Non-metal-doped NiFe LDH composite graphite phase carbon nitride material and preparation method and use

Abstract

The present invention belongs to the field of electrocatalytic materials, specifically relating to a non-metal-doped NiFe LDH composite graphite-phase carbon nitride material, a preparation method, and uses thereof. The present invention provides a non-metal-doped NiFe LDH composite g-C3N4 material, wherein the NiFe LDH composite g-C3N4 material is doped with a non-metallic element; the non-metallic element includes sulfur, phosphorus, selenium, or oxygen. The non-metal-doped NiFe LDH composite g-C3N4 material has high electrical conductivity, thereby improving its catalytic activity. Furthermore, the raw material used is a transition metal source, which is low in cost. This solves the problem in the prior art that electrocatalysts have difficulty in simultaneously achieving high catalytic performance and low cost.

Description

Technical Field

[0001] The present invention belongs to the field of electrocatalytic materials, and in particular relates to a non-metal-doped NiFe LDH composite graphite phase carbon nitride material, a preparation method and an application thereof. Background Art

[0002] Water electrolysis is a renewable method for hydrogen production with the advantages of being environmentally friendly, safe, and having high product purity. However, the half-reaction oxygen evolution reaction (OER) is a complex multi-electron transfer process that is more affected by the kinetic reaction energy barrier and is the main obstacle in water electrolysis. Although commercial RuO2 / IrO2 catalysts have excellent OER electrocatalytic activity, they are made of precious metals, are expensive, and have low stability, making them difficult to use on a large scale. Therefore, the development of low-cost, high-performance non-precious metal OER electrocatalysts is the only way to improve the efficiency of water electrolysis and promote its commercial development.

[0003] Transition metals not only have the advantages of abundant content, high stability, and good environmental compatibility, but more importantly, their partially filled d orbitals have the ability to easily donate / accept electrons, making them promising alternatives to traditional precious metal electrocatalysts. For example, “Two-dimensional / two-dimensional NiFe LDH / g-C3N4 (graphitic carbon nitride) composite photocatalysts for promoting CO2 photoreduction reaction” (Li Han et al., Acta Physico-Chimica Sinica 2021, 37(8)) discloses a NiFe LDH composite g-C3N4 catalyst, which is less expensive than commercial RuO2 catalysts, but has lower catalytic performance than commercial RuO2. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a non-metal-doped NiFe LDH composite graphite phase carbon nitride material and a preparation method and use thereof. The non-metal-doped NiFe LDH composite g-C3N4 material has high conductivity, thereby having higher catalytic activity, low cost, and its preparation method is simple and easy to operate.

[0005] To this end, the present invention provides the following technical solutions:

[0006] A non-metallic doped NiFe LDH composite g-C3N4 material, wherein the NiFe LDH composite g-C3N4 material is doped with non-metallic elements; the non-metallic elements include sulfur, phosphorus, selenium or oxygen.

[0007] A method for preparing the non-metal-doped NiFe LDH composite g-C3N4 material comprises the following steps:

[0008] When the doped non-metal is sulfur or phosphorus, the NiFe LDH composite g-C3N4 material is weighed and placed on one side of the reaction container, and the sulfur source or phosphorus source is weighed and placed on the other side of the reaction container, and then calcined in an inert gas atmosphere. The calcination conditions are a temperature of 280-400° C., holding for 1-4 hours, and cooling;

[0009] When the doped non-metal is selenium, a NiFe LDH composite g-C3N4 material is weighed and placed on one side of a reaction vessel, a selenium source is weighed and placed on the other side of the reaction vessel, and then calcined in an inert gas atmosphere. The calcination conditions are: first, keeping the temperature at 280-350°C for 1-2 hours, then keeping the temperature at 400-500°C for 1-4 hours, and cooling;

[0010] When the doped non-metal is oxygen, the NiFe LDH composite g-C3N4 material is calcined in an oxygen-containing atmosphere at a temperature of 280-450°C (preferably 350°C), kept warm for 1-4 (preferably 2) hours, and cooled.

[0011] Optionally, when the doped non-metal is sulfur, the calcination conditions are a temperature of 300° C. and a time of 1.5 hours; and / or

[0012] When the doped non-metal is sulfur, the heating rate is 5-15°C·min -1 and / or

[0013] When the doped non-metal is sulfur, 15-35 parts by weight of the NiFe LDH composite g-C3N4 material is weighed and placed on one side of the reaction container, and 30-270 parts by weight of a sulfur source is weighed and placed on the other side of the reaction container; and / or

[0014] When the doped non-metal is sulfur, the sulfur source is sublimed sulfur or sulfur;

[0015] Optionally, when the doped non-metal is sulfur, the heating rate is 8°C·min in the calcination conditions. -1 ;

[0016] Optionally, when the doped non-metal is sulfur, 25 parts by weight of the NiFe LDH composite g-C3N4 material is weighed and placed on one side of the reaction container, and 100 parts by weight of the sulfur source is weighed and placed on the other side of the reaction container.

[0017] Optionally, when the doped non-metal is phosphorus, the calcination condition is a temperature of 350° C. and a holding time of 2 hours; and / or

[0018] When the doped non-metal is phosphorus, the heating rate is 1-10°C·min -1 and / or

[0019] When the doped non-metal is phosphorus, 15-35 parts by weight of the NiFe LDH composite g-C3N4 material is weighed and placed on one side of the reaction container, and 125-420 parts by weight of a phosphorus source is weighed and placed on the other side of the reaction container; and / or

[0020] When the doped non-metal is phosphorus, the phosphorus source is sodium hypophosphite monohydrate;

[0021] Optionally, when the doped non-metal is phosphorus, the heating rate in the calcination condition is 2°C·min -1 ;

[0022] Optionally, when the doped non-metal is phosphorus, 25 parts by weight of the NiFe LDH composite g-C3N4 material is weighed and placed on one side of the reaction container, and 300 parts by weight of the phosphorus source is weighed and placed on the other side of the reaction container.

[0023] Optionally, when the doped non-metal is selenium, the calcination conditions are: first heating to 350° C., keeping warm for 2 hours, then heating to 450° C., keeping warm for 2 hours; and / or

[0024] When the doped non-metal is selenium, the calcination conditions are as follows: first, at 1-10°C·min -1 The heating rate is raised to 280-350℃ and kept at this temperature for 1-2h, and then the temperature is raised to 280-350℃ at a rate of 1-10℃·min -1 The temperature is raised to 400-500°C at a heating rate of 100-200°C and kept at this temperature for 1-4 hours; and / or

[0025] When the doped non-metal is selenium, 15-35 parts by weight of the NiFe LDH composite g-C3N4 material is weighed and placed on one side of the reaction container, and 30-210 parts by weight of a selenium source is weighed and placed on the other side of the reaction container; and / or

[0026] When the doped non-metal is selenium, the selenium source is selenium powder;

[0027] Optionally, when the doped non-metal is selenium, the calcination conditions are first carried out at 2°C·min -1 The heating rate is raised to 280-350℃ and kept at this temperature for 1-2h, and then the temperature is raised to 2℃·min -1 The temperature is raised to 400-500℃ at a heating rate and kept at this temperature for 1-4h;

[0028] Optionally, when the doped non-metal is selenium, 25 parts by weight of the NiFe LDH composite g-C3N4 material is weighed and placed on one side of the reaction container, and 75 parts by weight of the selenium source is weighed and placed on the other side of the reaction container.

[0029] Optionally, when the doped non-metal is oxygen, the calcination condition is a temperature of 350° C. for 2 hours; and / or

[0030] When the doped non-metal is oxygen, the heating rate during calcination is 1-10°C·min -1 ;

[0031] Optionally, in the calcination conditions, the heating rate during calcination is 2°C·min -1 .

[0032] Optionally, a method for preparing a NiFe LDH composite g-C3N4 material is also included, comprising the following steps:

[0033] (1) calcining melamine powder at 400-600°C in an air atmosphere for 1-3 hours to obtain a yellow product; grinding the yellow product into powder, heating it to 400-500°C in an air atmosphere and keeping it warm for 3-7 hours, and then cooling it to obtain a light yellow product, i.e., g-C3N4 nanosheets;

[0034] (2) Weigh the g-C3N4 nanosheets and dissolve them in methanol, ethanol, acetone and / or water, and the resulting solution is recorded as solution A; weigh nickel nitrate hexahydrate, iron nitrate nonahydrate and urea and dissolve them in water, add trisodium citrate dihydrate under stirring, and the resulting solution is recorded as solution B; under stirring, add solution A dropwise to solution B, and then keep the mixture at 100-180°C for 24-55 hours, and then cool, wash and dry to obtain a NiFe LDH composite g-C3N4 material;

[0035] Optionally, (1) calcining melamine powder at 500° C. in an air atmosphere for 2 h to obtain a yellow product; grinding the obtained yellow product into powder, heating it to 500° C. in an air atmosphere and keeping the temperature for 4.5 h, and then cooling it to obtain a light yellow product, i.e., g-C3N4 nanosheets;

[0036] (2) Weigh the g-C3N4 nanosheets and dissolve them in methanol, ethanol, acetone and / or water, and the resulting solution is recorded as solution A; weigh nickel nitrate hexahydrate, iron nitrate nonahydrate and urea and dissolve them in water, add trisodium citrate dihydrate under stirring, and the resulting solution is recorded as solution B; under stirring, add solution A dropwise to solution B, and then keep the mixture at 150°C for 48 hours, then cool, wash and dry to obtain NiFe LDH composite g-C3N4 material.

[0037] Optionally, in step (1), in preparing the yellow product, the heating rate of the calcination is 1-10°C·min -1 and / or

[0038] In the step (1), in the preparation of the light yellow product, the heating rate is 1-10°C·min -1 ;

[0039] Optionally, in step (1), in preparing the yellow product, the heating rate of the calcination is 5°C·min -1 and / or

[0040] In the step (1), in the preparation of the light yellow product, the heating rate is 2°C·min -1 .

[0041] Optionally, in step (2), in preparing solution A, 5-20 parts by weight of the g-C3N4 nanosheets are weighed and dissolved in 15-60 parts by volume of methanol; and / or

[0042] In step (2), in preparing solution B, 200-400 parts by weight of nickel nitrate hexahydrate, 120-200 parts by weight of ferric nitrate nonahydrate, and 120-200 parts by weight of urea are weighed and dissolved in 60-100 parts by volume of water, and 2-8 parts by weight of trisodium citrate dihydrate are added under stirring; and / or

[0043] In step (2), 10-50 parts by volume of solution A is added dropwise to 25-120 parts by volume of solution B;

[0044] The ratio of parts by weight to parts by volume is mg / ml or g / L;

[0045] Optionally, in step (2), in preparing solution A, 10 parts by weight of the g-C3N4 nanosheets are weighed and dissolved in 30 parts by volume of methanol; and / or

[0046] In step (2), in preparing solution B, 350 parts by weight of nickel nitrate hexahydrate, 160 parts by weight of ferric nitrate nonahydrate, and 170 parts by weight of urea are weighed and dissolved in 80 parts by volume of water, and 5.8 parts by weight of trisodium citrate dihydrate are added under stirring; and / or

[0047] In step (2), 30 ml of solution A was added dropwise to 74.8 parts by volume of solution B.

[0048] The use of the non-metal-doped NiFe LDH composite g-C3N4 material or the non-metal-doped NiFe LDH composite g-C3N4 material prepared by the preparation method as an electrocatalyst;

[0049] Optionally, it can be used as an electrocatalyst for a half-reaction oxygen evolution reaction.

[0050] The technical solution of the present invention has the following advantages:

[0051] 1. The non-metal-doped NiFe LDH composite g-C3N4 material provided by the present invention is doped with a non-metallic element; the non-metallic element includes sulfur, phosphorus, selenium or oxygen; the non-metal-doped NiFe LDH composite g-C3N4 material has higher conductivity, thereby improving its catalytic activity, and the raw material used is a transition metal source, which is low in cost.

[0052] 2. The preparation method of the non-metal doped NiFe LDH composite g-C3N4 material provided by the present invention comprises the following steps: when the doped non-metal is sulfur or phosphorus, weighing the NiFe LDH composite g-C3N4 material and placing it on one side of the reaction container, weighing the sulfur source or phosphorus source and placing it on the other side of the reaction container, and then calcining it in an inert gas atmosphere, the calcination conditions are as follows: the temperature is 280-400°C, keeping warm for 1-4 hours, and cooling; when the doped non-metal is selenium, weighing the NiFe LDH composite g-C3N4 material and placing it on one side of the reaction container, weighing the selenium source and placing it on the other side of the reaction container, and then calcining it in an inert gas atmosphere, the calcination conditions are as follows: first keeping warm at a temperature of 280-350°C for 1-2 hours, then keeping warm at 400-500°C for 1-4 hours, and cooling; when the doped non-metal is oxygen, the NiFe The LDH composite g-C3N4 material is calcined in an oxygen-containing atmosphere at a temperature of 280-450°C (preferably 350°C), kept warm for 1-4 hours (preferably 2 hours), and cooled. In the above method, non-metallic elements such as sulfur, phosphorus, selenium or oxygen are directly doped into the NiFe LDH composite g-C3N4 material through a topochemical conversion method. The prepared sulfur-, phosphorus-, selenium- or oxygen-doped NiFe LDH composite g-C3N4 material has high conductivity and thus high catalytic activity, low cost, and a simple method and easy operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0054] Figure 1 This is an electron scanning microscope image of the NiFe LDH composite g-C3N4 material in the experimental example of the present invention;

[0055] Figure 2 is an electron scanning microscope image of the S / NiFe LDH composite g-C3N4 material in the experimental example of the present invention;

[0056] Figure 3 is an electron scanning microscope image of the P / NiFe LDH composite g-C3N4 material in the experimental example of the present invention;

[0057] Figure 4 is an electron scanning microscope image of the Se / NiFe LDH composite g-C3N4 material in the experimental example of the present invention;

[0058] Figure 5 is an electron scanning microscope image of the O / NiFe LDH composite g-C3N4 material in the experimental example of the present invention;

[0059] Figure 6 is the X-ray diffraction spectrum of NiFe LDH composite g-C3N4 material in the experimental example of the present invention;

[0060] Figure 7 This is the EDS elemental analysis of the S / NiFe LDH composite g-C3N4 material in the experimental example of the present invention;

[0061] Figure 8 This is the EDS elemental analysis of the P / NiFe LDH composite g-C3N4 material in the experimental example of the present invention;

[0062] Figure 9 This is the EDS elemental analysis of the Se / NiFe LDH composite g-C3N4 material in the experimental example of the present invention;

[0063] Figure 10 This is the EDS elemental analysis of the O / NiFe LDH composite g-C3N4 material in the experimental example of the present invention;

[0064] Figure 11 is the polarization curve of the experimental sample in the experimental example of the present invention. DETAILED DESCRIPTION

[0065] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0066] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0067] Example 1

[0068] This embodiment provides a method for preparing a non-metal-doped NiFe LDH composite g-C3N4 material, comprising the following steps:

[0069] (1) First, 20g of melamine powder was placed in an alumina crucible in an air atmosphere at a heating rate of 5℃·min -1 After heating to 500℃ and calcining for 2h, a yellow product (large g-C3N4) was obtained; the yellow product was ground into powder, 5g of the ground powder was weighed and evenly spread on a porcelain boat, and then calcined in air at a heating rate of 2℃·min -1 The temperature was raised to 500°C and kept at this temperature for 4.5 h. After cooling, the product was taken out to obtain a light yellow product, which was g-C3N4 nanosheets.

[0070] (2) Weigh 10 mg of g-C3N4 nanosheets and dissolve them in 30 mL of methanol. Ultrasonicate for at least 30 minutes to disperse them evenly to obtain solution A. Weigh 0.35 g of nickel nitrate hexahydrate, 0.16 g of ferric nitrate nonahydrate, and 0.17 g of urea and dissolve them in 80 mL of water. Add 5.8 mg of trisodium citrate dihydrate under stirring, stir evenly, and take out 74.8 mL as solution B. Under stirring, add solution A dropwise to solution B, and finally pour the mixed solution into a high-pressure reactor lined with polytetrafluoroethylene. Place the high-pressure reactor in a forced air drying oven and keep it at 150°C for 48 hours. After cooling, take out the product, wash it several times with water and ethanol by centrifugation, collect the product, and finally dry it in a drying oven overnight to obtain NiFe LDH composite g-C3N4 material.

[0071] (3) Weigh 25 mg of NiFe LDH composite g-C3N4 material and place it on the downstream of the porcelain boat, then weigh 100 mg of sulfur powder and place it on the upstream of the porcelain boat as a sulfur source, and calcine it in an argon atmosphere at 8 ° C min -1 The temperature was raised to 300°C at a heating rate and kept at this temperature for 1.5 hours. After cooling, the material was taken out to obtain the sulfur-doped NiFe LDH composite g-C3N4 material.

[0072] Example 2

[0073] This embodiment provides a method for preparing a non-metal-doped NiFe LDH composite g-C3N4 material, comprising the following steps:

[0074] (1) First, 20g of melamine powder was placed in an alumina crucible in an air atmosphere at a heating rate of 1℃·min -1After heating to 400℃ and calcining for 3h, a yellow product (large g-C3N4) was obtained; the yellow product was ground into powder, 5g of the ground powder was weighed and evenly spread on a porcelain boat, and then calcined in air at a heating rate of 1℃·min -1 The temperature was raised to 400 °C and kept at this temperature for 7 h. After cooling, the product was taken out to obtain a light yellow product, which was g-C3N4 nanosheets.

[0075] (2) Weigh 5 mg of g-C3N4 nanosheets and dissolve them in 60 mL of methanol. Ultrasonicate for at least 30 minutes to disperse them evenly to obtain solution A. Weigh 0.20 g of nickel nitrate hexahydrate, 0.20 g of iron nitrate nonahydrate, and 0.12 g of urea and dissolve them in 100 mL of water. Add 2 mg of trisodium citrate dihydrate under stirring, stir evenly, and take out 100 mL as solution B. Under stirring, add solution A (40 ml) dropwise to solution B. Finally, pour the mixed solution into a high-pressure reactor lined with polytetrafluoroethylene. Place the high-pressure reactor in a forced air drying oven and keep it at 100 ° C for 55 hours. After cooling, take out the product, wash it several times with water and ethanol by centrifugation, collect the product, and finally dry it in a drying oven overnight to obtain NiFe LDH composite g-C3N4 material.

[0076] (3) Weigh 15 mg of NiFe LDH composite g-C3N4 material and place it on the downstream of the porcelain boat, then weigh 30 mg of sulfur powder and place it on the upstream of the porcelain boat as a sulfur source, and calcine it in an argon atmosphere at 5 ° C min -1 The temperature was raised to 280°C at a heating rate and kept at this temperature for 4 hours. After cooling, the material was taken out to obtain the sulfur-doped NiFe LDH composite g-C3N4 material.

[0077] Example 3

[0078] This embodiment provides a method for preparing a non-metal-doped NiFe LDH composite g-C3N4 material, comprising the following steps:

[0079] (1) First, 20g of melamine powder was placed in an alumina crucible in an air atmosphere at a heating rate of 10℃·min -1 After heating to 600℃ and calcining for 1h, a yellow product (large g-C3N4) was obtained; the yellow product was ground into powder, 5g of the ground powder was weighed and evenly spread on a porcelain boat, and then calcined in air at a heating rate of 10℃·min -1 The temperature was raised to 500°C and kept at this temperature for 3 h. After cooling, the product was taken out to obtain a light yellow product, which was g-C3N4 nanosheets.

[0080] (2) Weigh 20 mg of g-C3N4 nanosheets and dissolve them in 15 mL of methanol. Ultrasonicate for at least 30 minutes to disperse them evenly to obtain solution A. Weigh 0.40 g of nickel nitrate hexahydrate, 0.12 g of ferric nitrate nonahydrate, and 0.20 g of urea and dissolve them in 60 mL of water. Add 8 mg of trisodium citrate dihydrate under stirring, stir evenly, and take out 36 mL as solution B. Under stirring, add solution A (15 mL) dropwise to solution B. Finally, pour the mixed solution into a high-pressure reactor lined with polytetrafluoroethylene. Place the high-pressure reactor in a forced air drying oven and keep it at 180 ° C for 24 hours. After cooling, take out the product, wash it with water and ethanol by centrifugation several times, collect the product, and finally dry it in a drying oven overnight to obtain NiFe LDH composite g-C3N4 material.

[0081] (3) Weigh 35 mg of NiFe LDH composite g-C3N4 material and place it on the downstream of the porcelain boat, then weigh 270 mg of sulfur powder and place it on the upstream of the porcelain boat as a sulfur source, and calcine it in an argon atmosphere at 15 ° C min -1 The temperature was raised to 400°C at a heating rate and kept at this temperature for 1 hour. After cooling, the material was taken out to obtain the sulfur-doped NiFe LDH composite g-C3N4 material.

[0082] Example 4

[0083] The difference between this embodiment and embodiment 1 is that the step (3) is as follows: 25 mg of NiFe LDH composite g-C3N4 material is weighed and placed in the downstream of the porcelain boat, and 300 mg of sodium hypophosphite monohydrate is weighed and placed in the upstream of the porcelain boat as a phosphorus source, and calcined in an argon atmosphere at 2 ° C. min -1 The temperature was raised to 350°C at a heating rate and kept at this temperature for 2 hours. After cooling, the material was taken out to obtain a phosphorus-doped NiFe LDH composite g-C3N4 material.

[0084] Example 5

[0085] The difference between this embodiment and embodiment 2 is that the step (3) is as follows: 15 mg of NiFe LDH composite g-C3N4 material is weighed and placed in the downstream of the porcelain boat, and 125 mg of sodium hypophosphite monohydrate is weighed and placed in the upstream of the porcelain boat as a phosphorus source, and calcined in an argon atmosphere at 1 ° C. min -1 The temperature was raised to 280°C at a heating rate and kept at this temperature for 4 hours. After cooling, the material was taken out to obtain a phosphorus-doped NiFe LDH composite g-C3N4 material.

[0086] Example 6

[0087] The difference between this embodiment and embodiment 3 is that the step (3) is as follows: 35 mg of NiFe LDH composite g-C3N4 material is weighed and placed in the downstream of the porcelain boat, and 420 mg of sodium hypophosphite monohydrate is weighed and placed in the upstream of the porcelain boat as a phosphorus source, and calcined in an argon atmosphere at 10 ° C. min -1 The temperature was raised to 400°C at a heating rate and kept at this temperature for 1 hour. After cooling, the material was taken out to obtain a phosphorus-doped NiFe LDH composite g-C3N4 material.

[0088] Example 7

[0089] The difference between this embodiment and embodiment 1 is that the step (3) is as follows: 25 mg of NiFe LDH composite g-C3N4 material is weighed and placed in the downstream of the porcelain boat, 75 mg of selenium powder is weighed and placed in the upstream of the porcelain boat as a selenium source, and calcined in an argon atmosphere at 2 ° C. min -1 The heating rate was raised to 350℃ and kept at this temperature for 2h, and then the temperature was raised to 350℃ at a rate of 2℃·min -1 The heating rate was increased to 450°C and kept warm for 2 h. After cooling, the sample was taken out to obtain a selenium-doped NiFe LDH composite g-C3N4 material.

[0090] Example 8

[0091] The difference between this embodiment and embodiment 2 is that the step (3) is as follows: 15 mg of NiFe LDH composite g-C3N4 material is weighed and placed in the downstream of the porcelain boat, 30 mg of selenium powder is weighed and placed in the upstream of the porcelain boat as a selenium source, and calcined in an argon atmosphere at 1 ° C. min -1 The heating rate was raised to 280℃ and kept at this temperature for 2h, and then the heating rate was increased to 1℃·min -1 The heating rate was increased to 400°C and kept at this temperature for 4 hours. After cooling, the material was taken out to obtain a selenium-doped NiFe LDH composite g-C3N4 material.

[0092] Example 9

[0093] The difference between this embodiment and embodiment 3 is that the step (3) is as follows: 35 mg of NiFe LDH composite g-C3N4 material is weighed and placed in the downstream of the porcelain boat, 210 mg of selenium powder is weighed and placed in the upstream of the porcelain boat as a selenium source, and calcined in an argon atmosphere at 10 ° C. min -1 The heating rate was raised to 350℃ and kept at this temperature for 1h, and then the temperature was raised to 350℃ at a rate of 10℃·min -1 The heating rate was increased to 500°C and kept at this temperature for 1 hour, and then taken out after cooling to obtain the selenium-doped NiFe LDH composite g-C3N4 material.

[0094] Example 10

[0095] The difference between this embodiment and embodiment 1 is that the step (3) is as follows: 30 mg of NiFe LDH composite g-C3N4 material is weighed and placed in a porcelain boat, the porcelain boat is placed in a muffle furnace, and the temperature is set at 2°C·min under air atmosphere. -1 The temperature was raised to 350°C at a heating rate and kept at this temperature for 2 h. After cooling, the material was taken out to obtain the oxygen-doped NiFe LDH composite g-C3N4 material.

[0096] Example 11

[0097] The difference between this embodiment and embodiment 1 is that the step (3) is as follows: 30 mg of NiFe LDH composite g-C3N4 material is weighed and placed in a porcelain boat, the porcelain boat is placed in a muffle furnace, and the temperature is set at 1°C·min under air atmosphere. -1 The temperature was raised to 280°C at a heating rate and kept at this temperature for 4 hours. After cooling, the material was taken out to obtain the oxygen-doped NiFe LDH composite g-C3N4 material.

[0098] Example 12

[0099] The difference between this embodiment and embodiment 1 is that the step (3) is as follows: 30 mg of NiFe LDH composite g-C3N4 material is weighed and placed in a porcelain boat, the porcelain boat is placed in a muffle furnace, and the temperature is set at 10 ° C. min under air atmosphere. -1 The temperature was raised to 450°C at a heating rate and kept at this temperature for 1 hour. After cooling, the material was taken out to obtain the oxygen-doped NiFe LDH composite g-C3N4 material.

[0100] Experimental example

[0101] 1. Experimental Materials

[0102] Experimental sample: NiFe LDH composite g-C3N4 material prepared in step (2) of Example 1;

[0103] The sulfur-doped NiFe LDH composite g-C3N4 material (abbreviated as S / NiFeLDH composite g-C3N4) prepared in step (3) of Example 1;

[0104] The phosphorus-doped NiFe LDH composite g-C3N4 material (abbreviated as P / NiFe LDH composite g-C3N4) prepared in Example 4;

[0105] Selenium-doped NiFe LDH composite g-C3N4 material (abbreviated as Se / NiFe LDH composite g-C3N4) prepared in Example 7;

[0106] The oxygen-doped NiFe LDH composite g-C3N4 material prepared in Example 10 (abbreviated as O / NiFe LDH composite g-C3N4);

[0107] Commercial RuO2 material was purchased from Aladdin.

[0108] 2. Experimental Methods and Results

[0109] (1) Scanning electron microscope

[0110] The experimental samples (except the control) were scanned by electron scanning microscope (SEM), and the results were as follows: Figure 1-5 As shown, Figure 1 The SEM images of the NiFe LDH composite g-C3N4 material show that the synthesized yellow-brown NiFe LDH composite g-C3N4 material has a clear lamellar structure, consistent with the characteristics of NiFe LDH. Due to the influence of g-C3N4, small spheres with a radius of approximately 50-100nm appear above the lamellar structure. Figure 2 The SEM results of S / NiFe LDH composite g-C3N4 material show that the sulfur-doped composite material presents large particles with a diameter of about 3 μm, and there is still a clear lamellar structure on the large particles. Figure 3 This is the SEM result of P / NiFe LDH composite g-C3N4 material. From the figure, we can see that the phosphorus-doped composite material has less agglomeration and more clear layers. Figure 4 This is the SEM result of Se / NiFe LDH composite g-C3N4 material. It can be seen from the figure that they are all nano-scale fine particles; Figure 5 These are the SEM results of O / NiFe LDH composite g-C3N4 materials. A clear two-dimensional lamellar structure can be seen from the figure. Except for the selenium-doped composite material that is broken at a high temperature and recrystallized into fine particles, the other composite materials have well inherited the two-dimensional structure of the precursor NiFe LDH composite g-C3N4.

[0111] (2) X-ray diffraction measurement

[0112] The experimental samples (except the control) were subjected to X-ray diffraction, and the results were as follows Figure 6-10 As shown, Figure 6 This is the X-ray diffraction measurement result of NiFe LDH composite g-C3N4 material. It can be seen from the figure that a series of characteristic peaks appear near 11°, 23°, 34°, and 61°, corresponding to the diffraction signals of the (003), (006), (012), and (113) crystal planes of NiFe LDH, respectively. There is a broad diffraction peak near 28°, which is consistent with the diffraction peak of g-C3N4. The weak peak intensity indicates that the crystallinity is not high. Figure 7Energy dispersive spectrometer (EDS) elemental analysis of the S / NiFeLDH composite g-C3N4 material shows that the S element accounts for 44.23%, which proves that sulfur has been successfully incorporated into the NiFe LDH composite g-C3N4 material; Figure 8 This is the EDS element analysis of P / NiFe LDH composite g-C3N4 material. It can be seen from the figure that P element accounts for 36.93%, which proves that phosphorus element is successfully doped into NiFe LDH composite g-C3N4 material; Figure 9 EDS elemental analysis of Se / NiFe LDH composite g-C3N4 material shows that Se element accounts for 16.31%, which proves that Se-doped NiFe LDH composite g-C3N4 material was successfully prepared; Figure 10 The EDS element analysis of O / NiFe LDH composite g-C3N4 material shows that the O element accounts for 53.15%, which proves that the oxygen element doped NiFe LDH composite g-C3N4 material was successfully prepared.

[0113] (3) Electrocatalytic performance test

[0114] Electrochemical tests were performed using a CHI 660D electrochemical workstation with a standard three-electrode system. A modified glassy carbon electrode (GCE), a graphite rod, and a Hg / HgO electrode were used as the working electrode, counter electrode, and reference electrode, respectively. 1 mol L -1 4 mg of the experimental sample and 2 mg of acetylene black were dispersed in a mixed solution containing 700 μL of ethanol, 275 μL of water and 25 μL of Nafion (5 wt%, binder) and ultrasonically dispersed to form a uniform ink. Then, 6.30 μL (loading amount of 0.35 mg cm -2 ) ink was dropped onto a polished GCE and dried at room temperature to serve as the working electrode. In the experiments, all potential settings were calibrated to the reversible hydrogen electrode using the Nernst equation, which is as follows: (RHE): E(vs.RHE) = E 测试 + E (vs. Hg / HgO) + 0.059 * pH; the overpotential (η) value was calculated according to the formula: η = E (vs. RHE) - 1.23 V. The linear sweep voltammetry (LSV) test was carried out in a N2 atmosphere at 2 mV s -1 The test was performed at a scan rate of 1.1 V to 1.9 V (vs. RHE) (with 85% iR compensation correction). Cyclic voltammetry was first used to activate the sample. After the signal stabilized, linear sweep voltammetry was performed. Polarization curves were plotted with current density as the ordinate and potential as the abscissa.

[0115] The test results are as follows Figure 11As shown in the figure, it can be seen that P / NiFe LDH composite g-C3N4 and S / NiFe LDH composite g-C3N4 materials show better performance, achieving the same current density of 10 mA cm -2 Only 250mV and 236mV overpotentials are required, which is better than the performance of commercial RuO2 (current density of 10mA·cm -2 The performance of O / NiFe LDH composite g-C3N4, Se / NiFe LDH composite g-C3N4 and NiFe LDH composite g-C3N4 materials is slightly inferior. -2 The overpotentials at the current density of 321mV, 292mV, and 273mV are respectively. A small oxidation peak appears in the NiFe LDH composite g-C3N4, P / NiFe LDH composite g-C3N4, and S / NiFe LDH composite g-C3N4 composites, indicating that these materials have certain oxidizability.

[0116] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst, characterized in that: The NiFe LDH composite g-C3N4 material is doped with a non-metallic element; the non-metallic element is phosphorus, selenium or oxygen; The preparation method of the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst comprises the following steps: When the doped non-metal is phosphorus, a NiFe LDH composite g-C3N4 material is weighed and placed on one side of a reaction container, a phosphorus source is weighed and placed on the other side of the reaction container, and then calcined in an inert gas atmosphere at a temperature of 280-400° C., kept warm for 1-4 hours, and cooled; When the doped non-metal is selenium, a NiFe LDH composite g-C3N4 material is weighed and placed on one side of a reaction vessel, a selenium source is weighed and placed on the other side of the reaction vessel, and then calcined in an inert gas atmosphere. The calcination conditions are: first, keeping the temperature at 280-350°C for 1-2 hours, then keeping the temperature at 400-500°C for 1-4 hours, and cooling; When the doped non-metal is oxygen, the NiFe LDH composite g-C3N4 material is calcined in an atmosphere containing oxygen. The calcination conditions are a temperature of 280-450° C., keeping the temperature for 1-4 hours, and cooling.

2. A method for preparing the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to claim 1, characterized in that: The steps include: When the doped non-metal is phosphorus, a NiFe LDH composite g-C3N4 material is weighed and placed on one side of a reaction container, a sulfur source or a phosphorus source is weighed and placed on the other side of the reaction container, and then calcined in an inert gas atmosphere at a temperature of 280-400° C., holding for 1-4 hours, and cooling; When the doped non-metal is selenium, a NiFe LDH composite g-C3N4 material is weighed and placed on one side of a reaction vessel, a selenium source is weighed and placed on the other side of the reaction vessel, and then calcined in an inert gas atmosphere. The calcination conditions are: first, keeping the temperature at 280-350°C for 1-2 hours, then keeping the temperature at 400-500°C for 1-4 hours, and cooling; When the doped non-metal is oxygen, the NiFe LDH composite g-C3N4 material is calcined in an atmosphere containing oxygen. The calcination conditions are a temperature of 280-450° C., keeping the temperature for 1-4 hours, and cooling.

3. The method for preparing the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to claim 2, characterized in that: When the doped non-metal is phosphorus, the calcination condition is a temperature of 350° C. and a holding time of 2 hours; and / or When the doped non-metal is phosphorus, the heating rate is 1-10°C·min -1 and / or When the doped non-metal is phosphorus, 15-35 parts by weight of the NiFe LDH composite g-C3N4 material is weighed and placed on one side of the reaction container, and 125-420 parts by weight of a phosphorus source is weighed and placed on the other side of the reaction container; and / or When the doped non-metal is phosphorus, the phosphorus source is sodium hypophosphite monohydrate.

4. The method for preparing the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to claim 3, characterized in that: When the doped non-metal is phosphorus, the heating rate is 2°C·min -1 ; And / or, when the doped non-metal is phosphorus, 25 parts by weight of the NiFe LDH composite g-C3N4 material is weighed and placed on one side of the reaction container, and 300 parts by weight of the phosphorus source is weighed and placed on the other side of the reaction container.

5. The method for preparing the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to claim 2 or 3, characterized in that: When the doped non-metal is selenium, the calcination conditions are: firstly heating to 350° C., keeping the temperature for 2 hours, then heating to 450° C., keeping the temperature for 2 hours; and / or When the doped non-metal is selenium, the calcination conditions are as follows: first, at 1-10°C·min -1 The heating rate is raised to 280-350℃ and kept at this temperature for 1-2h, and then the temperature is raised to 280-350℃ at a rate of 1-10℃·min -1 The temperature is raised to 400-500°C at a heating rate of 100-200°C and kept at this temperature for 1-4 hours; and / or When the doped non-metal is selenium, 15-35 parts by weight of the NiFe LDH composite g-C3N4 material is weighed and placed on one side of the reaction container, and 30-210 parts by weight of a selenium source is weighed and placed on the other side of the reaction container; and / or When the doped non-metal is selenium, the selenium source is selenium powder.

6. The method for preparing the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to claim 5, characterized in that: When the doped non-metal is selenium, the calcination conditions are as follows: first, at 2°C·min -1 The heating rate is raised to 280-350℃ and kept at this temperature for 1-2h, and then the temperature is raised to 2℃·min -1 The temperature is raised to 400-500℃ at a heating rate and kept at this temperature for 1-4h; And / or, when the doped non-metal is selenium, 25 parts by weight of the NiFe LDH composite g-C3N4 electrocatalyst is weighed and placed on one side of the reaction container, and 75 parts by weight of the selenium source is weighed and placed on the other side of the reaction container.

7. The method for preparing the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to any one of claims 2 to 3, characterized in that: When the doped non-metal is oxygen, the calcination conditions are: a temperature of 350° C. for 2 hours; and / or When the doped non-metal is oxygen, the heating rate during calcination is 1-10°C·min -1 .

8. The method for preparing the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to any one of claims 2 to 3, characterized in that: The heating rate during calcination is 2°C·min -1 .

9. The method for preparing the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to any one of claims 2 to 3, characterized in that: Also included is a method for preparing a NiFe LDH composite g-C3N4 material, comprising the following steps: (1) calcining melamine powder at 400-600°C in an air atmosphere for 1-3 hours to obtain a yellow product; grinding the yellow product into powder, heating it to 400-500°C in an air atmosphere and keeping it warm for 3-7 hours, and then cooling it to obtain a light yellow product, i.e., g-C3N4 nanosheets; (2) Weigh the g-C3N4 nanosheets and dissolve them in methanol, ethanol, acetone and / or water, and the resulting solution is recorded as solution A; weigh nickel nitrate hexahydrate, iron nitrate nonahydrate and urea and dissolve them in water, add trisodium citrate dihydrate under stirring, and the resulting solution is recorded as solution B; under stirring, add solution A dropwise to solution B, and then keep warm at 100-180°C for 24-55 hours, and then cool, wash and dry to obtain NiFe LDH composite g-C3N4 material.

10. The method for preparing the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to claim 9, characterized in that: (1) calcining melamine powder at 500°C in an air atmosphere for 2 hours to obtain a yellow product; grinding the yellow product into powder, heating it to 500°C in an air atmosphere and keeping it warm for 4.5 hours, and then cooling it to obtain a light yellow product, i.e., g-C3N4 nanosheets; (2) Weigh the g-C3N4 nanosheets and dissolve them in methanol, ethanol, acetone and / or water, and the resulting solution is recorded as solution A; weigh nickel nitrate hexahydrate, iron nitrate nonahydrate and urea and dissolve them in water, add trisodium citrate dihydrate under stirring, and the resulting solution is recorded as solution B; under stirring, add solution A dropwise to solution B, and then keep the mixture at 150°C for 48 hours, then cool, wash and dry to obtain NiFe LDH composite g-C3N4 material.

11. The method for preparing the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to claim 10, characterized in that: In the step (1), in preparing the yellow product, the heating rate of the calcination is 1-10°C·min -1 and / or In the step (1), in the preparation of the light yellow product, the heating rate is 1-10°C·min -1 .

12. The method for preparing the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to claim 11, characterized in that: In the step (1), in the preparation of the yellow product, the heating rate of the calcination is 5°C·min -1 and / or In the step (1), in the preparation of the light yellow product, the heating rate is 2°C·min -1 .

13. The method for preparing the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to any one of claims 11 to 12, characterized in that: In the step (2), in preparing solution A, 5-20 parts by weight of the g-C3N4 nanosheets are weighed and dissolved in 15-60 parts by volume of methanol; and / or In step (2), in preparing solution B, 200-400 parts by weight of nickel nitrate hexahydrate, 120-200 parts by weight of ferric nitrate nonahydrate, and 120-200 parts by weight of urea are weighed and dissolved in 60-100 parts by volume of water, and 2-8 parts by weight of trisodium citrate dihydrate are added under stirring; and / or In step (2), 10-50 parts by volume of solution A is added dropwise to 25-120 parts by volume of solution B; The ratio of parts by weight to parts by volume is mg / ml or g / L.

14. The method for preparing the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to claim 13, characterized in that: In the step (2), in preparing solution A, 10 parts by weight of the g-C3N4 nanosheets are weighed and dissolved in 30 parts by volume of methanol; and / or In step (2), in preparing solution B, 350 parts by weight of nickel nitrate hexahydrate, 160 parts by weight of ferric nitrate nonahydrate, and 170 parts by weight of urea are weighed and dissolved in 80 parts by volume of water, and 5.8 parts by weight of trisodium citrate dihydrate are added under stirring; and / or In the step (2), 30 ml of solution A was added dropwise to 74.8 ml of solution B.

15. Use of the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst according to claim 1 or the non-metal-doped NiFe LDH composite g-C3N4 electrocatalyst prepared by the preparation method according to any one of claims 2 to 14 as an electrocatalyst for a half-reaction oxygen evolution reaction.

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