Nickel-iron phosphide/graphene/nickel composite material, and preparation method and application thereof
阅读说明：本技术 镍-铁磷化物/石墨烯/镍复合材料、其制备方法及应用 (Nickel-iron phosphide/graphene/nickel composite material, and preparation method and application thereof ) 是由 李鑫恒 祁磊 张珍珍 于 2020-06-10 设计创作，主要内容包括：本发明公开了一种镍-铁磷化物/石墨烯/镍复合材料、其制备方法及应用。所述复合材料包括作为载体的石墨烯包裹镍材料,以及,负载于所述载体上的镍-铁磷化物阵列,所述石墨烯包裹镍材料包括镍以及包裹于镍表面的石墨烯材料,所述石墨烯材料具有直立鱼鳞阵列结构,所述镍-铁磷化物呈多孔阵列状结构。本发明制备镍-铁磷化物/石墨烯/镍复合材料在通过石墨烯包裹镍材料表面直接生长直立多孔镍-铁磷化物阵列,没有添加粘合剂,具有导电性高、稳定性好、重复性高的特点,且在碱性以及盐碱性条件下均有着良好的稳定性,并有着广泛的应用前景。(The invention discloses a nickel-iron phosphide/graphene/nickel composite material, and a preparation method and application thereof. The composite material comprises a graphene coated nickel material serving as a carrier and a nickel-iron phosphide array loaded on the carrier, wherein the graphene coated nickel material comprises nickel and a graphene material coated on the surface of the nickel, the graphene material has an upright fish scale array structure, and the nickel-iron phosphide is in a porous array structure. The prepared nickel-iron phosphide/graphene/nickel composite material directly grows the vertical porous nickel-iron phosphide array on the surface of the nickel material wrapped by the graphene without adding an adhesive, has the characteristics of high conductivity, good stability and high repeatability, has good stability under alkaline and saline-alkaline conditions, and has wide application prospect.)
1. The nickel-iron phosphide/graphene/nickel composite material is characterized by comprising a graphene-coated nickel material serving as a carrier and a nickel-iron phosphide array loaded on the carrier, wherein the graphene-coated nickel material comprises nickel and a graphene material coated on the surface of the nickel, the graphene material has an upright fish scale array structure, and the nickel-iron phosphide is in a porous array structure;
preferably, the loading capacity of the nickel-iron phosphide array in the nickel-iron phosphide/graphene/nickel composite material is 0.3-0.5 mg;
preferably, the loading amount of the graphene material in the nickel-iron phosphide/graphene/nickel composite material is 0.2-0.5 mg.
2. The nickel-iron phosphide/graphene/nickel composite material of claim 1, wherein: the carrier has a porous structure, and the aperture of a hole contained in the porous structure is 50 nm-400 mu m;
and/or the nickel-iron phosphide is derived from a nickel-iron metal organic framework structure, the nickel-iron phosphide has a hierarchical pore structure, the hierarchical pore structure is composed of micropores and/or mesopores, and the pore diameter of pores contained in the hierarchical pore structure is 0.2 nm-50 nm.
3. A preparation method of a nickel-iron phosphide/graphene/nickel composite material is characterized by comprising the following steps:
carrying out hydrothermal reaction on nickel and graphene oxide to obtain a graphene coated nickel material;
reacting a mixed system containing nickel salt, iron salt, an organic ligand and a graphene-coated nickel material by a chemical bath deposition method, so as to grow a nickel-iron metal organic framework structure on the surface of the graphene-coated nickel material, and obtain a nickel-iron metal organic framework structure/graphene/nickel composite material with a sandwich structure;
calcining the nickel-iron metal organic framework structure/graphene/nickel composite material to obtain a nickel-iron oxide/graphene/nickel composite material;
and in a phosphorization atmosphere, carrying out phosphorization reduction treatment on the obtained nickel-iron oxide/graphene/nickel composite material to obtain the nickel-iron phosphide/graphene/nickel composite material.
4. The production method according to claim 3, characterized by comprising:
and mixing the graphene oxide, a reducing agent, nickel and water to form a first mixed reaction system, and then carrying out hydrothermal reaction at 50-300 ℃ for 1-72h to obtain the graphene coated nickel material.
5. The method of claim 4, wherein: the reducing agent comprises ammonia and/or hydrazine hydrate;
and/or the mass volume ratio of the graphene oxide to the water is 0.05: 1-50: 1 mg/ml;
and/or the volume ratio of the reducing agent to water is 1: 200-1: 500;
and/or the mass volume ratio of the graphene oxide to the reducing agent is 100: 1-500: 1 mg/ml;
and/or, the preparation method further comprises the following steps: after the hydrothermal reaction is finished, washing and drying the obtained material; preferably, the drying treatment temperature is 40-200 ℃, the drying treatment time is 2-48 h, and particularly preferably 60-100 ℃.
6. The production method according to claim 3, characterized by comprising:
mixing nickel salt, iron salt, an organic ligand, the graphene-coated nickel material and water to form a second mixed reaction system, then reacting for 1-48 hours at 40-80 ℃, and growing a nickel-iron metal organic framework structure on the surface of the graphene-coated nickel material to form the nickel-iron metal organic framework structure/graphene/nickel composite material with the sandwich structure;
preferably, the nickel salt comprises any one or a combination of more than two of nickel acetate, nickel nitrate, nickel chloride, nickel sulfate and nickel acetylacetonate;
preferably, the iron salt comprises any one or a combination of more than two of ferric nitrate, ferric chloride, ferric sulfate and ferric acetylacetonate;
preferably, the organic ligand comprises any one or the combination of more than two of dimethyl carboxylate, dimethyl carboxylate and derivatives thereof, p-carboxybenzene derivatives, dipotassium carboxylate and dipotassium carboxylate derivatives;
preferably, the mass ratio of the nickel salt to the iron salt is 20: 1-1: 20;
preferably, the mass ratio of the nickel salt to the organic ligand is 0.1: 1-40: 1;
preferably, the mass ratio of the ferric salt to the organic ligand is 0.1: 1-10: 1;
preferably, the mass volume ratio of the nickel salt to the water is 1: 5-1: 20 mg/ml;
preferably, the mass volume ratio of the ferric salt to the water is 1: 20-1: 80 mg/ml;
preferably, the preparation method further comprises: and after the reaction of the second mixed reaction system is finished, washing and drying the obtained material.
7. The production method according to claim 3, characterized by comprising: calcining the nickel-iron metal organic frame structure/graphene/nickel composite material in the air at 100-800 ℃ for 1-6 h to obtain the nickel-iron oxide/graphene/nickel composite material;
and/or, the preparation method comprises the following steps: in a phosphorization atmosphere, carrying out phosphorization reduction treatment on the obtained nickel-iron oxide/graphene/nickel composite material at 100-800 ℃ for 1-8 h to obtain the nickel-iron phosphide/graphene/nickel composite material;
and/or, the phosphating atmosphere comprises phosphine and a protective gas; preferably, the phosphine is generated by thermal decomposition of a phosphorus source; preferably, the phosphorus source comprises one or a combination of more than two of sodium phosphate, sodium phosphite and sodium hypophosphite; preferably, the protective gas comprises nitrogen and/or an inert gas; particularly preferably, the mass ratio of the phosphorus source to the nickel salt is 1000: 1-1500: 1.
8. The nickel-iron phosphide/graphene/nickel composite material prepared by the method of any one of claims 3 to 7, which is characterized by comprising a graphene-coated nickel material as a carrier and a nickel-iron phosphide array loaded on the carrier, wherein the nickel-iron phosphide/graphene/nickel composite material has a sandwich structure with hierarchical pores;
preferably, the carrier has a porous structure, and the pore diameter of pores contained in the porous structure is 50 nm-400 μm;
preferably, the nickel-iron phosphide is derived from a nickel-iron metal organic framework structure, the nickel-iron phosphide has a hierarchical pore structure, the hierarchical pore structure is composed of micropores and/or mesopores, and the pore diameter of pores contained in the hierarchical pore structure is 0.2 nm-50 nm.
9. Use of the nickel-iron phosphide/graphene/nickel composite material of any one of claims 1-2 and 8 as an electrochemical catalyst in an electrochemical oxygen evolution reaction;
preferably, the electrolyte used in the electrochemical oxygen evolution reaction comprises any one of 0.1-3.0 mol/L potassium hydroxide solution, and a mixed solution of 0.1-3.0 mol/L potassium hydroxide and 0.1-3.0 mol/L sodium chloride.
10. An electrocatalytic oxygen evolution material, characterized in that it comprises at least a nickel-iron-phosphide/graphene/nickel composite material according to any one of claims 1 to 2, 8.
Technical Field
The invention belongs to the technical field of nano material preparation and electrocatalysis, and particularly relates to a nickel-iron phosphide/graphene/nickel composite material, a preparation method and application thereof, in particular to a nickel-iron phosphide/graphene/nickel composite material with a sandwich structure, and a preparation method and application thereof.
Background
The increased demand for energy and the increased pollution have led to the search for alternative energy sources and the design of efficient energy storage devices. Hydrogen has a high energy density and is considered a promising energy alternative to fossil fuels. At present, the production of hydrogen is still largely dependent on the fossil fuel industry, resulting in low purity and high cost. One of the most efficient methods of producing hydrogen at low cost and high purity is to split water into hydrogen and oxygen by electricity or sunlight. The oxygen decomposition reaction has been studied for decades as an important half reaction in water decomposition, wherein iridium dioxide and ruthenium dioxide are the latest oxygen evolution electrocatalysts, having low overpotential and tafel slope. However, these catalysts are in short supply and costly and cannot be used in the water splitting industry to obtain economical hydrogen. Nickel is a transition metal element, has abundant earth reserves, has corrosion resistance and good ductility. In recent years, it has been found that layered nickel phosphide is an excellent catalyst which can be more efficiently converted to active site formation in alkaline solutions, rather than nickel oxides and hydroxides. More importantly, theoretical and experimental results prove that the doped iron element can adjust the local coordination environment and the electronic structure catalytic activity of the nickel phosphide, so that the oxygen precipitation activity is enhanced. However, in addition to the activity of the catalyst itself, it is also important that the conductivity of the catalyst and the specific surface area be greater to expose more active sites. Therefore, how to design the structure of the catalyst is also a key issue. Most of the two-dimensional catalytic materials reported so far are prepared in the form of powders, which limit the macro-porosity for efficient transport of electrons, ions and gases during electrocatalysis. In addition, the porous material used as the carrier is also very important, and at present, the macroporous materials such as nickel/titanium, carbon cloth/paper and the like are mainly used for loading the catalyst for decomposing water, but the effect needs to be improved.
Disclosure of Invention
The invention mainly aims to provide a nickel-iron phosphide/graphene/nickel composite material, a preparation method and application thereof, so as to overcome the defects of the prior art.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
the embodiment of the invention provides a nickel-iron phosphide/graphene/nickel composite material which comprises a graphene-coated nickel material serving as a carrier and a nickel-iron phosphide array loaded on the carrier, wherein the graphene-coated nickel material comprises nickel and a graphene material coated on the surface of the nickel, the graphene material has a vertical fish scale array structure, and the nickel-iron phosphide is in a porous array structure.
The embodiment of the invention also provides a preparation method of the nickel-iron phosphide/graphene/nickel composite material, which comprises the following steps:
carrying out hydrothermal reaction on nickel and graphene oxide to obtain a graphene coated nickel material;
reacting a mixed system containing nickel salt, iron salt, an organic ligand and a graphene-coated nickel material by a chemical bath deposition method, so as to grow a nickel-iron metal organic framework structure on the surface of the graphene-coated nickel material, and obtain a nickel-iron metal organic framework structure/graphene/nickel composite material with a sandwich structure;
calcining the nickel-iron metal organic framework structure/graphene/nickel composite material to obtain a nickel-iron oxide/graphene/nickel composite material;
and in a phosphorization atmosphere, carrying out phosphorization reduction treatment on the obtained nickel-iron oxide/graphene/nickel composite material to obtain the nickel-iron phosphide/graphene/nickel composite material.
The embodiment of the invention also provides the nickel-iron phosphide/graphene/nickel composite material prepared by the method, which comprises a graphene-coated nickel material used as a carrier and a nickel-iron phosphide array loaded on the carrier, wherein the nickel-iron phosphide/graphene/nickel composite material has a sandwich structure with multilevel pores.
The embodiment of the invention also provides application of the nickel-iron phosphide/graphene/nickel composite material as an electrochemical catalyst in an electrochemical oxygen evolution reaction.
The embodiment of the invention also provides an electrocatalytic oxygen evolution material which at least comprises the nickel-iron phosphide/graphene/nickel composite material.
The graphene-coated nickel material is used as an electrocatalyst carrier, not only can load nickel-iron phosphide, but also can be used as a carrier of other electrocatalytic materials.
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the invention, the nickel-iron phosphide array in the shape of a vertical fish scale directly grows on the surface of the graphene-coated nickel material, and no adhesive is added, so that the graphene-coated nickel phosphide array has the characteristics of high conductivity, good stability and high repeatability;
(2) the composite material prepared by the invention has excellent conductivity and stability, and the graphene coating can improve the stability of the nickel material, so that the composite material has broad spectrum;
(3) the composite material prepared by the method has good stability under alkaline and saline-alkaline conditions, and has wide practical application prospect.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1a to 1d are scanning electron microscope images of a graphene-coated nickel electrode, a nickel-iron metal organic framework/graphene/nickel composite material, a nickel-iron oxide/graphene/nickel composite material, and a nickel-iron phosphide/graphene/nickel composite material in example 1 of the present invention, respectively;
FIGS. 2a-2b are XRD spectra of Ni-Fe metal organic framework/graphene/Ni composite, Ni-Fe oxide/graphene/Ni composite, and Ni-Fe-phosphide/graphene/Ni composite in example 1 of the present invention;
fig. 3a-3b are the polarization curves of the nickel electrode, the graphene-coated nickel electrode, the nickel-iron metal organic framework/graphene/nickel composite material, the nickel-iron oxide/graphene/nickel composite material, the nickel-iron phosphide/graphene/nickel composite material, and the electrochemical impedance curves of the nickel-iron phosphide/graphene/nickel composite material in example 1 of the present invention, respectively;
fig. 4a to 4b are stability test charts of the nickel-iron phosphide/graphene/nickel composite material in the alkaline environment and the saline-alkaline environment in example 1 of the present invention.
Detailed Description
In view of the defects of the prior art, the inventor of the present invention has made long-term research and extensive practice to provide the technical scheme of the present invention, which is mainly based on that graphene coated nickel material with good stability is used as a carrier, and array-shaped nickel-iron phosphide is directly grown on the surface of the graphene, so as to form a hierarchical pore structure.
The technical solutions of the present invention will be described clearly and completely below, and it should be apparent that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
One aspect of the embodiment of the invention provides a nickel-iron phosphide/graphene/nickel composite material, which comprises a graphene-coated nickel material used as a carrier and a nickel-iron phosphide array loaded on the carrier, wherein the graphene-coated nickel material comprises nickel and a graphene material coated on the surface of the nickel, the graphene material has a vertical fish scale array structure, and the nickel-iron phosphide is in a porous array structure.
Furthermore, the loading capacity of the nickel-iron phosphide array in the nickel-iron phosphide/graphene/nickel composite material is 0.3-0.5 mg.
Furthermore, the loading amount of the graphene material in the nickel-iron phosphide/graphene/nickel composite material is 0.2-0.5 mg.
Further, the graphene-coated nickel material may be a graphene-coated nickel electrode.
Furthermore, the carrier has a porous structure, and the pore diameter of pores contained in the porous structure is 50 nm-400 mu m.
Further, the nickel-iron phosphide is derived from a nickel-iron metal organic framework structure, the nickel-iron phosphide has a hierarchical pore structure, the hierarchical pore structure is composed of micropores and/or mesopores, and the pore diameter of pores contained in the hierarchical pore structure is 0.2 nm-50 nm.
Another aspect of the embodiments of the present invention also provides a method for preparing a nickel-iron phosphide/graphene/nickel composite material, including:
carrying out hydrothermal reaction on nickel and graphene oxide to obtain a graphene coated nickel material;
reacting a mixed system containing nickel salt, iron salt, an organic ligand and a graphene-coated nickel material by a chemical bath deposition method, so as to grow a nickel-iron metal organic framework structure on the surface of the graphene-coated nickel material, and obtain a nickel-iron metal organic framework structure/graphene/nickel composite material with a sandwich structure;
calcining the nickel-iron metal organic framework structure/graphene/nickel composite material to obtain a nickel-iron oxide/graphene/nickel composite material;
and in a phosphorization atmosphere, carrying out phosphorization reduction treatment on the obtained nickel-iron oxide/graphene/nickel composite material to obtain the nickel-iron phosphide/graphene/nickel composite material.
In some more specific embodiments, the preparation method comprises:
and mixing the graphene oxide, a reducing agent, nickel and water to form a first mixed reaction system, and then carrying out hydrothermal reaction at 50-300 ℃ for 1-72h to obtain the graphene coated nickel material.
Further, the nickel may be a nickel electrode.
Further, the graphene-coated nickel material may be a graphene-coated nickel electrode.
Further, the reducing agent includes any one of ammonia water and hydrazine hydrate or a combination of the two, and is not limited thereto.
Further, the mass-to-volume ratio of the graphene oxide to the water is 0.05: 1-50: 1 mg/ml.
Further, the volume ratio of the reducing agent to water is 1: 200-1: 500.
Further, the mass-to-volume ratio of the graphene oxide to the reducing agent is 100: 1-500: 1 mg/ml.
Further, the preparation method further comprises the following steps: and after the hydrothermal reaction is finished, washing and drying the obtained material.
Furthermore, the number of washing treatments is 3 to 6.
Furthermore, the drying treatment temperature is 40-200 ℃, and the drying treatment time is 2-48 h.
Furthermore, the temperature of the drying treatment is 60-100 ℃.
In some more specific embodiments, the preparation method comprises:
mixing nickel salt, iron salt, an organic ligand, the graphene-coated nickel material and water to form a second mixed reaction system, then reacting for 1-48 h at 40-80 ℃, and growing a nickel-iron metal organic framework structure on the surface of the graphene-coated nickel material to form the nickel-iron metal organic framework structure/graphene/nickel composite material with the sandwich structure.
Further, the nickel salt includes any one or a combination of two or more of nickel acetate, nickel nitrate, nickel chloride, nickel sulfate, and nickel acetylacetonate, and is not limited thereto.
Further, the iron salt includes any one or a combination of two or more of ferric nitrate, ferric chloride, ferric sulfate, and ferric acetylacetonate, and is not limited thereto.
Further, the organic ligand includes any one or a combination of two or more of dimethyl carboxylate, dimethyl carboxylate and derivatives thereof, p-carboxybenzene derivatives, dipotassium carboxylate, and dipotassium carboxylate derivatives, and is not limited thereto.
Further, the mass ratio of the nickel salt to the iron salt is 20: 1-1: 20.
Further, the mass ratio of the nickel salt to the organic ligand is 0.1: 1-40: 1.
Further, the mass ratio of the iron salt to the organic ligand is 0.1: 1-10: 1.
Further, the mass volume ratio of the nickel salt to the water is 1: 5-1: 20 mg/ml.
Further, the mass volume ratio of the ferric salt to the water is 1: 20-1: 80 mg/ml.
Further, the preparation method further comprises the following steps: and after the reaction of the second mixed reaction system is finished, washing the obtained material for 3-6 times, and drying at 60-80 ℃.
In some more specific embodiments, the preparation method comprises: and calcining the nickel-iron metal organic frame structure/graphene/nickel composite material in the air at 100-800 ℃ for 1-6 h to obtain the nickel-iron oxide/graphene/nickel composite material.
In some more specific embodiments, the preparation method comprises: and in a phosphorization atmosphere, carrying out phosphorization reduction treatment on the obtained nickel-iron oxide/graphene/nickel composite material at 100-800 ℃ for 1-8 h to obtain the nickel-iron phosphide/graphene/nickel composite material.
Further, the phosphating atmosphere comprises phosphine and a protective gas.
Further, the phosphine is generated by thermal decomposition of a phosphorus source.
Further, the phosphorus source includes one or a combination of two or more of sodium phosphate, sodium phosphite, and sodium hypophosphite, but is not limited thereto.
Further, the protective gas comprises nitrogen or an inert gas.
Further, the mass ratio of the phosphorus source to the nickel salt is 1000: 1-1500: 1.
According to the invention, residual organic matters in the preparation process can be effectively removed through calcination treatment, so that the conductivity of the material is ensured, the non-conductive organic frame structure can be completely removed through calcination in the air, and the problem that carbon in the metal organic frame obstructs the pore structure due to high-temperature sintering in the subsequent phosphorization process and influences the performance of the material is avoided.
In another aspect of the embodiment of the present invention, there is also provided a nickel-iron phosphide/graphene/nickel composite material prepared by the foregoing method, which includes a graphene-coated nickel material as a carrier, and a nickel-iron phosphide array supported on the carrier, wherein the nickel-iron phosphide/graphene/nickel composite material has a sandwich structure with hierarchical pores.
Furthermore, the carrier has a porous structure, and the pore diameter of pores contained in the porous structure is 50 nm-400 mu m.
Further, the nickel-iron phosphide is derived from a nickel-iron metal organic framework structure, the nickel-iron phosphide has a hierarchical pore structure, the hierarchical pore structure is composed of micropores and/or mesopores, and the pore diameter of pores contained in the hierarchical pore structure is 0.2 nm-50 nm.
In another aspect of the embodiment of the invention, the application of the nickel-iron phosphide/graphene/nickel composite material as an electrochemical catalyst in an electrochemical oxygen evolution reaction is also provided.
For example, in some specific embodiments, the electrolyte used in the electrochemical oxygen evolution reaction comprises any one of 0.1-3.0 mol/L potassium hydroxide solution, 0.1-3.0 mol/L potassium hydroxide and 0.1-3.0 mol/L sodium chloride.
Preferably, the electrolyte used in the electrochemical oxygen evolution reaction includes any one of a 1mol/L potassium hydroxide solution, a 0.1mol/L potassium hydroxide solution, and a mixed solution of 1mol/L potassium hydroxide and 1mol/L sodium chloride, but is not limited thereto.
Another aspect of the embodiments of the present invention also provides an electrocatalytic oxygen evolution material, which at least comprises the aforementioned nickel-iron phosphide/graphene/nickel composite material.
The technical solutions of the present invention are further described in detail below with reference to several preferred embodiments and the accompanying drawings, which are implemented on the premise of the technical solutions of the present invention, and a detailed implementation manner and a specific operation process are provided, but the scope of the present invention is not limited to the following embodiments.
The experimental materials used in the examples used below were all available from conventional biochemical reagents companies, unless otherwise specified.
Example 1
(1) Preparation of graphene-coated nickel electrodes (rGO/NF): liquid-phase ultrasonic stripping graphene is used as a raw material, and an improved Hummers method is adopted to synthesize graphene oxide. Dispersing 70mg of prepared graphene in 70ml of water, and then adding NH3·H2O, nickel electrode. Transferring the obtained mixture into a stainless steel reaction kettle, heating for 24h at 240 ℃, naturally cooling to room temperature, taking out the nickel electrode, washing with ethanol and water for 3 times respectively, and drying at 60 ℃ for 12h to obtain the graphene-coated nickel electrode;
(2) preparation of nickel-iron metal organic framework/graphene/nickel composite (NiFe MOF/rGO/NF): adding prepared rGO/NF (1cm × 1cm) into the solution containing 20ml of H2O、1mg Ni(Ac)2And 0.5mg Fe (NO)3)3Adding 10mg of organic ligand dimethyl carboxylate into the reaction system, carrying out sealing reaction at 80 ℃ for 12h, and drying at 60 ℃ for 12h to obtain the nickel-iron metal organic framework/graphene/nickel composite material;
(3) preparation of nickel-iron oxide/graphene/nickel composite (NiFeO/rGO/NF): calcining the NiFe MOF/rGO/NF prepared in the step above for 2h at 350 ℃ in the air to obtain a nickel-iron oxide/graphene/nickel composite material;
(4) preparation of nickel-iron phosphide/graphene/nickel composite material (NiFeP/rGO/NF): and (3) calcining the NiFeO/rGO/NF prepared in the step above in phosphine gas at 350 ℃ for 2h to obtain the nickel-iron phosphide/graphene/nickel composite material.
Example 2
(1) Preparation of graphene-coated nickel electrodes (rGO/NF): liquid-phase ultrasonic stripping graphene is used as a raw material, and an improved Hummers method is adopted to synthesize graphene oxide. Dispersing 1mg of prepared graphene in 50ml of water, and then adding NH3·H2O, nickel electrode. Transferring the obtained mixture into a stainless steel reaction kettle, heating at 50 ℃ for 72h, naturally cooling to room temperature, taking out the nickel electrode, washing with ethanol and water for 3 times respectively, and drying at 60 ℃ for 12h to obtain the graphene-coated nickel electrode;
(2) preparation of nickel-iron metal organic framework/graphene/nickel composite (NiFe MOF/rGO/NF): adding prepared rGO/NF (1cm x 1cm) into 20ml of H2O, 2mg of nickel acetate and 1mg of ferric nitrate, then adding 10mg of organic ligand dimethyl carboxylate into the reaction system, carrying out sealed reaction at 40 ℃ for 48h, cooling to room temperature, taking out the electrode, carrying out ultrasonic treatment in a water bath for 1min, and drying at 40 ℃ for 48h to obtain the nickel-iron metal organic framework/graphene/nickel composite material;
(3) preparation of nickel-iron oxide/graphene/nickel composite material as in example 1;
(4) preparation of nickel-iron phosphide/graphene/nickel composite material (NiFeP/rGO/NF): and (3) calcining the NiFeO/rGO/NF prepared in the step above in phosphine gas at 800 ℃ for 1h to obtain the nickel-iron phosphide/graphene/nickel composite material.
Example 3
(1) Preparation of graphene-coated nickel electrodes (rGO/NF): liquid-phase ultrasonic stripping graphene is used as a raw material, and an improved Hummers method is adopted to synthesize graphene oxide. Dispersing 70mg of prepared graphene in 70ml of water, and then adding NH3·H2O, nickel electrode. Transferring the obtained mixture into a stainless steel reaction kettle, heating for 1h at 300 ℃, naturally cooling to room temperature, taking out the nickel electrode, washing with ethanol and water for 3 times respectively, and drying at 60 ℃ for 12h to obtain the graphene-coated nickel electrode;
(2) preparation of nickel-iron metal organic framework/graphene/nickel composite (NiFe MOF/rGO/NF): adding prepared rGO/NF (1cm x 1cm) into 20ml of H2O, 1mg of nickel chloride and 4mg of ferric chloride, then adding 10mg of organic ligand carboxylic acid dipotassium salt derivative into the reaction system, carrying out sealed reaction at 80 ℃ for 1h, cooling to room temperature, taking out an electrode, carrying out ultrasonic treatment in a water bath for 1min, and drying at 200 ℃ for 2h to obtain the nickel-iron metal organic framework/graphene/nickel composite material;
(3) preparation of nickel-iron oxide/graphene/nickel composite material as in example 1;
(4) preparation of nickel-iron phosphide/graphene/nickel composite material (NiFeP/rGO/NF): and (3) calcining the NiFeO/rGO/NF prepared in the step above in phosphine gas at 100 ℃ for 8h to obtain the nickel-iron phosphide/graphene/nickel composite material.
Example 4
(1) Preparation of graphene-coated nickel electrode as in example 1;
(2) preparation of nickel-iron metal organic framework/graphene/nickel composite (NiFe MOF/rGO/NF): to the prepared rGO/NF (1 cm. times.1 cm) was added 20ml H2O, 10mg of nickel sulfate and 20mg of ferric sulfate, then adding 10mg of organic ligand carboxylic acid dipotassium salt into the reaction system, carrying out sealed reaction for 25 hours at the temperature of 60 ℃, cooling to room temperature, taking out an electrode, carrying out ultrasonic treatment in a water bath for 1min, and drying for 12 hours at the temperature of 60 ℃ to obtain a nickel-iron metal organic framework/graphene/nickel composite material;
(3) preparation of nickel-iron oxide/graphene/nickel composite material as in example 1;
(4) the nickel-iron phosphide/graphene/nickel composite material was prepared as in example 1.
Example 5
(1) Preparation of graphene-coated nickel electrode as in example 1;
(2) preparation of nickel-iron metal organic framework/graphene/nickel composite (NiFe MOF/rGO/NF): adding prepared rGO/NF (1cm x 1cm) into 20ml of H2O, 1mg of nickel acetylacetonate and 8mg of iron acetylacetonate, then adding 10mg of organic ligand p-carboxyl benzene into the reaction system, carrying out sealing reaction for 25h at the temperature of 60 ℃, cooling to room temperature, taking out an electrode, carrying out water bath ultrasonic treatment for 1min, and drying for 12h at the temperature of 60 ℃ to obtain the nickel-iron metal organic framework/graphene/nickel composite material;
(3) preparation of nickel-iron oxide/graphene/nickel composite material as in example 1;
(4) the nickel-iron phosphide/graphene/nickel composite material was prepared as in example 1.
Example 6
(1) Preparation of graphene-coated nickel electrode as in example 1;
(2) preparation of nickel-iron metal organic framework/graphene/nickel composite (NiFe MOF/rGO/NF): adding prepared rGO/NF (1cm x 1cm) into 20ml of H2O、8mg Ni(Ac)2And 2mg FeCl3Adding 10mg of organic ligand dimethyl carboxylate into the reaction system, carrying out sealing reaction at 60 ℃ for 25h, cooling to room temperature, taking out an electrode, carrying out water bath ultrasonic treatment for 1min, and drying at 60 ℃ for 12h to obtain the nickel-iron metal organic framework/graphene/nickel composite material;
(3) preparation of nickel-iron oxide/graphene/nickel composite material as in example 1;
(4) the nickel-iron phosphide/graphene/nickel composite material was prepared as in example 1.
Example 7
(1) Preparation of graphene-coated nickel electrodes (rGO/NF): liquid-phase ultrasonic stripping graphene is used as a raw material, and an improved Hummers method is adopted to synthesize graphene oxide. 140mg of preparedGraphene oxide was dispersed in 70ml of water, followed by addition of NH3·H2O, nickel electrode, transferring the obtained mixture to a stainless steel reaction kettle. Then heated in an oven at 180 ℃ for 12 h. Naturally cooling to room temperature, taking out the substrate, washing with ethanol and water for 3 times respectively, and drying at 60 ℃ for 12 hours to obtain a graphene-coated nickel electrode;
(2) the preparation of the nickel-iron metal organic framework/graphene/nickel composite material is the same as example 1;
(3) preparation of nickel-iron oxide/graphene/nickel composite material as in example 1;
(4) the nickel-iron phosphide/graphene/nickel composite material was prepared as in example 1.
Example 8
(1) Preparation of graphene-coated nickel electrode as in example 1;
(2) the preparation of the nickel-iron metal organic framework/graphene/nickel composite material is the same as example 1;
(3) preparation of nickel-iron oxide/graphene/nickel composite (NiFeO/rGO/NF): calcining the NiFe MOF/rGO/NF prepared in the step for 1h at 800 ℃ in the air to obtain a nickel-iron oxide/graphene/nickel composite material;
(4) the nickel-iron phosphide/graphene/nickel composite material was prepared as in example 1.
Example 9
(1) Preparation of graphene-coated nickel electrode as in example 1;
(2) the preparation of the nickel-iron metal organic framework/graphene/nickel composite material is the same as example 1;
(3) preparation of nickel-iron oxide/graphene/nickel composite (NiFeO/rGO/NF): calcining the NiFe MOF/rGO/NF prepared in the step for 6 hours in the air at the temperature of 100 ℃ to obtain a nickel-iron oxide/graphene/nickel composite material;
(4) the nickel-iron phosphide/graphene/nickel composite material was prepared as in example 1.
Example 10
(1) Preparation of graphene-coated nickel electrode as in example 1;
(2) the preparation of the nickel-iron metal organic framework/graphene/nickel composite material is the same as example 1;
(3) preparation of nickel-iron phosphide/graphene/nickel composite electrode (NiFeP/rGO/NF): directly calcining the mixture in phosphine gas for 8 hours without the step 3 to obtain the nickel-iron phosphide/graphene/nickel composite material.
And (3) structural and performance characterization:
1. topographic structure
Fig. 1a is a scanning electron microscope image of the nickel electrode coated with graphene in example 1, and it can be clearly found that the graphene is coated on the surface of the flat nickel electrode to form an upright fish scale array structure, and the wrinkles form a pore structure of about 200 nm. FIGS. 1b-1d are scanning electron micrographs of the Ni-Fe metal organic framework/graphene/Ni composite, Ni-iron oxide/graphene/Ni composite, and Ni-iron phosphide/graphene/Ni composite, respectively, of example 1; the method can find that a nickel-iron metal organic framework grows on the surface of a graphene/nickel electrode to form a 20-50 nm mesoporous structure, a hierarchical pore structure is formed by the composite material due to a microporous structure of the metal organic framework, and the morphology of the material is not changed through calcination and phosphorization.
2. Structural characterization
FIG. 2a is an XRD spectrum of the Ni-Fe metal organic framework/graphene/Ni composite material in example 1, which is consistent with the structure of the metal organic framework; fig. 2b is the XRD spectrum of the nickel-iron oxide/graphene/nickel composite material and the nickel-iron phosphide/graphene/nickel composite material in example 1, and it can be seen that the main material of the material after the phosphine gas treatment is nickel phosphide.
3. Characterization of catalytic Properties
Fig. 3a is a polarization curve of a nickel electrode, a graphene-coated nickel electrode, a nickel-iron metal organic framework/graphene/nickel composite material, a nickel-iron oxide/graphene/nickel composite material, and a nickel-iron phosphide/graphene/nickel composite material in example 1 of the present invention, and fig. 3b is an electrochemical impedance curve graph of a nickel-iron phosphide/graphene/nickel composite material, from the polarization curve graph, it can be found that the conductivity of the material can be greatly enhanced after the nickel-iron metal organic framework structure grows on the surface of the graphene-coated nickel, a higher current density can be achieved under the same voltage, after the material is further calcined and phosphated, a maximum current density can be achieved under a very low overpotential, and good activity and conductivity of the material are fully demonstrated, and the electrochemical impedance graph proves that the electron transfer internal resistance of the material is only 1.98 omega.
Fig. 4a to 4b are stability test charts of the nickel-iron phosphide/graphene/nickel composite material in the alkaline environment and the saline-alkaline environment in example 1 of the present invention. The material can achieve 500h stability at lower current density and still has 120h stability in saline-alkali water environment. The performance test proves that the material has excellent electrochemical oxygen evolution activity and excellent stability.
In addition, the inventors of the present invention have also made experiments with other materials, process operations, and process conditions described in the present specification with reference to the above examples, and have obtained preferable results.
The aspects, embodiments, features and examples of the present invention should be considered as illustrative in all respects and not intended to be limiting of the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.
The use of headings and chapters in this disclosure is not meant to limit the disclosure; each section may apply to any aspect, embodiment, or feature of the disclosure.
Throughout this specification, where a composition is described as having, containing, or comprising specific components or where a process is described as having, containing, or comprising specific process steps, it is contemplated that the composition of the present teachings also consist essentially of, or consist of, the recited components, and the process of the present teachings also consist essentially of, or consist of, the recited process steps.
It should be understood that the order of steps or the order in which particular actions are performed is not critical, so long as the teachings of the invention remain operable. Further, two or more steps or actions may be performed simultaneously.
While the invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions and/or additions may be made and substantial equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated any use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.