CN105148924A

CN105148924A - P-NiO/n-ZnO heterojunction photocatalytic material as well as preparation method and application thereof

Info

Publication number: CN105148924A
Application number: CN201510519795.1A
Authority: CN
Inventors: 矫淑杰; 周廷龙; 李海力; 朱春光
Original assignee: Harbin Institute of Technology
Current assignee: Harbin Institute of Technology
Priority date: 2015-08-22
Filing date: 2015-08-22
Publication date: 2015-12-16

Abstract

The invention discloses a p-NiO/n-ZnO heterojunction photocatalytic material as well as a preparation method and an application thereof. According to the photocatalytic material, ITO (indium tin oxide) is taken as a substrate, ZnO nano arrays grow on the ITO substrate, then NiO grid structures grow on the ZnO nano arrays, and a double-layer composite structure of ZnO/NiO is formed. NiO/ZnO heterogeneous pn junctions are prepared on the transparent conductive film substrate (ITO) with a hydrothermal method, photoelectrons and electron holes are effectively separated under the action of built-in fields of the pn junctions, the photocatalytic performance is improved, the research of the photocatalytic performance is carried out, and accordingly, the NiO/ZnO heterogeneous pn junctions have good application prospects in the aspect of photocatalytic degradation of organic matters.

Description

P-NiO/n-ZnO heterojunction photocatalysis material and preparation method thereof and application

Technical field

The invention belongs to the technical field of catalysis material and preparation thereof, relate to a kind of NiO/ZnO heterojunction photocatalysis material and preparation method thereof.

Background technology

Along with China's rapid development of economy, pollution problem is also day by day serious, and the contour toxic pollutant of sewage, waste gas and byproduct of reaction produces in a large number, the waste water of especially weaving, producing in the industrial processes such as printing and dyeing, containing dyestuff, accessory substance and inorganic salts etc., all difficult biodegradable waste water.Photocatalyst has can make full use of that sunshine, reaction condition are gentle, simple operation and other advantages, can the effectively various dyestuff of catalytic degradation, organic matter and inorganic matter, is an important channel of the global water pollutions of solution.

Semiconductor pn junction type composite photocatalyst material comprises homogeneous pn junction and heterogenous pn junction, relates to n-type semiconductor and p-type semiconductor material.Space-charge region is defined in the interface of pn knot, produce a built-in field from n to p, this electric field can be diffused into the photo-generated carrier directional separation of electric field region, electronics is assembled in n-type semiconductor side, hole is assembled in p-type semiconductor side, effectively can reduce the compound of photo-generated carrier compared to simple p-type or N-shaped material, effectively improve photocatalysis efficiency.

Zinc oxide (ZnO) is a kind of broad-band gap (3.37eV) semi-conducting material, there is high electron transfer rate and long light induced electron life-span, appearance of nano material enriches simultaneously, makes it be with a wide range of applications in fields such as photocatalysis degradation organic contaminant, photocatalysis hydrogen production, solar cells.But, under involuntary doping condition, because the existence of the donor-type defects such as Lacking oxygen and zinc gap makes the conduction type of ZnO be N-shaped, and be difficult to obtain the p-type ZnO of high carrier concentration due to self-compensation mechanism, limit the application that zno-based pn ties.In this case, the p-type semiconductor material and the ZnO that need to find other form heterogenous pn junction.NiO is a kind of p-type broad-band gap (band gap 3.5-4.0eV) semi-conducting material, can form p-NiO/n-ZnO heterogenous pn junction, for photocatalysis field with ZnO.

Summary of the invention

The object of this invention is to provide a kind of p-NiO/n-ZnO heterojunction photocatalysis material and preparation method thereof and application, utilize hydro-thermal method at transparent conductive film substrate (ITO) upper preparation NiO/ZnO heterogenous pn junction, the built-in field effect that light induced electron is tied at pn with hole is effectively separated, improve photocatalysis performance, carry out the research of photocatalysis performance, shown that NiO/ZnO heterogenous pn junction has good application prospect in photocatalysis to degrade organic matter.

The object of the invention is to be achieved through the following technical solutions:

A kind of n-NiO/p-ZnO heterojunction photocatalysis material, in ITO Grown ZnO nano array, then grows NiO network in ZnO nano array, forms the two-layer composite of ZnO/NiO.

A preparation method for said n-NiO/p-ZnO heterojunction photocatalysis material, utilizes hydrothermal method to synthesize ZnO nano post array and NiO nanometer grid structure, and final acquisition n-NiO/p-ZnO heterojunction structure, for photocatalysis field.Concrete technical scheme is as follows:

The cleaning of step one, ITO substrate:

ITO is placed in concentration be 7% hydrochloric acid soak 5-10s, with deionized water rinsing ITO surface clean hydrochloric acid; Recycling cleanser ultrasonic cleaning 10-15min; With the cleanser on deionized water rinsing ITO surface after taking out, ultrasonic cleaning 10-15min in acetone and ethanol; Clean by deionized water, ITO is dried up for subsequent use.

Step 2, making ZnO collosol and gel:

The growth raw material of Seed Layer is the sol gel solution of zinc oxide, and its preparation process is as follows: by the zinc acetate (Zn (CH of mass ratio 3.8: 1 ₃cOO) ₂2H ₂and lithium hydroxide (LiOHH O) ₂o) be dissolved in 100-500ml absolute ethyl alcohol, at 80-100 DEG C, rapid stirring 5-10min, is cooled to room temperature for subsequent use.

Step 3, making ZnO Seed Layer:

On electro-conductive glass, the uniform sol-gel film of one deck is plated by czochralski method, concrete steps are as follows: clean ITO substrate is suspended at 10-30min in the collosol and gel configured in step 2, then at the uniform velocity lift makes its surface have the uniform liquid film of one deck, put it into 120-150 DEG C of freeze-day with constant temperature 10-30min in electrothermostat again, in order to obtain being combined Seed Layer comparatively closely with substrate, the Seed Layer obtained need be put into 150-300 DEG C, tubular annealing stove insulation 10-30min, so count and once lift.The Seed Layer of experiment requires 3-12 lift.After having lifted, the ITO with ZnO Seed Layer is saved backup.

Step 4, making ZnO nano-array:

By prepare etc. the zinc acetate of molar concentration and the mixed aqueous solution (0.01 ~ 0.1mol/L) of hexamethylenetetramine pour in the polytetrafluoroethyllining lining of reactor, compactedness controls 60 ~ 80%; Faced down by the ITO substrate growth with Seed Layer prepared in step 3 and put into reactor, sealed reactor also puts into heated at constant temperature drying box, at 70 ~ 100 DEG C, be incubated 2 ~ 6 hours; Be down to room temperature, have the ITO substrate of ZnO nano post array to take out by long, with deionized water rinsing, natural drying in atmosphere, obtained ZnO nano array.

Step 5, preparation NiO nanostructured:

Pour in the polytetrafluoroethyllining lining of reactor by the mixed aqueous solution (concentration ratio is 1: 1-5: 1) of the nickel nitrate of the certain molar concentration rate prepared and hexamethylenetetramine, compactedness controls 60 ~ 80%; Have the ITO substrate growth of ZnO nano array to face down placement in a kettle. by long, sealed reactor also puts into heated at constant temperature drying box, at 70 ~ 100 DEG C, be incubated 4 ~ 24 hours; Be down to room temperature, ITO substrate is taken out, with deionized water rinsing, natural drying in atmosphere, obtained NiO/ZnO hetero-junctions.

The present invention has the following advantages:

1, the built in field that p-NiO/n-ZnO heterogenous pn junction photochemical catalyst utilizes pn to tie can effectively be separated light induced electron and hole, suppresses Carrier recombination, significantly improves photocatalysis efficiency.

2, utilize hydro-thermal method, ITO substrate has synthesized ZnO nanorod (post, line) array and NiO, has prepared p-NiO/n-ZnO heterogenous pn junction photochemical catalyst, synthetic method is simple, and cost is low, is applicable to large area deposition.

3, hetero-junctions is grown on substrate and is convenient to reclaim and reuse, and has good DEVELOPMENT PROSPECT for large-scale production and application.

Accompanying drawing explanation

Fig. 1 is NiO/ZnO hetero-junctions XRD collection of illustrative plates prepared by hydro-thermal method;

Fig. 2 is SEM (SEM) front elevation of ZnO nano-rod array prepared by hydro-thermal method;

Fig. 3 is the SEM front elevation of NiO network prepared by hydro-thermal method;

Fig. 4 is NiO/ZnO hetero-junctions SEM sectional view prepared by hydro-thermal method;

Fig. 5 is the I-V curve map of NiO/ZnO hetero-junctions;

Fig. 6 is that NiO/ZnO hetero-junctions is under light illumination to the curve map of methyl orange solution resolution ratio.

Detailed description of the invention

Below in conjunction with accompanying drawing, technical scheme of the present invention is further described; but be not limited thereto; everyly technical solution of the present invention modified or equivalent to replace, and not departing from the spirit and scope of technical solution of the present invention, all should be encompassed in protection scope of the present invention.

Embodiment 1:

One, substrate cleaning: ITO substrate selects size to be 1 × 1cm ², ITO substrate is placed in concentration be 7% watery hydrochloric acid soak 10s, with deionized water rinsing ITO surface clean hydrochloric acid; Recycling cleanser ultrasonic cleaning 10min; With the cleanser on deionized water rinsing ITO surface after taking out, each ultrasonic cleaning 10min in acetone and ethanol; Clean by deionized water, ITO is dried up for subsequent use.

Two, Seed Layer preparation: accurately take two parts of 2.75g zinc acetate (Zn (CH with electronic balance ₃cOO) ₂2H ₂o) and 0.725 lithium hydroxide (LiOH2H ₂o) absolutely dry beaker is placed in for subsequent use; Measuring 500ml absolute ethyl alcohol is contained in beaker, a copy of it zinc acetate and lithium hydroxide is added and fills in the beaker of absolute ethyl alcohol, at ambient temperature solution water-bath is heated to 80 DEG C; After 80 DEG C of insulation 5min, another part of zinc acetate and lithium hydroxide are added in solution fast, take out after being again incubated 5min at this temperature and be cooled to room temperature, in whole process, need ceaselessly high-speed stirred.By the solution sealing finally obtained, and be placed in the standing at least 24h of 0 DEG C-5 DEG C dry, refrigerator, treat that solution clear can use (noting: can not be mixed into water in the whole preparation process of collosol and gel).Pulling apparatus is utilized to be suspended in by substrate in ZnO collosol and gel, at the uniform velocity propose after leaving standstill 30min, and be placed in room temperature environment, after repeating above-mentioned steps twice after substrate surface absolute ethyl alcohol evaporates completely again, substrate be placed in thermostatic drying chamber, rise to 150 DEG C by room temperature, and naturally cool to room temperature after being incubated 30min at this temperature.In order to obtain being combined Seed Layer comparatively closely with substrate, the Seed Layer obtained need be put into 300 DEG C, tubular annealing stove insulation 30min.So for once to lift, the required Seed Layer of experiment needs six lifts.

Three, ZnO nano array preparation: first have the substrate growth of Seed Layer to face down length and put into the reactor inner bag cleaned and dry; Configure the hexa (C of the 0.03mol/L of 15ml respectively ₆h ₁₂n ₄) and the zinc acetate (Zn (CH of 0.03mol/L ₃cOO) ₂2H ₂o) solution, fully mixes the solution in two beakers after high-speed stirred medicine fully dissolves; Pour in the liner of the reactor of 1 50ml by after the two mix and blend 10min; Finally put reactor shell, moved to after tightening hydro-thermal reaction kettle cover in thermostatic drying chamber, rise to 90 DEG C from room temperature and keep this temperature 4 hours.By the time reaction terminates rear taking-up sample deionized water rinsing sample surfaces, is rinsed by sample surfaces after losing no time and is dried by sample, then dip the hydrochloric acid wipe samples nonconductive surface of 7% with cotton balls.

Four, NiO preparation: have the ITO substrate slice aufwuchsplate of ZnO nano post array to put into the reactor inner bag cleaned and dry down by long; Configure the hexa of the 0.06mol/L of 15ml and the nickel nitrate of 0.12mol/L respectively, after high-speed stirred, the solution in two beakers fully mixes after fully dissolving by medicine; Pour in the liner of the reactor of 1 50ml by after the two mix and blend 10min; Finally put reactor shell, moved to after tightening hydro-thermal reaction kettle cover in thermostatic drying chamber, rise to 90 DEG C from room temperature and keep this temperature 12 hours.By the time reaction terminates rear taking-up sample deionized water rinsing sample surfaces, is rinsed by sample surfaces after losing no time and is dried by sample, then dip the hydrochloric acid wipe samples nonconductive surface of 7% with cotton balls.

The present embodiment prepares the XRD spectra of the NiO/ZnO hetero-junctions of gained as shown in Figure 1, can observe the diffraction maximum of ZnO and NiO; As shown in Figures 2 and 3, ZnO nano post presents obvious hexagon to SEM figure, and NiO presents network, has large surface area, can improve the adsorption rate of pollutant, thus improves photocatalysis efficiency; Fig. 4 gives the SEM sectional view of hetero-junctions, and display Hydrothermal Growth obtains double-deck NiO/ZnO composite construction; Fig. 5 is the I-V characteristic curve of NiO/ZnO hetero-junctions, illustrates obvious pn and ties rectification characteristic.

Embodiment 2:

The present embodiment is as different from Example 1: the concentration of HMT and nickel nitrate in embodiment 1 is changed into 0.06mol/L and 0.18mol/L, and other concrete steps are with embodiment 1.

Embodiment 3:

Using certain density methyl orange as target degradation product, carrying out simulated solar light source with solar simulator, carrying out photocatalysis test to preparing NiO/ZnO heterojunction photocatalyst.

The p-NiO/n-ZnO hetero-junctions obtained in embodiment 1 is carried out Photocatalytic Degradation On Methyl Orange Solution study, radiation source is solar simulator (500W xenon lamp).Concrete experiment is: be 1cm by area ²sample vertically put into methyl orange solution, irradiate solution and sample surfaces with analog light source, the time is 60 minutes, every 10 minutes, takes out part methyl orange solution, tests its absorbance by ultraviolet specrophotometer.In order to compare the photocatalysis effect of p-NiO/n-ZnO hetero-junctions, also photocatalysis test is carried out respectively to the ZnO nano-rod array obtained on ITO substrate under similarity condition and NiO.As shown in Figure 6, compare with simple NiO with simple ZnO nano array, the p-NiO/n-ZnO hetero-junctions under equal conditions shows more excellent photocatalysis performance.

Claims

1. a p-NiO/n-ZnO heterojunction photocatalysis material, is characterized in that described catalysis material take ITO as substrate, in ITO Grown ZnO nano array, then in ZnO nano array, grows NiO network, forms the two-layer composite of ZnO/NiO.

2. a preparation method for p-NiO/n-ZnO heterojunction photocatalysis material described in claim 1, is characterized in that described preparation method is as follows:

One, making ZnO Seed Layer:

(1) clean ITO substrate is suspended at 10-30min in ZnO collosol and gel, then at the uniform velocity lift makes its surface have the uniform liquid film of one deck, put it into 120-150 DEG C of freeze-day with constant temperature 10-30min in electrothermostat again, finally the Seed Layer obtained is put into 150-300 DEG C, tubular annealing stove insulation 10-30min, so count and once lift;

(2) step (1) 3-12 time is repeated;

(3) after having lifted, the ITO with ZnO Seed Layer is saved backup;

Two, making ZnO nano-array:

By etc. the zinc acetate of molar concentration and the mixed aqueous solution of hexamethylenetetramine pour in the polytetrafluoroethyllining lining of reactor, the ITO substrate growth with Seed Layer of preparation in step one is faced down and puts into reactor, sealed reactor also puts into heated at constant temperature drying box, at 70 ~ 100 DEG C, be incubated 2 ~ 6 hours; Be down to room temperature, have the ITO substrate of ZnO nano post array to take out by long, with deionized water rinsing, natural drying in atmosphere, obtained ZnO nano array;

Three, NiO nanostructured is prepared:

The mixed aqueous solution of nickel nitrate and hexamethylenetetramine is poured in the polytetrafluoroethyllining lining of reactor, the ITO substrate growth of ZnO nano array is had to face down placement in a kettle. by long, sealed reactor also puts into heated at constant temperature drying box, at 70 ~ 100 DEG C, be incubated 4 ~ 24 hours; Be down to room temperature, ITO substrate is taken out, with deionized water rinsing, natural drying in atmosphere, obtained NiO/ZnO hetero-junctions.

3. the preparation method of p-NiO/n-ZnO heterojunction photocatalysis material according to claim 2, is characterized in that the cleaning method of described ITO substrate is as follows:

4. the preparation method of p-NiO/n-ZnO heterojunction photocatalysis material according to claim 2, is characterized in that the preparation method of described ZnO collosol and gel is as follows:

The zinc acetate of mass ratio 3.8:1 and lithium hydroxide are dissolved in 100-500ml absolute ethyl alcohol, at 80-100 DEG C, rapid stirring 5-10min, is cooled to room temperature for subsequent use.

5. the preparation method of p-NiO/n-ZnO heterojunction photocatalysis material according to claim 2, is characterized in that the concentration of described zinc acetate and hexamethylenetetramine is 0.01 ~ 0.1mol/L.

6. the preparation method of p-NiO/n-ZnO heterojunction photocatalysis material according to claim 2, is characterized in that the compactedness of the mixed aqueous solution of described zinc acetate and hexamethylenetetramine in polytetrafluoroethyllining lining controls 60 ~ 80%.

7. the preparation method of p-NiO/n-ZnO heterojunction photocatalysis material according to claim 2, is characterized in that the molar concentration rate of described nickel nitrate and hexamethylenetetramine is 1:1-5:1.

8. the preparation method of p-NiO/n-ZnO heterojunction photocatalysis material according to claim 2, is characterized in that the compactedness of the mixed aqueous solution of described nickel nitrate and hexamethylenetetramine in polytetrafluoroethyllining lining controls 60 ~ 80%.

9. the application of p-NiO/n-ZnO heterojunction photocatalysis material in photocatalysis field described in claim 1.