Summary of the invention
The present invention adopts simple unique synthetic method, prepares the metal nickel nano sheet and assembly thereof with superthin structure.During as electrode material, super thin metal nickel nano film and assembly thereof show extremely excellent electrocatalysis characteristic.
A first aspect of the present invention relates to a kind of super thin metal nickel nano film, and it is of a size of: thickness 2-5 nanometer, length 100-300 nanometer, width 50-300 nanometer.
A second aspect of the present invention relates to a kind of preparation method of super thin metal nickel nano film, described super thin metal nickel nano film thickness 2-5 nanometer, length 100-300 nanometer, width 50-300 nanometer, and described preparation method comprises:
A. by nickel salt solution and precipitating reagent, the hydro-thermal reaction in closed container generates ultra-thin nickel hydroxide nano sheet, and it is of a size of thickness 5-10 nanometer, length 1.0-5.0 micron, width 0.5-3.0 micron;
B. by the original appearance reduction in alkaline polyol solution of described ultra-thin nickel hydroxide nano sheet.
In above-mentioned preparation method, described hydrothermal reaction condition is heated up and carry out hydro-thermal reaction at autogenous pressures by the aqueous solution comprising soluble nickel salt and hexamethylenetetramine or urea, wherein said original appearance reduction reaction conditions heats up for nickel hydroxide nano sheet being placed in alkaline polyol solution and carrying out alcohothermal reaction at autogenous pressures, wherein said polyalcohol is selected from ethylene glycol, propane diols, BDO, hexylene glycol.Described precipitating reagent is selected from hexamethylenetetramine or urea.
The third aspect, the present invention relates to the electrode material that a kind of surface has super thin metal nickel nano film array, it comprises:
Porous, electrically conductive substrate;
Perpendicular to the super thin metal nickel nano film array of this substrate grown in described porous, electrically conductive substrate;
Wherein said super thin metal nickel nano film is of a size of: thickness 2-5 nanometer, length 100-300 nanometer, width 50-300 nanometer.
Fourth aspect, the present invention relates to the electrode material that a kind of surface has nickel metal nickel nano sheet assembly, it comprises:
Porous, electrically conductive substrate;
Perpendicular to the metal nickel nano sheet assembly of this substrate grown in described porous, electrically conductive substrate, described assembly intersects by metal nickel nano sheet the spherical nickel nano flower array assembled; The diameter of wherein said metal nickel nano sheet assembly is 30-70 nanometer.Preferably, the diameter of described metal nickel nano sheet assembly is 40-60 nanometer, is more preferably 45-55 nanometer, such as 50 ran.
In the present invention, described porous, electrically conductive substrate is nickel foam or foam copper.Wherein, described porous, electrically conductive substrate refers to the conductive substrates with loose structure, and this substrate is metal in material, can be called foam metal.Wherein metal can be selected from any applicable metal, such as, when metal is copper, is then called foam copper, when metal is nickel, is then called nickel foam.About how detailed introduction and the preparation method of foam metal, can see existing patented technology document.Such foam metal be also can be commercially available or can make by oneself according to pertinent literature content.
In a preferred embodiment of the present invention, described super thin metal nickel nano film sheet is with the superficial growth of the form of array perpendicular to this porous, electrically conductive substrate, and be 100nm-300nm with the length of conductive substrates contact surface, the width of described nickel nano film is 50nm-300nm, and the thickness of described nickel nano film is 2nm-5nm.Wherein said array refers to the expansion of single nanometer sheet in two dimension or three-dimensional, and this expansion can be orderly orientating type expansion, also can be unordered non-orientation type expansion.
The assembly diameter assembled by nickel nano film in the present invention is at about 50nm, overall appearance is like spheric granules, surface is long multilevel hierarchy, and characterized by transmission electron microscope and can find out that this assembly is intersected mutually by multi-disc nanometer sheet and form, the present inventor is by its called after " nickel nano flower ".Such super thin metal nickel nano film array and be mutually closely cross-linked to form three-dimensional porous nickel nano flower.Multiple ball shaped nano is spent can also be orderly or to be unorderedly stacked each other, forms more complicated three-dimensional structure.
5th aspect, the present invention relates to the preparation method that a kind of surface as described in third aspect present invention has the electrode material of ultra-thin nickel nano film array, it comprises the following steps:
A. the aqueous solution of soluble nickel salt and hexamethylenetetramine or urea will be comprised, join in reactor, again reactor is put in the porous, electrically conductive substrate of surface after acid treatment, then this reactor airtight, heat up and carry out hydro-thermal reaction at autogenous pressures, with this substrate grown nickel hydroxide nano chip arrays vertical on this porous, electrically conductive substrate surface;
B. the porous, electrically conductive substrate of nickel hydroxide nano chip arrays is had to take out by long for surface, dry after washing;
C. in the second reactor, add the ethylene glycol solution of NaOH, again this reactor is put in the porous, electrically conductive substrate obtained through step b, sealed reactor, heat up and carry out alcohothermal reaction at autogenous pressures, making nickel hydroxide nano sheet original appearance described in each be reduced into ultra-thin nickel nano film array; Washing also, after vacuum drying, obtains the electrode material that described surface has ultra-thin nickel nano film array, and saves backup under the condition of starvation.
In preferred version in the 5th, wherein said soluble nickel salt is selected from nickel nitrate, nickelous sulfate or nickel chloride; In wherein said hydro-thermal reaction, in the described aqueous solution, soluble nickel salinity is 0.1-0.5 mol/L, and hexamethylenetetramine concentration is 0.2-1.0 mol/L, and the condition of described first hydro-thermal reaction is: temperature is 90-120 DEG C, and the reaction time is 8-20 hour; In alcohothermal reaction, the concentration of NaOH in ethylene glycol is 0.3-1.0 mol/L, and the condition of described alcohothermal reaction is: temperature is 140-180 DEG C, and the reaction time is 8-24 hour.
6th aspect, the invention discloses the preparation method that a kind of surface as described in fourth aspect present invention has the electrode material of ultra-thin nickel nano film assembly, it comprises the following steps:
A. the aqueous solution comprising soluble nickel salt and hexamethylenetetramine or urea is joined in reactor, again reactor is put in the porous, electrically conductive substrate of surface after acid treatment, then this reactor airtight, heat up and carry out hydro-thermal reaction at autogenous pressures, with this substrate grown nickel hydroxide nano chip arrays vertical on this porous, electrically conductive substrate surface;
B. the porous, electrically conductive substrate of nickel hydroxide nano chip arrays is had to take out by long for surface, dry after washing;
C. in the second reactor, add the ethylene glycol solution of NaOH and sodium borohydride, again this reactor is put in the porous, electrically conductive substrate obtained through step b, sealed reactor, heat up and carry out alcohothermal reaction at autogenous pressures, make nickel hydroxide nano sheet original appearance described in each be reduced into ultra-thin nickel nano film and form described ultrathin nanometer sheet assembly; Washing also, after vacuum drying, obtains the electrode material that described surface has ultra-thin nickel nano film assembly, and saves backup under the condition of starvation.
In preferred version in the 6th, wherein said soluble nickel salt is selected from nickel nitrate, nickelous sulfate or nickel chloride; In wherein said hydro-thermal reaction, in the described aqueous solution, soluble nickel salinity is 0.1-0.5 mol/L, and hexamethylenetetramine concentration is 0.2-1.0 mol/L, and the condition of described first hydro-thermal reaction is: temperature is 90-120 DEG C, and the reaction time is 8-20 hour; In alcohothermal reaction, the concentration of NaOH in ethylene glycol is 0.3-1.0 mol/L, and the concentration of sodium borohydride in ethylene glycol is 0.1-0.5 mol/L, and the condition of described alcohothermal reaction is: temperature is 140-180 DEG C, and the reaction time is 8-24 hour.
Specifically, in the step a of above-mentioned 5th aspect and the 6th aspect, the first reactor is put into by tilting for porous, electrically conductive substrate, first aqueous solution comprising soluble nickel salt and hexamethylenetetramine is added again in this reactor, then this reactor airtight, heat up and carry out hydro-thermal reaction at autogenous pressures, being prepared in the nickel hydroxide nano chip arrays of this substrate grown vertical on this porous, electrically conductive substrate surface.Preferably, this porous, electrically conductive substrate will in advance through cleaning, to remove dirt on surface and impurity.Such cleaning can be ultrasonic cleaning in concentrated hydrochloric acid, is then transferred in such as deionized water and ethanol equal solvent, ultrasonic cleaning again.In this first aqueous solution, the concentration of various material can adjust as required, and such as, in a kind of preferred embodiment, described soluble nickel salinity is 0.1-0.5 mol/L, and hexamethylenetetramine concentration is 0.2-1.0 mol/L.Certainly, also other concentration range can be used.The condition of described first hydro-thermal reaction also can adjust as required, and such as a kind of optimum condition is: temperature is 90-120 DEG C, and the reaction time is 8-20 hour.Through the first hydro-thermal reaction, what porous, electrically conductive substrate obtained is nickel hydroxide nano chip arrays.Change the concentration of each material or change the condition of the first hydro-thermal reaction, can adjust nickel hydroxide nano chip arrays arranging density on this substrate, growing height etc., these can be tested by limited number of time and specifically grope its growth rhythm.Wherein said soluble nickel salt is selected from nickel nitrate, nickelous sulfate or nickel chloride, or their any hydrate with the crystallization water.After this first hydro-thermal reaction terminates, open after this first reactor is cooled to room temperature.
Specifically, in the step b of above-mentioned 5th aspect and the 6th aspect, take out this porous, electrically conductive substrate, washing is also dry.Do not limit concrete washing and drying mode, such as, washing can be carried out rinsing or ultrasonic cleaning with any suitable solvent such as water, ethanol etc., and drying can adopt the mode of drying in an oven.
Specifically, in the step c of above-mentioned 5th aspect, the second reactor is put into by tilting for the porous, electrically conductive substrate after step b process, the reducing solution comprising NaOH and ethylene glycol is added again in this reactor, seal this reactor, heat up and carry out alcohothermal reaction at autogenous pressures, making nickel hydroxide nano sheet described in each by the nickel nano film of in-situ reducing slabbing structure.In described second aqueous solution, various amount of substance can adjust as required, and such as, in a kind of preferred embodiment, the concentration of NaOH in ethylene glycol is 0.3-1.0 mol/L; The condition of described alcohothermal reaction also can adjust as required, and such as a kind of optimum condition is: temperature is 140-180 DEG C, and the reaction time is 8-24 hour.This porous, electrically conductive substrate is again taken out, washing also vacuum drying after reduction reaction terminates.Will carry out starvation to concrete washing and drying mode, such as, washing can be carried out rinsing or ultrasonic cleaning with the solvent of deoxygenation such as water, ethanol etc., and drying can adopt the mode of drying in vacuum drying oven.
Specifically, in the step c of above-mentioned 6th aspect, also add sodium borohydride to above-mentioned comprising in the reducing solution of NaOH and ethylene glycol, and other condition is constant, can prepare nickel nano flower.The concentration of sodium borohydride also can adjust as required, and such as, in a kind of preferred embodiment, the concentration of sodium borohydride in ethylene glycol is 0.1-0.5 mol/L.After the reaction of this alcohothermal terminates, open after this second reactor is cooled to room temperature.Follow-up washing drying steps is with described in fifth aspect present invention.
7th aspect, the invention still further relates to according to a first aspect of the present invention described super thin metal nickel nano film, electrode material that electrode material that surface described in the third aspect has ultra-thin nickel nano film array or surface described according to a fourth aspect of the present invention have ultra-thin nickel nano film assembly is used as the purposes of the positive electrode of hydrazine hydrate oxidized fuel cell or is used as the purposes of brine electrolysis cathode material for hydrogen evolution.
In the present invention, no matter be that surface has ultra-thin nickel nano film or has nickel nano flower, considerably increase the surface area of material of the present invention undoubtedly, and enhance its electrical contact efficiency.Material of the present invention is very suitable for the cathode material of positive electrode as hydrazine hydrate fuel cell and brine electrolysis evolving hydrogen reaction, and the performance shown all is superior to current commercial best platinum C catalyst.But do not get rid of material of the present invention yet and find to there is other purposes in the future.
Beneficial effect of the present invention is as follows:
1, preparation method of the present invention synthesizes under simple hydrothermal reaction condition, and method is easy, with low cost, reproducible, very friendly to environment; Synthetic method uniqueness set forth in the present invention is ingenious, for synthesis ultrathin nanometer sheet metal provides new approaches.The thickness of synthesized super thin metal nickel nano film is only several nanoscale, has electric conductivity and the quantum effect of superelevation.
2, homogeneous, the ordered arrangement of material structure of the present invention, what is more important its be monoblock type material, directly be connected with the conductive substrates as collector as the nickel nano film of electrode active material and assembly thereof in material, without the need to adding adhesive during making, and novel structure, there is good conduction property; Such structure avoids the problem that the little and interfacial gases product of general powder body material and collector loose contact, electric transmission weak effect, specific area adheres to, and then improves the integrated electronic performance of electrode and the fuel cell comprising this material.
Accompanying drawing explanation
Fig. 1 is the high resolution transmission electron microscopy figure (HRTEM) that ultra-thin nickel nano film two panels of the present invention overlaps.
Fig. 2 is the lattice diffraction pattern of the nickel nano film of monolithic shown in Fig. 1, (111) crystal face of the corresponding metallic nickel of spacing of lattice 0.203nm.The provable nickel hydroxide of Fig. 2 is reduced completely, and nanometer sheet is pure metallic nickel nanometer sheet.
Fig. 3 is the X-ray diffractogram (XRD) of material change in material synthesis processes shown in Fig. 1, after foam nickel base grows nickel hydroxide, there will be nickel hydroxide characteristic peak.And after reduction reaction, the characteristic peak of nickel hydroxide disappears, only there is the characteristic peak of standard nickel, prove that nickel hydroxide is all reduced.
Fig. 4 a and Fig. 4 b is the thickness phenogram of the monolithic nickel nano film of material shown in Fig. 1, can find out that the thickness of every sheet nickel nano film is within the scope of 2nm-5nm.
Fig. 5 is the stereoscan photograph figure (SEM) of material of the present invention, wherein clearly shows, and ultra-thin nickel nano film array grows perpendicular to substrate surface, and forms the three-dimensional porous structure that aperture is less than 100nm between ultra-thin nickel nano film; Wherein substrate is nickel foam.
Fig. 6 be material shown in Fig. 5, foam nickel base, nickel hydroxide array and 20% commercial Pt/C catalyst as anode material, oxidation polarization curve respective in 0.5mol/l hydrazine hydrate alkaline solution take reversible hydrogen electrode as reference electrode.As seen from the figure, electrode material of the present invention has minimum overpotential and the fastest electric current growth rate, function admirable when proving the anode material that material of the present invention is oxidized as hydrazine hydrate.
Fig. 7 a is the oxidation polarization curve of material shown in Fig. 5 in variable concentrations hydrazine hydrate solution, and Fig. 7 b is corresponding current versus time curve figure, can find out that material of the present invention can have good stability in the oxidation test at variable concentrations hydrazine hydrate solution.
Fig. 8 be material shown in Fig. 5, foam nickel base, nickel hydroxide array and 20% commercial Pt/C catalyst as cathode material, the polarization curve in 0.1mol/lKOH solution during brine electrolysis liberation of hydrogen take reversible hydrogen electrode as reference electrode.Electrode material of the present invention has overpotential close to Pt/C catalyst and the fastest electric current growth rate, proves that material of the present invention is as function admirable during brine electrolysis hydrogen-precipitating electrode.
Fig. 9 is current versus time curve figure during brine electrolysis liberation of hydrogen in 0.1mol/lKOH solution of material shown in Fig. 5, after wherein using 10 hours, the current density value of commercial Pt/C catalyst reduces to 86.7% of initial current density values, and surface of the present invention has the electrode material of ultra-thin nickel nano film, use after 10 hours, its current density value is 94.9% of initial current density values.As can be seen from Figure, compared to current commercial best Pt/C catalyst, material of the present invention has higher stability.
Figure 10 is the high resolution transmission electron microscopy figure (HRTEM) of super thin metal nickel nano film assembly.Wherein clearly show, mutually intersected by multi-disc nickel nano film, be assembled into outward appearance spheroidal " nickel nano flower ".
Figure 11 a is the Electronic Speculum figure of multiple metal nickel nano sheet assembly shown in Figure 10, Figure 11 b is corresponding electron diffraction diagram, the different crystal faces of corresponding pure nickel.Be reduced completely from the provable nickel hydroxide of Figure 15 b, nano flower is pure metallic nickel nano flower.
Figure 12 is the X-ray diffractogram (XRD) of material change in material synthesis processes shown in Figure 10.Nickel hydroxide array is after reduction reaction, and the characteristic peak of nickel hydroxide disappears, and proves that nickel hydroxide is all reduced.
Figure 13 be material shown in Figure 10, foam nickel base, nickel hydroxide array and 20% commercial Pt/C catalyst as anode material, oxidation polarization curve respective in 0.5mol/l hydrazine hydrate alkaline solution take reversible hydrogen electrode as reference electrode.As seen from the figure, electrode material of the present invention has minimum overpotential and the fastest electric current growth rate, function admirable when proving the anode material that material of the present invention is oxidized as hydrazine hydrate.
Figure 14 is the current versus time curve figure of material shown in Figure 10 in variable concentrations hydrazine hydrate solution, can find out that material of the present invention can have good stability in the oxidation test at variable concentrations hydrazine hydrate solution.
Figure 15 be material shown in Figure 10, foam nickel base, nickel hydroxide array and 20% commercial Pt/C catalyst as cathode material, the polarization curve in 0.1mol/lKOH solution during brine electrolysis liberation of hydrogen take reversible hydrogen electrode as reference electrode.
Figure 16 is material shown in Figure 10 and 20% commercial Pt/C catalyst current versus time curve figure during brine electrolysis liberation of hydrogen in 0.1mol/lKOH solution, and as can be seen from Figure, compared to current commercial best Pt/C catalyst, material of the present invention has higher stability.
Detailed description of the invention
The present invention is further illustrated by following examples.Embodiment is only illustrative, and not restrictive.
Embodiment 1
A. the first reactor is put into by tilting for foam nickel base, the nickel nitrate comprising 0.125 mol/L is added again in this reactor, the aqueous solution of the hexamethylenetetramine of 0.25 mol/L, then this reactor airtight, be warming up to 100 DEG C and keep at autogenous pressures carrying out hydro-thermal reaction in 10 hours, with at this foam nickel base this substrate grown nickel hydroxide nano chip arrays vertical on the surface;
B. take out this foam nickel base, washing is also dry;
C. the second reactor is put into by tilting for the nickel hydroxide nano chip arrays substrate after step b process, add in this reactor again and comprise the solution that the concentration of NaOH in ethylene glycol is 0.625 mol/L, seal this reactor, be warming up to 160 DEG C and keep at autogenous pressures carrying out alcohothermal reaction in 12 hours, making nickel hydroxide nano sheet original appearance described in each be reduced into nickel nano film.After the reaction of this alcohothermal terminates, open after this second reactor is cooled to room temperature; And the foam nickel base of again taking out after this reduction, washing also, after vacuum drying, saves backup under the condition of starvation.
The high magnification transmission electron microscope figure of the super thin metal nickel nano film obtained is see accompanying drawing 1, its lattice diffraction pattern is see accompanying drawing 2, its XRD spectra is see accompanying drawing 3, its single-sheet thickness is see accompanying drawing Fig. 4 a and Fig. 4 b, its SEM figure being grown on nickel foam is see accompanying drawing 5, its in the alkaline solution of hydrazine hydrate hydrazine hydrate oxidation polarization curve see accompanying drawing 6, its polarization curve in the hydrazine hydrate solution of variable concentrations and stability test figure are see accompanying drawing 7a and Fig. 7 b, the cathodic polarization curve figure of its brine electrolysis liberation of hydrogen in 0.1mol/LKOH solution is see accompanying drawing 8, the current versus time curve figure of its brine electrolysis liberation of hydrogen in 0.1mol/LKOH solution is see accompanying drawing 9.
Embodiment 2
See the method in embodiment 1, the sodium borohydride of 0.33mol/L will be added in the reduction system in embodiment 1 step c, and when other condition is constant, the assembly of nickel nano film can be prepared, i.e. nickel nano flower.
The high magnification transmission electron microscope figure of the ultra-thin nickel nano film assembly materials obtained is see accompanying drawing 10, its high magnification transmission electron microscope figure and electron diffraction diagram are see accompanying drawing 11a and Figure 11 b, its XRD spectra is see accompanying drawing 12, its in the alkaline solution of hydrazine hydrate hydrazine hydrate oxidation polarization curve see accompanying drawing 13, its stability test figure in the hydrazine hydrate solution of variable concentrations is see accompanying drawing 14, the cathodic polarization curve figure of its brine electrolysis liberation of hydrogen in 0.1mol/LKOH solution is see accompanying drawing 15, the current versus time curve figure of its brine electrolysis liberation of hydrogen in 0.1mol/LKOH solution is see accompanying drawing 16.
Each experimental data shown in the drawings, sufficient proof surface of the present invention has the excellent properties that the electrode material of super thin metal nickel nano film array and surface have the electrode material of metal nickel nano sheet assembly, its a lot of physicochemical property has surmounted the Pt/C electrode material of current commercialization greatly, is an important breakthrough in electrode material field.