CN112376068B

CN112376068B - 3D catalytic material and preparation method and application thereof

Info

Publication number: CN112376068B
Application number: CN202011261161.8A
Authority: CN
Inventors: 杨晓进; 周博; 焦志伟; 唐阳; 万平玉
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2020-11-12
Filing date: 2020-11-12
Publication date: 2021-10-15
Anticipated expiration: 2040-11-12
Also published as: CN112376068A

Abstract

The invention provides a 3D catalytic material and a preparation method and application thereof, and relates to the technical field of water electrolysis. The 3D catalytic material provided by the invention comprises a 3D NiCu base material on which a Cu nanowire grows and a CoO nanosheet attached to the surface of the base material. According to the 3D catalytic material, a 3D NiCu material with good conductivity is used as a base material, a Cu nanowire grows on the surface of the 3D NiCu material and is coated by a CoO nanosheet, so that the 3D catalytic material has a macroscopic grid structure and a microscopic nanostructure, has a large specific surface area and an active site, can effectively promote the transfer of electrons, and improves the conductivity, and the 3D catalytic material provided by the invention has high electrocatalytic performance; the 3D catalytic material provided by the invention is applied to a cathode of electrolyzed water, and shows low hydrogen evolution overpotential, alternating current impedance value and Tafel slope, so that hydrogen production reaction by electrolyzed water is easier to carry out.

Description

3D catalytic material and preparation method and application thereof

Technical Field

The invention relates to the technical field of water electrolysis, in particular to a 3D catalytic material and a preparation method and application thereof.

Background

With the continuous development of modern industry, fossil energy is exploited and utilized in large quantities, so that the environment pollution and energy crisis caused by the fossil energy seriously threaten the survival and development of human beings, and the search of renewable clean energy is regarded as one of effective methods for breaking through the current embarrassment. Hydrogen energy is widely used because of its high energy density, easy storage and transportation, and no pollution. At present, over 5000 billions of cubic meters of hydrogen is required to be prepared in the world every year, most of the hydrogen is applied to industrial production, and hydrogen energy is also an important national strategic material and has irreplaceable effect in the aerospace field. Hydrogen energy is different from petroleum and natural gas, and hydrogen does not exist in nature, so that the preparation of hydrogen must be realized by a certain method. Therefore, the research of the high-efficiency artificial hydrogen production method is an important precondition for realizing the industrial production and application of hydrogen energy.

Water electrolysis is a clean, safe and efficient hydrogen energy preparation method, and the complex electron transfer process causes high overpotential in actual hydrogen production by water electrolysis, so that the hydrogen production by water electrolysis has large loss and low efficiency, and the application of the technology in industrial production is influenced. In the current research stage, Pt-based catalytic materials are considered to be the most effective catalysts in the hydrogen production reaction by electrolyzing water, however, the expensive Pt increases the cost of the Hydrogen Evolution Reaction (HER), and thus research on non-noble metal catalytic materials with high hydrogen production activity by electrolyzing water is gradually hot. Research shows that transition metal catalytic materials such as Co, Ni, Mo and Cu show good electrocatalytic activity in water electrolysis hydrogen production reaction, wherein NiCu alloy materials are widely researched as having high water electrolysis hydrogen production activity, but the problems of high hydrogen evolution overpotential, poor long-time reaction stability and the like still exist in alkaline water electrolysis, so that the development of an efficient, stable and cheap electrocatalytic material for water electrolysis hydrogen production is the focus of the current research.

Disclosure of Invention

The invention aims to provide a 3D catalytic material, 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 3D catalytic material for improving catalytic activity of hydrogen production by water electrolysis, which comprises a 3DNiCu base material with Cu nanowires growing and CoO nanosheets attached to the surface of the base material.

Preferably, the diameter of the Cu nanowire is 110-180 nm.

Preferably, the size of the CoO nanosheet is 70-100 nm; the mass content of Co in the 3D catalytic material is 2-5%.

Preferably, the mass ratio of Ni to Cu in the 3DNiCu substrate is 3: 2 to 7.

The invention provides a preparation method of the 3D catalytic material in the technical scheme, which comprises the following steps:

mixing Ni powder, Cu powder and a binder to obtain slurry;

preparing a 3DNiCu base material by adopting a direct-writing slurry 3D printing technology;

carrying out thermal oxidation treatment and electrochemical reduction on the 3DNiCu base material in sequence to obtain a 3DNiCu base material with Cu nanowires;

and (3) taking cobalt salt as electrolyte, and carrying out electrochemical deposition and sintering on the 3D NiCu substrate on which the Cu nanowires grow in sequence to obtain the 3D catalytic material for improving the catalytic activity of hydrogen production by water electrolysis.

Preferably, the particle size of the Ni powder is 200-500 meshes, the particle size of the Cu powder is 200-500 meshes, the binder is a polyvinyl alcohol aqueous solution, and the concentration of the polyvinyl alcohol aqueous solution is 5-15 wt%.

Preferably, the mass ratio of the Ni powder to the Cu powder is 3: 2-7; the mass ratio of the binder to the mixed metal powder of the Ni powder and the Cu powder is 6: 40 to 50.

Preferably, the temperature of the thermal oxidation treatment is 400-700 ℃, and the heat preservation time is 1-3 h; the heating rate from the room temperature to the thermal oxidation treatment temperature is preferably 5 to 10 ℃/min.

Preferably, the cobalt salt is cobalt nitrate or cobalt chloride; the sintering temperature is 200-500 ℃, and the sintering time is 1-3 h.

The invention also provides the application of the 3D catalytic material in the technical scheme or the 3D catalytic material prepared by the preparation method in the technical scheme in hydrogen production by water electrolysis.

The invention provides a 3D catalytic material for improving catalytic activity of hydrogen production by water electrolysis, which comprises a 3DNiCu base material with Cu nanowires growing and CoO nanosheets attached to the surface of the base material. According to the 3D catalytic material, a 3D NiCu material with good conductivity is used as a base material, a Cu nanowire grows on the surface of the 3D NiCu material and is coated by a CoO nanosheet, so that the 3D catalytic material has a macroscopic grid structure and a microscopic nanostructure, has a large specific surface area and an active site, can effectively promote the transfer of electrons, and improves the conductivity, and the 3D catalytic material provided by the invention has high electrocatalytic performance; the 3D catalytic material provided by the invention is applied to a cathode for electrolyzing water,the hydrogen production reaction by electrolyzing water is easier to be carried out due to the low hydrogen evolution overpotential, the low alternating current impedance value and the Tafel slope. The results of the examples show that the 3D catalytic material provided by the invention is used as a cathode in the alkaline medium electrolytic water reaction, and shows good electrocatalytic performance: the current density is 10mA/cm²The overpotential is 68mV, and the Tafel slope is 74mV dec^-1And the 3D catalytic material shows good stability in a hydrogen evolution experiment for 10 hours, and is a cheap, efficient and stable electrode material.

Drawings

FIG. 1 is a SEM image of a macro-grid structure of a 3DNiCu substrate prepared in example 1;

FIG. 2 is a microscopic spherical structure SEM image of the 3D NiCu substrate prepared in example 1;

fig. 3 is an SEM image of the 3DNiCu substrate grown with Cu nanowires prepared in example 1;

fig. 4 is an SEM image of the 3DNiCu substrate grown with Cu nanowires prepared in example 1;

FIG. 5 is an SEM image of the material obtained after electrochemical deposition of a 3DNiCu substrate with Cu nanowires grown as described in example 1;

FIG. 6 is an SEM image of a CoO @ CuNWs/3DNiCu catalytic material prepared in example 1;

FIG. 7 is a graph showing the distribution of Ni, Cu and Co elements in the preparation of a CoO @ CuNWs/3DNiCu catalytic material in example 1;

FIG. 8 is a graph of the HER performance results for the 3D catalytic materials prepared in examples 1-10;

fig. 9 is a graph of results of continuous electrolysis experiments of the 3D catalytic material.

Detailed Description

The invention provides a 3D catalytic material for improving catalytic activity of hydrogen production by water electrolysis, which comprises a 3DNiCu base material with Cu nanowires growing and CoO nanosheets attached to the surface of the base material. In the present invention, the 3d ni cu substrate is preferably a square grid structure, and in a specific embodiment of the present invention, the side length of the 3d ni cu substrate of the square grid structure is preferably 550 μm. In the present invention, the mass ratio of Ni and Cu in the 3DNiCu substrate is preferably 3: 2-7, more preferably 9: 11.

in the invention, the diameter of the Cu nanowire is preferably 110-180 nm, and more preferably 150 nm.

In the invention, the size of the CoO nanosheet is preferably 70-100 nm, and more preferably 80 nm; the mass content of Co in the 3D catalytic material is preferably 2-5%, and more preferably 3%.

The invention also provides a preparation method of the 3D catalytic material in the technical scheme, which comprises the following steps:

mixing Ni powder, Cu powder and a binder to obtain slurry;

preparing a 3D NiCu base material with a grid structure by adopting a direct-writing slurry 3D printing technology;

The invention mixes Ni powder, Cu powder and binder to obtain slurry. In the invention, the particle size of the Ni powder is preferably 200-500 meshes, and more preferably 300 meshes; the particle size of the Cu powder is preferably 200-500 meshes, and more preferably 300 meshes; the binder is preferably a polyvinyl alcohol aqueous solution, and the concentration of the polyvinyl alcohol aqueous solution is preferably 5-15 wt%, and more preferably 10 wt%. In the present invention, the mass ratio of the Ni powder to the Cu powder is preferably 3: 2-7, and particularly preferably 3: 2. 1: 1. 9: 11. 2: 3 or 3: 7; the mass ratio of the binder to the mixed metal powder of Ni powder and Cu powder is preferably 6: 40-50, more preferably 6: 45. the present invention has no special requirement on the specific mixing process, and the mixing process known to those skilled in the art can be adopted.

After the slurry is obtained, the 3D NiCu base material is prepared by adopting a direct-writing slurry 3D printing technology. In the present invention, the 3d ni cu substrate is preferably prepared by layer-by-layer printing. The invention preferably performs 3D printing via Simplify3D software; specifically, it is preferable that: a direct-writing 3D printer is adopted, high-pressure airflow is used as a driving force, the slurry is extruded, and the 3DNiCu base material is printed and molded in a layer-by-layer printing mode according to a software setting program.

The invention adopts simple direct-writing slurry 3D printing technology to prepare the base material, realizes the uniform printing of multi-metal materials with different densities through the particle sizes of Ni powder and Cu powder, and compared with the laser and melting 3D printing technology commonly used for metal 3D forming at present, the invention removes the limitation of the physical properties of metal raw materials on the 3D printing forming, realizes the 3D forming of NiCu bimetallic materials with different melting points and densities, and has better electro-catalysis performance compared with single metal materials. The direct-writing paste 3D printing technology adopted by the invention has the characteristics of simplicity in operation, low cost and the like, and is suitable for popularization in large-scale industrial production.

After the 3DNiCu base material is obtained, the 3DNiCu base material is subjected to thermal oxidation treatment and electrochemical reduction in sequence to obtain the 3DNiCu base material with the Cu nanowires. In the invention, the temperature of the thermal oxidation treatment is preferably 400-700 ℃, and more preferably 500 ℃; the heat preservation time is preferably 1-3 h, and more preferably 2 h; the rate of temperature increase from the room temperature to the thermal oxidation treatment temperature is preferably 5 to 10 ℃/min, more preferably 6 to 8 ℃/min. In the present invention, the thermal oxidation treatment is preferably performed in an air atmosphere. The invention realizes the redistribution of NiCu element through thermal oxidation treatment, so that Cu is migrated and enriched to the surface of the base material and CuO nanowire is formed. In the invention, the diameter of the CuO nanowire is preferably 180-500 nm, and more preferably 300 nm.

In the present invention, specific parameters of the electrochemical reduction preferably include: the reduction potential is-1.4V, and the reduction time is 10-20 min. The method reduces the CuO nanowire into the Cu nanowire through electrochemical reduction.

Before the thermal oxidation treatment, the present invention preferably further includes: the 3DNiCu substrate was degreased. In the invention, the degreasing treatment is preferably carried out in an argon atmosphere, so that the oxidation of metal nickel and copper is avoided while the effective removal of PVA is realized, and the subsequent thermal oxidation treatment on the material is avoided. In the present invention, the temperature control program of the degreasing treatment preferably includes: raising the temperature from room temperature to 200-300 ℃ at a heating rate of 5 ℃/min, then raising the temperature to 300-500 ℃ at a heating rate of 2 ℃/min, then raising the temperature to 800-900 ℃ at a heating rate of 5 ℃/min, and keeping the temperature for 60 min. The invention effectively removes the binder in the base material through degreasing treatment.

After the 3D NiCu base material with the Cu nanowires is obtained, the 3D NiCu base material with the Cu nanowires is subjected to electrochemical deposition and sintering sequentially by taking cobalt salt as electrolyte, and the 3D catalytic material for improving catalytic activity of hydrogen production by water electrolysis is obtained. In the present invention, the cobalt salt is preferably cobalt nitrate or cobalt chloride; the concentration of the cobalt salt is preferably 0.05-0.3 mol/L, and more preferably 0.1-0.2 mol/L.

In the present invention, the electrochemical deposition is preferably potentiostatic electrochemical deposition, the potentiostatic deposition potential preferably being from-1.0 to-1.2V, more preferably-1.0V (vs. SCE). In the electrochemical deposition process, cobalt ions in the cobalt salt electrolyte migrate to the working electrode 3DNiCu and are deposited on the surface of the electrode.

In the invention, the sintering temperature is preferably 200-500 ℃, and more preferably 300-400 ℃; the sintering time is preferably 1-3 h, and more preferably 1-2 h. In the present invention, the sintering is preferably performed in an oxygen-containing atmosphere, more preferably in air. In the sintering process, the CoO loaded on the surface of the material through electrodeposition is oxidized to form a CoO nano sheet.

The invention also provides application of the 3D catalytic material prepared by the preparation method in the technical scheme in hydrogen production by water electrolysis, and particularly preferably the 3D catalytic material is used as a cathode material in hydrogen production by water electrolysis of an alkaline medium. In the present invention, the method for producing hydrogen by electrolyzing water preferably comprises: the 3D catalytic material is used as a cathode (working electrode), a platinum wire is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, a 1mol/LKOH solution is used as an electrolyte, and hydrogen is produced by electrolyzing water in the argon saturated electrolyte. In the present invention, the size of the 3D catalytic material is preferably 1X 0.15cm³。

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

Preparing 10 wt% of polyvinyl alcohol (PVA) solution as a binder, fully mixing 300-mesh Ni powder and 400-mesh Cu powder according to the mass ratio of Ni to Cu of 45:55, and mixing PVA with the mixed powder of Ni powder and Cu powder according to the mass ratio of 6: 45, preparing slurry;

the 3D NiCu base material is molded by adopting a direct-writing slurry 3D printing technology in a layer-by-layer printing mode; the 3DNiCu base material is of a square grid structure with the side length of 550 mu m;

removing PVA in the base material by programmed heating in a tubular furnace filled with argon; the temperature raising procedure is as follows: heating to 250 ℃ from 20 ℃ at a heating rate of 5 ℃/min, then heating to 450 ℃ at a heating rate of 2 ℃/min, then heating to 850 ℃ at a heating rate of 5 ℃/min, and preserving heat for 60min to obtain a degreased 3DNiCu base material;

introducing oxygen into the tubular furnace at a speed of 300mL/min, putting the degreased 3DNiCu base material into the tubular furnace, heating to 500 ℃ at a heating rate of 5 ℃/min, keeping for 1h, performing thermal oxidation treatment, and then realizing the generation of the Cu nanowire on the surface of the 3DNiCu base material through electrochemical reduction (adopting-1.4V vs. SCE potential reduction for 10-20 min until a current curve is stable), so as to obtain the 3DNiCu base material (CuNWs/3DNiCu) with the Cu nanowire;

and taking 0.1mol/L cobalt nitrate aqueous solution as electrolyte, performing electrochemical deposition by adopting a constant potential of-1.0V (vs. SCE), and sintering in a muffle furnace at 300 ℃ for 1h to realize the coating of the CoO nanosheet on the surface of the material, thereby preparing the CoO @ CuNWs/3DNiCu catalytic material.

Examples 2 to 5

The manufacturing method is basically the same as that of example 1, except that the mass ratio of the Ni powder to the Cu powder is 3: 2(NiCu40), 1: 1(NiCu50), 2: 3(NiCu60) and 3: 7(NiCu 70).

Examples 6 to 8

The same preparation method as that of example 1 was followed except that the sintering temperatures were 200 deg.C, 400 deg.C and 500 deg.C, respectively.

Examples 9 to 10

The preparation method is basically the same as that of the example 1, except that the sintering time is 2h and 3h respectively.

Examples 11 to 13

Substantially the same as the preparation method of example 1 except that the temperatures of the thermal oxidation treatment were 400 c, 600 c and 700 c, respectively.

Test example 1

The morphology and structure of the sample were observed by using a Japanese JEOL JSM-7001F type thermal field emission Scanning Electron Microscope (SEM) and EDS-mapping.

The SEM image of the macro-grid structure of the 3d ni cu substrate prepared in example 1 is shown in fig. 1, and the SEM image of the micro-spherical structure of the 3d ni cu substrate is shown in fig. 2. As can be seen from fig. 1 to 2, the 3d ni cu substrate is composed of spherical powder, and the microscopic spherical structure and the macroscopic gridding structure of the material contribute to further modification of the 3d ni cu substrate.

SEM images of 3D NiCu substrate with Cu nanowires grown prepared in example 1 are shown in FIGS. 3-4, wherein the diameter of the Cu nanowires is 150 nm.

The SEM image of the material obtained after electrochemical deposition of the 3d ni Cu substrate with Cu nanowires grown as described in example 1 is shown in fig. 5, and it can be seen that Co coating on the surface of the material is achieved.

The SEM image of the CoO @ CuNWs/3DNiCu catalytic material prepared in example 1 is shown in FIG. 6, and as can be seen from FIG. 6, a uniform CoO nanosheet structure is formed outside the cladding layer.

Example 1 distribution of Ni element, Cu element and Co element in the process of preparing CoO @ CuNWs/3DNiCu catalytic material is shown in fig. 7, and as can be seen from fig. 7, Ni and Cu in the print-formed 3DNiCu substrate are uniformly distributed as shown in a in fig. 7; carrying out thermal oxidation treatment on the 3DNiCu base material subjected to printing and forming, wherein the distribution of NiCu elements in the material is changed, and under the oxidation condition of 500 ℃, Cu elements with relatively low melting points migrate and enrich to the surface of the material, as shown in b in FIG. 7; forming a Cu nanowire on the surface of the material after one-step electrochemical reduction; in fig. 7, c is the element distribution in the material after Co electrochemical deposition of the material subjected to thermal oxidation treatment, and the Co element can be found to be uniformly distributed in the material, which indicates that Co is effectively deposited on the surface of the material.

Test example 2

The electrocatalytic properties of the material were analyzed using a model CHI-760e electrochemical workstation.

The invention adopts a standard three-electrode system to test the electrocatalytic performance of the CoO @ CuNWs/3DNiCu catalytic material prepared in the embodiment 1-10: the CoO @ CuNWs/3DNiCu catalytic material prepared in the embodiment 1-10 is used as a cathode (working electrode), a platinum wire is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, a 1mol/LKOH solution is used as an electrolyte, water electrolysis is carried out in the argon saturated electrolyte to prepare hydrogen, the HER performance of the prepared material is tested, and the obtained results are shown in FIG. 8, and all potentials are converted into Reversible Hydrogen Electrodes (RHE);

a in fig. 8 is the HER polarization curves for different ratios of 3DNiCu substrates, which by comparison show that the material has the best HER performance when the NiCu mass ratio is 45:55, and thus the ratio is the best ratio for preparing 3 DNiCu; b in fig. 8 is the effect of the thermal oxidation treatment temperature on the HER performance of the 3DNiCu substrate, and 500 ℃ is found to be the optimum thermal oxidation treatment temperature by comparison of HER polarization curves; c in fig. 8 is the effect of sintering temperature on CoO @ CuNWs/3 dnicucher performance, and the material was found to exhibit the best HER performance at 300 ℃ by comparison of HER polarization curves; FIG. 8, d, compares the HER performance of the 3DNiCu substrate, CuNWs/3DNiCu and CoO @ CuNWs/3DNiCu catalytic materials, indicating that CoO @ CuNWs/3DNiCu has higher current density at the same potential, when the current density reaches 10mA/cm²The overpotential is 68 mv; in FIG. 8, e and f are Tafel slope and AC impedance values of 3DNiCu substrate, CuNWs/3DNiCu and CoO @ CuNWs/3DNiCu, respectively. By contrast, CoO @ CuNWs/3DNiCu has a lower Tafel slope and AC impedance value, indicating that CoO @ CuNWs/3DNiCu is more prone to HER progression than 3DNiCu and CuNWs/3DNiCu catalytic materials.

The electrochemical test results are integrated, and the CoO @ CuNWs/3DNiCu catalytic material has the highest HER catalytic activity, and the excellent HER catalytic activity is benefited by the fact that a 3D grid structure of a Cu nanowire grown by coating a CoO nanosheet has a large electrochemical active surface area and more active point sites, so that an electrolyte is easy to contact with the catalytic material, and in addition, a NiCu base material prepared by adopting a 3D printing technology has good conductivity, and the reaction kinetics is promoted. RHE was applied at 80mV (vs. RHE) for 10 hours, and as shown in FIG. 9, the current density of the material did not decay significantly during the 10 hours of electrolysis, indicating that the CoO @ CuNWs/3DNiCu catalytic material had good stability in 1M KOH solution.

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. A3D catalytic material for improving catalytic activity of hydrogen production by water electrolysis comprises a 3D NiCu substrate on which Cu nanowires grow and a CoO nanosheet attached to the surface of the substrate.

2. The 3D catalytic material of claim 1, wherein the Cu nanowires have a diameter of 110-180 nm.

3. The 3D catalytic material of claim 1, wherein the CoO nanoplates are 70-100 nm in size; the mass content of Co in the 3D catalytic material is 2-5%.

4. The 3D catalytic material of any of claims 1-3, wherein the mass ratio of Ni to Cu in the 3D NiCu substrate is 3: 2 to 7.

5. A method for preparing a 3D catalytic material according to any of claims 1 to 4, comprising the steps of:

mixing Ni powder, Cu powder and a binder to obtain slurry;

6. The method according to claim 5, wherein the Ni powder has a particle size of 200 to 500 mesh, the Cu powder has a particle size of 200 to 500 mesh, the binder is an aqueous polyvinyl alcohol solution, and the concentration of the aqueous polyvinyl alcohol solution is 5 to 15 wt%.

7. The production method according to claim 6, wherein the mass ratio of the Ni powder to the Cu powder is 3: 2-7; the mass ratio of the binder to the mixed metal powder of the Ni powder and the Cu powder is 6: 40 to 50.

8. The preparation method according to claim 5, wherein the temperature of the thermal oxidation treatment is 400-700 ℃, and the holding time is 1-3 h; the temperature rise rate from the room temperature to the thermal oxidation treatment temperature is 5-10 ℃/min.

9. The method according to claim 5, wherein the cobalt salt is cobalt nitrate or cobalt chloride; the sintering temperature is 200-500 ℃, and the sintering time is 1-3 h.

10. Use of the 3D catalytic material according to any one of claims 1 to 4 or the 3D catalytic material prepared by the preparation method according to any one of claims 5 to 9 in hydrogen production by water electrolysis.