " two dimension " photocatalysis, its photocatalytic activity also can change because of the molecule of interlayer or the difference of ion, is the new and effective heterogeneous photochemical catalyst of a class.In recent years in the coming year, Zou Zhigang or the like has reported Bi ₂WO ₆Under the visible radiation of wavelength, has photocatalytic activity greater than 400nm.In addition, Bi ₂WO ₆Valence band (VB) form by Bi6s and O2p orbital hybridization, have higher oxidation activity and charge mobility.Therefore, Bi ₂WO ₆The research of semiconductor light-catalyst is removed for the development visible light photocatalysis and degradable organic pollutant opens up a new way.

Yet, this class Bi ₂WO ₆The present normally high-temperature solid phase reaction method preparation of photochemical catalyst.Calcination process not only consumes a large amount of energy, can not regulate and control the pattern and the structure of product effectively, orientation etc., and make the sample particle size of preparation bigger than normal, cause the specific area of catalyst to reduce greatly.Therefore, though can realize visible light-responded, its photocatalysis efficiency and not ideal enough.Nano material has unique quantum effect, skin effect, and carrier diffusion effects etc. help catalytic activity and optionally raising.Therefore the Bi for preparing nanostructured ₂WO ₆Photochemical catalyst will significantly improve the efficient of degradable organic pollutant.Hydrothermal synthesis method is the in the recent period emerging a kind of economy of inorganic nano material, effective means of preparing.The present invention intends going out low cost, high efficiency Bi with Hydrothermal Preparation ₂WO ₆The visible light photocatalysis nano material.

Summary of the invention

The object of the present invention is to provide a kind of simple, quick, eco-friendly hydrothermal synthesis method to prepare Bi ₂WO ₆Superstructure synthesizes the Bi with superstructure and efficient visible light photocatalysis performance efficient visible light activity ₂WO ₆Photochemical catalyst.

The concrete preparation process of the present invention is as follows:

1) has the Bi of nano-scale ₂WO ₆The predecessor preparation of superstructure

With nitrate, chloride or the oxalates and W sodium salt, the ammonium salt etc. that contain Bi is raw material, pressing the stoichiometric proportion of Bi:W=2:1 mixes, wherein Bi molar concentration scope is 1～40mmol/L, or to add mass percent again be 2%～10% surfactant, itself and raw material are mixed, the pH value of the hierarchy of control is 0.5～7, forms the precursor liquid of white suspension;

2) hydrothermal condition is: the fill volume of predecessor in water heating kettle is 50%～80%, the temperature range of hydro-thermal reaction is 120 ℃～240 ℃, the hydro-thermal reaction time is that 4h～24h. carries out post processing with the product after the hydro-thermal reaction again, step is: centrifugation goes out precipitation, clean, at 30 ℃～150 ℃ at air drying, obtain powder, or with powder again at sintering temperature 1h～10h of 300 ℃～750 ℃, just obtained to have the efficient visible light response semiconductor photochemical catalyst Bi of the superstructure of secondary structure ₂WO ₆Prepared micron order superstructure Bi ₂WO ₆Be to assemble by nanometer scale nanometer sheet or nanometer rods to form.

Described surfactant is P123 (EO ₂₀PO ₇₀EO ₂₀), a kind of in polyvinylpyrrolidone (PVP), softex kw (CTAB), polyethylene glycol (PEG) and the ethylenediamine tetra-acetic acid (EDTA).

The present invention and the Bi that adopts the additive method preparation ₂WO ₆Photochemical catalyst has following advantage:

1) the hydrothermal synthesis method cost that provides of this invention is low, simple to operate.

2) has the Bi of superstructure ₂WO ₆Not only can be implemented under the radiation of visible light and be excited, also present high catalytic activity, Photocatalytic Activity for Degradation efficient compares TiO ₂(P25) to exceed tens times (seeing embodiment for details).

Description of drawings

Fig. 1 is the Bi of hydrothermal preparation among the embodiment 1,2 ₂WO ₆Superstructure XRD diffracting spectrum

Fig. 2 is hydrothermal preparation Bi among the embodiment 1 ₂WO ₆The stereoscan photograph of superstructure

Fig. 3 is hydrothermal preparation Bi ₂WO ₆(sintering and not sintering), solid phase Bi ₂WO ₆With the degradation rate curve over time of P25 photocatalytic degradation rhodamine B, wherein S represents solid phase method, and H represents hydro-thermal method.

The specific embodiment

Embodiment 1

Bi ₂WO ₆Bi (NO is used in the preparation of superstructure presoma ₃) ₃5H ₂O and Na ₂WO ₄(analyzing pure) is synthetic for raw material, according to stoichiometric proportion, takes by weighing 0.97gBi (NO ₃) ₃5H ₂O (analyzing pure) is dissolved in the 50mL water, adds 0.33g Na then ₂WO ₄(analyzing pure) stirred and formed white suspension pioneer liquid, regulates pH value 0.5～2.5.Pour the white suspension precursor liquid into water heating kettle then, carry out hydrothermal treatment consists, through comparative experiments, choosing the fill volume of forerunner in water heating kettle is 80%, and the temperature range of hydro-thermal reaction is 160 ℃, and the hydro-thermal reaction time is 20h.After reaction finishes, the yellow mercury oxide that obtains is filtered, respectively wash three times with deionized water, absolute ethyl alcohol, then 80 ℃ of dryings.As Fig. 1,, obtained rhombic Bi through the XRD composition ₂WO ₆Superstructure.A is the exemplary scanning electromicroscopic photograph of sample among Fig. 2, as can be seen from the figure, and the Bi about particle diameter 3 μ m ₂WO ₆Superstructure is to be assembled by the nanometer sheet of the about 200nm of size to form.

By the mensuration to product ultraviolet/visible diffuse reflectance spectra, until the visible region all has photoresponse, the estimation band gap is 2.75eV to the bismuth tungstate that present embodiment provides from ultraviolet region.

For research institute prepares the photocatalysis performance of sample, the design visible light is the experiment of degraded rhodamine B down.Utilize the character of rhodamine B photocatalytic degradation decolouring,, observe the variation of solution colourity, and then draw percent of decolourization by the absorbance of ultraviolet/visible absorbance spectrometry solution at 553nm.In order to compare, with (0.072mmol) hydrothermal preparation Bi of equivalent ₂WO ₆The Bi of (sintering and not sintering), solid reaction process preparation ₂WO ₆And P25 (Fig. 3), joining 100mL concentration is 10 ^-5In the rhodamine B solution of mol/L, lucifuge stirred 30 minutes, to reach adsorption equilibrium, placed through λ then〉the 500W xenon lamp irradiation down of filtering of the optical filter of 400nm.Through 60 minutes Photocatalytic Activity for Degradation, hydrothermal preparation Bi ₂WO ₆The powder of superstructure (not sintering) degradation effect is up to 90%, and the Bi of the amount solid phase reaction of same substance preparation ₂WO ₆Powder and P25 degraded situation under the same conditions, the visible light degradation rate is respectively 17% and 19%.Thereby proved Bi ₂WO ₆The visible light photocatalysis active of superstructure.

Embodiment 2

Bi ₂WO ₆Bi (NO is used in the preparation of superstructure presoma ₃) ₃5H ₂O and Na ₂WO ₄(analyzing pure) is synthetic for raw material, according to stoichiometric proportion, takes by weighing 2mmol Bi (NO ₃) ₃5H ₂O (analyzing pure) is dissolved in the 50mL water, adds 1mmol Na then ₂WO ₄(analyzing pure) stirred and formed white suspension pioneer liquid, regulates pH value 0.1～5.Pour white suspension pioneer liquid into water heating kettle then, carry out hydrothermal treatment consists, through comparative experiments, choosing the fill volume of forerunner in water heating kettle is 80%, and the temperature range of hydro-thermal reaction is 160 ℃, and the hydro-thermal reaction time is 20h.After reaction finishes, the yellow mercury oxide that obtains is filtered, respectively wash three times, then after 80 ℃ of dryings, in 550 ℃ of following sintering with deionized water, absolute ethyl alcohol.As Fig. 1, through the XRD constituent analysis, that also obtain is rhombic Bi ₂WO ₆Superstructure, but its degree of crystallinity is higher.Among this embodiment, the Bi about particle diameter 3 μ m ₂WO ₆Superstructure is to be assembled by the nanometer sheet of the about 200nm of size to form, and has formed many nano-pores in the sheet.Wavelength X〉the visible light degraded methyl orange experimental result of 400nm is slightly higher than embodiment 1, and degradation rate is 97% (Fig. 3).

Embodiment 3

Bi ₂WO ₆Use Bi (NO during the preparation of superstructure presoma ₃) ₃5H ₂O and Na ₂WO ₄(analyzing pure) is synthetic for raw material, according to stoichiometric proportion, takes by weighing 2mMol Bi (NO ₃) ₃5H ₂O (analyzing pure) is dissolved in the 50mL water, adds 1mMol Na then ₂WO ₄(analyzing pure) adds surfactant p123 again, stirs to form the white suspension precursor liquid, regulates pH value 0.5～5.Pour the white suspension precursor liquid into water heating kettle then, carry out hydrothermal treatment consists, choosing the fill volume of forerunner in water heating kettle is 60%, and the temperature range of hydro-thermal reaction is 160 ℃, and the hydro-thermal reaction time is 20h..After reaction finishes, the yellow mercury oxide that obtains is filtered, respectively wash three times with deionized water, absolute ethyl alcohol, then 80 ℃ of dryings.Among this embodiment, the Bi about particle diameter 3 μ m ₂WO ₆Superstructure is to be 20nm by length, and diameter is that the nanometer rods of 10nm is assembled and formed.

Embodiment 4

Bi ₂WO ₆Use Bi (NO during the preparation of superstructure presoma ₃) ₃5H ₂O and Na ₂WO ₄(analyzing pure) is synthetic for raw material, according to stoichiometric proportion, takes by weighing 2mmol Bi (NO ₃) ₃5H ₂O (analyzing pure) is dissolved in the 50mL water, adds 1mmol Na then ₂WO ₄(analyzing pure) stirred and formed the white suspension precursor liquid, regulates pH value 7.Pour the white suspension precursor liquid into water heating kettle then, carry out hydrothermal treatment consists, choosing the fill volume of forerunner in water heating kettle is 80%, and the temperature range of hydro-thermal reaction is 160 ℃, and the hydro-thermal reaction time is 20h..After reaction finishes, the yellow mercury oxide that obtains is filtered, respectively wash three times with deionized water, absolute ethyl alcohol, then 80 ℃ of dryings.The Bi for preparing among this embodiment ₂WO ₆It is the laminated structure that is about 2 μ m by length and width.All the other are with embodiment 1.

Claims

1, the Bi of superstructure visible light responsive ₂WO ₆The hydrothermal preparing process of photochemical catalyst is characterized in that the step for preparing comprises:

(A) has the Bi of nano-scale ₂WO ₆The predecessor preparation of superstructure:

1. be raw material with the nitrate, chloride or the oxalates that contain Bi and sodium salt or the ammonium salt of W, press Bi: W=2: 1 stoichiometric proportion is mixed;

2. adding mass percent is the surfactant EO of 2-10% ₂₀PO ₇₀EO ₂₀, itself and step raw material are 1. mixed;

3. the pH value of the hierarchy of control is 0.5～7, forms the precursor liquid of white suspension;

(B) hydro-thermal reaction:

1. the fill volume that is filled in the water heating kettle of the predecessor of steps A preparation is 50%～80%, and the temperature of hydro-thermal reaction is 120 ℃～240 ℃;

2. the product after the hydro-thermal reaction is handled, and condition is the centrifugation precipitation, cleans, 30 ℃～150 ℃ at air drying, make Bi ₂WO ₆Catalyst;

3. or the Bi that step is made in 2. ₂WO ₆Catalyst makes the superstructure Bi with secondary structure at 300-750 ℃ of sintering temperature 1-10h ₂WO ₆Catalyst.

2, press the Bi of the described superstructure visible light responsive of claim 1 ₂WO ₆The hydrothermal preparing process of photochemical catalyst, it is characterized in that steps A 1. in the Bi molar concentration be 1-40mmol/L.

3, press the Bi of the described superstructure visible light responsive of claim 1 ₂WO ₆The hydrothermal preparing process of photochemical catalyst is characterized in that nitrate, chloride or the oxalates of described Bi is pure for analyzing.

4, press the Bi of the described superstructure visible light responsive of claim 1 ₂WO ₆The hydrothermal preparing process of photochemical catalyst is characterized in that the sodium salt of described W or ammonium salt are pure for analyzing.

5, press the Bi of the described superstructure visible light responsive of claim 1 ₂WO ₆The hydrothermal preparing process of photochemical catalyst is characterized in that the hydro-thermal reaction time is 4-24h.

6, press the Bi of the described superstructure visible light responsive of claim 1 ₂WO ₆The hydrothermal preparing process of photochemical catalyst is characterized in that prepared superstructure Bi ₂WO ₆Be to assemble by nanometer sheet or nanometer rods to form.