CN114517303A

CN114517303A - Honeycomb electrolyzed water catalyst and preparation method and application thereof

Info

Publication number: CN114517303A
Application number: CN202210335093.8A
Authority: CN
Inventors: 刘世熙; 孙彭亮; 胡广志
Original assignee: Yunnan University YNU
Current assignee: Yunnan University YNU
Priority date: 2022-03-31
Filing date: 2022-03-31
Publication date: 2022-05-20
Anticipated expiration: 2042-03-31
Also published as: CN114517303B

Abstract

The invention provides a honeycomb-shaped electrolytic water catalyst, a preparation method and application thereof, belonging to the technical field of electrocatalysis. The honeycomb-shaped electrolytic water catalyst prepared by the method has the advantages of being porous, high in specific surface area, more in surface active sites, good in electron conduction capacity and the like, and the catalyst is used as a working electrode or a cathode and an anode respectively, and shows excellent catalytic activity and stability for hydrogen evolution and oxygen evolution reaction in alkaline electrolyte. Meanwhile, the catalyst is low in cost, the preparation method is simple and feasible in preparation process, environment-friendly and excellent in catalytic performance, and provides a basic application research for the materials in the field of electrocatalysis.

Description

Honeycomb electrolyzed water catalyst and preparation method and application thereof

Technical Field

The invention relates to the technical field of electrocatalysis, in particular to a honeycomb-shaped electrolytic water catalyst and a preparation method and application thereof.

Background

The rapid depletion of fossil fuels coupled with environmental crisis has strongly stimulated the pursuit of developing renewable alternative energy sources. Hydrogen is considered a promising alternative to fossil fuels as a zero carbon footprint fuel due to its high energy density and cleanliness. At present, Pt-based and Ir/Ru-based compounds have been the most advanced HER and OER electrocatalysts, respectively. However, the high price, scarcity, low bifunctional properties (excellent catalytic performance in both HER and OER, respectively) and poor stability of these noble metals severely limit their widespread use.

Molybdenum carbide is an important member of early transition metal carbides and has attracted interest as a high performance Hydrogen Evolution (HER) electrocatalyst due to its electronic structure similarity to platinum group metals. However, the problems of poor and unstable dual-function of the electrolyzed water still exist.

Disclosure of Invention

The invention aims to provide a honeycomb-shaped electrolytic water catalyst, a preparation method and application thereof, which have high activity, high stability and dual-functionality and low cost.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a preparation method of a honeycomb-shaped electrolytic water catalyst, which comprises the following steps:

dissolving polyacid and transition metal salt in hot water for doping, then adding a recrystallization solvent for recrystallization to obtain transition metal doped polyacid; the polyacid is phosphomolybdic acid or phosphotungstic acid; the transition metal salt is Fe salt, Co salt or Ni salt;

doping the transition metal with polyacid and SiO₂Mixing the ball and a carbon-nitrogen source in a solvent, and carrying out prepolymerization to obtain a prepolymer; the carbon-nitrogen source is dopamine hydrochloride, melamine or polyaniline; the SiO₂The particle size of the ball is 200-1000 nm;

pyrolyzing the prepolymer to obtain a pyrolysis product;

SiO in the pyrolysis product is treated by hydrofluoric acid₂And etching the ball to obtain the honeycomb-shaped electrolyzed water catalyst.

Preferably, the molar ratio of the transition metal ions in the polyacid and the transition metal salt is 1: (0.7-2.5).

Preferably, the hot water further contains a recrystallization aid, and the recrystallization aid comprises potassium acetate or potassium carbonate; the molar ratio of the polyacid to the recrystallization aid is 1: (1-1.5); the doping temperature is 85-105 ℃.

Preferably, the recrystallization solvent includes methanol, acetonitrile, ethanol or toluene; the temperature of recrystallization is 1.5-12.3 ℃.

Preferably, the pyrolysis temperature is 700-900 ℃, and the heat preservation time is 5-8 h.

Preferably, the solvent used for the prepolymerization is methanol, ethanol or acetonitrile.

Preferably, the mass ratio of the transition metal doped polyacid to the carbon-nitrogen source is 1: (0.8-3.8).

Preferably, the carbon nitrogen source and SiO₂The mass ratio of the ball is 1: (1.3-11.8).

The invention provides the honeycomb-shaped electrolyzed water catalyst prepared by the preparation method in the scheme.

The invention provides application of the honeycomb-shaped electrolyzed water catalyst in the scheme in alkaline electrolyzed water.

The invention provides a preparation method of a honeycomb-shaped electrolytic water catalyst, which comprises the following steps: dissolving polyacid and transition metal salt in hot water for doping, then adding a recrystallization solvent for recrystallization to obtain transition metal doped polyacid; the polyacid is phosphomolybdic acid or phosphotungstic acid; the transition metal salt is Fe salt, Co salt or Ni salt; doping the transition metal with polyacid and SiO₂Mixing the ball and a carbon-nitrogen source in a solvent, and carrying out prepolymerization to obtain a prepolymer; the SiO₂The particle size of the ball is 200-1000 nm; the carbon-nitrogen source is dopamine hydrochloride, melamine or polyaniline; pyrolyzing the prepolymer to obtain a pyrolysis product; SiO in the pyrolysis product is treated by hydrofluoric acid₂And etching the ball to obtain the honeycomb-shaped electrolyzed water catalyst. The invention firstly utilizes the vacancy characteristic of the polyacid to dope the transition metal into the polyacid and then uses SiO to dope the transition metal into the polyacid₂The ball is used as a template, and transition metal is doped with polyacid and SiO₂The spheres and the carbon-nitrogen source are mixed in a solvent, and the transition metal doped polyacid and the carbon-nitrogen source are prepolymerized together and anchored to SiO by utilizing the spontaneous polymerization of the carbon-nitrogen source (dopamine hydrochloride, melamine or polyaniline) under the alkalescent condition and the capability of chelating and adsorbing various metal ions in the self-polymerization process₂Surface of a ball, shapeForming a prepolymer; then pyrolyzing the carbon-nitrogen source in the prepolymer into N-doped C and pyrolyzing the transition metal-doped polyacid into X₂P/Y₂C heterojunction (X is transition metal, Fe, Co or Ni; Y is metal element in polyacid, Mo or W), and etching off SiO with hydrofluoric acid₂Ball to obtain honeycomb-shaped electrolytic water catalyst, abbreviated as X₂P/Y₂C @ NC catalyst.

The invention realizes the coupling of five elements of X (X ═ Fe, Co or Ni), Y (Y ═ Mo or W) and P, C, N simultaneously through one-step pyrolysis in a confined space (namely, prepolymer is obtained first), and a honeycomb-shaped porous nano structure is obtained in one step. Due to Y₂C (meaning Mo)₂C or W₂C) And X₂P(Co₂P、Fe₂P or Ni₂P) unique heterostructure and synergistic effect, realizes Mott-Schottky effect driven interface charge regulation, X₂P/Y₂The C @ NC catalyst exhibits excellent hydrogen and oxygen evolution properties. In alkaline medium, HER and OER are at a current density of 10mA cm^-2The overpotential for this time was 86mV and 209mV, respectively.

Honeycomb X of the invention₂P/Y₂The C @ NC catalyst has a stable porous structure, a good appearance and a large pore diameter, and the interconnected micropore and mesoporous structures can promote the diffusion of electrolyte; the macroporous structure can be used as an electrolyte storage bank, can effectively convey reactants and electrolyte to an active center, and can promote the release of bubbles. The pores can increase the specific surface area of the catalyst and improve the surface activity, and the surface particles are used as active sites of catalytic reaction and have high-efficiency electrocatalytic activity.

Furthermore, heteroatom doping (N and P elements) also improves the activity of the catalyst.

The preparation method has the advantages of simple reaction process, few reaction steps, short reaction period, good repeatability and the like, and has good application prospect and wide development space in the field of electrocatalysts.

Drawings

FIG. 1 shows Co prepared in example 1₂P/Mo₂Sweeping of C @ NC catalystScanning an electron microscope image;

FIG. 2 shows Co prepared in example 1₂P/Mo₂Transmission electron microscope images of C @ NC catalyst;

FIG. 3 shows Co prepared in example 1₂P/Mo₂The BET adsorption-desorption curve of the C @ NC catalyst;

FIG. 4 shows Co prepared in example 1₂P/Mo₂(ii) a raman spectrogram of C @ NC catalyst;

FIG. 5 shows Co prepared in example 1₂P/Mo₂XRD pattern of C @ NC catalyst;

FIG. 6 shows Co prepared in example 1 and comparative examples 1 and 2₂P/Mo₂C@NC、Co₂P@NC、Mo₂C @ NC and commercial Pt/C catalysts in 1M KOH solution (a) hydrogen evolution linear voltammogram and (b) tafel slope;

FIG. 7 shows Co prepared in example 1 and comparative examples 1 and 2₂P/Mo₂C@NC、Co₂P@NC、Mo₂C @ NC and commercial RuO₂The catalyst is (a) oxygen evolution linear voltammetry curve and (b) tafel slope curve in 1M KOH solution;

FIG. 8 shows Co prepared in example 1₂P/Mo₂Characterization of catalytic activity and stability of C @ NC catalyst in 1M KOH solution to (a) fully electrolyzed water and its commercial Pt/C and RuO₂Comparison of the noble metal catalyst stability.

Detailed Description

pyrolyzing the prepolymer to obtain a pyrolysis product;

In the present invention, the starting materials used are all commercially available products well known in the art, unless otherwise specified.

The polyacid and the transition metal salt are dissolved in hot water for doping, and then a recrystallization solvent is added for recrystallization to obtain the transition metal doped polyacid.

In the present invention, the polyacid is phosphomolybdic acid or phosphotungstic acid, preferably phosphomolybdic acid; the transition metal salt is Fe salt, Co salt or Ni salt, preferably Co salt. The invention has no special requirements on the specific types of the transition metal salts, and can be dissolved in water. In the examples of the present invention, Co (NO) is specifically used₃)₃·6H₂And O. In the present invention, the molar ratio of the transition metal ion in the polyacid and the transition metal salt is preferably 1: (0.7 to 2.5), more preferably 1: (1-2), more preferably 1: (1.2-1.6).

In the invention, the hot water preferably further contains a recrystallization aid, and the recrystallization aid preferably comprises potassium acetate or potassium carbonate, more preferably potassium acetate; the molar ratio of the polyacid to the recrystallization aid is preferably 1: (1-1.5). The invention utilizes the recrystallization assistant to improve the yield of recrystallization.

In the present invention, the doping by dissolving the polyacid and the transition metal salt in hot water preferably includes: dissolving polyacid in hot water to obtain a polyacid solution; dissolving a transition metal salt in hot water to obtain a transition metal salt solution; mixing the polyacid solution and the transition metal salt solution, and doping under stirring.

When the hot water contains a recrystallization aid, the dissolving of the polyacid and the transition metal salt in the hot water for doping preferably includes: dissolving polyacid in hot water to obtain polyacid solution; dissolving a transition metal salt in hot water to obtain a transition metal salt solution; dissolving a recrystallization aid in hot water to obtain a recrystallization aid solution; under the condition of stirring, adding a transition metal salt solution into a polyacid solution, then adding a recrystallization aid solution, and doping under the condition of stirring.

In the invention, the temperature of the hot water is preferably 85-105 ℃, the doping temperature is 85-105 ℃, and the doping time is preferably more than 2 min. The invention has no special requirement on the consumption of hot water, and can dissolve all substances. The invention uses hot water to promote the dissolution of polyacid and transition metal salt, and facilitates the doping of polyacid by transition metal.

After the doping is finished, the obtained solution is preferably cooled to below 60 ℃ for filtration, and then a recrystallization solvent is added for recrystallization to obtain the transition metal doped polyacid. The purpose of the invention is to prevent the solution from burning hands. The purpose of filtration is to remove impurities in the solution, and no solid is precipitated in the process of temperature reduction.

In the present invention, the recrystallization solvent preferably includes methanol, acetonitrile, ethanol, or toluene. The volume ratio of the recrystallization solvent to the total amount of hot water is preferably 1: (1-1.8).

In the invention, the recrystallization is preferably carried out under stirring, and the temperature of the recrystallization is preferably 1.5-12.3 ℃, and more preferably 5-10 ℃. The invention has no special requirement on the recrystallization time until no solid is continuously precipitated. In the examples of the present invention, 5 ℃ overnight is specifically mentioned.

The recrystallization process is preferably repeated for 2-3 times so as to improve the purity of the transition metal doped polyacid. The process of repeating the recrystallization according to the invention is preferably: and dissolving the transition metal doped polyacid obtained by the previous recrystallization in hot water, and then adding a recrystallization solvent for recrystallization.

After the recrystallization is completed, the obtained product is preferably dried to obtain the transition metal doped polyacid. The conditions for the drying are not particularly critical to the present invention and may be any conditions well known in the art. In the examples of the present invention, drying was carried out in an oven at 55 ℃.

After the transition metal doped polyacid is obtained, the invention dopes the transition metalPolyacid, SiO₂And mixing the ball and a carbon nitrogen source in a solvent, and performing prepolymerization to obtain a prepolymer.

In the invention, the carbon-nitrogen source is dopamine hydrochloride, melamine or polyaniline, and preferably dopamine hydrochloride. In the present invention, the mass ratio of the transition metal-doped polyacid to the carbon-nitrogen source is preferably 1: (0.8 to 3.8), more preferably 1: (1 to 3.5), more preferably 1: (2-3).

In the present invention, the SiO₂The particle size of the spheres is 200 to 1000nm, preferably 300 to 800nm, and more preferably 400 to 600 nm. In the present invention, the SiO₂The ball serves as a template for the water electrolysis catalyst. In the present invention, the carbon nitrogen source and SiO₂The mass ratio of the balls is preferably 1: (1.3 to 11.8), more preferably 1: (5-11.8).

In the present invention, the solvent is preferably methanol, ethanol or acetonitrile; the transition metal is doped with polyacid and SiO₂The preferable dosage ratio of the total mass of the ball and the carbon-nitrogen source to the solvent is 0.2-0.5 g: 1 mL.

In the invention, the transition metal is doped with polyacid and SiO₂The mixing of the spheres and the carbon and nitrogen source in the solvent preferably comprises: firstly, the transition metal doped polyacid and the carbon nitrogen source are dispersed into the solvent, and then SiO is added₂The balls are ground. The invention has no special requirements on the grinding conditions, and all the substances are uniformly mixed. The grinding process of the invention is a prepolymerization process. The invention utilizes the spontaneous polymerization of carbon-nitrogen source (dopamine hydrochloride, melamine or polyaniline) under alkalescent condition and the capability of chelating and adsorbing various metal ions in the self-polymerization process to pre-polymerize transition metal-doped polyacid and carbon-nitrogen source and anchor the transition metal-doped polyacid and the carbon-nitrogen source to SiO₂Forming prepolymer on the surface of the pellet.

After the grinding is completed, the present invention preferably dries the obtained ground product and then uniformly grinds the dried product to obtain a prepolymer.

After the prepolymer is obtained, the prepolymer is pyrolyzed to obtain a pyrolysis product.

In the invention, the pyrolysis temperature is preferably 700-900 ℃, and more preferablySelecting the temperature to be 750-850 ℃; the heat preservation time is preferably 5-8 h, and more preferably 6-7 h. In the present invention, the pyrolysis is preferably performed under a nitrogen atmosphere. In the pyrolysis process, the carbon-nitrogen source in the prepolymer is pyrolyzed into N-doped C, and simultaneously, the transition metal-doped polyacid is pyrolyzed into X₂P/Y₂C heterojunction (X is transition metal, Fe, Co or Ni; Y is metal element in polyacid, Mo or W).

The invention realizes the coupling of five elements of X (X ═ Fe, Co or Ni), Y (Y ═ Mo or W) and P, C, N simultaneously through one-step pyrolysis in a limited space (namely, prepolymer is obtained firstly).

After obtaining the pyrolysis product, the invention uses hydrofluoric acid to remove SiO in the pyrolysis product₂And etching the ball to obtain the honeycomb-shaped electrolyzed water catalyst.

In the invention, the concentration of the hydrofluoric acid is preferably 10-40 wt%, and the invention has no special requirement on the dosage of the hydrofluoric acid and can completely immerse the pyrolysis product. In the invention, the etching time is preferably 6-12 h. The invention utilizes etching to remove SiO₂Spheres, forming a honeycomb macroporous, microporous and mesoporous structure.

After the etching is finished, the obtained powder is preferably thoroughly washed by deionized water and ethanol, and is dried in vacuum at 50 ℃ for 12 hours to obtain the honeycomb-shaped electrolyzed water catalyst.

The invention provides a honeycomb-shaped electrolyzed water catalyst (X for short) prepared by the preparation method in the scheme₂P/Y₂C @ NC catalyst). The honeycomb-shaped electrolytic water catalyst comprises N-doped graphite phases C and X₂P/Y₂C heterojunction material (X is transition metal, Fe, Co or Ni; Y is metal element in polyacid, Mo or W).

Due to Y₂C (meaning Mo)₂C or W₂C) And X₂P/(Co₂P、Fe₂P or N₂P) unique heterostructure and synergistic effect, X₂P/Y₂The C @ NC catalyst exhibits excellent hydrogen and oxygen evolution properties.

In the present invention, the ratio table of the honeycomb-shaped electrolytic water catalystThe area is preferably 80-300 m²The average pore diameter is preferably 6.5 to 11.3nm, and the pore volume is preferably 0.02 to 0.09cm²/g。

Honeycomb X of the invention₂P/Y₂The C @ NC porous catalyst has a stable porous structure, a good appearance and a large pore diameter, and the interconnected micropore and mesoporous structures can promote the diffusion of electrolyte; the macroporous structure can be used as an electrolyte storage bank, can effectively convey reactants and electrolyte to an active center, and can promote the release of bubbles. The pores can increase the specific surface area of the catalyst and improve the surface activity, and the surface particles are used as active sites of catalytic reaction and have high-efficiency electrocatalytic activity.

The invention provides application of the honeycomb-shaped electrolyzed water catalyst in the scheme in alkaline electrolyzed water. In the present invention, the honeycomb-shaped electrolyzed water catalyst may be used as a cathode or an anode for electrolyzing water, or may be used as both the cathode and the anode.

The honeycomb-shaped electrolytic water catalyst provided by the present invention, the preparation method and the application thereof are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.

Example 1

5.65g (3.1mmoL) phosphomolybdic acid (PMo for short) is weighed₁₂) Dissolved in 25mL of hot water at 90 deg.C, 1.222g (4.2mmoL) of Co (NO) dissolved in 5mL of hot water was added under stirring₃)₂·6H₂O, and finally 10g of CH dissolved in 10mL of hot water₃And (4) COOK. The mixture was then allowed to react at 90 ℃ for 2min, cooled to 60 ℃ and filtered, and 40mL of CH was added to the filtrate with stirring₃OH and recrystallizing at 5 deg.C overnight, recrystallizing the crystal with a small amount of hot water for 3 times, and drying in oven at 55 deg.C to obtain Co-doped polyacid (CoPMo for short)₁₂。

0.2g CoPMo₁₂And 0.4g dopamine hydrochloride (DA) in 5mL methanol, then 1.0g SiO₂Grinding the microspheres (with the particle size of 200nm) in a mortar uniformly, drying in an oven at the temperature of 55 ℃ and then grinding uniformly to obtain SiO₂@ CoPMo @ DA prepolymer; harvesting machineAfter the product is collected, the product is ground uniformly in N₂Heating at 800 deg.C for 5 hr under atmosphere for pyrolysis at a heating rate of 5 deg.C/min^-1To obtain a pyrolysis product, SiO for short₂The @ CoPMo @ NC complex.

Mixing SiO₂Adding the @ CoPMo @ NC compound into 8.8mL of hydrofluoric acid (15 wt%) solution, stirring for 12h at room temperature, and removing SiO₂A template; finally, the powder was thoroughly washed with deionized water, ethanol and vacuum dried at 50 ℃ for 12 hours to obtain a honeycomb like electrolyzed water catalyst, noted as Co₂P/Mo₂C @ NC catalyst.

Example 2

Weigh 5.65g (3.1mmoL) of PMo₁₂Dissolved in 25mL of hot water at 90 deg.C, 0.611g (2.1mmoL) of Co (NO) dissolved in 5mL of hot water was added under stirring₃)₂·6H₂O, and finally 10g of CH dissolved in 10mL of hot water₃And COOK (cooling). The mixture was then allowed to react at 90 ℃ for 2min, cooled to 60 ℃ and filtered, and 40mL of CH was added to the filtrate with stirring₃OH and recrystallizing at 5 deg.C overnight, recrystallizing the crystal with a small amount of hot water for 3 times, and drying in oven at 55 deg.C to obtain Co-doped polyacid (CoPMo for short)₁₂。

0.2g CoPMo₁₂And 0.16g Polyaniline (PANI) dispersed in 5mL ethanol, then 0.8g SiO₂Grinding the microspheres (with the particle size of 600nm) in a mortar uniformly, drying in an oven at the temperature of 55 ℃ and grinding uniformly to obtain SiO₂@ CoPMo @ PANI prepolymer; the product is collected and then ground uniformly in N₂Heating at 750 deg.C for 7 hr for pyrolysis at 5 deg.C/min^-1Obtaining a pyrolysis product, noted as SiO₂The @ CoPMo @ NC complex.

Mixing SiO₂Adding the @ CoPMo @ NC compound into 10.5mL of hydrofluoric acid (10 wt%) solution, stirring for 8h at room temperature for etching, and removing SiO₂A template; finally, the powder was thoroughly washed with deionized water, ethanol and vacuum dried at 50 ℃ for 12 hours to obtain a honeycomb like electrolyzed water catalyst, noted as Co₂P/Mo₂C @ NC catalyst.

Example 3

8.928g (3.1mmoL) phosphotungstic acid (PW for short)₁₂) Dissolving in 25mL of 90 deg.C hot water, adding 1.688g (5.8mmoL) of Co (NO) dissolved in 5mL of hot water under stirring₃)₂·6H₂O, and finally 10g of CH dissolved in 10mL of hot water₃And COOK (cooling). The mixture was then allowed to react at 90 ℃ for 2min, cooled to 60 ℃ and filtered, and 40mL of CH was added to the filtrate with stirring₃OH and recrystallizing at 5 deg.C overnight, recrystallizing the crystal with a small amount of hot water for 3 times, and drying in oven at 55 deg.C to obtain Co-doped polyacid, CoPW for short₁₂。

0.2g of CoPW₁₂And 0.5g of Melamine (Mel) in 6mL of acetonitrile, followed by 1.5g of SiO₂Grinding the microspheres (with the particle size of 500nm) in a mortar uniformly, drying in an oven at the temperature of 55 ℃ and grinding uniformly to obtain SiO₂@ CoPMo @ Mel prepolymer; the product is collected and then ground uniformly in N₂Heating at 850 deg.C for 5 hr under atmosphere for pyrolysis, with heating rate of 5 deg.C/min^-1Obtaining a pyrolysis product, noted as SiO₂@ CoPW @ NC complex.

Mixing SiO₂Adding the @ CoPW @ NC compound into 9.2mL of hydrofluoric acid (20 wt%) solution, stirring for 10h at room temperature for etching, and removing SiO₂A template; finally, the powder was thoroughly washed with deionized water, ethanol and vacuum dried at 50 ℃ for 12 hours to obtain a honeycomb like electrolyzed water catalyst, noted as Co₂P/W₂C @ NC catalyst.

Example 4

Weigh 8.92g (3.1mmoL) of PW₁₂Dissolved in 25mL of hot water at 90 deg.C, 1.939g (4.8mmoL) of Fe (NO) dissolved in 5mL of hot water was added with stirring₃)₃·9H₂O, and finally 10g of CH dissolved in 10mL of hot water₃And COOK (cooling). The mixture was then left to react at 90 ℃ for 2min, cooled to 60 ℃ and filtered, and 40mL of CH was added to the filtrate with stirring₃OH and recrystallizing at 5 deg.C overnight, recrystallizing the crystal with a small amount of hot water for 3 times, and drying at 55 deg.C in oven to obtain Fe-doped polyacid (FePW for short)₁₂。

0.2g of FePW₁₂And 0.62g Polyaniline (PANI) dispersed in 6mL of methanol, followed by 1.9g of SiO₂Grinding the microspheres (with the particle size of 800nm) in a mortar uniformly, drying in an oven at the temperature of 55 ℃ and grinding uniformly to obtain SiO₂@ FePW @ PANI prepolymer; the product is collected and then ground uniformly in N₂Heating at 900 deg.C for 6 hr under atmosphere for pyrolysis at a heating rate of 5 deg.C/min^-1Obtaining a pyrolysis product, SiO for short₂@ FePW @ NC complex.

Mixing SiO₂Adding the @ FePW @ NC compound into 6mL of hydrofluoric acid (40 wt%) solution, stirring for 6h at room temperature, and removing SiO₂A template; finally, the powder is thoroughly washed with deionized water and ethanol and dried in vacuum at 50 ℃ for 12 hours to obtain the honeycomb-shaped electrolyzed water catalyst which is marked as Fe₂P/W₂C @ NC catalyst.

Example 5

Weighing 8.928g (3.1mmoL) PW₁₂Dissolving in 25mL of hot water at 90 deg.C, adding 1.512g (5.2mmoL) of Ni (NO) dissolved in 5mL of hot water under stirring₃)₂·6H₂O, and finally 10g of CH dissolved in 10mL of hot water₃And COOK (cooling). The mixture was then allowed to react at 90 ℃ for 2min, cooled to 60 ℃ and filtered, and 40mL of CH was added to the filtrate with stirring₃OH and recrystallizing at 5 deg.C overnight, recrystallizing the crystal with a small amount of hot water for 3 times, and drying at 55 deg.C in oven to obtain Ni-doped polyacid (NiPW for short)₁₂。

0.2g of NiPW₁₂And 0.68g Polyaniline (PANI) dispersed in 7mL methanol, followed by 1.8g SiO₂Grinding the microspheres (with the particle size of 700nm) in a mortar uniformly, drying in an oven at the temperature of 55 ℃ and grinding uniformly to obtain SiO₂@ NiPW @ PANI prepolymer; the product is collected and then ground uniformly in N₂Heating at 900 deg.C for 6 hr under atmosphere for pyrolysis at a heating rate of 5 deg.C/min^-1Obtaining a pyrolysis product, SiO for short₂@ NiPW @ NC complex.

Mixing SiO₂Adding the @ NiPW @ NC compound into 10mL of hydrofluoric acid (40 wt%) solution, stirring for 6h at room temperature, and removing SiO₂A template; finally, the process is carried out in a batch,thoroughly washing the powder with deionized water and ethanol, and vacuum drying at 50 deg.C for 12 hr to obtain honeycomb-shaped electrolyzed water catalyst, denoted as Ni₂P/W₂C @ NC catalyst.

Example 6

Weigh 5.65g (3.1mmoL) of PMo₁₂Dissolved in 25mL of hot water at 90 ℃ and 1.939g (4.8mmoL) of Fe (NO) dissolved in 5mL of hot water was added with stirring₃)₃·9H₂O, and finally 10g of CH dissolved in 10mL of hot water₃And COOK (cooling). The mixture was then allowed to react at 90 ℃ for 2min, cooled to 60 ℃ and filtered, and 40mL of CH was added to the filtrate with stirring₃OH, standing overnight at 5 ℃, recrystallizing the precipitated crystals for 3 times by using a small amount of hot water, and drying in an oven at 55 ℃ to obtain Fe-doped polyacid (FePMo for short)₁₂。

0.2g of FePMo₁₂And 0.36g dopamine hydrochloride (DA) in 5mL methanol, followed by 0.7g SiO₂Grinding the microspheres (with the particle size of 600nm) in a mortar uniformly, drying in an oven at the temperature of 55 ℃ and grinding uniformly to obtain SiO₂@ FePMo @ DA prepolymer; the product is collected and then ground uniformly in N₂Heating at 750 deg.C for 8 hr for pyrolysis at 5 deg.C/min^-1Obtaining a pyrolysis product, noted as SiO₂The @ CoPMo @ NC complex.

Mixing SiO₂Adding the @ FePMo @ NC compound into 7mL of hydrofluoric acid (30 wt%) solution, stirring for 6h at room temperature for etching, and removing SiO₂A template; finally, the powder is thoroughly washed with deionized water and ethanol and dried in vacuum at 50 ℃ for 12 hours to obtain the honeycomb-shaped electrolyzed water catalyst which is marked as Fe₂P/Mo₂C @ NC catalyst.

Example 7

Weigh 5.65g (3.1mmoL) of PMo₁₂Dissolved in 25mL of hot water at 90 deg.C, 1.221g (4.2mmoL) of Ni (NO) dissolved in 5mL of hot water was added under stirring₃)₂·6H₂O, and finally 10g of CH dissolved in 10mL of hot water₃And COOK (cooling). Then maintaining the mixture at 90 deg.C for 2min, cooling to 60 deg.C, filtering, and adding 40mL of the filtrate under stirringCH₃OH and recrystallizing at 5 deg.C overnight, recrystallizing the crystal with a small amount of hot water for 3 times, and drying in oven at 55 deg.C to obtain Ni-doped polyacid (NiPMo for short)₁₂。

0.2g of NiPMo₁₂And 0.56g of Melamine (Mel) in 6mL of ethanol, followed by 1.0g of SiO₂Grinding the microspheres (with the particle size of 400nm) in a mortar uniformly, drying in an oven at the temperature of 55 ℃ and then grinding uniformly to obtain SiO₂@ NiPMo @ Mel prepolymer; the product is collected and then ground uniformly in N₂Heating at 850 deg.C for 6 hr under atmosphere for pyrolysis, with heating rate of 5 deg.C/min^-1Obtaining a pyrolysis product, noted as SiO₂@ NiPMo @ NC compound.

Mixing SiO₂Adding the @ NiPMo @ NC compound into 9.3mL of hydrofluoric acid (20 wt%) solution, stirring for 8h at room temperature for etching, and removing SiO₂A template; finally, the powder is thoroughly washed with deionized water and ethanol and dried in vacuum at 50 ℃ for 12 hours to obtain the honeycomb-shaped electrolyzed water catalyst, which is recorded as Ni₂P/Mo₂C @ NC catalyst.

Comparative example 1

Co₂Synthesis of P @ NC catalyst

0.2g of Co (NO)₃)₂·6H₂O and 0.4g dopamine hydrochloride and 1.0g SiO₂Grinding the microspheres (with the particle size of 300nm) in a mortar uniformly, adding 5mL of methanol for dispersion, drying in an oven at the temperature of 55 ℃, and grinding uniformly to obtain SiO₂@ Co @ DA prepolymer; in N₂Heating at 800 deg.C for 6 hr under atmosphere to carbonize at a heating rate of 5 deg.C/min^-1. The carbonized product was again placed in an alumina magnetic boat, and 1.5g of sodium hypophosphite (NaH) was added₂PO₂·H₂O) as phosphorus source is put in two independent positions (in tandem) with catalyst in porcelain boat, and N is used₂Blowing for 30min to remove air in the furnace tube, heating at 350 deg.C for 2 hr at 2 deg.C for min^-1To obtain SiO₂@Co₂P @ NC complex. The product was added to 8.8mL hydrofluoric acid (10 wt%) solution and stirred at room temperature for 12h to remove SiO₂A template; the powder was then de-ionizedThoroughly washing with water, and vacuum drying at 50 deg.C for 12 hr to obtain Co₂P @ NC catalyst.

Comparative example 2

Mo₂Synthesis of C @ NC catalyst

0.2g of Na₂MoO₄And 0.4g dopamine hydrochloride and 1.0g SiO₂Grinding the microspheres (with the particle size of 300nm) in a mortar uniformly, adding 5mL of methanol for dispersion, drying in an oven at the temperature of 55 ℃, and grinding uniformly to obtain SiO₂@ Mo @ DA complex; in N₂Heating at 800 deg.C for 6 hr under atmosphere at a heating rate of 5 deg.C/min^-1To obtain SiO₂@Mo₂C @ NC complex. The product was added to 8.8mL hydrofluoric acid (10 wt%) solution and stirred at room temperature for 12h to remove SiO₂A template; then, the powder was thoroughly washed with deionized water and vacuum dried at 50 ℃ for 12 hours to finally obtain Mo₂C @ NC catalyst.

And (3) structural and performance characterization:

for Co prepared in example 1₂P/Mo₂The results of the scanning electron microscope observation of the C @ NC catalyst are shown in FIG. 1. As can be seen from FIG. 1, the porous structures are closely connected and distributed in layers. The carrier (N doped C) has strong adhesion with the catalyst, which is beneficial to reducing the contact resistance and being beneficial to injecting and transmitting charges from the electrode to the active site of the catalyst.

For Co prepared in example 1₂P/Mo₂The results of the transmission electron microscope observation of the C @ NC catalyst are shown in FIG. 2. As shown in FIG. 2, numerous small nanocrystals (Co) are dispersed on the porous skeleton₂P/Mo₂C heterojunction), the nanocrystals are favorable for the generation of boundaries, defects and dislocations, which provide a large number of active centers for enhanced catalytic activity. Two adjacent nanocrystals were intimately fused together at the boundary, indicating that they were tightly connected to each other, ensuring good electrical and mechanical contact, and thus achieving an efficient and stable catalytic reaction.

For Co prepared in example 1₂P/Mo₂BET adsorption-desorption analysis of the C @ NC catalyst showed the results shown in fig. 3. According to the results shown in FIG. 3, Co₂P/Mo₂The specific surface area of C @ NC is as high as 88.45m²·g^-1The isothermal adsorption line is an I/IV mixed type, and H appears in a middle-high pressure area₄The hysteresis loop indicates that the pore structure mainly comprises micropores and mesopores. The interconnected microporous and mesoporous structures may facilitate electrolyte diffusion, while the macroporous structure may serve as an electrolyte reservoir, both to efficiently transport reactants and electrolyte to the active sites and to facilitate release of gas bubbles.

For Co prepared in example 1₂P/Mo₂The raman spectrum of the C @ NC catalyst was analyzed, and the results are shown in fig. 4. Raman spectroscopy further confirms Co₂P/Mo₂Degree of graphitization of C @ NC (fig. 4). D belt (1350 cm)^-1) And G belt (1580 cm)^-1) Ratio of intensities (I)_D/I_G) 1.89, indicating that there is partial graphitization and many structural defects on the porous carbon shell, facilitating electrical conduction and H⁺/H₂And (4) absorbing.

For Co prepared in example 1₂P/Mo₂XRD analysis of the C @ NC catalyst gave the results shown in FIG. 5. FIG. 5 shows Co₂P/Mo₂Powder X-ray diffraction (PXRD) pattern of C @ NC. PXRD peaks can be attributed to Co₂P (JCPDS, No.54-0413) and Mo₂C (JCPDS, No. 31-0871). The peaks at 31.09 °, 40.83 °, 44.85 °, 48.37 °, 55.47 ° and 67.91 ° are clearly visible, pointing to Co, respectively₂The (110), (111), (021), (120), (030) and (130) planes of P. Four characteristic peaks at 34.41 degrees, 37.94 degrees, 39.45 degrees and 61.38 degrees, which are respectively attributed to Mo₂The (002), (200), (102) and (040) crystal planes of C. The additional peak observed at 24 ° is due to graphitic carbon.

The results of analyzing the hydrogen evolution performance of the catalysts prepared in example 1 and comparative examples 1 to 2 are shown in fig. 6. As expected, Co₂P/Mo₂C @ NC electrode showed the best HER electrochemical activity, driving 10mA cm^-2、50mA·cm^-2And 100mA · cm^-2The overpotentials required are 86mV (. eta.10),. eta.133 mV (. eta.50) and 165mV (. eta.100), respectively, which can be used with Pt/C electrodes (eta.10: 37mV,. eta.50: 129mV,. eta.100: 218 m)V) (fig. 6 (a)). Co₂P/Mo₂C @ NC shows the ratio Co₂P@NC、Mo₂Better HER activity of C @ NC, indicating Co₂P and Mo₂There is a synergistic effect between C. Furthermore, Co₂P/Mo₂The C @ NC catalyst has relatively fast dynamic performance on HER, and the Tafel slope of the C @ NC catalyst is 46mV dec^-1Lower than Pt/C (54mV dec)^-1)、Co₂P@NC(116mV·dec^-1) And Mo₂C@NC(153mV·dec^-1) (FIG. 6 (b)). As is well known, Tafel slopes of 120, 40 and 30mV dec^-1Corresponding to the Volmer, Heyrovsky and Tafel processes, respectively, indicating that the reaction proceeds by the Volmer-Heyrovsky mechanism. Tafel slope of 46mV, indicating Co₂P/Mo₂The HER pathway of C @ NC follows the Volmer-Tafel mechanism.

The results of analyzing the oxygen evolution performance of the catalysts prepared in example 1 and comparative examples 1 to 2 are shown in fig. 7. As expected, Co is seen from the polarization curves of representative samples₂P/Mo₂The performance of C @ NC is superior to that of commercial RuO₂(FIGS. 7 (a) and (b)). Co₂P/Mo₂C @ NC has the minimum overpotential, eta 10 of 209mV, eta 50 of 270mV, eta 100 of 350mV, specific to RuO₂(eta.10-240 mV) is low by 31mV, much lower than Co₂P @ NC (. eta.10. 301mV), notably Mo₂Lower than Co of C @ NC (. eta.10. 181mV)₂P/Mo₂C @ NC (. eta.10. 209mV), but at a current density of 13mA · cm^-2As above, the overpotential exhibits an increasing tendency ((a) in fig. 7). At the same time, Co₂P/Mo₂Tafel slope of C @ NC is 91mV dec^-1Lower than RuO₂(132mV·dec^-1)，Mo₂C@NC(140mV·dec^-1) And Co₂P@NC(169mV·dec^-1) (FIG. 7 (b)) shows Co₂P/Mo₂C @ NC faster OER kinetics.

Catalytic activity on the catalyst of example 1 for total electrolysis of water and its commercial Pt/C and RuO₂The results of comparison of the stability of the noble metal catalysts are shown in fig. 8. With Co₂P/Mo₂C @ NC is an anode and a cathode, and an integral water splitting experiment is carried out. As shown in FIG. 8 (a), in the two-electrode system, electrons can rapidly pass through the porous catalyst because of its high conductivity and can be separately dissociated and adsorbed on Co₂P/Mo₂H on C @ NC₂O and OH^-And H is simultaneously generated at the cathode₂And generating O at the anode₂. As expected, Co₂P/Mo₂The C @ NC pair is greatly superior to Pt/C II RuO₂And (4) carrying out pairing. Co₂P/Mo₂The C @ NC pair shows excellent catalytic bulk water splitting activity, and can provide 10mA · cm only by 1.55V^-2Current density of (1) is much lower than Pt/C II RuO₂(1.62V). Furthermore, Co₂P/Mo₂C @ NC in the range of 10mA · cm^-2、50mA·cm^-2And 100mA · cm^-2The i-t chronoamperometric curve at current density demonstrates its good long-term stability (fig. 8 (b)).

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a honeycomb-shaped water electrolysis catalyst comprises the following steps:

pyrolyzing the prepolymer to obtain a pyrolysis product;

2. The method according to claim 1, wherein the molar ratio of the transition metal ion in the polyacid and the transition metal salt is 1: (0.7-2.5).

3. The preparation method of claim 1, wherein the hot water further contains a recrystallization aid, and the recrystallization aid comprises potassium acetate or potassium carbonate; the molar ratio of the polyacid to the recrystallization aid is 1: (1-1.5); the doping temperature is 85-105 ℃.

4. The production method according to claim 1, wherein the recrystallization solvent includes methanol, acetonitrile, ethanol, or toluene; the temperature of recrystallization is 1.5-12.3 ℃.

5. The preparation method of claim 1, wherein the pyrolysis temperature is 700-900 ℃ and the holding time is 5-8 h.

6. The method according to claim 1, wherein the solvent used in the prepolymerization is methanol, ethanol or acetonitrile.

7. The preparation method according to claim 1, wherein the mass ratio of the transition metal doped polyacid to the carbon-nitrogen source is 1: (0.8-3.8).

8. The method according to claim 1 or 7, wherein the carbon-nitrogen source and SiO₂The mass ratio of the ball is 1: (1.3-11.8).

9. The honeycomb-shaped electrolyzed water catalyst prepared by the preparation method of any one of claims 1 to 8.

10. Use of the honeycomb electrolyzed water catalyst of claim 9 in alkaline electrolyzed water.