CN102872850B - Oxygen-defect ZnO photocatalyst and preparation method - Google Patents
Oxygen-defect ZnO photocatalyst and preparation method Download PDFInfo
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- CN102872850B CN102872850B CN201210370194.5A CN201210370194A CN102872850B CN 102872850 B CN102872850 B CN 102872850B CN 201210370194 A CN201210370194 A CN 201210370194A CN 102872850 B CN102872850 B CN 102872850B
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Abstract
The invention discloses an oxygen-defect ZnO photocatalyst and a preparation method. The preparation method includes subjecting ZnO nano-powder to vacuum deaeration to obtain the oxygen-defect ZnO photocatalyst. The oxygen-defect ZnO photocatalyst has high visible photocatalytic activity and high ultraviolet photocatalytic activity. The preparation method acquires low-cost raw materials, is simple in process and remarkable in effect, product cost is reduced effectively, and solar utilization rate is increased. Accordingly, the preparation method has high practical value and application prospect.
Description
Technical field
The present invention relates to a kind of oxygen defect type ZnO photochemical catalyst and preparation method thereof, belong to catalysis material technical field.
Background technology
Photocatalysis technology is widely used in the aspect such as environment, the energy, and the performance of catalysis material is vital to photocatalysis technology.Tradition light-catalyst ZnO is because nontoxic, cheap, stable in properties are widely used in photocatalysis field.But it for example also has drawback: can only produce in ultraviolet light region response 1.; 2. light induced electron-hole is higher to recombination rate; 3. have photoetch, these have seriously hindered the application of ZnO aspect photocatalysis.Therefore, light-catalyst ZnO is furtherd investigate, improved photocatalytic activity, expand photocatalysis response range, suppress photoetch and be necessary.Some researchers have carried out a large amount of research to ZnO, and suppressing right compound in light induced electron-hole, produce visible light activity and suppress photoetch aspect and also obtained certain achievement in research, for example utilize the doping of ZnO and nonmetal, metal or with other semi-conductive technology such as compound.But, utilize these technology aspect the visible light-responded scope of expansion ZnO, many times to sacrifice ultraviolet light activity as cost, therefore, one need to be found and photocatalytic activity can be effectively improved, can expand again the response in visible region, and not reduce the method for ZnO ultraviolet light photocatalysis activity.
Summary of the invention
The object of this invention is to provide a kind of oxygen defect type ZnO photochemical catalyst and preparation method thereof, the method is to utilize simple, cheap method that traditional light-catalyst ZnO is produced compared with high visible activity not sacrificing on the photoactive basis of ultraviolet, makes it produce the highlight catalytic active of relative broad range thereby can make full use of natural energy resources sunshine.
The preparation method of a kind of oxygen defect type ZnO photochemical catalyst provided by the present invention, comprises the steps: that nanometer ZnO powder is carried out to vacuum deaeration obtains product.
In above-mentioned preparation method, the particle diameter of described nanometer ZnO powder can be 20nm ~ 50nm.
In above-mentioned preparation method, the temperature of described vacuum deaeration can be 240 ~ 260 DEG C, specifically can be 240 DEG C, 245 DEG C, 250 DEG C, 255 DEG C or 260 DEG C.
In above-mentioned preparation method, the time of described vacuum deaeration can be 3h ~ 9h, specifically can be 3h, 4h, 5h, 7h or 9h.
In above-mentioned preparation method, the low vacuum of described vacuum deaeration is in 0.133Pa.
The present invention also provides the oxygen defect type ZnO being prepared by said method photochemical catalyst; This oxygen defect type ZnO photochemical catalyst all shows high photocatalytic activity under visible ray or UV-irradiation.
Oxygen defect type ZnO photochemical catalyst provided by the invention has produced higher visible light catalysis activity, and ultraviolet light photocatalysis activity also increases; Preparation method provided by the invention, raw material is inexpensive, and technique is simple, and therefore successful effectively reduces product cost, can improve the utilization rate of sunshine, has very high practical value and application prospect.
Brief description of the drawings
Fig. 1 is the temperature programming deoxidation (O of nano-ZnO under He atmosphere in embodiment 1
2-TPD) curve.
Fig. 2 is Kinetics Rate Constants By Using (k) comparison diagram of nano-ZnO and vacuum deaeration ZnO after treatment degradation of methylene blue (MB) under radiation of visible light; Wherein, Fig. 2 (A) in nano-ZnO and embodiment 2 through degrade under radiation of visible light Kinetics Rate Constants By Using (k) comparison diagram of MB of vacuum deaeration ZnO after treatment, Fig. 2 (B) in nano-ZnO and embodiment 3 through degrade under radiation of visible light Kinetics Rate Constants By Using (k) comparison diagram of MB of vacuum deaeration ZnO after treatment.
Fig. 3 is Kinetics Rate Constants By Using (k) comparison diagram of nano-ZnO and vacuum deaeration ZnO after treatment degradation of methylene blue (MB) under UV-irradiation; Wherein, Fig. 3 (A) in nano-ZnO and embodiment 2 through degrade under UV-irradiation Kinetics Rate Constants By Using (k) comparison diagram of MB of vacuum deaeration ZnO after treatment, Fig. 3 (B) in nano-ZnO and embodiment 3 through degrade under UV-irradiation Kinetics Rate Constants By Using (k) comparison diagram of MB of vacuum deaeration ZnO after treatment.
Fig. 4 is nano-ZnO and the sign spectrograms at 255 DEG C and 5h vacuum deaeration ZnO after treatment; Wherein, Fig. 4 (A), Fig. 4 (B) and Fig. 4 (C) are respectively UVDRS, PL and EPR spectrogram.
Fig. 5 is the photoelectric current test result of nano-ZnO and the ZnO after the vacuum deaeration of 255 DEG C and 5h; Wherein, Fig. 5 (A) is the photoelectricity test result under radiation of visible light, and Fig. 5 (B) is the photoelectric current test result under UV-irradiation.
Detailed description of the invention
The experimental technique using in following embodiment if no special instructions, is conventional method.
Material, reagent etc. used in following embodiment, if no special instructions, all can obtain from commercial channels.
The parent material using in the present invention is commercially available nanometer ZnO powder, and its particle diameter is 20nm ~ 50nm; Depleted gas is inert gas He gas.
Target degradation product is the commercially available pure methylene blue of analysis (MB).
The O of embodiment 1, ZnO
2-TPD
Claim 0.050g nanometer ZnO powder sample to pack in U-shaped quartz ampoule, and be mounted to the relevant position of chemical adsorption instrument, inwardly pass into N
2gas temperature programming to 200 DEG C, 10 DEG C/min of heating rate, gas flow rate 25mL/min continues to keep logical N after 200 DEG C
2gas 2h(removes the impurity of catalyst surface), treat that sample is at N
2under atmosphere, be cooled to after room temperature, then the road of sample being taken a breath is He gas, continues to purge 30min under room temperature, opens ChemiSorb TPx software, and set corresponding program, start to measure, make system from room temperature temperature programming to 550 DEG C, 10 DEG C/min of heating rate, gas flow rate 25mL/min, keep ventilation 5min, be then cooled to room temperature, can obtain the O of ZnO
2-TPD curve.
As shown in Figure 1, ZnO surface deoxidation temperature scope is 240 ~ 260 DEG C, approximately 255 DEG C of best deoxidation temperature.
Claim 1.5g nanometer ZnO powder sample to pack in the quartz ampoule of an end opening, and be mounted to temperature controlled vacuum extractor, control vacuum is 0.133Pa, heating rate is 10 DEG C/min, make respectively temperature programming to 240 DEG C of system, 245 DEG C, 250 DEG C, 255 DEG C and 260 DEG C, keep vacuumizing 5h, be then cooled to room temperature.
Claim 1.5g nanometer ZnO powder sample to pack in the quartz ampoule of an end opening, and be mounted to the vacuum extractor of temperature control, control vacuum is 0.133Pa, heating rate is 10 DEG C/min, in the time of temperature programming to 255 DEG C, system keeps the pumpdown time to be respectively 3h, 4h, 5h, 7h and 9h, is then cooled to room temperature.
Adopt Hitachi U-3010 ultraviolet-visible spectrophotometer, BaSO
4for substrate, sweep limits 200 ~ 800nm, slit width 2nm, sweep speed 600nm/min, the variation of the optical property of ZnO sample before and after observation vacuum deaeration.Use respectively laser Raman spectrometer (excitation wavelength 514nm), photoluminescence spectra (the excitation wavelength 277nm of xenon lamp) and the JEOL ES-ED3X electron paramagnetic resonance of Perkin-Elmer LS55 spectrophotometric determination ZnO sample, at ambient temperature, the variation on observing samples surface, proves the existence of surperficial oxygen defect.
From Fig. 4 (A), after 430nm ~ 800nm vacuum deaeration ZnO compared with vacuum deaeration before parallel raising.
Fig. 4 (B) has provided ZnO and vacuum deaeration ZnO photoluminescence spectra at ambient temperature.Can find out, before and after vacuum deaeration, the luminescent spectrum of ZnO has four main glow peaks, at 420nm (2.95eV), 446nm (2.78eV), 460nm (2.69eV) and 490nm (2.53eV), they are all in visible region respectively.The electronics that is considered to come from excitation state in about 420nm (2.95eV) transmitting is because the transition of oxygen vacancy valence band produces.446nm (2.78eV) emission peak is considered to electronics and is hunted down in ZnO-ZnO grain boundary region.Emission peak 460nm (2.69eV) is and the relevant defect of Zn.The transmitting of 490nm (2.53eV) has much dispute, but best saying be transition herein should be owing to the existence of oxygen defect, this is relevant with Surface Oxygen defect.Emission peak in 420nm and 490nm visibility region is the strongest by force, illustrate vacuum deaeration ZnO at Surface Creation the defect state in oxygen room.Photoluminescence spectra signal is stronger, and the concentration of corresponding oxygen defect is larger.Can be found out by Fig. 4 (B), at 420nm and 490nm place, the peak intensity of vacuum deaeration ZnO is obviously greater than the peak intensity of pure ZnO, also just illustrates that the surface of vacuum deaeration ZnO has produced more Surface Oxygen defect.
From Fig. 4 (C), vacuum deaeration ZnO will be owing to oxygen defect according to former bibliographical information g ~ 2.001-2.004.In g ~ 2.001, the signal at the EPR peak of vacuum deaeration ZnO obviously displays, and ZnO does not have obvious epr signal peak herein, and there is the existence of oxygen defect on this explanation vacuum deaeration ZnO surface.Some research work show, can produce visible light-responded by introducing energy a little less than the oxygen defect of the high concentration of conduction band, and the Surface Oxygen defect of ZnO can be used as catches trap and catch one or two light induced electron, improves the separative efficiency in light induced electron-hole, thereby improve photocatalytic activity.
Be 1.0 × 10 by 50mg vacuum deaeration ZnO photochemical catalyst (product of preparation in embodiment 2 and embodiment 3) and 100mL concentration
-5the MB solution of mol/L is placed in 150mL beaker to be mixed, first ultrasonic 10min, and lucifuge stirs 10min, makes vacuum deaeration ZnO in MB solution, reach adsorption equilibrium and be uniformly dispersed.Then be positioned in the halogen tungsten lamp visible ray evaluating apparatus of green glow and carry out photocatalytic activity evaluation, the light intensity while wherein stablizing is 2.5mW/cm
2every 1 time (every sub-sampling 4.0mL) of 1h sampling, centrifugal 10min under the rotating speed of 12000r/min, get supernatant liquor Hitachi U-3010 ultraviolet-visible spectrophotometer and measure MB residual concentration, calculate the degradation rate of MB, and compare the visible light catalysis activity of the vacuum deaeration ZnO preparing under different condition.
As shown in Figure 2, visible light source halogen tungsten lamp (wave-length coverage 400-800nm, dominant wavelength 550nm), ZnO almost can, by excited by visible light, almost have visible light activity, but vacuum deaeration ZnO after treatment but has obvious visible light catalysis activity, and its photocatalysis efficiency starts to improve gradually along with the rising vacuum deaeration time lengthening of vacuum deaeration temperature, in the time of 255 DEG C and 5h, reach maximum, when continuing rising temperature or extending vacuum deaeration time photocatalysis efficiency declines on the contrary.
Embodiment 5, vacuum deaeration generate the ultraviolet catalytic activity rating of Surface Oxygen defect ZnO sample
Be 1.0 × 10 by 50mg vacuum deaeration ZnO photochemical catalyst and 100mL concentration
-5the MB solution of mol/L is placed in 150mL beaker to be mixed, first ultrasonic 10min, and lucifuge stirs 10min, makes vacuum deaeration ZnO in MB solution, reach adsorption equilibrium and be uniformly dispersed.Then be positioned in the ultraviolet light evaluating apparatus of 254nm and carry out photocatalytic activity evaluation, the light intensity while wherein stablizing is 0.9mW/cm
2every 1 time (every sub-sampling 4.0mL) of 5min sampling, centrifugal 10min under the rotating speed of 12000r/min, get supernatant liquor Hitachi U-3010 ultraviolet-visible spectrophotometer and measure MB residual concentration, calculate the degradation rate of MB, and the vacuum deaeration ZnO relatively preparing under different condition ultraviolet catalytic activity.
As shown in Figure 3, after ZnO vacuum deaeration, increase compared with ZnO ultraviolet catalytic activity.And, along with rising and the increase of vacuum deaeration time of vacuum deaeration temperature, photocatalysis efficiency improves while beginning, in the time of 255 DEG C and 5h, reach maximum
Embodiment 6, vacuum deaeration generate the mensuration of Surface Oxygen defect ZnO sample electrochemical properties
Adopt CHI-660B electrochemical workstation to carry out the mensuration of photoelectric current and AC impedance.
Visible light source adopts the 500W CHF500 type xenon source of Beijing Chang Tuo Science and Technology Ltd., and ultraviolet source is 11W, 254nm ultraviolet germicidal.Adopting three-electrode system, is wherein platinum filament to electrode, and reference electrode is saturated calomel electrode, and working electrode is respectively the glass smear of ZnO and vacuum deaeration ZnO photochemical catalyst.In the homemade electrolytic cell with quartz window, complete, electrolyte is 0.1mol/LNa
2sO
4solution.
From Fig. 5 (A), ZnO visible ray current-responsive is very low, and vacuum deaeration ZnO has produced obvious photocurrent response, has improved approximately 8 times compared with ZnO.Shown in Fig. 5 (B), along with the switch of uviol lamp, ZnO and vacuum deaeration ZnO electrode all can produce stable photocurrent response, and the photoelectric current that vacuum deaeration ZnO produces is approximately 2.5 times of ZnO.The raising explanation of photoelectric current, vacuum deaeration ZnO after treatment can not only effectively improve the migration rate of photoelectric current and the separative efficiency in light induced electron-hole under radiation of visible light, and under UV-irradiation, the migration rate of photoelectric current is also improved accordingly, thereby increase substantially photocurrent response, this is consistent with the result of photocatalytic activity part.
Claims (3)
1. a preparation method for oxygen defect type ZnO photochemical catalyst, comprises the steps: that nanometer ZnO powder is carried out to vacuum deaeration obtains product;
The temperature of described vacuum deaeration is 240～260 DEG C; The time of described vacuum deaeration is 3h～5h; The vacuum of described vacuum deaeration is 0.133Pa.
2. method according to claim 1, is characterized in that: the particle diameter of described nanometer ZnO powder is 20nm～50nm.
3. the oxygen defect type ZnO photochemical catalyst that in claim 1-2, described in any one prepared by method.
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| RU2678983C1 (en) * | 2018-04-25 | 2019-02-05 | Ооо "Нпо Аква" | Method of obtaining a photocatalizer based on zinc oxide |
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| CN113083277B (en) * | 2021-03-30 | 2022-04-22 | 西南科技大学 | Preparation method and application of nano ZnO rich in oxygen vacancy for photocatalytic reduction of hexavalent uranium |
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