Method for preparing iron-nickel-molybdenum electrocatalyst through combination of electrodeposition and rapid Joule heat and application of iron-nickel-molybdenum electrocatalyst

Abstract

The invention discloses a method for preparing an iron-nickel-molybdenum-based electrocatalyst through combination of electrodeposition and rapid Joule heat and application of the method. The method comprises the steps that S1, a porous nickel substrate is pretreated, and the pretreated porous nickel substrate is obtained; s2, obtaining a nickel salt solution, a molybdenum salt solution and a ferric salt solution; s3, obtaining a mixed solution; s4, putting the mixed solution serving as electrolyte into a dual-electrode electrolytic tank, carrying out electro-deposition treatment by taking the pretreated porous nickel substrate as a cathode and an inert electrode as an anode, and washing and drying to obtain a Fe-Ni-Mo-LDH precursor; and S5, carrying out Joule thermal pyrolysis treatment on the Fe-Ni-Mo-LDH precursor, so as to obtain the iron-nickel-molybdenum based electrocatalyst. The preparation method can effectively regulate and control the size structure of the catalyst, and is suitable for preparing iron-nickel-molybdenum-based electrocatalysts with different substrates and different sizes; and the electrocatalyst has the advantages of uniform and stable nanostructure and high loading capacity. Meanwhile, the preparation method is short in reaction time, high in heating efficiency, high in repeatability and suitable for industrial large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysts, and particularly relates to a method for preparing an iron-nickel-molybdenum electrocatalyst by combining electrodeposition and rapid Joule heating and its application. Background Art

[0002] With the rapid development of renewable energy and the urgent demand for clean energy, hydrogen (H2), as an ideal energy carrier, has received extensive attention. Seawater electrolysis is a promising technology for large-scale production of H2.

[0003] Currently, hydrothermal synthesis is commonly used to prepare catalysts. Although this method has the advantages of high product purity, good dispersion, and easy control of particle size, it usually needs to be carried out at high temperature and pressure, which may lead to high energy consumption and thus increase the preparation cost. Moreover, the hydrothermal synthesis method is usually carried out in a closed autoclave, there is a risk of explosion or leakage. If the temperature is not properly controlled or the seal fails during the reaction process, the reaction kettle may burst. At the same time, this method requires special hydrothermal synthesis equipment, which increases the complexity of experimental equipment and maintenance cost, and cannot meet the needs of large-scale production.

[0004] The electrodeposition method has the advantages of mild conditions, simple operation, less time-consuming, and low energy consumption. By changing the composition of the electrolyte, the magnitude of voltage / current, and the deposition time, the morphology of the catalyst can be accurately regulated, and the electrodeposition method is conducive to large-scale production. At the same time, the existing high-temperature tube furnace and muffle furnace processes require long-time heating and cooling, which easily leads to an increase in the size of catalyst particles and a complex production process with high energy consumption. Joule heating can quickly reach a high temperature and shorten the synthesis time, thereby improving the catalytic performance. Moreover, the rapid Joule heating method has the advantages of simple regulation and low energy consumption. The discharge voltage and current can be controlled by changing the capacitor charging time, which is suitable for occasions that require rapid heating and cooling. Through the preforming of electrodeposited precursors and the instantaneous alloying of rapid Joule heating, the low-cost preparation of large-area, highly uniform, and highly active catalysts can be realized, providing certain technical support for large-scale production. Summary of the Invention

[0005] The present invention discloses a method for preparing an iron-nickel-molybdenum-based electrocatalyst by combining electrodeposition and rapid Joule heating and its application. This preparation method can effectively regulate the size and structure of the catalyst, is suitable for preparing iron-nickel-molybdenum-based electrocatalysts with different substrates and different sizes, and the prepared electrocatalyst has the advantages of a uniform and stable nanostructure and high-loading loading. At the same time, this preparation method has a short reaction time, high heating efficiency, and strong repeatability, and is suitable for industrial large-scale production.

[0006] The first object of the present invention is to provide a method for preparing an iron-nickel-molybdenum-based electrocatalyst by combining electrodeposition and rapid Joule heating, and this method includes:

[0007] S1 Pretreat the porous nickel substrate to obtain a pretreated porous nickel substrate;

[0008] S2 Dissolve nickel salt, molybdenum salt and iron salt in deionized water respectively to obtain a nickel salt solution, a molybdenum salt solution and an iron salt solution;

[0009] S3 Mix and stir the nickel salt solution, molybdenum salt solution and iron salt solution evenly to obtain a mixed solution;

[0010] S4 Place the mixed solution as an electrolyte in a two-electrode electrolytic cell, use the pretreated porous nickel substrate as the cathode and an inert electrode as the anode for electrodeposition treatment, and then wash and dry to obtain a Fe-Ni-Mo-LDH precursor;

[0011] S5 Under a reducing atmosphere, perform Joule heat pyrolysis treatment on the Fe-Ni-Mo-LDH precursor to obtain an iron-nickel-molybdenum-based electrocatalyst, namely a Fe-NiO / MoO2 electrocatalyst.

[0012] Specifically, in step S1, the porous nickel substrate is any one of nickel foam, nickel felt and nickel mesh; the pretreatment is to ultrasonically clean it with 2 mol / L hydrochloric acid solution, acetone and deionized water respectively to obtain a pretreated porous nickel substrate.

[0013] Specifically, in step S1, the sizes of the nickel foam, nickel felt and nickel mesh include 1 cm×1 cm, 3 cm×3 cm and 5 cm×5 cm.

[0014] Specifically, in step S2, the iron salt is ferrous sulfate heptahydrate; the nickel salt is nickel nitrate hexahydrate; the molybdenum salt is ammonium molybdate tetrahydrate.

[0015] Specifically, in step S3, the concentration ratio of the iron salt, nickel salt and molybdenum salt in the mixed solution is (0.001 - 5):(0.01 - 5):(0.001 - 5).

[0016] Specifically, in step S4, the inert electrode is carbon paper, the electrodeposition treatment time is 20 min, and the deposition current is 0.05 A·cm -2 .

[0017] Specifically, in step S5, the treatment temperature of the Joule heat pyrolysis treatment is 750 - 900 °C, the energization time is 60 - 80 s, and the energization current is 80 - 90 A.

[0018] Specifically, in step S5, the reducing atmosphere is a mixed gas of hydrogen and argon; the content of hydrogen in the mixed gas is 10 - 50 vol.%.

[0019] The second object of the present invention is to provide an iron-nickel-molybdenum-based electrocatalyst prepared by the above-mentioned preparation method.

[0020] The third object of the present invention is to provide an application of the above-mentioned iron-nickel-molybdenum-based electrocatalyst in catalytic cracking for hydrogen production.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] (1) The method of combining electrodeposition and rapid Joule heating used in the present invention to prepare the iron-nickel-molybdenum-based electrocatalyst realizes a uniform temperature distribution, can rapidly promote the full reaction of different metal elements at high temperature, form a more uniform and stable nanostructure, thereby improving the catalytic performance of the iron-nickel-molybdenum-based electrocatalyst, and ensuring the controllable thermal reduction and the stable formation of heterogeneous structures during the preparation of the catalyst.

[0023] (2) The present invention regulates the electrolyte composition and current density through electrodeposition treatment to form a porous and uniformly distributed Fe-Ni-Mo precursor; the element ratio can be precisely regulated, and the mass transfer efficiency is improved through the nano-scale pore structure; through Joule heat pyrolysis, the alloying and crystal phase reconstruction of the precursor are quickly completed through instantaneous high-energy thermal shock, avoiding the problem of grain coarsening caused by traditional high-temperature annealing. At the same time, lattice distortion and dislocation defects are introduced through ultra-fast cooling, significantly increasing the density of active sites.

[0024] (3) The Fe-NiO / MoO2 iron-nickel-molybdenum-based electrocatalyst prepared by the present invention is a heterogeneous structure with a nano-sphere morphology. The three-dimensional morphology provides a large specific surface area for the catalyst, while improving the hydrophilic performance of the catalyst, optimizing the three-phase interface during the reaction, promoting bubble desorption, and serving as a highly active bifunctional catalyst in catalytic cracking for hydrogen production. The doping of Fe into the NiO lattice can reduce the Ni 3 + / Ni 2 + redox potential and optimize the adsorption energy of oxygen evolution reaction (OER) intermediates (such as *OOH); at the same time, the NiO substrate promotes the dissociation of H2O through surface hydroxylation. The introduction of MoO2 regulates the electronic state of Fe-NiO, enhances the electronegativity of surface oxygen atoms, effectively repels the adsorption of Cl-, and inhibits the chlorine evolution side reaction in seawater electrolysis. In an alkaline seawater environment, a stable Fe,Mo-NiOOH layer is formed on the surface of Fe-NiO / MoO2. Its highly negatively charged surface blocks the penetration of Cl- through electrostatic repulsion, while preferentially adsorbing H2O molecules, significantly inhibiting corrosion.

[0025] (4) The iron-nickel-molybdenum-based bifunctional catalyst is prepared by the technology of combining electrodeposition and rapid Joule heating. Due to the short reaction time and high heating efficiency, this technology can reduce the energy consumption caused by long-time heating in traditional synthesis methods, which is in line with the concept of sustainable development; at the same time, the reaction speed is fast, the route is simple and controllable, and the repeatability is strong, providing good technical support and material guarantee for industrial scale production. Description of the Drawings

[0026] Figure 1 X-ray diffraction pattern of the a-Fe-NiO / MoO2 electrocatalyst prepared in Example 1 of the present invention;

[0027] Figure 2 X-ray diffraction pattern of the NiO / MoO2 electrocatalyst in Comparative Example 1 of the present invention;

[0028] Figure 3 X-ray diffraction pattern of the NiO electrocatalyst in Comparative Example 2 of the present invention;

[0029] Figure 4 Mo 3d XPS comparative spectra of the electrocatalysts prepared in Example 1 and Comparative Example 1 of the present invention;

[0030] Figure 5 Ni 2p XPS spectra of the electrocatalysts prepared in Example 1 and Comparative Example 1 of the present invention;

[0031] Figure 6 O1s XPS spectra of the electrocatalysts prepared in Example 1 and Comparative Example 1 of the present invention;

[0032] Figure 7 Fe 2p XPS spectrum of the a-Fe-NiO / MoO2 electrocatalyst in Example 1 of the present invention;

[0033] Figure 8 Scanning electron microscope image of the a-Fe-NiO / MoO2 electrocatalyst in Example 1 of the present invention;

[0034] Figure 9 Oxygen evolution reaction activity diagram of the a-Fe-NiO / MoO2 electrocatalyst with nickel foam of different sizes as the substrate in Example 1 of the present invention;

[0035] Figure 10 Hydrogen evolution reaction activity diagram of the a-Fe-NiO / MoO2 electrocatalyst with nickel foam of different sizes as the substrate in Example 1 of the present invention;

[0036] Figure 11 OER activity diagram of the a-Fe-NiO / MoO2 catalyst with nickel felt of different sizes as the substrate prepared in Example 1 of the present invention;

[0037] Figure 12 HER activity diagram of the a-Fe-NiO / MoO2 catalyst with nickel felt of different sizes as the substrate prepared in Example 1 of the present invention;

[0038] Figure 13OER activity diagram of the a-Fe-NiO / MoO2 catalyst with nickel meshes of different sizes as the substrate prepared in Example 1 of the present invention;

[0039] Figure 14 HER activity diagram of the a-Fe-NiO / MoO2 catalyst with nickel meshes of different sizes as the substrate prepared in Example 1 of the present invention;

[0040] Figure 15 OER activity diagram of the a-Fe-NiO / MoO2 catalyst with 1 wt% Fe concentration added and prepared in Example 1 of the present invention at different NaCl concentrations;

[0041] Figure 16 OER activity diagram of the a-Fe-NiO / MoO2 catalyst with 2 wt% Fe concentration added and prepared in Example 1 of the present invention at different NaCl concentrations;

[0042] Figure 17 OER activity diagram of the a-Fe-NiO / MoO2 catalyst with 5 wt% Fe concentration added and prepared in Example 1 of the present invention at different NaCl concentrations;

[0043] Figure 18 OER activity diagram of the a-Fe-NiO / MoO2 catalyst with 10 wt% Fe concentration added and prepared in Example 1 of the present invention at different NaCl concentrations.

[0044] Figure 19 Physical diagram of the a-Fe-NiO / MoO2 electrocatalyst with nickel foam as the substrate in Example 1 of the present invention;

[0045] Figure 20 Physical diagram of the b-Fe-NiO / MoO2 electrocatalyst with nickel felt as the substrate in Example 2 of the present invention;

[0046] Figure 21 Physical diagram of the c-Fe-NiO / MoO2 electrocatalyst with nickel mesh as the substrate in Example 3 of the present invention. Specific implementation plan

[0047] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the content in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0048] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which this invention belongs. The terms used in the specification of this invention are only for the purpose of describing specific embodiments and are not intended to limit the invention. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items. It should be understood that unless otherwise specified, all kinds of raw materials in this invention can be obtained commercially.

[0049] Example 1

[0050] S1 At room temperature, foam nickel substrates with sizes of 1 cm×1 cm, 3 cm×3 cm, and 5 cm×5 cm were successively immersed in 2 mol / L hydrochloric acid solution, acetone solution, and deionized water for ultrasonic treatment. The ultrasonic cleaning time was 40 min, and pretreated foam nickel a with sizes of 1 cm×1 cm, 3 cm×3 cm, and 5 cm×5 cm was obtained respectively.

[0051] S2 At room temperature, nickel nitrate hexahydrate was dispersed in deionized water and ultrasonicated for 40 min to obtain nickel nitrate solution a with a concentration of 0.01 mol / L; ammonium molybdate tetrahydrate was dissolved in deionized water and ultrasonicated for 40 min to obtain ammonium molybdate solution a with a concentration of 0.001 mol / L; ferrous sulfate heptahydrate was dissolved in deionized water and ultrasonicated for 40 min to obtain ferrous sulfate solution a with a concentration of 0.001 mol / L.

[0052] S3 Then, nickel nitrate solution a, ammonium molybdate solution a, and ferrous sulfate solution a were mixed and stirred evenly to obtain mixed solution a.

[0053] S4 The mixed solution a was transferred to a two-electrode electrolytic cell as the electrolyte. The pretreated foam nickel a with sizes of 1 cm×1 cm, 3 cm×3 cm, and 5 cm×5 cm was used as the cathode in turn, and hydrophilic carbon paper was used as the anode. The deposition current was 0.05 A·cm -2 , and the deposition areas were 1 cm×1 cm, 3 cm×3 cm, and 5 cm×5 cm respectively. After deposition for 20 min, it was rinsed with deionized water and vacuum dried at 80 °C for 12 h to obtain a-Fe-Ni-Mo-LDH precursors with deposition areas of 1 cm×1 cm, 3 cm×3 cm, and 5 cm×5 cm respectively.

[0054] S5 sequentially placed a-Fe-Ni-Mo-LDH precursors with deposition areas of 1 cm×1 cm, 3 cm×3 cm, and 5 cm×5 cm flat in the center of a conductive graphite plate, then transferred them into the cavity of a Joule heating device, fixed both sides, and carried out Joule pyrolysis treatment under a hydrogen / argon reducing atmosphere (hydrogen content 10 vol.%). The controlled electric current was set to 80 A, the energization time was 60 s, and the temperature of the rapid Joule heat treatment was 750 °C to obtain black a-Fe-NiO / MoO2 electrocatalysts with sizes of 1 cm×1 cm, 3 cm×3 cm, and 5 cm×5 cm respectively.

[0055] Example 2

[0056] S1 At room temperature, nickel foam substrates with sizes of 1 cm×1 cm, 3 cm×3 cm, and 5 cm×5 cm were sequentially immersed in a 2 mol / L hydrochloric acid solution, acetone solution, and deionized water for ultrasonic treatment for 50 min to obtain pretreated nickel foams b with sizes of 1 cm×1 cm, 3 cm×3 cm, and 5 cm×5 cm respectively;

[0057] S2 At room temperature, nickel nitrate hexahydrate was dispersed in deionized water and ultrasonicated for 40 min to obtain a nickel nitrate solution b with a concentration of 0.05 mol / L; ammonium molybdate tetrahydrate was dissolved in deionized water and ultrasonicated for 40 min to obtain an ammonium molybdate solution b with a concentration of 0.01 mol / L; ferrous sulfate heptahydrate was dissolved in deionized water and ultrasonicated for 40 min to obtain a ferrous sulfate solution b with a concentration of 0.005 mol / L;

[0058] S3 Then, the nickel nitrate solution b, ammonium molybdate solution b, and ferrous sulfate solution b were mixed and stirred evenly to obtain a mixed solution b;

[0059] S4 The mixed solution b was transferred as an electrolyte to a two-electrode electrolytic cell. The pretreated nickel foam b was used as the cathode, and a hydrophilic carbon paper was used as the anode. The deposition current was 0.05 A·cm -2 , the deposition areas were 1 cm×1 cm, 3 cm×3 cm, and 5 cm×5 cm, the deposition time was 20 min, and then it was rinsed clean with deionized water and vacuum dried at 80 °C for 12 h to obtain b-Fe-Ni-Mo-LDH precursors with deposition areas of 1 cm×1 cm, 3 cm×3 cm, and 5 cm×5 cm respectively;

[0060] S5 places the b-Fe-Ni-Mo-LDH precursor flat in the center of the conductive graphite plate, then moves it into the Joule heating equipment cavity and fixes both sides, and performs Joule pyrolysis treatment in a hydrogen / argon reducing atmosphere (hydrogen content 50 vol.%). The controlled current is set to 90 A, the power-on time is 70 s, and the temperature of the rapid Joule heating treatment is 900 ° C. 1 cm × 1 cm, 3 cm × 3 cm, and 5 cm × 5 cm b-Fe-NiO / MoO2 electrocatalysts are obtained, respectively.

[0061] Example 3

[0062] S1: At room temperature, nickel felt substrates with sizes of 1 cm×1 cm, 3 cm×3 cm and 5 cm×5 cm were immersed in 2 mol / L hydrochloric acid solution, acetone solution and deionized water for ultrasonic treatment, and the ultrasonic cleaning time was 60 min to obtain a pretreated nickel mesh c;

[0063] S2: At room temperature, nickel nitrate hexahydrate is dispersed in deionized water and ultrasonicated for 40 minutes to obtain a nickel nitrate solution c with a concentration of 0.5 mol / L; ammonium molybdate tetrahydrate is dissolved in deionized water and ultrasonicated for 40 minutes to obtain an ammonium molybdate solution c with a concentration of 0.5 mol / L; ferrous sulfate heptahydrate is dissolved in deionized water and ultrasonicated for 40 minutes to obtain a ferrous sulfate solution with a concentration of 0.5 mol / L;

[0064] S3: mixing the nickel nitrate solution c, the ammonium molybdate solution c and the ferrous sulfate solution c, and stirring the mixture to obtain a mixed solution c;

[0065] S4 transferred the mixed solution c as the electrolyte into a two-electrode electrolytic cell, and used the pretreated nickel mesh c of 1 cm×1 cm, 3 cm×3 cm, and 5 cm×5 cm as the cathode and the hydrophilic carbon paper as the anode. The deposition current was 0.05 A·cm -2 The deposition areas were 1cm×1cm, 3cm×3cm, and 5cm×5cm, respectively. The deposition was carried out for 20min, and then the mixture was rinsed with deionized water and dried under vacuum at 80℃ for 12h to obtain c-Fe-Ni-Mo-LDH precursors with deposition areas of 1cm×1cm, 3cm×3cm, and 5cm×5cm, respectively.

[0066] S5 places the c-Fe-Ni-Mo-LDH precursor flat in the center of the conductive graphite plate, then moves it into the cavity of the Joule heating equipment and fixes both sides. It performs Joule pyrolysis treatment in a hydrogen / argon reducing atmosphere (hydrogen content 10 vol.%), sets the controlled current to 85 A, the power-on time to 80 s, and the temperature of the rapid Joule heating treatment to 850 ° C to obtain 1 cm × 1 cm, 3 cm × 3 cm, and 5 cm × 5 cm c-Fe-NiO / MoO2 electrocatalysts.

[0067] Comparative Example 1

[0068] Same as Example 1, except that the mixed solution only includes ammonium molybdate solution and nickel nitrate solution, and the NiO / MoO2 electrocatalyst is prepared.

[0069] Comparative Example 2

[0070] Same as Example 1, except that the mixed solution is only nickel nitrate solution, and the prepared electrocatalyst is NiO.

[0071] Comparative Example 3

[0072] Same as Example 1, except that when preparing the Fe-NiO / MoO2 electrocatalyst, the Joule heat pyrolysis is replaced by traditional tube furnace heating pyrolysis.

[0073] Comparative Example 4

[0074] Same as Example 1, except that when preparing the Fe-NiO / MoO2 electrocatalyst, the hydrogen / argon reduction mixed atmosphere is replaced by argon.

[0075] Comparative Example 5

[0076] Same as Example 1, except that when preparing the Fe-Ni-Mo electrocatalyst, the electro-deposition combined with rapid Joule heating technology is replaced by the commonly used hydrothermal synthesis method.

[0077] Performance Test

[0078] Please refer to Figure 1 , Figure 1 which is the X-ray diffraction pattern of the a-Fe-NiO / MoO2 electrocatalyst prepared in Example 1 of the present invention; it can be seen from Figure 1 that the main phases of the Fe-NiO / MoO2 catalyst prepared in the present invention are the crystal structures of molybdenum dioxide and nickel oxide, and the failure to detect the Fe main phase is due to the low Fe content.

[0079] Figure 4 which is the Mo 3d XPS comparative spectrum of the electrocatalysts prepared in Example 1 and Comparative Example 1 of the present invention; it can be seen from Figure 4 that after the precursor is rapidly heated by Joule heat, part of the Mo 6+ component is reduced to produce Mo 4+ , which confirms the existence of MoO2 and oxygen vacancies and is beneficial to the enhancement of conductivity. Figure 5 which is the Ni 2p XPS spectrum of the electrocatalysts prepared in Example 1 and Comparative Example 1 of the present invention; after the precursor is rapidly heated by Joule heat, the 2p orbit of Ni mainly shows Ni 2+ , which confirms the existence of NiO. Figure 6O 1s XPS spectra of the electrocatalysts prepared in Example 1 and Comparative Example 1 of the present invention; it can be seen from Figure 6 that the O 1s of the Fe-NiO / MoO2 catalyst shows a large number of O defects, confirming the existence of oxygen vacancies in MoO2. Figure 7 Fe 2p XPS spectra of the a-Fe-NiO / MoO2 electrocatalyst prepared in Example 1 of the present invention; it can be seen from Figure 7 that the 2p orbit of Fe mainly shows Fe 2+ and Fe 3+ ; Figure 8 Scanning electron microscope image of the a-Fe-NiO / MoO2 electrocatalyst prepared in Example 1 of the present invention; it can be seen from Figure 8 that the a-Fe-NiO / MoO2 catalyst prepared in Example 1 has a nanosphere structure.

[0080] Figure 2 X-ray diffraction spectra of the NiO / MoO2 electrocatalyst prepared in Comparative Example 1 of the present invention; Figure 3 X-ray diffraction spectra of the NiO electrocatalyst prepared in Comparative Example 2 of the present invention;

[0081] Figure 19 Physical diagram of the a-Fe-NiO / MoO2 electrocatalyst with nickel foam as the substrate in Example 1 of the present invention; Figure 20 Physical diagram of the b-Fe-NiO / MoO2 electrocatalyst with nickel felt as the substrate in Example 2 of the present invention; Figure 21 Physical diagram of the c-Fe-NiO / MoO2 electrocatalyst with nickel mesh as the substrate in Example 3 of the present invention. It can be seen that the technology combining electrodeposition and rapid Joule heating provided by the present invention can be used to prepare iron-nickel-molybdenum-based electrocatalysts with different substrates and different sizes.

[0082] Hydrogen production effect test of the Fe-NiO / MoO2 electrocatalyst prepared in Examples 1-3 by water splitting

[0083] (1) The electrocatalysts prepared in Examples 1-3 were successively loaded on nickel foams, nickel felts and nickel meshes with different sizes (1 cm × 1 cm, 3 cm × 3 cm and 5 cm × 5 cm) after pretreatment, and then used as working electrodes respectively; a mercury / mercuric oxide electrode was used as the reference electrode; a platinum wire electrode was used as the counter electrode.

[0084] (2) The electrolytes for the test were 1 M KOH solution, 1 M KOH + 1 M NaCl solution, 1 M KOH + 2 M NaCl solution and 1 M KOH + 3 M NaCl solution.

[0085] Hydrogen production effect test of the electrocatalysts prepared in Comparative Examples 1-5 by water splitting

[0086] (1) The electrocatalysts of Comparative Examples 1-5 were successively loaded on nickel foam, nickel felt, and nickel mesh with different sizes (1 cm × 1 cm, 3 cm × 3 cm, and 5 cm × 5 cm) after pretreatment, and then they were used as working electrodes respectively; the mercury / mercuric oxide electrode was used as the reference electrode; and the platinum wire electrode was used as the counter electrode.

[0087] (2) The electrolytes for testing were 1 M KOH solution, 1 M KOH + 1 M NaCl solution, 1 M KOH + 2 M NaCl solution, and 1 M KOH + 3 M NaCl solution.

[0088] The electrocatalytic performance results of the catalysts prepared in Examples 1-3 and Comparative Examples 1-5 are shown in Tables 1-2 and Figures 9 - 18 .

[0089] Table 1 OER performance of Fe-NiO / MoO2 catalyst

[0090] Overpotential 1 cm × 1 cm 3 cm × 3 cm 5 cm × 5 cm Example 1 <![CDATA[227mV@100mAcm -2 > <![CDATA[233mV@100mAcm -2 > <![CDATA[235mV@100mAcm -2 > Example 2 <![CDATA[234mV@100mAcm -2 > <![CDATA[235mV@100mAcm -2 > <![CDATA[240mV@100mAcm -2 > Example 3 <![CDATA[247mV@100mAcm -2 > <![CDATA[247mV@100mAcm -2 > <![CDATA[250mV@100mAcm -2 > Comparative Example 1 <![CDATA[278mV@100mAcm -2 > <![CDATA[280mV@100mAcm -2 > <![CDATA[275mV@100mAcm -2 > Comparative Example 2 <![CDATA[290mV@100mAcm -2 > <![CDATA[287mV@100mAcm -2 > <![CDATA[288mV@100mAcm -2 <!-- 6 -->]]> Comparative Example 3 <![CDATA[242mV@100mAcm -2 > <![CDATA[242mV@100mAcm -2 > <![CDATA[242mV@100mAcm -2 > Comparative Example 4 <![CDATA[256mV@100mAcm -2 > <![CDATA[253mV@100mAcm -2 > <![CDATA[256mV@100mAcm -2 > Comparative Example 5 <![CDATA[248mV@100mAcm -2 > <![CDATA[251mV@100mAcm -2 > <![CDATA[249mV@100mAcm -2 >

[0091] Table 2 HER performance of Fe-NiO / MoO2 catalyst

[0092] Overpotential 1 cm × 1 cm 3 cm × 3 cm 5 cm × 5 cm Example 1 <![CDATA[42mV@10mAcm -2 > <![CDATA[43mV@10mAcm -2 > <![CDATA[42mV@10mAcm -2 > Example 2 <![CDATA[46mV@10mAcm -2 > <![CDATA[48mV@10mAcm -2 > <![CDATA[45mV@10mAcm -2 > Example 3 <![CDATA[50mV@10mAcm -2 > <![CDATA[50mV@10mAcm -2 > <![CDATA[53mV@10mAcm -2 > Comparative Example 1 <![CDATA[43mV@10mAcm -2 > <![CDATA[43mV@10mAcm -2 > <![CDATA[46mV@10mAcm -2 > Comparative Example 2 <![CDATA[82mV@10mAcm -2 > <![CDATA[81mV@10mAcm -2 > <![CDATA[84mV@10mAcm -2 > Comparative Example 3 <![CDATA[65mV@10mAcm -2 > <![CDATA[63mV@10mAcm -2 > <![CDATA[70mV@10mAcm -2 > Comparative Example 4 <![CDATA[55mV@10mAcm -2 > <![CDATA[52mV@10mAcm -2 > <![CDATA[53mV@10mAcm -2 > Comparative Example 5 <![CDATA[65mV@10mAcm -2 > <![CDATA[65mV@10mAcm -2 > <![CDATA[65mV@10mAcm -2 >

[0093] As can be seen from Tables 1-2, compared with the NiO / MoO2 electrocatalyst prepared in Comparative Example 1 and the NiO electrocatalyst prepared in Comparative Example 2, in the α-Fe-NiO / MoO2 electrocatalyst prepared in Example 1, the doping of Fe into the NiO lattice reduces the Ni 3 + / Ni 2 +redox potential, optimizes the adsorption free energy of OER intermediates, MoO2 enhances the H2O dissociation ability through interfacial charge redistribution, precisely regulates the active sites, and improves the catalytic activity; and the surface of α-Fe-NiO / MoO2 is reconstructed into Fe,Mo-NiOOH, and the highly negatively charged oxygen atom layer blocks the penetration of Cl- through electrostatic repulsion, effectively improving the salt tolerance and corrosion resistance of the catalyst. Compared with the hydrothermal synthesis technology, the technology combining electrodeposition and rapid Joule heating can precisely regulate the precursor composition and substrate morphology, form a highly active heterointerface, and introduce lattice distortion, dislocation defects, and oxygen vacancies through rapid cooling, effectively improving the catalyst activity. And the formed surface reconstruction layer (Fe,Mo-NiOOH) inhibits the Cl- adsorption through electrostatic repulsion, significantly improving the corrosion resistance and stability of the catalyst. Figure 9 This is the oxygen evolution reaction activity diagram of the α-Fe-NiO / MoO2 electrocatalyst with nickel foam of different sizes as the substrate in Example 1 of the present invention; Figure 10 This is the hydrogen evolution reaction activity diagram of the α-Fe-NiO / MoO2 catalyst with nickel foam of different sizes as the substrate in Example 1 of the present invention;

[0094] Figure 11 OER activity diagram of the b-Fe-NiO / MoO2 catalyst with nickel felts of different sizes as the substrate prepared in Example 2 of the present invention; Figure 12 HER activity diagram of the b-Fe-NiO / MoO2 catalyst with nickel felts of different sizes as the substrate prepared in Example 2 of the present invention; Figure 13 OER activity diagram of the c-Fe-NiO / MoO2 catalyst with nickel mesh as the substrate prepared in Example 3 of the present invention; Figure 14 HER activity diagram of the c-Fe-NiO / MoO2 catalyst with nickel mesh as the substrate prepared in Example 3 of the present invention; It can be seen from the performance diagram of Figures 9 - 14 that the Fe-NiO / MoO2 catalyst has excellent hydrogen evolution (HER) and oxygen evolution (OER) performance on different substrates.

[0095] Figure 15 OER activity diagram of the a-Fe-NiO / MoO2 catalyst with an added amount of 1 wt% Fe concentration prepared in Example 1 of the present invention at different NaCl concentrations; Figure 16 OER activity diagram of the a-Fe-NiO / MoO2 catalyst with an added amount of 2 wt% Fe concentration prepared in Example 1 of the present invention at different NaCl concentrations; Figure 17 OER activity diagram of the a-Fe-NiO / MoO2 catalyst with an added amount of 5 wt% Fe concentration prepared in Example 1 of the present invention at different NaCl concentrations; Figure 18 OER activity diagram of the a-Fe-NiO / MoO2 catalyst with an added amount of 10 wt% Fe concentration prepared in Example 1 of the present invention at different NaCl concentrations. In an alkaline seawater environment, a stable Fe,Mo-NiOOH layer is formed on the surface of Fe-NiO / MoO2. Its highly negatively charged surface blocks the penetration of Cl- through electrostatic repulsion, and at the same time preferentially adsorbs H2O molecules, significantly inhibiting corrosion. For the hydrogen evolution reaction, in an alkaline seawater environment, the overpotential of Fe-NiO / MoO2 at 1000 mA cm -2 is 417 mV. In a 1 M KOH electrolyte, from 0 M NaCl to 3 M NaCl, the overpotential of Fe-NiO / MoO2 at 500 mA cm -2 hardly changes. For the oxygen evolution reaction, Fe-NiO / MoO2 is reconstructed into NiOOH co-doped with Fe and Mo (Fe,Mo-NiOOH). The reconstructed Fe,Mo-NiOOH in alkaline seawater at 1000 mA cm -2The overpotential reaches 399 mV, and in 1 M KOH electrolyte, from 0 M NaCl to 3 M NaCl, the overpotential of Fe, Mo-NiOOH increases by approximately 20 mV at 500 mA cm -2 The FeNiO / MoO2 can operate stably for 50 h under the condition of 100 mA cm in 1 M KOH electrolyte and 3 M NaCl, with good corrosion resistance and salt tolerance, and can be used in the field of seawater electrolysis. -2

[0096] The embodiments described above are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.​

Claims

1. A method for preparing an iron-nickel-molybdenum-based electrocatalyst by combining electrodeposition and rapid Joule heating, characterized in that, The method includes: S1 Pretreat the porous nickel substrate to obtain a pretreated porous nickel substrate; S2 Dissolve nickel salt, molybdenum salt and iron salt in deionized water respectively to obtain a nickel salt solution, a molybdenum salt solution and an iron salt solution; S3 Mix and stir the nickel salt solution, molybdenum salt solution and iron salt solution evenly to obtain a mixed solution; S4 Use the mixed solution as an electrolyte in a two-electrode electrolytic cell, use the pretreated porous nickel substrate as the cathode, and an inert electrode as the anode for electrodeposition treatment, and then wash and dry to obtain a Fe-Ni-Mo-LDH precursor; S5 Under a reducing atmosphere, perform Joule heating pyrolysis treatment on the Fe-Ni-Mo-LDH precursor to obtain an iron-nickel-molybdenum-based electrocatalyst, namely a Fe-NiO / MoO2 electrocatalyst.

2. The method according to claim 1, wherein In step S1, the porous nickel substrate is any one of nickel foam, nickel felt and nickel mesh; the pretreatment is to ultrasonically clean it with 2 mol / L hydrochloric acid solution, acetone and deionized water respectively to obtain a pretreated porous nickel substrate.

3. The method according to claim 2, characterized in that In step S1, the sizes of the nickel foam, nickel felt and nickel mesh include 1 cm×1 cm, 3 cm×3 cm and 5 cm×5 cm.

4. The method according to claim 1, wherein In step S2, the iron salt is ferrous sulfate heptahydrate; the nickel salt is nickel nitrate hexahydrate; the molybdenum salt is ammonium molybdate tetrahydrate.

5. The method according to claim 1, wherein In step S3, the concentration ratio of the iron salt, nickel salt and molybdenum salt in the mixed solution is (0.001~5):(0.01~5):(0.001~5).

6. The method according to claim 1, wherein In step S4, the inert electrode is carbon paper, the electrodeposition treatment time is 20 min, and the deposition current is 0.05 A·cm -2 .

7. The method according to claim 1, wherein In step S5, the treatment temperature of the Joule heating pyrolysis treatment is 750~900 °C, the energization time is 60~80 s, and the energization current is 80~90 A.

8. The method according to claim 1, characterized in that, In step S5, the reducing atmosphere is a mixed gas of hydrogen and argon; the content of hydrogen in the mixed gas is 10~50 vol.%.

9. An iron-nickel-molybdenum-based electrocatalyst prepared by the preparation method according to any one of claims 1~7.

10. Application of the iron-nickel-molybdenum-based electrocatalyst according to claim 9 in catalytic cracking for hydrogen production.

Images