CN105826574B - Nitrogen-doped graphene/difunctional VPO catalysts of ferro-cobalt houghite and its preparation method and application - Google Patents
Nitrogen-doped graphene/difunctional VPO catalysts of ferro-cobalt houghite and its preparation method and application Download PDFInfo
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- H—ELECTRICITY
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- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/9016—Oxides, hydroxides or oxygenated metallic salts
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/24—Nitrogen compounds
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- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
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- H01M4/00—Electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/9091—Unsupported catalytic particles; loose particulate catalytic materials, e.g. in fluidised state
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Abstract
The invention discloses difunctional VPO catalysts of base metal of a kind of nitrogen-doped graphene/ferro-cobalt houghite and its preparation method and application.The catalyst is using bimetallic oxide as precursor, utilize the memory effect of houghite, graphene oxide and ferro-cobalt houghite are assembled, azotized carbon nano piece is doped in compound again under reducing condition and obtains nitrogen-doped graphene/ferro-cobalt houghite compound.VPO catalysts of the present invention are in the basic conditions, there is higher catalytic activity, good stability and excellent methanol tolerance to oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) simultaneously, and raw materials used cost is low, preparation method is simple, it is easily operated, it is easy to mass produce.
Description
Technical field：
The invention belongs to novel energy resource material technology and electrochemical catalysis field, and in particular to nitrogen-doped graphene/ferro-cobalt
The difunctional VPO catalysts of houghite；Further relate to the preparation method of the catalyst and its reacted in electrolyzed alkaline water Oxygen anodic evolution
With the electro-catalysis application in fuel battery negative pole oxygen reduction reaction.
Background technology：
As the mankind are continuously increased to cleaning and sustainable energy demand, great effort has been put into height by scientists
In terms of the research and development of effect, low cost and environmentally friendly energy conversion and stocking system.Wherein oxygen reduction reaction (ORR) is
The cathode reaction of generally existing in fuel cell and metal-air battery, oxygen evolution reaction (OER) then solar energy fuel synthesis and
Played an important role in water-splitting energy storage system.Therefore, catalyst particularly VPO catalysts have been to restrict new energy hair
The main bottleneck of exhibition.In view of the activity and stability of catalyst, the catalyst for ORR reactions mainly has Pt and its alloy,
And the catalyst for being used for OER mainly has IrO2Or RuO2, but these noble metals are very rare in nature, make current power supply
Apparatus cost is too high.Therefore, research and development non-precious metal catalyst becomes hot subject of concern in the field.
Houghite (writing a Chinese character in simplified form LDH) is a kind of two-dimensional nano anionic clay, and it forms formula and is represented by [M1-x 2+Mx 3+
(OH)2]x+(An-)x/n·mH2O, it is made up of positively charged hydroxide laminate and electric charge balances each other therewith interlayer anion.
Its preparation method is more, frequently with coprecipitation, the ion-exchange either calcining restoring method based on itself memory effect.By
In adjustable chemical composition, different electroactive metals such as Fe, Ni, Co, Mn may participate in double-metal hydroxide octahedron
The structure of houghite layer, make LDH materials energy conversion and field of storage present good application prospect [X.Long,
Z.Wang,S.Xiao,Y.An and S.Yang.Transition metal based layered double
hydroxides tailored for energy conversion and storage.Materials Today(2015),
http://dx.doi.org/10.1016/j.mattod.2015.10.006].However, in practical application, LDH catalyst materials
The shortcomings of poorly conductive, easily aggregation and stability difference also be present.In order to overcome LDH disadvantage mentioned above, researcher is generally by some
The material such as carbon material such as graphene (GR) and CNT (CNT) is intercalated in LDH interlayers, first can improve the conduction of composite
Property, second prevent LDH from assembling, improve its stability.GR is a kind of sp2Hydbridized carbon atoms composition has a carbon atom thickness
Two-dimensional material, have the specific surface area (~2600m of superelevation2/ g) and excellent electric conductivity (~106S/cm), can greatly improve
Charge transfer and mass-transfer efficiency in electrocatalytic reaction.And negatively charged graphene oxide (GO) and positively charged LDH
The other static buildup of the face-to-face molecular level of nanometer sheet, LDH transition metal-catalyzed center and conductive sp can be made2Hydbridized carbon atoms
Be in close contact, greatly shorten electrolyte diffusion length [X.Long, et al.Angew.Chem.126 (2014) 7714-
7718.].Although the problems such as LDH material conductivities difference and aggregation can be solved by assembling LDH and GR by electrostatic attraction, GR exists
The competition with other anion is usually present in compound process, as present in the intrinsic anion of LDH interlayers and system
Other anion, cause GR and LDH combined efficiencies bad, if single increase GR dosages, not only fail to strengthen its own and other
The competitiveness of anion, while the GR of surplus is coated on LDH surfaces, cause the masking of avtive spot, so as to drop significantly
Its low catalytic activity.Therefore, the actual combined efficiency for further improving composite is still the efficient elctro-catalyst of exploitation
Significant challenge.
Graphite type carbon nitride (g-C3N4) graphite of nitrogen substitution is commonly called as, there is the two-dimensional slice structure similar to graphene, should
Lamella is formed by van der Waals interaction stacked in multi-layers, has higher nitrogen content, unique heat endurance and appropriate machine
Tool intensity, it is made up of the most abundant carbon of reserves on the earth and nitrogen.Lyth etc. has found g-C at first3N4In acid medium
ORR catalytic activity is higher than carbon black, illustrates that it has certain oxygen reducing ability, [S.M.Lyth, Y.Nabae, S.Moriya,
et.al.Carbon nitride as a nonprecious catalyst for electrochemical oxygen
reduction.The journal of physical chemistry C(2009),http://dx.doi.doi/pdf/
10.1021/jp907928j] but g-C3N4Itself larger energy gap (~2.6eV), the contact resistance of piece interlayer and compared with
Low specific surface area make it that its electric conductivity is excessively poor, equivalent to semiconductor, therefore strongly limit its electron transfer rate
With electrochemical catalysis performance [Y.Zhao, J.Wang and L.T.Qu.Graphitic carbon nitride/graphene
hybrids as new active materials for energy conversion and storage.Chemistry
of nanomaterials for energy,biology and more(2015),http://dx.doi.org/10.1002/
cnma.201500060].And graphene be frequently utilized for semiconducting electrical conductivity can improvement, and graphene have to carbonitride it is similar
2D plane layer structures, usually by both combine so as to prepare nitrogen-doped graphene, nitrogen causes graphene as foreign atom
Possesses more novel application value in association areas such as material preparation, catalysis and energy storage.But g-C3N4Be still limited by its compared with
Small specific surface area, so as to be difficult to estimated electrochemistry and catalytic performance.
In order to prepare the elctro-catalyst with high combined efficiency, the ferro-cobalt houghite after calcining is added portionwise the present invention
Into GO aqueous dispersions, GO/LDH is obtained after being well mixed under certain condition, then adulterates g-C under the reducing conditions3N4Nanometer
Sheet nitrogen-doped graphene/ferro-cobalt houghite (NG/LDH) nanocatalyst is made in piece.NG/ is prepared using the method at present
LDH efficient composite catalysts and the catalyst are used for electrolyzed alkaline water anode OER and fuel battery negative pole ORR research also
Have no report.
What the present invention was utilized is LDH memory effect, and its calcined product bimetallic oxide (LDO) is added portionwise into the moon
Restored in the single GO aqueous dispersions of ionic species, then carry out N doping under the reducing conditions, so as to be prepared for sheet NG/
LDH catalyst, the preparation method avoid recombination process GO and other anion competition, have obtained the GO/LDH of high efficiency composition
Catalyst, the C of state will be peeled off3N4The hydro-thermal in the case where there is hydrazine hydrate existence condition is compound with GO/LDH for nanometer sheet, introduces the same of N atoms
When avoid semiconductor C3N4A large amount of participations, obtained the NG/LDH catalyst with laminated structure, not only increased catalyst
Electric conductivity, it is thus also avoided that LDH itself aggregation, and realize the N doping of real meaning, gained VPO catalysts effectively drop
Low OER and ORR overpotential, shows its ORR mistake by rotating disk electrode (r.d.e) (RDE) and rotating ring disk electrode (r.r.d.e) (RRDE)
Journey majority is 4 electronic catalytic mechanism, is ideal ORR courses of reaction.Elctro-catalyst obtained by this method gives full play to
The synergy of LDH, GR and hetero atom N in terms of electro-catalysis, to exploitation novel electrochemical catalyst and energy conversion and storage
Device has important theoretical and practical significance.
The content of the invention：
In view of the shortcomings of the prior art and the demand of this area research and application, an object of the present invention are to provide one
Kind nitrogen-doped graphene/difunctional VPO catalysts of ferro-cobalt houghite；That is LDO is first high by ferro-cobalt houghite to prepare precursor
Temperature is sintered into ferro-cobalt bimetallic oxide, is recovered using the memory effect of houghite in the aqueous dispersions of graphene oxide,
Graphene oxide is assembled on ferro-cobalt houghite piece, graphene oxide/ferro-cobalt houghite compound is formed, then in water
The doping that azotized carbon nano piece is carried out under hydrazine existence condition is closed, nitrogen-doped graphene/ferro-cobalt houghite flake nano is formed and answers
Close catalyst.
The second object of the present invention is to provide a kind of system of nitrogen-doped graphene/difunctional VPO catalysts of ferro-cobalt houghite
Preparation Method, specifically include following steps：
(a) preparation of CoFe-LDO hybrids
Cobalt chloride hexahydrate and ferric chloride hexahydrate are dissolved in ultra-pure water by certain mol proportion, make metal ion always dense
Spend is completely dissolved it for 0.215mol/L, stirring, then at the uniform velocity instills 1.5mol/L NaOH, until pH=8, this is mixed
Liquid is moved into reactor, and 24h is reacted in 130 DEG C, after reaction solution centrifuges, is washed three times with deionized water and ethanol respectively,
For drying and grinding after the lower 500 DEG C of calcinings 5h of air atmosphere, products therefrom is CoFe-LDO hybrids；
(b) preparation of GO/LDH compounds
A certain amount of GO is scattered in ultra-pure water, ultrasonic disperse 4 hours, 5000rpm centrifugations 10min removes unstripped
GO, it is 1.0~6.0mg/mL to make its ultimate density, pipettes the 50mL solution, 50mg is slowly added to by step (a) under stirring condition
Middle gained CoFe-LDO hybrids, and 12h is stirred at room temperature, then 3000rpm centrifuges 10min, and gained precipitation is GO/
LDH compounds；
(c) preparation of NG/LDH VPO catalysts
0.5g graphite phase carbon nitrides are weighed, are designated as C3N4, it is dissolved in 14mL concentrated sulfuric acid solutions, after being stirred at room temperature two hours
Add 50mL deionized waters to dilute, mixed liquor is washed till neutrality after ultrasonic 2h, obtains 0.3~0.7mg/mL C3N4Nanometer sheet moisture
Dispersion liquid, gained GO/LDH compounds in a certain amount of step (b) are added portionwise in the 80mL solution under ultrasound condition, are then stirring
2mL hydrazine hydrates are added under the conditions of mixing, mixed liquor is moved in reactor after stirring, 20h, institute are reacted under the conditions of 180 DEG C
Obtain and washed three times with deionized water and ethanol after solid sample centrifuges, difunctional VPO catalysts NG/LDH is obtained after drying.
The mol ratio of cobalt chloride hexahydrate and ferric chloride hexahydrate is 3 wherein described in step (a):1, institute in step (c)
Structure, average grain diameter are 125~150nm to the VPO catalysts obtained in the form of sheets, and specific surface area is in 134.09~168.63m2/g。
The three of the object of the invention are to provide a kind of nitrogen-doped graphene/difunctional VPO catalysts of ferro-cobalt houghite in alkalescence
Application in anode of electrolytic water OER and fuel battery negative pole ORR.
The present invention utilizes LDH memory effect, first assembles GO and LDH using calcining restoring method, is then being hydrated
Pass through C in hydrazine3N4Doping obtained the NG/LDH catalyst with laminated structure；Not only increase catalyst electric conductivity and
Combined efficiency, and gained VPO catalysts effectively reduce OER and ORR overpotential, the results showed that its ORR process is mainly
4 electronic catalytic mechanism, it is ideal ORR courses of reaction.
Compared with prior art, the present invention has following major advantage and beneficial effect：
1) difunctional VPO catalysts of the present invention are base metal composite, raw materials used to be easy to buy and make
Standby, aboundresources and price is relatively low, it is low that it prepares cost on a large scale；
2) methanol tolerance that difunctional VPO catalysts of the present invention have had, in 0.1mol/L KOH electrolyte
1mol/L methanol is added, the catalytic activity of catalyst does not almost decay；
3) difunctional VPO catalysts of the present invention are a kind of novel three-dimensional composite, have preferable OER and ORR
Activity, there is significant advantage compared with the one-side ORR activity of base metal/non-metallic catalyst of current research report；
4) compared with commercialization 20wt% Pt/C catalyst, stability obtains difunctional VPO catalysts of the present invention
Significantly improve, can keep good catalytic activity in fuel cell long-term use；
5) the OER activity of difunctional VPO catalysts of the present invention, the Heteroatom doping reported better than current research
Carbon material/non-precious metal catalyst；
6) difunctional VPO catalysts preparation method of the present invention is simple, easily operated, is easy to mass produce.
Brief description of the drawings：
Fig. 1 is the gained NG/LDH compound scanning electron microscope (SEM) photographs of embodiment 2.
Fig. 2 be the gained NG/LDH compounds of embodiment 2, the gained LDH of comparative example 1, the gained N/LDH compounds of comparative example 2 and
The gained G/LDH compounds of comparative example 3 modify the linear volt-ampere curve figures of OER of Ni foam electrodes.
Fig. 3 is that the gained NG/LDH compounds of embodiment 2 modify Ni foam electrodes in 15mA/cm2Under P-t curve maps.
Fig. 4 be the gained NG/LDH compounds of embodiment 2, the gained LDH of comparative example 1, the gained N/LDH compounds of comparative example 2 and
The gained G/LDH compounds of comparative example 3 modify the RDE linear volt-ampere curve figures of ORR.
Fig. 5 is the ORR kinetic curves that the gained NG/LDH compounds of embodiment 2 modify RDE.
Fig. 6 is the ORR kinetic curves that the gained NG/LDH compounds of embodiment 2 modify RRDE.
Fig. 7 is the linear volt-ampere curve figures of ORR that the gained NG/LDH compounds of embodiment 2 modify RDE under 1600rpm, passed through
The linear volt-ampere curve figures of ORR and the linear volt-ampere curve figures of ORR added after methanol after 5000 cyclic voltammetry scans.
Embodiment：
To further understand the present invention, the invention will be further described with reference to the accompanying drawings and examples, but not with
Any mode limits the present invention.
Embodiment 1：
(a) preparation of CoFe-LDO hybrids
Cobalt chloride hexahydrate and ferric chloride hexahydrate are dissolved in ultra-pure water by certain mol proportion, make metal ion always dense
Spend is completely dissolved it for 0.215mol/L, stirring, then at the uniform velocity instills 1.5mol/L NaOH, until pH=8, this is mixed
Liquid is moved into reactor, and 24h is reacted in 130 DEG C, after reaction solution centrifuges, is washed three times with deionized water and ethanol respectively,
For drying and grinding after the lower 500 DEG C of calcinings 5h of air atmosphere, products therefrom is CoFe-LDO hybrids；
(b) preparation of GO/LDH compounds
A certain amount of GO is scattered in ultra-pure water, ultrasonic disperse 4 hours, 5000rpm centrifugations 10min removes unstripped
GO, it is 1.0mg/mL to make its ultimate density, pipettes the 50mL solution, and 50mg is slowly added under stirring condition by institute in step (a)
CoFe-LDO hybrids are obtained, and stir 12h at room temperature, then 3000rpm centrifuges 10min, and gained precipitation is that GO/LDH is answered
Compound；
(c) preparation of NG/LDH VPO catalysts
Weigh 0.5g C3N4It is dissolved in 14mL concentrated sulfuric acid solutions, 50mL deionized waters is added after being stirred at room temperature two hours
Dilute, mixed liquor is washed till neutrality after ultrasonic 2h, obtains 0.5mg/mL C3N4Nanometer sheet aqueous dispersions, in 80mL under ultrasound condition
Gained GO/LDH compounds in 100mg steps (b) are added portionwise in the solution, then add 2mL hydrazine hydrates under agitation,
Mixed liquor is moved in reactor after stirring, 20h is reacted under the conditions of 180 DEG C, gained solid sample is used after centrifuging
Deionized water and ethanol washing three times, obtain difunctional VPO catalysts NG/LDH, its average grain diameter is 142nm, compares surface after drying
Product is 151.52m2/g。
Embodiment 2：
(a) preparation of CoFe-LDO hybrids
Prepared according to the method and condition of step (a) in embodiment 1；
(b) preparation of GO/LDH compounds
A certain amount of GO is scattered in ultra-pure water, ultrasonic disperse 4 hours, 5000rpm centrifugations 10min removes unstripped
GO, it is 3.0mg/mL to make its ultimate density, pipettes the 50mL solution, and 50mg is slowly added under stirring condition by institute in step (a)
CoFe-LDO hybrids are obtained, and stir 12h at room temperature, then 3000rpm centrifuges 10min, and gained precipitation is that GO/LDH is answered
Compound；
(c) preparation of NG/LDH VPO catalysts
Prepared according to the method and condition of step (c) in embodiment 1, its average grain diameter is 136nm, and specific surface area is
142.38m2/g。
Embodiment 3：
(a) preparation of CoFe-LDO hybrids
Prepared according to the method and condition of step (a) in embodiment 1；
(b) preparation of GO/LDH compounds
A certain amount of GO is scattered in ultra-pure water, ultrasonic disperse 4 hours, 5000rpm centrifugations 10min removes unstripped
GO, it is 6.0mg/mL to make its ultimate density, pipettes the 50mL solution, and 50mg is slowly added under stirring condition by institute in step (a)
CoFe-LDO hybrids are obtained, and stir 12h at room temperature, then 3000rpm centrifuges 10min, and gained precipitation is that GO/LDH is answered
Compound；
(c) preparation of NG/LDH VPO catalysts
Prepared according to the method and condition of step (c) in embodiment 1, its average grain diameter is 125nm, and specific surface area is
168.63m2/g。
Embodiment 4：
(a) preparation of CoFe-LDO hybrids
Prepared according to the method and condition of step (a) in embodiment 1；
(b) preparation of GO/LDH compounds
Prepared according to the method and condition of step (b) in embodiment 2；
(c) preparation of NG/LDH VPO catalysts
Weigh 0.5g C3N4It is dissolved in 14mL concentrated sulfuric acid solutions, 50mL deionized waters is added after being stirred at room temperature two hours
Dilute, mixed liquor is washed till neutrality after ultrasonic 2h, obtains 0.5mg/mL C3N4Nanometer sheet aqueous dispersions, in 80mL under ultrasound condition
Gained GO/LDH compounds in 100mg steps (b) are added portionwise in the solution, then add 2mL hydrazine hydrates under agitation,
Mixed liquor is moved in reactor after stirring, 20h is reacted under the conditions of 180 DEG C, gained solid sample is used after centrifuging
Deionized water and ethanol washing three times, obtain difunctional VPO catalysts NG/LDH, its average grain diameter is 150nm, compares surface after drying
Product is 134.09m2/g。
Embodiment 5：
(a) preparation of CoFe-LDO hybrids
Prepared according to the method and condition of step (a) in embodiment 1；
(b) preparation of GO/LDH compounds
Prepared according to the method and condition of step (b) in embodiment 2；
(c) preparation of NG/LDH VPO catalysts
Weigh 0.5g C3N4It is dissolved in 14mL concentrated sulfuric acid solutions, 50mL deionized waters is added after being stirred at room temperature two hours
Dilute, mixed liquor is washed till neutrality after ultrasonic 2h, obtains 0.7mg/mL C3N4Nanometer sheet aqueous dispersions, in 80mL under ultrasound condition
Gained GO/LDH compounds in 100mg steps (b) are added portionwise in the solution, then add 2mL hydrazine hydrates under agitation,
Mixed liquor is moved in reactor after stirring, 20h is reacted under the conditions of 180 DEG C, gained solid sample is used after centrifuging
Deionized water and ethanol washing three times, obtain difunctional VPO catalysts NG/LDH, its average grain diameter is 138nm, compares surface after drying
Product is 140.16m2/g。
Comparative example 1：
(a) preparation of CoFe-LDH hybrids
Cobalt chloride hexahydrate and ferric chloride hexahydrate are pressed 3：1 mol ratio is dissolved in ultra-pure water, makes metal ion total
Concentration is 0.215mol/L, and stirring is completely dissolved it, then at the uniform velocity instills 1.5mol/L NaOH, until pH=8, this is mixed
Close liquid to move into reactor, 24h is reacted in 130 DEG C, after reaction solution centrifuges, washs three with deionized water and ethanol respectively
It is secondary, as CoFe-LDH hybrids；
Comparative example 2：
(a) preparation of CoFe-LDO hybrids
Prepared according to the method and condition of step (a) in embodiment 1；
(b) the LDH compounds N/LDH of carbon doping preparation is nitrogenized
Weigh the 0.5g C3N4It is dissolved in 14mL concentrated sulfuric acid solutions, 50mL deionized waters is added after being stirred at room temperature two hours
Dilution, then ultrasonic 2h, then mixed liquor is washed till into neutrality, obtains 0.5mg/mL C3N4Nanometer sheet aqueous dispersions, in 80mL, this is molten
Gained CoFe-LDO hybrids in the step (a) of 100mg embodiments 1 are added portionwise in liquid, then add 2mL water under agitation
Hydrazine is closed, moves to mixed liquor in reactor after stirring, 20h is reacted under the conditions of 180 DEG C, gained solid sample centrifuges
Washed three times with deionized water and ethanol afterwards, difunctional VPO catalysts N/LDH is obtained after drying.
Comparative example 3：
(a) preparation of CoFe-LDO hybrids
Prepared according to the method and condition of step (a) in embodiment 1；
(b) preparation of GO/LDH compounds
Prepared according to the method and condition of step (b) in embodiment 2；
(c) preparation of G/LDH VPO catalysts
GO/LDH compounds obtained by step (b) in 100mg embodiments 2 are dissolved in 80mL ultra-pure waters, then in stirring bar
2mL hydrazine hydrates are added under part, mixed liquor is moved in reactor after stirring, 20h is reacted under the conditions of 180 DEG C, gained is solid
Body sample is washed three times after centrifuging with deionized water and ethanol, and difunctional VPO catalysts G/LDH is obtained after drying.
Fig. 1 is the scanning electron microscope (SEM) photograph of the gained NG/LDH compounds of embodiment 2, as shown in the figure hexagonal piece pattern intrinsic LDH
Occur irregular, this is to be probably caused by hetero atom N or special hybridization conditions, and its pattern present it is compound
Structure, the graphene platelet of silk shape is mingled between irregular nanometer sheet, this demonstrate that graphene and houghite is effective
It is compound, at the same also cause the original two-dimensional structure bodies of LDH by with graphene sheet layer is compound presents hierarchy, have three
Dimension space structure, so the specific surface area of composite is greatly improved.
Embodiment 6：
The catalyst of 10mg embodiments 2, comparative example 1, comparative example 2 and the gained of comparative example 3 is scattered in 400 μ L ethanol respectively
And 20 in μ L polytetrafluoroethylsolution solutions, after ultrasound mixes solution, 15 μ L slurry drops are taken to be applied to 1 × 1cm2On foam nickel electrode,
The tabletting after it is completely dried, its OER electrocatalysis characteristic is determined on CHI660D electrochemical workstations, and with saturation Hg/
Hg2Cl2/ KCl electrodes are reference electrode, and Pt electrodes are that it is 10mV/s, electrolyte N to sweep speed to electrode2The 0.1M KOH of saturation.
Embodiment 7：
The catalyst obtained by 10mg embodiments 2, comparative example 1, comparative example 2 and comparative example is scattered in 400 μ L ethanol respectively
And 15 in μ L Nafion solutions, after ultrasound mixes solution, take 2 μ L slurry drops be applied to rotating ring disk electrode (r.r.d.e) (RRDE,
0.1256cm2) on, determine its ORR electrocatalysis characteristic on CHI660D electrochemical workstations after it is completely dried, and with
Saturation Hg/Hg2Cl2/ KCl electrodes are reference electrode, and Pt electrodes are that it is 10mV/s, electrolyte O to sweep speed to electrode2Saturation
0.1M KOH, test result can calculate electronics after Koutecky-Levich formula manipulation, by the K-L slopes of curve (B) and turn
Move number (n).
J-1=Jk -1+(Bω1/2)-1
B=0.62n F C0D0 2/3v1/6
Wherein F=96485C/mol, C0=1.2 × 10-3Mol/L, D0=1.9 × 10-5cm2/ s, v=0.01cm2/s。
RRDE test results can obtain electron transfer number (n) and H by following formula manipulation2O2Content：
N=4Id·(Id+Ir/N)
%H2O2=200Id/N·(Id+Ir/ N),
Wherein N=0.43.
Fig. 2 is the gained NG/LDH of embodiment 2, the gained LDH of comparative example 1, the gained N/LDH of comparative example 2 and the gained G/ of comparative example 3
LDH compounds modify the linear volt-ampere curve figures of OER of Ni foam electrodes.Of the Ni foam electrodes of LDH modifications as shown in the figure
Beginning overpotential is 300mV, and after LDH combined oxidation graphenes, OER starting overpotentials are down to 240mV, then by under reducing condition
After carrying out N doping, NG/LDH starting overpotential is down to 225mV again, and peels off state C for directly doping3N4Catalyst n/
LDH, its OER starting overpotential are 290mV, and higher than GO/LDH, this could not be changed mainly due to electric conductivity bad LDH
It is kind, cause its electro-catalysis ability poor, be embodied in the reduction of OER catalytic activity.Similarly, when current density is 10mA/
cm2When, the overpotential corresponding to LDH, G/LDH, N/LDH and NG/LDH modification RDE is respectively 410,360,290 and 270mV.Knot
Fruit shows hydridization of the LDH by NG, significantly reduces its overpotential, and this is mainly due to after compound nitrogen-doped graphene
LDH composite material conductives ability and electro-catalysis ability are obviously improved.
Fig. 3 is that the gained NG/LDH compounds of embodiment 2 modify Ni foam electrodes in 15mA/cm2Under P-t curve maps.Such as
Shown in figure, by 8h continuous analysis oxygen process, NG/LDH OER current potentials are due to oxygen only there occurs minor variations, the change
Bubble lasting precipitation, constantly impact electrode surface NG/LDH catalyst, so as to cause material it is micro come off caused by, thus may be used
See, NG/LDH catalyst shows good OER catalytic stabilities in alkaline solution, has longer service life.
Fig. 4 is the gained NG/LDH compounds of embodiment 2, the gained LDH of comparative example 1, the gained N/LDH of comparative example 2, comparative example 3
Institute G/LDH must modify the RDE linear volt-ampere curve figures of ORR.As illustrated, passing through N doping after the compound GO of LDH again, ORR's rises
Beginning current potential just moves to 0.80V by 0.74V, and Limited diffusion current density is also by -4.35mA/cm2Increase to -5.15mA/cm2；Compared to
G/LDH, the simple product N/LDH carried out after N doping LDH, equally also shows preferable ORR catalytic performances, it is possible thereby to push away
It is disconnected：The presence of hetero atom N and graphene significantly improves the electronics conduction efficiency and catalytic activity of NG/LDH compounds, table
Now for ORR take-off potentials shuffle and steady-state process in current density significant increase, it is achieved thereby that ORR catalytic performances
Enhancing.
Fig. 5 is the ORR kinetic curves that the gained NG/LDH compounds of embodiment 2 modify RDE.As a result show, ORR catalysis
During electron transfer number mesh be about 3.8, close to without HO2 -4 electronic transfer process of product, so as to illustrate NG/LDH modified electrodes
The ORR processes majority of catalysis is preferable 4 electron reaction mechanism.
Fig. 6 is the ORR kinetic curves that the gained NG/LDH compounds of embodiment 2 modify RRDE.As a result show, the ORR is urged
Electron transfer number mesh is about 3.7 during change, is approached with RDE test results, and the HO of 2 electron reaction courses2 -Product is always
Less than 20% is maintained, it is preferable 4 electron reaction mechanism, i.e. NG/LDH compounds to further illustrate ORR processes majority
With good ORR catalytic activity.
Fig. 7 is that the gained NG/LDH compounds of embodiment 2 modify ORR linear volt-ampere curve figures of the RDE under 1600rpm.Such as
Shown in figure, after 5000 cyclic voltammetry scans, there is shuffling for part in the limiting diffusion current of the volt-ampere curve, and
ORR take-off potentials almost do not change, and for this explanation after long-time loop test, NG/LDH still remains higher ORR
Catalytic activity.Similarly, after (instilling 1mL in about 50mL electrolyte) after instillation 1M methanol in system, the ORR of the volt-ampere curve
Take-off potential occur it is slight shuffle and along with the slight increase of half wave potential, and Limited diffusion current density is not almost sent out
Changing, this explanation is in the system containing methanol, and ORR catalytic reactions fail to be interfered, it was demonstrated that NG/LDH catalyst phases
There is stronger methanol tolerance interference performance with noble metal decorated electrode compared with business.In summary, NG/LDH modified electrodes are in alkali
There is preferable stability under the conditions of property, and compared to noble metal electrode, it shows splendid methanol tolerance, can be used as more
The decorative material of kind fuel battery negative pole.
Claims (4)
1. a kind of nitrogen-doped graphene/difunctional VPO catalysts of ferro-cobalt houghite, it is characterised in that the catalyst is first will
The high-temperature calcination of ferro-cobalt houghite into ferro-cobalt bimetallic oxide, using houghite memory effect graphene oxide water
Recover in dispersion liquid, graphene oxide is assembled on ferro-cobalt houghite piece, form graphene oxide/ferro-cobalt houghite and answer
Compound, the doping of azotized carbon nano piece is then carried out under hydrazine hydrate existence condition, form nitrogen-doped graphene/ferro-cobalt class neatly
Flag shape nano-complex, the ferro-cobalt bimetallic oxide are designated as CoFe-LDO, and ferro-cobalt houghite is designated as LDH, the oxygen
Graphite alkene is designated as GO, and graphene oxide/ferro-cobalt houghite is designated as GO/LDH, nitrogen-doped graphene/ferro-cobalt houghite note
For NG/LDH；
The preparation method of the nitrogen-doped graphene/difunctional VPO catalysts of ferro-cobalt houghite, it is characterised in that including following
Specific steps：
(a) preparation of CoFe-LDO hybrids
Cobalt chloride hexahydrate and ferric chloride hexahydrate are dissolved in ultra-pure water by certain mol proportion, make the metal ion total concentration be
0.215mol/L, stirring are completely dissolved it, then at the uniform velocity instill 1.5mol/L NaOH, until pH=8, the mixed liquor is moved
Enter in reactor, 24h is reacted in 130 DEG C, after reaction solution centrifuges, washed three times, dried with deionized water and ethanol respectively
After the lower 500 DEG C of calcinings 5h of air atmosphere, products therefrom is CoFe-LDO hybrids for grinding；
(b) preparation of GO/LDH compounds
A certain amount of GO is scattered in ultra-pure water, ultrasonic disperse 4 hours, 5000rpm centrifugations 10min removes unstripped GO, makes
Its ultimate density is 1.0~6.0mg/mL, pipettes the 50mL solution, and 50mg is slowly added under stirring condition by institute in step (a)
CoFe-LDO hybrids are obtained, and stir 12h at room temperature, then 3000rpm centrifuges 10min, and gained precipitation is that GO/LDH is answered
Compound；
(c) preparation of NG/LDH VPO catalysts
0.5g graphite phase carbon nitrides are weighed, are designated as C3N4, it is dissolved in 14mL concentrated sulfuric acid solutions, is added after being stirred at room temperature two hours
50mL deionized waters are diluted, and mixed liquor is washed till into neutrality after ultrasonic 2h, obtains 0.3~0.7mg/mL C3N4Nanometer sheet moisture dissipates
Liquid, gained GO/LDH compounds in a certain amount of step (b) are added portionwise in the 80mL solution under ultrasound condition, are then stirring
Under the conditions of add 2mL hydrazine hydrates, mixed liquor is moved in reactor after stirring, 20h, gained are reacted under the conditions of 180 DEG C
Solid sample is washed three times after centrifuging with deionized water and ethanol, and difunctional VPO catalysts NG/LDH is obtained after drying.
2. a kind of nitrogen-doped graphene according to claim 1/difunctional VPO catalysts of ferro-cobalt houghite, its feature exist
In step
(a) mol ratio of cobalt chloride hexahydrate described in and ferric chloride hexahydrate is 3:1.
3. a kind of nitrogen-doped graphene according to claim 1 or 2/difunctional VPO catalysts of ferro-cobalt houghite, it is special
Sign is that the catalyst is in shaggy laminated structure, and average grain diameter is 125~150nm, specific surface area 134.09~
168.63m2/g。
4. a kind of nitrogen-doped graphene according to claim 1 or 2/difunctional VPO catalysts of ferro-cobalt houghite, it is special
Sign is that the catalyst is used for the reaction of electrolyzed alkaline water Oxygen anodic evolution and fuel battery negative pole oxygen reduction reaction.
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| CN111167499B (en) * | 2020-01-21 | 2022-11-22 | 佛山科学技术学院 | NiM-LDH/g-C 3 N 4 Composite photocatalytic material and preparation method thereof |
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| CN114792810B (en) * | 2022-04-08 | 2024-01-30 | 启东高能新能源有限公司 | Preparation method of Fe (Ni) -NCNTs@NiFe-LDH in-situ electrode |
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