P-N HETEROJUNCTION COMPOSITE MATERIAL SUPPORTED ON SURFACE OF NICKEL FOAM, PREPARATION METHOD THEREFOR AND APPLICATION THEREOF

Abstract

Disclosed are a P—N heterojunction composite material supported on the surface of nickel foam, a preparation method therefor and the application thereof. The composite material is a supported catalyst which can be used to remove pollutants in water by means of photoelectrocatalysis. The method comprises firstly modifying, by means of a hydrothermal method, a layered nickel-iron bimetallic hydroxide nanosheet on the surface of clean nickel foam, and then modifying cobalt oxide nanowires on the surface of the layered nickel-iron bimetallic hydroxide nanosheet by means of a mixed solvent-thermal method, so as to obtain a P—N heterojunction catalyst composite material supported on the surface of nickel foam (Ni foam@NiFe-LDH/Co.sub.3O.sub.4). The composite material has a good response to visible light, which can greatly enhance the absorption and utilization of light, and is further beneficial to enhance the performance of the catalyst.

Claims

1. A P—N heterojunction composite material supported on the surface of nickel foam, which is characterized in that the preparation method of the P—N heterojunction composite material supported on the surface of nickel foam comprising the following steps: modifying one-dimensional cobalt oxide nanowires on the surface of the layered nickel-iron bimetallic hydroxide nanosheet supported on the surface of nickel foam by means of a mixed solvent-thermal method to obtain the P—N heterojunction composite material supported on the surface of nickel foam.

2. The P—N heterojunction composite material supported on the surface of nickel foam according to claim 1, wherein using nickel foam as the supporter, modifying layered nickel-iron bimetallic hydroxide nanosheet on the surface of nickel foam by means of a hydrothermal method, and then modifying one-dimensional cobalt oxide nanowires on the surface of the layered nickel-iron bimetallic hydroxide nanosheet by means of a mixed solvent-thermal method to obtain a P—N heterojunction composite material supported on the surface of nickel foam.

3. The P—N heterojunction composite material supported on the surface of nickel foam according to claim 2, wherein mixing the precursor solution with nickel foam and then reacting at 120-180° C. for 20-30 h by means of hydrothermal reaction method to obtain the layered nickel-iron bimetallic hydroxide nanosheet supported on the surface of nickel foam; the precursor solution consists of nickel salt, iron salt, water and urea.

4. The P—N heterojunction composite material supported on the surface of nickel foam according to claim 3, wherein in the precursor solution, the molar ratio of divalent metal ion Ni.sup.2+ to trivalent metal ion Fe.sup.3+ is 2:1, and the molar number of urea is 3.8-4.2 times of the sum of the molar numbers of divalent metal ion Ni.sup.2+ and trivalent metal ion Fe.sup.3+.

5. The P—N heterojunction composite material supported on the surface of nickel foam according to claim 1, wherein mixing the layered nickel-iron bimetallic hydroxide nanosheet with cobalt containing solution, and then hydrothermal reacting at 80-100° C. for 6-10 h and then heat treating to obtain the layered nickel-iron bimetallic hydroxide nanosheet supported on the surface of nickel foam, the cobalt containing solution is composed of water, ethanol, cobalt salt and urea.

6. The P—N heterojunction composite material supported on the surface of nickel foam according to claim 5, wherein volume ratio of water to ethanol is 1:1 and molar ratio of urea to cobalt salt is 4:1, the concentration of cobalt salt is 0.003-0.008 g/mL.

7. The P—N heterojunction composite material supported on the surface of nickel foam according to claim 5, wherein heat treatment is to keep temperature at 250° C. for 1.5-2.5 h in air.

8. A method for catalytic purification of pollutants in water bodies, comprising the following steps: modifying one-dimensional cobalt oxide nanowires on the surface of the layered nickel-iron bimetallic hydroxide nanosheet supported on the surface of nickel foam by means of a mixed solvent-thermal method to obtain the P—N heterojunction composite material supported on the surface of nickel foam; adding the P—N heterojunction composite material supported on the surface of nickel foam into water containing pollutants, and performing photocatalytic and/or electrocatalysis to complete the purification of pollutants in the water.

9. A preparation method of P—N heterojunction composite material supported on the surface of nickel foam, comprising the following steps, modifying one-dimensional cobalt oxide nanowires on the surface of the layered nickel-iron bimetallic hydroxide nanosheet supported on the surface of nickel foam by means of a mixed solvent-thermal method to obtain the P—N heterojunction composite material supported on the surface of nickel foam.

10. The application of P—N heterojunction composite material supported on the surface of nickel foam according to claim 1 in the purification of pollutants in the water as a catalyst.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a scanning electron microscope diagram of layered nickel-iron bimetallic hydroxide nanosheet supported on the surface of nickel foam (Ni foam@NiFe-LDH).

[0024] FIG. 2 is a scanning electron microscope diagram of the P—N heterojunction catalyst composite material supported on the surface of nickel foam (Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2) in embodiment 4.

[0025] FIG. 3 is an effect diagram of removal of pollutants by photoelectric catalysis with the P—N heterojunction catalyst composite material supported on the surface of nickel foam (Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2) in embodiment 4.

[0026] FIG. 4 is comparison of pollutant removal effects by photocatalysis, electrocatalysis and photocatalysis with the P—N heterojunction catalyst composite material supported on the surface of nickel foam (Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2) in embodiment 4.

DETAILED DESCRIPTION OF THE INVENTION

[0027] The preparation method of the P—N heterojunction composite material supported on the surface of nickel foam (Ni foam@NiFe-LDH/Co.sub.3O.sub.4) disclosed in the invention is, modifying one-dimensional cobalt oxide nanowires on the surface of the layered nickel-iron bimetallic hydroxide nanosheet supported on the surface of nickel foam by means of a mixed solvent-thermal method to obtain the P—N heterojunction composite material supported on the surface of nickel foam(Ni foam@NiFe-LDH/Co.sub.3O.sub.4), which can be used as catalyst.

Embodiment 1

[0028] Preparation of the NiFe-LDH precursor solution.

[0029] 0.6979 g Ni(NO.sub.3).sub.2.6H.sub.2O, 0.4803 g Fe(NO.sub.3).sub.3.9H.sub.2O and 0.8647 g urea are dissolved in 15 ml deionized water in a round bottom flask under ultrasound, then the mixture are refluxed at 100° C. under stirring for 24 h to obtain the NiFe-LDH precursor solution. The molar ratio of Ni.sup.2+ and Fe.sup.3+ in the precursor solution is 1:2, the molar concentration of Fe.sup.3+ is 0.1 mol/L, and the molar ratio of urea and metal ion is 4 times.

Embodiment 2

[0030] Preparation of Ni foam@NiFe-LDH by a hydrothermal method.

[0031] Ni foam@NiFe-LDH is obtained by a hydrothermal method. Typically, 3 ml the precursor solution of NiFe-LDH in Embodiment 1, 32 ml deionized water and the pretreated Ni foam are transferred to a Teflon-lined stainless steel autoclave and kept in an oven at 160° C. for 24 h. After the reaction is cooled to room temperature, the Ni foam@NiFe-LDH is wash 3 times with water and ethanol, and then dried under vacuum at 60° C. for 24 h. As can be seen from FIG. 1, the SEM image shows that NiFe-LDH nanosheets are evenly distributed on the smooth surface of Ni foam, which is used as photocatalyst in Embodiment 7 to treat Cr(VI). After 100 min, the removal rate of Cr(VI) is 22.3%.

Embodiment 3

[0032] Preparation of Ni foam@NiFe-LDH/Co.sub.3O.sub.4-1 by meas of a mixed solvothermal method.

[0033] Preparation of Ni foam@NiFe-LDH/Co.sub.3O.sub.4-1 is obtained by a mixed solvothermal strategy. In a typical experiment, 0.87 g of Co(NO.sub.3).sub.2.6H2.sub.O and 0.72 g of urea are dissolved in 80 mL of mixed solvents of deionized water and ethanol (V.sub.deionized water: V.sub.ethanol=1:1) to form a pink solution. The above solutions (10 ml the above pink solution and 25 ml the above mixed solvents) and Ni foam@NiFe-LDH obtained in Embodiment 2 are then transferred into a Teflon-lined stainless steel autoclave and kept in an oven at 90° C. for 8 h. After reaction, the product is washed 3 times by deionized water, and annealed at 250° C. for 2 h in Ar flow to obtain Ni foam@NiFe-LDH/Co.sub.3O.sub.4-1. A few Co.sub.3O.sub.4 nanowires appeared on the surface of the NiFe-LDH nanosheets after the second step in-situ growth. Ni foam@NiFe-LDH/Co.sub.3O.sub.4-1 is used as photocatalyst in Embodiment 7 to treat Cr(VI). After 100 min, the removal rate of Cr(VI) is 30.1%.

Embodiment 4

[0034] Preparation of Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 by a mixed solvothermal strategy.

[0035] Preparation of Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 is obtained by a mixed solvothermal strategy. In a typical experiment, 0.87 g of Co(NO.sub.3).sub.2.6H.sub.2O and 0.72 g of urea are dissolved in 80 mL of mixed solvents of deionized water and ethanol (V.sub.deionized water: V.sub.ethanol=1: 1) to form a pink solution. The above solutions (15 ml the above pink solution and 20 ml the above mixed solvents) and Ni foam@NiFe-LDH obtained in Embodiment 2 are then transferred into a Teflon-lined stainless steel autoclave and kept in an oven at 90° C. for 8 h. After reaction, the product is washed 3 times by deionized water, and annealed at 250° C. for 2 h in Ar flow to obtain Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2. As can be seen from FIG. 2, Co.sub.3O.sub.4 nanowires is uniformly loaded on the surface of the NiFe-LDH nanosheet after the second step in-situ growth.

[0036] Adjust the above insulation for 2 h at 250° C. to insulation for 2 hat 300° C., and the rest remain unchanged, to obtain Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2-1, used as photocatalyst in Embodiment 7 to treat Cr(VI). After 100 min, the removal rate of Cr(VI) is 38.5%.

Embodiment 5

[0037] Preparation of Ni foam@NiFe-LDH/Co.sub.3O.sub.4-3 by a mixed solvothermal strategy.

[0038] Preparation of Ni foam@NiFe-LDH/Co.sub.3O.sub.4-3 is obtained by a mixed solvothermal strategy. In a typical experiment, 0.87 g of Co(NO.sub.3).sub.2.6H.sub.2O and 0.72 g of urea are dissolved in 80 mL of mixed solvents of deionized water and ethanol (V.sub.deionized water: V.sub.ethanol=1: 1) to form a pink solution. The above solutions (20 ml the above pink solution and 15 ml the above mixed solvents) and Ni foam@NiFe-LDH obtained in Embodiment 2 are then transferred into a Teflon-lined stainless steel autoclave and kept in an oven at 90° C. for 8 h. After reaction, the product is washed 3 times by deionized water, and annealed at 250° C. for 2 h in Ar flow to obtain Ni foam@NiFe-LDH/Co.sub.3O.sub.4-3. As the increase of Co.sub.3O.sub.4 precursors, the surface of Ni foam@NiFe-LDH/Co.sub.3O.sub.4-3 is completely covered by Co.sub.3O.sub.4 nanowires. Ni foam@NiFe-LDH/Co.sub.3O.sub.4-3 is used as photocatalyst in Embodiment 7 to treat Cr(VI). After 100 min, the removal rate of Cr(VI) is 36.7%.

Embodiment 6

[0039] Preparation of Ni foam@Co.sub.3O.sub.4 by a mixed solvothermal strategy.

[0040] Preparation of Ni foam@Co.sub.3O.sub.4 is obtained by a mixed solvothermal strategy. In a typical experiment, 0.87 g of Co(NO.sub.3).sub.2.6H.sub.2O and 0.72 g of urea are dissolved in 80 mL of mixed solvents of deionized water and ethanol (V.sub.deionized water: V.sub.ethanol=1: 1) to form a pink solution. 35 ml the above pink solution and Ni foam are then transferred into a Teflon-lined stainless steel autoclave and kept in an oven at 90° C. for 8 h. After reaction, the product is washed 3 times by deionized water, and annealed at 250° C. for 2 h in Ar flow to obtain Ni foam@Co.sub.3O.sub.4. After SEM characterization, the surface of Ni foam is completely covered by Co.sub.3O.sub.4 nanowires. Ni foam@Co.sub.3O.sub.4 is used as photocatalyst in Embodiment 7 to treat Cr(VI). After 100 min, the removal rate of Cr(VI) is 31.3%.

Embodiment 7

[0041] The photocatalytic experiment of Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 evaluated by removal of Cr(VI).

[0042] The photocatalytic experiments are performed under light irradiated with a Xenon lamp (300 W). Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 is added into the 50 mL solution of Cr(VI) (10 mg/L) and stirred in dark for 30 min to achieve absorption-desorption equilibrium. And then the suspension is irradiated by a 300 W Xenon lamp source (with a light filter>420 nm) and 3 mL suspension is collected and centrifuged every 20 min to analyze the concentration of Cr(VI). And the concentration of residual Cr(VI) in each period is measured by UV-vis (540 nm) with its working curve. As can be seen from FIG. 4, Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 shows 43.6% removal rate after 100 min through photocatalytic process.

Embodiment 8

[0043] The photocatalytic experiment of Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 evaluated by removal of BPA.

[0044] The photocatalytic experiments are performed under light irradiated with a Xenon lamp (300 W). Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 is added into the 50 mL solution of BPA (10 mg/L) and stirred in dark for 30 min to achieve absorption-desorption equilibrium. And then the suspension is irradiated by a 300 W Xenon lamp source (with a light filter>420 nm) and 3 mL suspension is collected and centrifuged every 20 min to analyze the concentration of BPA. And the concentration of residual BPA in each period is measured by HPLC. As can be seen from FIG. 4, Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 shows 45.2% removal rate after 100 min through photocatalytic process.

Embodiment 9

[0045] The electrocatalytic experiment of Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 evaluated by removal of BPA and Cr(VI).

[0046] The electrocatalytic experiments are performed on CHI660E in dark. The solutions of BPA and Cr(VI) are transferred to a double-chamber photoelectrochemical reaction cell separated by a nafion membrane. Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 is used as the working electrode, the platinum (Pt) wire, Ag/AgCl and 0.1 M Na.sub.2SO.sub.4 are used as counter, reference electrodes and electrolyte, respectively. Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 is added into the solution of BPA and stirred in dark for 30 min to achieve absorption-desorption equilibrium. And then a little voltage (such as 0.7 V) is applied by an electrochemical workstation on working electrod. 3 mL suspension is collected and centrifuged every 20 min to analyze the concentration of BPA and Cr(VI). And the concentration of residual BPA and Cr(VI) in each period is measured by HPLC and UV-vis. As can be seen from FIG. 4, after 100 min through electrocatalytic process, Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 shows 13.1% and 5.3% removal rate of BPA and Cr(VI).

Embodiment 10

[0047] The photoelectrocatalytic experiment of Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 evaluated by removal of BPA and Cr(VI).

[0048] The photoelectrocatalytic experiments are performed on CHI660E under light irradiated with a xenon lamp (300 W). The solutions of BPA and Cr(VI) are transferred to a double-chamber photoelectrochemical reaction cell separated by a nafion membrane. Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 is used as the working electrode, the platinum (Pt) wire, Ag/AgCl and 0.1 M Na.sub.2SO.sub.4 are used as counter, reference electrodes and electrolyte, respectively. Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 is added into the solution of BPA and stirred in dark for 30 min to achieve absorption-desorption equilibrium. And then the suspension is irradiated by a 300 W Xenon lamp source (with a light filter>420 nm) and applied a little voltage (such as 0.7 V) by an electrochemical workstation. 3 mL suspension is collected and centrifuged every 20 min to analyze the concentration of BPA and Cr(VI). And the concentration of residual BPA and Cr(VI) in each period is measured by HPLC and UV-vis. As can be seen from FIG. 4, after 100 min through photoelectrocatalytic process, Ni foam@NiFe-LDH/Co.sub.3O.sub.4-2 shows 98.1% and 97.5% removal rate of BPA and Cr(VI).

[0049] The composite material disclosed by the invention has been proved to be an effective means to improve the catalytic activity of the material. For the p-n heterojunction, when two different types of semiconductors with different Fermi levels are in contact, the carriers will spontaneously flow between semiconductors until reaching the equilibrium state. At the interface of semiconductor junction, two space charge regions with opposite charges will be formed due to the flow of carriers, resulting in the corresponding built-in electric field. The built-in electric field of semiconductor junction is widely used to promote the separation of photogenerated carriers, such as solar cells and photocatalytic systems. In addition, photocatalysis technology, which enhances the catalytic activity by effectively separating the photogenerated charges generated by semiconductor materials excited by light through applied voltage, is one of the effective methods to realize the efficient utilization of solar energy, and is expected to solve the current environmental problems and energy crisis.