CN100358626C - Preparation method of high specific surface tantalate and niobate photo catalyst - Google Patents
Preparation method of high specific surface tantalate and niobate photo catalyst Download PDFInfo
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- CN100358626C CN100358626C CNB2004100418165A CN200410041816A CN100358626C CN 100358626 C CN100358626 C CN 100358626C CN B2004100418165 A CNB2004100418165 A CN B2004100418165A CN 200410041816 A CN200410041816 A CN 200410041816A CN 100358626 C CN100358626 C CN 100358626C
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Abstract
The present invention relates to a method for preparing a tantalate photocatalyst or a niobate photocatalyst with a high specific surface. Pentoxide of tantalum or niobium is firstly used as raw material, and water-soluble niobium precursors or tantalum oxalate water solution is obtained. The stable water-soluble precursors of tantalum or niobium, which are obtained with the method, are used for preparing a tantalate photocatalyst and a niobate photocatalyst, and tantalate and niobate which contain alkali metal and alkaline earth metal are prepared. Strontium carbonate, barium carbonate, lithium carbonate or rare earth nitrate is added to the water-soluble precursor solution of tantalum oxalate or niobium oxalate according to the components of a formula, the mixture is dissolved in chelating agents (EDTA), and citric acid is then added. The molar ratio of metal ions and the citric acid is between 1: 4 to 10, a proper amount of ethylene glycol is added as complexing agents, and the mixture is heated at the temperature of 60 DEG C to 80 DEG C and agitated to obtain the precursor solution of the tantalate photocatalyst and the niobate photocatalyst. The tantalate photocatalyst and the niobate photocatalyst are obtained after the precursor solution is polyesterified, burnt for two to four hours, and thermally processed at the temperature of 600 DEG C to 900 DEG C.
Description
Technical field
The present invention relates to the preparation method of a kind of tantalates or niobate photocatalyst, especially adopt water miscible tantalum or niobium precursor, prepare the tantalates of high-ratio surface and the preparation method of niobate photocatalyst by polymer complex technology (PC).
Background technology
The energy and environment are two importances of close concern to each other with the human society survival and development.Catalysis material has critical role aspect energy conversion, environmental protection.Preparing photochemical catalyst highly active, with low cost, stable performance, is extremely active in a current scientific research and development field.The most frequently used traditional photochemical catalyst is titanium dioxide and modification body or derivative, and recently for over ten years, a series of tantalates and niobates become the new material of being a dark horse in the photochemical catalyst development, water is being become aspect hydrogen and the oxygen by photocatalysis Decomposition, particularly directly utilize the solar visible light part, obtained breakthrough, had important and wide application prospect in solar electrical energy generation, battery energy storage, water treatment field.For example, the tantalates of alkali metal containing and alkaline-earth metal and niobates, Sr
2(Ta
2-xNb
x) O
7, (x=0-2), ATaO
3, (A=Li, Na, K), (Sr
xBa
1-x) Ta
2O
6, (x=0-1); The photochemical catalyst of rare-earth-doped modification, as: the ATaO of La element doping
3Laminated perovskite niobates series, A (M
N-1Nb
nO
3n+1), (A=K, Ru, Cs, M=La, Ca, Ti), as K
4Nb
6O
17, KTiNbO
5, KLaNb
2O
7AndCsCa
2Nb
3O
10Deng, all have outstanding photocatalytic activity.And InTaO
4And InNbO
4The oxide semiconductor photochemical catalyst can directly utilize the visible light of the sun to realize the decomposition of water, discharges hydrogen and oxygen.
Yet mainly still (Solid state reaction SSR) obtains by traditional solid-phase sintering reaction in the preparation of tantalates and niobate photocatalyst at present.Traditional solid phase reaction generally uses metal oxide or metal carbonate as parent material, utilize long mechanical lapping such as ball milling etc., realize the even mixing of raw material, in high temperature (1000-1300 ℃ usually) long-time (10-100 hour) reaction down, obtain corresponding product at last then.Therefore, there is following point usually in the solid-phase sintering reaction: the growth of uncontrollable big crystal grain (tens microns of 1-); The stoichiometric proportion loss that volatile components such as alkali metal cause at high temperature evaporation; The local fractional condensation of one or more components.These will cause the photocatalytic activity of photochemical catalyst obviously to descend.Adopt the solution synthesis method of wet-chemical, initiation material is dissolved in certain solvent, by subsequent heat treatment is little and even in relatively low technological temperature acquisition granularity, photocatalyst powder is accurately compared in metering, is a kind of method of simple possible.Wherein, (Polymerizable complex, PC) technology has original advantage aspect preparation high-ratio surface, the accurate powder of composition to the polymer complex of naming with Pechini.It adopts water-soluble precursor, by metal citrate (CA) and polyalcohol (normally ethylene glycol EG), under heating condition, obtains required polyester polymers by polycondensation reaction (dehydration).Metal ion is evenly distributed on molecular scale in the polymeric matrix, again by high-temperature heat treatment (500-900 ℃), obtains oxide powder.Yet, preparation tantalates and required water miscible niobium and the tantalum precursor of niobate photocatalyst, still more unobtainable.Ethanol tantalum and ethanol niobium are the precursor materials of normal use in the synthetic compound that contains tantalum or niobium of wet chemistry method, yet the major defect of alkoxide group technology is that ethanol tantalum and ethanol niobium cost an arm and a leg, to moist extreme sensitivity.Although some corrective measures are adopted, as part substituted alkoxies such as use EGMEs, part has improved the stability of precursor, still can not fundamentally address this problem, and has also greatly limited the commercial applications of similar preceding system.Tantalic chloride, columbium pentachloride also have been used the precursor as tantalum or niobium, although relative alkoxide, its price is more cheap, stability also has improvement, in having the environment of aqueous vapor, tantalic chloride (niobium) still is unsettled, and can discharge by mordant hydrogen chloride gas in the process heat processing procedure, and remaining small amounts of chlorine ion also can have a negative impact to photocatalysis property.Core of the present invention is to use tantalum pentoxide (Ta
2O
5) and niobium pentaoxide (Nb
2O
5) these two kinds of cheapnesss, stable raw material, by a kind of simple and feasible synthesis path, obtain the precursor (referring to Chinese invention patent application number 200410014962.9) of extremely stable water miscible tantalum or niobium.Adopt this precursor, make the precursor solution of a series of catalysis materials, as Sr
2(Ta
2-xNb
x) O
7, ATaO
3, (A=Li, Na, K), (Sr
xBa
1-x) Ta
2O
6, mix the LaTaO of La
3And K
4Nb
6O
17, KTiNbO
5Deng precursor solution, have fabulous stability, by polymer complex technology (PC), under low technological temperature, prepare the photocatalyst powder of a series of high-ratio surfaces.The method technology is simple, in energy conversion such as solar electrical energy generation and battery energy storage field, aspect environmental protection such as water treatment, has important application prospects.
Summary of the invention
The invention provides a kind of preparation method of tantalates or niobate photocatalyst of high-ratio surface, use tantalum pentoxide (Ta
2O
5) and niobium pentaoxide (Nb
2O
5) these two kinds of cheapnesss, stable raw material, obtain the stable water miscible tantalum or the precursor of niobium, again by polymer complex technology (PC), in order to prepare the method for tantalates and niobate photocatalyst, overcome traditional solid-phase sintering reaction (Solid state reaction, deficiency SSR): the growth of uncontrollable big crystal grain (tens microns of 1-); The stoichiometric proportion loss that volatile components such as alkali metal cause at high temperature evaporation; The local fractional condensation of one or more components.Finally obtained the tantalates of the high-specific surface area more much bigger and the photochemical catalyst of niobates, and the technology synthesis temperature reduces 300-500 ℃ than traditional solid-phase sintering reaction (SSR).
The object of the present invention is achieved like this: the present invention uses niobium pentaoxide or tantalum pentoxide earlier, will be even with potassium hydroxide or NaOH 1: 4 in molar ratio～40 mixed grindings, put into nickel crucible, 400-500 ℃ of calcination reaction 2-4 hour, obtain the melt of potassium niobate (sodium) or potassium tantalate (sodium).Melt is dissolved in deionized water, and the clear liquid after the filtration adds an amount of acetic acid earlier, will produce the niobic acid precipitation (Nb of white in the solution
2O
5NH
2O) or tantalic acid precipitation (Ta
2O
5NH
2O), regulate pH value again, make solution be highly acid (PH＜3), niobium or tantalum in the solution are precipitated out fully with niobic acid or tantalic acid form.After the filtration, white precipitate is washed repeatedly with deionized water earlier, so that remove potassium ion or the sodium ion of the remnants of precipitation absorption.At last, the niobic acid precipitation is added an amount of citric acid (Citric Acid, aqueous solution CA) or an amount of oxalic acid (Oxalic acid, aqueous solution OA) of tantalic acid precipitation adding, under 60 ℃ of condition of heating and stirring, obtain the citrate precursor of water miscible niobium or the oxalates aqueous solution of tantalum.
The tantalates of high-ratio surface of the present invention or the preparation method of niobate photocatalyst, obtain the precursor of stable water miscible tantalum or niobium again in order to preparation tantalates and niobate photocatalyst with said method, according to the prescription component with strontium carbonate, strontium acetate or strontium nitrate, brium carbonate, barium acetate or barium nitrate and lithium carbonate, lithium nitrate or lithium acetate, or rare earth nitrades, mix with the precursor solution of chelating agent EDTA and water miscible tantalum oxalate or citric acid niobium, the mol ratio of chelated metal ion and EDTA is 1: 1-4, add citric acid again, allow the mol ratio of metal ion and citric acid between 1: 4～10, regulate pH value between 7～8 with ammoniacal liquor or ethylenediamine, add proper amount of glycol at last as complexing agent, the mol ratio of ethylene glycol and citric acid is between 2-6, in 60-80 ℃ of heating and stirring, obtain the precursor solution of tantalates and niobate photocatalyst, keep pH value between 7-8.Then in baking oven 130-140 ℃ polyesterification 5-10 hour, in stove 300-400 ℃ calcination 2-4 hour, and, obtain tantalates and niobate photocatalyst powder at 600-900 ℃ of heat treatment 1-8 hour.
Effect of the present invention is: by adopting the precursor of water miscible tantalum or niobium, make the stable a series of tantalates and the precursor solution of niobate photocatalyst, use these precursor solutions, by polymer complex technology (PC), obtained single-phase high-ratio surface photocatalyst powder in lower heat treatment temperature.The method technology is simple, in energy conversion such as solar electrical energy generation and battery energy storage field, aspect environmental protection such as water treatment, has important application prospects.
Description of drawings
Fig. 1 is a water soluble tantalum precursor synthetic schemes of the present invention.
Fig. 2 is the infrared spectrogram of water miscible tantalum precursor of the present invention (a) and niobium precursor (b).
Fig. 3 is the hot TG-DSC figure of the thermogravimetric-Re differential of powder of 140 ℃ of oven dry of water miscible tantalum precursor of the present invention (a) and niobium precursor (b).In the air, 5 ℃/minute of heating rates.
Fig. 4 is the PC preparation technology flow chart of tantalates of the present invention or niobate photocatalyst powder.
Fig. 5 is the XRD spectra of the PC technology of the present invention tantalates photocatalyst powder of deriving.(a) Sr
2Ta
2O
7, 850 ℃, 5 hours; (b) (SrBa)
0.5Ta
2O
6, 750 ℃, 2 hours; (c) LiTaO
3, 600 ℃, 2 hours; (d) La Li doped TaO
3, 650 ℃, 2 hours.
Fig. 6 is the XRD spectra of the PC technology of the present invention niobate photocatalyst powder of deriving.(a) Sr
2Nb
2O
7, 850 ℃, 5 hours; (b) KTiNbO
5, 700 ℃, 2 hours; (c) K
4Nb
6O
17, 650 ℃, 2 hours.
Fig. 7 is the Sr that PC of the present invention and SSR technology are derived
2Ta
2O
7And Sr
2Nb
2O
7The SEM photo of photocatalyst powder.(a) Sr
2Nb
2O
7, PC technology; (b) Sr
2Nb
2O
7, SSR technology; (c) Sr
2Ta
2O
7, PC technology; (b) Sr
2Ta
2O
7, SSR technology.
Fig. 8 is the LiTaO that PC technology of the present invention is derived
3(a) and (SrBa)
0.5Ta
2O
6(b) the TEM photo of photocatalyst powder.
The specific embodiment
1, is fit to the water miscible tantalum of preparation photochemical catalyst and the precursor synthetic method of niobium
Synthesis material: niobium pentaoxide (99.5%), tantalum pentoxide (99.5%), potassium hydroxide or NaOH (down together) (analyzing pure), acetic acid (99.5%), citric acid (99.5%), oxalic acid (99.5%).
The synthesis path of water miscible tantalum precursor: referring to flow chart 1, with Ta
2O
5Even with 1: 20 in molar ratio mixed grinding of KOH, put into nickel crucible, 450 ℃ of calcination reactions 2 hours, obtain the melt of potassium tantalate.Melt is dissolved in deionized water, and the clear liquid after the filtration adds an amount of acetic acid, will produce the tantalic acid precipitation (Ta of white in the solution
2O
5NH
2O), regulate pH value, make solution be acid (PH＜3).After the filtration, white precipitate is washed repeatedly with deionized water earlier, so that remove the potassium ion of the remnants of precipitation absorption.At last, the aqueous solution of the oxalic acid that the adding of tantalic acid precipitation is an amount of, the mol ratio of oxalic acid and tantalum ion is 50～60, and under 60 ℃ of condition of heating and stirring, tantalic acid is dissolved in oxalic acid, after the filtration, obtains the oxalates aqueous solution of stable tantalum.
Synthesis path and Fig. 1 of water miscible niobium precursor are similar: with Nb
2O
5Even with 1: 10 in molar ratio mixed grinding of KOH, put into nickel crucible, 450 ℃ of calcination reactions 2 hours, obtain the melt of potassium niobate.Melt is dissolved in deionized water, and the clear liquid after the filtration adds an amount of acetic acid, will produce the niobic acid precipitation (Nb of white in the solution
2O
5NH
2O), regulate pH value, make solution be acid (PH＜3).After the filtration, white precipitate is washed repeatedly with deionized water, so that remove the potassium ion of remaining absorption.At last, the niobic acid precipitation is added an amount of lemon aqueous acid, the mol ratio of citric acid and niobium ion is 9～10, and under 60 ℃ of condition of heating and stirring, niobic acid is dissolved in citric acid, after the filtration, obtains the citrate aqueous solution of stable niobium.
The content of tantalum or niobium and purity are demarcated by plasma coupled resonance spectrum analysis (ICP) in the precursor solution of water miscible tantalum and niobium, this remaining potassium ion of solution and other foreign ions (Na, Si, Al) be low-down, tantalum and niobium ion content all reach more than 99.5%, match with raw materials used purity.Fig. 2 fourier transform infrared analysis shows: between tantalum ion and the oxalic acid, formed stable coordinate bond between niobium ion and the citric acid, can need not to take under the special safeguard procedures situation long preservation under room temperature state.The hot analytical test of Fig. 3 (TG-DSC) shows: water miscible tantalum precursor is finished thermal decomposition at 380 ℃, and water miscible niobium precursor is finished thermal decomposition at 500 ℃.
2, the preparation method of tantalates and niobate photocatalyst
The water miscible tantalum that synthesizes above using or the precursor of niobium can prepare a series of high-ratio surface tantalates and niobate photocatalyst powder.The for example tantalates of alkali metal containing and alkaline-earth metal and niobates, Sr
2(Ta
2-xNb
x) O
7, (x=0-2), ATaO
3, (A=Li, Na, K), (Sr
xBa
1-x) Ta
2O
6, (x=0-1); The photochemical catalyst of rare-earth-doped modification, as: the ATaO of La element doping
3Laminated perovskite niobates series, A (M
N-1Nb
nO
3n+1), (A=K, Ru, Cs, M=La, Ca, Ti), as K
4Nb
6O
17, KTiNbO
5, KLaNb
2O
7AndCsCa
2Nb
3O
10Deng, all have outstanding photocatalytic activity.The InTaO that also has visible-light response type
4And InNbO
4The oxide semiconductor photochemical catalyst.Sr
2(Ta
2-xNb
x) O
7, ATaO
3, (A=Li, Na, K), (Sr
xBa
1-x) Ta
2O
6, mix the LaTaO of La
3And K
4Nb
6O
17, KTiNbO
5, laminated perovskite niobates series, A (M
N-1Nb
nO
3n+1), (A=K, Ru, Cs, M=La, Ca, Ti), as K
4Nb
6O
17, KTiNbO
5, KLaNb
2O
7And CsCa
2Nb
3O
10
Illustrate the preparation technology of tantalates and niobate photocatalyst powder below:
Fig. 4 is preparation technology's flow chart of tantalates or niobate photocatalyst powder.
(1) .Sr
2(Ta
2-xNb
x) O
7The preparation of precursor solution and powder are synthetic: according to chemical formula Sr
2(Ta
2-xNb
x) O
7(x=0～2) with the strontium carbonate (or strontium acetate or strontium nitrate) of metering ratio, are dissolved in the aqueous solution of chelating agent EDTA, and the mol ratio of Sr and EDTA is 1-4, regulate pH value to 7-8 with ammoniacal liquor (or ethylenediamine).Mix necessarily measuring the water miscible citric acid niobium of ratio and the precursor solution of tantalum oxalate, regulate citric acid content, the mol ratio that makes metal ion and citric acid is 1: between (4～10), add ammoniacal liquor (or ethylenediamine) and regulate pH value between 7～8.Top two solution are mixed, and add proper amount of glycol,, obtain Sr in 60-80 ℃ of heating and magnetic agitation as complexing agent (mol ratio of ethylene glycol and citric acid is between 2-6)
2(Ta
2-xNb
x) O
7Precursor solution, keep pH value between 7-8.Then in baking oven 130-140 ℃ polyesterification 5-10 hour, obtain the thickness body of burgundy.In Muffle furnace 350 ℃ calcination 2-4 hour, obtain black powder.In 850-900 ℃ of heat treatment 5 hours (750-800 ℃ with 8 hours), obtain the Sr of white at last
2(Ta
2-xNb
x) O
7Powder.X gets the scope of 0-2, realizes by the addition that changes water miscible citric acid niobium and tantalum oxalate.
(2). (Sr
xBa
1-x) Ta
2O
6The preparation of precursor solution and powder are synthetic: according to chemical formula (Sr
xBa
1-x) Ta
2O
6(x=0～1) with the strontium carbonate (or strontium acetate or strontium nitrate) and the brium carbonate (or barium acetate or barium nitrate) of metering ratio, is dissolved in the aqueous solution of chelating agent EDTA, and the mol ratio of Sr or Ba and EDTA is 1-4, regulates pH value to 7-8 with ammoniacal liquor (or ethylenediamine).Will necessarily measure the precursor solution of water miscible tantalum oxalate of ratio add citric acid, allow the mol ratio of metal ion and citric acid 1: between (4～10), to add ammoniacal liquor (or ethylenediamine) adjusting pH value between 7～8.Top two solution are mixed, and add proper amount of glycol,, obtain (Sr in 60-80 ℃ of heating and magnetic agitation as complexing agent (mol ratio of ethylene glycol and citric acid is between 2-6)
xBa
1-x) Ta
2O
6Precursor solution, keep pH value between 7-8.Then in baking oven 130-140 ℃ polyesterification 5-10 hour, obtain the thickness body of burgundy.In Muffle furnace 350 ℃ calcination 2-4 hour, obtain black powder.750-850 ℃ of heat treatment 2 hours, obtain (the Sr of white at last
xBa
1-x) Ta
2O
6Powder.
(3) .LiTaO
3LiTaO with the rare earth La doping
3The preparation of precursor solution and powder are synthetic: the lithium carbonate (or lithium nitrate or lithium acetate) that will measure ratio adds the precursor solution of water miscible tantalum oxalate, add EDTA, the mol ratio that makes Li and EDTA is 1-4, add citric acid again, allow the mol ratio of metal ion and citric acid 1: between (4～10), regulate pH value between 7～8 with ammoniacal liquor (or ethylenediamine), add proper amount of glycol at last as complexing agent (mol ratio of ethylene glycol and citric acid is between 2-6), in 60-80 ℃ of heating and magnetic agitation, obtain LiTaO
3Precursor solution, keep pH value between 7-8.Then in baking oven 130-140 ℃ polyesterification 5-10 hour, obtain the solid of black.In Muffle furnace 350 ℃ calcination 2-4 hour, obtain black powder.600-650 ℃ of heat treatment 2 hours, obtain the LiTaO of white at last
3Powder.The LiTaO that rare earth La mixes
3The precursor solution preparation: as long as increase by a step rare earth lanthanum nitrate is dissolved in the aqueous solution of chelating agent EDTA by doping (molar percentage 0.5-2.5), the mol ratio of La and EDTA is 1-4, regulates pH value to 7-8 with ammoniacal liquor (or ethylenediamine).Again with LiTaO
3Precursor solution mixes, and promptly gets the LiTaO that La mixes
3Precursor solution.The heat treatment step of back and LiTaO
3Precursor solution is identical, obtains the LiTaO of the La doping of white at last
3Powder.
(4) .K
4Nb
6O
17The preparation of precursor solution and powder are synthetic: the potash (or potassium nitrate or potassium acetate) that will measure ratio adds the precursor solution of water miscible citric acid niobium, regulate citric acid content, the mol ratio that makes metal ion and citric acid is 1: between (4～10), regulate pH value between 7～8 with ammoniacal liquor (or ethylenediamine), add proper amount of glycol at last as complexing agent (mol ratio of ethylene glycol and citric acid is between 2-6), in 60-80 ℃ of heating and magnetic agitation, obtain K
4Nb
6O
17Precursor solution.Then in baking oven 130-140 ℃ polyesterification 5-10 hour, obtain the thickness body of black.In Muffle furnace 350 ℃ calcination 2-4 hour, obtain black powder.700-750 ℃ of heat treatment 2 hours, obtain the K of white at last
4Nb
6O
17Powder.
(5) .KTiNbO
5The preparation of precursor solution and powder are synthetic: the tetrabutyl titanate (or isopropyl titanate) that will measure ratio adds in an amount of glacial acetic acid, more an amount of citric acid is dissolved in wherein; The precursor solution that the potash (or potassium nitrate or potassium acetate) of metering ratio is added water miscible citric acid niobium; Top two solution are mixed, regulate citric acid content, the mol ratio that makes metal ion and citric acid is 1: between (4～10), regulate pH value between 7～8 with ammoniacal liquor (or ethylenediamine), add proper amount of glycol at last as complexing agent (mol ratio of ethylene glycol and citric acid is between 2-6), in 60-80 ℃ of heating and magnetic agitation, obtain KTiNbO
5Precursor solution.Then in baking oven 130-140 ℃ polyesterification 5-10 hour, obtain black thickness body.In Muffle furnace 350 ℃ calcination 2-4 hour, obtain black powder.700-800 ℃ of heat treatment 2 hours, obtain the KTiNbO of white at last
5Powder.In addition, in order to contrast with above-mentioned polymer complex technology based on water soluble tantalum and niobium precursor, we also adopt traditional solid-phase sintering reaction, utilize Ta
2O
5And Nb
2O
5With the oxide of other metals or carbonate as parent material, synthesized Sr at 1100-1300 ℃ of sintering 10-20 hour
2Ta
2O
7, Sr
2Nb
2O
7, SrTa
2O
6, SrNb
2O
6, Sr
0.5Ba
0.5Ta
2O
6, KTiNbO
5Deng photochemical catalyst.
3, the sign of tantalates and niobate photocatalyst
Fig. 5 and Fig. 6 have provided the tantalates that polymer complex technology derives and the X ray diffracting spectrum of niobate photocatalyst respectively.As can be seen, adopt the precursor of water miscible tantalum or niobium, Sr
2Ta
2O
7And Sr
2Nb
2O
7In the crystallization in 5 hours of 850 ℃ of sintering, obtained the crystal structure of pure phase, there is not parafacies to be detected, obtained the very good powder of crystalline quality in 5 hours at 900 ℃ of sintering; And traditional Sr of reported in literature
2Ta
2O
7And Sr
2Nb
2O
7The temperature and time of solid-phase sintering reaction is respectively 1180 ℃ (200 hours) and 1100 ℃ (150 hours).We adopt traditional solid-phase sintering method 1200 ℃ 10 hours, obtained the Sr of pure phase
2Ta
2O
7And Sr
2Nb
2O
7Powder.As seen adopt the precursor of water miscible tantalum or niobium, adopt polymer complex technology, significantly reduced crystallization temperature.The Sr that the polymer precursor base is derived
0.5Ba
0.5Ta
2O
6And KTiNbO
5Crystal temperature effect be respectively 750 ℃ and 700 ℃, the crystallization temperature of solid-phase sintering reaction is respectively 1300 and 1100 ℃.The K that other polymer precursor bases are derived
4Nb
6O
17And LiTaO
3In lower crystallization temperature, be respectively 700 and 600 ℃, just can obtain pure phase, avoided the K that high temperature causes or the volatilization of Li element.And the LiTaO that La mixes
3Powder owing to used polymer precursor solution technology, make a small amount of La element can with LiTaO
3Precursor reaches molecular ion level mixed-level, and the doping powder of preparing has uniform composition and distributes, and has solved the normal uneven problem of dopant profiles that exists in the solid phase reaction sintering.In addition, all contain alkali metal potassium or sodium element in many photochemical catalysts, owing to us synthesizing water-solubility tantalum or niobium precursor, what adopt is the alkaline auxiliary solvent method of potassium hydroxide or sodium, therefore synthetic when containing the photochemical catalyst of alkali metal potassium or sodium element, cleaning during water soluble tantalum or niobium precursor are synthetic can be simplified, and very helps the reduction of cost.Influencing a key factor of photochemical catalyst photocatalytic activity, is exactly the specific area of photochemical catalyst and the pattern of powder.Adopt traditional BET method, we have measured the tantalates that the reaction of polymer precursor base and solid-phase sintering derives and the specific area of niobate photocatalyst, are listed in the table 1.Find out easily,,, obtained than solid phase reaction sintered powder (0.5-3m by polymer precursor technology with the precursor of water miscible tantalum or niobium
2/ g) much higher specific area is usually at 8-36m
2/ g.For example: the Sr of polymer precursor base preparation
2Ta
2O
7And Sr
2Nb
2O
7Specific area be respectively 9.5 and 10.7m
2/ g, and the specific area of corresponding solid phase reaction sintered powder is respectively 2.5 and 1.3m
2/ g.(SrBa) that PC derives
0.5Ta
2O
6The specific area 15.2m of powder
2/ g, solid-phase sintering powder only are 0.9m
2The photochemical catalyst that other PC of/g. derive.
As LiTaO
3LiTaO with the La doping
3Specific area near 10m
2/ g, KTiNbO
5And K
4Nb
6O
17Have bigger specific area, be respectively 35.7 and 26.8m
2/ g. ESEM and transmission electron microscopy are utilized to observe the pattern and the size of top photocatalyst powder.As shown in Figure 7 and Figure 8.Among Fig. 7, the Sr that PC technology is derived
2Nb
2O
7Powder has loose porous pattern, and crystal particle scale is about 50 nanometers, and the powder that solid-phase sintering SSR technology obtains, crystallite dimension is at the 1-1.5 micron, and the smooth densification of grain surface.Such pattern difference just in time is reflected in the obvious difference of specific area.The Sr that derives of PC technology in like manner
2Ta
2O
7The powder grain yardstick is in the 100-200 nanometer, and the powder that solid-phase sintering SSR technology obtains, crystallite dimension is at the 0.5-1.0 micron.Among Fig. 8, the LiTaO that PC technology is derived
3(SrBa)
0.5Ta
2O
6The particle diameter of photocatalyst powder is respectively between 20-30 nanometer and 50-100 nanometer.As seen PC technology is well suited for the powder of preparation scale between tens～200 nanometers.
The tantalates that table 1, polymer precursor base and solid-phase sintering reaction are derived and the specific area of niobate photocatalyst
| Photochemical catalyst | The preparation method | Sintering temperature (℃) | Sintering time (hour) | Specific area (m 2/g) |
| Sr 2Ta 2O 7 | PC | 850 | 5 | 9.5 |
| SSR | 1200 | 10 | 2.4 | |
| Sr 2Nb 2O 7 | PC | 850 | 5 | 10.7 |
| PC | 900 | 5 | 8.6 | |
| SSR | 1200 | 10 | 1.3 | |
| (SrBa) 0.5Ta 2O 6 | PC | 750 | 2 | 15.2 |
| SSR | 1200 | 10 | 0.9 | |
| LiTaO 3 | PC | 600 | 2 | 9.9 |
| La-doped LiTaO 3 | PC | 650 | 2 | 9.7 |
| KTiNbO 5 | PC | 700 | 2 | 35.7 |
| K 4Nb 6O 17 | PC | 650 | 2 | 26.8 |
| PC | 750 | 2 | 15.9 |
*PC representation polymer combination process, SSR are represented the solid-phase sintering reaction.
Claims (3)
1, the preparation method of the tantalates of high-ratio surface and niobate photocatalyst, it is characterized in that using tantalum pentoxide or niobium pentaoxide to be raw material earlier, niobium pentaoxide or tantalum pentoxide and potassium hydroxide or NaOH 1: 2 in molar ratio～20 mixed grindings is even, put into corundum crucible, 400-550 ℃ of calcination reaction 2-4 hour, obtain the melt of potassium niobate or sodium niobate or potassium tantalate or tantalic acid sodium respectively; Melt is dissolved in deionized water, and the clear liquid after the filtration adds an amount of acetic acid earlier, produce the niobic acid precipitation or the tantalic acid precipitation of white in the solution, use the nitre acid for adjusting pH value again, make solution be the highly acid of pH＜2, niobium or tantalum in the solution are precipitated out fully with niobic acid or tantalic acid form; Remove potassium ion or the sodium ion of the remnants of precipitation absorption; Lemon aqueous acid that the adding of niobic acid precipitation is an amount of or tantalic acid precipitation add the aqueous solution of an amount of oxalic acid, obtain the oxalates aqueous solution of water miscible niobium precursor or tantalum; Prepare tantalates and niobate photocatalyst Sr with the water miscible niobium precursor of said method acquisition and the oxalates aqueous solution of tantalum
2(Ta
2-xNb
x) O
7X=0～2:
To measure strontium carbonate, strontium acetate or the strontium nitrate of ratio according to described chemical formula, and be dissolved in the aqueous solution of chelating agent EDTA, the mol ratio of Sr and EDTA is 1-4, regulates the pH value between the 7-8 with ammoniacal liquor or ethylenediamine; The precursor solution of water miscible citric acid niobium and tantalum oxalate is mixed, add citric acid, regulate citric acid content, the mol ratio that makes metal ion and citric acid is regulated the pH value between 7～8 with ammoniacal liquor or ethylenediamine between 1: 4～10, above-mentioned two solution are mixed, and add proper amount of glycol as complexing agent, the mol ratio of ethylene glycol and citric acid in 60-80 ℃ of heating and stirring, obtains Sr between 2-6
2(Ta
2-xNb
x) O
7Precursor solution, keep pH value between 7-8, then in baking oven 130-140 ℃ polyesterification 5-10 hour, obtain the thickness body of burgundy, in Muffle furnace 350 ℃ calcination 2-4 hour, the acquisition black powder; 850-900 ℃ of heat treatment 5 hours, obtain the Sr of white at last
2(Ta
2-xNb
x) O
7Powder photocatalyst.
2, the preparation method of the tantalates photochemical catalyst of high-ratio surface, it is characterized in that using tantalum pentoxide to be raw material earlier, tantalum pentoxide and potassium hydroxide or NaOH 1: 2 in molar ratio～20 mixed grindings is even, put into corundum crucible, 400-550 ℃ of calcination reaction 2-4 hour, obtain the melt of potassium tantalate or tantalic acid sodium respectively; Melt is dissolved in deionized water, and the clear liquid after the filtration adds an amount of acetic acid earlier, produces the tantalic acid precipitation in the solution, uses the nitre acid for adjusting pH value again, makes solution be the highly acid of pH＜2, and the tantalum in the solution is precipitated out fully with the tantalic acid form; Remove potassium ion or the sodium ion of the remnants of precipitation absorption; Tantalic acid is precipitated the aqueous solution that adds an amount of oxalic acid, obtain the oxalates aqueous solution of water miscible tantalum; With the precursor of water miscible tantalum in order to preparation tantalates photochemical catalyst (Sr
xBa
1-x) Ta
2O
6X=0～1: strontium carbonate, strontium acetate or the strontium nitrate that will measure ratio according to described chemical formula, with brium carbonate, barium acetate or barium nitrate, be dissolved in the aqueous solution of chelating agent EDTA, the mol ratio of Sr or Ba and EDTA is 1-4, regulates pH value between the 7-8 with ammoniacal liquor or ethylenediamine; The precursor solution of water miscible tantalum oxalate is added citric acid, allow the mol ratio of metal ion and citric acid between 1: 4～10, add ammoniacal liquor or ethylenediamine adjusting pH value between 7～8; Top two solution are mixed, and add proper amount of glycol as complexing agent, the mol ratio of ethylene glycol and citric acid in 60-80 ℃ of heating and magnetic agitation, obtains (Sr between 2-6
xBa
1-x) Ta
2O
6Precursor solution, keep pH value between 7-8, then in baking oven 130-140 ℃ polyesterification 5-10 hour, the thickness body of acquisition burgundy; At 350 ℃ of calcination 2-4 hours, obtain black powder; 750-850 ℃ of heat treatment 2 hours, obtain (the SrxBa of white at last
1-x) Ta
2O
6Powder photocatalyst.
3, the preparation method of the tantalates photochemical catalyst of high-ratio surface, it is characterized in that using tantalum pentoxide to be raw material earlier, tantalum pentoxide and potassium hydroxide or NaOH 1: 2 in molar ratio～20 mixed grindings is even, put into corundum crucible, 400-550 ℃ of calcination reaction 2-4 hour, obtain the melt of potassium tantalate or tantalic acid sodium respectively; Melt is dissolved in deionized water, and the clear liquid after the filtration adds an amount of acetic acid earlier, produces the tantalic acid precipitation in the solution, uses the nitre acid for adjusting pH value again, makes solution be the highly acid of pH＜2, and the tantalum in the solution is precipitated out fully with the tantalic acid form; Remove potassium ion or the sodium ion of the remnants of precipitation absorption; Tantalic acid is precipitated the aqueous solution that adds an amount of oxalic acid, obtain the oxalates precursor solution of water miscible tantalum; With the oxalates precursor solution of water miscible tantalum in order to preparation LiTaO
3Or the LiTaO of rare earth La doping
3Catalyst:
The precursor solution that lithium carbonate, lithium nitrate or the lithium acetate of metering ratio is added water miscible tantalum oxalate, add EDTA, the mol ratio that makes Li and EDTA is 1-4, add citric acid again, allow the mol ratio of metal ion and citric acid between 1: 4～10, regulate the pH value between 7～8 with ammoniacal liquor or ethylenediamine, add proper amount of glycol at last as complexing agent, the mol ratio of ethylene glycol and citric acid in 60-80 ℃ of heating and magnetic agitation, obtains LiTaO between 2-6
3Precursor solution, keep the pH value between 7-8; Then in baking oven 130-140 ℃ polyesterification 5-10 hour, obtain the solid of black; In Muffle furnace 350 ℃ calcination 2-4 hour, obtain black powder, at last 600-650 ℃ of heat treatment 2 hours, obtain the LiTaO of white
3Powder photocatalyst;
Or further make rare earth La Li doped TaO
3Photochemical catalyst: the rare earth lanthanum nitrate is dissolved in the aqueous solution of chelating agent EDTA by doping molar percentage 0.5-2.5, and the mol ratio of La and EDTA is 1-4, regulates the pH value to 7-8, again with aforementioned LiTaO with ammoniacal liquor or ethylenediamine
3Precursor solution mix, promptly get the LiTaO of La doping
3Precursor solution, obtain the LiTaO that La mixes through identical heat treatment step
3Powder photocatalyst.
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