CN104857960B - Graphene is oriented to multilevel hierarchy composite oxide catalysts and preparation method thereof - Google Patents
Graphene is oriented to multilevel hierarchy composite oxide catalysts and preparation method thereof Download PDFInfo
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Abstract
A kind of graphene is oriented to multilevel hierarchy composite oxide catalysts and preparation method thereof, belongs to environmental catalysis technical field.The coprecipitation modified using lemon acid dispersant and complexing agent prepares multilevel hierarchy LDHs nano-chip arrays/Graphene hybrid materials of Graphene template directions, then the hybrid material is moderately calcined, template direction effect based on graphene, the composite oxides for making LDHs nano-chip arrays be formed in roasting have remained in that three-dimensional manometer chip arrays pattern, and its composite oxides nanometer sheet is the pore structure for being assembled by the oxide particle of small particle and being had prosperity.The novel multilevel hierarchy composite oxide catalysts show more simple LDHs roasting in removing nitrogen oxides and carbon-smoke combustion reaction obtained by the catalytic activity that significantly improves of oxide, overcome the shortcoming that LDHs nanometer sheets caused by traditional preparation methods are easily reunited.
Description
Technical field
The invention belongs to environmental catalysis technical field, in particular, provide a kind of graphene and be oriented to multilevel hierarchy combined oxidation
Thing catalyst and preparation method thereof, the composite oxide catalysts can be effectively used for environmental contaminants (nitrogen oxide NOx and soot
Particle Soot) removing.
Technical background
In recent decades, because Diesel engine (diesel engines) has high fuel efficiency and stable durability
Can, it is widely used on all kinds of vehicles, such as bus, light-duty or heavy truck.However, Diesel engine
In tail gas include the harmful substance such as various nitrogen oxides (NOx) and carbon soot particles (Soot), the environment that we are depended on for existence and
Human health causes serious harm.In current removing NOx and Soot catalyst, Pt bases catalyst is due to its high activity
And stability, receive extensive research.However, because Pt Precious Metals Resources are valuable and non-renewable, therefore Development of Novel, height
It is an important research direction that the non-Pt bases catalyst of transition metal oxide of effect, which is used to remove NOx and Soot pollutants,.
Hydrotalcite (Layered Double Hydroxides, abbreviation LDHs) is put down by positively charged laminate and interlayer
Weigh lamellar compound formed by anion ordered fabrication, and LDHs can obtain uniform metal composite oxide through appropriateness roasting
(Layered Double Oxides, abbreviation LDOs).LDHs and its derivative metal composite oxide LDOs can because of its chemical composition
The homogeneous and intrinsic alkalescence of modulation, Elemental redistribution, excellent catalytic activity is shown in environmental catalysis field.However, traditional is total to
The precipitation method are carried out, reaction rate is fast, nucleation time is asynchronous as LDHs customary preparation methods due to reacting in same phase,
LDHs nanometer sheet sizes obtained by causing are uneven, controllability is poor, and the LDHs nanometer sheets particle aggregation effect thus generated is strong, divide
Scatter-difference, high-temperature roasting are easily sintered, and above-mentioned reason substantially constrains height of the metal composite oxide LDOs in catalytic reaction
Effect is utilized.
To prevent the sintering of oxide particle in catalyst, an effective method is by Gao Bibiao in preparation process
The scattered and growth of the template contral nano-particle of area or specific structure, so as to obtain high dispersive, small size and with specific
The metal oxide catalyst of pattern, and then improve catalytic activity.Such as Kwak (Kwak G, Hwang J, Cheon J Y, et
Al.J.Phys.Chem.C, 2013,117,1773-1779) using ordered mesoporous carbon material CMK-3 as sacrifice template, using etc. body
Mesoporous carbon template is impregnated in certain density Co (NO by product infusion process3)2In solution, obtained mixture is empty in flowing after drying
The i.e. available 6~10nm of roasting small size Co in gas3O4Mealy oxide catalyst, for being shown in Fischer-Tropsch synthesis
Excellent catalytic activity.(the Chinese invention patents such as Zhang：ZL201310106570.4 it is) growth with graphene (Graphene)
Template, Graphene surfaces are carried on using traditional coprecipitation by LDHs nanometer sheets, show that LDHs nanometer sheets are put down at random
Paving is distributed in the shape characteristic on Graphene surfaces, and high-specific surface area, small particle are can obtain after the composite is calcined
Co3O4Mealy oxide catalyst (80~110m of specific surface area2/ g, pore-size distribution be mesoporous distribution, pore volume 0.3~
0.4cm3/ g), so as to significantly improve its NOx storage activity.Although in the preparation of heterogeneous catalysis material, by nano material group
Dressing up the high-dimensional multilevel structure materials such as the nanometer rods (1D), nanometer sheet (2D) or nanoparticle (3D) of specific morphology can be
The property of uniqueness is shown in a variety of catalytic reactions, but in current research, prepares LDHs by Graphene templates and derives
Three-dimensional (3D) the metal composite oxide nano-chip arrays catalyst of multilevel hierarchy there is not been reported.
The content of the invention
Multilevel hierarchy composite oxide catalysts and its preparation side are oriented to it is an object of the invention to provide a kind of graphene
Method, preparation process is easy and avoids the operating condition of HTHP and the use of a large amount of organic reagents.The multilevel hierarchy pattern
Metal composite oxide shows small size, the feature of high dispersive, substantially increases it in removing NOxAnd urging in Soot reactions
Change activity.
The coprecipitation that the present invention is modified using lemon acid dispersant and complexing agent first prepares Graphene templates
The hybrid material, is then moderately calcined, based on stone by multilevel hierarchy LDHs nano-chip arrays/Graphene hybrid materials of guiding
The template direction effect of black alkene, makes the composite oxides that LDHs nano-chip arrays are formed in roasting remain in that three-dimensional manometer
Chip arrays pattern, its composite oxides nanometer sheet is the hole knot for being assembled by the oxide particle of small particle and being had prosperity
Structure.The novel multilevel hierarchy composite oxide catalysts are in removing nitrogen oxides (NOx) and soot (Soot) combustion reaction
Show the catalytic activity that more simple LDHs roastings gained oxide is significantly improved.
The multilevel hierarchy composite oxide catalysts of the graphene template direction of the present invention are Multilevel-structure hydrotalcite
(LDHs) in nano-chip arrays/graphene (Graphene) hybrid material, graphene quality is the 8%~25% of LDHs mass,
LDHs nanometer sheets size range is 20~120nm, and thickness~5nm, pattern is that LDHs nanometer sheets are orthogonal, is staggeredly grown on stone
Mertenyl face both sides, form three-dimensional " honeycomb " shape array pattern；The hybrid material is calcined, the template direction based on graphene is made
With the composite oxides for making LDHs nano-chip arrays be formed in roasting have remained in that three-dimensional manometer chip arrays pattern, and it is answered
Closing oxide nano-slice (thickness is 7~12nm) is assembled by the oxide particle (8~10nm) of small particle and with hair
The pore structure reached, obtains multilevel hierarchy composite oxide catalysts.
The present invention preparation process and its principle be：Graphene oxide is inhaled with strong electrostatic force first in initial preparation
Metal cation in attached salting liquid, while citric acid is as dispersant, can effectively facilitate metal cation in graphene oxide
Surface is dispersed；Then, with NaOH/Na2CO3Mixed alkali liquor be precipitating reagent, surface of graphene oxide absorption metal sun from
Son can in-situ preparation high dispersive LDHs crystal seeds, while citric acid reduces LDHs nucleation, growth rate as complexing agent, control
LDHs crystal seeds processed are in surface of graphene oxide original position, slow growth；After the completion of crystallization, graphene oxide is reduced in strong base solution
For Graphene, multilevel hierarchy LDHs nano-chip arrays/Graphene hybrid materials are obtained.The shape characteristic table of the hybrid material
It is now the LDHs nanometer sheets vertical-growth that intermeshes in the both sides of Graphene basal planes, forms three-dimensional " honeycomb " shape array shape
Looks, the hybrid material is calcined, the effect of template direction based on graphene, makes what LDHs nano-chip arrays were formed in roasting to answer
Close oxide and remained in that three-dimensional manometer chip arrays pattern, its composite oxides nanometer sheet is the oxide particle by small particle
Assemble and have the pore structure of prosperity, obtain multilevel hierarchy composite oxide catalysts.Its preparation method includes following
Step：
(1) it is that raw material prepares graphite oxide using chemical oxidization method with natural flake graphite (325 mesh), drying mode is used
Freeze-drying condition, prior to -60 DEG C at freeze 1h, under vacuum condition dry 12h after obtain fluffy graphite oxide, will
The above-mentioned graphite oxide of set amount is scattered in deionized water, and uniform graphene oxide colloidal is can obtain after ultrasonic disperse
Suspension.
(2) metal salt and citric acid are dissolved in deionized water simultaneously and obtain mixed solution A.Then in lasting stirring bar
The graphene oxide colloidal suspension in step 1 is poured slowly into mixed solution A under part, gained slurries are surpassed while stirring
Sound, obtains brown color slurries B.
(3) by NaOH, Na2CO3It is dissolved in simultaneously in deionized water and mixed ammonium/alkali solutions C is made.By the palm fibre obtained in step 2
Yellow slurry B and mixed ammonium/alkali solutions C is slowly dropped into the four-hole boiling flask for filling 100mL deionized waters simultaneously, controls pH=10
± 0.1, then in crystallization under water bath condition, gained black precipitate is washed with deionized to pH=7, obtains many after freeze-drying
Level structure LDHs nano-chip arrays/Graphene hybrid materials.
(4) corresponding multilevel hierarchy metal composite oxide will be can obtain after the hybrid material in step 3 moderately roasting to urge
Agent.
The mass ratio of graphite oxide and deionized water used described in step (1) is 2:1, obtained graphene oxide glue
Body shape suspension concentration is 2mg/mL, and ultrasonic power is 300W, and ultrasonic time control is 0.5h~1h.
Metal salt described in step (2) includes the metal salt of divalence and trivalent, and its existence form is nitrate or acetic acid
Bivalent metal ion (M2+) in one kind or its mixed form in salt, metal salt is one in Co2+, Ni2+, Mg2+, Mn2+
Kind or two kinds of combinations, trivalent metal ion (M3+) is one kind in Al3+, Fe3+, and M2+ and M3+ molar ratio are fixed as [M2
+]/[M3+]=3：1.
The mass ratio of citric acid and graphite oxide used described in step (2) is 0.5:1~1.5:1, per 100mg lemons
Total ionizable metal salt [the M of acid 0.005~0.02mol of correspondence2++M3+], graphene oxide colloidal suspension and mixed solution A
Volume ratio control is 3:1~5:1, ultrasonic power is 300W, and ultrasonic time control is 10min~30min.
In the mixed base of every 100mL volumes described in step (3), [NaOH]/[M2++M3+] molar ratio be 1.6：1,
[Na2CO3]/[M3+] molar ratio be 2：1, time for adding is maintained between 30~60min, and crystallization temperature selection is 60~90
DEG C, the time is 4~24h, and the freezing dry process of the same step of drying condition (1) obtains multilevel hierarchy M2+ 3M3+ 1- LDHs nanometer sheets
Array/Graphene hybrid materials.
Roasting condition selection described in step (4) is 5 DEG C/min of heating rate 400~600 DEG C in still air, is protected
The time is held for 4h, multilevel hierarchy M is obtained2+ 3M3+ 1(O) metal composite oxide.
It is pointed out that the chemical oxidization method that the preparation of graphite oxide is used in the present invention is with reference to the conjunction reported before
Into method (bibliography Kovtyukhova N I, Chem.Mater., 1999,11,771-778), including following corrective measure：
(1) pre-oxidation of graphite.Successively by the dense H of 24mL2SO4(mass fraction 98%), 5g K2S2O8With 5g P2O5Add
Into four-hole boiling flask, stirring is lower to add 10g graphite powders, reaction 6h is stirred vigorously in 80 DEG C of water-baths, then by four-hole boiling flask certainly
Room temperature so is cooled to, is washed with deionized to pH=7,60 DEG C are dried to obtain pre-oxidation graphite powder.
(2) preparation of graphite oxide.The dense H of 115mL are measured in four-hole boiling flask2SO4, it is successively that 5g is pre- under agitation
Graphite oxide powder and 2.5g NaNO3It is added to dense H2SO4In, and it is slowly added to 15g KMnO4, controlled under the conditions of ice-water bath anti-
Answer temperature to be no more than 4 DEG C, stir 90min；Then four-hole boiling flask is transferred in 35 DEG C of water bath with thermostatic control, stirs 30min；Remove
After water-bath, deionized water is added while stirring, reaction system very exothermic, controlling reaction temperature is stirred between 95~98 DEG C
15min；When continuing to add water and temperature of reaction system is no longer raised, about 200mL deionized waters are rapidly joined, then with 30~50mL
H2O2(mass fraction 5%) handles reaction solution to golden yellow is presented, and is then fully washed into filtrate without SO with 5%HCl4 2-
(with BaCl2Solution detection is without precipitation), finally it is washed with deionized again and is precipitated to pH=7.By above-mentioned sample at -60 DEG C
Freezing 1h, fluffy graphite oxide is obtained after drying 12h under vacuum condition in advance.
The present invention has advantages below and feature compared with prior art：
(1) present invention is by introducing graphene template, the co-precipitation modified first using lemon acid dispersant and complexing agent
Route prepares multilevel hierarchy LDHs nano-chip arrays/Graphene hybrid materials, is then moderately calcined the hybrid material
Three-dimensional metal composite oxide nano-chip arrays catalyst is obtained, oxide particle shows small chi in the multilevel hierarchy catalyst
Very little, high dispersive feature.The preparation process of the invention is easy, it is to avoid the operating condition of HTHP and a large amount of organic reagents
Use, with good commercial application prospect.
(2) the multilevel hierarchy oxide catalyst is in Catalytic Decomposition of Nitric Oxide (NOx) and soot (Soot) combustion reaction
In show the catalytic activity that more simple LDHs roasting gained oxide is significantly improved, overcome conventional method and prepare LDHs bases and answer
The shortcoming of oxide catalyst high temperature easy-sintering is closed, the application of hydrotalcite and grapheme material in catalytic field has been widened.
Brief description of the drawings
Fig. 1 is the XRD spectra of graphite oxide sample in embodiment 1-5.
Fig. 2 is the SEM figures of graphite oxide sample in embodiment 1-5.
Fig. 3 is the multilevel hierarchy Co of embodiment 12Mg1Al1The SEM figures of-LDHs nano-chip arrays/Graphene hybrid materials.
Fig. 4 is the multilevel hierarchy metal composite oxide Co of embodiment 12Mg1Al1(O) SEM figures.
Fig. 5 is the multilevel hierarchy metal composite oxide Co of embodiment 12Mg1Al1(O) TEM figures.
Fig. 6 is the multilevel hierarchy Ni of embodiment 22Mg1Al1The SEM figures of-LDHs nano-chip arrays/Graphene hybrid materials.
Fig. 7 is the multilevel hierarchy Ni of embodiment 32.5Mn0.5Fe1The SEM of-LDHs nano-chip arrays/Graphene hybrid materials
Figure.
Embodiment
Following embodiments are further illustrating using as the explaination to the technology of the present invention content for present invention, but
Embodiments of the present invention are not limited to following preparation parameters, one of ordinary skill in the art can with and should know to appoint
What simple change based on true spirit, replacement all should belong to protection domain of the presently claimed invention.
Embodiment 1：
Step 1：Graphite oxide is prepared using chemical oxidization method by raw material of natural flake graphite.Specifically include two steps：(1)
The pre-oxidation of graphite.Successively by the dense H of 24mL2SO4(mass fraction 98%), 5g K2S2O8With 5g P2O5It is added to four-hole boiling flask
In, stirring is lower to add 10g graphite powders, and reaction 6h is stirred vigorously in 80 DEG C of water-baths, four-hole boiling flask then is naturally cooled into room
Temperature, is washed with deionized to pH=7, and 60 DEG C are dried to obtain pre-oxidation graphite powder.(2) preparation of graphite oxide.In four mouthfuls of burnings
The dense H of 115mL are measured in bottle2SO4, 5g is pre-oxidized into graphite powder and 2.5g NaNO successively under agitation3It is added to dense H2SO4
In, and it is slowly added to 15g KMnO4, controlling reaction temperature is no more than 4 DEG C under the conditions of ice-water bath, stirs 90min；Then by four
Mouth flask is transferred in 35 DEG C of water bath with thermostatic control, stirs 30min；Remove after water-bath, deionized water, reaction system are added while stirring
Very exothermic, controlling reaction temperature stirs 15min between 95~98 DEG C；When continuing to add water and temperature of reaction system no longer rises
Gao Shi, rapidly joins about 200mL deionized waters, then with 30~50mL H2O2(mass fraction 5%) processing reaction solution is in cash
Yellow, is then fully washed into filtrate without SO with 5%HCl4 2-(with BaCl2Solution detection is without precipitation), deionization is finally used again
Water washing is precipitated to pH=7.By above-mentioned sample in freezing 1h at -60 DEG C in advance, obtained after drying 12h under vacuum condition
In 2 θ=10 in fluffy graphite oxide, its XRD (accompanying drawing 1) spectrogramoThe position display of left and right goes out strong graphite oxide (001)
Diffraction maximum, SEM Electronic Speculum (accompanying drawing 2) shows that prepared graphite oxide has obvious fold and bending features, and size can reach
Micron level.The above-mentioned graphite oxide powder of 400mg is directly scattered in 200mL deionized waters and in ultrasonic disperse under 300W power
60min, obtains uniform graphene oxide colloidal suspension (concentration is 2mg/mL).
Step 2：By 0.01mol Co (NO3)2·6H2O、0.005mol Mg(NO3)2·6H2O、0.005mol Al
(NO3)3·9H2O metal salts are dissolved in 50mL deionized waters and obtain mixed solution A simultaneously with 400mg citric acids.Then holding
The graphene oxide colloidal suspension in step 1 is poured slowly into mixed solution A under continuous stirring condition, by gained slurries in
Ultrasound 30min in the ultrasonic machine of 300W power, obtains brown color slurries B.
Step 3：By 0.064mol NaOH and 0.02mol Na2CO3It is dissolved in 200mL deionized waters and mixing alkali soluble is made
Liquid C.The brown color slurries B obtained in step 2 and mixed alkali liquor C are filled the four of 100mL deionized waters while being slowly dropped into
In mouth flask, pH=10 ± 0.1 is controlled, time for adding is 30min, then the crystallization 4h in 65 DEG C of water-baths, gained black precipitate
It is washed with deionized to pH=7, freeze-drying obtains multilevel hierarchy Co2Mg1Al1- LDHs nano-chip arrays/Graphene is miscellaneous
Change material.The SEM Electronic Speculum (accompanying drawing 3) of material shows Co2Mg1Al1- LDHs nanometer sheets vertical-growth in the both sides of graphene film,
Three-dimensional " honeycomb " shape array pattern is formed, wherein LDHs nanometers of chip size~35nm, thickness~5nm, graphene film size is still protected
Hold in micron level.
Step 4：By multilevel hierarchy Co in step 32Mg1Al1- LDHs/Graphene hybrid materials are in 500 DEG C of still airs
In (5 DEG C/min of heating rate) roasting 4h obtain multilevel hierarchy O composite metallic oxide catalyst Co2Mg1Al1(O).Catalyst
SEM Electronic Speculum result (accompanying drawing 4) shows that oxide catalyst shows the feature of three-dimensional metal composite oxide nano-chip arrays
(lamellar spacing~10nm), is examined it can be seen that the three-dimensional metal composite oxide nano-chip arrays are by the small of high degree of dispersion
Particle diameter metal oxide particle is rearranged, and is existed to a certain degree on the locus of three-dimensional metal composite oxide nanometer sheet
Staggeredly, so that the reunion between obtained nanometer sheet is prevented, before the above results show that being calcined obtained catalyst inherits
The multilevel hierarchy pattern of body.TEM Electronic Speculum (accompanying drawing 5) further demonstrates that oxide particle of the oxide lamella by numerous small particles
Constitute (~8nm), there are numerous holes, grain size, catalyst shape characteristic and its SEM characterization result one between oxide particle
Cause.
Embodiment 2：
Step 1：Graphite oxide is prepared using chemical oxidization method by raw material of natural flake graphite.By 300mg graphite oxides
Directly it is scattered in 150mL deionized waters and in ultrasonic disperse 45min under 300W power, obtains uniform graphene oxide colloid
Shape suspension (concentration is 2mg/mL).
Step 2：By 0.02mol Ni (NO3)2·6H2O、0.01mol Mg(NO3)2·6H2O and 0.01mol Al
(NO3)3·9H2O metal salts are dissolved in 50mL deionized waters and obtain mixed solution A simultaneously with 450mg citric acids.Then holding
The graphene oxide colloidal suspension in step 1 is poured slowly into mixed solution A under continuous stirring condition, by gained slurries in
Ultrasound 20min in the ultrasonic machine of 300W power, obtains brown color slurries B.
Step 3：By 0.128mol NaOH and 0.04mol Na2CO3It is dissolved in 200mL deionized waters and mixing alkali soluble is made
Liquid C.The brown color slurries B obtained in step 2 and mixed alkali liquor C are filled the four of 100mL deionized waters while being slowly dropped into
In mouth flask, pH=10 ± 0.1 is controlled, time for adding is 45min, then the crystallization 12h in 90 DEG C of water-baths, gained black precipitate
It is washed with deionized to pH=7, freeze-drying obtains multilevel hierarchy Ni2Mg1Al1- LDHs nano-chip arrays/Graphene is miscellaneous
Change material.The SEM Electronic Speculum (accompanying drawing 6) of material shows Ni2Mg1Al1- LDHs nanometer sheets vertical-growth in the both sides of graphene film,
Form three-dimensional " honeycomb " shape array pattern, wherein LDHs nanometers of chip size~20nm, thickness~5nm.
Step 4：By multilevel hierarchy Ni in step 32Mg1Al1- LDHs/Graphene hybrid materials are in 400 DEG C of still airs
In (5 DEG C/min of heating rate) roasting 4h obtain multilevel hierarchy O composite metallic oxide catalyst Ni2Mg1Al1(O).Embodiment 3：
Step 1：Graphite oxide is prepared using chemical oxidization method by raw material of natural flake graphite.By 160mg graphite oxides
Directly it is scattered in 80mL deionized waters and in ultrasonic disperse 30min under 300W power, obtains uniform graphene oxide colloid
Shape suspension (concentration is 2mg/mL).
Step 2：By 0.010mol Ni (NO3)2·6H2O、0.002mol Mn(CH3OO)2·4H2O and 0.004mol Fe
(NO3)3·9H2O metal salts are dissolved in 16mL deionized waters and obtain mixed solution A simultaneously with 80mg citric acids.Then continuing
The graphene oxide colloidal suspension in step 1 is poured slowly into mixed solution A under stirring condition, by gained slurries in
Ultrasound 10min in the ultrasonic machine of 300W power, obtains brown color slurries B.
Step 3：By 0.0512mol NaOH and 0.016mol Na2CO3It is dissolved in 200mL deionized waters and mixed base is made
Solution C.The brown color slurries B obtained in step 2 and mixed alkali liquor C are filled into 100mL deionized waters while being slowly dropped into
In four-hole boiling flask, pH=10 ± 0.1 is controlled, time for adding is 60min, then the crystallization 24h in 60 DEG C of water-baths, gained black sinks
Shallow lake is washed with deionized to pH=7, and freeze-drying obtains multilevel hierarchy Ni2.5Mn0.5Fe1- LDHs nano-chip arrays/
Graphene hybrid materials.The SEM Electronic Speculum (accompanying drawing 7) of material shows Ni2.5Mn0.5Fe1- LDHs nanometer sheet vertical-growths are in stone
The both sides of black alkene piece, form three-dimensional " honeycomb " shape array pattern, wherein LDHs nanometers of chip size~120nm, thickness~5nm.
Step 4：By multilevel hierarchy Ni in step 32.5Mn0.5Fe1- LDHs/Graphene hybrid materials are static empty in 600 DEG C
(5 DEG C/min of heating rate) is calcined 4h and obtains multilevel hierarchy O composite metallic oxide catalyst Ni in gas2.5Mn0.5Fe1(O)。
Embodiment 4：
Step 1：Graphite oxide is prepared using chemical oxidization method by raw material of natural flake graphite.By 400mg graphite oxides
Directly it is scattered in 200mL deionized waters and in ultrasonic disperse 60min under 300W power, obtains uniform graphene oxide colloid
Shape suspension (concentration is 2mg/mL).
Step 2：By 0.03mol Co (NO3)2·6H2O and 0.01mol Al (NO3)3·9H2O metal salts and 400mg lemons
Acid is dissolved in 50mL deionized waters and obtains mixed solution A simultaneously.Then by the oxidation stone in step 1 under lasting stirring condition
Black alkene colloidal suspension is poured slowly into mixed solution A, by gained slurries in the ultrasonic machine of 300W power ultrasound 30min,
Obtain brown color slurries B.
Step 3：By 0.128mol NaOH and 0.04mol Na2CO3It is dissolved in 200mL deionized waters and mixing alkali soluble is made
Liquid C.The brown color slurries B obtained in step 2 and mixed alkali liquor C are filled the four of 100mL deionized waters while being slowly dropped into
In mouth flask, pH=10 ± 0.1 is controlled, time for adding is 40min, then the crystallization 12h in 65 DEG C of water-baths, gained black precipitate
It is washed with deionized to pH=7, freeze-drying obtains multilevel hierarchy Co3Al1- LDHs nano-chip arrays/Graphene hydridization materials
Material.
Step 4：By multilevel hierarchy Co in step 33Al1- LDHs/Graphene hybrid materials are in 600 DEG C of still airs
(5 DEG C/min of heating rate) roasting 4h obtains multilevel hierarchy O composite metallic oxide catalyst Co3Al1(O)。
Embodiment 5：
Step 1：Graphite oxide is prepared using chemical oxidization method by raw material of natural flake graphite.By 300mg graphite oxides
Directly it is scattered in 150mL deionized waters and in ultrasonic disperse 45min under 300W power, obtains uniform graphene oxide colloid
Shape suspension (concentration is 2mg/mL).
Step 2：By 0.03mol Ni (NO3)2·6H2O and 0.01mol Fe (NO3)3·9H2O metal salts and 450mg lemons
Acid is dissolved in 50mL deionized waters and obtains mixed solution A simultaneously.Then by the oxidation stone in step 1 under lasting stirring condition
Black alkene colloidal suspension is poured slowly into mixed solution A, by gained slurries in the ultrasonic machine of 300W power ultrasound 30min,
Obtain brown color slurries B.
Step 3：By 0.128mol NaOH and 0.04mol Na2CO3It is dissolved in 200mL deionized waters and mixing alkali soluble is made
Liquid C.The brown color slurries B obtained in step 2 and mixed alkali liquor C are filled the four of 100mL deionized waters while being slowly dropped into
In mouth flask, pH=10 ± 0.1 is controlled, time for adding is 60min, then the crystallization 6h in 80 DEG C of water-baths, gained black precipitate
It is washed with deionized to pH=7, freeze-drying obtains multilevel hierarchy Ni3Fe1- LDHs nano-chip arrays/Graphene hydridization materials
Material.
Step 4：By multilevel hierarchy Ni in step 33Fe1- LDHs/Graphene hybrid materials are in 400 DEG C of still airs
(5 DEG C/min of heating rate) roasting 4h obtains multilevel hierarchy O composite metallic oxide catalyst Ni3Fe1(O)。
Described above is the preferred embodiment of the present invention, it is noted that for those skilled in the art
For, under the premise without departing from the principles of the invention, some improvement can also be made, these improvement also should be regarded as the guarantor of the present invention
Protect scope.
Claims (7)
1. a kind of graphene is oriented to multilevel hierarchy composite oxide catalysts, it is characterised in that：Multilevel-structure hydrotalcite LDHs receives
In rice chip arrays/graphene hybrid material, graphene quality is situated between for the diameter of 8%~25%, the LDHs nanometer sheets of LDHs mass
In 20~120nm, thickness~5nm, pattern is that LDHs nanometer sheets are interlaced, and vertical-growth is in graphene basal plane both sides, shape
Into three-dimensional multistage structure class nano-chip arrays pattern；The hybrid material is calcined, the template direction effect based on graphene makes
The composite oxides that LDHs nano-chip arrays are formed in roasting have remained in that three-dimensional manometer chip arrays pattern, its combined oxidation
The thickness of thing nanometer sheet is 10~12nm, is assembled by 8~10nm of oxide particle of small particle and had the hole of prosperity
Structure, obtains multilevel hierarchy composite oxide catalysts.
2. a kind of preparation method of the multilevel hierarchy composite oxide catalysts of the graphene template direction described in claim 1,
It is characterised in that it includes following steps：
(1) graphite oxide is prepared using chemical oxidization method by raw material of 325 mesh natural flake graphites, drying mode is dry using freezing
Dry condition, prior to -60 DEG C at freeze 1h, under vacuum condition dry 12h after obtain fluffy graphite oxide, by gained oxygen
Graphite is scattered in deionized water, and uniform graphene oxide colloidal suspension is obtained after ultrasonic disperse；
(2) metal salt and citric acid are dissolved in deionized water simultaneously and obtain mixed solution A, then under lasting stirring condition
Graphene oxide colloidal suspension in step 1 is poured slowly into mixed solution A, gained slurries are ultrasonic while stirring,
Obtain brown color slurries B；
(3) by NaOH, Na2CO3Obtained mixed ammonium/alkali solutions C in deionized water is dissolved in simultaneously, it is pale brown by what is obtained in step (2)
Mill base liquid B and mixed ammonium/alkali solutions C is slowly dropped into the four-hole boiling flask for filling 100mL deionized waters simultaneously, and control pH=10 ±
0.1, then in crystallization under water bath condition, gained black precipitate is washed with deionized to pH=7, and multistage is obtained after freeze-drying
Structure LDHs nano-chip arrays/graphene hybrid material；
(4) corresponding multilevel hierarchy composite metal oxide catalyst will be obtained after the hybrid material in step (3) moderately roasting
Agent.
3. preparation method according to claim 2, it is characterised in that：Graphite oxide and deionized water described in step (1)
Mass ratio be 2:1, obtained graphene oxide colloidal suspension concentration is 2mg/mL, and ultrasonic power is 300W, when ultrasonic
Between control be 0.5h~1h.
4. preparation method according to claim 2, it is characterised in that：Metal salt described in step (2) include divalence and
The metal salt of trivalent, its existence form is the divalence gold in nitrate or one kind or its mixed form in acetate, metal salt
Belong to ion M2+For Co2+、Ni2+、Mg2+、Mn2+One or both of combination, trivalent metal ion M3+For Al3+、Fe3+In one
Kind, M2+And M3+Molar ratio be fixed as [M2+]/[M3+]=3：1.
5. preparation method according to claim 4, it is characterised in that：The mass ratio of citric acid and graphite oxide used is
0.5:1~1.5:1, per the total ionizable metal salt [M of 100mg citric acids 0.005~0.02mol of correspondence2++M3+], graphene oxide glue
The volume ratio control of liquid suspension and mixed solution A is 3:1~5:1, ultrasonic power is 300W, and ultrasonic time control is 10min
~30min.
6. preparation method according to claim 2, it is characterised in that：In step (3) in the mixed base of every 100mL volumes,
[NaOH]/[M2++M3+] molar ratio be 1.6：1, [Na2CO3]/[M3+] molar ratio be 2：1, time for adding is maintained at 30~
Between 60min, crystallization temperature selection is 60~90 DEG C, and the time is 4~24h, the freeze-drying of the same step of drying condition (1)
Journey, obtains M2+ 3M3+ 1- LDHs nano-chip arrays/graphene hybrid material.
7. preparation method according to claim 2, it is characterised in that：Roasting condition selection described in step (4) is quiet
400~600 DEG C in state air, 5 DEG C/min of heating rate, the retention time is 4h, obtains multilevel hierarchy M2+ 3M3+ 1(O) composition metal
Oxide.
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