CN104907060A - CeO2 / TiO2 heterojunction nano flower preparation method - Google Patents

Abstract

The present invention discloses a CeO2 / TiO2 heterojunction nano flower preparation method. TiO2 nano flower is prepared by hydrothermal reaction of isopropyl titanate as a raw material and acetic acid as a solvent, a TiO2 nano flower sample is dispersed in deionized water, and an appropriate amount of cerium nitrate is added for hydrothermal reaction to prepare CeO2 / TiO2 heterojunction nano flower. The CeO2 / TiO2 heterojunction nano flower structure can broaden TiO2 UV-visible light absorption edge from ultraviolet region to visible region, and improve TiO2 light response range. The photocatalytic activity of the CeO2 / TiO2 heterojunction nano flower can be studied by simulation of sunlight irradiated methyl orange degradation, by comparison of P25 and the TiO2 nanoflower, the CeO2 / TiO2 heterojunction nano flower shows outstanding photocatalytic activity, within 60min, 98% of methyl orange is degraded mainly due to the special heterostructure capable of enhancing the photocatalytic activity.

Description

A kind of CeO 2/ TiO 2the preparation method of hetero-junctions nano flower

Technical field

The present invention relates generally to light degradation field, particularly relates to a kind of CeO ₂/ TiO ₂the preparation method of hetero-junctions nano flower.

Background technology

TiO ₂as a kind of semiconductor catalysis material with multi-functional characteristic, be subject to researchers in fields such as photocatalysis, opto-electronic conversion, DSSC and biology sensors to pay close attention to widely, have high activity, nontoxic, indissoluble, etc. advantage, in photocatalysis degradation organic contaminant, show bright application prospect.But, at TiO ₂in photocatalytic process, have that quantum efficiency is low, sunshine utilizes rate variance, photo-generate electron-hole is to defects such as recombination probability are high.For improving its photocatalytic activity, making full use of sunshine, usually needing TiO ₂modification, such as noble metal decorated, ion doping, composite semiconductor are modified and dye sensitization etc., wherein semiconductor/semiconductor is compounded to form hetero-junctions is also a kind of effective method, after the semiconductor and wide bandgap semiconductor materials with the arrowband system of visible absorption are carried out heterojunction structure compound, effectively can expand the absorption region of compound to light sunlight, offset to visible ray direction.

Be that the rare earth element of representative has unique electronic structure with Ce, there is special optical, electrical and magnetic property, good electron transfer orbital can be provided.CeO ₂it is a kind of important rare earth oxide, be widely used in luminescent material, UV absorbing material, electronic ceramics etc., have and good store oxygen ability, the structural stability of photochemical catalyst can not only be improved and improve the photocatalysis performance in activated centre, but also the redox ability of photochemical catalyst can be strengthened, by CeO ₂be compound to TiO ₂nano grain surface forms heterojunction structure, makes it have good electro transfer and photocatalytic activity.

The present invention is using metatitanic acid isopropyl ester as titanium source, and six water cerous nitrates, as cerium source, adopt hydro-thermal method, prepared CeO ₂/ TiO ₂hetero-junctions nano flower, the analysis means such as X-ray diffraction (XRD), ESEM (SEM), transmission electron microscope (TEM) and UV-Visible absorption (UV-vis) are utilized to characterize the sample topography of preparation and structure, and be target contaminant with methyl orange, investigate the photocatalysis performance of sample, and the mechanism of photocatalytic degradation has been analyzed.

Summary of the invention

The object of the invention is just to provide a kind of CeO ₂/ TiO ₂the preparation method of hetero-junctions nano flower.

The present invention is achieved by the following technical solutions:

A kind of CeO ₂/ TiO ₂the preparation method of hetero-junctions nano flower, comprises the following steps:

(1) TiO is prepared ₂nano flower: 1-1.2ml isopropyl titanate is joined in 30-35ml acetic acid, stir 30min, being transferred to volume is in the reactor of 50ml polytetrafluoroethylliner liner, 12h is incubated at 120-140 DEG C in air dry oven, products therefrom, through eccentric cleaning, through the dry 12h of 60-70 DEG C of air dry oven, is collected gained sample and is put into annealing furnace again, be incubated 2-3h at 450-500 DEG C, obtain TiO ₂nano flower;

(2) finished product preparation: get the above-mentioned TiO of 0.9-1mmol ₂nano flower mixes with the six water cerous nitrates of 0.028-0.03mmol, be distributed in 40ml deionized water, magnetic agitation 30min, adding ammoniacal liquor regulates pH value to be 9-10, then solution is transferred to air dry oven, is incubated 12h at 90-100 DEG C, product is through alcohol and distilled water alternately cleaning, centrifugal, dry, collect at gained sample puts into annealing furnace 450-500 DEG C again and be incubated 2-3h, obtain described CeO ₂/ TiO ₂hetero-junctions nano flower.

Advantage of the present invention is:

The present invention is by CeO ₂be compound to TiO ₂nano flower surface forms hetero-junctions and makes it have good electron transfer properties and photocatalytic activity, TiO ₂uV-Visible absorption limit widen visible region by UV light region, thus improve photoresponse scope, the present invention is irradiated to decline at simulated solar irradiation and is separated methyl orange and study CeO ₂/ TiO ₂the photocatalytic activity of hetero-junctions nano flower, by with P25 and TiO ₂nano flower compares, CeO ₂/ TiO ₂the photocatalytic activity that the performance of hetero-junctions nano flower is excellent, in 60min, degrade the methyl orange of 98%, this mainly comes from its special heterojunction structure, can strengthen photocatalytic activity.

Accompanying drawing explanation

Fig. 1 is CeO ₂/ TiO ₂the XRD spectra of hetero-junctions nano flower;

Fig. 2 is CeO ₂/ TiO ₂the different amplification SEM figure of hetero-junctions nano flower;

Fig. 3 is CeO ₂/ TiO ₂the SEM figure of the different amplification of hetero-junctions nano flower;

Fig. 4 is CeO ₂/ TiO ₂the TEM figure of the different amplification of hetero-junctions nano flower;

Fig. 5 is CeO ₂/ TiO ₂the TEM figure of the different amplification of hetero-junctions nano flower;

Fig. 6 is CeO ₂/ TiO ₂the High-Resolution Map of hetero-junctions nano flower;

Fig. 7 is pure TiO ₂and CeO ₂/ TiO ₂the UV, visible light collection of illustrative plates of hetero-junctions nano flower;

Fig. 8 is CeO ₂/ TiO ₂hetero-junctions nano flower mechanism of degradation;

Fig. 9 is P25, TiO ₂nano flower, CeO ₂/ TiO ₂hetero-junctions nano flower degraded methyl orange test curve figure.

Detailed description of the invention

Embodiment 1:

A kind of CeO ₂/ TiO ₂the preparation method of hetero-junctions nano flower, is characterized in that comprising the following steps:

(1) TiO is prepared ₂nano flower: 1ml isopropyl titanate is joined in 30ml acetic acid, stir 30 minutes, being transferred to volume is in the reactor of 50ml polytetrafluoroethylliner liner, 12h is incubated at air dry oven 140 DEG C, products therefrom is through eccentric cleaning, 60 DEG C of dry 12h of air dry oven, collect at annealing furnace 500 DEG C put into again by gained sample and are incubated 3h, obtain TiO ₂nano flower;

(2) finished product preparation: get the above-mentioned TiO of 1mmol ₂nano flower mixes with the six water cerous nitrates of 0.03mmol, be distributed in 40ml deionized water, magnetic agitation 30min, adding ammoniacal liquor regulates pH value to be 10, then 12h is incubated at solution being transferred to air dry oven 100 DEG C, product, through alcohol and distilled water alternately cleaning, centrifugal, dry, is collected at annealing furnace 500 DEG C put into again by gained sample and is incubated 3h, obtain described CeO ₂/ TiO ₂hetero-junctions nano flower.

The present invention adopts multiple characterization method to carry out the sign of various performance to prepared sample, utilize X-ray diffraction (XRD) instrument, characterize the crystalline phase of prepared sample, phase composition and grain size, the XRD that the present invention uses is the XD-3 type X-ray diffractometer that Beijing Puxi General Instrument Co., Ltd produces; What uv-visible absorption spectra (UV-Vis) was used is the U-4100 type ultraviolet-visible spectrophotometer that HIT produces, and collection wavelength is 200-800nm; The ESEM (SEM) used is the S-4800 type sweep electron microscope that HIT produces; Transmission electron microscope (TEM) uses JEM-2100 type high-resolution-ration transmission electric-lens;

Photocatalytic degradation is tested:

Photocatalytic degradation test of the present invention is at room temperature carried out, and chooses methyl orange (concentration is 20mg/L) as target contaminant, before experiment, and whole glass apparatus distilled water washes clean.The methyl orange solution getting 20ml is placed in the beaker of 50ml, adds 20mg CeO ₂/ TiO ₂hetero-junctions nano flower catalyst, under dark surrounds, continuing magnetic force stirs 30min, reaches the attached balance of absorption-desorption to make dyestuff and catalyst surface.350W xenon lamp (upper sea blue bright Electronics Co., Ltd. is adopted in experiment, model XQ350W) as simulated solar radiant, be placed in distance reaction system 10cm position illumination to impel the carrying out of catalytic reaction, simultaneously, in whole light-catalyzed reaction process, keep magnetic stirring apparatus to stir always.The concentration of methyl orange is measured by ultraviolet-visible spectrometer (UV-3200S, Shanghai Mei Puda Instrument Ltd., China).Reaction solution to filter every 10min and tests the change in concentration of methyl orange by analog light source illumination, and often group experiment total time is 60min.

Experimental result:

Fig. 1 is CeO ₂/ TiO ₂the XRD spectra of hetero-junctions nano flower, diffraction maximum is in 2 θ=25.5 °, and 37.9 °, 48.1 °, 54.1 °, 55.0 °, 62.7 ° have 6 obvious diffraction maximums, correspond respectively to Anatase TiO ₂(101), (004), (200), (105), (211), (204) diffraction surfaces (JCPDS NO.21-1272); 2 θ=28.6 ° in figure, 33.2 °, 47.5 °, 56.5 °, 59.2 ° there are 5 new diffraction maximums, through and standard card (JCPDS NO.34-394) comparison, correspond respectively to CeO ₂(111), (200), (220), (311), (222) crystal face, belongs to CeO ₂characteristic diffraction peak, show that this heterojunction structure nano material that we prepare is by TiO ₂nano flower and CeO ₂nano-particles reinforcement, and there is good degree of crystallinity.

Fig. 2,3 is the CeO prepared ₂/ TiO ₂hetero-junctions nano flower is at the scanning electron microscope (SEM) photograph of different amplification.As seen from the figure, the CeO of synthesis ₂/ TiO ₂hetero-junctions nano flower presents hierarchy, and pattern is flower-shaped.CeO ₂/ TiO ₂the average diameter of nano flower is at 1.5 μm.The SEM figure of high-amplification-factor shows, and the pattern of " petal " of this nano flower is nanobelt, and has many CeO in its surface ₂nano particle adheres to uniformly, CeO ₂the diameter of nano particle for being about about 150nm, and does not occur to reunite and independent nucleation phenomenon.

Fig. 4,5 illustrate CeO ₂/ TiO ₂the transmission electron microscope picture of hetero-junctions nano flower under different amplification, Fig. 4 show be low multiplication factor TEM figure, as seen from the figure, CeO ₂/ TiO ₂average diameter be 1.5 μm, this is consistent with the SEM picture in Fig. 2; Fig. 5 show be high-amplification-factor TEM figure, TiO ₂nano flower is assembled by thinner nanobelt, and TiO ₂nano flower is modified many CeO ₂nano particle, these CeO ₂nano particle average grain diameter is about 150nm, this and Fig. 2, and the SEM picture in 3 is consistent, CeO ₂nano particle presents irregular spherical, and size is more even.

Fig. 6 is CeO ₂nano particle and TiO ₂the hetero-junctions crystal lattice structure of nano flower junction, corresponding high resolution diffraction striped marks in the drawings, and wherein fringe spacing is the crystal face of 0.248nm, is Anatase TiO ₂(103) face; Fringe spacing is the crystal face of 0.323nm is CeO ₂(111) face, show that gained sample is CeO further ₂nano particle and TiO ₂the hetero-junctions that nano flower is composited;

Fig. 7 is CeO ₂/ TiO ₂hetero-junctions nano flower and pure TiO ₂uv-visible absorption spectroscopy.As seen from the figure, pure TiO ₂a precipitous ABSORPTION EDGE has been there is in UV-vis curve at 370nm place.CeO ₂/ TiO ₂hetero-junctions nano flower has and pure TiO in the scope of 300nm ~ 700nm (namely ultraviolet is to visible region) ₂similar absorption curve, illustrates CeO ₂/ TiO ₂the photodegradative light abstraction width of hetero-junctions nano flower covers ultraviolet and visible region.CeO ₂/ TiO ₂hetero-junctions nano flower absorption intensity is but far above pure TiO ₂, and CeO ₂/ TiO ₂the ABSORPTION EDGE red shift of hetero-junctions nano flower is to visible ray about 490nm, and this shows CeO ₂/ TiO ₂hetero-junctions nano flower and pure TiO ₂compare and there is higher photocatalytic activity.For CeO ₂/ TiO ₂hetero-junctions nano flower, TiO ₂ceO on nano flower ₂nano particle can absorb visible ray, and ultraviolet light can pass through CeO ₂nano particle or TiO ₂the white space of nano flower passes to TiO ₂nano flower, thus be absorbed.CeO ₂/ TiO ₂broadband, the forbidden band value that hetero-junctions nano flower is corresponding is 2.53eV, and this shows through CeO ₂tiO after compound ₂catalysis material effectively reduces its forbidden band bandwidth, can make full use of the visible light part of sunshine when photocatalysis degradation organic contaminant;

Fig. 8 is CeO ₂/ TiO ₂the experimental principle of hetero-junctions nano flower Photodegradation of Methyl Orange and light absorption energy band diagram.CeO ₂/ TiO ₂hetero-junctions nano flower the disposal efficiency is than pure TiO ₂high reason primarily of following some: first, TiO ₂nano flower and the CeO taken ₂nano particle forms heterojunction structure, thus makes its light abstraction width comprise Uv and visible light scope, makes it have light degradation property to Uv and visible light scope concurrently; Secondly, CeO in hetero-junctions ₂the a little higher than TiO of conduction band ₂conduction band, the compound that this band structure can suppress photo-generate electron-hole right effectively, this is also the main cause that heterojunction structure can improve photocatalytic activity, and then more light induced electron participates in reduction reaction and forms superoxide radical (O ₂ ^-), superoxide radical is the oxidant effectively of one wherein of degraded methyl orange; Photohole then participates in oxidation reaction and generates hydroxyl radical free radical (OH), and hydroxyl radical free radical is also a kind of strong oxidant of degraded methyl orange.Again, CeO ₂/ TiO ₂hetero-junctions has stronger capturing ability to methyl orange molecule, thus improves the disposal efficiency.In sum, light degradation process roughly comprises following three steps: methyl orange molecule is caught, methyl orange degradation, methyl orange decompose release.Mechanism of degradation analysis as shown in Figure 8;

CeO ₂/ TiO ₂the light degradation pattern of hetero-junctions under Uv and visible light irradiates has two kinds.On the one hand, under ultraviolet light, TiO ₂and CeO ₂can be excited, excite generation light induced electron at conduction band, produce photohole in valence.Due to CeO ₂conduction band at the bottom of current potential lower than TiO ₂conduction band at the bottom of current potential, thus CeO ₂the electronics that conduction band excites can transfer to TiO very like a cork by both contact surfaces ₂conduction band, similar, TiO ₂the hole that valence band produces can be injected into CeO by both contact surfaces ₂valence band on.This makes photo-generate electron-hole to can quick separating, thus contributes to improving photocatalytic activity; On the other hand, under visible light, CeO ₂excite generation electron-hole pair, light induced electron can from CeO ₂conduction band passes to TiO ₂conduction band, photohole can from TiO ₂valence band transfer to CeO ₂valence band on, thus contribute to the separation of electron-hole pair;

Fig. 9 is CeO ₂/ TiO ₂hetero-junctions nano flower, P25, TiO ₂nano flower is to the light degradation curve of methyl orange.This light degradation experiment carries out under simulated solar irradiation irradiates, when unglazed photograph, and CeO ₂/ TiO ₂hetero-junctions nano flower degrades the methyl orange of 6% at 60min, and this is mainly due to CeO ₂/ TiO ₂hetero-junctions has stronger capture ability to methyl orange molecule; Under illumination simulation condition, P25 degrades the methyl orange of 62% in 60min, and TiO ₂nano flower then degrades the methyl orange of 73%, relative to P25, TiO ₂the photodegradation rate that nano flower improves mainly comes from TiO ₂hierarchy add light scattering, improve the utilization rate of light, thus contribute to the raising of photocatalytic activity; CeO ₂/ TiO ₂hetero-junctions nano flower has showed best photocatalytic activity, degrades the methyl orange of 98%, CeO in 60min ₂/ TiO ₂the raising of hetero-junctions nano flower photocatalytic activity mainly comes from the effect of hetero-junctions.Under simulated solar irradiation irradiates, CeO ₂/ TiO ₂hetero-junctions nano flower not only can absorb ultraviolet light can also absorb visible ray.And CeO ₂conduction band higher than TiO ₂conduction band, thus CeO ₂the light induced electron excited can be quickly transferred to TiO ₂on nano flower, photohole is then from TiO ₂on transfer to CeO ₂on, thus the compound that inhibit photo-generate electron-hole right.In addition, in visible-range, CeO ₂the light induced electron excited via its conduction band through CeO ₂and TiO ₂the interface of hetero-junctions is transferred to TiO ₂conduction band on, thus suppress the compound of electron-hole pair.

Claims (1)

1. a CeO ₂/ TiO ₂the preparation method of hetero-junctions nano flower, is characterized in that comprising the following steps:

(1) TiO is prepared ₂nano flower: 1-1.2ml isopropyl titanate is joined in 30-35ml acetic acid, stir 30min, being transferred to volume is in the reactor of 50ml polytetrafluoroethylliner liner, 12h is incubated at 120-140 DEG C in air dry oven, products therefrom eccentric cleaning, through the dry 12h of 60-70 DEG C of air dry oven, collects gained sample and puts into annealing furnace again, be incubated 2-3h at 450-500 DEG C, obtain TiO ₂nano flower;

(2) finished product preparation: get the above-mentioned TiO of 0.9-1mmol ₂nano flower mixes with the six water cerous nitrates of 0.028-0.03mmol, be distributed in 40ml deionized water, magnetic agitation 30min, adding ammoniacal liquor regulates pH value to be 9-10, then solution is transferred to air dry oven, is incubated 12h at 90-100 DEG C, product is through alcohol and distilled water alternately cleaning, centrifugal, dry, collect at gained sample puts into annealing furnace 450-500 DEG C again and be incubated 2-3h, obtain described CeO ₂/ TiO ₂hetero-junctions nano flower.