Preparation of a honeycomb porous carbon / nickel-iron double hydroxide / foam nickel photoanode

Abstract

The application discloses a honeycomb porous carbon / nickel-iron double hydroxide / foamed nickel photoanode and a preparation method thereof. The nickel-iron double hydroxide is prepared by calcination with nickel nitrate, iron nitrate, ammonium fluoride and urea as raw materials. The photoanode is prepared by mixing and stirring different quality raw materials and calcination. The preparation method comprises the following steps: F1, grinding dried pomelo skin into powder, and obtaining honeycomb porous carbon through high-temperature carbonization; F2, drying the product after washing with ultrapure water and ethanol respectively, mixing, dissolving in water, and placing the high-pressure reaction kettle into a hydrothermal furnace for calcination at a certain temperature, and the collected product is the honeycomb porous carbon / nickel-iron double hydroxide / foamed nickel photoanode. The prepared photoanode has the advantages of large specific surface area, many active sites, fast photo-generated carrier separation and migration rate, high photocatalytic activity and high stability, thereby promoting the improvement of photoelectrocatalytic performance.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials and relates to layered nickel-iron double hydroxide photocatalysts and honeycomb porous carbon / nickel-iron double hydroxide / foam nickel photoanodes and their preparation methods. Background Technology

[0002] The energy shortage and environmental pollution caused by the continuous extraction and combustion of fossil fuels are becoming increasingly serious. Researchers are now searching for renewable and clean energy sources to replace non-renewable fossil fuels in order to meet growing energy demands and address related environmental problems. Hydrogen energy, with its numerous advantages such as being clean, efficient, safe, storable, and transportable, has received high attention from various countries. Green hydrogen is expected to become a new generation of energy carrier, and hydrogen production technology is a hot research topic for scientists.

[0003] Photoelectrochemical (PEC) water splitting for hydrogen production offers high flexibility, allowing for the rational selection of photoanodes and photocathodes. It can decompose water at room temperature, is simple to operate, and can directly separate and produce hydrogen gas with a lower overpotential required to produce the same amount of hydrogen. Photoelectrochemical water splitting is an attractive strategy for large-scale production of renewable hydrogen. Developing low-cost, highly active, and stable semiconductor photoelectrodes is crucial for achieving high-efficiency PEC water splitting. Although photoelectrocatalytic water splitting for hydrogen production is currently in the theoretical research stage, this method has potential practical applications. Perovskite oxides, as a large class of semiconductor metal oxides, are widely used in PEC water splitting for hydrogen production due to their abundant content, high (photo)electrochemical stability, compositional and structural flexibility, high electrocatalytic activity, and strong sunlight absorption capacity. Nickel-iron layered double hydroxide (NiFeLDH) possesses numerous advantages, including excellent visible light response, high thermochemical stability, easily tunable structure and morphology, non-toxicity, ease of preparation, low cost, moderate band gap, and large specific surface area. However, it also suffers from drawbacks such as high photogenerated electron-hole recombination rate and narrow visible light absorption range. Therefore, several optimization methods are employed: first, combining it with other catalysts to form heterojunctions, thereby improving electron-hole mobility; second, providing more reactive sites through morphology control (e.g., spherical, nanotube, hollow sphere, nanosheet); and third, increasing the specific surface area and improving the thermal stability of the material through structural design (supported, core-shell, eggshell structures). Nickel foam, due to its abundant and porous three-dimensional structure, has been used as an electrode in alkaline electrolyzers. In recent years, the HER (hydrogen evolution reaction) of NiFeLDH has attracted widespread attention, demonstrating that doping with a small amount of honeycomb porous carbon can enhance catalytic activity. In-situ growth and synthesis of foamed nickel photoanodes offers a fast reaction rate, enabling synthesis to be completed in a short time and improving production efficiency.

[0004] This patent, from the perspective of green, clean and efficient, proposes to design and prepare a series of NiFe LDH composites as novel water splitting photoelectrodes, conduct photoelectrochemical performance testing and reaction mechanism analysis, and provide new ideas for further developing efficient and inexpensive hydrogen production materials and promoting the industrialization of water splitting hydrogen production technology. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a honeycomb porous carbon / nickel-iron double hydroxide / foam nickel photoanode with a large specific surface area, numerous active sites, fast photogenerated carrier separation and migration rates, low photogenerated carrier overlap rate, redshift in the visible light absorption range, high photocatalytic activity, and high stability. Furthermore, it provides a preparation method that is simple to operate, has relatively low production costs, high product yield, and good reproducibility.

[0007] (II) Technical Solution (Honeycomb Porous Carbon / Nickel-Iron Double Hydroxide / Foam Nickel Photoanode)

[0008] F1: Take a certain amount of grapefruit peel pulp, cut it into small pieces, and dry it in a hot air drying oven for a period of time. After soaking the dried sample in potassium hydroxide solution, freeze-dry the resulting sample, and then grind the processed sample into powder.

[0009] F2: The powder is placed in a tube furnace filled with nitrogen gas, and the sample is carbonized at high temperature in a nitrogen environment. The black solid is ground into a uniform powder and washed with dilute nitric acid. After centrifugation, it is dried to obtain black powder.

[0010] F3: A certain mass of the above-mentioned black powder, nickel nitrate, ferric nitrate, ammonium fluoride, and urea mixture are thoroughly mixed in a certain proportion and placed into a high-pressure reactor. Then, nickel foam is placed in the solution, and the high-pressure reactor is placed in a hydrothermal furnace and calcined at a certain temperature to obtain black nickel foam. After drying, the black nickel foam is used to obtain a photoelectrode.

[0011] In a preferred embodiment, in F1, 20g of grapefruit peel pulp is cut into small pieces, and the dried grapefruit peel pulp should be soaked in 100mL of 1mol·L⁻¹ solution. -1 Soak in KOH solution for 12 hours.

[0012] In a preferred embodiment, in F2, 5g of the dried powder is placed in a crucible and placed in a tube furnace to be heated at 2°C·min. -1 The heating rate was increased to 300℃ and held at 300℃ for 60 min, followed by a temperature increase of 5℃·min. -1 Raise the temperature to 600℃ and hold for 30 minutes, then reduce the temperature to 5℃·min. -1The temperature was raised to 800°C and held for 60 minutes, then allowed to cool naturally to room temperature to obtain a black solid.

[0013] In a preferred embodiment, in F3, the method for preparing the photoanode includes the following steps:

[0014] (1) Weigh 0.9g of honeycomb porous carbon powder, 0.52g of nickel nitrate, 0.08g of ferric nitrate, 0.15g of ammonium fluoride and 0.6g of urea. Put the raw materials into a beaker in sequence and add 70mL of ultrapure water. Stir for 3h to make them fully mixed.

[0015] (2) Place the sample and nickel foam into a high-pressure reactor and calcine them in a hydrothermal furnace at a certain temperature and time.

[0016] In a preferred embodiment, step (2) includes the following steps:

[0017] (1) The sample was placed in a hydrothermal furnace for calcination, and then naturally cooled to room temperature after calcination at 200℃ for 24 hours.

[0018] (2) The mass fraction of honeycomb porous carbon in the nickel-iron double hydroxide doped with honeycomb porous carbon ranges from 1% to 10%, with a preferred mass fraction of 2%. The foamed nickel is selected from samples with a length of 4cm and a width of 2cm.

[0019] In a preferred embodiment, in F3, the black foam nickel obtained by naturally air-drying the foam nickel with tweezers is the honeycomb porous carbon / nickel-iron double hydroxide / foam nickel photoanode.

[0020] (iv) Beneficial effects

[0021] The beneficial effects of this invention are:

[0022] This invention provides a honeycomb porous carbon / nickel-iron double hydroxide / foamed nickel photoanode and its preparation method. The material in this invention possesses advantages such as moderate band gap, excellent thermal and chemical stability, environmental friendliness, absence of toxic components, and no secondary pollution, making it an ideal green catalyst. This material has a high specific surface area and abundant reactive sites, making it a good charge transport material. This invention is the first to propose using a NiFe LDH photocatalyst with a nickel-iron ratio of 9:1 and 2% honeycomb porous carbon / nickel-iron double hydroxide / foamed nickel photoanode to promote the separation and transport of photogenerated charge carriers in the photocatalytic reaction. Utilizing this type of material can improve the absorption rate of visible light, and by leveraging the large specific surface area of ​​the material, it increases the active sites for water splitting reactions, ultimately achieving the goal of improving the overall photocatalytic performance of the photoanode.

[0023] The preparation process of the present invention has the following advantages: the process is simple and easy to operate, the production cost is relatively low, the product yield is high, and the repeatability is good.

[0024] The photoanode prepared by the method of the present invention has the following advantages: large specific surface area, many active sites, fast separation and migration rate of photogenerated carriers, low overlap rate of photogenerated carriers, redshift of visible light absorption range, high photocatalytic activity, and high stability. Attached Figure Description

[0025] Figure 1 Flowchart for the preparation of nickel-iron double hydroxide photocatalyst and honeycomb porous carbon / nickel-iron double hydroxide / foam nickel photoanode for this patent;

[0026] Figure 2 The 0%-10% HLPC / Ni synthesized in Example 1 0.9 Fe 0.1 X-ray diffraction pattern of LDH;

[0027] Figure 3 Ni synthesized in Example 1 0.9 Fe 0.1 LDH and 2% HLPC / Ni 0.9 Fe 0.1 Scanning electron microscope image of LDH;

[0028] Figure 4 The 0%-10% HLPC / Ni synthesized in Example 1 0.9 Fe 0.1 Impedance diagram of LDH;

[0029] Figure 5 The 0%-10% HLPC / Ni synthesized in Example 1 0.9 Fe 0.1 Linear current-voltage (LSV) plot of LDH;

[0030] Figure 6 The 0%-10% HLPC / Ni synthesized in Example 1 0.9 Fe 0.1 LDH time-current graph.

[0031] Specific implementation plan (Ni) 0.9 Fe 0.1 LDH)

[0032] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below through specific embodiments.

[0033] This embodiment proposes a 2% honeycomb porous carbon / nickel-iron double hydroxide / foam nickel photoanode and its preparation method. The preparation method of this nanomaterial includes the following steps:

[0034] F1: Take a certain amount of grapefruit peel pulp, cut it into small pieces, and dry it in a hot air drying oven for a period of time. After soaking the dried sample in potassium hydroxide solution, freeze-dry the resulting sample, and then grind the processed sample into powder.

[0035] F2: The powder is placed in a tube furnace filled with nitrogen gas, and the sample is carbonized at high temperature in a nitrogen environment. The black solid is ground into a uniform powder and washed with dilute nitric acid. After centrifugation, it is dried to obtain black powder.

[0036] F3: A certain mass of the above-mentioned black powder, nickel nitrate, ferric nitrate, ammonium fluoride, and urea mixture are thoroughly mixed in a certain proportion and placed into a high-pressure reactor. Then, nickel foam is placed in the solution, and the high-pressure reactor is placed in a hydrothermal furnace and calcined at a certain temperature to obtain black nickel foam. After drying, the black nickel foam is used to obtain a photoelectrode.

[0037] Specifically, F1 includes the following steps:

[0038] Take 20g of grapefruit peel pulp and cut it into small pieces. The dried grapefruit peel pulp should be soaked in 100mL of 1mol·L⁻¹ solution. -1 Soak in KOH solution for 12 hours.

[0039] Step F2 includes the following steps:

[0040] The dried powder was placed in a crucible and then placed in a tube furnace to be heated at 2°C / min. -1 The heating rate was increased to 300℃ and held at 300℃ for 60 min, followed by a temperature increase of 5℃·min. -1 Raise the temperature to 600℃ and hold for 30 minutes, then reduce the temperature to 5℃·min. -1 The temperature was raised to 800°C and held for 60 minutes, then allowed to cool naturally to room temperature to obtain a black solid.

[0041] Step F3 includes the following steps:

[0042] F3.1: Weigh 0.9g of honeycomb porous carbon powder, 0.52g of nickel nitrate, 0.08g of ferric nitrate, 0.15g of ammonium fluoride and 0.6g of urea. Put the raw materials into a beaker in sequence and add 70mL of ultrapure water. Stir for 3 hours to mix them thoroughly.

[0043] F3.2: Place the sample and nickel foam into a high-pressure reactor, calcine at 200°C for 24 hours in a hydrothermal furnace, and then allow it to cool naturally to room temperature.

[0044] F3.3: Remove the supernatant and collect the precipitate; place the precipitate in a drying oven and dry at 60℃ for 24h to obtain a honeycomb porous carbon / nickel-iron double hydroxide photocatalyst. The black foamed nickel obtained by naturally air-drying the foamed nickel with tweezers is the honeycomb porous carbon / nickel-iron double hydroxide / foamed nickel photoanode.

[0045] In step S3.2, the mass fraction of the honeycomb porous carbon in the honeycomb porous carbon-doped nickel-iron double hydroxide ranges from 1% to 10%, with a preferred mass fraction of 2%, and the foamed nickel is selected from samples with a length of 4 cm and a width of 2 cm.

[0046] This invention presents a hydrothermal method for preparing a honeycomb-shaped porous carbon / nickel-iron double hydroxide / foamed nickel photoanode. Compared with undoped nickel hydroxide, it exhibits a larger specific surface area, more active sites, faster photogenerated carrier separation and migration rates, higher photogenerated carrier overlap rate, a redshift in the low visible light absorption range, higher photocatalytic activity, and higher stability, thereby improving photocatalytic efficiency. The method of this invention is simple and easy to operate, has relatively low production costs, high product yield, and good reproducibility, demonstrating potential for practical application.

[0047] The present invention is further illustrated by the following embodiments.

[0048] Example 1

[0049] Take 20g of grapefruit peel pulp, cut it into small pieces, and dry it in a 60℃ hot air drying oven for 24 hours. Then, soak the dried sample in 100mL of 1mol·L⁻¹ solution. -1 After soaking in KOH solution for 12 hours, the obtained sample was freeze-dried for 48 hours. Then, the treated sample was ground uniformly into powder, placed in a crucible, and then placed in a tube furnace. Nitrogen gas was introduced into the tube furnace to carbonize the sample at high temperature in a nitrogen atmosphere at 2℃·min. -1 The heating rate was increased to 300℃ and held at 300℃ for 60 min, followed by a temperature increase of 5℃·min. -1 Raise the temperature to 600℃ and hold for 30 minutes, then reduce the temperature to 5℃·min. -1 The temperature was raised to 800℃ and held for 60 minutes, then allowed to cool naturally to room temperature. The resulting black solid was then ground into a uniform powder and mixed with 50 mL of 1 mol·L⁻¹ solution. -1 The sample was washed once with HNO3 to remove KOH and other inorganic impurities. The sample was then subjected to surface oxidation treatment and washed with ultrapure water until neutral. After centrifugation, the sample was dried, and the resulting black powder was honeycomb porous carbon.

[0050] Prepare beakers and a high-pressure reactor. Wash the beakers with water and alcohol and dry them in a drying oven. Soak the reactor in nitric acid for 10 minutes, then wash it with water and alcohol and dry it in a drying oven. Weigh 0.9 mg of honeycomb porous carbon powder, 0.52 g of nickel nitrate, 0.08 g of ferric nitrate, 0.15 g of NH4F, and 0.6 g of urea using an electronic balance, and use 70 mL of ultrapure water as the solvent. Add the raw materials sequentially to a 100 mL beaker, then add 70 mL of ultrapure water and stir for 3 hours to ensure thorough mixing. Place the sample into the dried 100 mL high-pressure reactor, then tilt a 4 cm long and 2 cm wide piece of foamed nickel into the solution. Calcinate in a hydrothermal furnace at 200 °C for 24 hours. The resulting black foamed nickel is 1% HLPC / Ni by mass. 0.9 Fe 0.1 LDH foam nickel photoelectrode.

[0051] Example 2

[0052] Take 25g of grapefruit peel pulp, cut it into small pieces, and dry it in a 60℃ hot air drying oven for 36 hours. Then, soak the dried sample in 50mL of 1mol·L⁻¹ solution. -1 After soaking in KOH solution for 18 hours, the obtained sample was freeze-dried for 60 hours. Then, the treated sample was ground uniformly into powder, placed in a crucible, and then placed in a tube furnace. Nitrogen gas was introduced into the tube furnace to carbonize the sample at high temperature in a nitrogen atmosphere at 2℃·min. -1 The heating rate was increased to 300℃ and held at 300℃ for 60 min, followed by a temperature increase of 5℃·min. -1 Raise the temperature to 600℃ and hold for 30 minutes, then reduce the temperature to 5℃·min. -1 The temperature was raised to 800℃ and held for 60 minutes, then allowed to cool naturally to room temperature. The resulting black solid was then ground into a uniform powder and mixed with 100 mL of 1 mol·L⁻¹ solution. -1 The sample was washed twice with HNO3 to remove KOH and other inorganic impurities. The sample was then subjected to surface oxidation treatment and washed with ultrapure water until neutral. After centrifugation, the sample was dried, and the resulting black powder was honeycomb porous carbon.

[0053] Prepare beakers and a high-pressure reactor. Wash the beakers with water and alcohol and dry them in a drying oven. Soak the reactor in nitric acid for 10 minutes, then wash it with water and alcohol and dry it in a drying oven. Weigh 1.8 mg of honeycomb porous carbon powder, 0.52 g of nickel nitrate, 0.08 g of ferric nitrate, 0.15 g of NH4F, and 0.6 g of urea using an electronic balance, and use 70 mL of ultrapure water as the solvent. Add the raw materials sequentially to a 100 mL beaker, then add 70 mL of ultrapure water and stir for 3 hours to ensure thorough mixing. Place the sample into the dried 100 mL high-pressure reactor, then tilt a 4 cm long and 2 cm wide piece of foamed nickel into the solution. Calcinate in a hydrothermal furnace at 200 °C for 24 hours. The final black foamed nickel is 2% HLPC / Ni by mass. 0.9 Fe 0.1 LDH foam nickel photoelectrode.

[0054] Example 3

[0055] Take 30g of grapefruit peel pulp, cut it into small pieces, and dry it in a 60℃ hot air drying oven for 48 hours. Then, soak the dried sample in 150mL of 1mol·L⁻¹ solution. -1 After soaking in KOH solution for 24 hours, the obtained sample was freeze-dried for 72 hours. Then, the treated sample was ground uniformly into powder, placed in a crucible, and then placed in a tube furnace. Nitrogen gas was introduced into the tube furnace to carbonize the sample at high temperature in a nitrogen atmosphere at 2℃·min. -1 The heating rate was increased to 300℃ and held at 300℃ for 60 min, followed by a temperature increase of 5℃·min. -1 Raise the temperature to 600℃ and hold for 30 minutes, then reduce the temperature to 5℃·min. -1 The temperature was raised to 800℃ and held for 60 minutes, then allowed to cool naturally to room temperature. The resulting black solid was then ground into a uniform powder and mixed with 150 mL of 1 mol·L⁻¹ solution. -1 The sample was washed three times with HNO3 to remove KOH and other inorganic impurities. The sample was then subjected to surface oxidation treatment and washed with ultrapure water until neutral. After centrifugation, the sample was dried, and the resulting black powder was honeycomb porous carbon.

[0056] Prepare beakers and a high-pressure reactor. Wash the beakers with water and alcohol and dry them in a drying oven. Soak the reactor in nitric acid for 10 minutes, then wash it with water and alcohol and dry it in a drying oven. Weigh 4.5 mg of honeycomb porous carbon powder, 0.52 g of nickel nitrate, 0.08 g of ferric nitrate, 0.15 g of NH4F, and 0.6 g of urea using an electronic balance, and use 70 mL of ultrapure water as the solvent. Add the raw materials sequentially to a 100 mL beaker, then add 70 mL of ultrapure water and stir for 3 hours to ensure thorough mixing. Place the sample into the dried 100 mL high-pressure reactor, then tilt a 4 cm long and 2 cm wide piece of foamed nickel into the solution. Calcinate in a hydrothermal furnace at 200 °C for 24 hours. The resulting black foamed nickel is 5% HLPC / Ni by mass. 0.9 Fe 0.1 LDH foam nickel photoelectrode.

Claims

1. A method for preparing a honeycomb porous carbon / nickel-iron double hydroxide / foam nickel photoanode, characterized in that, The method comprises the steps of: F1: A certain amount of pomelo peel is cut into small pieces and placed in a hot air drying oven for drying for a period of time. The dried sample is soaked in a potassium hydroxide solution, and then the obtained sample is freeze-dried. Then, the treated sample is ground uniformly and made into a powder; F2: The powder is placed in a tube furnace with nitrogen, and the sample is carbonized at high temperature in a nitrogen environment. The black solid is ground into a uniform powder and washed with dilute nitric acid. After centrifugal separation, the black powder is obtained after drying treatment; F3: A mixture of a certain mass of the above black powder, nickel nitrate, iron nitrate, ammonium fluoride and urea is mixed uniformly at a certain proportion and placed in a high-pressure reaction kettle. Then, the nickel foam is placed in the solution, and the high-pressure reaction kettle is placed in a hydrothermal furnace and calcined at a certain temperature to obtain black nickel foam. After drying, the photoelectrode is obtained.

2. The production method according to claim 1, characterized by, In F1, 20 g of pomelo peel was cut into small pieces, and the dried pomelo peel was soaked in 100 mL of 1 mol·L -1 KOH solution for 12 h.

3. The preparation method according to claim 1, characterized in that, In F2, the dried powder was put into a crucible and was put into a tube furnace to increase to 300°C at a temperature increasing rate of 2°C min -1 and was kept at 300°C for 60 min, immediately after which the temperature was increased to 600°C at a temperature increasing rate of 5°C min -1 and was kept at 600°C for 30 min, and finally was increased to 800°C at a temperature increasing rate of 5°C min -1 and was kept at 800°C for 60 min, and after that, it was naturally cooled to room temperature to obtain a black solid.

4. The method of claim 1, wherein, In F3, the preparation method of the photoanode comprises the following steps: (1) 0.9 g of honeycomb-like porous carbon powder, 0.52 g of nickel nitrate, 0.08 g of iron nitrate, 0.15 g of ammonium fluoride and 0.6 g of urea are weighed, and the raw materials are placed in a beaker in turn and then 70 mL of ultrapure water is added and stirred for 3 h to make them mix well; (2) The sample and the nickel foam are placed in a high-pressure reaction kettle, and calcined at 200°C in a hydrothermal furnace for 24 h, and then naturally cooled to room temperature; (3) The mass fraction of honeycomb-like porous carbon in the honeycomb-like porous carbon-doped nickel-iron double hydroxide ranges from 1% to 10%, and the nickel foam is selected to be a sample with a length of 4 cm and a width of 2 cm.

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