A modified cobalt phosphate / cobalt phosphide heterojunction composite material, a preparation method and application thereof

Abstract

The application discloses a modified cobalt phosphate / cobalt phosphide heterojunction composite material and a preparation method and application thereof, and comprises a base material and a carbon-coated cobalt phosphate / cobalt phosphide heterojunction nanosheet structure; the carbon-coated cobalt phosphate / cobalt phosphide heterojunction nanosheet structure is firmly anchored between the base material through a chemical bond; the cobalt phosphate / cobalt phosphide nanosheet structure exists in a heterojunction form; the size of the cobalt phosphate / cobalt phosphide nanosheet structure is 0.5-5 microns; and the thickness is 1-30 nanometers. The carbon-coated cobalt phosphate / cobalt phosphide heterojunction nanosheet structure is constructed on the base material, the catalytic performance of the catalytic material is effectively improved, and the catalytic material has the characteristics of recyclable and cyclic utilization.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalytic decomposition of water to produce hydrogen, and particularly relates to a modified cobalt phosphate / cobalt phosphide heterojunction composite material and a preparation method and application thereof. BACKGROUND

[0002] Transition metal-based materials, such as sulfides, phosphides, nitrides, and selenides, have attracted attention due to their high catalytic activity, low cost, rich properties, and tunable nanostructures. However, these catalysts face challenges during use, such as oxidation, exfoliation / deposition, or rearrangement of their nanostructures, which reduces their catalytic activity and long-term repeatable catalytic cycle stability.

[0003] Cobalt phosphide is an important transition metal catalyst, but it faces problems such as reduced catalytic activity and non-reusability in practical use, which limits its practical application. How to improve the morphology and structure of the catalytic material through modification and other preparation methods to improve the catalytic performance of the material, and how the catalytic material can be recycled and reused, are not clearly explained in the prior art. SUMMARY

[0004] In order to overcome the defects existing in the prior art, the purpose of the present application is to provide a modified cobalt phosphate / cobalt phosphide heterojunction composite material and a preparation method and application thereof. By constructing a carbon-coated cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the substrate, the catalytic performance of the catalytic material is effectively improved, and the material has the characteristics of recyclable and reusable.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0006] A modified cobalt phosphate / cobalt phosphide heterojunction composite material, comprising a substrate and a carbon-coated cobalt phosphate / cobalt phosphide heterojunction nanosheet structure, the carbon-coated cobalt phosphate / cobalt phosphide heterojunction nanosheet structure is firmly anchored between the substrate through a chemical bond, the cobalt phosphate / cobalt phosphide nanosheet structure exists in the form of a heterojunction, and the size of the cobalt phosphate / cobalt phosphide nanosheet structure is 0.5-5 μm and the thickness is 1-30 nm.

[0007] The nanosheet structure contains both cobalt phosphate and cobalt phosphide phases, a heterojunction is formed at the interface between the two phases, the chemical bond is only a carbon-cobalt bond (C-Co), and the nanosheet is firmly anchored between the carbon substrate through the C-Co bond.

[0008] A preparation method of a modified cobalt phosphate / cobalt phosphide heterojunction composite material, comprising the following steps:

[0009] a. A certain amount of cobalt salt is dissolved in deionized water, and after stirring uniformly for a certain time, a certain amount of NaBH4 is added and stirred uniformly to obtain solution A;

[0010] b. The treated substrate is immersed in solution A, and after a certain period of time, it is taken out and washed with deionized water to obtain a substrate loaded with cobalt hydroxide nanosheets on the surface;

[0011] c. The substrate loaded with cobalt hydroxide nanosheets on the surface is placed in a tube furnace, a phosphorus source is placed upstream of the tube furnace, and phosphating treatment is carried out under an inert atmosphere for a certain period of time to obtain a substrate loaded with a cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the surface. The purpose of the phosphating treatment is to obtain cobalt phosphate / cobalt phosphide (obtained by controlling the phosphating time) by phosphating cobalt hydroxide;

[0012] d. The substrate loaded with a cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the surface is immersed in a carbon source precursor solution for a certain period of time, and after high-temperature carbonization treatment, the modified cobalt phosphate / cobalt phosphide heterojunction nanosheet structure composite material loaded on the substrate product of the present application can be obtained.

[0013] The cobalt salt in step a is any one of cobalt nitrate, cobalt chloride, etc., and the concentration of the cobalt salt is 10-500 mM. NaBH4 is used as a reducing agent to reduce the cobalt salt. The mass ratio of NaBH4 to cobalt salt is 1:20-120.

[0014] The standing time in step b is 0.5-12 h. The substrate is immersed in concentrated nitric acid for treatment. Commercially available concentrated nitric acid has a mass fraction of about 68%.

[0015] The substrate in step b is any one of carbon felt and carbon cloth.

[0016] The phosphorus source in step c is one or more of sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, magnesium hypophosphite, barium hypophosphite, and hypophosphorous acid. The phosphorus source needs to be in excess relative to the molar amount of cobalt hydroxide, and the molar ratio of the phosphorus source to cobalt hydroxide is 1-3:1.

[0017] The phosphating temperature in step c is 500-1000°C, which is used to phosphatize cobalt hydroxide into cobalt phosphate / cobalt phosphide.

[0018] The phosphating time in step c is 1-24 h.

[0019] The carbon source precursor solution in step d is glucose or dopamine. The high-temperature carbonization treatment condition is that the carbon source such as glucose is decomposed into carbon at a high temperature of 800-1200°C in an inert gas.

[0020] The modified cobalt phosphate / cobalt phosphide heterojunction composite material is used for catalytic decomposition of water to produce hydrogen and oxygen, and catalytic reduction of CO2.

[0021] The beneficial effects of the present application are:

[0022] The preparation process is simple, the photocatalytic active material is loaded on the substrate without the need of a binder, the C-Co bond is used for anchoring, the preparation cost is low, and a noble metal is not needed as an active component.

[0023] The built-in electric field of the cobalt phosphate / cobalt phosphide heterojunction in the application can effectively promote the separation of photo-induced charge holes and improve the catalytic efficiency; the interface between the cobalt phosphate and the cobalt phosphide has a potential difference due to the difference in internal electron concentration, which becomes a built-in electric field.

[0024] The ultrathin nanosheet structure of the cobalt phosphate / cobalt phosphide heterojunction in the application has a high specific surface area, fully contacts with reactants, improves the catalytic reaction rate, and has a catalyst with super strong photocatalytic capacity.

[0025] The carbon-coated cobalt phosphate / cobalt phosphide in the application can effectively guarantee the catalytic stability of the cobalt phosphate / cobalt phosphide. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The schematic diagram of the final product of the modified cobalt phosphate / cobalt phosphide heterojunction composite material in the application is shown. DETAILED DESCRIPTION

[0027] The application will be further described in detail below with reference to the drawings.

[0028] Example 1

[0029] a. 5.8g of cobalt chloride hexahydrate was dissolved in 100mL of deionized water, and after stirring uniformly for 20min, a certain amount of 0.1g NaBH4 was added and stirred uniformly to obtain solution A;

[0030] b. The treated substrate was immersed in solution A, and after standing for 0.5h, it was taken out and washed with deionized water to obtain a substrate loaded with cobalt hydroxide nanosheets on the surface;

[0031] c. The substrate loaded with cobalt hydroxide nanosheets on the surface was placed in the middle of a tube furnace, and a sufficient amount of hypophosphorous acid was placed upstream of the tube furnace, and phosphorization treatment was carried out at 700℃ for 1h under an argon atmosphere to obtain a substrate loaded with cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the surface.

[0032] d. The substrate loaded with cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the surface was placed into a dopamine precursor solution for 1h, and after carbonization treatment at 900℃, the product substrate loaded with the modified cobalt phosphate / cobalt phosphide heterojunction nanosheet structure composite material was obtained.

[0033] Example 2

[0034] a. 11.6 g of cobalt chloride hexahydrate was dissolved in 100 mL of deionized water, and after stirring uniformly for 20 min, a certain amount of 0.2 g of NaBH4 was added, and after stirring uniformly, solution A was obtained;

[0035] b. The treated substrate was immersed in solution A, and after standing for 0.5 h, it was taken out and washed with deionized water to obtain a substrate loaded with cobalt hydroxide nanosheets on the surface;

[0036] c. The substrate loaded with cobalt hydroxide nanosheets on the surface was placed in the middle of a tube furnace, and a sufficient amount of hypophosphorous acid was placed upstream of the tube furnace, and phosphating treatment was carried out at 700°C for 1 h under an argon atmosphere to obtain a substrate loaded with a cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the surface.

[0037] d. The substrate loaded with a cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the surface was placed into a dopamine precursor solution for 1 h, and after carbonization treatment at 900°C, a modified cobalt phosphate / cobalt phosphide heterojunction nanosheet structure composite material loaded on the substrate of the product of the application was obtained.

[0038] Example 3

[0039] a. 11.6 g of cobalt nitrate was dissolved in 100 mL of deionized water, and after stirring uniformly for 20 min, a certain amount of 0.2 g of NaBH4 was added, and after stirring uniformly, solution A was obtained;

[0040] b. The treated substrate was immersed in solution A, and after standing for 0.5 h, it was taken out and washed with deionized water to obtain a substrate loaded with cobalt hydroxide nanosheets on the surface;

[0041] c. The substrate loaded with cobalt hydroxide nanosheets on the surface was placed in the middle of a tube furnace, and a sufficient amount of hypophosphorous acid was placed upstream of the tube furnace, and phosphating treatment was carried out at 800°C for 2 h under an argon atmosphere to obtain a substrate loaded with a cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the surface.

[0042] d. The substrate loaded with a cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the surface was placed into a dopamine precursor solution for 1 h, and after carbonization treatment at 900°C, a modified cobalt phosphate / cobalt phosphide heterojunction nanosheet structure composite material loaded on the substrate of the product of the application was obtained.

[0043] Example 4

[0044] a. 11.6 g of cobalt nitrate was dissolved in 100 mL of deionized water, and after stirring uniformly for 20 min, a certain amount of 0.2 g of NaBH4 was added, and after stirring uniformly, solution A was obtained;

[0045] b. The treated substrate was immersed in solution A, and after standing for 1 h, it was taken out and washed with deionized water to obtain a substrate loaded with cobalt hydroxide nanosheets on the surface;

[0046] c. Put the substrate loaded with cobalt hydroxide nanosheet on the surface into the tube furnace, place enough hypophosphorous acid upstream of the tube furnace, and carry out phosphating treatment at 800°C for 4h under argon atmosphere to obtain the substrate loaded with cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the surface.

[0047] d. After the substrate loaded with cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the surface is put into the dopamine precursor solution for 1h, the modified cobalt phosphate / cobalt phosphide heterojunction nanosheet structure composite material loaded on the substrate product of the present application can be obtained after carbonization treatment at 900°C.

[0048] Example 5

[0049] a. Dissolve 11.6g of cobalt chloride hexahydrate in 100mL of deionized water, and after stirring uniformly for 20min, add a certain amount of 0.2g NaBH4 to obtain solution A;

[0050] b. After the treated substrate is immersed in solution A, it is placed for 1h, and after being taken out and washed with deionized water, the substrate loaded with cobalt hydroxide nanosheet on the surface is obtained;

[0051] c. Put the substrate loaded with cobalt hydroxide nanosheet on the surface into the tube furnace, place enough hypophosphorous acid upstream of the tube furnace, and carry out phosphating treatment at 800°C for 8h under argon atmosphere to obtain the substrate loaded with cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the surface.

[0052] d. After the substrate loaded with cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the surface is put into the dopamine precursor solution for 2h, the modified cobalt phosphate / cobalt phosphide heterojunction nanosheet structure composite material loaded on the substrate product of the present application can be obtained after carbonization treatment at 900°C.

[0053] Example 6

[0054] a. Dissolve 11.6g of cobalt chloride hexahydrate in 100mL of deionized water, and after stirring uniformly for 20min, add a certain amount of 0.4g NaBH4 to obtain solution A;

[0055] b. After the treated substrate is immersed in solution A, it is placed for 2h, and after being taken out and washed with deionized water, the substrate loaded with cobalt hydroxide nanosheet on the surface is obtained;

[0056] c. Put the substrate loaded with cobalt hydroxide nanosheet on the surface into the tube furnace, place enough hypophosphorous acid upstream of the tube furnace, and carry out phosphating treatment at 800°C for 4h under argon atmosphere to obtain the substrate loaded with cobalt phosphate / cobalt phosphide heterojunction nanosheet structure on the surface.

[0057] d.The substrate loaded with the surface cobalt phosphate / cobalt phosphide heterojunction nanosheet structure is taken out after being immersed in the dopamine precursor solution for 4 h, and the modified cobalt phosphate / cobalt phosphide heterojunction nanosheet structure composite material loaded on the substrate product is obtained after carbonization treatment at 900 DEG C.

[0058] As shown in Figure 1 The substrate is immersed in solution A, and the surface of the substrate is uniformly distributed with cobalt hydroxide nanosheets after standing for 2 h. After phosphorization of the substrate loaded with cobalt hydroxide nanosheets in a tube furnace, the morphology and structure are still nanosheets, and the phase composition is that the cobalt hydroxide nanosheets are converted into cobalt phosphate / cobalt phosphide heterojunction nanosheets.

[0059] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can make equivalent replacements or changes according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A modified cobalt phosphate / cobalt phosphide heterojunction composite, characterized in that, The application relates to a carbon substrate and a carbon-coated cobalt phosphate / cobalt phosphide heterojunction nanosheet structure, the carbon-coated cobalt phosphate / cobalt phosphide heterojunction nanosheet structure is firmly anchored between the carbon substrate through a chemical bond, the cobalt phosphate / cobalt phosphide nanosheet structure exists in a heterojunction form, the size of the cobalt phosphate / cobalt phosphide nanosheet structure is 0.5-5 microns, and the thickness is 1-30 nanometers. The nanosheet structure contains both cobalt phosphate and cobalt phosphide phases, a heterojunction is formed at the interface of the two phases, and the chemical bond is a carbon-cobalt bond C-Co.

2. The method for preparing a modified cobalt phosphate / cobalt phosphide heterojunction composite material according to claim 1, characterized in that, The application also discloses a preparation method of the carbon substrate loaded modified cobalt phosphate / cobalt phosphide heterojunction nanosheet structure composite material. a. A certain amount of cobalt salt is dissolved in deionized water, and after being uniformly stirred for a certain time, a certain amount of NaBH4 is added and uniformly stirred to obtain solution A; b. The treated carbon substrate is immersed in solution A, and after being left to stand for a certain time, the carbon substrate loaded with cobalt hydroxide nanosheets is obtained after the surface is washed with deionized water; c. The carbon substrate loaded with cobalt hydroxide nanosheets is placed in a tubular furnace, a phosphorus source is placed at the upstream of the tubular furnace, and after being phosphorized under an inert atmosphere for a certain time, the carbon substrate loaded with cobalt phosphate / cobalt phosphide heterojunction nanosheet structures is obtained; d. After the carbon substrate loaded with cobalt phosphate / cobalt phosphide heterojunction nanosheet structures is placed in a carbon source precursor solution for a certain time and high-temperature carbonization treatment, the product, the carbon substrate loaded modified cobalt phosphate / cobalt phosphide heterojunction nanosheet structure composite material, is obtained. In step c, the phosphorus source is one or more of sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, magnesium hypophosphite, barium hypophosphite and hypophosphorous acid; and the molar ratio of the phosphorus source to the cobalt hydroxide is 1-3:

1. In step c, the phosphorization temperature is 500-1000 DEG C, and the cobalt hydroxide is phosphorized into cobalt phosphate / cobalt phosphide. In step c, the phosphorization time is 1-24 hours. In step d, the carbon source precursor solution is glucose or dopamine, and the high-temperature carbonization treatment is carried out in an inert gas, and the carbon source is decomposed into carbon at a high temperature of 800-1200 DEG C.

3. The method for preparing a modified cobalt phosphate / cobalt phosphide heterojunction composite material according to claim 2, characterized in that, In step a, the cobalt salt is any one of cobalt nitrate and cobalt chloride, the concentration of the cobalt salt is 10-500 mM, NaBH4 is used as a reducing agent to reduce the cobalt salt, and the mass ratio of the NaBH4 to the cobalt salt is 1:20-120.

4. The method for preparing a modified cobalt phosphate / cobalt phosphide heterojunction composite material according to claim 2, characterized in that, In step b, the standing time is 0.5-12 hours, and the carbon substrate is treated by immersion in concentrated nitric acid. In step b, the carbon substrate is any one of carbon felt and carbon cloth.

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