阅读说明：本技术 弱酸盐层保护的析氧催化电极及其制备与用途、及提高析氧催化电极析氧反应稳定性的方法 (Oxygen evolution catalytic electrode protected by weak acid salt layer, preparation and application thereof, and method for improving stability of oxygen evolution reaction of oxygen evolution catalyt) 是由 邝允 张兴恒 孙晓明 于 2021-08-25 设计创作，主要内容包括：本发明属于无机材料合成技术领域以及电化学电解水技术领域,具体涉及一种析氧电极及其制备与用途,以及一种提高析氧电极析氧反应稳定性的方法。所述电极包括:载体和负载在所述载体上的析氧催化剂,所述电极的表面受弱酸盐层保护。本发明使用弱酸盐调控电解液的组分或者将弱酸盐溶液滴涂到析氧催化电极上,使弱酸盐离子在析氧催化剂表面附着,形成一层弱酸盐层。弱酸盐的水解作用会缓冲催化剂表面的pH变化,并通过配位作用稳定催化剂表层原子,抑制金属离子溶出,起到保护催化剂的结构和性能的作用,提高其在大电流长时间的工作条件下的稳定性。(The invention belongs to the technical field of inorganic material synthesis and the technical field of electrochemical water electrolysis, and particularly relates to an oxygen evolution electrode, preparation and application thereof, and a method for improving the stability of the oxygen evolution reaction of the oxygen evolution electrode. The electrode comprises a carrier and an oxygen evolution catalyst loaded on the carrier, and the surface of the electrode is protected by a weak acid salt layer. The invention uses weak acid salt to regulate and control the components of the electrolyte or coats the weak acid salt solution on the oxygen evolution catalytic electrode, so that weak acid salt ions are attached to the surface of the oxygen evolution catalyst to form a weak acid salt layer. The hydrolysis action of the weak acid salt can buffer the pH change of the surface of the catalyst, stabilize atoms on the surface layer of the catalyst through coordination action, inhibit the dissolution of metal ions, play a role in protecting the structure and performance of the catalyst and improve the stability of the catalyst under the working condition of large current for a long time.)

1. The oxygen evolution catalytic electrode protected by the weak acid salt layer is characterized by comprising an oxygen evolution catalytic electrode substrate and the weak acid salt layer on the surface of the oxygen evolution catalytic electrode substrate.

2. The weak acid salt layer protected oxygen evolution catalytic electrode of claim 1, wherein the oxygen evolution catalytic electrode substrate comprises: a carrier and a catalyst supported on the carrier;

the catalyst is selected from: one or more of metal, hydroxide, sulfide, phosphide, selenide and oxide.

3. The weak acid salt layer protected oxygen evolution catalytic electrode of claim 2, wherein the support is selected from the group consisting of: one or more of foamed nickel, foamed nickel iron, foamed cobalt, foamed iron, a nickel net, a stainless steel net, foamed titanium, a titanium net, a titanium felt, carbon paper and carbon cloth.

4. The weak acid salt layer protected oxygen evolution catalytic electrode of any of claims 1-3, the weak acid salt layer comprising: one or more of a phosphate layer, a hypophosphite layer, a carbonate layer, a tungstate layer, a molybdate layer, a borate layer, an acetate layer, a sulfite layer and a thiosulfate layer.

5. A preparation method of an oxygen evolution catalytic electrode protected by a weak acid salt layer is characterized by comprising the following steps:

dripping 0.01-2.0mol/L of weak acid salt solution on an oxygen evolution catalytic electrode substrate to deposit a weak acid salt layer on the surface of the oxygen evolution catalytic electrode substrate, and airing or heating and drying at room temperature to obtain the oxygen evolution catalytic electrode protected by the weak acid salt layer;

the surface of the oxygen evolution catalytic electrode protected by the weak acid salt layer is provided with the weak acid salt layer.

6. A preparation method of an oxygen evolution catalytic electrode protected by a weak acid salt layer is characterized by comprising the following steps:

carrying out constant current charging test on the oxygen evolution catalytic electrode substrate in a mixed solution of weak acid salt and alkali to deposit a weak acid salt layer on the surface of the oxygen evolution catalytic electrode substrate, thus obtaining the oxygen evolution catalytic electrode protected by the weak acid salt layer;

the surface of the oxygen evolution catalytic electrode protected by the weak acid salt layer is provided with the weak acid salt layer;

the constant current test is carried out, the current is 10-1000 mA, and the test time is 1 min-3 h.

7. The production method according to claim 6, wherein the oxygen evolution catalytic electrode substrate comprises a support and a carrier and a catalyst supported on the carrier;

the catalyst is selected from: one or more of metal, hydroxide, sulfide, phosphide, selenide and oxide.

The carrier is selected from: one or more of foamed nickel, foamed nickel iron, foamed cobalt, foamed iron, a nickel net, a stainless steel net, foamed titanium, a titanium net, a titanium felt, carbon paper and carbon cloth.

8. The method according to claim 6, wherein the concentration ratio of the weak acid salt to the alkali in the mixed solution of the weak acid salt and the alkali is 0.01 to 10.

9. A method for improving the stability of oxygen evolution reaction of an oxygen evolution catalytic electrode is characterized in that the oxygen evolution reaction is carried out in an electrolytic cell, a working electrode of the electrolytic cell is the oxygen evolution catalytic electrode, and an electrolyte is as follows: a mixed solution of a weak acid salt and a base.

10. Use of the weak acid salt layer protected oxygen evolution catalytic electrode of claim 1 for improving the stability of the electrode in oxygen evolution reactions in alkaline environments.

Technical Field

The invention belongs to the technical field of inorganic material synthesis and the technical field of electrochemical water electrolysis, and particularly relates to a nickel-iron hydrotalcite electrode and preparation thereof, and a method for improving the stability of oxygen evolution reaction of the nickel-iron hydrotalcite electrode.

Background

With the rapid development of economy and the increasing exhaustion of fossil energy, the energy crisis has become one of the problems to be solved urgently in the 21 st century. Among them, the electrolytic water is being researched more and more because of its clean and pollution-free product. The electrolysis water comprises two half-reactions, one being the Hydrogen Evolution Reaction (HER) and one being the Oxygen Evolution Reaction (OER). Wherein HER is a two electron reaction and OER is a four electron reaction, has a slower kinetic process, and is particularly important for the study of OER catalytic electrodes.

In past studies, nickel iron hydrotalcite possesses basic OER activity superior to other catalysts. However, in the process of electrolysis in an alkaline environment, the continuous consumption of hydroxide ions can cause local pH change on the surface of the electrode, even the local environment is acidic, and the structure of the nickel-iron hydrotalcite is damaged, so that the activity of the nickel-iron hydrotalcite is greatly reduced. Therefore, the stability of the nickel-iron hydrotalcite is improved, and the method plays an extremely important role in the development of the water electrolysis OER catalyst.

The present invention has been made to solve the above problems.

Disclosure of Invention

The invention provides an oxygen evolution catalytic electrode protected by a weak acid salt layer.

Preferably, the oxygen evolution catalytic electrode substrate comprises: a carrier and a catalyst supported on the carrier. One or more of catalyst hydroxide, sulfide or phosphide, selenide and oxide.

Preferably, the catalyst is selected from: one or more of metal, hydroxide, sulfide, phosphide, metal selenide and metal oxide;

preferably, the carrier is selected from: one or more of foamed nickel, foamed nickel iron, foamed cobalt, foamed iron, a nickel net, a stainless steel net, foamed titanium, a titanium net, a titanium felt, carbon paper and carbon cloth.

Preferably, the oxygen evolution catalytic electrode matrix comprises a foamed nickel substrate and nickel-iron hydrotalcite with a nanosheet array structure loaded on the foamed nickel substrate.

Preferably, the weak acid salt layer comprises: one or more of a phosphate layer, a hypophosphite layer, a carbonate layer, a tungstate layer, a molybdate layer, a borate layer, an acetate layer, a sulfite layer and a thiosulfate layer.

The invention provides a preparation method of an oxygen evolution catalytic electrode protected by a weak acid salt layer, which comprises the following steps:

dripping 0.01-2.0mol/L of weak acid salt solution on an oxygen evolution catalytic electrode substrate to deposit a weak acid salt layer on the surface of the oxygen evolution catalytic electrode substrate, and airing at room temperature to obtain the oxygen evolution catalytic electrode protected by the weak acid salt layer;

the surface of the oxygen evolution catalytic electrode protected by the weak acid salt layer is provided with the weak acid salt layer.

Preferably, the oxygen evolution catalytic electrode substrate comprises: a carrier and a catalyst supported on the carrier. The catalyst is selected from: one or more of metal, hydroxide, sulfide, phosphide, selenide and oxide. The carrier is selected from: one or more of foamed nickel, foamed nickel iron, foamed cobalt, foamed iron, a nickel net, a stainless steel net, foamed titanium, a titanium net, a titanium felt, carbon paper and carbon cloth.

Or the oxygen evolution catalytic electrode matrix comprises a foamed nickel substrate and nickel-iron hydrotalcite loaded on the foamed nickel substrate and having a nanosheet array structure.

Of course, any suitable catalyst carrier can be used as the carrier of the present invention, and any suitable catalyst for catalyzing the oxygen evolution reaction can be selected as the catalyst supported on the carrier.

Preferably, the oxygen evolution catalytic electrode substrate comprises: the nickel-iron hydrotalcite comprises a foamed nickel substrate and nickel-iron hydrotalcite loaded on the foamed nickel substrate and having a nanosheet array structure.

The oxygen evolving catalytic electrode substrate may be prepared according to the method of the present invention or may be prepared according to existing methods.

The third aspect of the invention provides a preparation method of an oxygen evolution catalytic electrode protected by a weak acid salt layer, which comprises the following steps:

carrying out constant current charging test on the oxygen evolution catalytic electrode substrate in a mixed solution of weak acid salt and alkali to deposit a weak acid salt layer on the surface of the oxygen evolution catalytic electrode substrate, thus obtaining the oxygen evolution catalytic electrode protected by the weak acid salt layer;

the surface of the oxygen evolution catalytic electrode protected by the weak acid salt layer is provided with the weak acid salt layer;

in the constant current test, the current is 10-1000 mA, and the test time is 10 min-3 h.

Preferably, the oxygen evolution catalytic electrode matrix comprises a foamed nickel substrate and nickel-iron hydrotalcite with a nanosheet array structure loaded on the foamed nickel substrate;

the preparation method of the oxygen evolution catalytic electrode substrate comprises the following steps:

step 1, dissolving nickel salt and ferric salt in deionized water to obtain electroplating solution of nickel salt and ferric salt;

step 2, fixing foamed nickel on a platinum sheet electrode clamp, immersing the platinum sheet electrode clamp into the electroplating solution in the step 1, and performing constant potential deposition by using a three-electrode system of an electrochemical workstation;

wherein, in the step 1, the nickel salt is one or more of nickel nitrate, nickel chloride or nickel sulfate, the ferric salt is one or more of ferric nitrate, ferric chloride or ferric sulfate, and the molar ratio of the nickel salt to the ferric salt is 1-6: 1.

in the step 2, the deposition potential of the constant potential deposition is-2-0V, the deposition time is 20-60 min, and the reaction temperature is 30-60 ℃.

Preferably, the concentration ratio of the weak acid salt to the alkali in the mixed solution of the weak acid salt and the alkali is 1: 2.

The fourth aspect of the present invention provides a method for improving the stability of the oxygen evolution reaction of an oxygen evolution catalytic electrode, wherein the oxygen evolution reaction is carried out in an electrolytic cell, the working electrode of the electrolytic cell is the oxygen evolution catalytic electrode, and the electrolyte is: a mixed solution of a weak acid salt and a base.

Preferably, in the mixed solution of the weak acid salt and the alkali, the concentration ratio of the weak acid salt to the alkali is 0.01-10.

Preferably, the weak acid salt comprises: one or more of borate, phosphate, carbonate, tungstate, molybdate and acetate.

Preferably, the oxygen evolution catalytic electrode is a nickel iron hydrotalcite electrode comprising: the nickel-iron hydrotalcite comprises a foamed nickel substrate and nickel-iron hydrotalcite loaded on the foamed nickel substrate and having a nanosheet array structure.

The alkali of the invention is one or more of potassium hydroxide, sodium hydroxide and ammonia water.

In a fifth aspect, the invention provides the use of the weak acid salt layer protected oxygen evolution catalytic electrode of the first aspect for improving the stability of the oxygen evolution reaction of the electrode in an alkaline environment.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention firstly proposes that the OER stability of the oxygen evolution catalytic electrode in an alkaline environment is improved by using weak acid salt. In the OER process, the oxygen evolution catalytic electrode can continuously consume hydroxide radicals on the surface of the electrode to generate oxygen, so that the pH value of the surface of the electrode is continuously reduced, the oxygen evolution catalytic electrode has a metal ion dissolution phenomenon, the structure of the oxygen evolution catalytic electrode is damaged, and the stability of the oxygen evolution catalytic electrode is influenced. According to the invention, a weak acid salt is used for regulating and controlling the components of the electrolyte in the constant-current charging process or the weak acid salt solution is dripped on the NiFe-LDH, so that weak acid salt ions are attached to the surface of the oxygen evolution catalytic electrode to form a weak acid salt layer. The hydrolysis action of the weak acid salt can buffer the pH change of the surface of the oxygen evolution catalytic electrode, stabilize the atoms on the surface layer of the catalyst through coordination action, inhibit the dissolution of metal ions, play a role in protecting the structure and performance of the catalyst and improve the stability of the catalyst under the large-current long-time working condition.

Particularly, when the oxygen evolution catalytic electrode is a nickel-iron hydrotalcite electrode, the surface of the nickel-iron hydrotalcite adsorbs weak acid salt ions, so that iron ions can be maintained in a lower valence state, the dissolution of the iron ions is prevented, the binding energy of iron-oxygen bonds can be improved, the iron ions are more stable, and the stability of the electrode is improved.

2. The method for improving the stability of the nickel-iron hydrotalcite electrode is simple and convenient, the reaction conditions are easy to control, the reaction process and the operation are simple, the cost is low, and the raw materials used in the method are rich in reserves and have little pollution to the environment.

Drawings

FIG. 1 is an SEM image (a) of a nickel iron hydrotalcite electrode of comparative example 1 and example 2 at 400mA cm^-2Current density of nickel iron hydrotalcite electrode SEM picture after 100h test in mixed solution of 1M KOH and 0.5M different weak acid salts. (b)1M KOH, (c)1M KOH +0.5M K₂B₄O₇、(d)1M KOH+0.5M K₃PO₄、(e)1M KOH+0.5M K₂CO₃、(f)1M KOH+0.5M Na₂WO₄、(g)1M KOH+0.5M K₂MoO₄、(h)1M KOH+0.5M CH₃COONa

FIG. 2 is a graph showing a curve at 400mA cm^-2The nickel-iron hydrotalcite electrode is tested in a mixed solution of 1M KOH and 0.5M different weak acid salts for 100 hours under the current density, and then the linear cyclic voltammetry curve comparison is carried out. (a)1M KOH, (b)1M KOH +0.5M K₂B₄O₇、(c)1M KOH+0.5M K₃PO₄、(d)1M KOH+0.5M K₂CO₃

FIG. 3 at 400mA cm^-2The nickel iron hydrotalcite electrode under the current density is tested in a mixed solution of 1M KOH and 0.5M different weak acid salts for a stability curve after 100 hours. (a)1M KOH, (b)1M KOH +0.5M K₂B₄O₇、(c)1M KOH+0.5M K₃PO₄、(d)1M KOH+0.5M K₂CO₃。

FIG. 4 is a graph showing a curve at 400mA cm^-2The nickel-iron hydrotalcite electrode is tested in a mixed solution of 1M KOH and 0.5M different weak acid salts for 100 hours under the current density, and then the linear cyclic voltammetry curve comparison is carried out. (a)1M KOH +0.5M K₂MoO₄、(b)1M KOH+0.5M CH₃COONa、(c)1M KOH+0.5M Na₂WO₄。

FIG. 5 at 400mA cm^-2The nickel iron hydrotalcite electrode under the current density is tested in a mixed solution of 1M KOH and 0.5M different weak acid salts for a stability curve after 100 hours. (a)1M KOH +0.5M Na₂WO₄、(b)1M KOH+0.5M K₂MoO₄、(c)1M KOH+0.5M CH₃COONa。

FIG. 6 shows the nickel-iron hydrotalcite electrodes treated with different weak acid salts at 400mA cm^-2At a current density of (a), linear cyclic voltammograms after 50h of testing in 1M KOH solution were compared. (a) NiFe-LDH A, (B) NiFe-LDH B, (C) NiFe-LDH C, (D) NiFe-LDH D, (E) NiFe-LDH E, (F) NiFe-LDH F

FIG. 7 is a graph showing a curve at 400mA cm^-2The stability curve of the nickel-iron hydrotalcite electrode treated by different weak acid salts in 1M KOH solution after 50 hours of test is obtained. (a) NiFe-LDH A, (B) NiFe-LDH B, (C) NiFe-LDH C, (D) NiFe-LDH D, (E) NiFe-LDH E, (F) NiFe-LDH F

FIG. 8 is a graph showing a curve at 400mA cm^-2The stability curves of the phosphate, borate, carbonate treated nickel iron sulfide electrodes tested in 1M KOH solution at current densities of (g).

FIG. 9 is a graph showing a curve at 400mA cm^-2The stability curves of phosphate, borate, carbonate treated nickel iron phosphide electrodes tested in 1M KOH solution at current densities of (g).

FIG. 10 is at 400mA cm^-2Current density of next time phosphate treated NiFe-LDH, nickel iron phosphide electrode, nickel iron sulfide stability curve tested in 1M KOH solution.

FIG. 11 is at 400mA cm^-2Sulfite treated NiFe-LDH, nickel iron phosphide electrode, nickel iron sulfide in 1M KOH solution at current density.

FIG. 12 is a graph showing the measurement at 400mA cm^-2The stability curves tested for thiosulfate-treated NiFe-LDH, nickel iron phosphide electrode, nickel iron sulfide in 1M KOH solution at current densities of (a).

FIG. 13 at 400mA cm^-2The nickel-iron hydrotalcite electrode is respectively at 1M KOH +0.5M Na under the current density₂SO₃Solution, 1M KOH +0.5M Na₂S₂O₃Solution, 1M KOH +0.5M NaH₂PO₂Stability test in solution stability curve after 100 h.

Detailed Description

The present invention is further illustrated by the following examples, but is not limited to these examples. The experimental methods not specified in the examples are generally commercially available according to the conventional conditions and the conditions described in the manual, or according to the general-purpose equipment, materials, reagents and the like used under the conditions recommended by the manufacturer, unless otherwise specified. The starting materials required in the following examples and comparative examples are all commercially available.

According to the blue battery test system, the reference electrode is a mercury oxide electrode, the counter electrode is a platinum sheet electrode, and the working electrode is the electrode in the embodiment.

Example 1

The preparation method of the electrode precursor provided by the embodiment comprises the following steps:

step 1: cleaning the foamed nickel by using ethanol and dilute hydrochloric acid to remove oil and oxides on the surface of the foamed nickel;

step 2: dissolving nickel salt and iron salt in deionized water to obtain electroplating solution of nickel salt and iron salt;

and step 3: and (3) fixing the foamed nickel in the step (1) on a platinum sheet electrode clamp, immersing the platinum sheet electrode clamp into the electroplating solution in the step (2), and performing constant potential deposition by using a three-electrode system of an electrochemical workstation to obtain an electrode precursor NiFe-LDH 1.

Wherein, the nickel salt in the step 2 is nickel nitrate; the ferric salt is ferric chloride, and the molar ratio of the nickel salt to the ferric salt is 4: 1.

the three-electrode system in the step 3 is assembled in an electrolytic cell by taking a silver-silver chloride electrode as a reference electrode, a platinum sheet electrode as a counter electrode and the working electrode as a working electrode; and 3, constant potential deposition, wherein the deposition potential is-1V, the deposition time is 60min, and the reaction temperature is 60 ℃.

Preparing an electrode precursor NiFe-LDH 2:

the nickel salt in the step 2 is nickel nitrate; the ferric salt is changed into ferric nitrate, and the molar ratio of the nickel salt to the ferric salt is 3: 1. and 3, constant potential deposition, wherein the deposition potential is-1V, the deposition time is 30min, the reaction temperature is 30 ℃, the nickel nitrate is 0.006M, the ferric nitrate is 0.018M, and the specification of the foamed nickel is 1 x 2 cm. The other methods are not changed, and an electrode precursor NiFe-LDH2 is obtained.

Example 2

And (3) borate treatment: k is prepared in 0.1mol/L₂B₄O₇And (3) dripping 1mL of solution into the electrode precursor NiFe-LDH1 of example 1, and airing at room temperature to obtain NiFe-LDH A.

And (3) phosphate treatment: k is prepared in 0.3mol/L₃PO₄And (3) dripping 1mL of solution into the electrode precursor NiFe-LDH1 of example 1, and airing at room temperature to obtain NiFe-LDH B.

Carbonate treatment: preparing K of 1.2mol/L₂CO₃And (3) dripping 1mL of solution into the electrode precursor NiFe-LDH1 of example 1, and airing at room temperature to obtain NiFe-LDH C.

Tungstate treatment: preparing 0.6mol/L of Na₂WO₄And (3) dripping 1mL of solution into the electrode precursor NiFe-LDH2 of example 1, and airing at room temperature to obtain NiFe-LDH D.

And (3) molybdate treatment: k with the configuration of 2mol/L₂MoO₄And (3) dripping 1mL of solution into the electrode precursor NiFe-LDH2 of example 1, and airing at room temperature to obtain NiFe-LDH E.

Acetate treatment: preparing CH with 1.1mol/L₃And (3) dripping 1mL of COONa solution on the electrode precursor NiFe-LDH2 of the example 1, and airing at room temperature to obtain NiFe-LDH F.

Application example 1

The nickel iron hydrotalcite electrodes A-F (NiFe-LDH A-NiFe-LDH F) of example 2 were subjected to stability test and OER performance test.

The test method is as follows:

1. a three-electrode system is built by utilizing an electrochemical workstation, a mercury oxidized mercury electrode is used as a reference electrode, a platinum sheet is used as a counter electrode, the nickel-iron hydrotalcite electrodes A, B, C, D, E, F in the embodiment 2 are respectively used as working electrodes, and an OER performance test is carried out in 1M KOH by utilizing a linear cyclic voltammetry test system.

2. By using a blue battery test system, a mercury oxidation mercury electrode is used as a reference electrode, a platinum sheet is used as a counter electrode, the nickel-iron hydrotalcite electrodes A, B, C, D, E, F in the embodiment 2 are respectively used as working electrodes, and a constant current test system is used for testing 400mA cm of mercury in a 1M KOH solution^-2The stability test was performed at the current density of (1).

3. After the stability test, a three-electrode system is set up by using an electrochemical workstation, a mercury mercuric oxide electrode is used as a reference electrode, a platinum sheet is used as a counter electrode, the nickel-iron hydrotalcite electrodes A, B, C, D, E, F in the embodiment 2 are respectively used as working electrodes, and an OER performance test is performed in 1M KOH by using a linear cyclic voltammetry test system.

The test result shows that:

the electrodes described in example 2 were obtained by treating the NiFe-LDH surface with a weak acid salt and subjected to stability testing and comparison of OER activity before and after the stability testing. The results are shown in FIGS. 6 and 7. The NiFe-LDH treated by weak acid salt is 400mA cm^-2The catalyst can continuously and stably work for 50h under the current density, and the OER catalytic activity of the catalyst is not changed before and after the stability test. Proves that the OER catalytic activity of the NiFe-LDH can be protected by the treatment method of dripping the weak acid salt on the surface of the NiFe-LDH.

Comparative example 1

This comparative example was tested for stability in a conventional alkaline environment directly using the electrode precursor NiFe-LDH2 of example 1, and included the following steps:

step 1: carrying out constant current polarization on the prepared nickel-iron hydrotalcite electrode in a 1M KOH solution by utilizing an electrochemical workstation;

step 2: carrying out linear voltammetry cycling on the electrode in the step 1 in a 1M KOH solution, and testing the OER activity of the electrode;

and step 3: subjecting the electrode of step 2 to a blue cell test system in a 1M KOH solution at 400mA cm^-2The 100h stability test was performed at current density of (1).

And 4, step 4: and (4) performing linear voltammetry cycling on the electrode in the step (3) in a 1M KOH solution, and testing the OER activity after the stability test.

SEM characterization was performed on the electrode precursor NiFe-LDH2 of example 1. FIG. 1a is an SEM image of the electrode precursor NiFe-LDH2 of example 1.

From fig. 1a, it can be seen that the hydrotalcite deposited on the surface of the foamed nickel is a nanosheet array structure, and the structure grows uniformly to cover the foamed nickel.

Fig. 1b is an SEM image of the electrode after comparative example 1, step 3, stability test. Figure 3a is a comparative example 1, step 3 stability test curve. Figure 2a is a linear cyclic voltammogram of comparative example 1, step 4.

The potential variation is around 100mV as shown by the line in fig. 3 a. From the potential change, the electrode precursor NiFe-LDH2 of example 1 was subjected to stability test in 1M KOH solution, and the performance of the electrode was reduced.

As can be seen from the linear cyclic voltammogram of fig. 2a, the electrode peak potential shifts to a larger potential direction, and the electrode performance decreases.

It can be seen from fig. 1b that the sheet structure on the surface of the electrode is destroyed, and the nanosheet array structure largely disappears, which may be the cause of the reduction of the performance of the electrode.

Example 3

The electrode precursor NiFe-LDH2 of example 1 was used directly in the invention at K₂B₄O₇And KOH, comprising the following steps:

step 1: the electrode precursor NiFe-LDH2 of example 1 is activated by constant current in 1M KOH solution by an electrochemical workstation;

step 2: carrying out linear voltammetry cycling on the electrode in the step 1 in a 1M KOH solution, and testing the OER activity of the electrode;

and step 3: and (3) stability testing: subjecting the electrode obtained in step 2 to 1M KOH +0.5M K₂B₄O₇In solution using a blue cell test system at 400mA cm^-2The current density of (2) for 100 h;

and 4, step 4: and (4) performing linear voltammetry cycling on the electrode in the step (3) in a 1M KOH solution, and testing the OER activity after the stability test.

Fig. 1c is an SEM image of the electrode after the example 3, step 3, stability test. As can be seen from FIG. 1c, the electrode surface morphology is still clear, the nanosheet structure is obvious, and the array structure is still kept as it is, so that the borate is proved to play a role in protecting the structure.

Figure 3b is the example 3 step 3 stability test curve. FIG. 2b is a linear cyclic voltammogram of step 4 of example 3.

The performance of the electrode is characterized by a stability test curve 3b and a linear cyclic voltammetry curve 2b, and the results consistently show that: the electrode after stability test in the solution added with borate has no change in voltage and no change in oxygen evolution performance. In contrast, the electrode precursor NiFe-LDH2 of example 1 in comparative example 1 was subjected to stability test in 1M KOH solution, and the electrode performance was reduced. This proves that borate has the effect of protecting the oxygen evolution performance of hydrotalcite.

Example 4

This example used the electrode precursor NiFe-LDH2 of example 1 directly at K₃PO₄And KOH, comprising the following steps:

step 1: carrying out constant current activation on the prepared nickel-iron hydrotalcite electrode in a 1M KOH solution by using an electrochemical workstation;

step 2: carrying out linear voltammetry cycling on the electrode in the step 1 in a 1M KOH solution, and testing the OER activity of the electrode;

and step 3: subjecting the electrode obtained in step 2 to 1M KOH +0.5M K₃PO₄In solution using a blue cell test system at 400mA cm^-2The 100h test was performed at the current density of (1).

And 4, step 4: and (4) performing linear voltammetry cycling on the electrode in the step (3) in a 1M KOH solution, and testing the OER activity after the stability test.

Fig. 1d is an SEM image of the electrode after the example 4, step 3, stability test.

It can be seen from fig. 1d that the electrode surface morphology is still clear, and the nanosheet array will dissolve to a lesser extent, but still maintain a relatively complete nanosheet array structure, which proves that the dissolution of the nanosheet array structure is slowed down when tested in a solution containing phosphate.

The surface of the electrode is weak acid salt ions adsorbed on the surface of the NiFe-LDH, and a weak acid salt layer is formed on the surface of the electrode.

Figure 3c is the example 4 step 3 stability test curve. FIG. 2c is a linear cyclic voltammogram of step 4 of example 4.

The results in fig. 3c and fig. 2c are consistent showing that there is no change in voltage and no change in oxygen evolution performance after stability testing in a solution with added phosphate compared to the electrodes tested in 1M KOH. The phosphate is proved to have the function of protecting the oxygen evolution performance of the hydrotalcite.

Example 5

This example used the electrode precursor NiFe-LDH2 of example 1 directly at K₂CO₃And KOH, comprising the following steps:

step 1: carrying out constant current activation on the prepared nickel-iron hydrotalcite electrode in a 1M KOH solution by using an electrochemical workstation;

step 2: carrying out linear voltammetry cycling on the electrode in the step 1 in a 1M KOH solution, and testing the OER activity of the electrode;

and step 3: subjecting the electrode obtained in step 2 to 1M KOH +0.5M K₂CO₃In solution using a blue cell test system at 400mA cm^-2The 100h stability test was performed at current density of (1).

And 4, step 4: and (4) performing linear voltammetry cycling on the electrode in the step (3) in a 1M KOH solution, and testing the OER activity after the stability test.

Fig. 1e is an SEM image of the electrode after the stability test of example 5, step 3.

It can be seen from fig. 1e that the electrode surface morphology is still clear, the nanosheet structure is obvious, and the array structure is still kept as it is, which proves that the carbonate has a protective effect on the nickel-iron hydrotalcite structure.

FIG. 3d is a stability test curve of example 5, step 3. FIG. 2d is a linear cyclic voltammogram of example 5, step 4.

The results in fig. 3d and fig. 2d are consistent showing that the voltage is unchanged and the oxygen evolution performance is unchanged after stability testing in the solution with added carbonate compared to the electrodes tested in 1M KOH. Proves that the carbonate has the function of protecting the oxygen evolution performance of the hydrotalcite.

Example 6

In this example, the electrode precursor NiFe-LDH2 of example 1 was used directly in Na₂WO₄And KOH, comprising the following steps:

step 1: activating the prepared nickel-iron hydrotalcite electrode in a 1M KOH solution for a period of time by utilizing a constant current test on an electrochemical workstation;

step 2: carrying out linear voltammetry cycling on the electrode in the step 1 in a 1M KOH solution, and testing the OER activity of the electrode;

and step 3: subjecting the electrode obtained in step 2 to 1M KOH +0.5M Na₂WO₄In solution using a blue cell test system at 400mA cm^-2The 100h test was performed at the current density of (1).

And 4, step 4: and (4) performing linear voltammetry cycling on the electrode in the step (3) in a 1M KOH solution, and testing the OER activity after the stability test.

Fig. 1f is an SEM image of the electrode after the example 6, step 3, stability test.

It can be seen from fig. 1f that the electrode surface morphology is still clear, the nanosheet structure is obvious, the nano-array structure is still maintained, but the nanosheet is thickened, which proves that the phenomenon of thickening of the nanosheet can occur under the protection effect of tungstate on the nickel iron hydrotalcite nano-array structure.

FIG. 5a is a stability test curve of example 6, step 3. FIG. 4c is a linear cyclic voltammogram of step 4 of example 6.

The results of fig. 5a and fig. 4c are consistent, and show that after stability test, the voltage rises by about 90mV and the oxygen evolution performance is reduced to a small extent in the solution added with tungstate. Compared with electrodes tested in 1M KOH, tungstate has the effect of delaying the oxygen evolution performance of hydrotalcite.

Example 7

In this example, the electrode precursor NiFe-LDH1 of example 1 was used directly in Na₂MoO₄And KOH, comprising the following steps:

step 1: activating the prepared nickel-iron hydrotalcite electrode in a 1M KOH solution for a period of time by utilizing a constant current test on an electrochemical workstation;

step 2: carrying out linear voltammetry cycling on the electrode in the step 1 in a 1M KOH solution, and testing the OER activity of the electrode;

and step 3: subjecting the electrode obtained in step 2 to 1M KOH +0.5M Na₂MoO₄In solution (A) using a blue cell test system at 400mA cm^-2The 100h test was performed at the current density of (1).

And 4, step 4: and (4) performing linear voltammetry cycling on the electrode in the step (3) in a 1M KOH solution, and testing the OER activity after the stability test.

Fig. 1g is an SEM image of the electrode after the example 7, step 3, stability test.

It can be seen from fig. 1g that the electrode surface morphology is still clear, the nanosheet structure is obvious, and the array structure is still kept as it is, which proves that molybdate has a protective effect on the nickel-iron water structure.

FIG. 5b is a stability test curve of example 7, step 3. FIG. 4a is a linear cyclic voltammogram of step 4 of example 7.

The performance of the electrode is characterized by a stability test curve 5b and a linear cyclic voltammetry curve 4a, and the results are consistent, which shows that compared with the electrode tested in 1M KOH, after stability test in solution added with molybdate, the voltage is not changed, and the oxygen evolution performance is not changed. The molybdate is proved to have the function of protecting the oxygen evolution performance of the hydrotalcite.

Example 8

This example used the electrode precursor NiFe-LDH1 of example 1 directly in CH₃The stability test is carried out in a mixed solution of COONa and KOH, and comprises the following steps:

step 1: activating the prepared nickel-iron hydrotalcite electrode in a 1M KOH solution for a period of time by utilizing a constant current test on an electrochemical workstation;

step 2: carrying out linear voltammetry cycling on the electrode in the step 1 in a 1M KOH solution, and testing the OER activity of the electrode;

and step 3: subjecting the electrode obtained in step 2 to 1M KOH +0.5M CH₃Test system in COONa solution at 400mA cm by blue battery^-2The 100h test was performed at the current density of (1).

And 4, step 4: and (4) performing linear voltammetry cycling on the electrode in the step (3) in a 1M KOH solution, and testing the OER activity after the stability test.

Fig. 1h is an SEM image of the electrode after the example 7, step 3, stability test.

It can be seen from fig. 1h that the electrode surface morphology is still clear, and the nanosheet array structure remains the original shape, which proves the protective effect of acetate on the nickel-iron hydrotalcite nano array structure.

FIG. 5c is a stability test curve for example 8, step 3. FIG. 4b is a linear cyclic voltammogram of step 4 of example 8.

The performance of the electrode is characterized by a stability test curve 5c and a linear cyclic voltammetry curve 4b, and the results are consistent, so that compared with the electrode tested in 1M KOH, the voltage is unchanged and the oxygen evolution performance is unchanged after the stability test in the solution added with acetate. Proves that the acetate has the function of protecting the oxygen evolution performance of the hydrotalcite.

Example 9

The nickel iron sulfide electrode of this example was prepared using the following method,

the electrode precursor NiFe-LDH1 of example 1 was sulfided by vapor deposition, first weighing 100mg of sulfur powder and placing it in a clean porcelain boat and in the upper tuyere of a tube furnace. And placing the electrode precursor frame on another clean porcelain boat, and placing the electrode precursor frame at a lower air port of the tube furnace. And the hose at the air outlet end is connected into a gas washing bottle filled with saturated copper sulfate and then is connected into the gas washing bottle filled with water. And introducing high-purity argon for 20min to perform air exhaust operation in the furnace tube. Subsequently, the gas flow controller was adjusted to maintain the argon flow at 80ml/min, and after the flow stabilized, heating was started. Heating to 400 deg.C (heating rate of 5 deg.C/min), keeping the temperature for 2h, and naturally cooling to room temperature. The electrode precursor NiFe-LDH1 electrode of example 1 was used for phosphating,

the electrode precursor NiFe-LDH1 of example 1 was phosphated by vapor deposition by weighing 50mg of sodium hypophosphite and placing it in a clean porcelain boat and a tube furnace tuyere. And placing the electrode precursor frame on another clean porcelain boat, and placing the electrode precursor frame at a lower air port of the tube furnace. And the hose at the air outlet end is connected into a gas washing bottle filled with saturated copper sulfate and then is connected into the gas washing bottle filled with water. And introducing high-purity argon for 20min to perform air exhaust operation in the furnace tube. Subsequently, the gas flow controller was adjusted to maintain the argon flow at 80ml/min, and after the flow stabilized, heating was started. Heating to 400 deg.C (heating rate of 5 deg.C/min), keeping the temperature for 2h, and naturally cooling to room temperature.

1) And (3) phosphate treatment:

the present example was subjected to a stability test in a 1M KOH solution using nickel iron sulfide and nickel iron phosphide electrodes directly after phosphating (phosphating employed the method of carbonate treatment of example 2, replacing only the electrodes of example 1 with nickel iron sulfide and nickel iron phosphide electrodes), comprising the steps of:

step 1: activating the phosphated nickel-iron sulfide and nickel-iron phosphide electrodes in a 1M KOH solution for a period of time by using a constant current test on an electrochemical workstation;

step 2: the electrode described in step 1 was tested in a 1M KOH solution at 400mA cm using a blue cell test system^-2The test was carried out for 25h at the current density of (1).

2) And (3) borate treatment:

this example was conducted in a 1M KOH solution stability test using treated nickel iron sulfide and nickel iron phosphide electrodes directly using borate (borate treatment used the method of borate treatment of example 2, only the electrodes of example 1 were replaced with nickel iron sulfide and nickel iron phosphide electrodes) including the following steps:

step 1: activating the borate-treated nickel-iron sulfide and nickel-iron phosphide electrodes in a 1M KOH solution for a period of time by using a constant current test on an electrochemical workstation;

step 2: the electrode described in step 1 was tested in a 1M KOH solution at 400mA cm using a blue cell test system^-2The test was carried out for 25h at the current density of (1).

3) Carbonate treatment:

this example directly used the carbonated treated nickel iron sulfide and nickel iron phosphide electrodes (the carbonation treatment used the method of example 2 carbonate treatment, replacing only the electrode of example 1 with the nickel iron sulfide and nickel iron phosphide electrodes) in a 1M KOH solution for stability testing, comprising the following steps:

step 1: activating the carbonate treated nickel-iron sulfide and nickel-iron phosphide electrodes in a 1M KOH solution for a period of time by using a constant current test on an electrochemical workstation;

step 2: the electrode described in step 1 was tested in a 1M KOH solution at 400mA cm using a blue cell test system^-2The test was carried out for 25h at the current density of (1).

Fig. 8 and 9 are stability test curves of example 9, step 2. The performance of the electrode is characterized by stability test graphs 8 and 9, and the results are consistent to show that compared with the electrode tested in 1M KOH, the oxygen evolution performance of the electrode is not changed after the electrode of nickel sulfide and nickel phosphide which are treated by phosphate, borate and carbonate is subjected to stability test in a solution of 1M KOH. The method of demonstrating weak acid salt layer is equally applicable to sulfide and phosphide electrodes.

Example 10

This example was tested for stability in a 1M KOH solution using the electrode precursor NiFe-LDH1 directly after hypophosphite treatment (hypophosphite treatment used the molybdate treatment of example 2), the nickel iron sulfide of example 9, and the nickel iron phosphide of example 9, including the following steps:

step 1: activating the prepared electrode in a 1M KOH solution for a period of time on an electrochemical workstation by using a constant current test;

step 2: carrying out linear voltammetry cycling on the electrode in the step 1 in a 1M KOH solution, and testing the OER activity of the electrode;

and step 3: the electrode described in step 2 was tested in a 1M KOH solution at 400mA cm using a blue cell test system^-2The 100h test was performed at the current density of (1).

And 4, step 4: and (4) performing linear voltammetry cycling on the electrode in the step (3) in a 1M KOH solution, and testing the OER activity after the stability test.

The performance of the electrode is characterized by a stability test curve diagram 10, and the results are consistent, so that compared with the electrode tested in 1M KOH, the stability test of the electrode of NiFe-LDH, nickel-iron sulfide and nickel-iron phosphide after hypophosphite treatment shows that the voltage is not changed, and the oxygen evolution performance is not changed. Proves that the hypophosphite has the function of protecting the oxygen evolution performance of the oxygen evolution electrode.

Example 11

The present example performed stability tests using the electrode precursors NiFe-LDH1 directly after sulfite treatment (sulfite treatment used the method of tungstate treatment of example 2), nickel iron sulfide of example 9, nickel iron phosphide of example 9 in a solution of 1M KOH, including the following steps:

step 1: activating the prepared electrode in a 1M KOH solution for a period of time on an electrochemical workstation by using a constant current test;

step 2: carrying out linear voltammetry cycling on the electrode in the step 1 in a 1M KOH solution, and testing the OER activity of the electrode;

and step 3: the electrode described in step 2 was tested in a 1M KOH solution at 400mA cm using a blue cell test system^-2The 100h test was performed at the current density of (1).

And 4, step 4: and (4) performing linear voltammetry cycling on the electrode in the step (3) in a 1M KOH solution, and testing the OER activity after the stability test.

The performance of the electrode is characterized by a stability test curve diagram 11, and the results are consistent to show that compared with the electrode tested in 1M KOH, the NiFe-LDH, nickel-iron sulfide and nickel-iron phosphide electrodes treated by sulfite have no change in voltage and no change in oxygen evolution performance after stability test. Proves that the sulfite has the function of protecting the oxygen evolution performance of the oxygen evolution electrode.

Example 12

The present example carried out a stability test in a 1M KOH solution using the electrode precursors NiFe-LDH1, nickel iron sulfide, nickel iron phosphide directly after thiosulfate treatment (sulfite treatment using the carbonate treatment method of example 2), comprising the following steps:

step 1: activating the prepared electrode in a 1M KOH solution for a period of time on an electrochemical workstation by using a constant current test;

step 2: carrying out linear voltammetry cycling on the electrode in the step 1 in a 1M KOH solution, and testing the OER activity of the electrode;

and step 3: the electrode described in step 2 was tested in a 1M KOH solution at 400mA cm using a blue cell test system^-2The 100h test was performed at the current density of (1).

And 4, step 4: and (4) performing linear voltammetry cycling on the electrode in the step (3) in a 1M KOH solution, and testing the OER activity after the stability test.

The performance of the electrode is characterized by a stability test curve graph 12, and the results are consistent to show that compared with the electrode tested in 1M KOH, the NiFe-LDH, nickel sulfide iron and nickel phosphide iron electrode treated by thiosulfate has no change in voltage and no change in oxygen evolution performance after stability test. Proves that the thiosulfate has the function of protecting the oxygen evolution performance of the oxygen evolution electrode.

Example 13

In the present example, the electrode precursors NiFe-LDH1 of example 1 were used directly in Na respectively₂SO₃Mixed solution of KOH and Na₂S₂O₃Mixed solution of KOH and NaH₂PO₂And KOH, comprising the following steps:

step 1: activating the prepared nickel-iron hydrotalcite electrode in a 1M KOH solution for a period of time by utilizing a constant current test on an electrochemical workstation;

step 2: carrying out linear voltammetry cycling on the electrode in the step 1 in a 1M KOH solution, and testing the OER activity of the electrode;

and step 3: will be provided withThe electrodes in step 2 are respectively added with 1M KOH +0.5M Na₂SO₃Solution, 1M KOH +0.5M Na₂S₂O₃Solution, 1M KOH +0.5M NaH₂PO₂In solution using a blue cell test system at 400mA cm^-2The 100h test was performed at the current density of (1).

And 4, step 4: and (4) performing linear voltammetry cycling on the electrode in the step (3) in a 1M KOH solution, and testing the OER activity after the stability test.

The performance was characterized by the stability test plot 13, which consistently indicated that the electrodes tested in 1M KOH were in Na₂SO₃Mixed solution of KOH and Na₂S₂O₃Mixed solution of KOH and NaH₂PO₂After stability test, the voltage of the solution of the mixed solution of KOH and KOH is not changed, and the oxygen evolution performance is not changed. Proves that the sulfite, thiosulfate and hypophosphite have the function of protecting the oxygen evolution performance of the hydrotalcite.