Layered double-metal hydroxide electrode doped with p-region metal and preparation method and application of layered double-metal hydroxide electrode

Abstract

The invention discloses a p-region metal doped layered double-metal hydroxide electrode as well as a preparation method and application thereof. The p-region metal doped layered double-metal hydroxide electrode comprises a metal substrate and a p-region metal doped layered double-metal hydroxide catalyst deposited on the metal substrate, the p-region metal doped layered double-metal hydroxide catalyst comprises a p-region metal and a layered double-metal hydroxide; and the p-region metal is selected from one or more of aluminum, gallium, tin and indium. The preparation method can be completed within one minute at least through a simple, controllable and mild one-step electrodeposition method, the prepared p-region metal-doped layered double-metal hydroxide electrode is adjustable in size and shape, can be used as an OER anode to meet the requirements of different electrolytic bath specifications in practical application, is used for water electrolysis for hydrogen production, and has a wide application prospect. The activity and the stability of integral hydrogen production through water electrolysis can be improved, and the application potential is huge.

Description

Technical Field

[0001] The invention relates to the technical field of water electrolyzer electrodes, and in particular to a p-region metal-doped layered double metal hydroxide electrode and a preparation method and application thereof. Background Art

[0002] Compared with traditional hydrogen production methods that rely on fossil fuels, water electrolysis technology driven by renewable electricity can achieve clean, efficient, sustainable and high-purity production of carbon-free "green hydrogen". However, the overall efficiency of water electrolysis technology faces severe challenges. Its bottleneck lies in the oxygen evolution reaction (OER) occurring on the anode. The kinetic hysteresis of this half-reaction greatly limits the overall efficiency of water electrolysis. Therefore, in order to effectively accelerate the OER kinetics and improve the overall efficiency of the water electrolyzer, it is urgent to develop new, efficient and low-cost OER anodes.

[0003] At present, in the field of OER electrode research, compared with acidic electrolyzers based on electrodes of precious metal catalysts, alkaline electrolyzer technology (such as alkaline water electrolyzers and anion exchange membrane (AEM) electrolyzers) has attracted attention from academia and industry. The electrodes of alkaline electrolyzers are mainly based on non-precious transition metals and their alloys (such as Raney nickel), which greatly reduces their commercial costs. However, the catalytic performance of existing alkaline OER electrodes still needs to be further improved. In addition, the preparation process of commercial alkaline OER electrodes is relatively complicated, and spraying operations are often required, especially plasma spraying technology. This technology not only has high temperature and high energy consumption, and high equipment cost, but also has strict requirements on catalyst particles. Smaller particles such as nano-scale catalysts are difficult to achieve plasma spraying due to fluidity problems. Therefore, it is of great technical value and economic benefit to develop a simple, direct, economical, easy-to-regulate and scalable preparation method to firmly fix highly active and large specific surface area nano-scale non-precious transition metal-based catalysts on the substrate surface to prepare alkaline OER electrodes.

[0004] In addition, it has been generally confirmed in academic research that most non-precious metal nickel / cobalt / iron-based catalysts undergo in-situ reconstruction during the alkaline OER process and transform into the corresponding oxyhydroxides (Ni / Co / FeOOH x ), as the real active phase. When Ni / Co is combined with Fe components, NiFeOOH generated in situ in alkaline OER x / CoFeOOH x It exhibits extremely excellent catalytic activity, among which Fe atoms have extremely high intrinsic activity in the catalytic OER process ( J. Phys. Chem. Lett. 2015, 6 , 3737–3742). However, in the OER voltage under strong alkaline environment, Fe is easily converted to FeO4 2- species that is highly water soluble (GK Schweitzer, LL Pesterfield, The Aqueous hemistry of the Elements , 2010). Therefore, NiFeOOH x / CoFeOOH x The Fe in the OER electrode is prone to dissolution, which leads to a significant reduction in the overall catalytic performance. In actual electrolyzer application scenarios, high reaction voltage, current density, and operating temperature will further aggravate the dissolution of the active phase Fe, seriously hindering the actual industrial application of this type of OER electrode. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a p-region metal-doped layered double hydroxide electrode and a preparation method and application thereof. The p-region metal-doped layered double hydroxide electrode is obtained by depositing a p-region metal-doped layered double hydroxide catalyst on a metal substrate, which can be used as an OER anode of an alkaline electrolyzer for electrolyzing water to produce hydrogen.

[0006] The present invention is achieved through the following technical solutions: A first aspect of the present invention provides a p-region metal-doped layered double metal hydroxide electrode, the p-region metal-doped layered double metal hydroxide electrode comprising a metal substrate and a p-region metal-doped layered double metal hydroxide catalyst deposited on the metal substrate; The p-zone metal-doped layered double metal hydroxide catalyst comprises a p-zone metal and a layered double metal hydroxide; the p-zone metal is selected from one or more of aluminum, gallium, tin and indium; the layered double metal hydroxide is a nickel-iron layered double metal hydroxide, a cobalt-iron layered double metal hydroxide or a nickel-cobalt-iron layered double metal hydroxide.

[0007] Furthermore, the molar amount of the p-zone metal is less than 30% of the molar amount of all metals in the p-zone metal-doped layered double hydroxide catalyst, preferably 3-10%.

[0008] The metal elements in the p-block exist in the form of oxygen-containing anions or insoluble (hydrogen) oxide phases during the electrochemical process (no electrochemical activity, only acting as regulators), thereby regulating and optimizing the nickel-iron hydroxide phase, cobalt-iron hydroxide phase or nickel-cobalt-iron hydroxide phase (active components responsible for the electrochemical reaction) that are simultaneously reconstructed in situ. When the amount of inactive regulator is too much, the active components will decrease, resulting in poor performance.

[0009] Furthermore, the molar amount of any metal in the layered double hydroxide (LDH) accounts for more than 5% of the molar amount of all metals in the p-zone metal-doped layered double hydroxide catalyst, preferably 15-85%.

[0010] Furthermore, the metal substrate is foam metal or metal mesh, including but not limited to foam nickel, foam cobalt, nickel mesh, and cobalt mesh.

[0011] The second aspect of the present invention provides a method for preparing the p-zone metal-doped layered double hydroxide electrode according to the first aspect, comprising the following steps: (1) dissolving a p-zone metal salt and an iron salt in water, and then adding a nickel salt and / or a cobalt salt to obtain a deposition solution; (2) placing a metal substrate in the deposition solution obtained in step (1), and electrodepositing a p-region metal-doped layered double metal hydroxide catalyst on the metal substrate by an electrodeposition method to prepare the p-region metal-doped layered double metal hydroxide electrode.

[0012] The present invention can quickly convert the low-cost and widely available nickel / cobalt / iron salts into corresponding layered double metal hydroxides through a simple, controllable and mild one-step electrodeposition method, and directly grow them on a metal substrate; at the same time, the p-zone metal in the deposition solution is synchronously doped into the layered double metal hydroxide catalyst grown on the metal substrate during the electrodeposition process. The present invention can prepare a self-supporting electrode without a polymer linker within one minute at the shortest, which is composed of a metal substrate and a p-zone metal-doped layered double metal hydroxide catalyst deposited on the metal substrate, without the need for an additional spraying step. In addition, the present invention can precisely control the preparation time, size, and deposited catalyst components and deposition amount of the final electrode by controlling the ratio and type of nickel / cobalt / iron salts, the electrodeposition time, the deposition voltage, and the size of the metal substrate, which will be conducive to meeting the high requirements of cost, output, and electrolytic cell equipment compatibility for the industrial application of water electrolysis electrodes, and is suitable for large-scale production at a relatively low cost, and has huge application potential.

[0013] Furthermore, in step (1), the p-zone metal salt is a nitrate and / or chloride salt of a p-zone metal, the iron salt is a nitrate and / or chloride salt of iron, the nickel salt is a nitrate and / or chloride salt of nickel, and the cobalt salt is a nitrate and / or chloride salt of cobalt.

[0014] Furthermore, in step (1), the concentration of the p-region metal ions in the deposition solution is less than 0.05 M, preferably less than 0.01 M.

[0015] Furthermore, in step (1), the molar amount of the p-zone metal salt accounts for less than 30% of the molar amount of all metal salts (based on the molar ratio of the metal), preferably 3-10%.

[0016] Furthermore, in step (1), the molar ratio of the iron salt to the nickel salt and / or the cobalt salt is (0.1-10):1 (based on the molar ratio of the metals).

[0017] In a specific embodiment, in step (1), the p-zone metal salt, iron salt, nickel salt and / or cobalt salt are dissolved in water, and ultrasonically dissolved to obtain a deposition solution.

[0018] Furthermore, the ultrasonication time is 10-60 min.

[0019] Furthermore, in step (2), the electrodeposition method adopts a three-electrode system or a two-electrode system, wherein the three-electrode system includes a reference electrode, a counter electrode and a working electrode, and the metal substrate is used as the working electrode to deposit the target catalyst on the surface of the metal substrate; the two-electrode system includes a cathode and an anode, and the metal substrate is used as the cathode to deposit the target catalyst on the surface of the metal substrate serving as the cathode.

[0020] Furthermore, in step (2), the three-electrode system uses a saturated calomel electrode as a reference electrode and a metal electrode as a counter electrode.

[0021] Furthermore, the metal electrode is a foam metal or a metal mesh, including but not limited to foam nickel, foam cobalt, nickel mesh, and cobalt mesh.

[0022] Furthermore, in step (2), the two-electrode system has the metal substrate as the cathode and the metal electrode as the anode.

[0023] Furthermore, the metal electrode is a foam metal or a metal mesh, including but not limited to foam nickel, foam cobalt, nickel mesh, and cobalt mesh.

[0024] In a specific embodiment, the size, mass and shape of the metal substrate used can be adjusted in advance according to the specifications of the electrolytic cell.

[0025] Furthermore, in step (2), when a three-electrode system is used, the voltage of the electrodeposition is -0.5 to -2.5 V (relative to a saturated calomel reference electrode); when a two-electrode system is used, the voltage of the electrodeposition is -1 to -3 V.

[0026] Furthermore, in step (2), the electrodeposition can be completed within one minute at the shortest (e.g., the electrodeposition time is one minute), and the longest time can be adjusted as needed. In principle, it can be set until all metal elements in the deposition solution are deposited on the metal substrate.

[0027] Furthermore, in step (2), after the electrodeposition is completed, the step of rinsing and drying the electrode is also included.

[0028] In a specific embodiment, in step (2), the electrode after electrodeposition is rinsed with water and then dried naturally.

[0029] Furthermore, in step (2), the deposition amount of the p-zone metal-doped layered double hydroxide catalyst on the metal substrate is 0.5-500 mg·cm -2 .

[0030] The p-zone metal-doped layered double hydroxide electrode provided by the present invention has adjustable size and shape, and can meet the requirements of different electrolytic cell specifications in practical applications.

[0031] The third aspect of the present invention provides the use of the p-region metal-doped layered double hydroxide electrode described in the first aspect in an alkaline electrolytic cell.

[0032] Under the OER potential of a strong alkaline environment, the doped p-block metal tends to form soluble oxygen-containing anions or insoluble (hydr)oxides. Although most of the soluble oxygen-containing anions dissolve in the aqueous electrolyte, some of them tend to be re-adsorbed on the surface of the in-situ generated bimetallic oxyhydroxide active phase (nickel-iron oxyhydroxide active phase, cobalt-iron oxyhydroxide active phase or nickel-cobalt-iron oxyhydroxide active phase), thereby regulating the electronic structure, reaction kinetics, and adsorption strength of the active phase with the intermediates, and can effectively inhibit the precipitation of non-precious metal elements (such as Fe) with the highest intrinsic activity during the anodic alkaline OER reaction; as for insoluble (hydr)oxides, the in-situ reconstructed p-block metal (hydr)oxides are heterogeneously coupled with the bimetallic oxyhydroxide active phase. This phenomenon can not only regulate the electronic structure and intrinsic activity of the active phase, but also constrain its random stacking and agglomeration, thereby avoiding the massive flooding of active transition sites.

[0033] Therefore, the present invention dopes the p-zone metal into the layered double metal hydroxide catalyst firmly grown on the metal substrate by a one-step electrodeposition method. The doping of the p-zone metal can effectively regulate and optimize the bimetallic oxyhydroxide active phase generated in situ during the alkaline OER process, enhance its intrinsic activity and reaction kinetics of catalyzing alkaline OER, promote the exposure of more active sites, and solve the stubborn problem of large-scale dissolution of highly active iron components, thereby essentially improving the catalytic activity and stability of the electrode.

[0034] Furthermore, the alkaline electrolyzer includes an alkaline water electrolyzer and an anion exchange membrane (AEM) electrolyzer.

[0035] Furthermore, the alkaline water electrolyzer comprises an anode, a cathode and an electrolyte, and the anode is the p-region metal-doped layered double metal hydroxide electrode described in the first aspect.

[0036] Furthermore, the anion exchange membrane electrolyzer comprises an anode, a cathode, an anion exchange membrane and an electrolyte, and the anode is the p-region metal-doped layered double hydroxide electrode described in the first aspect.

[0037] The p-zone metal-doped layered double metal hydroxide electrode provided by the present invention is also expected to be applied to the fields of hydrogen fuel cells, direct alcohol fuel cells, etc., and has considerable ductility and applicability.

[0038] The fourth aspect of the present invention provides an alkaline electrolytic cell, comprising an anode, a cathode and an electrolyte, wherein the anode is the p-region metal-doped layered double hydroxide electrode described in the first aspect.

[0039] Furthermore, the cathode may be nickel-molybdenum foam or nickel foam loaded with platinum / carbon (Pt / C).

[0040] Furthermore, the electrolyte may be a potassium hydroxide (KOH) aqueous solution.

[0041] The p-zone metal-doped layered double metal hydroxide electrode provided by the present invention is used as an anode in an alkaline electrolytic cell and exhibits excellent water electrolysis activity and stability at a high current density.

[0042] Furthermore, the alkaline electrolytic cell includes an alkaline water electrolytic cell and an AEM electrolytic cell.

[0043] The fifth aspect of the present invention provides the use of the p-zone metal-doped layered double hydroxide electrode described in the first aspect or the alkaline electrolyzer described in the fourth aspect in the electrolysis of water to produce hydrogen.

[0044] The beneficial effects of the present invention are: 1. The present invention avoids the complex, high energy consumption, high cost and environmentally harmful preparation process of conventional alkaline OER electrodes. The one-step electrodeposition method provided is simple, direct, rapid and mild in conditions. While generating the p-zone metal-doped layered double hydroxide catalyst, it is firmly loaded on the metal substrate. The overall operation time can be completed in as short as one minute. The present invention also avoids the use of additional spraying steps and polymer linkers, has low cost, low energy consumption, strong operability and is easy for industrial production.

[0045] 2. The p-zone metal-doped layered double hydroxide electrode provided by the present invention, in alkaline OER, the p-zone metal will regulate the in-situ reconstructed bimetallic oxyhydroxide active phase, improve its reaction thermodynamics and kinetics, promote the exposure of active sites, and restrict the dissolution of its active metals (especially iron with high intrinsic activity), thereby improving the overall activity and stability of hydrogen production by water electrolysis.

[0046] 3. The p-zone metal-doped layered double hydroxide electrode provided by the present invention can change its size, mass, shape, and catalyst loading according to the parameter specifications of the assembled electrolytic cell, and is easy to commercialize. In addition, the p-zone metal-doped layered double hydroxide electrode provided by the present invention has considerable scalability, and a variety of different p-zone metals can be selected or combined according to needs.

[0047] 4. The AEM electrolytic cell provided by the present invention, which uses a p-zone metal-doped layered double hydroxide electrode as an anode, can achieve a current of 5.4 A·cm with an operating temperature of 80°C and a cell voltage of only 2.2 V. -2 The ultra-high current density is far higher than the current density (1 A·cm -2 ), which proves that the p-zone metal-doped layered double hydroxide electrode provided by the present invention has excellent practical application capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 These are actual pictures of NiFeAl-LDH electrodes of different shapes in Example 1; wherein a is a square NiFeAl-LDH electrode, and b is a circular NiFeAl-LDH electrode.

[0049] Figure 2 This is a scanning electron microscope (SEM) image of the NiFeAl-LDH electrode of Example 1; wherein the scale of a is 20 micrometers, the scale of b is 2 micrometers, and the scale of c is 500 nanometers.

[0050] Figure 3 The scanning electron microscope-energy dispersive X-ray spectrum (SEM-EDX) element mapping diagram and spectrum diagram of the NiFeAl-LDH catalyst of Example 1; wherein a is the Ni element mapping diagram, b is the Fe element mapping diagram, c is the Al element mapping diagram, d is the O element mapping diagram, and e is the spectrum diagram.

[0051] Figure 4 The X-ray diffraction (XRD) patterns of the NiFeAl-LDH catalyst of Example 1 and the NiFe-LDH catalyst of Comparative Example 1 are shown.

[0052] Figure 5 It is a linear sweep voltammetry (LSV) curve of water electrolysis of an alkaline water electrolyzer using the NiFeAl-LDH electrode of Example 1, the NiFeGa-LDH electrode of Example 2, the NiFeSn-LDH electrode of Example 3, the NiFeIn-LDH electrode of Example 4 and the NiFe-LDH electrode of Comparative Example 1 as the anode.

[0053] Figure 6The linear sweep voltammetry (LSV) curve of water electrolysis in an AEM electrolytic cell using the NiFeAl-LDH electrode of Example 1 as the anode. DETAILED DESCRIPTION

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0055] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0056] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used are all available from commercial sources unless otherwise specified.

[0057] Example 1

[0058] An aluminum-doped nickel-iron layered double hydroxide (NiFeAl-LDH) electrode comprises a nickel foam and an aluminum-doped nickel-iron layered double hydroxide (NiFeAl-LDH) catalyst deposited on the nickel foam. The preparation method comprises the following steps: The Ni(NO 3 ) 2 6H 2 O, Fe(NO 3 ) 3 9H 2 O and AlCl 3 6H 2 O was dissolved in deionized water at a metal molar ratio of 3:1:0.24, and a deposition solution was obtained after ultrasonication at room temperature for 30 minutes. A two-electrode system was constructed with nickel foam as the cathode and anode and placed in the deposition solution. Electrodeposition was performed for one minute at an overall voltage of -1.2 V, and the nickel foam as the cathode was loaded with NiFeAl-LDH catalyst, which was then rinsed with deionized water and dried naturally to obtain a NiFeAl-LDH electrode.

[0059] The deposition amount of NiFeAl-LDH catalyst is about 25 mg cm -2 , the electrode shape is square (side length is 200 mm) or circular (diameter is 200 mm).

[0060] Figure 1Figure 1 is a physical picture of NiFeAl-LDH electrodes of different shapes in Example 1; wherein a is a square NiFeAl-LDH electrode, and b is a circular NiFeAl-LDH electrode. Figure 1 It can be seen that the NiFeAl-LDH catalyst is uniformly deposited on the square / circular nickel foam.

[0061] Figure 2 is a scanning electron microscope (SEM) image of the NiFeAl-LDH electrode of Example 1. Figure 2 It can be seen that the surface of the NiFeAl-LDH electrode presents a lamellar structure, which is consistent with the typical morphological characteristics of LDH.

[0062] Example 2

[0063] A gallium-doped nickel-iron layered double hydroxide (NiFeGa-LDH) electrode comprises nickel foam and a gallium-doped nickel-iron layered double hydroxide (NiFeGa-LDH) catalyst deposited on the nickel foam, and a preparation method comprises the following steps: The Ni(NO 3 ) 2 6H 2 O, Fe(NO 3 ) 3 9H 2 O.Ga(NO 3 ) 3 ·xH 2 O was dissolved in deionized water at a metal molar ratio of 3:1:0.24, and a deposition solution was obtained after ultrasonication at room temperature for 30 minutes. A two-electrode system was constructed with nickel foam as the cathode and anode and placed in the deposition solution. Electrodeposition was performed for one minute at an overall voltage of -1.2 V, and the NiFeGa-LDH catalyst was loaded on the nickel foam as the cathode, which was then rinsed with deionized water and dried naturally to obtain a NiFeGa-LDH electrode.

[0064] The deposition amount of NiFeGa-LDH catalyst is about 25 mg cm -2 , the electrode shape is square (side length is 200 mm) or circular (diameter is 200 mm).

[0065] Example 3

[0066] A tin-doped nickel-iron layered double hydroxide (NiFeSn-LDH) electrode comprises a nickel foam and a tin-doped nickel-iron layered double hydroxide (NiFeSn-LDH) catalyst deposited on the nickel foam. The preparation method comprises the following steps: The Ni(NO 3 )2 6H 2 O, Fe(NO 3 ) 3 9H 2 O、SnCl 4 ·4H 2 O was dissolved in deionized water at a metal molar ratio of 3:1:0.24, and a deposition solution was obtained after ultrasonication at room temperature for 30 minutes. A two-electrode system was constructed with nickel foam as the cathode and anode and placed in the deposition solution. Electrodeposition was performed for one minute at an overall voltage of -1.2 V, and the NiFeSn-LDH catalyst was loaded on the nickel foam as the cathode, which was then rinsed with deionized water and dried naturally to obtain a NiFeSn-LDH electrode.

[0067] The deposition amount of NiFeSn-LDH catalyst is about 25 mg cm -2 , the electrode shape is square (side length is 200 mm) or circular (diameter is 200 mm).

[0068] Example 4

[0069] An indium-doped nickel-iron layered double hydroxide (NiFeIn-LDH) electrode comprises a nickel foam and an indium-doped nickel-iron layered double hydroxide (NiFeIn-LDH) catalyst deposited on the nickel foam. The preparation method comprises the following steps: The Ni(NO 3 ) 2 6H 2 O, Fe(NO 3 ) 3 9H 2 O、InCl 3 ·4H 2 O was dissolved in deionized water at a metal molar ratio of 3:1:0.24, and a deposition solution was obtained after ultrasonication at room temperature for 30 minutes. A two-electrode system was constructed with nickel foam as the cathode and anode and placed in the deposition solution. Electrodeposition was performed for one minute at an overall voltage of -1.2 V, and the NiFeIn-LDH catalyst was loaded on the nickel foam as the cathode, which was then rinsed with deionized water and dried naturally to obtain a NiFeIn-LDH electrode.

[0070] The deposition amount of NiFeIn-LDH catalyst is about 25 mg cm -2 , the electrode shape is square (side length is 200 mm) or circular (diameter is 200 mm).

[0071] Example 5

[0072] An aluminum and gallium doped nickel iron layered double hydroxide (NiFeAlGa-LDH) electrode comprises a nickel foam and an aluminum and gallium doped nickel iron layered double hydroxide (NiFeAlGa-LDH) catalyst deposited on the nickel foam. The preparation method comprises the following steps: The Ni(NO 3 ) 2 6H 2 O, Fe(NO 3 ) 3 9H 2 O、AlCl 3 6H 2 O.Ga(NO 3 ) 3 ·xH 2 O was dissolved in deionized water at a metal molar ratio of 3:1:0.12:0.12, and a deposition solution was obtained after ultrasonication at room temperature for 30 minutes. A two-electrode system was constructed with nickel foam as the cathode and anode and placed in the deposition solution. Electrodeposition was performed for one minute at an overall voltage of -1.2 V, and the nickel foam as the cathode was loaded with NiFeAlGa-LDH catalyst, which was then rinsed with deionized water and dried naturally to obtain a NiFeAlGa-LDH electrode.

[0073] The deposition amount of NiFeAlGa-LDH catalyst is about 25 mg cm -2 , the electrode shape is square (side length is 200 mm) or circular (diameter is 200 mm).

[0074] Example 6

[0075] An aluminum-doped cobalt-iron layered double hydroxide (CoFeAl-LDH) electrode comprises a nickel foam and an aluminum-doped cobalt-iron layered double hydroxide (CoFeAl-LDH) catalyst deposited on the nickel foam. The preparation method comprises the following steps: Co(NO 3 ) 2 6H 2 O, Fe(NO 3 ) 3 9H 2 O、AlCl 3 6H 2O was dissolved in deionized water at a metal molar ratio of 3:1:0.24, and a deposition solution was obtained after ultrasonication at room temperature for 30 minutes. A two-electrode system was constructed with nickel foam as the cathode and anode and placed in the deposition solution. Electrodeposition was performed for one minute at an overall voltage of -1.2 V, and the nickel foam as the cathode was loaded with CoFeAl-LDH catalyst, which was then rinsed with deionized water and dried naturally to obtain a CoFeAl-LDH electrode.

[0076] The deposition amount of CoFeAl-LDH catalyst is about 25 mg cm -2 , the electrode shape is square (side length is 200 mm) or circular (diameter is 200 mm).

[0077] Example 7

[0078] An aluminum-doped nickel-cobalt-iron layered double hydroxide (NiCoFeAl-LDH) electrode comprises a nickel foam and an aluminum-doped nickel-cobalt-iron layered double hydroxide (NiCoFeAl-LDH) catalyst deposited on the nickel foam. The preparation method comprises the following steps: The Ni(NO 3 ) 2 6H 2 O、Co(NO 3 ) 2 6H 2 O, Fe(NO 3 ) 3 · 9H 2 O、AlCl 3 6H 2 O was dissolved in deionized water at a molar ratio of 2:1:1:0.24 with metals, and a deposition solution was obtained after ultrasonication at room temperature for 30 minutes. A two-electrode system was constructed with nickel foam as cathode and anode, and placed in the deposition solution. Electrodeposition was performed for one minute at an overall voltage of -1.2 V, and the nickel foam as the cathode was loaded with NiCoFeAl-LDH catalyst, which was then rinsed with deionized water and dried naturally to obtain a NiCoFeAl-LDH electrode.

[0079] The deposition amount of NiCoFeAl-LDH catalyst is about 25 mg cm -2 , the electrode shape is square (side length is 200 mm) or circular (diameter is 200 mm).

[0080] Example 8

[0081] An aluminum-doped iron-rich nickel-iron layered double hydroxide (Fe-rich NiFeAl-LDH) electrode comprises nickel foam and an aluminum-doped iron-rich nickel-iron layered double hydroxide (Fe-rich NiFeAl-LDH) catalyst deposited on the nickel foam, and a preparation method comprises the following steps: The Ni(NO 3 ) 2 6H 2 O, Fe(NO 3 ) 3 9H 2 O and AlCl 3 6H 2 O was dissolved in deionized water at a metal molar ratio of 1:3:0.24, and a deposition solution was obtained after ultrasonication at room temperature for 30 minutes. A two-electrode system was constructed with nickel foam as the cathode and anode and placed in the deposition solution. Electrodeposition was performed for one minute at an overall voltage of -1.2 V, and the Fe-rich NiFeAl-LDH catalyst was loaded on the nickel foam as the cathode, which was then rinsed with deionized water and dried naturally to obtain a Fe-rich NiFeAl-LDH electrode.

[0082] The deposition amount of Fe-rich NiFeAl-LDH catalyst is about 25 mg cm -2 , the electrode shape is square (side length is 200 mm) or circular (diameter is 200 mm).

[0083] Comparative Example 1

[0084] A nickel-iron layered double hydroxide (NiFe-LDH) electrode comprises nickel foam and a nickel-iron layered double hydroxide (NiFe-LDH) catalyst deposited on the nickel foam, and a preparation method comprises the following steps: The Ni(NO 3 ) 2 6H 2 O and Fe(NO 3 ) 3 9H 2 O was put into deionized water at a metal molar ratio of 3:1, and a deposition solution was obtained after ultrasonic treatment at room temperature for 30 minutes. A two-electrode system was constructed with a saturated calomel electrode as a reference electrode and nickel foam as a cathode and anode, and placed in the deposition solution. Electrodeposition was performed for one minute at an overall voltage of -1.2 V, and the nickel foam as the cathode was loaded with NiFe-LDH catalyst, which was then rinsed with deionized water and dried naturally to obtain a NiFe-LDH electrode.

[0085] The deposition amount of NiFe-LDH catalyst is about 25 mg cm-2 , the electrode shape is square (side length is 200 mm) or circular (diameter is 200 mm).

[0086] Comparative Example 2

[0087] A cobalt-iron layered double hydroxide (CoFe-LDH) electrode comprises nickel foam and a nickel-iron layered double hydroxide (CoFe-LDH) catalyst deposited on the nickel foam, and a preparation method comprises the following steps: Co(NO 3 ) 2 6H 2 O and Fe(NO 3 ) 3 9H 2 O was put into deionized water at a metal molar ratio of 3:1, and after ultrasonication at room temperature for 30 minutes, a deposition solution was obtained. A two-electrode system was constructed with nickel foam as the cathode and anode and placed in the deposition solution. Electrodeposition was performed for one minute at an overall voltage of -1.2 V, and the nickel foam as the cathode was loaded with CoFe-LDH catalyst, which was then rinsed with deionized water and dried naturally to obtain a CoFe-LDH electrode.

[0088] The deposition amount of CoFe-LDH catalyst is about 25 mg cm -2 , the electrode shape is square (side length is 200 mm) or circular (diameter is 200 mm).

[0089] Comparative Example 3

[0090] An Fe-rich NiFe-LDH electrode comprises a nickel foam and a Fe-rich NiFe-LDH catalyst deposited on the nickel foam. The preparation method comprises the following steps: The Ni(NO 3 ) 2 6H 2 O and Fe(NO 3 ) 3 9H 2 O was put into deionized water at a metal molar ratio of 1:3, and after ultrasonication at room temperature for 30 minutes, a deposition solution was obtained. A two-electrode system was constructed with nickel foam as cathode and anode and placed in the deposition solution. Electrodeposition was performed for one minute at an overall voltage of -1.2 V, and the nickel foam as the cathode was loaded with Fe-rich NiFe-LDH catalyst, which was then rinsed with deionized water and dried naturally to obtain a Fe-rich NiFe-LDH electrode.

[0091] The deposition amount of Fe-rich NiFe-LDH catalyst is about 25 mg cm -2 , the electrode shape is square (side length is 200 mm) or circular (diameter is 200 mm).

[0092] Test Example 1 In order to avoid the influence of nickel element contained in the nickel foam of the NiFeAl-LDH electrode of Example 1 on the tested NiFeAl-LDH catalyst, the deposition solution of Example 1 was electro-deposited on a fluorine-doped tin oxide (FTO) glass substrate, and the NiFeAl-LDH catalyst was tested by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) element mapping and spectrum. Specifically, the Ni(NO 3 ) 2 6H 2 O, Fe(NO 3 ) 3 9H 2 O and AlCl 3 6H 2 O was dissolved in deionized water at a metal molar ratio of 3:1:0.24, and a deposition solution was obtained after ultrasonication at room temperature for 30 minutes. A three-electrode system was constructed with a saturated calomel electrode as a reference electrode, an FTO glass substrate as a counter electrode, and an FTO glass substrate as a working electrode, and placed in the deposition solution. Electrodeposition was performed at a voltage of -1.2 V for one minute, and the NiFeAl-LDH catalyst was loaded on the FTO glass substrate as the working electrode. The test results are shown in Figure 3 As shown, a is the Ni element mapping diagram, b is the Fe element mapping diagram, c is the Al element mapping diagram, d is the O element mapping diagram, and e is the spectrum diagram. It can be seen that the Ni, Fe, and Al elements are evenly distributed, and the molar ratio is 1:0.33:0.08, which further confirms the successful preparation of the aluminum-doped nickel-iron layered double hydroxide (NiFeAl-LDH) catalyst.

[0093] The deposition solutions of Example 1 and Comparative Example 1 were subjected to the same electrodeposition conditions (a three-electrode system was constructed using a saturated calomel electrode as a reference electrode, an FTO glass substrate as a counter electrode, and an FTO glass substrate as a working electrode, placed in the deposition solution, and electrodeposited for one minute at a voltage of -1.2 V), and the catalyst was loaded on the FTO glass substrate. The X-ray diffraction (XRD) patterns of the NiFeAl-LDH catalyst of Example 1 and the NiFe-LDH catalyst of Comparative Example 1 were tested. The test results are shown in FIG. Figure 4 As shown in Figure 2, both catalysts present LDH phase. In addition, compared with the NiFe-LDH catalyst, the peak corresponding to the (003) plane of the LDH phase in the XRD pattern of the NiFeAl-LDH catalyst shifts toward a lower angle, proving the successful doping of Al.

[0094] Test Example 2 The p-region metal-doped layered double metal hydroxide electrodes of Examples 1-8 and the p-region metal-free layered double metal hydroxide electrode of Comparative Example 1 were subjected to water electrolysis test in an alkaline water electrolyzer. The test method is: The alkaline water electrolyzer comprises an anode, a cathode and an electrolyte. The anode is a p-region metal-doped layered double hydroxide electrode or a p-region metal-free layered double hydroxide electrode. The cathode is a nickel foam loaded with Pt / C. The electrolyte is a 1 M KOH aqueous solution. The operating temperature is 80°C.

[0095] Figure 5 The linear sweep voltammetry (LSV) curves of water electrolysis in alkaline water electrolyzers using the NiFeAl-LDH electrode of Example 1, the NiFeGa-LDH electrode of Example 2, the NiFeSn-LDH electrode of Example 3, the NiFeIn-LDH electrode of Example 4, and the NiFe-LDH electrode of Comparative Example 1 as anodes are shown in FIG. Figure 5 It can be seen that the NiFe-LDH electrode as the anode of the alkaline water electrolyzer can significantly improve the water electrolysis performance of the alkaline water electrolyzer after being doped with p-region metal; among them, the alkaline water electrolyzer with the NiFeAl-LDH electrode as the anode has the best performance.

[0096] The performance of the alkaline water electrolyzer with the NiFeAlGa-LDH electrode of Example 5 as the anode is better than that of the alkaline water electrolyzer with the NiFe-LDH electrode of Comparative Example 1 as the anode under the same conditions. The performance of the alkaline water electrolyzer with the CoFeAl-LDH electrode of Example 6 as the anode is better than that of the alkaline water electrolyzer with the CoFe-LDH electrode of Comparative Example 2 as the anode under the same conditions. The performance of the alkaline water electrolyzer with the Fe-rich NiFeAl-LDH electrode of Example 8 as the anode is better than that of the alkaline water electrolyzer with the Fe-rich NiFeAl-LDH electrode of Comparative Example 3 as the anode under the same conditions.

[0097] Test Example 3 The p-zone metal-doped layered double hydroxide electrodes of Examples 1-8 were subjected to water electrolysis tests in an AEM electrolyzer. The test method was as follows: AEM includes an anode, a cathode, an electrolyte and AEM. The anode is a layered double hydroxide electrode doped with a p-zone metal, the cathode is nickel foam loaded with Pt / C, the electrolyte is a 1 M KOH aqueous solution, and the operating temperature is 60 or 80 °C.

[0098] Figure 6The linear sweep voltammetry (LSV) curve of water electrolysis in an AEM electrolytic cell using the NiFeAl-LDH electrode of Example 1 as the anode. Figure 6 It can be seen that the AEM electrolytic cell with NiFeAl-LDH electrode as the anode can load high current density at a very low cell voltage. Especially at a high temperature of 80 °C, it only needs a cell voltage of 2.2 V to reach 5.4 A cm -2 The ultra-high current density far meets the requirements of industrial water electrolysis for hydrogen production, proving that the p-zone metal-doped layered double metal hydroxide electrode provided by the present invention has excellent practical application capabilities.

[0099] The AEM electrolytic cells using the p-zone metal-doped layered double metal hydroxide electrodes of Examples 2-8 as anodes all have excellent alkaline water electrolysis performance.

[0100] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art should understand that other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A p-zone metal-doped layered double hydroxide electrode, characterized in that: The p-region metal-doped layered double metal hydroxide electrode comprises a metal substrate and a p-region metal-doped layered double metal hydroxide catalyst deposited on the metal substrate; The p-zone metal-doped layered double metal hydroxide catalyst comprises a p-zone metal and a layered double metal hydroxide; the p-zone metal is selected from one or more of aluminum, gallium, tin and indium; the layered double metal hydroxide is a nickel-iron layered double metal hydroxide, a cobalt-iron layered double metal hydroxide or a nickel-cobalt-iron layered double metal hydroxide.

2. The p-zone metal-doped layered double hydroxide electrode according to claim 1, characterized in that: The molar amount of the p-zone metal is less than 30% of the molar amount of all metals in the p-zone metal-doped layered double metal hydroxide catalyst.

3. The p-zone metal-doped layered double hydroxide electrode according to claim 1, characterized in that: The molar amount of any metal in the layered double metal hydroxide accounts for more than 5% of the molar amount of all metals in the p-zone metal-doped layered double metal hydroxide catalyst.

4. A method for preparing a p-zone metal-doped layered double hydroxide electrode according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) dissolving a p-zone metal salt and an iron salt in water, and then adding a nickel salt and / or a cobalt salt to obtain a deposition solution; (2) placing a metal substrate in the deposition solution obtained in step (1), and electrodepositing a p-region metal-doped layered double metal hydroxide catalyst on the metal substrate by an electrodeposition method to prepare the p-region metal-doped layered double metal hydroxide electrode.

5. The preparation method according to claim 4, characterized in that: In step (2), the electrodeposition method adopts a three-electrode system or a two-electrode system, wherein the three-electrode system includes a reference electrode, a counter electrode and a working electrode, and the metal substrate is the working electrode; the two-electrode system includes a cathode and an anode, and the metal substrate is the cathode.

6. The preparation method according to claim 4, characterized in that In step (2), the deposition amount of the p-zone metal-doped layered double hydroxide catalyst on the metal substrate is 0.5-500 mg·cm -2 .

7. Use of the p-zone metal-doped layered double hydroxide electrode according to any one of claims 1 to 3 in an alkaline electrolytic cell.

8. The use according to claim 7, characterized in that: The alkaline electrolyzer comprises an alkaline water electrolyzer and an anion exchange membrane electrolyzer.

9. An alkaline electrolytic cell comprising an anode, a cathode and an electrolyte, characterized in that: The anode is the p-region metal-doped layered double hydroxide electrode as claimed in any one of claims 1 to 3.

10. Use of the p-zone metal-doped layered double hydroxide electrode according to any one of claims 1 to 3 or the alkaline electrolyzer according to claim 9 in hydrogen production by electrolysis of water.

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