CN113215594B - Nickel-iron hydroxide/nickel-iron alloy loaded wood-based electrocatalyst, preparation method thereof and hydrogen production catalyst by electrolyzing water - Google Patents

Nickel-iron hydroxide/nickel-iron alloy loaded wood-based electrocatalyst, preparation method thereof and hydrogen production catalyst by electrolyzing water Download PDF

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CN113215594B
CN113215594B CN202110373756.0A CN202110373756A CN113215594B CN 113215594 B CN113215594 B CN 113215594B CN 202110373756 A CN202110373756 A CN 202110373756A CN 113215594 B CN113215594 B CN 113215594B
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iron
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iron alloy
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CN113215594A (en
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卿彦
吴义强
许瀚
宋美玲
罗莎
田翠花
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Central South University of Forestry and Technology
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
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    • C25B1/04—Hydrogen or oxygen by electrolysis of water
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Abstract

The invention discloses a wood-based electrocatalyst loaded with nickel-iron hydroxide/nickel-iron alloy, which comprises a charcoal skeleton with a three-dimensional porous structure and an active substance loaded on the charcoal skeleton, wherein the active substance comprises a nickel-iron hydroxide/nickel-iron alloy heterojunction taking the nickel-iron alloy as a bottom layer and the nickel-iron hydroxide as a surface layer. The invention also provides a preparation method of the wood-based electrocatalyst loaded with the nickel-iron hydroxide/nickel-iron alloy and a catalyst for hydrogen production by water electrolysis. The nickel-iron hydroxide/nickel-iron alloy loaded wood-based electrocatalyst has the advantages of high catalytic efficiency, good stability, simple process and the like.

Description

Nickel-iron hydroxide/nickel-iron alloy loaded wood-based electrocatalyst, preparation method thereof and catalyst for hydrogen production by electrolyzing water
Technical Field
The invention belongs to the field of catalysts, and particularly relates to a non-noble metal electrocatalyst, a preparation method thereof and a catalyst for hydrogen production by water electrolysis.
Background
With the rapid development of society, the traditional fossil fuel resources are increasingly exhausted. Under the circumstances that the human energy demand is more and the environment situation is not optimistic, the development of green renewable energy sources is urgent. Compared with solar energy, wind energy and the like, the hydrogen energy has the advantages of stable power generation, high combustion heat value and no pollution, and has wide application prospect. The hydrogen production by electrolyzing water is regarded as the most promising hydrogen production mode due to the advantages of high yield, high product purity and the like.
The hydrogen production by water electrolysis comprises two half reactions of HER and OER, wherein the hydrogen evolution reaction is a two-electron reaction, the oxygen evolution reaction is a four-electron reaction, a higher overpotential is required to overcome a reaction energy barrier, and the reaction is the rate-determining step of the water electrolysis reaction. Noble metal oxide (RuO) 2 、IrO 2 ) Has excellent OER catalytic performance, but has rare earth reserves and high priceAnd the like limit the large-scale application thereof, so that the development of an efficient and economical OER catalyst is required. Currently, a large number of researchers have been investing in the earth's abundant transition metals to develop inexpensive and effective OER catalysts and to prepare a series of OER catalysts having catalytic activity comparable to noble metal oxides. In the preparation process of the transition metal-based catalyst, compounding an active substance with a conductive substrate (graphene, carbon fiber, carbon nanotube and the like) is a conventional means for improving the catalytic activity of the active substance, but the simple compounding still has the problems of uneven dispersion, large accumulation and the like of the active substance, and the general conductive substrate is derived from petrochemical products and cannot be regenerated.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects and defects mentioned in the background technology, and provide a nickel-iron hydroxide/nickel-iron alloy loaded wood-based electrocatalyst with high catalytic efficiency, good stability and simple process, a preparation method thereof and a catalyst for hydrogen production by electrolyzing water. In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a wood-based electrocatalyst supporting a nickel-iron hydroxide/nickel-iron alloy, the wood-based electrocatalyst includes a charcoal skeleton having a three-dimensional porous structure and an active substance supported on the charcoal skeleton, the active substance including a nickel-iron hydroxide/nickel-iron alloy heterojunction having a nickel-iron alloy as a bottom layer and a nickel-iron hydroxide as a surface layer.
The wood-based electrocatalyst of the invention firstly generates a layer of uniform nickel-iron alloy in pores and surfaces of wood, and then generates nickel-iron hydroxide by taking the nickel-iron alloy as a growing point, the intrinsic activity of the catalyst is directly influenced by the electronic structure of the catalyst, a heterostructure is constructed, electrons are redistributed on an interface due to mutual strong electronic action of the heterostructure, an optimal electronic structure is obtained, reaction activation energy is reduced, and thus reaction is accelerated, and the composite catalyst has better catalytic activity.
Among the above wood-based electrocatalysts, it is preferable that the specific surface area of the wood-based electrocatalyst is from 100 to 400m 2 (ii)/g, the size of the active material in the wood-based electrocatalyst is50-200nm, and the loading rate (mass loading rate) of the active substance in the wood-based electrocatalyst is 0.2-10%. The catalyst has the advantages of small active substance particle size, large specific surface area and excellent catalytic performance.
As a general technical concept, the present invention also provides a method for preparing a nickel iron hydroxide/nickel iron alloy-loaded wood-based electrocatalyst, comprising the steps of:
(1) The wood chips (natural wood) are placed in a nickel-iron metal salt solution for impregnation treatment, and the wood chips are taken out and dried to obtain the wood chips loaded with nickel-iron ions;
(2) Calcining the wood chips loaded with nickel-iron ions obtained in the step (1) at high temperature in an inert atmosphere (such as nitrogen) to obtain charcoal loaded with nickel-iron alloy;
(3) And (3) placing the charcoal loaded with the nickel-iron alloy obtained in the step (2) into a mixed solution of nickel-iron metal salt and urea for hydrothermal treatment to obtain the wood-based electrocatalyst loaded with the nickel-iron hydroxide/nickel-iron alloy.
In the above preparation method, preferably, the ferronickel metal salt solution is a mixed solution of nickel salt and iron salt; the nickel salt comprises at least one of nickel nitrate, nickel chloride and nickel acetate; the ferric salt comprises at least one of ferric nitrate, ferric chloride and ferric acetate; and in the nickel-iron metal salt solution, the molar ratio of nickel to iron is controlled to be (0.1-9): 1, more preferably, the molar ratio of nickel to iron is controlled to be (0.67-0.7): 1. the nickel-iron alloy synthesized by different nickel-iron molar ratios has different electronic structures, and the proportion is controlled to be the molar ratio, so that the nickel-iron alloy with the optimal electronic structure can be synthesized, and the catalyst has the optimal intrinsic activity.
In the above preparation method, preferably, during the impregnation treatment, the mass ratio of the wood chips to the nickel-iron metal salt (i.e. the total mass of the nickel salt and the iron salt) in the nickel-iron metal salt solution is controlled to be (0.1-10): 1 (more preferably 0.125. The higher mass of the nickel-iron metal salt results in larger alloy particle size and agglomeration on the surface and inside of the wood, resulting in uneven distribution. When the metal salt is proper in quality, the metal salt is just uniformly loaded on the surface and the inside of the wood, and the generated alloy particles are smaller. Therefore, the particle size of the generated nickel-iron alloy can be finer and the alloy particles can be uniformly loaded on the charcoal skeleton by adjusting the mass ratio of the wood chips to the nickel-iron metal salt.
In the above preparation method, preferably, the dipping treatment is vacuum dipping treatment, the vacuum dipping treatment is carried out in a vacuum drying oven, and the dipping temperature is kept at 10-150 ℃ and the dipping time is 1-24h; the drying temperature is controlled to be 10-120 ℃ during drying, and the drying time is 1-24h.
In the above preparation method, preferably, the high-temperature calcination is carried out in a tube furnace, and the calcination temperature is maintained at 600 to 1000 ℃ (more preferably 900 ℃), the temperature rise rate is 5 to 10 ℃/min, and the calcination time is 1 to 3h (more preferably 2 h). The calcination temperature is too low, the calcination time is short, the graphitization degree of the carbon material is not enough, the conductivity of the catalyst is influenced, and the activity of the catalyst is finally influenced; the calcination temperature is too high, the calcination time is long, and the size of the synthesized nickel-iron alloy is larger, so that the catalytic reaction active sites can be reduced, and the catalytic activity is influenced.
In the above preparation method, preferably, in the mixed solution of the nickel-iron metal salt and urea, the molar ratio of the nickel-iron metal salt to the urea is (0.2-5): 1, and the molar ratio of nickel to iron in the nickel-iron metal salt is (0.1-9): 1, more preferably, the molar ratio of nickel to iron is controlled to be (0.67-0.7): 1. urea decomposes to produce ammonium ions and carbonate ions in the reaction process, the ammonium ions provide an alkaline environment to deposit ferronickel to generate hydroxide, and the carbonate ions are used as intercalation anions. The degree of alkalinity of the reaction environment will affect the rate of hydroxide formation and further the size, thickness of the hydroxide formed, and carbonate ion will affect the hydroxide thickness. The molar ratio of nickel iron in the nickel iron hydroxide nanosheets is different, and the obtained substance has different electronic structures which influence the intrinsic activity. Also, the ferronickel hydroxide thickness obtained from different molar ratios of ferronickel is also different. The dosage of urea in the proportional relation is optimized to ensure that the synthesized nickel iron hydroxide nanosheet has a larger size and a thinner thickness. The molar ratio of nickel to iron is controlled, and the obtained nickel-iron hydroxide nanosheet has the advantages of being thinner, higher in intrinsic activity and the like.
In the above preparation method, preferably, the mass ratio of the nickel-iron metal salt (i.e. the total mass of the nickel salt and the iron salt) in the mixed solution of the nickel-iron alloy-loaded charcoal and the nickel-iron metal salt and urea is controlled to be (0.1-10): 1. the charcoal has limited pores and defects, the more metal salts generate ferronickel hydroxide in hydrothermal process, the more hydroxide can grow on the pores and defects firmly and uniformly, and the excessive hydroxide is stacked on the hydroxide at the bottom part disorderly. Therefore, the nickel-iron hydroxide nanosheets can be uniformly and firmly anchored on the charcoal skeleton by regulating the mass ratio of the charcoal loaded with the nickel-iron alloy to the nickel-iron metal salt.
In the preparation method, preferably, the hydrothermal treatment is carried out in a hydrothermal reaction kettle, the hydrothermal reaction temperature is controlled to be 100-220 ℃, and the hydrothermal reaction time is 1-24h.
In the above preparation method, the wood chips are preferably any one of coniferous wood or broadleaf wood such as poplar, balsa wood, pine wood, fir wood, birch wood and basswood.
The principle of the invention is as follows: the unique structure of the natural wood chip with the three-dimensional porous structure and the vertical orientation micro-channels is perfectly maintained after impregnation, carbonization (namely high-temperature calcination) and hydrothermal treatment. During vacuum impregnation, nickel-iron metal ions deeply penetrate into pores of the wood chips, and rich active functional groups are arranged on wood cell walls, so that the metal ions can be uniformly adsorbed, natural wood chips are converted into charcoal during high-temperature carbonization, nickel-iron metal ions are reduced to generate nano nickel-iron alloy particles, the generated nano nickel-iron alloy particles are uniformly distributed in wood microchannels and the surfaces, and the generated nano nickel-iron alloy particles are uniformly and firmly embedded into a charcoal framework. Because the nano nickel-iron alloy particles are uniformly distributed in pores and surfaces of the wood, the nano nickel-iron alloy particles have anchoring points for uniform and firm growth of the hydroxide nanosheets, and the nickel-iron hydroxide nanosheets can also grow orderly due to inhibition of a microchannel structure with regularly arranged wood. Therefore, the nickel-iron hydroxide nanosheets can be uniformly, firmly and orderly grown on the charcoal skeleton loaded with the nickel-iron alloy in the hydrothermal process, and finally the nickel-iron hydroxide/nickel-iron alloy loaded wood-based electrocatalyst is obtained.
The wood-based electrocatalyst loaded with the nickel-iron hydroxide/nickel-iron alloy takes carbonized wood with a three-dimensional porous structure and vertically oriented microchannels as a framework, and nickel-iron hydroxide/nickel-iron alloy heterojunctions are uniformly and firmly loaded on the carbonized wood, so that the synthesized electrocatalyst is endowed with rich pores, large surface area, heterostructure, a large number of exposed active sites and strong structural stability. The optimized structure has the following advantages: 1) The three-dimensional porous structure and the vertical orientation micro-channel derived from the natural wood chips are perfectly maintained after a series of treatments, and the synthesized catalyst is endowed with a unique three-dimensional porous structure, so that the electrolyte permeation is faster, the gas release is faster, and the mass transfer of reaction intermediate products is faster. 2) The carbonized wood skeleton has excellent conductivity, and the nickel-iron alloy is doped to ensure that the conductivity of the catalyst skeleton is more excellent and the electron transmission is accelerated. 3) The robust charcoal skeleton gives the catalyst excellent overall stability. 4) The active substance is uniformly and firmly loaded on the three-dimensional porous charcoal skeleton, so that the catalyst has larger specific surface area and more exposed active sites. 5) The formation of the nickel-iron hydroxide/nickel-iron alloy heterojunction optimizes the electronic structure of the catalyst, so that the catalyst has better intrinsic activity.
As a general technical concept, the invention also provides a catalyst for hydrogen production by water electrolysis, which comprises a HER catalyst and an OER catalyst, wherein the OER catalyst is the above-mentioned nickel iron hydroxide/nickel iron alloy supported wood-based electrocatalyst. The HER catalyst is a wood-based electrocatalyst loaded with molybdenum carbide, and the preparation method comprises the following steps:
(1) The wood chips are placed in a molybdenum salt solution for impregnation treatment, and then taken out and dried to obtain the wood chips loaded with molybdenum salt; the molybdenum salt in the molybdenum salt solution comprises at least one of ammonium molybdate and sodium molybdate, and the concentration of molybdenum in the molybdenum salt solution is controlled to be 0.1-0.9mol/L.
(2) And (2) calcining the wood chips loaded with the molybdenum salt obtained in the step (1) in an inert atmosphere, and cooling to obtain the wood-based electrocatalyst loaded with molybdenum carbide. The calcination is carried out in a tubular furnace, the calcination temperature is controlled to be 600-1000 ℃, the heating rate is 5-10 ℃/min, and the heat preservation time is 1-3h.
The preparation principle of the wood-based electrocatalyst loaded with molybdenum carbide is as follows: the unique structure of the natural wood chip with the three-dimensional porous structure is completely preserved after the natural wood chip is treated by vacuum impregnation and high-temperature carbonization (namely calcination). During vacuum impregnation, abundant pores in the wood can adsorb the molybdenum salt solution, and the molybdenum salt is converted into molybdenum trioxide to be loaded in the pore structure of the wood. During high-temperature calcination, the wood chips are converted into charcoal and generate a large amount of cracked gas, and the wood chips further undergo a reduction reaction with molybdenum trioxide to generate beta-type molybdenum carbide, and finally the HER electrocatalyst with molybdenum carbide uniformly, directionally and firmly loaded on the three-dimensional porous charcoal is formed. The method fully utilizes the three-dimensional hierarchical porous structure of the natural wood, provides a reaction platform for uniform adsorption of molybdenum salt and subsequent growth of molybdenum carbide, and provides a foundation for firm combination, formation of a large number of exposed active sites and limitation of the size of molybdenum carbide particles, thereby preparing the catalyst with excellent catalytic activity and stability. In addition, the invention utilizes the pyrolysis gas released in the carbonization process of the natural wood as the carbon source, does not need to add any carbon-containing gas to provide the carbon source, greatly simplifies the preparation process, and only needs two steps of dipping and carbonization in the whole preparation process.
Compared with the prior art, the invention has the advantages that:
1. the wood-based electrocatalyst loaded with the nickel-iron hydroxide/nickel-iron alloy comprises a charcoal skeleton with rich multi-layer pores, directional mass transfer channels and a three-dimensional self-supporting structure, and a nickel-iron hydroxide/nickel-iron alloy heterojunction is uniformly and firmly loaded in the charcoal skeleton, so that the intrinsic activity of an active substance is further enhanced by forming the heterojunction. The above two phases are combined, so that the prepared catalyst has excellent OER electrocatalytic activity and stability. The test results show that at 50mA.cm -2 At current density, the overpotential was only 212mV at the lowest, and the voltage increased by only about 4.0% after 100h stability testing (chronopotentiometry).
2. The preparation method provided by the invention takes the natural wood chips with the three-dimensional porous structure as the raw material, and the natural wood chips are subjected to impregnation treatment, then the product can be obtained by utilizing multiple effects of the natural wood chips and further performing one-step calcination carbonization and hydrothermal reaction deposition, the whole preparation process is ingenious and simple in design, the raw material is derived from renewable biomass materials, and the whole preparation process has the advantages of easiness in obtaining the raw material, low cost, low energy consumption, simple preparation process and the like, and is particularly suitable for industrial mass production and application.
3. The invention converts cheap and renewable biological polymers into the wood-based electrocatalytic material with high added value by a simple method, and provides green and wider opportunities for the utilization of the biomass material.
4. The catalyst for hydrogen production by electrolyzing water has the advantages of high catalytic efficiency, simple process and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is an SEM image of the nickel iron hydroxide/nickel iron alloy supported wood-based electrocatalyst of example 1.
Figure 2 is a linear sweep voltammogram of the nickel iron hydroxide/nickel iron alloy supported wood based electrocatalyst of example 1.
Fig. 3 is a stability test chart of the wood-based electrocatalyst supporting nickel iron hydroxide/nickel iron alloy in example 1.
Detailed Description
In order to facilitate an understanding of the invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
Example 1:
a wood-based electrocatalyst loaded with nickel-iron hydroxide/nickel-iron alloy uses carbonized wood with three-dimensional hierarchical porous structure and vertically oriented channels as a charcoal skeleton, and nickel-iron hydroxide/nickel-iron alloy heterojunction (nickel-iron alloy is used as a bottom layer and nickel-iron hydroxide is used as a surface layer) is uniformly and firmly loaded on the charcoal skeleton. The specific surface area of the wood-based electrocatalyst is 100-200m 2 The active substance size is 100-150nm, and the active substance loading rate is 0.2-10%.
The preparation method of the wood-based electrocatalyst loading the nickel-iron hydroxide/nickel-iron alloy comprises the following steps:
(1) A large piece of poplar was cut out to have a size of 2.0 cm. Times.0.8 cm. Times.1 mm (length. Times.width. Times.height), and weighed to have a mass of 0.05g.
(2) Adding the wood chips obtained in the step (1) into a nickel-iron nitrate solution (0.400 g of nickel nitrate hexahydrate and ferric nitrate nonahydrate, and the molar ratio of nickel ions to iron ions in the solution is 0.67 to 1), placing the wood chips into a vacuum drying oven for vacuum impregnation, and keeping the impregnation temperature at 100 ℃ and the impregnation time at 12h.
(3) And (3) placing the wood chips impregnated with the nickel iron ions in the step (2) into a common drying oven, wherein the drying temperature is 100 ℃, and the drying time is 5 hours.
(4) And (4) placing the dried wood chips in the step (3) into a tubular furnace, heating to 900 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, and preserving heat for 2h. And naturally cooling to room temperature to obtain the charcoal loaded with the nickel-iron alloy.
(5) Putting the charcoal loaded with the nickel-iron alloy in the step (4) into a mixed solution of nickel-iron nitrate and urea (wherein the total amount of nickel nitrate hexahydrate and ferric nitrate nonahydrate is 0.400g, the molar ratio of nickel ions to iron ions in the solution is 0.67 and the amount of urea is 0.200 g), then moving the charcoal into a reaction kettle, heating the charcoal in a common drying oven, and keeping the hydrothermal temperature at 120 ℃ for 12h. Then naturally cooled to room temperature, and the wood-based electrocatalyst NiFe-LDHs @ NiFe/CW in the embodiment is obtained.
The morphology of the wood-based electrocatalyst prepared in this example was observed using a high-resolution scanning electron microscope. As a result, as shown in fig. 1, it is understood that a nickel-iron hydroxide/nickel-iron alloy heterojunction is uniformly supported on a charcoal skeleton having a three-dimensional network structure.
The wood-based electrocatalyst in the embodiment is directly used as a working electrode, and is soaked in a 1.0M KOH solution for oxygen evolution linear sweep voltammetry test, so that the electrocatalytic activity of the oxygen evolution reaction is represented. As shown in fig. 2, at 50ma -2 Under the current density, the overpotential of the wood-based catalyst is only 212mV, and the catalytic activity of the wood-based catalyst is far better than that of a commercial noble metal oxide (RuO) 2 (319 mV)) OER catalyst. In addition, the wood-based electrocatalyst in this example was directly used as a working electrode, and immersed in a 1.0M KOH solution for 100h of chronopotentiometric test to determine its long-term stability. As shown in fig. 3, the voltage increased only about 4.0% after 100h stability test and the catalyst showed excellent stability.
Example 2:
the wood-based electrocatalyst with supported nickel-iron hydroxide/nickel-iron alloy has carbonized wood with three-dimensional layered porous structure and vertically oriented channels as charcoal skeleton with homogeneously and firmly supported nickel-iron hydroxide/nickel-iron alloy heterojunction.
The preparation method of the wood-based electrocatalyst loading the nickel-iron hydroxide/nickel-iron alloy comprises the following steps:
(1) A large piece of poplar was cut to a size of 2.0 cm. Times.0.8 cm. Times.1 mm (length. Times.width. Times.height), and weighed to have a mass of 0.05g.
(2) Adding the wood chips obtained in the step (1) into a nickel-iron nitrate solution (0.400 g of nickel nitrate hexahydrate and ferric nitrate nonahydrate, and the molar ratio of nickel ions to iron ions in the solution is 1.25), placing the wood chips into a vacuum drying oven for vacuum impregnation, and keeping the impregnation temperature at 100 ℃ and the impregnation time at 12h.
(3) And (3) putting the wood chips impregnated with the nickel iron ions in the step (2) into a common drying oven, wherein the drying temperature is 100 ℃, and the drying time is 5 hours.
(4) And (4) placing the dried wood chips in the step (3) into a tubular furnace, heating to 900 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, and preserving heat for 2h. And naturally cooling to room temperature to obtain the charcoal loaded with the nickel-iron alloy.
(5) Putting the charcoal loaded with the nickel-iron alloy in the step (4) into a mixed solution of nickel-iron nitrate and urea (wherein the total amount of nickel nitrate hexahydrate and ferric nitrate nonahydrate is 0.400g, the molar ratio of nickel ions to iron ions in the solution is 0.67 and the amount of urea is 0.200 g), then moving the charcoal into a reaction kettle, heating the charcoal in a common drying oven, and keeping the hydrothermal temperature at 120 ℃ for 12h. Then naturally cooled to room temperature, thus obtaining the wood-based electrocatalyst NiFe-LDHs @ NiFe/CW in the embodiment.
The wood-based electrocatalyst in the embodiment is directly used as a working electrode, and is soaked in a 1.0M KOH solution for oxygen evolution linear sweep voltammetry test, so that the electrocatalytic activity of the oxygen evolution reaction is represented. At 50mA.cm -2 The overpotential of the wood-based catalyst is only 280mV at the current density, and the catalytic activity of the wood-based catalyst is far superior to that of the commercial noble metal oxide OER catalyst.
Example 3:
the wood-based electrocatalyst of supported nickel-iron hydroxide/nickel-iron alloy has carbonized wood with three-dimensional hierarchical porous structure and vertically oriented channels as charcoal skeleton with homogeneously and firmly supported nickel-iron hydroxide/nickel-iron alloy heterojunction.
The preparation method of the wood-based electrocatalyst loading the nickel-iron hydroxide/nickel-iron alloy comprises the following steps:
(1) A large piece of poplar was cut out to have a size of 2.0 cm. Times.0.8 cm. Times.1 mm (length. Times.width. Times.height), and weighed to have a mass of 0.05g.
(2) Adding the wood chips obtained in the step (1) into a nickel-iron nitrate solution (0.400 g of nickel nitrate hexahydrate and ferric nitrate nonahydrate, and the molar ratio of nickel ions to iron ions in the solution is 0.5, 1), placing the wood chips into a vacuum drying oven for vacuum impregnation, and keeping the impregnation temperature at 100 ℃ and the impregnation time at 12h.
(3) And (3) putting the wood chips impregnated with the nickel iron ions in the step (2) into a common drying oven, wherein the drying temperature is 100 ℃, and the drying time is 5 hours.
(4) And (4) placing the dried wood chips obtained in the step (3) into a tube furnace, heating to 900 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, and preserving heat for 2h. And naturally cooling to room temperature to obtain the charcoal loaded with the nickel-iron alloy.
(5) Putting the charcoal loaded with the nickel-iron alloy in the step (4) into a mixed solution of nickel-iron nitrate and urea (wherein the total amount of nickel nitrate hexahydrate and ferric nitrate nonahydrate is 0.400g, the molar ratio of nickel ions to iron ions in the solution is 0.67 and the amount of urea is 0.200 g), then moving the charcoal into a reaction kettle, heating the charcoal in a common drying oven, and keeping the hydrothermal temperature at 120 ℃ for 12h. Then naturally cooled to room temperature, and the wood-based electrocatalyst NiFe-LDHs @ NiFe/CW in the embodiment is obtained.
The wood-based electrocatalyst in the embodiment is directly used as a working electrode, and is soaked in a 1.0M KOH solution for oxygen evolution linear sweep voltammetry test, so that the electrocatalytic activity of the oxygen evolution reaction is represented. At 50mA.cm -2 The overpotential of the wood-based catalyst is only 260mV at the current density, and the catalytic activity of the wood-based catalyst is far better than that of a commercial noble metal oxide OER catalyst.
Example 4:
the wood-based electrocatalyst with supported nickel-iron hydroxide/nickel-iron alloy has carbonized wood with three-dimensional layered porous structure and vertically oriented channels as charcoal skeleton with homogeneously and firmly supported nickel-iron hydroxide/nickel-iron alloy heterojunction.
The preparation method of the wood-based electrocatalyst loading the nickel-iron hydroxide/nickel-iron alloy comprises the following steps:
(1) A large piece of poplar was cut out to have a size of 2.0 cm. Times.0.8 cm. Times.1 mm (length. Times.width. Times.height), and weighed to have a mass of 0.05g.
(2) Adding the wood chips obtained in the step (1) into a nickel-iron nitrate solution (0.200 g of nickel nitrate hexahydrate and ferric nitrate nonahydrate in total, wherein the molar ratio of nickel ions to iron ions in the solution is 0.65 to 1), placing the wood chips into a vacuum drying oven for vacuum impregnation, and keeping the impregnation temperature at 100 ℃ for 12 hours.
(3) And (3) placing the wood chips impregnated with the nickel iron ions in the step (2) into a common drying oven, wherein the drying temperature is 100 ℃, and the drying time is 5 hours.
(4) And (4) placing the dried wood chips in the step (3) into a tubular furnace, heating to 900 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, and preserving heat for 2h. And then naturally cooling to room temperature to obtain the charcoal loaded with the nickel-iron alloy.
(5) And (3) putting the nickel-iron alloy loaded charcoal in the step (4) into a mixed solution of nickel-iron nitrate and urea (wherein the total amount of nickel nitrate hexahydrate and ferric nitrate nonahydrate is 0.400g, the molar ratio of nickel ions to iron ions in the solution is 0.67 and the amount of urea is 0.200g, then transferring the mixture into a reaction kettle, heating the mixture in a common drying box, keeping the hydrothermal temperature at 120 ℃ for 12h, and naturally cooling the mixture to room temperature to obtain the wood-based electrocatalyst NiFe-LDHs @ NiFe/CW in the embodiment.
The wood-based electrocatalyst in the embodiment is directly used as a working electrode, and is soaked in a 1.0M KOH solution for oxygen evolution linear sweep voltammetry test, so that the electrocatalytic activity of the oxygen evolution reaction is represented. At 50mA.cm -2 The overpotential of the wood-based catalyst is only 270mV at the current density, and the catalytic activity of the wood-based catalyst is far better than that of a commercial noble metal oxide OER catalyst.
Example 5:
the wood-based electrocatalyst with supported nickel-iron hydroxide/nickel-iron alloy has carbonized wood with three-dimensional layered porous structure and vertically oriented channels as charcoal skeleton with homogeneously and firmly supported nickel-iron hydroxide/nickel-iron alloy heterojunction.
The preparation method of the wood-based electrocatalyst loading the nickel-iron hydroxide/nickel-iron alloy comprises the following steps:
(1) A large piece of poplar was cut out to have a size of 2.0 cm. Times.0.8 cm. Times.1 mm (length. Times.width. Times.height), and weighed to have a mass of 0.05g.
(2) Adding the wood chips obtained in the step (1) into a nickel iron nitrate solution (0.500 g of nickel nitrate hexahydrate and ferric nitrate nonahydrate, wherein the molar ratio of nickel ions to iron ions in the solution is 0.67), placing the wood chips into a vacuum drying oven for vacuum impregnation, and maintaining the impregnation temperature at 100 ℃ and the impregnation time at 12h.
(3) And (3) placing the wood chips impregnated with the nickel iron ions in the step (2) into a common drying oven, wherein the drying temperature is 100 ℃, and the drying time is 5 hours.
(4) And (4) placing the dried wood chips in the step (3) into a tubular furnace, heating to 900 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, and preserving heat for 2h. And naturally cooling to room temperature to obtain the charcoal loaded with the nickel-iron alloy.
(5) Putting the charcoal loaded with the nickel-iron alloy in the step (4) into a mixed solution of nickel-iron nitrate and urea (wherein the total amount of nickel nitrate hexahydrate and ferric nitrate nonahydrate is 0.400g, the molar ratio of nickel ions to iron ions in the solution is 0.67 and the amount of urea is 0.200 g), then moving the charcoal into a reaction kettle, heating the charcoal in a common drying oven, and keeping the hydrothermal temperature at 120 ℃ for 12h. Then naturally cooled to room temperature, thus obtaining the wood-based electrocatalyst NiFe-LDHs @ NiFe/CW in the embodiment.
The wood-based electrocatalyst in the embodiment is directly used as a working electrode, and is soaked in a 1.0M KOH solution for oxygen evolution linear sweep voltammetry test, so that the electrocatalytic activity of the oxygen evolution reaction is represented. At 50mA.cm -2 The overpotential of the wood-based catalyst is only 285mV under the current density, and the catalytic activity of the wood-based catalyst is far better than that of a commercial noble metal oxide OER catalyst.
Example 6:
the wood-based electrocatalyst with supported nickel-iron hydroxide/nickel-iron alloy has carbonized wood with three-dimensional layered porous structure and vertically oriented channels as charcoal skeleton with homogeneously and firmly supported nickel-iron hydroxide/nickel-iron alloy heterojunction.
The preparation method of the wood-based electrocatalyst loading the nickel-iron hydroxide/nickel-iron alloy comprises the following steps:
(1) A large piece of poplar was cut to a size of 2.0 cm. Times.0.8 cm. Times.1 mm (length. Times.width. Times.height), and weighed to have a mass of 0.05g.
(2) Adding the wood chips obtained in the step (1) into a nickel-iron nitrate solution (0.400 g of nickel nitrate hexahydrate and ferric nitrate nonahydrate, and the molar ratio of nickel ions to iron ions in the solution is 0.67 to 1), placing the wood chips into a vacuum drying oven for vacuum impregnation, and keeping the impregnation temperature at 100 ℃ and the impregnation time at 12h.
(3) And (3) placing the wood chips impregnated with the nickel iron ions in the step (2) into a common drying oven, wherein the drying temperature is 100 ℃, and the drying time is 5 hours.
(4) And (4) placing the dried wood chips in the step (3) into a tubular furnace, heating to 800 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, and preserving heat for 2h. And naturally cooling to room temperature to obtain the charcoal loaded with the nickel-iron alloy.
(5) Putting the charcoal loaded with the nickel-iron alloy in the step (4) into a mixed solution of nickel-iron nitrate and urea (wherein the total amount of nickel nitrate hexahydrate and ferric nitrate nonahydrate is 0.400g, the molar ratio of nickel ions to iron ions in the solution is 0.67 and the amount of urea is 0.200 g), then moving the charcoal into a reaction kettle, heating the charcoal in a common drying oven, and keeping the hydrothermal temperature at 120 ℃ for 12h. Then naturally cooled to room temperature, thus obtaining the wood-based electrocatalyst NiFe-LDHs @ NiFe/CW in the embodiment.
The wood-based electrocatalyst in the embodiment is directly used as a working electrode, and is soaked in a 1.0M KOH solution for oxygen evolution linear sweep voltammetry test, so that the electrocatalytic activity of the oxygen evolution reaction is represented. At 50mA.cm -2 The overpotential of the wood-based catalyst is only 256mV at current density, and the catalytic activity of the wood-based catalyst is far better than that of a commercial noble metal oxide OER catalyst.
Example 7:
the wood-based electrocatalyst with supported nickel-iron hydroxide/nickel-iron alloy has carbonized wood with three-dimensional layered porous structure and vertically oriented channels as charcoal skeleton with homogeneously and firmly supported nickel-iron hydroxide/nickel-iron alloy heterojunction.
The preparation method of the wood-based electrocatalyst loading the nickel-iron hydroxide/nickel-iron alloy comprises the following steps:
(1) A large piece of poplar was cut to a size of 2.0 cm. Times.0.8 cm. Times.1 mm (length. Times.width. Times.height), and weighed to have a mass of 0.05g.
(2) Adding the wood chips obtained in the step (1) into a nickel-iron nitrate solution (0.400 g of nickel nitrate hexahydrate and ferric nitrate nonahydrate, and the molar ratio of nickel ions to iron ions in the solution is 0.67 to 1), placing the wood chips into a vacuum drying oven for vacuum impregnation, and keeping the impregnation temperature at 100 ℃ and the impregnation time at 12h.
(3) And (3) placing the wood chips impregnated with the nickel iron ions in the step (2) into a common drying oven, wherein the drying temperature is 100 ℃, and the drying time is 5 hours.
(4) And (4) placing the dried wood chips in the step (3) into a tubular furnace, heating to 1000 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, and preserving heat for 2 hours. And then naturally cooling to room temperature to obtain the charcoal loaded with the nickel-iron alloy.
(5) Putting the charcoal loaded with the nickel-iron alloy in the step (4) into a mixed solution of nickel-iron nitrate and urea (wherein the total amount of nickel nitrate hexahydrate and ferric nitrate nonahydrate is 0.400g, the molar ratio of nickel ions to iron ions in the solution is 0.67 and the amount of urea is 0.200 g), then moving the charcoal into a reaction kettle, heating the charcoal in a common drying oven, and keeping the hydrothermal temperature at 120 ℃ for 12h. Then naturally cooled to room temperature, and the wood-based electrocatalyst NiFe-LDHs @ NiFe/CW in the embodiment is obtained.
The wood-based electrocatalyst in the embodiment is directly used as a working electrode, and is soaked in a 1.0M KOH solution for oxygen evolution linear sweep voltammetry test, so that the electrocatalytic activity of the oxygen evolution reaction is represented. At 50mA.cm -2 The overpotential of the wood-based catalyst is only 242mV at the current density, and the catalytic activity of the wood-based catalyst is far better than that of a commercial noble metal oxide OER catalyst.
Example 8:
the wood-based electrocatalyst with supported nickel-iron hydroxide/nickel-iron alloy has carbonized wood with three-dimensional layered porous structure and vertically oriented channels as charcoal skeleton with homogeneously and firmly supported nickel-iron hydroxide/nickel-iron alloy heterojunction.
The preparation method of the wood-based electrocatalyst loaded with the nickel-iron hydroxide/nickel-iron alloy comprises the following steps:
(1) A large piece of poplar was cut to a size of 2.0 cm. Times.0.8 cm. Times.1 mm (length. Times.width. Times.height), and weighed to have a mass of 0.05g.
(2) Adding the wood chips obtained in the step (1) into a nickel iron nitrate solution (0.400 g of nickel nitrate hexahydrate and ferric nitrate nonahydrate, wherein the molar ratio of nickel ions to iron ions in the solution is 0.67), placing the wood chips into a vacuum drying oven for vacuum impregnation, and maintaining the impregnation temperature at 100 ℃ and the impregnation time at 12h.
(3) And (3) putting the wood chips impregnated with the nickel iron ions in the step (2) into a common drying oven, wherein the drying temperature is 100 ℃, and the drying time is 5 hours.
(4) And (4) placing the dried wood chips obtained in the step (3) into a tube furnace, heating to 900 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, and preserving heat for 2h. And naturally cooling to room temperature to obtain the charcoal loaded with the nickel-iron alloy.
(5) Putting the charcoal loaded with the nickel-iron alloy in the step (4) into a mixed solution of nickel-iron nitrate and urea (wherein the total amount of nickel nitrate hexahydrate and ferric nitrate nonahydrate is 0.200g, the molar ratio of nickel ions to iron ions in the solution is 0.67 and the amount of urea is 0.200 g), then moving the charcoal into a reaction kettle, heating the charcoal in a common drying oven, and keeping the hydrothermal temperature at 120 ℃ for 12h. Then naturally cooled to room temperature, and the wood-based electrocatalyst NiFe-LDHs @ NiFe/CW in the embodiment is obtained.
The wood-based electrocatalyst in the embodiment is directly used as a working electrode, and is soaked in a 1.0M KOH solution for oxygen evolution linear sweep voltammetry test, so that the electrocatalytic activity of the oxygen evolution reaction is represented. At 50mA.cm -2 The overpotential of the wood-based catalyst is only 263mV at the current density, and the catalytic activity of the wood-based catalyst is far better than that of a commercial noble metal oxide OER catalyst.
Example 9:
the wood-based electrocatalyst with supported nickel-iron hydroxide/nickel-iron alloy has carbonized wood with three-dimensional layered porous structure and vertically oriented channels as charcoal skeleton with homogeneously and firmly supported nickel-iron hydroxide/nickel-iron alloy heterojunction.
The preparation method of the wood-based electrocatalyst loaded with the nickel-iron hydroxide/nickel-iron alloy comprises the following steps:
(1) A large piece of poplar was cut to a size of 2.0 cm. Times.0.8 cm. Times.1 mm (length. Times.width. Times.height), and weighed to have a mass of 0.05g.
(2) Adding the wood chips obtained in the step (1) into a nickel iron nitrate solution (0.400 g of nickel nitrate hexahydrate and ferric nitrate nonahydrate, wherein the molar ratio of nickel ions to iron ions in the solution is 0.67), placing the wood chips into a vacuum drying oven for vacuum impregnation, and maintaining the impregnation temperature at 100 ℃ and the impregnation time at 12h.
(3) And (3) placing the wood chips impregnated with the nickel iron ions in the step (2) into a common drying oven, wherein the drying temperature is 100 ℃, and the drying time is 5 hours.
(4) And (4) placing the dried wood chips obtained in the step (3) into a tube furnace, heating to 900 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, and preserving heat for 2h. And then naturally cooling to room temperature to obtain the charcoal loaded with the nickel-iron alloy.
(5) Putting the nickel-iron alloy loaded charcoal in the step (4) into a mixed solution of nickel-iron nitrate and urea (wherein the total amount of nickel nitrate hexahydrate and ferric nitrate nonahydrate is 0.500g, the molar ratio of nickel ions to iron ions in the solution is 0.67 and the amount of urea is 0.200 g), then moving the charcoal into a reaction kettle, heating the charcoal in a common drying oven, and keeping the hydrothermal temperature at 120 ℃ for 12h. Then naturally cooled to room temperature, and the wood-based electrocatalyst NiFe-LDHs @ NiFe/CW in the embodiment is obtained.
The wood-based electrocatalyst in the embodiment is directly used as a working electrode, and is soaked in a 1.0M KOH solution for oxygen evolution linear sweep voltammetry test, so that the electrocatalytic activity of the oxygen evolution reaction is represented. At 50mA.cm -2 The overpotential of the wood-based catalyst is only 256mV at current density, and the catalytic activity of the wood-based catalyst is far better than that of a commercial noble metal oxide OER catalyst.
Example 10:
the wood-based electrocatalyst with supported nickel-iron hydroxide/nickel-iron alloy has carbonized wood with three-dimensional layered porous structure and vertically oriented channels as charcoal skeleton with homogeneously and firmly supported nickel-iron hydroxide/nickel-iron alloy heterojunction.
The preparation method of the wood-based electrocatalyst loading the nickel-iron hydroxide/nickel-iron alloy comprises the following steps:
(1) A large piece of poplar was cut to a size of 2.0 cm. Times.0.8 cm. Times.1 mm (length. Times.width. Times.height), and weighed to have a mass of 0.05g.
(2) Adding the wood chips obtained in the step (1) into a nickel-iron nitrate solution (0.400 g of nickel nitrate hexahydrate and ferric nitrate nonahydrate, and the molar ratio of nickel ions to iron ions in the solution is 0.67 to 1), placing the wood chips into a vacuum drying oven for vacuum impregnation, and keeping the impregnation temperature at 100 ℃ and the impregnation time at 12h.
(3) And (3) putting the wood chips impregnated with the nickel iron ions in the step (2) into a common drying oven, wherein the drying temperature is 100 ℃, and the drying time is 5 hours.
(4) And (4) placing the dried wood chips obtained in the step (3) into a tube furnace, heating to 900 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, and preserving heat for 2h. And then naturally cooling to room temperature to obtain the charcoal loaded with the nickel-iron alloy.
(5) Putting the charcoal loaded with the nickel-iron alloy in the step (4) into a mixed solution of nickel-iron nitrate and urea (wherein the total amount of nickel nitrate hexahydrate and ferric nitrate nonahydrate is 0.400g, the molar ratio of nickel ions to iron ions in the solution is 1.25, and the amount of urea is 0.200 g), then moving the charcoal into a reaction kettle, heating the charcoal in a common drying oven, and keeping the hydrothermal temperature at 120 ℃ for 12h. Then naturally cooled to room temperature, and the wood-based electrocatalyst NiFe-LDHs @ NiFe/CW in the embodiment is obtained.
The wood-based electrocatalyst in the embodiment is directly used as a working electrode, and is soaked in a 1.0M KOH solution for oxygen evolution linear sweep voltammetry test, so that the electrocatalytic activity of the oxygen evolution reaction is represented. At 50mA.cm -2 Under the current density, the overpotential of the wood-based catalyst is only 256mV, and the catalytic activity of the wood-based catalyst is far better than that of the wood-based catalystCommercial noble metal oxide OER catalysts.
Example 11:
the wood-based electrocatalyst of supported nickel-iron hydroxide/nickel-iron alloy has carbonized wood with three-dimensional hierarchical porous structure and vertically oriented channels as charcoal skeleton with homogeneously and firmly supported nickel-iron hydroxide/nickel-iron alloy heterojunction.
The preparation method of the wood-based electrocatalyst loading the nickel-iron hydroxide/nickel-iron alloy comprises the following steps:
(1) A large piece of poplar was cut to a size of 2.0 cm. Times.0.8 cm. Times.1 mm (length. Times.width. Times.height), and weighed to have a mass of 0.05g.
(2) Adding the wood chips obtained in the step (1) into a nickel iron nitrate solution (0.400 g of nickel nitrate hexahydrate and ferric nitrate nonahydrate, wherein the molar ratio of nickel ions to iron ions in the solution is 0.67), placing the wood chips into a vacuum drying oven for vacuum impregnation, and maintaining the impregnation temperature at 100 ℃ and the impregnation time at 12h.
(3) And (3) placing the wood chips impregnated with the nickel iron ions in the step (2) into a common drying oven, wherein the drying temperature is 100 ℃, and the drying time is 5 hours.
(4) And (4) placing the dried wood chips obtained in the step (3) into a tube furnace, heating to 900 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, and preserving heat for 2h. And naturally cooling to room temperature to obtain the charcoal loaded with the nickel-iron alloy.
(5) Putting the charcoal loaded with the nickel-iron alloy in the step (4) into a mixed solution of nickel-iron nitrate and urea (wherein the total amount of nickel nitrate hexahydrate and ferric nitrate nonahydrate is 0.400g, the molar ratio of nickel ions to iron ions in the solution is 0.5, and the amount of urea is 0.200 g), then moving the charcoal into a reaction kettle, heating the charcoal in a common drying oven, and keeping the hydrothermal temperature at 120 ℃ for 12h. Then naturally cooled to room temperature, thus obtaining the wood-based electrocatalyst NiFe-LDHs @ NiFe/CW in the embodiment.
The wood-based electrocatalyst in the embodiment is directly used as a working electrode, and is soaked in a 1.0M KOH solution for oxygen evolution linear sweep voltammetry test, so that the electrocatalytic activity of the oxygen evolution reaction is represented. At 50mA.cm -2 The overpotential of the wood-based catalyst is only 235mV under the current density, and the catalytic activity of the wood-based catalyst is far better than that of a commercial noble metal oxide OER catalyst.
Example 12:
a catalyst for hydrogen production by water electrolysis, comprising a HER catalyst and an OER catalyst, wherein the OER catalyst is the nickel iron hydroxide/nickel iron alloy supported wood-based electrocatalyst obtained in example 1. The HER catalyst is a wood-based electrocatalyst loaded with molybdenum carbide, and the electrocatalyst takes three-dimensional porous carbonized wood as a framework and takes pyrolysis gas generated during wood carbonization as a carbon source to synthesize molybdenum carbide particles and load the molybdenum carbide particles on the carbonized wood framework. The specific surface area of the catalyst was 200m 2 The size of the molybdenum carbide particles is 10-20nm. The preparation method of the wood-based electrocatalyst loaded with molybdenum carbide comprises the following steps:
(1) A large piece of poplar was cut into a size of 2.0 cm. Times.0.8 cm. Times.1 mm (length. Times.width. Times.height), and the mass (0.05 g) was weighed.
(2) Adding the wood chips obtained in the step (1) into 0.5mol/L ammonium molybdate solution (the molybdenum salt is excessive relative to the wood chips, the same is applied below), and placing the wood chips into a vacuum drying oven for vacuum impregnation, wherein the impregnation temperature is kept at 80 ℃, and the impregnation time is kept at 8h.
(3) And (3) placing the impregnated wood chips obtained in the step (2) into a common drying oven, wherein the drying temperature is 60 ℃, and the drying time is 4 hours.
(4) And (4) placing the dried impregnated wood chips in the step (3) into a tubular furnace, heating to 900 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, and preserving heat for 2h. Then naturally cooling to room temperature to obtain the molybdenum carbide loaded wood-based electrocatalyst Mo in the embodiment 2 C/CW。
The molybdenum carbide-loaded wood-based electrocatalyst in the embodiment is directly used as a working electrode, and is soaked in a 1.0M KOH solution for hydrogen evolution linear sweep voltammetry test, so as to characterize the electrocatalytic activity of the hydrogen evolution reaction. At 50mA.cm -2 The overpotential of the molybdenum carbide-loaded wood-based electrocatalyst is only 94mV at the current density, and the excellent electrocatalytic activity is shown. In addition, the wood-based electrocatalyst supporting molybdenum carbide in the present example was used directly as the working electrode,the long-term stability was determined by soaking in 1.0M KOH solution for 100h of a chronopotentiometric test. The voltage increased only about 2.3% after 100h stability test, representing excellent stability of the catalyst.

Claims (9)

1. A preparation method of a wood-based electrocatalyst loaded with nickel-iron hydroxide/nickel-iron alloy is characterized in that the wood-based electrocatalyst comprises a charcoal skeleton with a three-dimensional porous structure and an active substance loaded on the charcoal skeleton, wherein the active substance comprises a nickel-iron hydroxide/nickel-iron alloy heterojunction with a nickel-iron alloy as a bottom layer and a nickel-iron hydroxide as a surface layer;
the preparation method comprises the following steps:
(1) Placing the wood chips in a nickel-iron metal salt solution for impregnation treatment, taking out and drying to obtain the wood chips loaded with nickel-iron ions;
(2) Calcining the wood chips loaded with nickel-iron ions obtained in the step (1) at high temperature in an inert atmosphere to obtain charcoal loaded with nickel-iron alloy;
(3) And (3) placing the charcoal loaded with the nickel-iron alloy obtained in the step (2) into a mixed solution of nickel-iron metal salt and urea for hydrothermal treatment to obtain the wood-based electrocatalyst loaded with the nickel-iron hydroxide/nickel-iron alloy.
2. The preparation method according to claim 1, wherein the specific surface area of the wood-based electrocatalyst is 100 to 400m 2 The size of the active substance in the wood-based electrocatalyst is 50-200nm, and the loading rate of the active substance in the wood-based electrocatalyst is 0.2-10%.
3. The production method according to claim 1, wherein the nickel iron metal salt solution is a mixed solution of a nickel salt and an iron salt; the nickel salt comprises at least one of nickel nitrate, nickel chloride and nickel acetate; the ferric salt comprises at least one of ferric nitrate, ferric chloride and ferric acetate; and in the nickel-iron metal salt solution, the molar ratio of nickel to iron is controlled to be (0.1-9): 1.
4. the method for preparing according to claim 1, characterized in that, during the impregnation treatment, the mass ratio of the wood chips to the nickel-iron metal salt in the nickel-iron metal salt solution is controlled to be (0.1-10): 1.
5. the preparation method according to claim 1, wherein the impregnation treatment is a vacuum impregnation treatment, which is carried out in a vacuum drying oven while maintaining an impregnation temperature of 10 to 150 ℃ and an impregnation time of 1 to 24 hours; the drying temperature is controlled to be 10-120 ℃ during drying, and the drying time is 1-24h.
6. The method according to any one of claims 1 to 5, wherein the high-temperature calcination is carried out in a tube furnace while maintaining the calcination temperature at 600 to 1000 ℃, the temperature increase rate at 5 to 10 ℃/min, and the calcination time at 1 to 3 hours.
7. The production method according to any one of claims 1 to 5, wherein the molar ratio of the nickel-iron metal salt to urea in the mixed solution of the nickel-iron metal salt and urea is (0.2 to 5): 1, and the molar ratio of nickel to iron in the nickel-iron metal salt is (0.1-9): 1.
8. the production method according to any one of claims 1 to 5, wherein the mass ratio of the nickel-iron alloy-supporting charcoal to the nickel-iron metal salt in the mixed solution of the nickel-iron metal salt and urea is controlled to be (0.1 to 10): 1.
9. the catalyst for hydrogen production by water electrolysis comprises a HER catalyst and an OER catalyst, and is characterized in that the OER catalyst is the wood-based electrocatalyst loaded with nickel-iron hydroxide/nickel-iron alloy and prepared by the preparation method of any one of claims 1-8.
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