Cerium-doped nickel-iron-based composite catalytic material, and preparation method and application thereof

Abstract

The present application relates to the field of hydrogen production by alkaline electrolysis of water, and discloses a cerium-doped nickel-iron-based composite catalytic material, a preparation method and application thereof.The cerium-doped nickel-iron-based composite catalytic material comprises a nickel foam substrate and a cerium-doped nickel-iron-based electrode layer coated on at least part of the nickel foam substrate.The mass ratio of cerium, nickel and iron in the cerium-doped nickel-iron-based electrode layer is 1:60-75:20-40.The average pore diameter of the cerium-doped nickel-iron-based electrode layer is 1-3 microns.The electrode layer of the cerium-doped nickel-iron-based composite catalytic material has an attenuation rate of less than or equal to 0.05 mV / h at 1000 h, and the amount of nickel element deposited is less than or equal to 2 micrograms per liter and the amount of iron element deposited is less than or equal to 100 micrograms per liter at 1000 h, thereby having excellent oxygen evolution activity and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydrogen production by alkaline electrolysis of water, in particular to a cerium-doped nickel-iron-based composite catalytic material and a preparation method and application thereof. BACKGROUND

[0002] Currently, the mainstream method of hydrogen production is through the reforming of fossil fuels, which produces a large amount of carbon emissions. Therefore, it is particularly urgent to develop sustainable hydrogen production technologies to meet the growing energy demand. Water electrolysis technology, which converts electrical energy into chemical energy, is an effective method for storing renewable energy. Coupling it with solar and wind power to produce hydrogen can effectively solve the instability problem of renewable energy generation. Common water electrolysis technologies include alkaline water electrolysis (ALK) and proton exchange membrane water electrolysis (PEMWE), as well as emerging anion exchange membrane water electrolysis (AEMWE). Among them, ALK has the longest development time and has been commercialized, but its low electrolysis efficiency and large ohmic resistance result in more energy consumption. PEMWE has a zero-gap structure and low ohmic resistance, which can achieve high current density, but it requires the use of low-abundance and expensive noble metal catalysts, limiting its large-scale application. AEMWE combines the advantages of ALK and PEMWE, which can achieve high current density and use non-noble metal catalysts, reducing the energy consumption and cost of water electrolysis for hydrogen production. However, the activity and stability of the AEMWE anode still need to be further improved.

[0003] CN101748426A discloses a preparation method of a foam electrode for water electrolysis. Foam nickel is selected as the substrate of the electrode material, the surface of the foam nickel is cleaned by removing oil stains, the foam nickel is soaked in a dilute acid solution for surface activation treatment, the activated foam nickel is rinsed with pure water, and then quickly immersed in an electrodeposition tank as a cathode for electrodeposition to prepare an active surface. The foam electrode with an active surface is thoroughly cleaned, then dried and heat treated. The foam material after heat treatment is cut to make an electrode material. The prior art can reduce the hydrogen evolution overpotential during electrolysis to some extent, reduce energy consumption and improve production efficiency. However, it has the defects of complex generation process and insufficient stability. SUMMARY

[0004] The purpose of the present application is to provide a composite catalytic material for alkaline water electrolysis with excellent activity and stability.

[0005] To achieve the above-mentioned purpose, the first aspect of the present application provides a cerium-doped nickel-iron-based composite catalytic material, which comprises: a foam nickel substrate, and a cerium-doped nickel-iron-based electrode layer coated on at least part of the foam nickel substrate.

[0006] The mass ratio of cerium elements, nickel elements and iron elements in the cerium-doped nickel-iron-based electrode layer is 1:60-75:20-40.

[0007] The average pore diameter of the cerium-doped nickel-iron-based electrode layer is 1-3 mu m; the attenuation rate of the cerium-doped nickel-iron-based electrode layer under 1000h is less than or equal to 0.05 mV / h, the deposition amount of nickel elements under 1000h is less than or equal to 2 mu g / L, and the deposition amount of iron elements under 1000h is less than or equal to 100 mu g / L.

[0008] The second aspect of the present application provides a method for preparing the cerium-doped nickel-iron-based composite catalytic material of the first aspect.

[0009] (1) In the presence of water, a nickel salt, a ferrous salt, cerium nitrate, citric acid, a conductive agent and a pH buffer are mixed to obtain an electroplating solution; in the electroplating solution, the concentration of the citric acid is 0.02-0.035 mol / L, and the concentration of cerium ions is 5-15 mmol / L;

[0010] (2) The foam nickel is immersed in the electroplating solution for electrodeposition treatment to obtain the cerium-doped nickel-iron-based composite catalytic material.

[0011] The third aspect of the present application provides an application of the cerium-doped nickel-iron-based composite catalytic material of the first aspect in water electrolysis hydrogen production.

[0012] The technical solution provided by the present application has at least the following advantages:

[0013] The cerium-doped nickel-iron-based composite catalytic material provided by the present application introduces cerium elements, improves the surface morphology of the cerium-doped nickel-iron-based electrode layer, has a porous structure on the surface, has rich active sites, and thus improves the activity. The cerium-doped nickel-iron-based electrode layer provided by the present application also has excellent stability, reduces the deposition of metal elements in the oxygen evolution process, and the cerium-doped nickel-iron-based electrode layer is firmly combined with the foam nickel substrate and is not easy to fall off.

[0014] In the preparation method of the cerium-doped nickel-iron-based composite catalytic material provided by the present application, the complexing effect of citric acid and cerium nitrate makes the electrode layer have a porous structure on the surface, has rich active sites, and thus improves the activity, and the electrode layer is firmly combined with the foam nickel substrate and can effectively prevent the electrode layer from falling off under a large current density. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a scanning electron microscope image of the composite catalytic material synthesized by using electroplating solutions with different concentrations of citric acid;

[0016] Figure 2 It is a scanning electron microscope image of the composite catalytic material synthesized by using electroplating solutions with different concentrations of Ce 3+ ;

[0017] Figure 3 is a scanning electron microscope image of the composite catalytic material synthesized using the plating solution with different electrodeposition times;

[0018] Figure 4 is a scanning electron microscope image of the composite catalytic material without doping of the cerium element;

[0019] Figure 5 is an X-ray diffraction analysis image of the composite catalytic material;

[0020] Figure 6 is a linear sweep voltammetry curve of the composite catalytic material synthesized using the plating solution with different citric acid concentrations;

[0021] Figure 7 is a linear sweep voltammetry curve of the composite catalytic material synthesized using the plating solution with different Ce 3+ concentrations;

[0022] Figure 8 is a linear sweep voltammetry curve of the composite catalytic material synthesized using the plating solution with different electrodeposition times;

[0023] Figure 9 is a linear sweep voltammetry curve of the foam nickel metal substrate without electrodeposition and the composite catalytic material;

[0024] Figure 10 is a chronoamperometric curve of the composite catalytic material without doping of the cerium element and the cerium-doped nickel-iron-based composite catalytic material;

[0025] Figure 11 is a scanning electron microscope image of the composite catalytic material after the stability test;

[0026] Figure 12 is a pore size analysis image of the composite catalytic material;

[0027] Figure 13 is an X-ray photoelectron spectroscopy of the composite catalytic material;

[0028] Figure 14 is a linear sweep voltammetry curve of the composite catalytic material of Example 1 and Comparative Example 5;

[0029] Figure 15 is a linear sweep voltammetry curve of the composite catalytic material of Example 1 and Comparative Example 6. DETAILED DESCRIPTION

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] The average aperture mentioned in this invention refers to the average aperture diameter.

[0032] As mentioned above, a first aspect of the present invention provides a cerium-doped nickel-iron-based composite catalytic material, the cerium-doped nickel-iron-based composite catalytic material comprising: a nickel foam substrate, and a cerium-doped nickel-iron-based electrode layer coated on at least a portion of the nickel foam substrate;

[0033] The mass ratio of cerium, nickel and iron in the cerium-doped nickel-iron-based electrode layer is 1:60-75:20-40.

[0034] The average pore size of the cerium-doped nickel-iron-based electrode layer is 1-3 μm; the decay rate of the cerium-doped nickel-iron-based electrode layer is ≤0.05 mV / h over 1000 h, and the amount of nickel deposited is ≤2 μg / L and the amount of iron deposited is ≤100 μg / L over 1000 h.

[0035] The cerium-doped nickel-iron-based composite catalytic material provided by this invention has excellent activity and stability, and is not prone to metal component dissolution or electrode catalyst layer detachment under alkaline oxygen evolution conditions.

[0036] In a preferred embodiment, in the cerium-doped nickel-iron-based composite catalytic material provided by the present invention, the cerium-doped nickel-iron-based electrode layer is coated on all the nickel foam substrates.

[0037] Preferably, the thickness of the cerium-doped nickel-iron-based electrode layer is 5-20 μm.

[0038] Preferably, based on the total mass of the cerium-doped nickel-iron-based electrode layer, the sum of the contents of cerium, nickel, and iron is 70-90 wt%.

[0039] Preferably, the cerium-doped nickel-iron-based electrode layer is at 100 mA·cm⁻¹ -2 The overpotential is ≤300mV, preferably ≤290mV, more preferably ≤285mV, and especially preferably ≤280mV.

[0040] Preferably, the areal density of the nickel foam is 300-400 g / m³. 2 The porosity is 75-98%.

[0041] As described above, the second aspect of the present application provides a method for preparing the cerium-doped nickel-iron-based composite catalytic material of the aforementioned first aspect, which comprises:

[0042] (1) contacting and mixing a nickel salt, a ferrous salt, cerium nitrate, citric acid, a conductive agent and a pH buffer in the presence of water to obtain an electroplating solution; in the electroplating solution, the concentration of the citric acid is 0.02-0.035 mol / L, and the concentration of cerium ions is 5-15 mmol / L;

[0043] (2) immersing the foamed nickel in the electroplating solution for electrodeposition treatment to obtain the cerium-doped nickel-iron-based composite catalytic material.

[0044] In the present application, cerium nitrate is specifically selected as the source of cerium element, and the inventors have found that this technical feature can make the cerium-doped nickel-iron-based composite catalytic material have more excellent activity and stability, reduce the deposition rate of metal elements, and improve the oxygen evolution activity. In addition, the combined effect of citric acid and cerium element makes the surface of the electrode layer have a porous structure, so that it has abundant active sites, thereby improving the activity, and the electrode layer is firmly combined with the foamed nickel substrate, which can effectively prevent the electrode layer from falling off under a large current density.

[0045] In the present application, a ferrous salt is used in the electroplating solution, which has the advantages of lower overpotential and better stability compared to trivalent iron ions, thereby obtaining a cerium-doped nickel-iron-based composite catalytic material with higher activity and stability.

[0046] Preferably, in the electroplating solution, the molar concentration ratio of cerium ions, nickel ions and ferrous ions is 1:6-20:6-20, more preferably 1:10-20:10-20.

[0047] Preferably, in the electroplating solution, the concentration of nickel ions is 0.05-0.2 mol / L, preferably 0.08-0.12 mol / L; the concentration of ferrous ions is 0.05-0.2 mol / L, preferably 0.08-0.12 mol / L; and the concentration of cerium ions is 5-10 mmol / L.

[0048] Preferably, in the electroplating solution, the concentration of the citric acid is 0.02-0.025 mol / L.

[0049] Preferably, in the electroplating solution, the concentration of the conductive agent is 0.5-1.5 mol / L.

[0050] Preferably, in the electroplating solution, the concentration of the pH buffer is 0.2-0.5 mol / L.

[0051] Preferably, the nickel salt is nickel sulfate and / or nickel chloride.

[0052] Preferably, the ferrous salt is ferrous sulfate and / or ferrous ammonium sulfate.

[0053] Preferably, the conductive agent is at least one of ammonium chloride, ammonium sulfate, potassium sulfate, sodium chloride; preferably ammonium chloride and / or ammonium sulfate.

[0054] Preferably, the pH buffer is at least one of boric acid, phosphoric acid, oxalic acid; preferably boric acid.

[0055] The form of the nickel salt, the ferrous salt, the cerium nitrate, and the citric acid can be a hydrated form or a non-hydrated form, and the amount of combined water is not particularly limited, and water and compounds known in the art can be used, for example, nickel sulfate hexahydrate, ferrous sulfate heptahydrate, cerium nitrate hexahydrate, and citric acid monohydrate. The present application does not limit the present application again, and those skilled in the art should not be construed as limiting the present application.

[0056] Preferably, the time of the electrodeposition treatment is 10-20 min.

[0057] According to a particularly preferred embodiment of the present application, the operation of the electrodeposition treatment comprises:

[0058] The nickel foam is used as a working electrode, and a graphite sheet is used as a counter electrode, and a two-electrode system is used for constant current deposition at a current density of 25-75 mA·cm -2 for 10-20 min to obtain the cerium-doped nickel-iron-based composite catalytic material.

[0059] Preferably, the nickel foam is in the form of a sheet, and the volume of the plating solution is 0.1-0.2 L relative to the nickel foam of 4 cm 2 in area. It should be noted that the area of the nickel foam here refers to the area of a single side.

[0060] The nickel foam of the present application can be a regular sheet or an irregular sheet, and those skilled in the art can tailor it into any shape according to actual needs. The present application does not limit the present application again, and those skilled in the art should not be construed as limiting the present application.

[0061] According to a preferred embodiment, the method further comprises sequentially subjecting the nickel foam to oil removal treatment and surface activation treatment, and then subjecting the pretreated nickel foam to the electrodeposition treatment.

[0062] In some embodiments, the operation of the oil removal treatment comprises: ultrasonic cleaning the nickel foam in an organic solvent for 20-40 min.

[0063] Preferably, the organic solvent is selected from at least one of acetone, petroleum ether, ethyl acetate.

[0064] In some embodiments, the surface activation treatment operation comprises: soaking the oil-stripped foamed nickel in acid solution for 20-40 min under ultrasonic treatment to obtain the pretreated foamed nickel.

[0065] Preferably, the acid solution is selected from at least one of hydrochloric acid solution and sulfuric acid solution.

[0066] According to a particularly preferred embodiment, before the oil-stripped foamed nickel is subjected to the oil-stripped treatment, the foamed nickel is subjected to a rolling treatment so that the surface density is 300-400 g / m 2 .

[0067] The method of the present application can further comprise conventional post-treatment means such as washing, drying, etc. in the art, which can be selected by those skilled in the art according to the technical means known in the art. The present application exemplarily provides a preferred embodiment hereinafter, which should not be understood as a limitation of the present application.

[0068] As described previously, the third aspect of the present application provides an application of the cerium-doped nickel-iron-based composite catalytic material of the aforementioned first aspect in the electrolysis of water to produce hydrogen.

[0069] The present application will be described in detail below by way of examples. In the following examples, the raw materials are all commercially available unless otherwise specified.

[0070] Foamed nickel: purchased from Kunshan Guangjiayuan New Material Co., Ltd.

[0071] In the following examples, the foamed nickel is pretreated by the following method unless otherwise specified.

[0072] Commercial foamed nickel is rolled to 270 μm (surface density of 300-400 g / m 2 ), and then cut into a size of 2 cm x 2 cm. The cut foamed nickel is ultrasonically cleaned in acetone for 30 min to remove surface oil stains, and the cleaned foamed nickel is naturally air-dried. The dried foamed nickel is ultrasonically cleaned in 3 mol / L hydrochloric acid for 30 min to remove the surface oxide layer, and the cleaned foamed nickel is washed with deionized water for 3 times and then with anhydrous ethanol for 3 times to remove residual hydrochloric acid on the surface, and then naturally air-dried to obtain the pretreated foamed nickel (NF).

[0073] Example 1

[0074] (1) Dissolve nickel sulfate hexahydrate, ferrous sulfate heptahydrate, cerium nitrate hexahydrate, ammonium chloride, boric acid and citric acid monohydrate in deionized water, uniformly mix to obtain a green transparent solution, which is the electroplating solution;

[0075] In the electroplating solution, the concentration of nickel ions is 0.1 mol / L, the concentration of ferrous ions is 0.1 mol / L, the concentration of cerium ions is 5 mmol / L, the concentration of citric acid monohydrate is 0.025 mol / L, the concentration of ammonium chloride is 1 mol / L, and the concentration of boric acid is 0.4 mol / L;

[0076] (2) Take the pretreated foamed nickel as a working electrode and a graphite sheet as a counter electrode, immerse them in 0.1 L of the electroplating solution to form a two-electrode system, and deposit at a constant current of -50 mA·cm -2 -2 under the current density of -50 mA·cm 0.05 -2.5-10mins / NF), the average pore size of the cerium-doped nickel-iron-based composite catalytic material is 1-3 μm, the sum of the contents of cerium, nickel and iron elements in the electrode layer is 85 wt%, and the mass ratio of cerium, nickel and iron elements is 1:69:29.

[0077] Example 2

[0078] The similar process as in Example 1 is adopted, except that the concentration of citric acid monohydrate is adjusted to 0.02 mol / L, and the rest remains unchanged, to prepare a cerium-doped nickel-iron-based composite catalytic material (named as NiFeCe 0.05 -2-10mins / NF).

[0079] Example 3

[0080] The similar process as in Example 1 is adopted, except that the concentration of citric acid monohydrate is adjusted to 0.03 mol / L, and the rest remains unchanged, to prepare a cerium-doped nickel-iron-based composite catalytic material (named as NiFeCe 0.05 -3-10mins / NF).

[0081] Example 4

[0082] The similar process as in Example 1 is adopted, except that the concentration of citric acid monohydrate is adjusted to 0.035 mol / L, and the rest remains unchanged, to prepare a cerium-doped nickel-iron-based composite catalytic material (named as NiFeCe 0.05 -3.5-10mins / NF).

[0083] Example 5

[0084] The similar procedure of Example 1 was adopted, except that the amount of cerium nitrate hexahydrate was adjusted so that the concentration of cerium ions in the electroplating solution was 10 mmol / L, and the concentrations of the other metal ions remained unchanged; a cerium-doped nickel-iron-based composite catalytic material (named NiFeCe 0.1 -2.5-10mins / NF).

[0085] Example 6

[0086] The similar procedure of Example 1 was adopted, except that the electrodepositing time was adjusted to 15 mins; the rest remained unchanged, and a cerium-doped nickel-iron-based composite catalytic material (named NiFeCe 0.05 -2.5-15mins / NF).

[0087] Example 7

[0088] The similar procedure of Example 1 was adopted, except that the electrodepositing time was adjusted to 20 mins; the rest remained unchanged, and a cerium-doped nickel-iron-based composite catalytic material (named NiFeCe 0.05 -2.5-20mins / NF).

[0089] Comparative Example 1

[0090] The similar procedure of Example 1 was adopted, except that the concentration of citric acid monohydrate was adjusted to 0.01 mol / L; the rest remained unchanged, and a cerium-doped nickel-iron-based composite catalytic material (named NiFeCe 0.05 -1-10mins / NF).

[0091] Comparative Example 2

[0092] The similar procedure of Example 1 was adopted, except that the concentration of citric acid monohydrate was adjusted to 0.015 mol / L; the rest remained unchanged, and a cerium-doped nickel-iron-based composite catalytic material (named NiFeCe 0.05 -1.5-10mins / NF).

[0093] Comparative Example 3

[0094] The similar procedure of Example 1 was adopted, except that the amount of cerium nitrate hexahydrate was adjusted so that the concentration of cerium ions in the electroplating solution was 20 mmol / L, and the concentrations of the other metal ions remained unchanged; a cerium-doped nickel-iron-based composite catalytic material (named NiFeCe 0.2 -2.5-10mins / NF).

[0095] Comparative Example 4

[0096] The similar procedure of Example 1 was adopted, except that no cerium nitrate hexahydrate was added in the plating solution in step (1), and the rest remained unchanged, to prepare a nickel-iron-based composite catalytic material (named as NiFe / NF).

[0097] Comparative Example 5

[0098] The similar procedure of Example 1 was adopted, except that the ferrous sulfate heptahydrate in step (1) was replaced by ferric nitrate nonahydrate (chemical formula Fe(NO3)3·9H2O) to keep the concentration of iron ions in the plating solution unchanged; to prepare a cerium-doped nickel-iron-based composite catalytic material (named as NiFeCe 0.05 -Fe(NO3)3·9H2O / NF).

[0099] Comparative Example 6

[0100] The similar procedure of Example 1 was adopted, except that no citric acid monohydrate was used in step (1), that is, no citric acid was contained in the plating solution; the rest remained unchanged; to prepare a cerium-doped nickel-iron-based composite catalytic material (NiFeCe 0.05 -no citric acid / NF).

[0101] Test Example 1

[0102] The composite catalytic materials synthesized by using plating solutions with different citric acid concentrations (Example 1 to Example 4, Comparative Example 1 to Comparative Example 2) were subjected to scanning electron microscope analysis, and the surface morphology thereof is shown in Figure 1 From the figure, it can be seen that the surface electrode catalytic layer of the cerium-doped nickel-iron-based composite catalytic material provided by the present application has more excellent pore distribution and size.

[0103] The composite catalytic materials synthesized by using plating solutions with different Ce 3+ concentrations (Example 1, Example 5 and Comparative Example 3) were subjected to scanning electron microscope analysis, and the surface morphology thereof is shown in Figure 2 From the figure, it can be seen that the surface electrode catalytic layer of the cerium-doped nickel-iron-based composite catalytic material provided by the present application is porous, and the pore size distribution and porosity are moderate. The surface electrode catalytic layer of the cerium-doped nickel-iron-based composite catalytic material obtained without using the scheme of the present application is changed from a porous structure to a nano-particle, and gradually agglomerates.

[0104] The composite catalytic materials synthesized by using different electrodeposition times (Example 1, Example 6 and Example 7) were subjected to scanning electron microscope analysis, and the surface morphology thereof is shown in Figure 3 From the figure, it can be seen that the cerium-doped nickel-iron-based composite catalytic material provided by the present application has a porous structure, and the pores are uniformly distributed with moderate pore size.

[0105] The scanning electron microscope analysis of the composite catalytic material without doping cerium element (Comparative Example 4) was carried out, and the surface morphology thereof is shown in Figure 4 From the figure, it can be seen that, compared with the sample with cerium element doping, the NiFe / NF catalytic layer surface has no porous structure, and the surface active site will be reduced, which is not conducive to the improvement of oxygen evolution activity.

[0106] The pore size analysis of the composite catalytic material obtained in Example 1 was carried out, and the results are shown in Figure 12 From the figure, it can be seen that the pore size of the electrode layer of the composite catalytic material is mostly about 1 μm.

[0107] Test Example 2

[0108] The electrode layer of the composite catalytic material obtained in Example 1 (NiFeCe 0.05 -2.5-10mins) and Comparative Example 4 (NiFe / NF) was subjected to X-ray diffraction (XRD) analysis, and the results are shown in Figure 5 The XRD data show that the composition of the electrode layer is mainly an alloy phase material of Ni and Fe, wherein the diffraction peaks at 44.5°, 51.8° and 76.4° belong to the (111), (200) and (220) crystal faces of Ni, and the diffraction peaks at 44.7°, 65.0° and 82.3° belong to the (110), (200) and (211) crystal faces of Fe.

[0109] Figure 13 The X-ray photoelectron spectroscopy of the composite catalytic material (Example 1) is shown in Figure 8; the NiFeCe 0.05 -2.5-10mins / NF sample Ni 2p orbit analysis shows that the characteristic peak at the binding energy of 852.5 eV belongs to Ni 0 , and the characteristic peak at 855.8 eV belongs to Ni 2+ , and the binding energy is shifted to a lower direction compared with NiFe / NF, proving that the valence state of Ni is lower than that of NiFe / NF. The Fe 2p orbit XPS analysis shows that the characteristic peak at the binding energy of 707 eV belongs to Fe 0 , and the characteristic peak at 711.1 eV belongs to Fe 2+ , and the binding energy is shifted to a lower direction compared with NiFe / NF, proving that the valence state of Ni is lower than that of NiFe / NF. The Ce 3d orbit shows that the characteristic peaks at 879.5 eV and 885.4 eV belong to Ce 3+ , and the characteristic peaks at 882.2 eV and 887.4 eV belong to Ce 4+ .

[0110] Test Example 3

[0111] Activity and stability test of the composite catalytic material: 1 mol / L potassium hydroxide solution was prepared as a test electrolyte, the prepared composite catalytic material sample was used as a working electrode, a graphite electrode was used as a counter electrode, and a saturated calomel electrode was used as a reference electrode, and the three electrodes were fully immersed in the prepared electrolyte to form a three-electrode system. The linear sweep voltammetry method was used to determine the catalytic activity of oxygen evolution reaction, and the chronopotentiometry method was used to determine the catalytic stability of oxygen evolution reaction.

[0112] Figure 6 The linear sweep voltammograms of the composite catalytic materials synthesized by using the electroplating solutions with different citric acid concentrations (Examples 1 to 4, Comparative Examples 1 to 2) are shown in the figure. It can be seen from the figure that the cerium-doped nickel-iron-based composite catalytic material provided by the application has high oxygen evolution activity.

[0113] Figure 7 The linear sweep voltammograms of the composite catalytic materials synthesized by using the electroplating solutions with different Ce 3+ concentrations (Examples 1, 5, Comparative Examples 3 and 4) are shown in the figure. It can be seen from the figure that the introduction of the cerium element can effectively improve the active sites on the surface of the catalytic layer, thereby improving the activity. In particular, the oxygen evolution activity of Example 1 (NiFeCe 0.05 -2.5-10mins / NF) is the highest, reaching 100 mA·cm -2 The overpotential required for a current density of 100 mA·cm is 1.505 V (relative to the reversible hydrogen electrode RHE).

[0114] Figure 8 The linear sweep voltammograms of the composite catalytic materials synthesized by using different electrodeposition times (Examples 1, 6, and 7) are shown in the figure. It can be seen from the figure that the cerium-doped nickel-iron-based composite catalytic material provided by the application has excellent oxygen evolution activity.

[0115] Figure 9 The linear sweep voltammograms of the nickel foam metal substrate (NF) without electrodeposition and the composite catalytic material (Example 1) are shown in the figure. It can be found that compared with other different examples, the activity of NF is the worst, and the overpotential is as high as 383 mV at a current density of 100 mA·cm -2 .

[0116] Figure 10 The chronopotentiometry curves of the composite catalytic material without doping cerium element (Comparative Example 4) and the cerium-doped nickel-iron-based composite catalytic material (Example 1) are shown in the figure. The electrodeposition time is 10 mins, and the chronopotentiometry curve at a current density of 200 mA·cm -2 is compared. It is found that the NiFeCe 0.05-2.5-10mins / NF only increased 40mV, while NiFe / NF increased 11mV after 130h, and the decay rate of NiFeCe 0.05 -2.5-10mins / NF only increased 40mV, while NiFe / NF increased 11mV after 130h, and the decay rate of NiFeCe

[0117] Figure 11 are scanning electron microscope images of the composite catalytic materials of Example 1 and Comparative Example 4 after stability test, wherein NiFeCe 0.05 -2.5-10mins / NF at 200mA·cm -2 After 1000h test, the electrode layer did not fall off, and the pore size structure of the electrode layer surface was well preserved. It shows that the composite catalytic material provided by the application has high mechanical stability, and the structure of the electrode catalytic layer is not easy to be damaged and is firmly combined with the nickel foam metal substrate, showing good stability. The NiFe / NF sample has serious agglomeration of the nanoparticles on the surface of the catalytic layer, and the catalytic layer is thinned, and the outline of the nickel foam metal substrate is clearly visible.

[0118] Figure 14 are linear sweep voltammetry curves of Example 1 and Comparative Example 5; it can be found that the sample OER activity will be poor when Fe 3+ is contained in the plating solution, and the overpotential is as high as 318mV at a current density of 100mA·cm -2 .

[0119] Figure 15 are linear sweep voltammetry curves of Example 1 and Comparative Example 6; it can be found that the sample OER activity will be poor when citric acid is not contained in the plating solution, and the overpotential is as high as 312mV at a current density of 100mA·cm -2 .

[0120] Test Example 4

[0121] The thickness of the electrode layer of the composite catalytic material prepared in each of the foregoing examples and comparative examples is shown in Table 1.

[0122] After the chronopotentiometric test of the composite catalytic material, the content of the metal element precipitated from the electrolyte is tested. The test method is: a high-frequency inductively coupled plasma is used as an excitation light source to excite gaseous atoms or ions in the sample substance. The characteristic radiation energy emitted during the return of the excited outer electrons to the ground state is captured, and the energy information of the standard sample at different contents is compared to obtain the content of the measured element. The application exemplarily provides the data of the content of the metal element precipitated from the electrolyte after the chronopotentiometric test of the composite catalytic material of Example 1 and Comparative Example 4, which is shown in Table 2.

[0123] The overpotential and decay rate of the composite catalytic material prepared in each of the foregoing examples and comparative examples were tested.

[0124] The overpotential test method is as follows: in actual oxygen evolution half-reaction electrochemical performance testing, the measured potential will have a certain difference from the theoretical thermodynamic electrode potential, and this difference is the overpotential. Under the same anode current density, the smaller the overpotential, the higher the OER catalytic activity of the sample. The oxygen evolution activity was tested by linear sweep voltammetry to obtain the potential at 100mA cm -2 -2 under the current density, which is subtracted from the theoretical thermodynamic OER electrode potential, i.e. 1.23V, to obtain the OER overpotential at 100mA cm -2 -2. The results are shown in Table 3.

[0125] The decay rate test method is to use chronopotentiometry to charge at 200mA cm -2 -2, and the value of the overpotential increase is divided by the time to obtain the decay rate.

[0126] The composite catalytic material prepared by the technical scheme provided in the present application has excellent activity and stability. The decay rate of the composite catalytic material of Example 1 is 0.04mV / h, while the decay rates of the composite catalytic materials of Comparative Example 3 and Comparative Example 4 are 0.57mV / h and 0.085mV / h respectively, and the stability is significantly poorer.

[0127] Table 1

[0128] Composite catalytic material designation Thickness of electrode layer (pm) Example 1 NiFeCe 0.05 -2.5-10 mins / NF 10 Example 2 NiFeCe 0.05 -2-10 mins / NF 10 Example 3 NiFeCe 0.05 -3-10 mins / NF 10 Example 4 NiFeCe 0.05 -3.5-10 mins / NF 10 Example 5 NiFeCe 0.1 -2.5-10 mins / NF 10 Example 6 NiFeCe 0.05 -2.5-15 mins / NF 12 Example 7 NiFeCe 0.05 -2.5-20 mins / NF 14 Comparative Example 1 NiFeCe 0.05 -1-10 mins / NF 10 Comparative Example 2 NiFeCe 0.05 -1.5-10 mins / NF 10 Comparative Example 3 NiFeCe 0.2 -2.5-10 mins / NF 10 Comparative Example 4 NiFe / NF 10

[0129] Table 2

[0130]

[0131] Table 3

[0132] Composite catalytic material designation 100 mA-cm -2 Under-potential (mV) Example 1 NiFeCe 0.05 -2.5-10 mins / NF 275 Example 3 NiFeCe 0.05 -3-10 mins / NF 281 Example 4 NiFeCe 0.05 -3.5-10 mins / NF 295 Example 5 NiFeCe 0.1 -2.5-10 mins / NF 279 Example 6 NiFeCe 0.05 -2.5-15 mins / NF 292 Example 7 NiFeCe 0.05 -2.5-20 mins / NF 286 Comparative Example 3 NiFeCe 0.2 -2.5-10 mins / NF 294 Comparative Example 4 NiFe / NF 298 Comparative Example 5 NiFeCe 0.05 - Fe(NO3)3·9H2O / NF 318 Comparative Example 6 NiFeCe 0.05 - no citric acid / NF 312 Pretreated nickel foam NF 383

[0133] As can be seen from the above results, the cerium-doped nickel-iron-based electrode layer provided in the present application also has excellent activity and stability, reduces the deposition of metal elements during oxygen evolution, and is firmly combined with the nickel foam substrate and is not easy to fall off.

[0134] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical scheme of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed in the present application and fall within the protection scope of the present application.

Claims

1. A cerium-doped nickel-iron-based composite catalytic material, characterized in that, The cerium-doped nickel-iron-based composite catalytic material comprises a nickel foam substrate and a cerium-doped nickel-iron-based electrode layer coated on at least part of the nickel foam substrate; The mass ratio of cerium, nickel and iron in the cerium-doped nickel-iron-based electrode layer is 1:60-75:20-40; The average pore size of the cerium-doped nickel-iron-based electrode layer is 1-3 μm; the decay rate of the cerium-doped nickel-iron-based electrode layer is ≤0.05 mV / h after 1000 h, the amount of nickel element deposited is ≤2 μg / L after 1000 h, and the amount of iron element deposited is ≤100 μg / L after 1000 h; The cerium-doped nickel-iron-based composite catalytic material is prepared by the following method: (1) In the presence of water, a nickel salt, a ferrous salt, cerium nitrate, citric acid, a conductive agent and a pH buffer are mixed to obtain an electroplating solution; in the electroplating solution, the concentration of citric acid is 0.02-0.035 mol / L, and the concentration of cerium ions is 5-15 mmol / L; (2) The nickel foam is immersed in the electroplating solution for electrodeposition treatment to obtain the cerium-doped nickel-iron-based composite catalytic material.

2. The cerium-doped nickel-iron-based composite catalytic material of claim 1, wherein, The thickness of the cerium-doped nickel-iron-based electrode layer is 5-20 μm; And / or, based on the total mass of the cerium-doped nickel-iron-based electrode layer, the total content of cerium, nickel and iron is 70-90 wt%.

3. The cerium-doped nickel-iron-based composite catalytic material according to claim 1 or 2, characterized in that The cerium-doped nickel-iron-based electrode layer has a capacity of at least 300 mAh·g -2 The overpotential is less than 300 mV.

4. A process for the preparation of the cerium-doped nickel-iron-based composite catalytic material according to any one of claims 1 to 3, characterized in that, The method comprises: (1) In the presence of water, a nickel salt, a ferrous salt, cerium nitrate, citric acid, a conductive agent and a pH buffer are mixed to obtain an electroplating solution; in the electroplating solution, the concentration of citric acid is 0.02-0.035 mol / L, and the concentration of cerium ions is 5-15 mmol / L; (2) The nickel foam is immersed in the electroplating solution for electrodeposition treatment to obtain the cerium-doped nickel-iron-based composite catalytic material.

5. The method of claim 4, wherein, In the electroplating solution, the concentration of nickel ions is 0.05-0.2 mol / L, and the concentration of ferrous ions is 0.05-0.2 mol / L; And / or, in the electroplating solution, the molar concentration ratio of cerium ions, nickel ions and ferrous ions is 1:6-20:6-20; And / or, in the electroplating solution, the concentration of citric acid is 0.02-0.025 mol / L; And / or, in the electroplating solution, the concentration of the conductive agent is 0.5-1.5 mol / L; And / or, in the electroplating solution, the concentration of the pH buffer is 0.2-0.5 mol / L.

6. The method of claim 4, wherein, The nickel salt is nickel sulfate and / or nickel chloride; And / or, the ferrous salt is ferrous sulfate and / or ferrous ammonium sulfate.

7. The method of claim 4, wherein, The conductive agent is selected from at least one of ammonium chloride, ammonium sulfate, potassium sulfate and sodium chloride; And / or, the pH buffer is selected from at least one of boric acid, phosphoric acid and oxalic acid.

8. The method of claim 4, wherein, The electrodeposition treatment time is 10-20 min; and / or, relative to the 4 cm 2 The volume of the electroplating solution is 0.1-0.2 L relative to the 4 cm 9. The method according to any one of claims 4-8, characterized in that, The method further comprises: first, sequentially performing oil removal treatment and surface activation treatment on the nickel foam, and then performing the electrodeposition treatment on the pretreated nickel foam.

10. The cerium-doped nickel-iron-based composite catalytic material according to any one of claims 1-3 is used in the electrolysis of water to produce hydrogen.

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