CN114959767B - Nickel-based active cathode and preparation method thereof - Google Patents

Nickel-based active cathode and preparation method thereof Download PDF

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CN114959767B
CN114959767B CN202110218710.1A CN202110218710A CN114959767B CN 114959767 B CN114959767 B CN 114959767B CN 202110218710 A CN202110218710 A CN 202110218710A CN 114959767 B CN114959767 B CN 114959767B
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conductive substrate
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noble metal
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CN114959767A (en
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于昕
李爽
陆崖青
王小磊
高珊
沈妮
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Bluestar Beijing Chemical Machinery Co Ltd
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Abstract

The nickel-based active cathode comprises a conductive matrix of a nickel base material, wherein the conductive matrix is made of a nickel wire mesh, the outer surface of the conductive matrix is coated with a metal oxide catalyst intermediate layer, and the outer surface of the metal oxide catalyst intermediate layer is coated with a metal monoatomic catalyst surface layer; the metal oxide catalyst intermediate layer is composed of an oxide of a noble metal element and an oxide of a lanthanoid element, wherein the mole percentage of the noble metal element is 75% -85% and the mole percentage of the lanthanoid element is 15% -25% in the metal oxide coating layer according to the metal composition; the metal monoatomic catalyst surface layer is composed of a noble metal element. The nickel-based active cathode and the preparation method thereof have the advantages of simple process, easy operation and low preparation cost, can effectively absorb reverse current, inhibit cathode degradation caused by the reverse current when electrolysis is stopped, and inhibit damage to a cathode surface net caused by the reverse current, thereby reducing electric energy consumption.

Description

Nickel-based active cathode and preparation method thereof
Technical Field
The invention relates to the field of sodium hydroxide preparation, in particular to a nickel-based active cathode and a preparation method thereof.
Background
In the ionic membrane process caustic soda electrolysis production apparatus, when the production is stopped, free chlorine existing in the solution in the electrolytic cell is discharged on the electrode and forms a current loop due to the primary cell effect, and a reverse current is inevitably generated in the electrolytic cell.
Reverse current generation mechanism:
in the process of electrolysis, the unit cell is polarized from an equilibrium state, and the following electrolytic reactions respectively occur at the anode and the cathode:
anode: 2Cl - －2e-＝Cl 2
And (3) cathode: 2H (H) 2 O+2e-＝H 2 +2OH-
When the current is cut off, the cell returns to the equilibrium state, but the composition of the anode and cathode solution changes, and the anode solution contains (Cl - /Cl 2 ) The pair of electrodes is present in the catholyte (H 2 +OH - /H 2 O) couple and the conductive liquid is arranged in the inlet and outlet pipelines of the anode and the cathode, thus forming a primary cell, and the following primary cell reaction occurs:
anode: cl 2 +2e-＝2Cl -
And (3) cathode: h 2 +2OH - －2e-＝2H 2 O
Thereby forming a reverse current.
Hazard of reverse current:
due to H 2 The solubility in catholyte was very low (H in 21% NaOH) 2 Is about 2mL/m 3 ＝0.1mol/m 3 ) While Cl 2 Has a large solubility in the anolyte (about 1 g/l=14 mol/m 3 In the actual electrolysis process, the available chlorine in the anode liquid is about 1.5-2.0 g/L), so that H in the cathode liquid 2 Insufficient to complete the above primary cell reaction, cl 2 There is a significant driving force at the anode, causing the cathode itself in the cathode chamber to be oxidized by the reverse current.
The technology for preparing alkali by using the ionic membrane electrolysis method is widely accepted as the most advanced technology and the most reasonable economical alkali preparation method because of the advantages of energy conservation, high product quality, no pollution and the like. In recent years, the ion membrane method electrolysis technology is continuously innovated, and the main aim is to reduce direct current consumption, and particularly, after the membrane electrode distance is operated in an electrolytic tank, the electricity-saving effect is very obvious. However, due to different running conditions of the electrolytic cell, frequent stopping is mainly caused in the starting process, so that great difference exists in service life of the electrolytic cell of a user. When the electrolytic cell stops electrolyzing, the anode has (Cl-/Cl 2) pair, and the cathode has (H2+OH-/H2O) pair. After the electrolytic bath is stopped and the electrolysis is stopped, chlorine atoms in the anode liquid can be reduced into chloride ions to generate reduction reaction, and the cathode can perform oxidation reaction of metal. With the development of large-scale electrolytic cells, the additive effect of reverse current is more obvious, and the elimination and control of the reverse current are important conditions for long-period and low-energy-consumption stable operation of the electrolytic cells, so that the stress-resistance reverse current capability of the electrode is improved, and the method has positive significance for reducing the operation cost and increasing the market competitiveness.
Disclosure of Invention
The invention aims to provide the nickel-based active cathode which has simple process, easy operation and low manufacturing cost, can reduce the hydrogen evolution potential of the cathode, can effectively resist reverse current, inhibit the damage of the reverse current to a cathode surface net and reduce the electric energy consumption, and the preparation method thereof.
The nickel-based active cathode comprises a conductive matrix of a nickel base material, wherein the conductive matrix is made of a nickel screen, the outer surface of the conductive matrix of the nickel base material is coated with a metal oxide catalyst intermediate layer, and the outer surface of the metal oxide catalyst intermediate layer is coated with a metal monoatomic catalyst surface layer;
the metal oxide catalyst intermediate layer is composed of an oxide of a noble metal element and an oxide of a lanthanide, the thickness of the metal oxide catalyst intermediate layer is 6-15 mu m, and the metal oxide coating comprises 75-85% of the noble metal element and 15-25% of the lanthanide by mole percent;
the metal monoatomic catalyst surface layer is composed of noble metal elements, and the thickness of the metal monoatomic catalyst surface layer is 1-4 mu m;
the nickel-based active cathode is prepared by the following steps:
A. Preparing a conductive matrix of a nickel substrate by using a nickel screen, cleaning the conductive matrix, removing surface dirt of the conductive matrix, and roughening the surface of the conductive matrix;
B. preparing soluble nitrate of lanthanide and soluble nitrate of noble metal element, respectively dissolving the soluble nitrate of lanthanide and soluble nitrate of noble metal element in water to obtain soluble nitrate solution of lanthanide and soluble nitrate solution of noble metal element for use;
C. mixing the soluble nitrate solution of the lanthanide obtained in the step B and the noble metal nitrate solution according to the proportion that the mole percentage of noble metal elements is 75% -85%, and the mole percentage of the lanthanide is 15% -25%, wherein the concentration of the noble metal in the mixed solution is 100-120 g/L, so as to obtain a mixed solution;
D. b, regulating and controlling the concentration of noble metal in the noble metal nitrate solution prepared in the step B to 50-80 g/L to obtain a noble metal nitrate coating solution;
E. coating the mixed solution obtained in the step C on the conductive substrate treated in the step A, and heating the conductive substrate to 100-300 ℃ in air atmosphere for 10-50 minutes to obtain a first heat treatment conductive substrate;
Then heating the first heat-treated conductive substrate to 400-600 ℃ for 10-50 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
F. repeating the step E until the thickness of the metal oxide catalyst intermediate layer on the surface of the conductive substrate is 6-15 mu m;
G. coating the noble metal nitrate coating solution obtained in the step D on the conductive substrate treated in the step F, and heating the conductive substrate to 100-200 ℃ in an inert gas atmosphere for 10-30 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 350-550 ℃ for 10-30 minutes to obtain a conductive substrate with the outer surface of the metal oxide catalyst intermediate layer coated with the metal monoatomic catalyst surface layer;
H. and (C) repeating the step G until the thickness of the metal monoatomic catalyst surface layer on the surface of the conductive substrate is 1-4 mu m, namely the nickel-based active cathode.
The noble metal element is ruthenium, rhodium, palladium, osmium, iridium, platinum, gold, or silver, and the lanthanide element is lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium.
Preferably, the noble metal nitrate comprises ruthenium nitrate, palladium nitrate, iridium nitrate, platinum nitrate and silver nitrate, and the metal oxide coating comprises 78-82 mol% of noble metal elements and 18-22 mol% of lanthanoids according to metal components;
the mole percentage of noble metal element in the surface layer of the metal monoatomic catalyst is 78% -82%, and the mole percentage of lanthanide is 18% -22%.
Preferably, the metal oxide coating comprises 80 mole percent of noble metal elements and 20 mole percent of lanthanoids, based on the metal component;
the molar percentage of noble metal element in the metal monoatomic catalyst surface layer is 80% and the molar percentage of lanthanide is 20%.
Preferably, in the step E, the mixed solution obtained in the step C is coated on the conductive substrate treated in the step A, and the conductive substrate is heated to 150-250 ℃ in air atmosphere for 20-40 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 450-550 ℃ for 20-40 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
In the step G, the noble metal nitrate coating solution obtained in the step D is coated on the conductive substrate treated in the step F, and the conductive substrate is heated to 120-180 ℃ in the inert gas atmosphere for 15-25 minutes to obtain a first heat treatment conductive substrate;
and then heating the first heat-treated conductive substrate to 400-500 ℃ for 15-25 minutes to obtain the conductive substrate with the metal monoatomic catalyst surface layer coated on the outer surface of the metal oxide catalyst intermediate layer.
The preparation method of the nickel-based active cathode comprises the following steps:
A. preparing a conductive matrix of a nickel substrate by using a nickel screen, cleaning the conductive matrix, removing surface dirt of the conductive matrix, and roughening the surface of the conductive matrix;
B. preparing soluble nitrate of lanthanide and soluble nitrate of noble metal element, respectively dissolving the soluble nitrate of lanthanide and soluble nitrate of noble metal element in water to obtain soluble nitrate solution of lanthanide and soluble nitrate solution of noble metal element for use;
C. mixing the soluble nitrate solution of the lanthanide obtained in the step B and the noble metal nitrate solution according to the proportion that the mole percentage of noble metal elements is 75% -85%, and the mole percentage of the lanthanide is 15% -25%, wherein the concentration of the noble metal in the mixed solution is 100-120 g/L, so as to obtain a mixed solution;
D. B, regulating and controlling the concentration of noble metal in the noble metal nitrate solution prepared in the step B to 50-80 g/L to obtain a noble metal nitrate coating solution;
E. coating the mixed solution obtained in the step C on the conductive substrate treated in the step A, and heating the conductive substrate to 100-300 ℃ in air atmosphere for 10-50 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 400-600 ℃ for 10-50 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
F. repeating the step E until the thickness of the metal oxide catalyst intermediate layer on the surface of the conductive substrate is 6-15 mu m;
G. coating the noble metal nitrate coating solution obtained in the step D on the conductive substrate treated in the step F, and heating the conductive substrate to 100-200 ℃ in an inert gas atmosphere for 10-30 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 350-550 ℃ for 10-30 minutes to obtain a conductive substrate with the outer surface of the metal oxide catalyst intermediate layer coated with the metal monoatomic catalyst surface layer;
H. And (C) repeating the step G until the thickness of the metal monoatomic catalyst surface layer on the surface of the conductive substrate is 1-4 mu m, namely the nickel-based active cathode.
Preferably, the noble metal nitrate includes ruthenium nitrate, palladium nitrate, iridium nitrate, platinum nitrate, and silver nitrate.
Preferably, the metal oxide coating comprises 78-82 mol% of noble metal element and 18-22 mol% of lanthanide element;
the mole percentage of noble metal element in the surface layer of the metal monoatomic catalyst is 78% -82%, and the mole percentage of lanthanide is 18% -22%.
Preferably, the metal oxide coating comprises 80 mole percent of noble metal elements and 20 mole percent of lanthanoids, based on the metal component;
the molar percentage of noble metal element in the metal monoatomic catalyst surface layer is 80% and the molar percentage of lanthanide is 20%.
Preferably, in the step E, the mixed solution obtained in the step C is coated on the conductive substrate treated in the step A, and the conductive substrate is heated to 150-250 ℃ in air atmosphere for 20-40 minutes to obtain a first heat treatment conductive substrate;
Then heating the first heat-treated conductive substrate to 450-550 ℃ for 20-40 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
in the step G, the noble metal nitrate coating solution obtained in the step D is coated on the conductive substrate treated in the step F, and the conductive substrate is heated to 120-180 ℃ in the inert gas atmosphere for 15-25 minutes to obtain a first heat treatment conductive substrate;
and then heating the first heat-treated conductive substrate to 400-500 ℃ for 15-25 minutes to obtain the conductive substrate with the metal monoatomic catalyst surface layer coated on the outer surface of the metal oxide catalyst intermediate layer.
Preferably, in the step E, the mixed solution obtained in the step C is coated on the conductive substrate treated in the step A, and the conductive substrate is heated to 180-220 ℃ in air atmosphere for 25-35 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 480-520 ℃ for 25-35 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
In the step G, the noble metal nitrate coating solution obtained in the step D is coated on the conductive substrate treated in the step F, and the conductive substrate is heated to 140-160 ℃ in the inert gas atmosphere for 18-22 minutes to obtain a first heat treatment conductive substrate;
and then heating the first heat-treated conductive substrate to 430-470 ℃ for 18-22 minutes to obtain the conductive substrate with the metal monoatomic catalyst surface layer coated on the outer surface of the metal oxide catalyst intermediate layer.
The nickel-based active cathode is characterized in that a conductive matrix is made of a nickel wire mesh, a metal oxide catalyst middle layer is coated on the outer surface of the conductive matrix of a nickel base material, and a metal monoatomic catalyst surface layer is coated on the outer surface of the metal oxide catalyst middle layer. Therefore, the nickel-based active cathode and the preparation method thereof have the characteristics of simple process, easy operation, low manufacturing cost, effective resistance and absorption of reverse current, inhibition of cathode degradation caused by the reverse current when electrolysis is stopped, inhibition of damage to a cathode surface net caused by the reverse current and increase of cell pressure, and reduction of electric energy consumption.
Other details and features of the nickel-based active cathode and method of making the same of the present invention will become apparent upon review of the examples described in detail below.
Drawings
FIG. 1a is a surface topography of a nickel-based active cathode prepared in comparative example 1 of the present invention;
FIG. 1b is a surface topography of a nickel-based active cathode prepared in example 1 of the present invention;
FIG. 2a is a cross-sectional morphology of a nickel-based active cathode prepared according to comparative example 2 of the present invention;
FIG. 2b is a cross-sectional view of the nickel-based active cathode prepared in example 2 of the present invention;
FIG. 3 shows 3 examples of the invention and 4 comparative examples of the invention at 4kA/m 2 A comparison plot of hydrogen evolution potential at current density;
FIG. 4 is a graph showing the residual amount of Ru coating after multiple reverse electrification of the nickel-based active cathodes prepared according to 3 examples of the present invention and 3 comparative examples of the present invention;
FIG. 5 is a graph showing the residual amount of coating Pt after multiple reverse electrification of the nickel-based active cathodes prepared in 3 examples of the present invention and 3 comparative examples of the present invention.
Detailed Description
The nickel-based active cathode comprises a conductive matrix of a nickel base material, wherein the conductive matrix is made of a nickel screen, the outer surface of the conductive matrix of the nickel base material is coated with a metal oxide catalyst intermediate layer, and the outer surface of the metal oxide catalyst intermediate layer is coated with a metal monoatomic catalyst surface layer;
The metal oxide catalyst intermediate layer is composed of an oxide of a noble metal element and an oxide of a lanthanide, the thickness of the metal oxide catalyst intermediate layer is 6-15 mu m, and the metal oxide coating comprises 75-85% of the noble metal element and 15-25% of the lanthanide by mole percent;
the metal monoatomic catalyst surface layer is composed of noble metal elements, and the thickness of the metal monoatomic catalyst surface layer is 1-4 mu m;
the nickel-based active cathode is prepared by the following steps:
A. preparing a conductive matrix of a nickel substrate by using a nickel screen, cleaning the conductive matrix, removing surface dirt of the conductive matrix, and roughening the surface of the conductive matrix;
B. preparing soluble nitrate of lanthanide and soluble nitrate of noble metal element, respectively dissolving the soluble nitrate of lanthanide and soluble nitrate of noble metal element in water to obtain soluble nitrate solution of lanthanide and soluble nitrate solution of noble metal element for use;
C. mixing the soluble nitrate solution of the lanthanide obtained in the step B and the noble metal nitrate solution according to the proportion that the mole percentage of noble metal elements is 75% -85%, and the mole percentage of the lanthanide is 15% -25%, wherein the concentration of the noble metal in the mixed solution is 100-120 g/L, so as to obtain a mixed solution;
D. B, regulating and controlling the concentration of noble metal in the noble metal nitrate solution prepared in the step B to 50-80 g/L to obtain a noble metal nitrate coating solution;
E. coating the mixed solution obtained in the step C on the conductive substrate treated in the step A, and heating the conductive substrate to 100-300 ℃ in air atmosphere for 10-50 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 400-600 ℃ for 10-50 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
F. repeating the step E until the thickness of the metal oxide catalyst intermediate layer on the surface of the conductive substrate is 6-15 mu m;
G. coating the noble metal nitrate coating solution obtained in the step D on the conductive substrate treated in the step F, and heating the conductive substrate to 100-200 ℃ in an inert gas atmosphere for 10-30 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 350-550 ℃ for 10-30 minutes to obtain a conductive substrate with the outer surface of the metal oxide catalyst intermediate layer coated with the metal monoatomic catalyst surface layer;
H. And (C) repeating the step G until the thickness of the metal monoatomic catalyst surface layer on the surface of the conductive substrate is 1-4 mu m, namely the nickel-based active cathode.
The noble metal element is ruthenium, rhodium, palladium, osmium, iridium, platinum, gold, or silver, and the lanthanide element is lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium.
As a further improvement of the present invention, the above noble metal nitrate includes ruthenium nitrate, palladium nitrate, iridium nitrate, platinum nitrate and silver nitrate, and the metal oxide coating layer comprises 78% -82% by mole of noble metal element and 18% -22% by mole of lanthanoid element, based on metal components;
the mole percentage of noble metal element in the surface layer of the metal monoatomic catalyst is 78% -82%, and the mole percentage of lanthanide is 18% -22%.
As a further improvement of the present invention, the metal oxide coating layer described above has a noble metal element content of 80% by mole and a lanthanoid element content of 20% by mole, based on the metal component;
the molar percentage of noble metal element in the metal monoatomic catalyst surface layer is 80% and the molar percentage of lanthanide is 20%.
As a further improvement of the invention, in the step E, the mixed solution obtained in the step C is coated on the conductive substrate treated in the step A, and the conductive substrate is heated to 150-250 ℃ in air atmosphere for 20-40 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 450-550 ℃ for 20-40 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
in the step G, the noble metal nitrate coating solution obtained in the step D is coated on the conductive substrate treated in the step F, and the conductive substrate is heated to 120-180 ℃ in the inert gas atmosphere for 15-25 minutes to obtain a first heat treatment conductive substrate;
and then heating the first heat-treated conductive substrate to 400-500 ℃ for 15-25 minutes to obtain the conductive substrate with the metal monoatomic catalyst surface layer coated on the outer surface of the metal oxide catalyst intermediate layer.
The preparation method of the nickel-based active cathode comprises the following steps:
A. Preparing a conductive matrix of a nickel substrate by using a nickel screen, cleaning the conductive matrix, removing surface dirt of the conductive matrix, and roughening the surface of the conductive matrix;
the conductive matrix of the nickel-based active cathode adopts a woven nickel wire mesh, and the nickel wire mesh needs to be pretreated such as sanding, ultrasonic cleaning, drying and the like in the use process. The sanding is to enhance the roughness of the surface of the conductive substrate, so that the active catalyst layer obtains enough adhesion and enhances the stability. The ultrasonic cleaning is used for removing sand left after sanding the surface of the nickel screen, and compared with the traditional pickling technology, the ultrasonic cleaning can remove the sand on the surface of the nickel screen more environmentally-friendly, and meanwhile, the roughness of the surface of the conductive substrate is not damaged.
B. Preparing soluble nitrate of lanthanide and soluble nitrate of noble metal element, respectively dissolving the soluble nitrate of lanthanide and soluble nitrate of noble metal element in water to obtain soluble nitrate solution of lanthanide and soluble nitrate solution of noble metal element for use;
C. mixing the soluble nitrate solution of the lanthanide obtained in the step B and the noble metal nitrate solution according to the proportion that the mole percentage of noble metal elements is 75% -85%, and the mole percentage of the lanthanide is 15% -25%, wherein the concentration of the noble metal in the mixed solution is 100-120 g/L, so as to obtain a mixed solution;
D. B, regulating and controlling the concentration of noble metal in the noble metal nitrate solution prepared in the step B to 50-80 g/L to obtain a noble metal nitrate coating solution;
E. coating the mixed solution obtained in the step C on the conductive substrate treated in the step A, and heating the conductive substrate to 100-300 ℃ in air atmosphere for 10-50 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 400-600 ℃ for 10-50 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
F. repeating the step E until the thickness of the metal oxide catalyst intermediate layer on the surface of the conductive substrate is 6-15 mu m;
G. coating the noble metal nitrate coating solution obtained in the step D on the conductive substrate treated in the step F, and heating the conductive substrate to 100-200 ℃ in an inert gas atmosphere for 10-30 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 350-550 ℃ for 10-30 minutes to obtain a conductive substrate with the outer surface of the metal oxide catalyst intermediate layer coated with the metal monoatomic catalyst surface layer;
H. And (C) repeating the step G until the thickness of the metal monoatomic catalyst surface layer on the surface of the conductive substrate is 1-4 mu m, namely the nickel-based active cathode.
As a further improvement of the present invention, the above noble metal nitrate includes ruthenium nitrate, palladium nitrate, iridium nitrate, platinum nitrate, and silver nitrate.
As a further improvement of the present invention, the metal oxide coating layer has a noble metal element content of 78 to 82 mol% and a lanthanoid element content of 18 to 22 mol% in terms of metal component;
the mole percentage of noble metal element in the surface layer of the metal monoatomic catalyst is 78% -82%, and the mole percentage of lanthanide is 18% -22%.
As a further improvement of the present invention, the metal oxide coating layer described above has a noble metal element content of 80% by mole and a lanthanoid element content of 20% by mole, based on the metal component;
the molar percentage of noble metal element in the metal monoatomic catalyst surface layer is 80% and the molar percentage of lanthanide is 20%.
As a further improvement of the invention, in the step E, the mixed solution obtained in the step C is coated on the conductive substrate treated in the step A, and the conductive substrate is heated to 150-250 ℃ in air atmosphere for 20-40 minutes to obtain a first heat treatment conductive substrate;
Then heating the first heat-treated conductive substrate to 450-550 ℃ for 20-40 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
in the step G, the noble metal nitrate coating solution obtained in the step D is coated on the conductive substrate treated in the step F, and the conductive substrate is heated to 120-180 ℃ in the inert gas atmosphere for 15-25 minutes to obtain a first heat treatment conductive substrate;
and then heating the first heat-treated conductive substrate to 400-500 ℃ for 15-25 minutes to obtain the conductive substrate with the metal monoatomic catalyst surface layer coated on the outer surface of the metal oxide catalyst intermediate layer.
As a further improvement of the invention, in the step E, the mixed solution obtained in the step C is coated on the conductive substrate treated in the step A, and the conductive substrate is heated to 180-220 ℃ in air atmosphere for 25-35 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 480-520 ℃ for 25-35 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
In the step G, the noble metal nitrate coating solution obtained in the step D is coated on the conductive substrate treated in the step F, and the conductive substrate is heated to 140-160 ℃ in the inert gas atmosphere for 18-22 minutes to obtain a first heat treatment conductive substrate;
and then heating the first heat-treated conductive substrate to 430-470 ℃ for 18-22 minutes to obtain the conductive substrate with the metal monoatomic catalyst surface layer coated on the outer surface of the metal oxide catalyst intermediate layer.
The nickel-based active cathode is characterized in that a conductive matrix is made of a nickel wire mesh, a metal oxide catalyst middle layer is coated on the outer surface of the conductive matrix of a nickel base material, a metal monoatomic catalyst surface layer is coated on the outer surface of the metal oxide catalyst middle layer, a certain gradient change of atomic components among the conductive matrix, the metal oxide catalyst middle layer and the metal monoatomic catalyst surface layer can be realized through a heat treatment step of E, F, G, H, and the gradient change can obviously slow down the heat effect among the conductive matrix, the metal oxide catalyst middle layer and the metal monoatomic catalyst surface layer, so that the thermal stress is reduced, namely the cracks generated among the conductive matrix, the metal oxide catalyst middle layer and the metal monoatomic catalyst surface layer can be reduced, the binding force among the conductive matrix, the metal oxide catalyst middle layer and the metal monoatomic catalyst surface layer is increased, the service life of an electrode can be obviously prolonged, and the anti-reverse current capability of the electrode is improved.
Example 1.
The preparation method of the nickel-based active cathode comprises the following steps:
pretreatment of conductive substrates
Firstly, carrying out sanding treatment on a 30-mesh nickel base material wire mesh woven by nickel wires with phi of 0.18mm by using 320-mesh white corundum sand as a conductive matrix, then putting clean water into an ultrasonic cleaner, adding a cleaning agent, heating to 50 ℃, putting the conductive matrix into the cleaner, immersing the conductive matrix into the clean water completely, carrying out ultrasonic cleaning for 4 hours, detecting the Al content in the surface mesh of the conductive matrix by using an X-hand-held fluorescent instrument, and removing residual sand on the surface of the surface mesh to obtain the cleaned conductive matrix.
Preparation of intermediate layer of metal oxide catalyst
The embodiment contains ruthenium nitrate and cerium nitrate, wherein the concentration of the ruthenium nitrate is 100g/L, the mole percentage of the ruthenium in the metal salt is 85%, and the mole percentage of the cerium is 15%.
The ruthenium nitrate solution was placed on a magnetic stirrer with a heater and stirred for 10 minutes, and then the cerium nitrate solution was added thereto and stirred for 10 minutes, and then heated and stirred with a heated magnetic stirrer. The solution was incubated for 100 minutes after reaching 80 ℃. The heater for heating the magnetic stirrer was turned off, and the magnetic stirrer was set while stirring and cooled to room temperature.
The prepared nitric acid metal salt solution is uniformly coated on a conductive substrate, firstly, the conductive substrate is burned for 30 minutes in an air atmosphere with the temperature of 200 ℃ and then is burned for 30 minutes in an air atmosphere with the temperature of 500 ℃ continuously, the nitric acid metal salt is subjected to thermal decomposition treatment, the operation is repeated for 8 times, the metal oxide catalyst intermediate layer with the set thickness is obtained, and the content of each element in the metal oxide catalyst intermediate layer is detected by an X-ray fluorescence instrument.
Preparation of surface layer of metal monoatomic catalyst
The embodiment contains a platinum nitrate solution, wherein the concentration of the platinum nitrate is 50g/L, the platinum nitrate metal salt solution is uniformly coated on the surface of a metal oxide catalyst intermediate layer of a conductive substrate, burned for 20 minutes in a nitrogen-containing protective atmosphere with the temperature of 100 ℃ and then continuously burned for 20 minutes in a nitrogen-containing protective atmosphere with the temperature of 450 ℃ to carry out thermal decomposition treatment, the operation is repeated for 4 times, a metal monoatomic catalyst surface layer with a certain thickness is obtained, and the content of the coating is detected by an X-fluorescence meter.
Example 2
The preparation method of the nickel-based active cathode comprises the following steps:
pretreatment of conductive substrates
Firstly, carrying out sanding treatment on a 30-mesh nickel base material nickel screen woven by nickel wires with phi of 0.18mm by using 320-mesh white corundum sand as a conductive matrix, then putting clear water into an ultrasonic cleaner, adding a cleaning agent, heating to 50 ℃, putting the conductive matrix into the clear water, immersing the conductive matrix into the clear water completely, carrying out ultrasonic cleaning for 4 hours, detecting the Al content in the surface screen of the conductive matrix by using an X-hand-held fluorescent instrument, and removing sand remained on the surface of the surface screen to obtain the cleaned conductive matrix.
Preparation of intermediate layer of metal oxide catalyst
The embodiment contains ruthenium nitrate and cerium nitrate, wherein the concentration of the ruthenium nitrate is 100g/L, the mole percentage of the ruthenium in the metal salt is 80%, and the mole percentage of the cerium is 20%.
The ruthenium nitrate solution was placed on a magnetic stirrer with a heater and stirred for 10 minutes, and then the cerium nitrate solution was added thereto and stirred for 10 minutes, and then heated and stirred with a heated magnetic stirrer. The solution was incubated for 100 minutes after reaching 80 ℃. The heater for heating the magnetic stirrer was turned off, and the magnetic stirrer was set while stirring and cooled to room temperature.
The prepared nitric acid metal salt solution is uniformly coated on a conductive substrate, firstly burned for 30 minutes in an air atmosphere with the temperature of 150 ℃ and then burned for 30 minutes in an oxygen-containing atmosphere with the temperature of 450 ℃ for further thermal decomposition treatment, the operation is repeated for 8 times, the metal oxide catalyst intermediate layer with the set thickness is obtained, and the content of each element in the metal oxide catalyst intermediate layer is detected by an X-fluorescence instrument.
(3) Preparation of monoatomic catalyst surface layer
The embodiment contains a platinum nitrate solution, wherein the concentration of the platinum nitrate is 50g/L, the platinum nitrate metal salt solution is uniformly coated on the surface of a metal oxide catalyst intermediate layer of a conductive substrate, the conductive substrate is burned in a nitrogen-containing protective atmosphere at a low temperature of 200 ℃ for 20 minutes, then the conductive substrate is burned in the nitrogen-containing protective atmosphere at a high temperature of 550 ℃ for 20 minutes to carry out thermal decomposition treatment, the operation is repeated for 4 times, a single-atom catalyst surface layer with a certain thickness is obtained, and the content of each element in the single-atom catalyst surface layer is detected by an X-fluorescence meter.
Example 3
The preparation method of the nickel-based active cathode comprises the following steps:
pretreatment of conductive substrates
Firstly, carrying out sanding treatment on a 30-mesh nickel base material nickel screen woven by nickel wires with phi of 0.18mm by using 320-mesh white corundum sand as a conductive matrix, then putting clear water into an ultrasonic cleaner, adding a cleaning agent, heating to 50 ℃, putting the conductive matrix into the clear water, immersing the conductive matrix into the clear water completely, carrying out ultrasonic cleaning for 4 hours, detecting the Al content in the surface screen of the conductive matrix by using an X-hand-held fluorescent instrument, and removing sand remained on the surface of the surface screen to obtain the cleaned conductive matrix.
Preparation of intermediate layer of metal oxide catalyst
The embodiment contains ruthenium nitrate and cerium nitrate, wherein the concentration of the ruthenium nitrate is 100g/L, and the mole percentage of the metal salt is ruthenium: cerium=75%: 25%.
The ruthenium nitrate solution was placed on a magnetic stirrer with a heater and stirred for 10 minutes, and then the cerium nitrate solution was added thereto and stirred for 10 minutes, and then heated and stirred with a heated magnetic stirrer. The solution was incubated for 100 minutes after reaching 80 ℃. The heater for heating the magnetic stirrer was turned off, and the magnetic stirrer was set while stirring and cooled to room temperature.
The prepared nitric acid metal salt solution is uniformly coated on a conductive substrate, firstly burned for 30 minutes in an air atmosphere with the temperature of 200 ℃ at low temperature, then burned for 30 minutes in an oxygen-containing atmosphere with the temperature of 550 ℃ at high temperature, the thermal decomposition treatment is carried out, the operation is repeated for 8 times, the metal oxide catalyst intermediate layer with a certain thickness is obtained, and the content of the coating is detected by an X-fluorescent instrument, so that the coating can be determined to have a preset component.
Preparation of monatomic catalyst surface layer
The embodiment contains a platinum nitrate solution, wherein the concentration of the platinum nitrate is 50g/L, the platinum nitrate metal salt solution is uniformly coated on a metal oxide catalyst intermediate layer of a conductive substrate, burned for 20 minutes in a nitrogen-containing protective atmosphere with the low temperature of 200 ℃, then burned for 20 minutes in a nitrogen-containing protective atmosphere with the high temperature of 500 ℃ for further thermal decomposition treatment, the operation is repeated for 4 times, a monoatomic catalyst surface layer with a certain thickness is obtained, and the content of the coating is detected by an X-fluorescence meter.
Comparative example 1
The nickel-based active cathode of this comparative example and the preparation method thereof are as follows:
pretreatment of conductive substrates
Pretreatment of the substrate was the same as in example 1.
Preparation of metal oxide catalyst
The comparative example contains ruthenium nitrate and cerium nitrate, wherein the concentration of the ruthenium nitrate is 100g/L, and the mole percentage of the metal salt is ruthenium: cerium=85%: 15%.
The ruthenium nitrate solution was placed on a magnetic stirrer with a heater and stirred for 10 minutes, and then the cerium nitrate solution was added thereto and stirred for 10 minutes, and then heated and stirred with a heated magnetic stirrer. The solution was incubated for 100 minutes after reaching 80 ℃. The heater for heating the magnetic stirrer was turned off, and the magnetic stirrer was set while stirring and cooled to room temperature.
The prepared nitric acid metal salt solution is uniformly coated on a conductive substrate, firstly burned for 30 minutes in an air atmosphere with the temperature of 200 ℃ at low temperature, then burned for 30 minutes in an air atmosphere with the temperature of 500 ℃ at high temperature, the thermal decomposition treatment is carried out, the operation is repeated for 12 times, the metal oxide catalyst intermediate layer with a certain thickness is obtained, and the content of the coating is detected by an X-fluorescent instrument, so that the coating can be determined to have a preset component.
Comparative example 2
The nickel-based active cathode of this comparative example and the preparation method thereof are as follows:
pretreatment of conductive substrates
Pretreatment of the substrate was the same as in example 1.
Preparation of intermediate layer of metal oxide catalyst
The comparative example contains ruthenium nitrate and cerium nitrate, wherein the concentration of the ruthenium nitrate is 100g/L, and the mole percentage of the metal salt is ruthenium: cerium=80%: 20%.
The ruthenium nitrate solution was placed on a magnetic stirrer with a heater and stirred for 10 minutes, and then the cerium nitrate solution was added thereto and stirred for 10 minutes, and then heated and stirred with a heated magnetic stirrer. The solution was incubated for 100 minutes after reaching 80 ℃. The heater for heating the magnetic stirrer was turned off, and the magnetic stirrer was set while stirring and cooled to room temperature.
The prepared nitric acid metal salt solution is uniformly coated on a conductive substrate, firstly burned for 30 minutes in an air atmosphere with the temperature of 150 ℃ and then burned for 30 minutes in an air atmosphere with the temperature of 450 ℃ for further thermal decomposition treatment, the operation is repeated for 12 times, a metal oxide catalyst intermediate layer with a certain thickness is obtained, and the content of the coating is detected by an X-fluorescent instrument, so that the coating can be determined to have a preset component.
Preparation of catalyst surface layer
The method comprises the steps of uniformly coating a platinum nitrate metal salt solution on a metal oxide catalyst intermediate layer of a conductive substrate in an air atmosphere with the temperature of 200 ℃ at a low temperature for 20 minutes, continuously burning for 20 minutes in the air atmosphere with the temperature of 450 ℃ at a high temperature for thermal decomposition treatment, repeating the operation for 4 times to obtain the metal oxide catalyst intermediate layer with a certain thickness, and detecting the content of the coating by an X-fluorescence instrument.
Comparative example 3
The nickel-based active cathode of this comparative example and the preparation method thereof are as follows:
pretreatment of conductive substrates
Pretreatment of the substrate was the same as in example 1.
Preparation of intermediate layer of metal oxide catalyst
The comparative example contains ruthenium nitrate and cerium nitrate, wherein the concentration of the ruthenium nitrate is 100g/L, and the mole percentage of the metal salt is ruthenium: cerium=75%: 25%.
The ruthenium nitrate solution was placed on a magnetic stirrer with a heater and stirred for 10 minutes, and then the cerium nitrate solution was added thereto and stirred for 10 minutes, and then heated and stirred with a heated magnetic stirrer. The solution was incubated for 100 minutes after reaching 80 ℃. The heater for heating the magnetic stirrer was turned off, and the magnetic stirrer was set while stirring and cooled to room temperature.
The prepared nitric acid metal salt solution is uniformly coated on a conductive substrate, firstly burned for 30 minutes in an air atmosphere with the temperature of 200 ℃ at low temperature, then burned for 30 minutes in an air atmosphere with the temperature of 500 ℃ at high temperature, the thermal decomposition treatment is carried out, the operation is repeated for 12 times, the metal oxide catalyst intermediate layer with a certain thickness is obtained, and the content of the coating is detected by an X-fluorescent instrument, so that the coating can be determined to have a preset component.
Preparation of catalyst surface layer
And uniformly coating the chloroplatinic acid solution on the metal oxide catalyst intermediate layer of the conductive substrate in a nitrogen protection atmosphere with the low temperature of 200 ℃ for 20 minutes, continuously burning for 20 minutes in the nitrogen protection atmosphere with the high temperature of 500 ℃ for thermal decomposition treatment, and repeating the operation for 4 times to obtain the noble metal oxide catalyst surface layer with a certain thickness.
Comparative example 4
The nickel-based active cathode of this comparative example and the preparation method thereof are as follows:
pretreatment of conductive substrates
Pretreatment of the substrate was the same as in example 1.
Preparation of intermediate layer of metal oxide catalyst
The comparative example contains ruthenium nitrate and cerium nitrate, wherein the concentration of the ruthenium nitrate is 100g/L, and the mole percentage of the metal salt is ruthenium: cerium=75%: 25%.
The ruthenium nitrate solution was placed on a magnetic stirrer with a heater and stirred for 10 minutes, and then the cerium nitrate solution was added thereto and stirred for 10 minutes, and then heated and stirred with a heated magnetic stirrer. The solution was incubated for 100 minutes after reaching 80 ℃. The heater for heating the magnetic stirrer was turned off, and the magnetic stirrer was set while stirring and cooled to room temperature.
The prepared nitric acid metal salt solution is uniformly coated on a conductive substrate, firstly burned for 30 minutes in an air atmosphere with the temperature of 200 ℃ at low temperature, then burned for 30 minutes in an air atmosphere with the temperature of 500 ℃ at high temperature, the thermal decomposition treatment is carried out, the operation is repeated for 12 times, the metal oxide catalyst intermediate layer with a certain thickness is obtained, and the content of the coating is detected by an X-fluorescent instrument, so that the coating can be determined to have a preset component.
Preparation of catalyst surface layer
The method comprises the steps of uniformly coating a platinum nitrate metal salt solution on a metal oxide catalyst intermediate layer of a conductive substrate in an air atmosphere with the temperature of 200 ℃ for 20 minutes, continuously burning for 20 minutes in the air atmosphere with the temperature of 500 ℃ for further thermal decomposition treatment, repeating the operation for 4 times to obtain a catalyst surface layer with a certain thickness, and then keeping the catalyst surface layer for 4 hours in an argon atmosphere with the temperature of 500 ℃ to reduce the platinum oxide into a monoatomic structure. The method can determine that the coating has a predetermined composition by detecting the coating content by an X-ray fluorescence meter.
FIG. 1b is a surface morphology diagram of a nickel-based active cathode prepared in example 1 of the present invention, and FIG. 1a is a surface morphology diagram of comparative example 1. As can be seen by comparison, comparative example 1 is a nickel-based single catalyst coated electrode, the size of crystal grains on the surface of the electrode is different, the dispersion of crystal grains is uneven, gaps among the crystal grains are larger, and the electrode easily enters a substrate to cause corrosion when contacting acidic substances, thereby causing the electrode coating to fall off; FIG. 1b shows a composite coated electrode of the nickel-based active cathode of example 1, the surface of the electrode has compact crystal distribution and smaller inter-grain gaps, and compared with the crystal particles of a single coated electrode, the crystal particles of the composite coated electrode have uniformly distributed thereon the nanorods of fine T oxide, and the nanorods can be observed to grow on the surface of the bottom catalytic coating layer under a scanning electron microscope with magnification, and the bonding force with the bottom layer is good, so that the special structure leads to the composite coated electrode having better performance than the single coated electrode, and the stress-resistance and reverse current capability of the electrode are improved.
FIG. 2b is a cross-sectional view of the nickel-based active cathode prepared in example 2 of the present invention, and FIG. 2a is a cross-sectional view of comparative example 2. As can be seen from FIG. 2a, the air-atmosphere-sintered catalyst layer of comparative example 2 is relatively loose and has poor bonding force with the nickel substrate; in the embodiment 2, the catalyst layer of the composite coating electrode has uniform thickness, the bonding force between the surface catalyst layer and the nickel matrix is good, and the anti-reverse current capability of the electrode is improved.
Performance testing of cathodes fabricated in examples and comparative examples
1. The hydrogen evolution potential detection is carried out in a sodium hydroxide solution with the electrolyte of 32% by mass at 90 ℃, and the result is as follows:
4kA/m 2 hydrogen evolution potential (vs. sce)
Example 1 1.198
Example 2 1.196
Example 3 1.195
Comparative example 1 1.225
Comparative example 2 1.211
Comparative example 3 1.215
Comparative example 4 1.201
It can be seen from the table that the cathodic hydrogen evolution potential in each example is relatively low and is much lower than the single-coated electrode potential of comparative example 1. The potential of the composite electrode burned under the air atmosphere was also lowered as compared with that of comparative example 2. The phase potential of the monoatomic catalytic layer prepared by chloroplatinic acid in comparative example 3 is lower and is close to that of the composite electrode treated by argon in comparative example 4 (see figure 3).
2. And (3) carrying out the enhanced reverse electric test, namely continuously carrying out the enhanced reverse electric acceleration test for a plurality of times by electrolysis in a sodium hydroxide solution with the electrolyte of which the mass fraction is 32%, and measuring the coating residue. Fig. 4 is a graph showing the comparison of the residual amount of Ru in the stress-resistant electric power comparison coating, and the residual amount of the composite coating electrode in the example after a plurality of cycles is significantly higher than that of the single coating electrode in the comparative example 1, and the composite coating electrode burned in the air atmosphere of the comparative example 2 also has a certain stress-resistant reverse current capability, but the stress-resistant reverse current capability is slightly worse than that of the electrode in the example. Comparative example 3 a composite electrode made of chloroplatinic acid as a raw material, whose coating residual amount drastically decreases with an increase in the reverse electric cycle, was not strong in the reverse electric resistance. The composite electrode in comparative example 4 was treated with argon gas, and the platinum element was reduced from the oxidized state to elemental platinum, but at the same time, part of ruthenium oxide was reduced to metallic ruthenium, resulting in a decrease in the binding force of the coating, thereby affecting the stress-reverse current resistance of the electrode, which means that the composite coated electrode of the present invention has a stronger stress-reverse current resistance.
Fig. 5 is a graph showing comparison of the residual amount of Pt in the stress-resistance capacity versus coating, and it can be seen from fig. 5 that the residual amount of Pt in the composite coating electrode in each example is relatively high after a plurality of cycles. The invention can effectively inhibit the damage of the reverse current to the cathode surface net.
The above examples are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the scope of protection defined by the claims of the present invention without departing from the design spirit of the present invention.

Claims (9)

1. The nickel-based active cathode is characterized by comprising a conductive matrix of a nickel base material, wherein the conductive matrix is made of a nickel screen, the outer surface of the conductive matrix is coated with a metal oxide catalyst intermediate layer, and the outer surface of the metal oxide catalyst intermediate layer is coated with a metal monoatomic catalyst surface layer;
the metal oxide catalyst intermediate layer is composed of an oxide of a noble metal element and an oxide of a lanthanide, the thickness of the metal oxide catalyst intermediate layer is 6-15 mu m, and the metal oxide coating comprises 75-85% of the noble metal element and 15-25% of the lanthanide by mole percent;
The metal monoatomic catalyst surface layer is composed of noble metal elements, and the thickness of the metal monoatomic catalyst surface layer is 1-4 mu m;
the nickel-based active cathode is prepared by the following steps:
A. preparing a conductive matrix of a nickel substrate by using a nickel screen, cleaning the conductive matrix, removing surface dirt of the conductive matrix, and roughening the surface of the conductive matrix;
B. preparing soluble nitrate of lanthanide and soluble nitrate of noble metal element, respectively dissolving the soluble nitrate of lanthanide and soluble nitrate of noble metal element in water to obtain soluble nitrate solution of lanthanide and soluble nitrate solution of noble metal element for use;
C. mixing the soluble nitrate solution of the lanthanide obtained in the step B and the noble metal nitrate solution according to the proportion that the mole percentage of noble metal elements is 75% -85%, and the mole percentage of the lanthanide is 15% -25%, wherein the concentration of the noble metal in the mixed solution is 100-120 g/L, so as to obtain a mixed solution;
D. b, regulating and controlling the concentration of noble metal in the noble metal nitrate solution prepared in the step B to 50-80 g/L to obtain a noble metal nitrate coating solution;
E. coating the mixed solution obtained in the step C on the conductive substrate treated in the step A, and heating the conductive substrate to 100-300 ℃ in air atmosphere for 10-50 minutes to obtain a first heat treatment conductive substrate;
Then heating the first heat-treated conductive substrate to 400-600 ℃ for 10-50 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
F. repeating the step E until the thickness of the metal oxide catalyst intermediate layer on the surface of the conductive substrate is 6-15 mu m;
G. coating the noble metal nitrate coating solution obtained in the step D on the conductive substrate treated in the step F, and heating the conductive substrate to 100-200 ℃ in an inert gas atmosphere for 10-30 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 350-550 ℃ for 10-30 minutes to obtain a conductive substrate with the outer surface of the metal oxide catalyst intermediate layer coated with the metal monoatomic catalyst surface layer;
H. repeating the step G until the thickness of the metal monoatomic catalyst surface layer on the surface of the conductive substrate is 1-4 mu m, namely the nickel-based active cathode;
the noble metal nitrate comprises ruthenium nitrate, palladium nitrate, iridium nitrate, platinum nitrate and silver nitrate, wherein the metal oxide coating comprises 78-82 mol percent of noble metal elements and 18-22 mol percent of lanthanoid elements according to metal components;
The mole percentage of noble metal element in the surface layer of the metal monoatomic catalyst is 78% -82%, and the mole percentage of lanthanide is 18% -22%.
2. The nickel-based active cathode according to claim 1, wherein the metal oxide coating layer has a noble metal element content of 80 mole percent and a lanthanoid element content of 20 mole percent, based on the metal component;
the molar percentage of noble metal element in the metal monoatomic catalyst surface layer is 80% and the molar percentage of lanthanide is 20%.
3. The nickel-based active cathode according to claim 1 or 2, wherein in the step E, the mixed solution obtained in the step C is coated on the conductive substrate treated in the step a, and the conductive substrate is heated to 150 ℃ to 250 ℃ in an air atmosphere for 20 minutes to 40 minutes to obtain a first heat-treated conductive substrate;
then heating the first heat-treated conductive substrate to 450-550 ℃ for 20-40 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
the step G is to coat the noble metal nitrate coating solution obtained in the step D on the conductive substrate treated in the step F, and heat the conductive substrate to 120-180 ℃ in inert gas atmosphere for 15-25 minutes to obtain a first heat treatment conductive substrate;
And then heating the first heat-treated conductive substrate to 400-500 ℃ for 15-25 minutes to obtain the conductive substrate with the metal monoatomic catalyst surface layer coated on the outer surface of the metal oxide catalyst intermediate layer.
4. The preparation method of the nickel-based active cathode is characterized by comprising the following steps:
A. preparing a conductive matrix of a nickel substrate by using a nickel screen, cleaning the conductive matrix, removing surface dirt of the conductive matrix, and roughening the surface of the conductive matrix;
B. preparing soluble nitrate of lanthanide and soluble nitrate of noble metal element, respectively dissolving the soluble nitrate of lanthanide and soluble nitrate of noble metal element in water to obtain soluble nitrate solution of lanthanide and soluble nitrate solution of noble metal element for use;
C. mixing the soluble nitrate solution of the lanthanide obtained in the step B and the noble metal nitrate solution according to the proportion that the mole percentage of noble metal elements is 75% -85%, and the mole percentage of the lanthanide is 15% -25%, wherein the concentration of the noble metal in the mixed solution is 100-120 g/L, so as to obtain a mixed solution;
D. b, regulating and controlling the concentration of noble metal in the noble metal nitrate solution prepared in the step B to 50-80 g/L to obtain a noble metal nitrate coating solution;
E. Coating the mixed solution obtained in the step C on the conductive substrate treated in the step A, and heating the conductive substrate to 100-300 ℃ in air atmosphere for 10-50 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 400-600 ℃ for 10-50 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
F. repeating the step E until the thickness of the metal oxide catalyst intermediate layer on the surface of the conductive substrate is 6-15 mu m;
G. coating the noble metal nitrate coating solution obtained in the step D on the conductive substrate treated in the step F, and heating the conductive substrate to 100-200 ℃ in an inert gas atmosphere for 10-30 minutes to obtain a first heat treatment conductive substrate;
then heating the first heat-treated conductive substrate to 350-550 ℃ for 10-30 minutes to obtain a conductive substrate with the outer surface of the metal oxide catalyst intermediate layer coated with the metal monoatomic catalyst surface layer;
H. and (C) repeating the step G until the thickness of the metal monoatomic catalyst surface layer on the surface of the conductive substrate is 1-4 mu m, namely the nickel-based active cathode.
5. The method of preparing a nickel-based active cathode according to claim 4, wherein the noble metal nitrate comprises ruthenium nitrate, palladium nitrate, iridium nitrate, platinum nitrate, and silver nitrate.
6. The method for producing a nickel-based active cathode according to claim 5, wherein the metal oxide coating layer comprises 78 to 82 mol% of noble metal element and 18 to 22 mol% of lanthanoid element, based on the metal component;
the mole percentage of noble metal element in the surface layer of the metal monoatomic catalyst is 78% -82%, and the mole percentage of lanthanide is 18% -22%.
7. The nickel-based active cathode according to claim 6, wherein the metal oxide coating layer has a noble metal element content of 80 mole percent and a lanthanoid element content of 20 mole percent, based on the metal component;
the molar percentage of noble metal element in the metal monoatomic catalyst surface layer is 80% and the molar percentage of lanthanide is 20%.
8. The nickel-based active cathode according to any one of claims 4 to 7, wherein in the step E, the mixed solution obtained in the step C is coated on the conductive substrate treated in the step a, and the conductive substrate is heated to 150 ℃ to 250 ℃ in an air atmosphere for 20 minutes to 40 minutes to obtain a first heat-treated conductive substrate;
Then heating the first heat-treated conductive substrate to 450-550 ℃ for 20-40 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
the step G is to coat the noble metal nitrate coating solution obtained in the step D on the conductive substrate treated in the step F, and heat the conductive substrate to 120-180 ℃ in inert gas atmosphere for 15-25 minutes to obtain a first heat treatment conductive substrate;
and then heating the first heat-treated conductive substrate to 400-500 ℃ for 15-25 minutes to obtain the conductive substrate with the metal monoatomic catalyst surface layer coated on the outer surface of the metal oxide catalyst intermediate layer.
9. The nickel-based active cathode according to claim 8, wherein in the step E, the mixed solution obtained in the step C is coated on the conductive substrate treated in the step A, and the conductive substrate is heated to 180-220 ℃ in an air atmosphere for 25-35 minutes to obtain a first heat-treated conductive substrate;
then heating the first heat-treated conductive substrate to 480-520 ℃ for 25-35 minutes to obtain a conductive substrate with the outer surface coated with the metal oxide catalyst intermediate layer;
In the step G, the noble metal nitrate coating solution obtained in the step D is coated on the conductive substrate treated in the step F, and the conductive substrate is heated to 140-160 ℃ in the inert gas atmosphere for 18-22 minutes to obtain a first heat treatment conductive substrate;
and then heating the first heat-treated conductive substrate to 430-470 ℃ for 18-22 minutes to obtain the conductive substrate with the metal monoatomic catalyst surface layer coated on the outer surface of the metal oxide catalyst intermediate layer.
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