阅读说明：本技术 一种异质结构的双功能自支撑电极及其制备方法和应用 (Dual-functional self-supporting electrode with heterostructure and preparation method and application thereof ) 是由 彭生杰 王辉 李林林 于 2021-07-09 设计创作，主要内容包括：本发明属于电催化技术领域,具体公开了一种异质结构的双功能自支撑电极及其制备方法和应用。本发明的电极在多孔导电基底上原位生长有Fe-2O-3纳米片和CuO四面体纳米颗粒,且CuO四面体纳米颗粒均匀附着在Fe-2O-3纳米片上,形成了二维异质结构的自支撑电极。这种二维异质结构使得该电极具有更大的比表面积,暴露出更多的活性位点,调整了电极材料的电子结构；加之多孔导电基底的自支撑结构保证了金属氧化物电极的高导电性,并实现了活性组分与导电基底的有效整合,这些性质相互协调,大大提高了自支撑电极的催化反应活性。实验结果表明,本发明的自支撑电极具有较高的电化学性能和稳定性,在碱性电解液中具有优异的析氢和析氧反应活性。(The invention belongs to the technical field of electrocatalysis, and particularly discloses a bifunctional self-supporting electrode with a heterostructure as well as a preparation method and application thereof. The electrode of the invention is grown with Fe in situ on a porous conductive substrate 2 O 3 Nanosheets and CuO tetrahedral nanoparticles, and the CuO tetrahedral nanoparticles are uniformly attached to the Fe 2 O 3 On the nano-sheet, a self-supporting electrode with a two-dimensional heterostructure is formed. The two-dimensional heterostructure enables the electrode to have a larger specific surface area, exposes more active sites and adjusts the electronic structure of the electrode material; in addition, the self-supporting structure of the porous conductive substrate ensures the high conductivity of the metal oxide electrode, realizes the effective integration of active components and the conductive substrate, and greatly improves the catalysis of the self-supporting electrode due to the mutual coordination of the propertiesAnd (4) activation of reaction. Experimental results show that the self-supporting electrode has high electrochemical performance and stability, and has excellent hydrogen evolution and oxygen evolution reaction activities in alkaline electrolyte.)

1. A heterostructure dual function self-supporting electrode, comprising: the electrode is grown with Fe in situ on a porous conductive substrate₂O₃Nanosheets and CuO tetrahedral nanoparticles, the CuO tetrahedral nanoparticles being uniformly attached to the Fe₂O₃And (4) nano-chips.

2. The heterostructured bifunctional self-supporting electrode according to claim 1, characterized in that: the porous conductive substrate is foamed nickel.

3. The heterostructured bifunctional self-supporting electrode according to claim 1, characterized in that: the in-situ growth of Fe on a porous conductive substrate₂O₃The method for preparing the nano-sheet and CuO tetrahedral nano-particles comprises the following steps: soluble ferric salt and soluble cupric salt are used as precursors, and Fe grows in situ on a porous conductive substrate through hydrothermal reaction with oxalate ligands under acidic conditions₂O₃Nanosheets and CuO tetrahedral nanoparticles; preferably, the soluble ferric salt is ferric nitrate, and/or the soluble copper salt is cupric nitrate, and/or the oxalate ligand is oxalic acid dihydrate, and the acidic condition is adjusted by oxalic acid dihydrate.

4. The heterostructured bifunctional self-supporting electrode according to claim 3, characterized in that: the molar ratio of the soluble ferric salt to the soluble cupric salt to the oxalate ligand is 1-2:1-2:2.5-5, preferably 1:1: 2.5; and/or, in the hydrothermal reaction system, the concentration of the oxalate ligand is 0.01-0.05mol/L, preferably 0.04 mol/L; and/or the mass ratio of the porous conductive substrate to the precursor is 1-2:1, preferably 1.65: 1; and/or the conditions of the hydrothermal reaction are as follows: the reaction is carried out at 160 ℃ and 200 ℃ for 16-24h, preferably at 200 ℃ for 24 h.

5. A method for preparing a heterostructured bifunctional self-supporting electrode according to any of claims 1 to 4, characterized in that: the method comprises the following steps: soluble ferric salt and soluble cupric salt are used as precursors, and Fe grows in situ on a porous conductive substrate through hydrothermal reaction with oxalate ligands under acidic conditions₂O₃Nanosheets and CuO tetrahedral nanoparticles.

6. The method of claim 5, wherein: the porous conductive substrate is foamed nickel.

7. The method of claim 5, wherein: the soluble ferric salt is ferric nitrate; and/or the soluble copper salt is copper nitrate; and/or the oxalate ligand is oxalic acid dihydrate, and the acidic condition is adjusted by the oxalic acid dihydrate.

8. The production method according to any one of claims 5 to 7, characterized in that: the molar ratio of the soluble ferric salt to the soluble cupric salt to the oxalate ligand is 1-2:1-2:2.5-5, preferably 1:1: 2.5; and/or, in the hydrothermal reaction system, the concentration of the oxalate ligand is 0.01-0.05mol/L, preferably 0.04 mol/L; and/or the mass ratio of the porous conductive substrate to the precursor is 1-2:1, preferably 1.65: 1; and/or the conditions of the hydrothermal reaction are as follows: the reaction is carried out at 160 ℃ and 200 ℃ for 16-24h, preferably at 200 ℃ for 24 h.

9. Use of a heterostructured bifunctional self-supporting electrode according to any of claims 1 to 4 or prepared according to the preparation method according to any of claims 5 to 8 for the electrolysis of water.

10. Use according to claim 9, characterized in that: the application is the application in the aspect of hydrogen production by water electrolysis; preferably, the hydrogen production by water electrolysis adopts alkaline electrolyte.

Technical Field

The invention belongs to the technical field of electrocatalysis, and particularly relates to a bifunctional self-supporting electrode with a heterostructure, a preparation method of the electrode, and application of the electrode in water electrolysis.

Background

Since the use of fossil fuels increases environmental pollution, a new energy source that can replace the conventional fossil fuels is urgently needed. The hydrogen energy is a new energy source which is considered to have the most application prospect, has higher energy density, is environment-friendly because the oxidation product is water, and is a green clean energy source. However, the currently widely favored technology for producing hydrogen by electrolyzing water still has many problems. For example, how to reduce overpotential of anodic oxygen evolution reaction and cathodic hydrogen evolution reaction, realize hydrogen production at low potential, how to reduce electric energy consumption and hydrogen production cost, etc. are all technical problems that need to be solved by technologists. Researches find that the noble metal electrode can effectively reduce overpotentials of the cathode and the anode during water electrolysis, but the abundance of the metal crust is low and the price is high, so that the large-scale application of the metal crust is limited. Therefore, it would be advantageous to develop a non-noble metal catalyst that is inexpensive and efficient to solve the above problems.

The basic idea of developing the non-noble metal catalyst at present is to change the electronic structure and the micro-morphology of the material by adjusting the composition (such as anion and cation doping), the special structure form (such as alloy, nuclear shell or heterostructure), the structure defect and the like, thereby improving the performance of the catalyst for hydrogen production by water electrolysis. For example, according to a self-supporting nitrogen-modified iron-nickel hydroxide electrolyzed water bifunctional electrode material disclosed in chinese patent CN110219013A, a NiFe-LDH precursor is prepared by a hydrothermal method, and then a nitrogen-modified NiFe-LDH nanosheet electrode material is prepared by a hydrothermal method with ammonia water as a nitrogen source. The patent synthesizes layered double metal hydroxide (NiFe-LDH) on a Ni-foam substrate in situ, which can not only utilize the conductivity of the Ni-foam substrate, but also reduce the resistance between the NiFe-LDH and the Ni-foam substrate through in situ synthesis; and then ammonia water is used as a nitrogen source, and nitrogen atoms are doped into the NiFe-LDH through a secondary hydrothermal reaction, so that the full water splitting performance of the electrode can be obviously improved. However, the preparation process of the patent is complex, needs secondary hydrothermal treatment and is not easy to operate.

Disclosure of Invention

The invention aims to provide a bifunctional self-supporting electrode with a heterostructure, which utilizes the design of the heterostructure to adjust the electronic structure of an electrode material and accelerate the electron transfer rate of a reaction interface, thereby improving the electrochemical performance of the electrode material and making up the disadvantage that the traditional metal oxide electrode can only be used as an oxygen evolution reaction electrode.

Meanwhile, the invention also provides a preparation method of the bifunctional self-supporting electrode with the heterostructure.

Finally, the invention further provides the application of the bifunctional self-supporting electrode with the heterostructure in the aspect of water electrolysis.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:

a heterostructured, bifunctional, self-supporting electrode with Fe grown in situ on a porous, electrically conductive substrate₂O₃Nanosheets and CuO tetrahedral nanoparticles, the CuO tetrahedral nanoparticles being uniformly attached to the Fe₂O₃And (4) nano-chips.

The self-supporting electrode of the invention is grown with Fe in situ on the porous conductive substrate₂O₃Nanosheets and CuO tetrahedral nanoparticles, wherein the CuO tetrahedral nanoparticles are uniformly attached to the Fe₂O₃On the nano-sheet, a self-supporting electrode with a two-dimensional heterostructure is formed. The two-dimensional heterostructure enables the electrode to have a larger specific surface area, so that more active sites are exposed, the electronic structure of the electrode material is adjusted, meanwhile, the self-supporting structure of the porous conductive substrate ensures high conductivity of the metal oxide electrode, the properties are coordinated with each other, and the performance of the active material is greatly promoted. The experimental result shows that the self-supporting electrode can be used with commercial Pt/C electrode and RuO₂The performance of the electrode is comparable with that of the electrode, and the electrode is an excellent difunctional electrolytic water electrode material.

As a preferred embodiment, the porous conductive substrate is preferably nickel foam (Ni-foam). The porous conductive substrate (such as foamed nickel) grows Fe in situ₂O₃Before nano sheets and CuO tetrahedral nano particles, impurities in the conductive substrate are removed by cleaning with a hydrochloric acid solution. The concentration of the hydrochloric acid solution is 0.05-0.3mol/L, and preferably 0.1 mol/L.

As a preferred embodiment, theIn-situ growth of Fe on porous conductive substrates₂O₃The method for preparing the nano-sheet and CuO tetrahedral nano-particles comprises the following steps: soluble ferric salt and soluble cupric salt are used as precursors, and Fe grows in situ on a porous conductive substrate through hydrothermal reaction with oxalate ligands under acidic conditions₂O₃Nanosheets and CuO tetrahedral nanoparticles. The soluble iron salt is preferably ferric nitrate (i.e., ferric nitrate nonahydrate).

As a preferred embodiment, the soluble copper salt is preferably copper nitrate (copper nitrate tetrahydrate).

In a preferred embodiment, the acidic conditions are adjusted with an organic acid,

as a preferred embodiment, oxalic acid dihydrate (i.e., oxalic acid) is preferred.

In a preferred embodiment, the oxalate ligand is an organic ligand, preferably oxalic acid dihydrate, in which case the acidic conditions can be adjusted by oxalic acid dihydrate. That is, oxalic acid dihydrate acts as both a ligand and an acidity regulator in this system. For example, oxalate anions tend to form complex intermediates with metal cations in solution, which decompose to produce metal oxides (Fe) of porous structure₂O₃)。

As a preferred embodiment, the hydrothermal reaction process is: putting soluble ferric salt (preferably ferric nitrate), soluble copper salt (preferably cupric nitrate), solvent (preferably deionized water) and oxalate ligand (preferably oxalic acid dihydrate) into a polytetrafluoroethylene lining for uniform dispersion, adding a porous conductive substrate (such as cleaned nickel foam), and then putting into a stainless steel reaction kettle for hydrothermal reaction to obtain the bifunctional self-supporting electrode with the heterostructure.

In a preferred embodiment, the molar ratio of the soluble iron salt (preferably ferric nitrate), the soluble copper salt (preferably cupric nitrate) and the oxalate ligand (preferably oxalic acid dihydrate) is 1-2:1-2:2.5-5, preferably 1:1: 2.5. In the hydrothermal reaction system, the concentration of the oxalate ligand is 0.01-0.05mol/L, preferably 0.04 mol/L. For example, 0.158g of oxalic acid dihydrate is added to 30mL of the solvent, and the soluble iron salt and the soluble copper salt are added in a molar ratio.

As a preferred embodiment, the dispersion is performed by ultrasonic dispersion, and the solution is uniformly dispersed without special requirements on the power, frequency and time of ultrasonic dispersion. For example, the frequency of ultrasonic dispersion is set to 80-120Hz, and the time is set to 5-20 min. Preferably, the frequency of ultrasonic dispersion is set to be 100Hz, and the time is set to be 10-12 min.

As a preferred embodiment, the mass ratio of the porous conductive substrate to the precursor (the sum of the soluble iron salt and the soluble copper salt) is 1-2:1, preferably 1.65: 1.

As a preferred embodiment, the hydrothermal reaction conditions are: reacting at 160-200 ℃ for 16-24 h. Preferably, the reaction is carried out at 200 ℃ for 24 h.

In a preferred embodiment, after completion of the hydrothermal reaction, the reaction mixture is cooled to room temperature, washed and dried. And the washing is sequentially washing with deionized water and absolute ethyl alcohol for 3-5 times respectively to remove impurities on the surface of the electrode. The drying is preferably vacuum drying at 50-80 deg.C for 10-15 hr, preferably at 60 deg.C for 12 hr.

A preparation method of a bifunctional self-supporting electrode with a heterostructure comprises the following steps: soluble ferric salt and soluble cupric salt are used as precursors, and Fe grows in situ on a porous conductive substrate through hydrothermal reaction with oxalate ligands under acidic conditions₂O₃Nanosheets and CuO tetrahedral nanoparticles.

The invention skillfully utilizes the reaction mechanism that oxalate ions are easy to complex with iron ions at low temperature and gradually decompose at high temperature to form a porous structure, and prepares the heterostructure metal oxide nano porous self-supporting electrode. The special morphology is beneficial to full contact between the electrolyte and active sites, and can effectively improve the catalytic reaction activity of the self-supporting electrode.

As a preferred embodiment, the porous conductive substrate is preferably nickel foam (Ni-foam). The porous conductive substrate (e.g., nickel foam) is in situGrowing Fe₂O₃Before nano sheets and CuO tetrahedral nano particles, impurities in the conductive substrate are removed by cleaning with a hydrochloric acid solution. The concentration of the hydrochloric acid solution is 0.05-0.3mol/L, and preferably 0.1 mol/L.

As a preferred embodiment, the soluble iron salt is preferably ferric nitrate (i.e., ferric nitrate nonahydrate).

As a preferred embodiment, the soluble copper salt is preferably copper nitrate (copper nitrate tetrahydrate).

As a preferred embodiment, the acidic conditions are adjusted with an organic acid, preferably oxalic acid dihydrate (i.e. oxalic acid).

In a preferred embodiment, the oxalate ligand is an organic ligand, preferably oxalic acid dihydrate, in which case the acidic conditions can be adjusted by oxalic acid dihydrate. That is, oxalic acid dihydrate acts as both a ligand and an acidity regulator in this system.

As a preferred embodiment, the hydrothermal reaction process is: putting soluble ferric salt (preferably ferric nitrate), soluble copper salt (preferably cupric nitrate), solvent (preferably deionized water) and oxalate ligand (preferably oxalic acid dihydrate) into a polytetrafluoroethylene lining for uniform dispersion, adding a porous conductive substrate (such as cleaned nickel foam), and then putting into a stainless steel reaction kettle for hydrothermal reaction to obtain the bifunctional self-supporting electrode with the heterostructure.

In a preferred embodiment, the molar ratio of the soluble iron salt (preferably ferric nitrate), the soluble copper salt (preferably cupric nitrate) and the oxalate ligand (preferably oxalic acid dihydrate) is 1-2:1-2:2.5-5, preferably 1:1: 2.5. In the hydrothermal reaction system, the concentration of the oxalate ligand is 0.01-0.05mol/L, preferably 0.04 mol/L. For example, 0.158g of oxalic acid dihydrate is added to 30mL of the solvent, and the amount of the precursor is added in a molar ratio.

As a preferred embodiment, the dispersion is performed by ultrasonic dispersion, and the solution is uniformly dispersed without special requirements on the power, frequency and time of ultrasonic dispersion. For example, the frequency of ultrasonic dispersion is set to 80-120Hz, and the time is set to 5-20 min. Preferably, the frequency of ultrasonic dispersion is set to be 100Hz, and the time is set to be 10-12 min.

As a preferred embodiment, the mass ratio of the porous conductive substrate to the precursor (the sum of the soluble iron salt and the soluble copper salt) is 1-2:1, preferably 1.65: 1.

As a preferred embodiment, the hydrothermal reaction conditions are: reacting at 160-200 ℃ for 16-24 h. Preferably, the reaction is carried out at 200 ℃ for 24 h.

In a preferred embodiment, after completion of the hydrothermal reaction, the reaction mixture is cooled to room temperature, washed and dried. And the washing is sequentially washing with deionized water and absolute ethyl alcohol for 3-5 times respectively to remove impurities on the surface of the electrode. The drying is preferably vacuum drying at 50-80 deg.C for 10-15 hr, preferably at 60 deg.C for 12 hr.

According to the invention, the nickel foam is preferably used as a substrate for preparing the heterostructure metal oxide nano porous self-supporting electrode, the weak acidic environment is adjusted by oxalic acid dihydrate, oxalate ions are easy to complex with iron ions at low temperature, and are gradually decomposed at high temperature to form a porous structure, and the special morphology is favorable for full contact of electrolyte and effective active sites, so that the reaction activity of the self-supporting electrode is improved. Experimental results show that the heterostructure metal oxide self-supporting electrode prepared by the method has high stability and electrochemical activity, and particularly has excellent hydrogen evolution and oxygen evolution reaction activity in alkaline electrolyte.

The application of a heterostructured bifunctional self-supporting electrode in water electrolysis.

As a preferred embodiment, the application is in particular in the field of hydrogen production by electrolysis of water.

In a preferred embodiment, the hydrogen production by water electrolysis is performed by using an alkaline electrolyte, preferably a KOH solution.

The invention has the beneficial effects that:

the invention integrates and prolongs the following strategies when preparing the bifunctional self-supporting electrode with the heterostructure:

(1) altering the morphology of the catalyst, particularly the electrochemically active component, to increase the actual surface area without altering the frequency of conversion (TOF) per site, thereby increasing the available active sites;

(2) through the design of a metal oxide heterostructure, the electronic structure of the electrode material is effectively adjusted, and the electron transfer rate of a reaction interface is accelerated, so that the electrochemical performance of the electrode material is improved;

(3) the active component of the electrode is integrated with the conductive substrate, so that the impedance of an electron transmission path is low, the possibility of physical layering is reduced, and the electron coupling between the conductive substrate and the active component generates a synergistic effect, thereby improving the intrinsic activity of the electrode.

The invention in-situ grows Fe with unique micro-morphology on the porous conductive substrate through hydrothermal reaction₂O₃The CuO composite electrode material realizes effective integration of active components and a conductive substrate, enhances the stability of the electrode material, greatly improves the electrocatalytic reaction activity of the bifunctional self-supporting electrode, has wide application prospect in the field of water electrolysis (especially in the aspect of hydrogen production by water electrolysis), and provides a new idea for preparation of similar self-supporting electrodes.

According to the invention, when the self-supporting electrode is prepared, the weakly acidic environment is adjusted by oxalic acid dihydrate, oxalate ions are easy to complex with iron ions at low temperature, and then the self-supporting electrode is gradually decomposed at high temperature of hydrothermal reaction to form a porous structure, and the special morphology is favorable for full contact of electrolyte and effective active sites, so that the reaction activity of the self-supporting electrode is improved, and the bifunctional self-supporting electrode with a heterostructure is obtained. Experimental results show that the self-supporting electrode prepared by the invention has high electrochemical activity and stability, and has excellent hydrogen evolution and oxygen evolution reaction activity in alkaline electrolyte.

The preparation method provided by the invention is simple and feasible to operate, mild in reaction conditions, cheap and easily available in raw materials and low in preparation cost, and the obtained self-supporting electrode has excellent electrocatalytic reaction activity and is expected to replace a traditional noble metal electrode for large-scale application.

Drawings

FIG. 1 is an SEM scanning electron micrograph of a self-supporting electrode prepared in example 1 of the present invention;

FIG. 2 is an X-ray diffraction pattern of a self-supporting electrode prepared in example 1 of the present invention;

FIG. 3 is a LSV curve of the hydrogen evolution reaction of a self-supporting electrode prepared in example 1 of the present invention;

FIG. 4 is an LSV curve of the oxygen evolution reaction of the self-supporting electrode prepared in example 1 of the present invention.

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings obtained in the experimental examples are briefly described above. It is understood that the above-mentioned drawings only show some experimental examples of the present invention and should not be considered as limiting the scope of protection of the claims in any way. For a person skilled in the art, it is possible to derive other relevant figures from these figures without inventive effort.

Detailed Description

In order to make the technical problems to be solved, the technical solutions adopted and the technical effects achieved by the present invention easier to understand, the technical solutions of the present invention are clearly and completely described below with reference to specific examples, comparative examples and experimental examples. It should be noted that the examples, comparative examples and experimental examples, in which specific conditions are not specified, were conducted according to conventional conditions or conditions recommended by the product manufacturer, and reagents, instruments and the like used therein were commercially available.

Example 1

The heterostructure bifunctional self-supporting electrode of this example was grown in situ with Fe on a porous conductive substrate₂O₃Nanosheets and CuO tetrahedral nanoparticles, wherein the CuO tetrahedral nanoparticles are uniformly attached to the Fe₂O₃And (4) nano-chips.

The preparation method of the heterostructure bifunctional self-supporting electrode of the embodiment comprises the following steps:

0.202g of iron nitrate nonahydrate, 0.13g of copper nitrate tetrahydrate, 0.158g of oxalic acid dihydrate and 30mL of deionized water were added to a polytetrafluoroethylene liner, ultrasonically dispersed at 100Hz for 10min, placed in a 2X 3cm cleaned Ni-foam substrate, then placed in a stainless steel reaction kettle, screwed down, placed in an oven, and the procedure was set: and (3) the temperature is 200 ℃ and the time is 1440min, after the reaction is finished, after the oven is cooled to room temperature, the electrode is taken out and washed by deionized water and absolute ethyl alcohol respectively for 3 times, and the electrode is dried in vacuum for 12 hours at the temperature of 60 ℃ to obtain the bifunctional self-supporting electrode with the heterostructure.

In other embodiments of the present invention, the amounts of the precursors were set to Fe: Cu 1:2 and Fe: Cu 2:1, respectively, and the same operations as in example 1 were performed to obtain LSV curves shown in fig. 3 and 4 as Fe/Cu 1:2 and Fe/Cu 2:1, respectively.

Example 2

The heterostructure bifunctional self-supporting electrode of this example was grown in situ with Fe on a porous conductive substrate₂O₃Nanosheets and CuO tetrahedral nanoparticles, wherein the CuO tetrahedral nanoparticles are uniformly attached to the Fe₂O₃And (4) nano-chips.

The preparation method of the heterostructure bifunctional self-supporting electrode of the embodiment comprises the following steps:

0.404g of iron nitrate nonahydrate, 0.13g of copper nitrate tetrahydrate, 0.158g of oxalic acid dihydrate and 30mL of deionized water were added to a polytetrafluoroethylene liner, ultrasonically dispersed at 100Hz for 10min, placed in a 2X 3cm cleaned Ni-foam substrate, then placed in a stainless steel reaction kettle, screwed down, placed in an oven, and the procedure was set: and (3) cooling the electrode to room temperature in an oven after the reaction is finished at 160 ℃ for 960min, taking out the electrode, sequentially washing the electrode for 3 times by using deionized water and absolute ethyl alcohol respectively, and drying the electrode for 12 hours in vacuum at 60 ℃ to obtain the bifunctional self-supporting electrode with the heterostructure.

Example 3

The heterostructure bifunctional self-supporting electrode of this example was grown in situ with Fe on a porous conductive substrate₂O₃Nanosheets and CuO tetrahedral nanoparticles, wherein the CuO tetrahedral nanoparticles are uniformly attached to the Fe₂O₃And (4) nano-chips.

The preparation method of the heterostructure bifunctional self-supporting electrode of the embodiment comprises the following steps:

0.202g of iron nitrate nonahydrate, 0.26g of copper nitrate tetrahydrate, 0.158g of oxalic acid dihydrate and 30mL of deionized water were added to a polytetrafluoroethylene liner, ultrasonically dispersed at 100Hz for 12min, placed in a 2X 3cm cleaned Ni-foam substrate, then placed in a stainless steel reactor and screwed down, placed in an oven, and the procedure was set: and (3) the temperature is 180 ℃ and the time is 1440min, after the reaction is finished, after the oven is cooled to room temperature, the electrode is taken out and washed by deionized water and absolute ethyl alcohol respectively for 3 times, and the electrode is dried in vacuum for 12 hours at the temperature of 60 ℃, so that the bifunctional self-supporting electrode with the heterostructure is obtained.

Comparative example 1

The single-phase self-supporting electrode of this comparative example had Fe grown in situ on a porous conductive substrate₂O₃Nanosheets.

The preparation method of the single-phase self-supporting electrode of the comparative example comprises the following steps:

adding 0.202g of ferric nitrate nonahydrate, 0.158g of oxalic acid dihydrate and 30mL of deionized water into a polytetrafluoroethylene lining, ultrasonically dispersing for 12min at the frequency of 100Hz, then putting the mixture into a 2X 3cm cleaned Ni-foam substrate, then putting the substrate into a stainless steel reaction kettle, screwing the substrate tightly, putting the substrate into an oven, and setting the program: the temperature is 200 ℃, the time is 1440min, after the reaction is finished, after the oven is cooled to the room temperature, the electrode is taken out and washed respectively with deionized water and absolute ethyl alcohol for 3 times, and vacuum drying is carried out for 12h at the temperature of 60 ℃, and the single-phase loaded Fe is obtained₂O₃A self-supporting electrode.

Comparative example 2

The single-phase self-supporting electrode of the comparative example has CuO nano-sheets grown in situ on a porous conductive substrate.

The preparation method of the single-phase self-supporting electrode of the comparative example comprises the following steps:

adding 0.13g of copper nitrate tetrahydrate, 0.158g of oxalic acid dihydrate and 30mL of deionized water into a polytetrafluoroethylene lining, ultrasonically dispersing for 12min at the frequency of 100Hz, then putting the mixture into a cleaned Ni-foam substrate of 2 x 3cm, then putting the mixture into a stainless steel reaction kettle, screwing the mixture, putting the mixture into an oven, and setting the program: and (3) the temperature is 200 ℃ and the time is 1440min, after the reaction is finished, after the oven is cooled to room temperature, the electrode is taken out and washed by deionized water and absolute ethyl alcohol respectively for 3 times, and vacuum drying is carried out for 12 hours at the temperature of 60 ℃ to obtain the single-phase loaded CuO self-supporting electrode.

In other comparative examples of the present invention, Pt/C, RuO was prepared separately₂The electrode is prepared by the following steps: separately purchasing Pt/C, RuO₂Mixing and grinding the powder sample, conductive carbon and a binder according to a certain proportion, and then coating the mixture on foamed nickel to obtain Pt/C or RuO₂The electrode and the performance test result of the electrode are respectively shown in Pt/C, RuO in FIG. 3 and FIG. 4₂The LSV curve is shown.

Examples of the experiments

(1) SEM scanning Electron microscopy analysis

SEM scanning electron microscope analysis of the self-supporting electrode prepared in example 1 is shown in FIG. 1.

As can be seen from FIG. 1, Fe₂O₃Is of a nano-sheet structure, CuO is of a tetrahedral block structure (nano), in Fe₂O₃The nano-sheet is evenly grown with CuO tetrahedral blocks, which shows that CuO is successfully compounded on Fe₂O₃A heterostructure is formed.

(2) XRD analysis

The self-supporting electrode prepared in example 1 was taken, and a sample of the powder was ultrasonically collected for XRD characterization and analysis, and the results are shown in FIG. 2.

As can be seen from FIG. 2, Fe₂O₃Corresponding to the standard card peak shape, the CuO peak is approximately in the vicinity of 2 theta to 40, and can be matched with Fe₂O₃CuO corresponds to CuO in CuO, indicating that example 1 successfully produced Fe₂O₃The composite electrode material is/CuO.

(3) HER test

The self-supporting electrodes of the examples and the electrodes of the comparative examples were used to form a three-electrode system, in which Ag/AgCl was used as a reference electrode, a carbon rod was used as a counter electrode, and the electrodes of the examples and comparative examples were used as working electrodes, and HER performance tests were performed in a 1.0M KOH solution, and the results are shown in fig. 3.

As can be seen from FIG. 3, the overpotential of the electrode prepared in the example of the present invention is 54mV at 10mA current, which is close to 38mV of the Pt/C electrode at 10mA current.

As can be seen from fig. 3, among the self-supporting electrodes prepared from different ratios of iron and copper salts, the electrode HER performance is best when Fe: Cu ═ 1:1, the electrode with Fe: Cu ═ 2:1 and Fe: Cu ═ 1:2, and the single-phase Fe are best₂O₃The HER performance of CuO electrodes was slightly inferior.

(4) OER test

The self-supporting electrode of the example and the electrode of the comparative example were used to form a three-electrode system, in which Ag/AgCl was used as a reference electrode, a platinum sheet was used as a counter electrode, and the electrodes of the example and the comparative example were used as working electrodes, respectively, and the results of the OER performance test were shown in fig. 4.

As can be seen from FIG. 4, the potential of the electrode prepared in the example of the present invention at 10mA current was 1.46V, exceeding RuO₂The overpotential of the electrode at 10mA current is 1.52V.

As can be seen from fig. 4, among the self-supporting electrodes prepared from different ratios of iron and copper salts, the electrode OER performance of Fe: Cu ═ 1:1 is the best, the electrode of Fe: Cu ═ 2:1, Fe: Cu ═ 1:2 and the single-phase Fe are the best₂O₃The OER performance of CuO electrodes is slightly inferior.

The experimental results show that the prepared bifunctional self-supporting electrode with the heterostructure has good electrochemical activity and stability, particularly has excellent hydrogen evolution and oxygen evolution reaction activity in alkaline electrolyte, and has the performance similar to that of a commercial Pt/C electrode and RuO₂The electrode is comparable to the electrode and is an excellent difunctional electrolytic water electrode material.

According to the preparation method, the weakly acidic environment is adjusted through the oxalic acid dihydrate, oxalate ions are easy to complex with iron ions at low temperature, and then the oxalic acid dihydrate is gradually decomposed at high temperature of hydrothermal reaction to form a porous structure, so that the special morphology is beneficial to full contact of electrolyte and effective active sites, and the catalytic reaction activity of the self-supporting electrode is improved. The invention grows Fe with heterostructure on the porous conductive substrate in situ₂O₃the/CuO composite electrode material realizes effective integration of active components and a conductive substrate, enhances the stability and greatly improves the difunctional self-supporting propertyThe electrocatalytic reaction activity of the electrode provides a new idea for the preparation of similar self-supporting electrodes.

The preparation method provided by the invention is simple and feasible to operate, relatively mild in reaction conditions, low in raw material cost, and good in performance of the obtained bifunctional electrode, and has a wide application prospect in the field of water electrolysis (especially in the aspect of hydrogen production by water electrolysis).

The above are only preferred examples and experimental examples of the present invention, and do not limit the scope of the present invention. Many variations and/or modifications in the specific implementation of the invention may occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.