CN115011997A

CN115011997A - Self-supporting hollow candied gourd-shaped electrocatalyst and preparation method and application thereof

Info

Publication number: CN115011997A
Application number: CN202210668202.8A
Authority: CN
Inventors: 王刚; 徐丹; 刘涵丹; 刘艳艳
Original assignee: Shihezi University
Current assignee: Shihezi University
Priority date: 2022-06-14
Filing date: 2022-06-14
Publication date: 2022-09-06
Anticipated expiration: 2042-06-14
Also published as: CN115011997B

Abstract

The invention provides a self-supporting hollow candied gourd-shaped electrocatalyst, a preparation method and application thereof, and belongs to the technical field of electrocatalytic water decomposition. Firstly, the invention takes the foam nickel as the substrate to prepare NiMoO ₄ ·xH ₂ An O/NF nanorod array is used as a growth framework, ZIF-67 is wrapped on the surface of the nanorod by an MOF participation strategy to form a sugarcoated haw-shaped core-shell structure, and NiMoO is formed by selective vulcanization ₄ ·xH ₂ The self-supporting hollow sugarcoated haw-shaped core-shell array structure with O as the core and Ni-Co-S nanocages as the shell ensures that the electrocatalyst is even under the condition of high current density (350mA cm) ^‑2 ) Still has excellent hydrogen evolution andoxygen evolution performance is beneficial to the improvement of full hydrolysis performance.

Description

Self-supporting hollow candied gourd-shaped electrocatalyst and preparation method and application thereof

Technical Field

The invention relates to the technical field of electrocatalytic water decomposition, in particular to a self-supporting hollow candied gourd-shaped electrocatalyst and a preparation method and application thereof.

Background

Increasing energy and environmental crisis have raised global concerns, and therefore, it is highly necessary to develop new renewable, clean energy sources to replace traditional fossil fuels. The hydrogen energy has the characteristics of large energy density, high heat value, rich resources, zero carbon emission, easy storage and the like, is generally considered as a potential energy carrier of a future sustainable energy system, and is widely concerned by people. Compared with the traditional hydrogen production technology, the hydrogen production by electrolyzing water has the advantages of high conversion efficiency, zero carbon emission, high hydrogen purity and the like, and is the hydrogen production technology with the greatest development prospect. However, in an actual water electrolysis process, an additional driving force (usually expressed in the form of an overpotential) is usually required to overcome the activation energy barrier and some other resistance of the solution and electrode/electrolyte contact interface to force the entire reaction to occur. Highly active electrocatalysts are sought to be effective means of increasing the efficiency of water electrolysis.

Currently, Pt-based noble metals are the best Hydrogen Evolution Reaction (HER) catalysts, while RuO ₂ And IrO ₂ Is the baseline electrocatalyst for Oxygen Evolution Reaction (OER). However, the problems of small reserves, high cost, poor stability and the like of the noble metals limit the large-scale application of the noble metals. Furthermore, the use of HER and OER catalysts often requires different environments. HER catalysts show good catalytic activity under acidic conditions while OER catalysts have better catalytic activity under basic conditions. Therefore, it is of great interest to develop and design non-noble metal electrocatalysts having the dual-functional properties of hydrogen evolution and oxygen evolution in the same electrolyte.

Disclosure of Invention

The invention aims to provide a self-supporting hollow candied gourd-shaped electrocatalyst and a preparation method and application thereof.

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

the invention provides a preparation method of a self-supporting hollow candied gourd-shaped electrocatalyst, which comprises the following steps:

mixing foamed nickel, a molybdenum source, a nickel source and water, and carrying out hydrothermal reaction to obtain a nickel-molybdenum oxide-nickel compound;

mixing the nickel-molybdenum oxide-nickel compound, a divalent cobalt salt-containing solution and a 2-methylimidazole solution, and carrying out coordination to obtain nickel-molybdenum oxide @ ZIF-67;

mixing the nickel molybdenum oxide @ ZIF-67 with a sulfur source-containing solution, and carrying out a solvothermal reaction to obtain a self-supported hollow candied gourd-shaped electrocatalyst; the mass ratio of the sulfur source to the nickel molybdenum oxide @ ZIF-67 in the sulfur source-containing solution is (3.5-5): 1.

Preferably, the molybdenum source comprises ammonium molybdate or sodium molybdate, and the nickel source comprises nickel acetate, nickel nitrate or nickel chloride.

Preferably, the molar ratio of the nickel source to the molybdenum source is 1: 1-10: 1; the temperature of the hydrothermal reaction is 140-180 ℃, and the time is 6-10 h.

Preferably, the divalent cobalt salt in the divalent cobalt salt-containing solution is cobalt nitrate, cobalt chloride, cobalt acetate or cobalt sulfate; the concentration of the divalent cobalt salt solution is 0.04-0.08 mol/L; the concentration of the 2-methylimidazole solution is 0.4-0.8 mol/L.

Preferably, the molar ratio of the 2-methylimidazole to the divalent cobalt salt in the divalent cobalt salt-containing solution is (0.08-0.16) to (0.8-1.6); the mass ratio of the nickel-molybdenum oxide-nickel compound to the divalent cobalt salt is 0.006 (0.23-0.46).

Preferably, the mixing of the nickel molybdenum oxide-nickel composite, the divalent cobalt salt-containing solution and the 2-methylimidazole solution comprises placing the nickel molybdenum oxide-nickel composite in the divalent cobalt salt-containing solution, performing first mixing, and performing second mixing on the obtained mixed solution and the 2-methylimidazole solution; the first mixing time is 5-10 min; and the second mixing time is 15-45 min.

Preferably, the sulfur source in the sulfur source-containing solution is thioacetamide, thiourea, sodium sulfide or cysteine, and the concentration of the sulfur source in the sulfur source-containing solution is 0.044 mol/L.

Preferably, the temperature of the solvothermal reaction is 120-150 ℃ and the time is 4-6 h.

The invention provides a self-supporting hollow candied gourd-shaped electrocatalyst prepared by the preparation method in the technical scheme, which comprises a nickel-molybdenum oxide-nickel composite inner core and a hollow Ni-Co-S nano cage shell.

The invention provides application of the self-supporting hollow candied gourd-shaped electrocatalyst in the technical scheme in the field of alkaline full-electrolytic cell water decomposition.

The invention provides a preparation method of a self-supporting hollow candied gourd-shaped electrocatalyst, which comprises the following steps: mixing foamed nickel, a molybdenum source, a nickel source and water, and carrying out hydrothermal reaction to obtain a nickel-molybdenum oxide-nickel compound; mixing the nickel-molybdenum oxide-nickel compound, a divalent cobalt salt-containing solution and a 2-methylimidazole solution, and carrying out coordination to obtain nickel-molybdenum oxide @ ZIF-67; mixing the nickel molybdenum oxide @ ZIF-67 with a sulfur source-containing solution, and carrying out a solvothermal reaction to obtain a self-supported hollow candied gourd-shaped electrocatalyst; the mass ratio of the sulfur source to the nickel molybdenum oxide @ ZIF-67 in the sulfur source-containing solution is (3.5-5): 1.

The invention firstly takes the foam nickel as the substrate to prepare the nickel molybdenum oxide-nickel compound (NiMoO) ₄ ·xH ₂ An O/NF nanorod array, x is more than or equal to 0), then the nanorod array is taken as a growth framework, ZIF-67 is wrapped on the surface of the nanorod by an MOF participation strategy to form a sugarcoated haw-shaped core-shell structure, and then selective vulcanization is carried out by adjusting and controlling the dosage of a sulfur source to realize a hollow core structure, so that NiMoO is formed ₄ ·xH ₂ The self-supporting hollow sugarcoated haw-shaped core-shell array structure takes O as a core and takes a Ni-Co-S nanocage as a shell. The invention takes the foamed nickel as the substrate, so that the electrocatalyst has the inherent structural advantages of the self-supporting electrocatalyst (the self-supporting structure avoids the use of a polymer adhesive, reduces the contact internal resistance of an active material and a conductive substrate, and realizes the rapid desorption of gas), and the hollow sugarcoated haw-shaped structure ensures that the electrocatalyst has larger specific surface area, can increase the contact area of an electrode and electrolyte, expose more active sites and improve the electronic conductivity, also obviously enhances the catalytic activity and stability of the electrocatalyst, and is beneficial to rapid charge and mass transfer and excellent reaction kinetics; the multi-element metal sulfide formed by selective vulcanization can realize the synergistic effect among different metal ions, and the catalyst is enhancedIntrinsic activity, thereby ensuring that the electrocatalyst is even under the condition of high current density (350 mAcm) ^-2 ) Still has excellent hydrogen evolution and oxygen evolution performances, and is beneficial to the improvement of the full-hydrolytic performance.

The preparation process is simple, no template is required to be removed, the production cost is low, the product structure is stable, and the prepared self-supporting hollow candied gourd-shaped electrocatalyst has the potential of being practically applied to the water electrolysis industry of the alkaline full electrolytic cell.

Drawings

FIG. 1 is a NiMoO prepared in example 1 ₄ ·xH ₂ XRD patterns of O @ Ni-Co-S array electrocatalysts;

FIG. 2 is a NiMoO prepared in example 1 ₄ ·xH ₂ SEM image of O @ Ni-Co-S array electrocatalyst;

FIG. 3 is a NiMoO prepared in example 1 ₄ ·xH ₂ TEM image of O @ Ni-Co-S array electrocatalyst;

FIG. 4 is a NiMoO prepared in example 1 ₄ ·xH ₂ Elemental mapping diagram for O @ Ni-Co-S array electrocatalyst;

figure 5 is a graph of HER polarization for the electrocatalyst prepared in example 1, the electrocatalyst prepared in comparative example 1, and commercial Pt;

FIG. 6 electrocatalyst prepared in example 1, electrocatalyst prepared in comparative example 1, and commercial RuO ₂ OER polarization profile of the catalyst;

FIG. 7 is a polarization curve of an alkaline water-splitting electrolyzer assembled as a positive electrode and a negative electrode with the electrocatalyst prepared in example 1;

FIG. 8 is a digital photograph of the Hoffman apparatus used in example 1 for measuring Faraday efficiency;

FIG. 9 shows the electrocatalyst yield H prepared in example 1 ₂ And O ₂ Graph of the volume change of (a);

FIG. 10 is a graph showing the test of the overall water decomposition stability at a voltage of 1.51V (vs. RHE) in example 1.

Detailed Description

In the present invention, unless otherwise specified, all the starting materials required for the preparation are commercially available products well known to those skilled in the art.

The invention mixes the foam nickel, the molybdenum source, the nickel source and the water to carry out hydrothermal reaction, and the nickel-molybdenum oxide-nickel compound is obtained.

The Nickel Foam (NF) is not particularly limited in the present invention, and may be any commercially available one well known in the art; the invention has no special limit on the size of the foamed nickel, and the foamed nickel can be adjusted according to the actual requirement; in the present invention, the size of the foamed nickel is 1.5X 3cm ² 。

In the invention, before the foamed nickel is used, 1mol/L HCl solution, deionized water and absolute ethyl alcohol are preferably adopted to carry out ultrasonic cleaning for 15min in sequence, and then the foamed nickel is dried in vacuum at low temperature. The specific procedures of the ultrasonic cleaning and the low-temperature vacuum drying are not particularly limited in the present invention, and may be performed according to procedures well known in the art.

In the present invention, the molybdenum source preferably includes ammonium molybdate or sodium molybdate, and the nickel source preferably includes nickel acetate, nickel nitrate or nickel chloride; the molar ratio of the nickel source to the molybdenum source is preferably 1: 1-10: 1, and more preferably 8.75: 1.

In the present invention, the process of mixing the foamed nickel, the molybdenum source, the nickel source and the water is preferably as follows: dissolving a molybdenum source and a nickel source in water, and mixing the obtained mixed solution with foamed nickel; in the mixed liquid, the concentration of the molybdenum source is preferably 0.0057mol/L, and the concentration of the nickel source is preferably 0.0267 mol/L.

In the invention, the temperature of the hydrothermal reaction is preferably 140-180 ℃, and the time is preferably 6-10 h; the hydrothermal reaction is preferably carried out in a teflon-lined autoclave.

After the hydrothermal reaction is finished, the obtained product is preferably cooled, deionized water and ethanol are sequentially adopted to wash the foamed nickel for a plurality of times, and then the vacuum drying is carried out to obtain a nickel-molybdenum oxide-nickel compound, which is marked as NiMoO ₄ ·xH ₂ O/NF (x is more than or equal to 0); the invention has no special limit on the washing times, and the washing is carried out according to the process well known in the field; the vacuum drying conditions are not particularly limited in the invention, and the drying can be carried out according to the processes well known in the art; in the embodiment of the invention, the temperature of the vacuum drying is 60 ℃ and the time is 12 h.

After the nickel-molybdenum oxide-nickel compound is obtained, the nickel-molybdenum oxide-nickel compound, a divalent cobalt salt solution and a 2-methylimidazole solution are mixed and coordinated to obtain the nickel-molybdenum oxide @ ZIF-67. In the invention, the divalent cobalt salt in the divalent cobalt salt-containing solution is preferably cobalt nitrate, cobalt chloride, cobalt acetate or cobalt sulfate; the concentration of the divalent cobalt salt-containing solution is preferably 0.04-0.08 mol/L, and more preferably 0.06 mol/L; the molar ratio of the 2-methylimidazole to the divalent cobalt salt in the divalent cobalt salt-containing solution is preferably (0.08-0.16) to (0.8-1.6), and more preferably 0.12: 1; the mass ratio of the nickel molybdenum oxide-nickel compound to the divalent cobalt salt is preferably 0.006 (0.23-0.46).

In the invention, the concentration of the 2-methylimidazole solution is preferably 0.4-0.8 mol/L, and more preferably 0.5 mol/L; the solvent used for the divalent cobalt salt-containing solution and the 2-methylimidazole solution is preferably methanol. The preparation process of the divalent cobalt salt-containing solution and the 2-methylimidazole solution is not particularly limited in the present invention, and the solution may be prepared according to a process well known in the art.

In the present invention, the mixing of the nickel molybdenum oxide-nickel complex, the divalent cobalt salt-containing solution, and the 2-methylimidazole solution preferably includes placing the nickel molybdenum oxide-nickel complex in the divalent cobalt salt-containing solution, performing a first mixing, and performing a second mixing of the resulting mixed solution with the 2-methylimidazole solution; the invention preferably relates to 2-methylThe imidazole solution was added dropwise to the mixture under vigorous stirring. In the invention, the time of the first mixing is preferably 5-10 min; the time for the second mixing is preferably 15 to 45min, and more preferably 30 min. In the present invention, the first mixing and the second mixing are preferably performed under stirring conditions, and the stirring rate is not particularly limited in the present invention, and may be performed according to a process well known in the art. According to the invention, divalent cobalt ions are fully attached to NiMoO through first mixing ₄ ·xH ₂ On an O/NF framework; in the second mixing process, divalent cobalt ions coordinate with 2-methylimidazole to form ZIF-67.

After the coordination is completed, the obtained product is preferably washed and dried in sequence to obtain the nickel molybdenum oxide @ ZIF-67 which is recorded as NiMoO ₄ ·xH ₂ O @ ZIF-67/NF; the reagent used for washing is preferably absolute ethyl alcohol, and the drying temperature is preferably 60 ℃ and the time is preferably 6 h.

After the nickel molybdenum oxide @ ZIF-67 is obtained, the nickel molybdenum oxide @ ZIF-67 and a sulfur source-containing solution are mixed for solvothermal reaction, and the self-supported hollow candied gourd-shaped electrocatalyst is obtained.

In the invention, the sulfur source in the sulfur source-containing solution is preferably thioacetamide, thiourea, sodium sulfide or cysteine, the concentration of the sulfur source in the sulfur source-containing solution is 0.044mol/L, and the solvent used in the sulfur source-containing solution is preferably ethanol; the mass ratio of the sulfur source to the nickel molybdenum oxide @ ZIF-67 in the sulfur source-containing solution is preferably (3.5-5): 1, and more preferably 4.16: 1.

In the invention, the nickel molybdenum oxide @ ZIF-67 is preferably mixed with the sulfur source-containing solution by immersing the nickel molybdenum oxide @ ZIF-67 in the sulfur source-containing solution and stirring for 30 min.

In the invention, the temperature of the solvothermal reaction is preferably 120-150 ℃, and the time is preferably 4-6 h; the solvothermal reaction is preferably carried out in a teflon lined stainless steel autoclave.

During the solvothermal reaction, the sulphur source is hydrolysed to form S ^2- Anion and Co on the surface of the shell ZIF-67 ²⁺ Reacting to generate cobalt sulfide; when Co is present ²⁺ After the ions are consumed, S ^2- Further with NiMoO in the inner core ₄ ·xH ₂ Ni on the surface of O reacts (preferentially reacts with Ni because Ni is more chemically active than Mo) to obtain nickel sulfide, but does not react with molybdenum ions to obtain molybdenum sulfide, the amount of sulfur source is excessive relative to cobalt ions but insufficient to react with metal ions Mo, and the amount of sulfur source is insufficient to react with NiMoO ₄ ·xH ₂ O is completely reacted, so that NiMoO is not damaged ₄ ·xH ₂ The structure of O.

After the solvothermal reaction is finished, the obtained product is preferably naturally cooled, washed and dried in sequence to obtain the self-supporting hollow candied gourd-shaped electrocatalyst marked as NiMoO ₄ ·xH ₂ O @ Ni-Co-S. In the present invention, the washing reagent is preferably absolute ethanol; the drying mode is preferably vacuum drying, the drying temperature is preferably 60 ℃, and the drying time is preferably 12 hours.

The invention provides a self-supporting hollow candied gourd-shaped electrocatalyst prepared by the preparation method in the technical scheme, which comprises a nickel-molybdenum oxide-nickel composite inner core and a hollow Ni-Co-S nano cage shell. The electrocatalyst is in a hollow sugar-gourd-shaped core-shell array structure.

The invention provides application of the self-supporting hollow candied gourd-shaped electrocatalyst in the technical scheme in the field of alkaline full-electrolytic cell water decomposition. The method of the present invention is not particularly limited, and the method may be applied according to a method known in the art.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

1) Mixing 1.5X 3cm ² Ultrasonically cleaning foam Nickel (NF) with different sizes in 1M HCl solution, deionized water and absolute ethyl alcohol in sequenceAfter 15min, vacuum drying at low temperature; the cleaned NF was placed in 30mL of a mixed solution containing 0.25g of nickel acetate (0.0014mol) and 0.2g of ammonium molybdate (0.00016mol), and the obtained solution was transferred to a Teflon-lined autoclave and reacted at 180 ℃ for 10 hours; after the reaction kettle is cooled, washing the foamed nickel by deionized water and ethanol for several times in sequence, and drying for 12 hours in vacuum at the temperature of 60 ℃ to obtain NiMoO ₄ ·xH ₂ O/NF；

2) 0.36g (0.0012mol) of Co (NO) ₃ ) ₂ ·6H ₂ Dissolving O in 20mL of methanol to obtain a cobalt salt solution; dissolving 0.82g (0.01mol) of 2-methylimidazole (2-MIM) in 20mL of methanol to obtain a 2-methylimidazole solution; the NiMoO obtained in the step (1) is treated ₄ ·xH ₂ Immersing O/NF in cobalt salt solution, stirring for 5 minutes, then dropwise adding 2-methylimidazole solution into the cobalt salt solution while stirring, continuously stirring for 30 minutes, cleaning the electrode with absolute ethyl alcohol, and drying at 60 ℃ for 6 hours to obtain the sugarcoated haws NiMoO ₄ ·xH ₂ O@ZIF-67；

3) 12mg of the sugarcoated haws NiMoO obtained in the step (2) ₄ ·xH ₂ Soaking O @ ZIF-67 in 15mL ethanol solution containing 50mg Thioacetamide (TAA), stirring for 30min, transferring the obtained solution to a 25mL stainless steel autoclave with a Teflon lining, reacting at 120 ℃ for 6h, naturally cooling the autoclave, cleaning an electrode with absolute ethanol, and drying at 60 ℃ in vacuum for 12h to obtain the self-supporting hollow NiMoO with the shape of a sugarcoated haws ₄ ·xH ₂ O @ Ni-Co-S array electrocatalyst.

Example 2:

the only difference from example 1 is: in the step 2), the 2-methylimidazole solution is dropwise added into the cobalt salt solution, and stirring is continued for 15 min.

Example 3:

the only difference from example 1 is: in the step 2), dropwise adding the 2-methylimidazole solution into the cobalt salt solution, and continuously stirring for 45 min.

Example 4:

the only difference from example 1 is: the sulfide in the step 3) is thiourea.

Example 5:

the only difference from example 1 is: the sulfide in the step 3) is sodium sulfide.

Example 6:

the only difference from example 1 is: in step 3), the sulfide is cysteine.

Comparative example 1

Step 1): mixing 1.5X 3cm ² Ultrasonically cleaning foam Nickel (NF) with large size in 1M HCl solution, deionized water and absolute ethyl alcohol for 15min, and vacuum drying at low temperature; placing the cleaned NF in 30mL of mixed solution containing 0.25g of nickel acetate and 0.2g of ammonium molybdate, transferring the obtained solution into a Teflon-lined autoclave, and reacting at 180 ℃ for 10 h; after the reaction kettle is cooled, washing the foamed nickel by deionized water and ethanol for several times in sequence, and drying for 12 hours in vacuum at the temperature of 60 ℃ to obtain NiMoO ₄ ·xH ₂ O/NF；

2) 0.36g of Co (NO) ₃ ) ₂ ·6H ₂ Dissolving O in 20mL of methanol to obtain a cobalt salt solution; 0.82g 2-methylimidazole (2-MIM) was dissolved in 20mL methanol to give a 2-methylimidazole solution; the NiMoO obtained in the step (1) is treated ₄ ·xH ₂ Immersing O/NF in cobalt salt solution, stirring for 5 minutes, then dropwise adding 2-methylimidazole solution into the cobalt salt solution while stirring, continuously stirring for 30 minutes, cleaning the electrode with absolute ethyl alcohol, and drying at 60 ℃ for 6 hours to obtain the sugarcoated haws NiMoO ₄ ·xH ₂ O @ ZIF-67 array electrocatalyst.

Characterization and testing

1) The hollow sugarcoated haws NiMoO prepared in example 1 was taken ₄ ·xH ₂ The O @ Ni-Co-S array electrocatalyst is subjected to X-ray diffraction, scanning electron microscopy, transmission electron microscopy and element mapping tests respectively, and the results are shown in FIGS. 1 to 4.

As can be seen from FIG. 1, the prepared electrocatalyst mainly comprises NF and NiMoO ₄ ·xH ₂ O、Ni ₃ S ₂ And Co ₉ S ₈ Four phases of which Ni ₃ S ₂ The nickel in the nickel is mainly from NiMoO ₄ ·xH ₂ O。

As can be seen from FIGS. 2 and 3, the morphology of the prepared electrocatalyst mainly consists of nanorods and nanocages, and NiMoO is inside ₄ ·xH ₂ The O nanorod array provides a growing place for the outer nanocages to form a candied gourd core-shell structure, and meanwhile, fig. 3 further proves that the outer nanocages are hollow structures. The hollow sugarcoated haw-shaped structure not only enables the electrode material to have larger specific surface area and is beneficial to exposing more active sites, but also ensures that electrolyte can easily permeate the electrode due to abundant open space in the array, shortens the ion diffusion length and accelerates the reaction process.

Fig. 4 is an EDS spectrum of the corresponding elements in the electrocatalyst prepared in example 1, and the distribution of the elements in the electrocatalyst can be clearly observed from fig. 4. Co is mainly distributed on the shell, S is uniformly distributed in the core and the shell, and signals of Ni, Mo and O are stronger in the core than in the shell. This is because, when ZIF-67 is consumed, S is consumed ^2- The ions further react with the internal NiMoO ₄ ·xH ₂ O nanorod reacts, and Ni is preferentially formed because Ni has higher chemical activity than Mo ₃ S ₂ . Multiple valence-state-converted Ni and Co metal ions (with Ni) ²⁺ 、Ni ³⁺ 、Co ²⁺ And Co ³⁺ ) Not only more active sites are formed, but also the synergistic effect between the two is beneficial to improving the intrinsic activity of the catalyst, thereby improving the catalytic reaction of the catalyst. The tests show that the invention successfully prepares the hollow sugarcoated haws NiMoO ₄ ·xH ₂ O @ Ni-Co-S array electrocatalyst.

Test example 1

The electro-catalysis performance test is carried out by adopting CHI 660E electrochemical workstation produced by Shanghai Chenghua company, the hydrogen evolution performance and the oxygen evolution performance of the catalyst are tested by adopting a three-electrode system, Ag/AgCl is taken as a reference electrode, a carbon rod is taken as a counter electrode, and a hollow sugarcoated haws-shaped NiMoO is adopted ₄ ·xH ₂ The O @ Ni-Co-S array electrocatalyst was the working electrode, and the electrolyte was 1.0M KOH solution.

Taking the electrocatalysts prepared in example 1 and comparative example 1 and commercial Pt sheet catalysts to carry out HER linear voltammetry scanning under alkaline conditions, wherein the voltage range is-1 to-1.55V, and the scanning rate is 5-100 mV s ^-1 And standing for 1-10 s, wherein the measured linear voltammetry scanning curve is shown in figure 5. From FIG. 5It can be seen that the hollow sugarcoated haws NiMoO prepared by the invention ₄ ·xH ₂ The O @ Ni-Co-S array electrocatalyst exhibits excellent HER catalytic activity under alkaline conditions. At 10mA cm ^-2 The overpotential of 113mV is better than that of comparative example 1, and even can be compared with commercial Pt. In addition, the electrode can stably output 350mA cm under overpotential of 260mV ^-2 High current density without suffering from severe evolution of H ₂ The obvious interference of the bubbles is expected to be applied to industrial electrolytic water.

The hollow sugarcoated haws NiMoO prepared in example 1 was taken ₄ ·xH ₂ O @ Ni-Co-S array electrocatalyst, sugarcoated NiMoO prepared in comparative example 1 ₄ ·xH ₂ O @ ZIF-67 array electrocatalyst and commercial RuO ₂ the/NF catalyst is subjected to OER linear volt-ampere scanning under the alkaline condition, the voltage range is 0.2-0.7V, and the scanning rate is 5-100 mV s ^-1 And standing for 1-10 s, wherein the measured linear voltammetry scanning curve is shown in figure 6. As can be seen from FIG. 6, the hollow sugarcoated haws NiMoO of the present invention ₄ ·xH ₂ The O @ Ni-Co-S array electrocatalyst exhibits excellent OER catalytic activity under alkaline conditions. At 50mA cm ^-2 At a current density of 261mV is better than that of comparative example 1 and commercial RuO ₂ A catalyst. In addition, the electrode can stably output 350mA cm at an overpotential of 466mV ^-2 High current density without suffering from a severe evolution of O ₂ Significant disturbance of the bubbles.

Test example 2

Electrolytic water performance test: adopts a two-electrode system and adopts a hollow sugarcoated haws shape NiMoO ₄ ·xH ₂ And the O @ Ni-Co-S array electrocatalyst is used as a cathode and an anode, and a 1M KOH solution is used as an electrolyte to assemble the alkaline electrolytic water electrolyzer.

The self-supporting hollow sugarcoated haws-like NiMoO prepared in example 1 was taken separately ₄ ·xH ₂ O @ Ni-Co-S array electrocatalyst, sugarcoated haws-like NiMoO prepared in comparative example 1 ₄ ·xH ₂ Assembling an alkaline water decomposition electrolytic cell by using O @ ZIF-67 array electrocatalyst for carrying out a polarization curve test, wherein the voltage range is 1-2.5V, and the scanning rate is 5mV s ^-1 And is a quotient ofBy RuO ₂ The results of the test are shown in FIG. 7 for the NF catalyst comparison. Commercial RuO ₂ The preparation process of the/NF catalyst comprises the following steps: 10mg of catalyst (RuO) ₂ ) Adding into solution containing 980. mu.L ethanol and 20. mu.L 5% Nafion, and performing ultrasonic treatment for 30min to obtain uniformly dispersed ink solution; 200 μ L of the ink solution was applied to NF (1X 1 cm) ² ) Drying the obtained sample by hot air to obtain RuO ₂ /NF。

As can be seen from FIG. 7, the self-supporting hollow sugarcoated haws-like NiMoO of the present invention ₄ ·xH ₂ The O @ Ni-Co-S array electrocatalyst exhibits excellent water splitting catalytic activity. When the current density is 20mAcm ^-2 And 100mAcm ^-2 The cell voltage only needs 1.503V and 1.61V, respectively, which is superior to commercial Pt | RuO ₂ A catalyst.

Test example 3

1) NiMoO prepared in example 1 was used ₄ ·xH ₂ O @ Ni-Co-S electrodes as positive and negative electrodes, H was aligned by drainage in a two-electrode system at room temperature by means of a Hofmann device (FIG. 8) ₂ And O ₂ The test was carried out with an electrolyte of 1M KOH solution and a current density of 50mAcm by a constant current method ^-2 (ii) a In FIG. 8, 1mL indicates the corresponding starting position of the solution without starting the reaction; 45 minutes after 20.1mL, H ₂ After a volume corresponding to the deposition of 10mL for 45 minutes, O ₂ The corresponding volume was isolated. Collecting H generated in the U-shaped electrolytic cell in different time periods by a drainage method ₂ /O ₂ The results of the measurements are shown in FIG. 9.

As can be seen from FIG. 9, the cathode/anode yield H ₂ And O ₂ The volume ratio of (A) to (B) is 2:1, and is consistent with a theoretical value, which shows that the self-supporting hollow sugarcoated haws NiMoO ₄ ·xH ₂ The O @ Ni-Co-S array electrocatalyst is an effective water electrolysis catalyst.

2) And (3) testing the full hydrolytic stability: self-supporting hollow sugarcoated NiMoO prepared as described in example 1 in a two-electrode cell ₄ ·xH ₂ The O @ Ni-Co-S array electrocatalyst is used as a positive electrode and a negative electrode, the electrolyte is 1.0M KOH, and a transverse voltage test method is adopted to measure NiMoO ₄ ·xH ₂ The durability of the bulk water splitting at a continuous potential of 1.51V for O @ Ni-Co-S/NF is shown in FIG. 10. As can be seen from FIG. 10, the prepared electrocatalyst has durability.

As can be seen from the above examples and test examples, the self-supporting hollow sugarcoated haws NiMoO prepared by the present invention ₄ ·xH ₂ The O @ Ni-Co-S array electrocatalyst shows excellent electrolytic water catalytic activity and mainly benefits from the following points: (1) the active material grows on the foamed nickel substrate, so that the use of a polymer adhesive is avoided, the contact internal resistance of the active material and the conductive substrate is reduced, and the rapid desorption of gas is realized; but also increases the contact area of the electrode and the electrolyte and improves the electronic conductivity; (2) the hollow sugarcoated haw array structure not only enables the electrocatalyst to have larger specific surface area and is beneficial to exposing more active sites, but also ensures that electrolyte can easily permeate into the electrode due to abundant open space in the array, shortens the ion diffusion length and accelerates the reaction process; (3) the synergistic effect of the Ni ions and the Co ions in multiple valence states can enhance the intrinsic activity of the catalyst, thereby accelerating the reaction kinetics and further improving the reaction efficiency of the electrolyzed water.

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 amendments can be made without departing from the principle of the present invention, and these modifications and amendments should also be considered as the protection scope of the present invention.

Claims

1. A preparation method of a self-supporting hollow candied gourd-shaped electrocatalyst comprises the following steps:

2. The method of claim 1, wherein the molybdenum source comprises ammonium molybdate or sodium molybdate and the nickel source comprises nickel acetate, nickel nitrate or nickel chloride.

3. The preparation method according to claim 1, wherein the molar ratio of the nickel source to the molybdenum source is 1:1 to 10: 1; the temperature of the hydrothermal reaction is 140-180 ℃, and the time is 6-10 h.

4. The preparation method according to claim 1, wherein the divalent cobalt salt in the divalent cobalt salt-containing solution is cobalt nitrate, cobalt chloride, cobalt acetate or cobalt sulfate; the concentration of the divalent cobalt salt solution is 0.04-0.08 mol/L; the concentration of the 2-methylimidazole solution is 0.4-0.8 mol/L.

5. The method according to claim 1 or 4, wherein the molar ratio of the 2-methylimidazole to the divalent cobalt salt in the divalent cobalt salt-containing solution is (0.08-0.16): (0.8-1.6); the mass ratio of the nickel-molybdenum oxide-nickel compound to the divalent cobalt salt is 0.006 (0.23-0.46).

6. The method of claim 1, wherein mixing the nickel molybdenum oxide-nickel composite, the divalent cobalt salt-containing solution, and the 2-methylimidazole solution comprises: putting the nickel-molybdenum oxide-nickel compound into a divalent cobalt salt solution, carrying out first mixing, and carrying out second mixing on the obtained mixed solution and a 2-methylimidazole solution; the first mixing time is 5-10 min; the second mixing time is 15-45 min.

7. The method according to claim 1, wherein the sulfur source in the sulfur source-containing solution is thioacetamide, thiourea, sodium sulfide or cysteine, and the concentration of the sulfur source in the sulfur source-containing solution is 0.044 mol/L.

8. The preparation method according to claim 1 or 7, wherein the temperature of the solvothermal reaction is 120-150 ℃ and the time is 4-6 h.

9. The self-supporting hollow sugarcoated haw-shaped electrocatalyst prepared by the preparation method of any one of claims 1 to 8, comprising a nickel molybdenum oxide-nickel composite inner core and a hollow Ni-Co-S nanocage outer shell.

10. Use of the self-supporting hollow candied gourd-shaped electrocatalyst according to claim 9 in the field of alkaline all-electrolytic cell water decomposition.