Preparation method of a water splitting catalyst and the water splitting catalyst

Abstract

The present invention provides a preparation method of a water splitting catalyst and the water splitting catalyst. The preparation method of the water splitting catalyst of the present invention includes: 1) adding an acetic acid aqueous solution to a carbon source solution to obtain a gel ink; the carbon source solution includes chitosan and ZIF-67; 2) printing the gel ink by 3D printing to form a green body with periodically uniform pores; 3) crosslinking and curing the green body, and performing carbonization treatment on the crosslinked and cured green body to obtain a carbon composite material; 4) loading a transition metal phosphide onto the carbon composite material to obtain the water splitting catalyst. The water splitting catalyst prepared by the preparation method of the present invention has excellent hydrogen evolution reaction activity and oxygen evolution reaction activity and relatively high catalytic efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemistry, and relates to a preparation method of a water splitting catalyst and a water splitting catalyst. Background Art

[0002] Electrocatalytic water splitting for continuous hydrogen production is considered an efficient and environmentally friendly renewable resource strategy. The electrolysis water reaction consists of two half-reactions, namely the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. Both of these reactions require catalysts to improve the efficiency of water electrolysis and reduce the overpotential of the reaction. Currently, noble metal platinum-based and ruthenium-based nanocatalysts have high hydrogen evolution and oxygen evolution reaction activities, but the high cost and scarcity of noble metals have hindered their large-scale application in the field of water electrolysis. In recent years, a large number of low-cost transition metal sulfides, selenides, phosphides, carbides, nitrides, alloys, oxides, hydroxides, phosphates, etc. have been developed and applied to HER and OER. Among them, transition metal phosphides can not only capture protons during the HER process but also promote the formation of peroxides in OER, so they possess excellent hydrogen evolution and oxygen evolution activities.

[0003] Traditional water electrolysis catalysts include a conductive substrate and an active metal component supported on the conductive substrate. Numerous studies have shown that three-dimensional supported monolithic catalysts, in which the active metal component is in situ grown on a conductive substrate, are more suitable for demanding industrial requirements. The reasons are: first, the in situ growth of the active metal component on the conductive substrate avoids post-coating and the steps of adding binders and conductive agents, simplifying the catalyst preparation process and reducing costs; second, the conductive substrate material can rivet and disperse the active metal component, with a high active component loading rate, thus providing abundant catalytic sites; third, the active metal component is more tightly bonded to the conductive substrate, ensuring rapid charge transfer and preventing the active component from falling off. Common base materials for three-dimensional self-supporting monolithic catalysts mainly include carbon fiber paper, carbon cloth, graphite plate, metal foam (such as copper foam, nickel foam), metal mesh (such as titanium mesh, copper mesh), metal plate (such as titanium plate), metal foil (such as W / Mo / Cu foil), fluorine-doped tin oxide (FTO), etc. The above-mentioned base materials are loaded with catalytic active components through synthesis methods such as water / solvent thermal, electrodeposition, vapor deposition, vacuum filtration, and freeze drying to produce electrocatalytic materials. Carbon-based substrates, with their low density, high strength, high-temperature resistance, and excellent electrical conductivity, can be coupled with nanocatalysts through post-processing to form monolithic electrodes, demonstrating their potential for electrochemical applications. However, carbon-based materials are prone to delamination, burring, and tearing during processing, resulting in incomplete three-dimensional structures. Furthermore, the carbon-based substrate is not easily accessible to active components, making it difficult to guarantee the stability and activity of the resulting electrocatalysts.

[0004] Therefore, how to prepare a carbon-based catalyst for complete water splitting with high activity, high catalytic efficiency and excellent stability is a technical problem that needs to be solved urgently in this field. Summary of the invention

[0005] The present invention provides a method for preparing a complete water-splitting catalyst. The method uses 3D printing to prepare a carbon composite material, so that the carbon composite material has a unique and regular periodically distributed three-dimensional hierarchical multi-porous structure. The complete water-splitting catalyst prepared using the carbon composite material as a substrate has excellent catalytic efficiency and catalytic activity.

[0006] The present invention also provides a complete water splitting catalyst, which has excellent catalytic efficiency and catalytic activity in the complete water splitting reaction.

[0007] The first aspect of the present invention provides a method for preparing a complete water splitting catalyst, comprising the following steps:

[0008] 1) adding an aqueous acetic acid solution to a carbon source solution to obtain a gel ink; the carbon source solution includes chitosan and ZIF-67;

[0009] 2) Printing the gel ink by 3D printing to form a green body with periodically uniform pores;

[0010] 3) Crosslinking and curing the green body, and performing carbonization treatment on the crosslinked and cured green body to obtain a carbon composite material;

[0011] 4) Loading transition metal phosphide into the carbon composite material to obtain the overall water splitting catalyst.

[0012] The overall water splitting catalyst obtained by the above preparation method includes a carbon composite material substrate with a three-dimensional hierarchical porous structure and transition metal phosphide loaded in the carbon composite material substrate.

[0013] Among them, chitosan is a biopolymeric polysaccharide polymer obtained by deacetylating chitin. Chitin exists in the shells of invertebrates, the mycelia of fungi, protozoa, and some green algae, and has a very wide source. Chitosan is rich in nitrogen elements. When using chitosan as a carbon source to prepare a carbon composite material, some nitrogen elements will be retained after the carbon source is carbonized to obtain the carbon composite material, and the nitrogen elements in the carbon composite material can increase the pseudocapacitance of the material, thereby improving the electrochemical performance of the material. At the same time, chitosan also contains a large number of hydroxyl and amino groups. The hydroxyl and amino groups have a good chelating effect on transition metal ions, and can evenly disperse the metal active components inside the carbon composite material, so that the catalyst has excellent catalytic performance.

[0014] In addition to chitosan, ZIF-67 is also added to the carbon source solution. The chemical name of ZIF-67 is cobalt dimethylimidazole, which is a zeolite-like metal-organic framework material formed by the complexation of transition metal cobalt ions and imidazole ligands. It has the advantages of regular morphology and large specific surface area. As an auxiliary carbon source material, it can increase the specific surface area of the carbon composite material, so that the catalyst obtains more excellent catalytic performance. In addition, ZIF-67 can also be used as a pre-introduced metal cobalt salt, interacting with the later-attached nickel cobalt phosphide, enhancing the attachment strength of the nickel cobalt phosphide.

[0015] In step 1), an acetic acid aqueous solution is added to the carbon source solution. After acetic acid reacts with chitosan, the reaction system can form an ink with a gel form. The gel ink can form a green body with a three-dimensional hierarchical porous structure and uniform macroscopic pore distribution after 3D printing.

[0016] After crosslinking and curing the green body, the pore structure of the green body can be retained during subsequent processes such as high-temperature roasting, hydrothermal treatment, and phosphidation.

[0017] Specifically, crosslinking and curing can adopt conventional treatment means in the art. For example, soaking the green body in a 1mol / L potassium hydroxide solution for 30 minutes can complete the process of crosslinking and curing.

[0018] Then, the crosslinked and cured green embryo is carbonized to obtain a carbon composite material with a three-dimensional hierarchical porous structure.

[0019] In the present invention, a unique and regular periodically distributed three-dimensional porous hierarchical structure is imparted to the carbon composite material by means of 3D printing. The three-dimensional hierarchical porous structure spans three scales of micropores, mesopores, and macropores. Due to the synergistic effect of micropores, mesopores, and macropores, the carbon composite material of the present invention has more excellent mass transfer performance compared with traditional carbon materials. Specifically, the penetration rate of the electrolyte, the gas release rate, and the mass transfer rate of reaction intermediates are all significantly improved, so that the catalyst has higher catalytic efficiency and catalytic activity. At the same time, the carbon composite material formed by 3D printing has a larger specific surface area, and its specific surface area can reach 400 - 1400 m 2 / g, which can provide more active sites for the active components, and the loading rate of the active components can be as high as 15 wt%.

[0020] In the present invention, by loading transition metal phosphide on the above carbon composite material, a bulk integral overall water splitting catalyst can be formed. The catalyst can uniformly and firmly load the transition metal phosphide particles on the carbon composite material substrate without adding a binder and a polymer crosslinking agent. At the same time, the obtained overall water splitting catalyst has abundant pores, a large specific surface area, and a large number of active sites, so that the catalyst has more excellent catalytic performance and catalytic efficiency. In 1 mol / L KOH solution and at a current density of 10 mA / cm 2 , the overpotentials of the hydrogen evolution and oxygen evolution reactions can be as low as 57 mV and 163 V, respectively. The overpotential of the hydrogen evolution reaction can be maintained for nearly 1000 h, and the overpotential of the oxygen evolution reaction can be maintained for 75 h without obvious change, showing good market application prospects.

[0021] In the preparation of the carbon composite material, the 3D printing process in step 2) satisfies the following parameters: the diameter of the printing nozzle for 3D printing is 1 mm, the printing speed is 3.0 - 10.0 mm / s, and the extrusion speed is 1.0 - 10.0 mm 3 / s;

[0022] Preferably, the printing speed is 5.0 mm / s and the extrusion speed is 3.0 mm 3 / s.

[0023] The printed size of the green embryo obtained by 3D printing is 30 mm × 30 mm × 6 mm, the printing layer height is 1 - 3 mm, and the printing method is one of the three filling and routing methods of [0°, 90°], [0°, 45°, 90°], and [0°, 30°, 60°];

[0024] Preferably, the printing layer height is 2 mm.

[0025] By any one of the three filling and routing methods of [0°, 90°], [0°, 45°, 90°], and [0°, 30°, 60°], a carbon composite material with periodically vertically oriented microchannels can be formed. Compared with nickel foam with a disordered structure, the vertically oriented pore structure formed by 3D printing is more conducive to the drainage process and inhibits the aggregation of bubbles.

[0026] Furthermore, the transition metal phosphide of the present invention is selected from nickel-cobalt bimetallic phosphides. Although noble metals such as Ru and Ir have stable and excellent hydrogen evolution and oxygen evolution reaction activities, the storage amount of noble metal materials is limited and the price is high, making large-scale production impossible. Compared with noble metals, nickel-cobalt compounds also have high stability and catalytic activity, can further reduce the reaction cost, and have better market application prospects.

[0027] Furthermore, in the carbon source solution, the mass ratio of ZIF-67 to chitosan is (0.01 - 0.15):1.

[0028] In a specific embodiment, the carbon source solution further includes raffinose, anhydrous calcium chloride, and / or a surfactant.

[0029] Adding anhydrous calcium chloride can inhibit the degradation of the molecular chain of chitosan in an acidic solution and ensure that the viscosity of the gel ink is controllable during the printing process. Under acidic conditions, the natural trisaccharide raffinose has good thermal stability, can balance the degradation rate of chitosan in acetic acid and its cross-linking rate with calcium chloride, and inhibits the degradation of chitosan by a dynamic equilibrium method to ensure controllable extrusion of the gel ink.

[0030] The surfactant as a templating agent can not only increase the specific surface area of the prepared carbon composite material, but also increase the pores on the carbon composite material substrate where the transition metal component can adhere, enabling the overall water splitting catalyst to have better catalytic performance. Specifically, the surfactant can be selected from poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (P 123 ), poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) triblock copolymer (F 127 ), and PEO-PPO-PEO poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (F 108 ), etc.

[0031] The carbonization treatment in the preparation process of the carbon composite material can adopt the commonly used carbonization treatment process in the art. For example, the temperature of the cross-linked and cured green body is raised from room temperature to 800 - 900 °C at a heating rate of 1 - 10 °C / min, and this temperature is maintained for 1 - 4 h to complete the carbonization process.

[0032] After the carbonization treatment is completed, the green body after carbonization treatment can be further subjected to pickling treatment. Specifically, the green body after carbonization treatment can be placed in a 2 mol / L dilute hydrochloric acid solution and soaked for 5 min to complete the pickling treatment process. Through the pickling treatment, the size of large Co nanoparticles can be greatly reduced, and the overall particle size distribution of large particles can be made uniform.

[0033] In a specific embodiment, step 4) includes: dispersing a salt solution of a transition metal and an alkali source in deionized water to obtain a mixed solution; adding a carbon composite material to the mixed solution and performing hydrothermal treatment at 100-200 °C; subjecting the product of the hydrothermal treatment to a phosphating reaction to obtain the overall water splitting catalyst.

[0034] The inventors have found through research that by controlling the hydrothermal synthesis to be carried out at a relatively low temperature of 100-200 °C, a catalyst with a transition metal phosphide size of 1.8-3.4 nm can be obtained. The smaller the particle size of the active component, the larger the specific surface area of the catalyst, which is more conducive to improving the catalytic activity of the catalyst.

[0035] Taking the transition metal phosphide being a nickel-cobalt bimetallic phosphide as an example, the above loading process includes: subjecting the carbon composite material to hydrothermal treatment with a mixed solution of a cobalt salt, a nickel salt and an alkali source, and then reacting the hydrothermal treatment product with sodium hypophosphite to obtain an overall water splitting catalyst with nickel-cobalt bimetallic phosphide loaded on a carbon composite material substrate.

[0036] Specifically, the cobalt salt is selected from at least one of cobalt nitrate, cobalt chloride or cobalt acetate, the nickel salt is selected from at least one of nickel nitrate, nickel chloride, nickel acetate, and the molar ratio of the cobalt salt to the nickel salt is 2:1; the alkali salt can be selected from at least one of urea, ammonium fluoride, sodium citrate and hexamethylenetetramine.

[0037] The second aspect of the present invention provides an overall water splitting catalyst, which is prepared by the preparation method provided in the first aspect of the present invention.

[0038] The overall water splitting catalyst prepared by the above method has rich pores, a large specific surface area and a large number of exposed active sites, and shows excellent catalytic activity and catalytic efficiency when applied to the overall water splitting reaction.

[0039] The implementation of the present invention has at least the following advantages:

[0040] 1. The preparation method of the overall water splitting catalyst provided by the present invention introduces 3D printing technology into the preparation of carbon composites, enabling the carbon composites to have a unique and regular three-dimensional hierarchical porous channel structure with periodic distribution. At the same time, transition metal phosphide particles are firmly loaded on the carbon composites to obtain a large-sized integral catalyst. This catalyst has abundant pores, a large specific surface area, and a large number of exposed active sites. When applied to the overall water splitting reaction, it exhibits excellent catalytic activity and catalytic efficiency. In 1 mol / L KOH solution and at a current density of 10 mA / cm 2 the overpotentials of the hydrogen evolution reaction and oxygen evolution reaction can be as low as 57 mV and 163 V respectively. At a large current density of 500 mA / cm 2 the overpotential of the hydrogen evolution reaction is 266 mV. At the same time, when the current density reaches 10 mA / cm 2 the cell voltage of the alkaline electrolyzer is only 1.43 V. The hydrogen evolution reaction of this overall water splitting catalyst in 1 mol / L KOH solution and at a current density of 10 mA / cm 2 the overpotential of the hydrogen evolution reaction can remain stable for nearly 1000 h, and the overpotential of the oxygen evolution reaction can remain stable for more than 75 h without obvious changes, showing good market application prospects.

[0041] 2. The overall water splitting catalyst provided by the present invention is prepared by the above preparation method, and this catalyst has excellent catalytic efficiency and catalytic activity. Brief Description of the Drawings

[0042] Figure 1 is the X-ray diffraction pattern of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1;

[0043] Figure 2a is the SEM image of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1;

[0044] Figure 2b is the EDX image of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1;

[0045] Figure 2c is the elemental surface distribution map of C, Co, Ni, P, N, and O of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1;

[0046] Figure 3a is the high-magnification transmission electron microscopy (TEM) image of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1;

[0047] Figure 3b is the particle size statistical chart of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1;

[0048] Figure 3c High-magnification transmission electron microscopy (TEM) lattice fringe image of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1;

[0049] Figure 4a Ni 2p X-ray photoelectron spectroscopy of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1;

[0050] Figure 4b Co 2p X-ray photoelectron spectroscopy of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1;

[0051] Figure 4c P 2p X-ray photoelectron spectroscopy of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1;

[0052] Figure 5a Isothermal adsorption curve comparison diagram of the overall water splitting catalysts prepared in Example 1 and Examples 4-8;

[0053] Figure 5b Mesoporous pore size distribution comparison diagram of the overall water splitting catalysts prepared in Example 1 and Examples 4-8;

[0054] Figure 6a Hydrogen evolution reaction polarization curve comparison diagram of the overall water splitting catalyst prepared in Example 1;

[0055] Figure 6b Oxygen evolution reaction polarization curve comparison diagram of the overall water splitting catalyst prepared in Example 1;

[0056] Figure 6c Tafel curve of hydrogen evolution reaction of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1;

[0057] Figure 6d Tafel curve of oxygen evolution reaction of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1;

[0058] Figure 6e Overall water splitting polarization curve of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1;

[0059] Figure 6f Hydrogen evolution reaction chronopotentiometry analysis curve of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1 in 1 mol / L KOH solution at a current density of 10 mA / cm 2 ;

[0060] Figure 6g Chronopotentiometry analysis curve of the oxygen evolution reaction of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1 in 1 mol / L KOH solution at a current density of 10 mA / cm 2 . Detailed implementation manners

[0061] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0062] It should be noted that in the following embodiments, unless otherwise specified, the raw materials used can be obtained through commercial purchase or conventional methods, and the experimental methods without specific conditions mentioned are all conventional methods and conventional conditions well known in the art.

[0063] Example 1

[0064] The preparation of the overall water splitting catalyst in this example includes the following steps:

[0065] 1) 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride are dispersed in deionized water, and then 0.023 g of ZIF-67 is added according to the mass ratio of ZIF-67 to chitosan of 0.05:1. After uniform dispersion, 1.0 g of P 123 and 0.5 g of acetic acid aqueous solution (concentration: 36 wt%) are added to prepare a gel ink. The gel ink is 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve cross-linking and curing, and then the cross-linked and cured green body is rinsed with ethanol and deionized water, and dried at room temperature for 18 h;

[0066] Among them, the 3D printing parameters are: printing nozzle diameter 1 mm, printing speed 2.0 mm / s, extrusion speed 5.0 mm 3 / s, the printing method is [0°, 90°] filling wire laying method, the size of the printed green body is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0067] 2) The dried green body is heated from room temperature to 800 °C at a heating rate of 2 °C / min and held for 2 h for carbonization treatment, and then soaked in 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0068] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea, and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing evenly, add the carbon composite material prepared in step 2), and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of the porcelain boat and sodium hypophosphite at the end of the porcelain boat, and react them together under a nitrogen atmosphere in a tube furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC.

[0069] Example 2

[0070] The preparation of the water splitting catalyst in this example includes the following steps:

[0071] 1) Disperse 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride in deionized water. Then add 0.0158 g of ZIF-67 according to the mass ratio of ZIF-67 to chitosan of 0.03:1. After dispersing evenly, add 0.5 g of acetic acid aqueous solution (concentration 36 wt%), and prepare a gel ink. The gel ink is 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve cross-linking and curing, and then the cross-linked and cured green body is rinsed with ethanol and deionized water and dried at room temperature for 18 h.

[0072] Among them, the parameters of 3D printing are: the diameter of the printing nozzle is 1 mm, the printing speed is 2.0 mm / s, the extrusion speed is 3.0 mm 3 / s, the printing method is the [0°, 90°] filling and routing method, the size of the printed green body is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0073] 2) Heat the dried green body from room temperature to 800 °C at a heating rate of 2 °C / min and keep it for 2 h for carbonization treatment, and then soak it in 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0074] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea, and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing, add the carbon composite material prepared in step 2), and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of the porcelain boat and sodium hypophosphite at the end of the porcelain boat, and react them together under a nitrogen atmosphere in a tubular furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC-2.

[0075] Example 3

[0076] The preparation of the water splitting catalyst in this example includes the following steps:

[0077] 1) Disperse 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride in deionized water. Then, add 0.042 g of ZIF-67 according to the mass ratio of ZIF-67 to chitosan of 0.08:1. After uniform dispersion, add 0.5 g of acetic acid aqueous solution (concentration 36 wt%), and prepare a gel ink. The gel ink is 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve cross-linking and curing, and then the cross-linked and cured green body is rinsed with ethanol and deionized water and dried at room temperature for 18 h.

[0078] Among them, the parameters of 3D printing are: the diameter of the printing nozzle is 1 mm, the printing speed is 2.0 mm / s, the extrusion speed is 8.0 mm 3 / s, the printing method is the [0°, 90°] filling and routing method, the size of the printed green body is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0079] 2) The dried green body is carbonized at a heating rate of 2 °C / min from room temperature to 800 °C and kept for 2 h, and then soaked in 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0080] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea, and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing until homogeneous, add the carbon composite material prepared in step 2), and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of a porcelain boat and sodium hypophosphite at the end of the porcelain boat. React them together in a nitrogen atmosphere in a tube furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC-3.

[0081] Example 4

[0082] The preparation of the water splitting catalyst in this example includes the following steps:

[0083] 1) Disperse 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride in deionized water. Then, add 0.0263 g of ZIF-67 according to the mass ratio of ZIF-67 to chitosan of 0.05:1. After dispersion until homogeneous, add 0.2 g of P 123 and 0.5 g of acetic acid aqueous solution (concentration: 36 wt%) to prepare a gel ink. The gel ink is 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve cross-linking and curing, and then the cross-linked and cured green body is rinsed with ethanol and deionized water and dried at room temperature for 18 h;

[0084] Among them, the parameters of 3D printing are: the diameter of the printing nozzle is 1 mm, the printing speed is 2.0 mm / s, the extrusion speed is 5.0 mm 3 / s, the printing method is the [0°, 90°] filling and routing method, the size of the printed green body is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0085] 2) Heat the dried green body from room temperature to 800 °C at a heating rate of 2 °C / min and keep it for 2 h for carbonization treatment, and then soak it in a 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0086] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea, and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing, add the carbon composite material prepared in step 2), and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of the porcelain boat and sodium hypophosphite at the end of the porcelain boat, and react them together under a nitrogen atmosphere in a tube furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC-4.

[0087] Example 5

[0088] The preparation of the water splitting catalyst in this example includes the following steps:

[0089] 1) Disperse 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride in deionized water, and then add 0.0263 g of ZIF-67 according to the mass ratio of ZIF-67 to chitosan of 0.05:1. After uniform dispersion, add 0.5 g of P 123 and 0.5 g of acetic acid aqueous solution (concentration: 36 wt%) to prepare a gel ink. The gel ink is 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve cross-linking and curing, and then the cross-linked and cured green body is rinsed with ethanol and deionized water and dried at room temperature for 18 h;

[0090] Among them, the parameters of 3D printing are: the diameter of the printing nozzle is 1 mm, the printing speed is 2.0 mm / s, the extrusion speed is 4.0 mm 3 / s, the printing method is [0°, 90°] filling and routing method, the size of the printed green body is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0091] 2) Heat the dried green body from room temperature to 800 °C at a heating rate of 2 °C / min and keep it for 2 h for carbonization treatment, and then soak it in 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0092] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea, and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing, add the carbon composite material prepared in step 2), and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of the porcelain boat and sodium hypophosphite at the end of the porcelain boat, and react them together in a nitrogen atmosphere in a tubular furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC-5.

[0093] Example 6

[0094] The preparation of the water splitting catalyst in this example includes the following steps:

[0095] 1) Disperse 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride in deionized water, and then add 0.0263 g of ZIF-67 according to the mass ratio of ZIF-67 to chitosan of 0.05:1. After uniform dispersion, add 1.5 g of P 123 and 0.5 g of acetic acid aqueous solution (concentration 36 wt%) to prepare a gel ink. The gel ink is 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve crosslinking and curing, and then the crosslinked and cured green body is rinsed with ethanol and deionized water and dried at room temperature for 18 h;

[0096] Among them, the parameters of 3D printing are: the diameter of the printing nozzle is 1 mm, the printing speed is 2.0 mm / s, the extrusion speed is 2.0 mm 3 / s, the printing method is [0°, 90°] filling wire routing method, the size of the printed green body is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0097] 2) Heat the dried green body from room temperature to 800 °C at a heating rate of 2 °C / min and keep it for 2 h for carbonization treatment, and then soak it in 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0098] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea, and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing, add the carbon composite material prepared in step 2), and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of the porcelain boat and sodium hypophosphite at the end of the porcelain boat, and react them together in a nitrogen atmosphere in a tube furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC-6.

[0099] Example 7

[0100] The preparation of the water splitting catalyst in this example includes the following steps:

[0101] 1) Disperse 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride in deionized water, and then add 0.0263 g of ZIF-67 according to the mass ratio of ZIF-67 to chitosan of 0.05:1. After uniform dispersion, add 2.0 g of P 123 and 0.5 g of acetic acid aqueous solution (concentration 36 wt%) to prepare a gel ink. The gel ink is 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve crosslinking and curing, and then the crosslinked and cured green body is rinsed with ethanol and deionized water and dried at room temperature for 18 h;

[0102] Among them, the parameters of 3D printing are: the diameter of the printing nozzle is 1 mm, the printing speed is 2.0 mm / s, the extrusion speed is 1.0 mm 3 / s, the printing method is the [0°, 90°] filling and routing method, the size of the printed green body is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0103] 2) Heat the dried green body from room temperature to 800 °C at a heating rate of 2 °C / min and keep it for 2 h for carbonization treatment, and then soak it in 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0104] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea, and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing evenly, add the carbon composite material prepared in step 2), and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of a porcelain boat and sodium hypophosphite at the end of the porcelain boat. React them together in a nitrogen atmosphere in a tube furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC-7.

[0105] Example 8

[0106] The preparation of the water splitting catalyst in this example includes the following steps:

[0107] 1) Disperse 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride in deionized water. Then add 0.0263 g of ZIF-67 according to the mass ratio of ZIF-67 to chitosan of 0.05:1. After dispersing evenly, add 0.5 g of acetic acid aqueous solution (concentration 36 wt%), and prepare a gel ink. The gel ink is 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve cross-linking and curing. Then rinse the cross-linked and cured green body with ethanol and deionized water, and dry it at room temperature for 18 h;

[0108] Among them, the parameters of 3D printing are: the diameter of the printing nozzle is 1 mm, the printing speed is 2.0 mm / s, the extrusion speed is 9.0 mm 3 / s, the printing method is the [0°, 90°] filling and routing method, the size of the printed green body is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0109] 2) Heat the dried green body from room temperature to 800 °C at a heating rate of 2 °C / min and keep it for 2 h for carbonization treatment, and then soak it in 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0110] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea, and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing, add the carbon composite material prepared in step 2), and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of the porcelain boat and sodium hypophosphite at the end of the porcelain boat, and react them together under a nitrogen atmosphere in a tubular furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC-8.

[0111] Example 9

[0112] The preparation of the water splitting catalyst in this example includes the following steps:

[0113] 1) Disperse 0.5250 g of chitosan in deionized water, then add 0.023 g of ZIF-67 according to the mass ratio of ZIF-67 to chitosan of 0.05:1. After uniform dispersion, add 1.0 g of P 123 and 0.5 g of acetic acid aqueous solution (concentration 36 wt%) to prepare a gel ink. The gel ink is 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve crosslinking and curing, and then the crosslinked and cured green body is rinsed with ethanol and deionized water, and dried at room temperature for 18 h;

[0114] Among them, the 3D printing parameters are: printing nozzle diameter 1 mm, printing speed 2.0 mm / s, extrusion speed 5.0 mm 3 / s, the printing method is [0°, 90°] filling and routing method, the size of the printed green body is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0115] 2) Heat the dried green body from room temperature to 800 °C at a heating rate of 2 °C / min and keep it for 2 h for carbonization treatment, and then soak it in 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0116] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea, and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing evenly, add the carbon composite material prepared in step 2), and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of the porcelain boat and sodium hypophosphite at the end of the porcelain boat. React them together under a nitrogen atmosphere in a tube furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC-9.

[0117] Example 10

[0118] The preparation of the water splitting catalyst in this example includes the following steps:

[0119] 1) Disperse 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride in deionized water. Then add 0.023 g of ZIF-67 according to the mass ratio of ZIF-67 to chitosan of 0.05:1. After dispersing evenly, add 1.0 g of F 127 and 0.5 g of acetic acid aqueous solution (concentration 36 wt%) to prepare a gel ink. The gel ink is 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve crosslinking and curing, and then the crosslinked and cured green body is rinsed with ethanol and deionized water, and dried at room temperature for 18 h after rinsing;

[0120] Among them, the parameters of 3D printing are: the diameter of the printing nozzle is 1 mm, the printing speed is 2.0 mm / s, the extrusion speed is 5.0 mm 3 / s, the printing method is [0°, 90°] filling and routing method, the size of the printed green body is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0121] 2) Heat the dried green body from room temperature to 800 °C at a heating rate of 2 °C / min and keep it for 2 h for carbonization treatment, and then soak it in 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0122] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea, and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing until homogeneous, add the carbon composite material prepared in step 2), and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of a porcelain boat and sodium hypophosphite at the end of the porcelain boat, and react them together under a nitrogen atmosphere in a tubular furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC-10.

[0123] Example 11

[0124] The preparation of the water splitting catalyst in this example includes the following steps:

[0125] 1) Disperse 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride in deionized water, and then add 0.023 g of ZIF-67 according to the mass ratio of ZIF-67 to chitosan of 0.05:1. After dispersing evenly, add 1.0 g of P 123 and 0.5 g of acetic acid aqueous solution (concentration 36 wt%) to prepare a gel ink. The gel ink is 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve cross-linking and curing, and then the cross-linked and cured green body is rinsed with ethanol and deionized water, and dried at room temperature for 18 h after rinsing;

[0126] Among them, the parameters of 3D printing are: the diameter of the printing nozzle is 1 mm, the printing speed is 2.0 mm / s, the extrusion speed is 5.0 mm 3 / s, the printing method is the [0°, 45°, 90°] filling wire routing method, the size of the printed green body is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0127] 2) Heat the dried green body from room temperature to 800 °C at a heating rate of 2 °C / min and keep it for 2 h for carbonization treatment, and then soak it in 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0128] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea, and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing, add the carbon composite material prepared in step 2), and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of the porcelain boat and sodium hypophosphite at the end of the porcelain boat, and react them together in a nitrogen atmosphere in a tube furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and held at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC-11.

[0129] Example 12

[0130] The preparation of the water splitting catalyst in this example includes the following steps:

[0131] 1) Disperse 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride in deionized water, and then add 0.023 g of ZIF-67 according to the mass ratio of ZIF-67 to chitosan of 0.05:1. After uniform dispersion, add 1.0 g of P 123 and 0.5 g of acetic acid aqueous solution (concentration 36 wt%) to prepare a gel ink. The gel ink is 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve crosslinking and curing, and then the crosslinked and cured green body is rinsed with ethanol and deionized water, and dried at room temperature for 18 h;

[0132] Among them, the parameters of 3D printing are: the diameter of the printing nozzle is 1 mm, the printing speed is 2.0 mm / s, the extrusion speed is 5.0 mm 3 / s, the printing method is [0°, 90°] filling and routing method, the size of the printed green body is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0133] 2) The dried green body is carbonized at a heating rate of 2 °C / min from room temperature to 800 °C and held for 2 h to obtain a carbon composite material.

[0134] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing evenly, add the carbon composite material prepared in step 2), and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of the porcelain boat and sodium hypophosphite at the end of the porcelain boat. The two are reacted together in a nitrogen atmosphere in a tubular furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC-12.

[0135] Comparative Example 1

[0136] The preparation of the water splitting catalyst in this comparative example includes the following steps:

[0137] 1) Disperse 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride in deionized water. Then add 0.023 g of ZIF-67 according to the mass ratio of ZIF-67 to chitosan of 0.05:1. After dispersing evenly, add 1.0 g of P 123 and 0.5 g of acetic acid aqueous solution (concentration 36 wt%) to prepare a gel ink. Put the gel ink into a fixed mold to make a three-dimensional green body, soak it in 1 mol / L potassium hydroxide for 30 min to achieve curing, and then rinse the cured green body with ethanol and deionized water. After rinsing, dry it at room temperature for 18 h.

[0138] 2) Carbonize the dried green body by heating it from room temperature to 800 °C at a heating rate of 2 °C / min and holding for 2 h, and then soak it in 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0139] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing evenly, add the carbon composite material prepared in step 2), and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of the porcelain boat and sodium hypophosphite at the end of the porcelain boat. The two are reacted together in a nitrogen atmosphere in a tubular furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / NC.

[0140] Comparative Example 2

[0141] The preparation of the water splitting catalyst in this comparative example includes the following steps:

[0142] 1) Dissolve 0.5250 g of glucose, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride in deionized water. Then, add 0.023 g of ZIF-67 according to a mass ratio of ZIF-67 to chitosan of 0.05:1. After dispersing evenly, add 1.0 g of P 123 and 0.5 g of acetic acid aqueous solution (concentration: 36 wt%) to prepare a gel ink. The gel ink is made into a green body with periodically uniform pores by 3D printing, soaked in 1 mol / L potassium hydroxide for 30 min to achieve cross-linking and curing, and then the cross-linked and cured green body is rinsed with ethanol and deionized water and dried at room temperature for 18 h;

[0143] Among them, the parameters of 3D printing are: the diameter of the printing nozzle is 1 mm, the printing speed is 2.0 mm / s, the extrusion speed is 5.0 mm 3 / s, the printing method is the [0°, 90°] filling and routing method, the size of the printed green body is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0144] 2) Heat the dried green body from room temperature to 800 °C at a heating rate of 2 °C / min and hold for 2 h for carbonization treatment, and then soak it in 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0145] 3) Disperse 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea, and 0.0620 g of ammonium fluoride in deionized water. After ultrasonic mixing evenly, add the carbon composite material prepared in step 2) and perform hydrothermal treatment at 120 °C for 2 h to obtain a nickel-cobalt precursor. Place the nickel-cobalt precursor at the front end of the porcelain boat and sodium hypophosphite at the end of the porcelain boat, and react them together under a nitrogen atmosphere in a tubular furnace. The reaction system is heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPC.

[0146] Comparative Example 3

[0147] The preparation of the water splitting catalyst in this comparative example includes the following steps:

[0148] 1) Disperse 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride in deionized water, and then add 1.0 g of P 1230.5 g of aqueous acetic acid solution (concentration: 36 wt%) was used to prepare a gel ink. The gel ink was 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve crosslinking and curing, and then the crosslinked and cured green body was rinsed with ethanol and deionized water and dried at room temperature for 18 h;

[0149] Among them, the parameters of 3D printing were as follows: the diameter of the printing nozzle was 1 mm, the printing speed was 2.0 mm / s, the extrusion speed was 5.0 mm 3 / s, the printing method was [0°, 90°] filling and routing method, the size of the printed green body was 30 mm × 30 mm × 6 mm, and the printing layer height was 2 mm.

[0150] 2) The dried green body was heated from room temperature to 800 °C at a heating rate of 2 °C / min and held for 2 h for carbonization treatment, and then soaked in 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0151] 3) 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt was 2:1), 0.0620 g of urea and 0.0620 g of ammonium fluoride were dispersed in deionized water. After ultrasonic mixing, the carbon composite material prepared in step 2) was added, and hydrothermal treatment was carried out at 120 °C for 2 h to obtain a nickel-cobalt precursor. The nickel-cobalt precursor was placed at the front end of the porcelain boat, and sodium hypophosphite was placed at the end of the porcelain boat. The two were reacted together under a nitrogen atmosphere in a tubular furnace. The reaction system was heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC-15.

[0152] Comparative Example 4

[0153] The preparation of the water splitting catalyst in this comparative example included the following steps:

[0154] 1) 0.5250 g of chitosan, 0.0905 g of raffinose, and 0.0540 g of anhydrous calcium chloride were dispersed in deionized water, and then 0.023 g of ZIF-67 was added according to the mass ratio of ZIF-67 to chitosan of 0.05:1. After uniform dispersion, 1.0 g of F 127 and 0.5 g of 0.5 mol / L dilute hydrochloric acid solution were used to prepare a gel ink. The gel ink was 3D printed into a green body with periodically uniform pores, soaked in 1 mol / L potassium hydroxide for 30 min to achieve crosslinking and curing, and then the crosslinked and cured green body was rinsed with ethanol and deionized water and dried at room temperature for 18 h;

[0155] Among them, the parameters of 3D printing are as follows: the diameter of the printing nozzle is 1 mm, the printing speed is 2.0 mm / s, the extrusion speed is 10.0 mm 3 / s, the printing method is the [0°, 90°] filling wire routing method, the size of the green body obtained by printing is 30 mm × 30 mm × 6 mm, and the printing layer height is 2 mm.

[0156] 2) The dried green body was heated from room temperature to 800 °C at a heating rate of 2 °C / min and held for 2 h for carbonization treatment, and then soaked in a 2 mol / L hydrochloric acid solution for 5 min to obtain a carbon composite material.

[0157] 3) 0.2910 g of cobalt nitrate hexahydrate, 0.1450 g of nickel nitrate hexahydrate (the molar ratio of cobalt salt to nickel salt is 2:1), 0.0620 g of urea and 0.0620 g of ammonium fluoride were dispersed in deionized water. After ultrasonic mixing, the carbon composite material prepared in step 2) was added, and hydrothermal treatment was carried out at 120 °C for 2 h to obtain a nickel-cobalt precursor. The nickel-cobalt precursor was placed at the front end of the porcelain boat, and sodium hypophosphite was placed at the end of the porcelain boat. The two were reacted together in a nitrogen atmosphere in a tubular furnace. The reaction system was heated from room temperature to 350 °C at a heating rate of 2 °C / min and kept at a constant temperature for 2 h to obtain a water splitting catalyst, named Ni-Co-P / 3DPNC-16.

[0158] Test Example

[0159] 1. Characterization of the structure of the water splitting catalyst

[0160] A. X-ray diffraction analysis

[0161] Figure 1 Figure 21 is the X-ray diffraction pattern of the Ni-Co-P / 3DPNC water splitting catalyst prepared in Example 1. The XRD pattern of the composite material Ni-Co-P / 3DPNC shows specific peaks composed of NiP2 (PDF = 13-0213) and Ni5P4 (PDF = 18-0883). At the same time, there are corresponding sharp characteristic diffraction peaks formed by hexagonal CoP3 (PDF = 29-0496). Therefore, the diffraction peaks in the XRD pattern of Ni-Co-P / 3DPNC are obviously those of a crystal mixture related to the Ni-P (NiP2 and Ni5P4) and Co-P (CoP3) phases. Therefore, it is determined that nickel cobalt phosphide has been successfully grown in-situ on the carbon composite substrate.

[0162] B. SEM, EDX, and EDS analysis

[0163] Figure 2a Figure 28 is the SEM image of the Ni-Co-P / 3DPNC water splitting catalyst prepared in Example 1. From Figure 2aIt can be seen that a carbon-based catalyst with periodic hierarchical pores was successfully formed by 3D printing.

[0164] Figure 2b Figure EDX of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1. It can be seen from Figure 2b that the prepared Ni-Co-P / 3DPNC overall water splitting catalyst has successfully adhered elements such as Ni, Co, and P.

[0165] Figure 2c Figure elemental mapping of C, Co, Ni, P, N, and O of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1. It can be seen from Figure 2c that Ni, Co, and P are uniformly dispersed on the Ni-Co-P / 3DPNC overall water splitting catalyst.

[0166] C, High-resolution transmission electron microscopy analysis

[0167] Figure 3a Figure high-resolution transmission electron microscopy (TEM) of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1. It can be seen from Figure 3a it that both large particles and small particles exist in the formed Ni-Co-P / 3DPNC overall water splitting catalyst, and the small particles are uniformly dispersed around the large particles.

[0168] Figure 3b Figure particle size statistical chart of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1. It can be seen from Figure 3b that the average particle size of the small particles is 2.61 nm.

[0169] Figure 3c Figure high-resolution transmission electron microscopy (TEM) lattice fringe pattern of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1. It can be seen from Figure 3c it that the large particles are cobalt oxides.

[0170] D, X-ray photoelectron spectroscopy analysis

[0171] In the present invention, the existence of Ni, Co, and P was further verified by X-ray photoelectron spectroscopy.

[0172] Among them, Figure 4a Figure Ni 2p X-ray photoelectron spectrum of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1. It can be seen from Figure 4a it that the Ni 2p spectrum shows that two obvious peaks at 856.92 and 875.54 eV respectively belong to Ni 2p3 / 2 and Ni 2p1 / 2.

[0173] Figure 4b X-ray photoelectron spectroscopy (XPS) spectrum of Co 2p for the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1. It can be seen from Figure 4b the spectrum that the Co 2p spectrum shows that the two obvious peaks at 779.39 and 798.50 eV belong to Co 2p3 / 2 and Co 2p1 / 2, respectively.

[0174] Figure 4c X-ray photoelectron spectroscopy (XPS) spectrum of P 2p for the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1. It can be seen from Figure 4c the spectrum that the P 2p spectrum shows that there are two obvious peaks at 134.32 eV and 129.96 eV. The lower binding energy (BE) peak corresponds to metal phosphide, and the other reflects the surface oxidized metal phosphate species, which is due to the exposure of surface Ni-Co-P to air.

[0175] E. Analysis of specific surface adsorption curves

[0176] Figure 5a Comparison diagram of isothermal adsorption curves of the overall water splitting catalysts prepared in Example 1 and Examples 4-8. It can be seen from Figure 5a the diagram that all samples show type IV isotherms and H4-type hysteresis loops (multilayer adsorption and capillary condensation), which are characteristics of mesoporous materials with slit-shaped pores.

[0177] According to Figure 5a the information in, the pore structure data of the overall water splitting catalysts prepared in Example 1 and Examples 4-8 are statistically obtained, and the specific data are shown in Table 1.

[0178] Table 1

[0179]

[0180] It can be seen from Table 1 that the periodically layered porous carbon-based nickel cobalt phosphide overall water splitting catalyst prepared by the preparation method of the present invention has a large specific surface area, spanning three scales of micropores, mesopores and macropores. Due to the synergistic effect of the three, the carbon composite material has more excellent mass transfer performance than traditional carbon materials.

[0181] Figure 5b Comparison diagram of mesopore size distributions of the overall water splitting catalysts prepared in Example 1 and Examples 4-8. It can be seen from Figure 5b the diagram that the most probable pore size is 2-4 nm.

[0182] 2. Electrochemical catalytic activity evaluation of hydrogen evolution reaction and oxygen evolution reaction of overall water splitting catalyst

[0183] A. Testing of overpotentials of hydrogen evolution reaction and oxygen evolution reaction

[0184] Testing method: The overall water splitting catalysts prepared in Examples 1-12 and Comparative Examples 1-4 were directly used as the working electrodes and immersed in 1.0 mol / L KOH solution to conduct linear sweep voltammetry tests for hydrogen evolution and oxygen evolution respectively, and the overpotentials of hydrogen evolution reaction and oxygen evolution reaction at a current density of 10 mA / cm 2 were recorded. The test results are shown in Table 2.

[0185] Table 2

[0186]

[0187]

[0188] It can be seen from Table 2 that the overall water splitting catalysts in Examples 1-12 have more excellent overall water splitting performance than those in Comparative Examples 1-4. Among them, the performance of the overall water splitting catalyst in Example 1 is the most excellent, and the overpotentials of hydrogen evolution reaction and oxygen evolution reaction are the lowest, which are 57 mV and 163 mV respectively.

[0189] B. Plotting of polarization curves for hydrogen evolution reaction and oxygen evolution reaction

[0190] Figure 6a Figure for comparing polarization curves of hydrogen evolution reaction for the overall water splitting catalyst prepared in Example 1 Figure 6b Figure for comparing polarization curves of oxygen evolution reaction prepared in Example 1. It can be seen from Figure 6a and Figure 6b that the overall water splitting catalyst prepared under the conditions of Example 1 has excellent hydrogen evolution and oxygen evolution performance.

[0191] C. Plotting of Tafel curves for hydrogen evolution reaction and oxygen evolution reaction

[0192] Figure 6c Figure of Tafel curve for hydrogen evolution reaction of Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1 Figure 6d Figure of Tafel curve for oxygen evolution reaction of Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1. It can be seen from Figure 6c and Figure 6d that the Tafel slope (34 mV / dec) of Example 1 is close to that of Pt / C (33 mV / dec). This is because the optimized combination of Ni, Co and P can effectively adjust the electronic properties of the material surface, thereby improving the activity and quantity of acceptor centers and being more conducive to the adsorption of H.

[0193] D. Plotting of overall water splitting polarization curve

[0194] Figure 6eThe polarization curve of the overall water splitting of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1 shows that Figure 6e at 10 mA / cm 2 , the cell voltage is 1.43 V, proving that this catalyst is an overall water splitting catalyst.

[0195] E, Figure 6f The chronopotentiometry analysis curve of the hydrogen evolution reaction of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1 in 1 mol / L KOH solution at a current density of 10 mA / cm 2 . It can be seen from Figure 6f that the overall water splitting catalyst of Example 1 has an overpotential that remains unchanged for nearly 1000 h under alkaline conditions at a small current density of 10 mA / cm 2 , indicating that this catalyst has excellent hydrogen evolution stability. Figure 6g The chronopotentiometry analysis curve of the oxygen evolution reaction of the Ni-Co-P / 3DPNC overall water splitting catalyst prepared in Example 1 in 1 mol / L KOH solution at a current density of 10 mA / cm 2 . It can be seen from Figure 6g that the overall water splitting catalyst of Example 1 has an overpotential that remains unchanged for more than 75 h under alkaline conditions at a small current density of 10 mA / cm 2 , indicating that this catalyst has excellent oxygen evolution stability.

[0196] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A preparation method of a full water splitting catalyst, characterized in that, It includes the following steps: 1) Add an aqueous acetic acid solution to the carbon source solution to obtain a gel ink; the carbon source solution includes chitosan and ZIF-67; 2) Print the gel ink by 3D printing to form a green body with periodically uniform pores; 3) Crosslink and cure the green body, and perform carbonization treatment on the crosslinked and cured green body to obtain a carbon composite material; 4) Load a transition metal phosphide onto the carbon composite material to obtain the overall water splitting catalyst; The transition metal phosphide is selected from nickel-cobalt bimetallic phosphides; The carbon source solution further includes raffinose, anhydrous calcium chloride, and / or a surfactant; Step 4) includes: dispersing a salt solution of a transition metal and an alkali source in deionized water to obtain a mixed solution; adding the carbon composite material to the mixed solution, and performing hydrothermal treatment at 100-200°C; subjecting the product of the hydrothermal treatment to a phosphidation reaction to obtain the overall water splitting catalyst.

2. The preparation method according to claim 1, wherein In step 2), the diameter of the printing nozzle for 3D printing is 1 mm, the printing speed is 3.0 - 10.0 mm / s, and the extrusion speed is 1.0 - 10.0 mm 3 / s.

3. The preparation method according to claim 2, characterized in that, The printing size of the green body is 30mm×30mm×6mm, the printing layer height is 1-3mm, and the printing method is one of the three filling wire routing methods of [0°, 90°], [0°, 45°, 90°], and [0°, 30°, 60°].

4. The preparation method according to any one of claims 1 to 3, characterized in that, The carbonization treatment includes: heating the temperature of the crosslinked and cured green body from room temperature to 800-900°C at a heating rate of 1-10°C / min, and then carbonizing for 1-4h.

5. The preparation method according to claim 4, characterized in that, After the carbonization treatment, it further includes performing pickling treatment on the carbonized green body.

6. The preparation method according to any one of claims 1 to 3, characterized in that, In step 1), the mass ratio of ZIF-67 to chitosan is (0.01-0.15):

1.

7. A catalyst for overall water splitting, characterized in that, Obtained by using the preparation method according to any one of claims 1-6.

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