CN118028886A - Alkaline electrolyzed water catalyst with iron-based heterostructure, and preparation method and application thereof - Google Patents
Alkaline electrolyzed water catalyst with iron-based heterostructure, and preparation method and application thereof Download PDFInfo
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 101
- 239000003054 catalyst Substances 0.000 title claims abstract description 79
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 78
- 229910052742 iron Inorganic materials 0.000 title claims abstract description 20
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- 238000006243 chemical reaction Methods 0.000 claims abstract description 73
- 238000004070 electrodeposition Methods 0.000 claims abstract description 31
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 30
- 238000000034 method Methods 0.000 claims abstract description 24
- 238000001035 drying Methods 0.000 claims abstract description 17
- 239000006260 foam Substances 0.000 claims abstract description 14
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 14
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- 230000008569 process Effects 0.000 claims abstract description 12
- 150000003839 salts Chemical class 0.000 claims abstract description 11
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 claims abstract description 10
- 239000001509 sodium citrate Substances 0.000 claims abstract description 10
- 238000005406 washing Methods 0.000 claims abstract description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 35
- 239000012498 ultrapure water Substances 0.000 claims description 22
- 239000011734 sodium Substances 0.000 claims description 11
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 10
- 229910002554 Fe(NO3)3·9H2O Inorganic materials 0.000 claims description 10
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 10
- 229910002422 La(NO3)3·6H2O Inorganic materials 0.000 claims description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 7
- 239000008367 deionised water Substances 0.000 claims description 7
- 229910021641 deionized water Inorganic materials 0.000 claims description 7
- 235000019441 ethanol Nutrition 0.000 claims description 7
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical group [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 claims description 7
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- 239000001301 oxygen Substances 0.000 claims description 7
- 125000004122 cyclic group Chemical group 0.000 claims description 3
- 239000002659 electrodeposit Substances 0.000 claims description 3
- FYDKNKUEBJQCCN-UHFFFAOYSA-N lanthanum(3+);trinitrate Chemical group [La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FYDKNKUEBJQCCN-UHFFFAOYSA-N 0.000 claims description 3
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 19
- 239000001257 hydrogen Substances 0.000 abstract description 19
- 230000000694 effects Effects 0.000 abstract description 14
- 238000000926 separation method Methods 0.000 abstract description 6
- 229910002588 FeOOH Inorganic materials 0.000 abstract description 5
- 125000004435 hydrogen atom Chemical class [H]* 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 28
- 239000007772 electrode material Substances 0.000 description 21
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 16
- 230000015572 biosynthetic process Effects 0.000 description 15
- 239000003792 electrolyte Substances 0.000 description 12
- 238000003786 synthesis reaction Methods 0.000 description 12
- 238000001291 vacuum drying Methods 0.000 description 11
- 238000002484 cyclic voltammetry Methods 0.000 description 8
- 239000010411 electrocatalyst Substances 0.000 description 6
- 238000011010 flushing procedure Methods 0.000 description 6
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 6
- 230000004913 activation Effects 0.000 description 5
- 230000008901 benefit Effects 0.000 description 5
- 238000005868 electrolysis reaction Methods 0.000 description 5
- 239000002243 precursor Substances 0.000 description 5
- 238000001179 sorption measurement Methods 0.000 description 5
- 239000000758 substrate Substances 0.000 description 5
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- 230000002194 synthesizing effect Effects 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 229910000510 noble metal Inorganic materials 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229920000557 Nafion® Polymers 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000003795 desorption Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000000407 epitaxy Methods 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 239000000543 intermediate Substances 0.000 description 2
- 239000013067 intermediate product Substances 0.000 description 2
- 150000002505 iron Chemical class 0.000 description 2
- 229910052746 lanthanum Inorganic materials 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000000178 monomer Substances 0.000 description 2
- 239000011943 nanocatalyst Substances 0.000 description 2
- 229910052761 rare earth metal Inorganic materials 0.000 description 2
- 230000000638 stimulation Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000003746 surface roughness Effects 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 150000003624 transition metals Chemical class 0.000 description 2
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- 239000004480 active ingredient Substances 0.000 description 1
- VREFGVBLTWBCJP-UHFFFAOYSA-N alprazolam Chemical compound C12=CC(Cl)=CC=C2N2C(C)=NN=C2CN=C1C1=CC=CC=C1 VREFGVBLTWBCJP-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
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- 230000002708 enhancing effect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 125000005842 heteroatom Chemical group 0.000 description 1
- 230000002209 hydrophobic effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- HTXDPTMKBJXEOW-UHFFFAOYSA-N iridium(IV) oxide Inorganic materials O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
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- 229910052697 platinum Inorganic materials 0.000 description 1
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
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Abstract
The invention relates to an alkaline electrolyzed water catalyst with an iron-based heterostructure, a preparation method and application thereof. The preparation method of the alkaline electrolyzed water catalyst with the iron-based heterostructure comprises the following steps: dissolving ferric salt, lanthanum salt and sodium citrate in water to obtain a reaction solution; immersing foam nickel serving as a working electrode in the reaction solution to perform electrodeposition reaction; and washing and drying the working electrode after the reaction is finished to obtain the alkaline electrolyzed water catalyst. The alkaline electrolyzed water catalyst of the iron-based heterostructure, the preparation method and the application thereof, provided by the invention, utilize electrodeposition to obtain the LaOOH/Fe 3O4 heterostructure, and reconstruct the surface into the FeOOH/LaOOH/Fe 3O4 heterostructure in the electrochemical process, so that high activity and stability are provided for integral water separation, and the catalyst is an effective means for realizing industrialized electrocatalytic hydrogen separation.
Description
Technical Field
The invention belongs to the technical field of catalysts, and particularly relates to an alkaline electrolyzed water catalyst with an iron-based heterostructure, and a preparation method and application thereof.
Background
The global energy system is continuously changing to environmental protection and low carbon. Hydrogen has been attracting research attention as a clean renewable energy source because of its long storage time and high energy density. Alkaline electrolyzed water process (AWE) has been widely used for large scale industrial hydrogen production. However, the slow kinetics inherent to Oxygen Evolution Reactions (OER) limit the effective reduction of AWE cell voltage. Meanwhile, in alkaline electrolytes, the Hydrogen Evolution Reaction (HER) of the cathode also presents a problem of poor efficiency. Although the traditional noble metal catalysts Pt, ru, pd and the like have better water electrolysis application efficiency, the large-scale commercial application is difficult to realize due to the rare reserves and high price. Therefore, the design of the non-noble metal catalyst for water electrolysis hydrogen production with both activity and economic benefit is important for the development of an alkaline water electrolytic cell, so that the high-efficiency water electrolysis under the high current density required by industry is realized.
Research reports that Fe 3O4 is widely used as a highly efficient OER electrocatalyst because of the excellent electron conductivity imparted to Fe 3O4 by the localized charge transfer between Fe 2+ and Fe 3+ at the octahedral Fe sites. Much research is devoted to manipulating the adsorption strength of OER intermediates on active sites through metal doping, morphology control and heterointerface engineering. The strong interface electric field of the heterojunction can improve the d-band center of the electrocatalyst and enhance the adsorption of intermediate species; heterostructures are one possible alternative to expensive electrocatalysts because of their tunable properties. The origin of the activity and stability of the heterostructure is the coupling between its constituent components. Therefore, establishing the coupling effect of interface components such as Mott-Schottky effect, strong metal-carrier-interaction effect, carrier stabilization effect, synergistic effect and the like is a promising technology for improving activity and stability. The rare earth element lanthanum (La) is taken as a doping element, and the OER and HER performances of the transition metal electrocatalyst are improved mainly by adjusting an electronic structure, generating oxygen vacancies and changing a morphology structure.
In view of the above, the invention provides a new alkaline electrolyzed water catalyst, namely a surface-reconstructed iron-based heterostructure, which has the advantages of high activity and stability and is an effective means for realizing industrialized electrocatalytic hydrogen evolution.
Disclosure of Invention
The invention aims to provide a preparation method of an alkaline electrolyzed water catalyst with an iron-based heterostructure, which utilizes electrodeposition to perform in-situ growth to prepare the alkaline electrolyzed water catalyst with the heterostructure of LaOOH/Fe 3O4.
In order to achieve the above purpose, the technical scheme adopted is as follows:
The preparation method of the alkaline electrolyzed water catalyst with the iron-based heterostructure comprises the following steps: dissolving ferric salt, lanthanum salt and sodium citrate in water to obtain a reaction solution; immersing foam nickel serving as a working electrode in the reaction solution to perform electrodeposition reaction; and washing and drying the working electrode after the reaction is finished to obtain the alkaline electrolyzed water catalyst.
Further, the foam nickel is pretreated and then used as a working electrode;
The pretreatment process comprises the following steps: the foam nickel is respectively cleaned by acetone, hydrochloric acid, deionized water and ethanol under ultrasonic wave and then dried.
Further, the molar ratio of the ferric salt to the lanthanum salt to the sodium citrate is 10: 1-5:1;
The ferric salt is ferric nitrate;
The lanthanum salt is lanthanum nitrate.
Still further, the iron salt is Fe (NO 3)3·9H2 O;
The lanthanum salt is La (NO 3)3·6H2 O;
Sodium citrate is C 6H5Na3O7·2H2 O.
Further, the conditions of the electrodeposition reaction are as follows: and (3) carrying out electrodeposition reaction within the potential range of-1.2-0.8V vs. Hg/HgO.
Still further, the electrodeposition reaction conditions are: 100 cyclic voltammetric electrodeposits were performed.
Further, the working electrode after the reaction is washed by high-purity water and absolute ethyl alcohol, and then dried for 10 to 14 hours at 75 to 85 ℃.
Further, the working electrode after the completion of the reaction was rinsed with high-purity water and absolute ethanol, and then dried at 80℃for 12 hours.
The invention further aims to provide an alkaline electrolyzed water catalyst with an iron-based heterostructure, which is prepared by adopting the preparation method, and has a LaOOH/Fe 3O4 heterostructure, and active metal sites are uniformly dispersed by utilizing chemical bond adsorption of LaOOH and Fe 3O4 in an electrodeposition process, so that the density of the active sites is improved, meanwhile, the falling-off of the catalyst in the OER and HER reaction process is avoided, and the electrocatalytic hydrogen evolution efficiency is improved.
It is still another object of the present invention to provide the use of the above alkaline electrolyzed water catalyst in an oxygen evolution reaction.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the technical scheme, laOOH/Fe 3O4 is self-supported and grown on the foam nickel by adopting a one-step electrodeposition method, and the catalyst has the characteristics of surface roughness and porosity.
2. According to the technical scheme, the prepared catalyst has good electrocatalytic activity and stability under high current density in alkaline electrolyte, and provides possibility for realizing industrialization.
3. According to the technical scheme, the prepared catalyst promotes electron redistribution between LaOOH and Fe 3O4 on the nano scale by forming the heterojunction, so that the integral water separation reaction is promoted.
4. According to the technical scheme, the prepared catalyst has the advantages of small water drop contact angle and small desorption hydrogen diameter of LaOOH/Fe 3O4 material and large underwater bubble contact angle on a microscopic scale, so that the whole water diversion reaction has obvious advantages. The hydrophilicity and hydrophobicity allow the electrode to be in sufficient contact with the electrolyte to obtain the desired intermediate product while ensuring rapid separation of hydrogen bubbles from the electrode surface. Subsequently, the adsorption sites on the electrode are again exposed, and the subsequent adsorption process is restarted.
5. According to the technical scheme, a direct method is provided for manufacturing the heterojunction nano-catalyst through electrodeposition, and basic research on design of the high-current-density water electrolysis catalyst is greatly promoted. Provides better reference and guidance for the Fe 3O4 material to become an electrocatalytic material.
Drawings
FIG. 1 is an X-ray diffraction diagram of LaOOH/Fe 3O4 for different La, fe ratios;
FIG. 2 is a transmission electron micrograph of LaOOH/Fe 3O4 at La/Fe=0.1;
FIG. 3 is an X-ray diffraction pattern of LaOOH/Fe 3O4 with La/Fe=0.1 for OER activation for 100 h;
FIG. 4 is a transmission electron microscope image of LaOOH/Fe 3O4 with La/Fe=0.1 for OER activation for 100 h;
FIG. 5 is a graph comparing LF-0.1 contact angle with precursor;
FIG. 6 shows oxygen evolution overpotential and Tafel slope for six catalysts under alkaline conditions;
FIG. 7 shows hydrogen evolution overpotential and Tafel slope for six catalysts under alkaline conditions;
Fig. 8 is OER stability of the optimal catalyst under alkaline conditions.
Detailed Description
In order to further illustrate the alkaline electrolyzed water catalyst with the iron-based heterostructure, the preparation method and the application of the alkaline electrolyzed water catalyst with the iron-based heterostructure, which are disclosed by the invention, the specific implementation, the structure, the characteristics and the efficacy of the alkaline electrolyzed water catalyst with the iron-based heterostructure are described in detail below by combining with the preferred embodiment. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.
The alkaline electrolyzed water catalyst with the iron-based heterostructure, the preparation method and the application of the alkaline electrolyzed water catalyst with the iron-based heterostructure are described in further detail below by combining specific embodiments:
Hydrogen is considered a green alternative energy source to fossil fuels, while alkaline water electrolysis represents an extremely attractive commercial technology for large-scale hydrogen production. Commercial Pt/C and IrO2/RuO 2 are considered excellent catalysts for water splitting, but their reserves have hampered their widespread use. In recent years, non-noble metal based catalysts have evolved greatly in HER and OER. However, most of the newly discovered catalysts only have significant electrocatalytic activity at low current densities (10-50 mA cm -2). However, there is a great need in the industry for bifunctional electrocatalysts to drive water splitting at high current densities of 200-500 mA cm -2, and to address this problem, researchers have developed a range of solutions such as bimetallic engineering, crystal phase adjustment, defect introduction, non-metallic doping and heterostructure construction. At the same time, as a chemical reaction occurring on the electrode surface, the reconstitution process and the number and activity of the resulting reconstituted species are also affected by the activation conditions and the nature of the catalyst, and regulating the reconstitution process to produce a large number of highly active reactive species has proven to be an effective strategy for improving the catalytic performance of electrocatalysts.
Based on the above, the invention provides an alkaline electrolyzed water catalyst of an iron-based heterojunction, and a preparation method and application thereof. The invention synthesizes a LaOOH/Fe 3O4 heterojunction catalyst by adopting a one-step electrodeposition method, and the catalyst comprises the following components: (1) The hydrophilic and hydrophobic properties of LaOOH/Fe 3O4 electrode ensure the attachment of electrolyte and the growth of oxygen and hydrogen and rapid detachment in the early stage of OER reaction; (2) And secondly, the heterojunction is formed, so that better conductivity and larger electrochemical active area are obtained, and the rapid transmission of electrons and the exposure of active sites are facilitated. (3) In addition, through electrochemical activation, under the potential stimulation, some components of LaOOH/Fe 3O4 precursor can be leached out on the interface between the catalyst and the electrolyte and react with the electrolyte to form amorphous phase FeOOH/LaOOH/Fe 3O4 on the surface of the precursor. This also provides more reference and options for the final active component of the electrochemical reaction. The mode of introducing rare earth elements into the metal oxide Fe 3O4 can be popularized to most transition metals, and meanwhile, certain possibility is provided for the Fe 3O4 -based catalyst to become an electrocatalytic hydrogen evolution catalyst. The technical scheme adopted by the invention is as follows:
The preparation method of the alkaline electrolyzed water catalyst with the iron-based heterostructure comprises the following steps: dissolving ferric salt, lanthanum salt and sodium citrate in water to obtain a reaction solution; immersing foam nickel serving as a working electrode in the reaction solution to perform electrodeposition reaction; and washing and drying the working electrode after the reaction is finished to obtain the alkaline electrolyzed water catalyst.
In the above technical solution, the electrochemical activation can allow some components of the precursor to leach out at the catalyst-electrolyte interface under the stimulation of electric potential and react with the electrolyte to form an amorphous phase on the surface of the precursor. While the introduction of heteroatoms or vacancies would disrupt the original structure, thereby accelerating dissolution and subsequent redeposition of the active ingredient. Therefore, the invention provides an in-situ growth preparation method for obtaining LaOOH/Fe 3O4 heterostructure by utilizing electrodeposition, and the surface reconstruction is FeOOH/LaOOH/Fe 3O4 heterostructure in the electrochemical process, so that high activity and stability are provided for integral water separation, and the method is an effective means for realizing industrialized electrocatalytic hydrogen evolution.
Preferably, the foam nickel is pretreated and then used as a working electrode;
The pretreatment process comprises the following steps: the foam nickel is respectively cleaned by acetone, hydrochloric acid, deionized water and ethanol under ultrasonic wave and then dried.
Preferably, the molar ratio of the ferric salt to the lanthanum salt to the sodium citrate is 10: 1-5:1;
The ferric salt is ferric nitrate;
The lanthanum salt is lanthanum nitrate.
Further preferably, the iron salt is Fe (NO 3)3·9H2 O;
The lanthanum salt is La (NO 3)3·6H2 O;
Sodium citrate is C 6H5Na3O7·2H2 O.
Preferably, the conditions of the electrodeposition reaction are as follows: and (3) carrying out electrodeposition reaction within the potential range of-1.2-0.8V vs. Hg/HgO.
Further preferably, the conditions of the electrodeposition reaction are: 100 cyclic voltammetric electrodeposits were performed.
Preferably, the working electrode after the reaction is washed with high-purity water and absolute ethyl alcohol, and then dried at 75-85 ℃ for 10-14 hours.
Further preferably, the working electrode after completion of the reaction is rinsed with high-purity water and absolute ethanol, and then dried at 80℃for 12 hours.
The LaOOH/Fe 3O4 heterojunction is synthesized by adopting a one-step electrodeposition method. The heterojunction formed at the lower LaOOH/Fe 3O4 ratio redistributes electrons at the interface, enhancing conductivity. In addition, the introduction LaOOH also optimizes the hydrophilicity and hydrophobicity of the electrode surface. Thus, in alkaline electrolytes, the activities of the hydrogen evolution reaction and the oxygen evolution reaction were 101mV (1000 A.m -2) and 350mV (5000 A.m -2), respectively. Further, at current densities of 100a·m -2 and 5000a·m -2, the cell voltages were 1.44V and 1.85V, respectively.
The invention provides a direct method for preparing the heterojunction nano-catalyst by electrodeposition. Mainly comprises the following steps: (1) Synthesizing LaOOH/Fe 3O4 with LaOOH/Fe 3O4 =0 molar ratio; (2) Synthesis LaOOH/Fe 3O4 = 0.1 molar ratio LaOOH/Fe 3O4; (3) Synthesis LaOOH/Fe 3O4 = 0.3 molar ratio LaOOH/Fe 3O4; (4) Synthesis LaOOH/Fe 3O4 = 0.5 molar ratio LaOOH/Fe 3O4; (5) synthesizing a monomer catalyst containing LaOOH alone; (6) Synthesizing a monomer catalyst containing only Fe 3O4; (7) vacuum drying the collected electrode material. Specific examples are as follows:
Example 1.
The invention relates to a preparation method of an alkaline electrolyzed water catalyst with a surface reconstructed iron-based heterojunction, which is used for constructing a difunctional electrolyzed water catalyst with high efficiency and stability under high current density, and specifically comprises the following steps:
(1) Pretreatment of a substrate: cutting foam Nickel (NF) into rectangle with the length of 1X 1.5cm, and cleaning with acetone, hydrochloric acid, deionized water and ethanol under ultrasonic wave for 15min. And then drying the NF to obtain the catalyst substrate.
(2) Synthesis LaOOH/Fe 3O4 -0.1:
Fe (NO 3)3·9H2O(1.5mmol)、La(NO3)3·6H2 O (0.15 mmol) and C 6H5Na3O7·2H2 O (1.5 mmol) were dissolved in 40mL high-purity water and sonicated for 15min to give a reaction solution.
Immersing NF treated in the step (1) as a working electrode in a reaction solution to perform 100 times of Cyclic Voltammetry (CV) electrodeposition within a potential range of-1.2 to 0.8Vvs. And (3) flushing the electrode material after the reaction is finished by using high-purity water and absolute ethyl alcohol, and rapidly transferring the electrode material to a vacuum drying oven for drying at 80 ℃ for 12 hours to obtain the alkaline electrolyzed water catalyst.
Since the molar ratio of [ La (NO 3)3]/[Fe(NO3)3 ] was 0.1, the obtained alkaline electrolyzed water catalyst was designated LaOOH/Fe 3O4 -0.1 (abbreviated as LF-0.1).
(3) Synthesis LaOOH/Fe 3O4 -0.3:
Fe (NO 3)3·9H2O(1.5mmol)、La(NO3)3·6H2 O (0.45 mmol) and C 6H5Na3O7·2H2 O (1.5 mmol) were dissolved in 40mL high-purity water and sonicated for 15min to give a reaction solution.
Immersing NF treated in the step (1) as a working electrode in a reaction solution to perform 100 times of Cyclic Voltammetry (CV) electrodeposition within a potential range of-1.2-0.8V vs. Hg/HgO. And (3) flushing the electrode material after the reaction is finished by using high-purity water and absolute ethyl alcohol, and rapidly transferring the electrode material to a vacuum drying oven for drying at 80 ℃ for 12 hours to obtain an alkaline electrolyzed water catalyst LaOOH/Fe 3O4 -0.3 (LF-0.3 for short).
(4) Synthesis LaOOH/Fe 3O4 -0.5:
Fe (NO 3)3·9H2O(1.5mmol)、La(NO3)3·6H2 O (0.75 mmol) and C 6H5Na3O7·2H2 O (1.5 mmol) were dissolved in 40mL high-purity water and sonicated for 15min to give a reaction solution.
Immersing NF treated in the step (1) as a working electrode in a reaction solution to perform 100 times of Cyclic Voltammetry (CV) electrodeposition within a potential range of-1.2 to 0.8Vvs. And (3) flushing the electrode material after the reaction is finished by using high-purity water and absolute ethyl alcohol, and rapidly transferring the electrode material to a vacuum drying oven for drying at 80 ℃ for 12 hours to obtain an alkaline electrolyzed water catalyst LaOOH/Fe 3O4 -0.5 (LF-0.5 for short).
(5) Synthesis LaOOH:
La (NO 3)3·6H2 O (0.15 mmol) and C 6H5Na3O7·2H2 O (1.5 mmol) were dissolved in 40mL high-purity water and sonicated for 15min to give a reaction solution.
Immersing NF treated in the step (1) as a working electrode in a reaction solution to perform 100 times of Cyclic Voltammetry (CV) electrodeposition within a potential range of-1.2 to 0.8Vvs. After the electrode material after the reaction is finished is washed by high-purity water and absolute ethyl alcohol, the electrode material is quickly transferred to a vacuum drying oven for drying at 80 ℃ for 12 hours, and then the alkaline electrolyzed water catalyst LaOOH (L for short) is obtained
(6) Synthesizing an Fe 3O4 electrode material:
Fe (NO 3)3·9H2 O (1.5 mmol) and C 6H5Na3 O7·2H2 O (1.5 mmol) were dissolved in 40mL high-purity water and sonicated for 15min to give a reaction solution.
Immersing NF treated in the step (1) as a working electrode in a reaction solution to perform 100 times of Cyclic Voltammetry (CV) electrodeposition within a potential range of-1.2 to 0.8Vvs. After the electrode material after the reaction is finished is washed by high-purity water and absolute ethyl alcohol, the electrode material is quickly transferred to a vacuum drying oven for drying for 12 hours at 80 ℃ to obtain an alkaline electrolyzed water catalyst Fe 3O4 (F for short)
(7) Synthesis of control OER electrode material:
2mg of commercial RuO 2 was weighed and dispersed in a mixed solution (deionized water 500. Mu.L, ethanol 500. Mu.L and Nafion solution 30. Mu.L), and sonicated for 10min to obtain a dispersion.
And (3) selecting NF in the step (1), dripping 100uL of dispersion liquid, rapidly transferring to a vacuum drying oven, and drying at 80 ℃ for 12 hours to obtain an alkaline electrolyzed water catalyst RuO 2.
(8) Synthesis of control HER electrode material:
2mg of commercial Pt/C was weighed and dispersed in a mixed solution (deionized water 500. Mu.L, ethanol 500. Mu.L and Nafion solution 30. Mu.L), and sonicated for 10min to obtain a dispersion.
And (3) selecting NF in the step (1), dripping 100uL of dispersion liquid, rapidly transferring to a vacuum drying oven, and drying at 80 ℃ for 12 hours to obtain the alkaline electrolyzed water catalyst Pt/C.
Example 2.
The specific operation steps are as follows:
(1) Pretreatment of a substrate: cutting foam Nickel (NF) into rectangle with the length of 1X 1.5cm, and cleaning with acetone, hydrochloric acid, deionized water and ethanol under ultrasonic wave for 15min. And then drying the NF to obtain the catalyst substrate.
(2) Synthesis of LF-0.1:
Fe (NO 3)3·9H2O(1.5mmol)、La(NO3)3·6H2 O (0.15 mmol) and C 6H5Na3O7·2H2 O (1.5 mmol) were dissolved in 40mL high-purity water and sonicated for 15min to give a reaction solution.
Immersing NF treated in the step (1) as a working electrode in a reaction solution to perform 100 times of Cyclic Voltammetry (CV) electrodeposition within a potential range of-1.2 to 0.4Vvs. And (3) flushing the electrode material after the reaction is finished by using high-purity water and absolute ethyl alcohol, and rapidly transferring the electrode material to a vacuum drying oven for drying at 75 ℃ for 14 hours to obtain an alkaline electrolyzed water catalyst LF-0.1.
(3) Synthesis of LF-0.2:
Fe (NO 3)3·9H2O(1.5mmol)、La(NO3)3·6H2 O (0.30 mmol) and C 6H5Na3O7·2H2 O (1.5 mmol) were dissolved in 40mL high-purity water and sonicated for 15min to give a reaction solution.
Immersing NF treated in the step (1) as a working electrode in a reaction solution to perform 100 times of Cyclic Voltammetry (CV) electrodeposition within a potential range of-0.4-0.8 Vvs. And (3) flushing the electrode material after the reaction is finished by using high-purity water and absolute ethyl alcohol, and rapidly transferring the electrode material to a vacuum drying oven for drying at 85 ℃ for 10 hours to obtain an alkaline electrolyzed water catalyst LF-0.2.
(4) Synthesis of LF-0.4:
Fe (NO 3)3·9H2O(1.5mmol)、La(NO3)3·6H2 O (0.60 mmol) and C 6H5Na3O7·2H2 O (1.5 mmol) were dissolved in 40mL high-purity water and sonicated for 15min to give a reaction solution.
Immersing NF treated in the step (1) as a working electrode in a reaction solution to perform 100 times of Cyclic Voltammetry (CV) electrodeposition within a potential range of-1.2-0.2 Vvs. And (3) flushing the electrode material after the reaction is finished by using high-purity water and absolute ethyl alcohol, and rapidly transferring the electrode material to a vacuum drying oven for drying at 83 ℃ for 11 hours to obtain an alkaline electrolyzed water catalyst LF-0.4.
Example 3.
The catalysts of different proportions of alkaline electrolyzed water catalyst LaOOH/Fe 3O4 obtained in example 1 were subjected to X-ray detection and the results are shown in FIG. 1. As can be seen from fig. 1, in addition to the main diffraction peaks from the (111), (200) and (220) planes of the NF substrate, the F electrode exhibits three typical peaks at 23.7 °, 25.0 ° and 29.2 °, corresponding to the (222), (302) and (322) crystal planes (green line in fig. 1) of Fe 3O4, respectively. After introduction of La, a distinct peak appears at 27.3 ° which belongs to the (011) plane of LaOOH. At the same time, the intensity of the (222) and (302) planes of Fe 3O4 was reduced, while the (322) plane was disappeared (red line), indicating that the addition of La caused a different exposed crystal plane of Fe 3O4.
Example 4.
The alkaline electrolyzed water catalyst LF-0.3 prepared in example 1 was observed for morphology and lattice fringes. It was found that LF-0.3 exhibited a predominantly lamellar structure, and with La addition (FIG. 2), the (011) face of LaOOH and the (220) and (311) faces of Fe 3O4 were predominantly exposed at the surface. The formation of a hetero-interface is demonstrated by lattice epitaxy and the co-existence of Fe 3O4 and LaOOH planes within the same selected region.
Example 5.
The alkaline electrolyzed water catalyst LF-0.3 prepared in example 1 is subjected to OER reaction for 100h to obtain a catalyst with a reconstructed surface. As can be seen from FIG. 3, the main structure is unchanged after OER-100h, but all the main peaks are shifted to the left, due to the formation of new compounds on the surface. In addition, the intensity of LaOOH (011) plane characteristic peak is also weakened. It was demonstrated that surface reconstitution during OER reactions produced new reactive species.
Example 6.
The alkaline electrolyzed water catalyst LF-0.3 prepared in example 1 was subjected to OER reaction for 100 hours to obtain a catalyst with a surface reconstruction. After the reaction, a clearly contrasting hydroxide layer was observed at the surface of LF-0.1, mainly comprising the (002) plane of FeOOH (FIG. 4). While the (220) and (400) planes of Fe 3O4 remain in LF-0.1. FFT spectral analysis was performed in the lattice epitaxy and coexistence regions, and the results indicated that the heterojunction structure was stably present by the presence of these crystal planes (FIG. 4: B1, B2). Thus, during OER stability testing, the Fe 3O4 and LaOOH on the surface undergo structural reconfiguration changes and FeOOH is formed on the surface.
Example 7.
The contact angles of the alkaline electrolyzed water catalysts LF-0.3, L and F obtained in example 1 were measured to obtain the surface wettability of the prepared electrode material. It can be seen from fig. 5 that only LF-0.1 showed complete penetration of water droplets after 250 ms. In contrast, F and L retain water droplets on their surfaces. Contact angles of F, LF-0.1 and L at 85ms were determined to be 127.5 °, 61 °, 101.5 °, 98 ° and 118 °, respectively. This shows that LF-0.1 has a higher wettability for mass transfer of the electrolyte.
Example 8.
OER test was performed in alkaline 1M KOH solution using the alkaline electrolyzed water catalyst prepared in example 1 as the working electrode, hg/HgO as the reference electrode, and Pt sheet as the counter electrode. As a result, the over potential of LF-0.1 was 350mV, the current density was 500mA cm -2, and it was about 100mV lower than F (444 mV), as shown in FIG. 6 a. Furthermore, of the catalysts prepared and commercial RuO 2, the LF-0.1 had a minimum Tafil slope of 121.08mV/dec (FIG. 6 b), indicating superior OER kinetics. The present invention considers that Fe 3O4 (LF-0.1) lightly doped with La always shows the lowest overpotential at low, medium, and high current densities (193, 265, and 350 mV).
Example 9.
HER testing was performed in alkaline 1M KOH solution, with the catalyst prepared in example 1 as the working electrode, hg/HgO as the reference electrode, and graphite rod as the counter electrode. As a result, as shown in FIG. 7a, LF-0.1 only requires 101mV to achieve a current density of 100mA cm -2. In contrast, the overpotential for NF, F, LF-0.3, LF-0.5, and L were 475, 300280, 301, and 324mV, respectively. As can be seen in FIG. 7b, the Taphillips for NF, F, LF-0.1, LF-0.3, LF-0.5, and L are 958.91, 374.49, 309.42, 306.98, 322.75, and 439.60mV/dec, respectively. The tafel slope of LF-0.1 is smaller, which corresponds to HER reaction kinetics enhancement.
Example 10.
OER stability test was performed in alkaline 1M KOH solution using the alkaline electrolyzed water catalyst LF-0.1 prepared in example 1 as the working electrode, hg/HgO as the reference electrode, and Pt plate as the counter electrode. After a long-term test at 500mA cm -2 for 100 hours, the attenuation rate was 4.1% (FIG. 8). The catalyst has good efficiency and stability under alkaline conditions.
From the examples of the present invention, the present invention utilizes a one-step electrodeposition process to self-support LaOOH/Fe 3O4 on nickel foam and carefully control the ratio of LaOOH to Fe 3O4. When the ratio LaOOH/Fe 3O4 is low, the obtained LF-0.1 has the characteristics of surface roughness and porosity. In alkaline electrolyte, LF-0.1 had OER and HER activities of 350mV (η500) and 101mV (η100), respectively. Notably, LF-0.1 exhibited an impressive OER stability with a decay rate of only 4.1% after 100 hours of maintaining a current density of 500mA cm -2. The applied voltages were 1.44V (. Eta.10), 1.71V (. Eta.100) and 1.85V (. Eta.500) by the full water splitting test, respectively. On the nanoscale, the formation of the heterojunction promotes electron redistribution between LaOOH and Fe 3O4, thereby promoting the overall water splitting reaction. On a microscopic scale, the LF-0.1 material has smaller water drop contact angle and desorption hydrogen diameter, and larger underwater bubble contact angle, which has obvious advantages for the whole water diversion reaction. The hydrophilicity and hydrophobicity allow the electrode to be in sufficient contact with the electrolyte to obtain the desired intermediate product while ensuring rapid separation of hydrogen bubbles from the electrode surface. Provides a better embodiment for preparing the catalyst for producing hydrogen by electrolyzing water under high current density.
The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the embodiment of the present invention in any way, but any simple modification, equivalent variation and modification of the above embodiment according to the technical substance of the embodiment of the present invention still fall within the scope of the technical solution of the embodiment of the present invention.
Claims (10)
1. The preparation method of the alkaline electrolyzed water catalyst with the iron-based heterostructure is characterized by comprising the following steps of: dissolving ferric salt, lanthanum salt and sodium citrate in water to obtain a reaction solution; immersing foam nickel serving as a working electrode in the reaction solution to perform electrodeposition reaction; and washing and drying the working electrode after the reaction is finished to obtain the alkaline electrolyzed water catalyst.
2. The method according to claim 1, wherein,
The foam nickel is pretreated and then used as a working electrode;
The pretreatment process comprises the following steps: the foam nickel is respectively cleaned by acetone, hydrochloric acid, deionized water and ethanol under ultrasonic wave and then dried.
3. The method according to claim 1, wherein,
The mol ratio of the ferric salt to the lanthanum salt to the sodium citrate is 10: 1-5:1;
The ferric salt is ferric nitrate;
The lanthanum salt is lanthanum nitrate.
4. A process according to claim 3, wherein,
The ferric salt is Fe (NO 3)3·9H2 O;
The lanthanum salt is La (NO 3)3·6H2 O;
Sodium citrate is C 6H5Na3O7·2H2 O.
5. The method according to claim 1, wherein,
The conditions of the electrodeposition reaction are as follows: and (3) carrying out electrodeposition reaction within the potential range of-1.2-0.8V vs. Hg/HgO.
6. The method according to claim 5, wherein,
The conditions of the electrodeposition reaction are as follows: 100 cyclic voltammetric electrodeposits were performed.
7. The method according to claim 1, wherein,
And washing the working electrode after the reaction is finished by using high-purity water and absolute ethyl alcohol, and drying the working electrode at 75-85 ℃ for 10-14 h.
8. The method according to claim 8, wherein,
The working electrode after the reaction was washed with high-purity water and absolute ethanol, and dried at 80℃for 12 hours.
9. An iron-based heterostructure alkaline electrolyzed water catalyst, characterized in that it is prepared by the preparation method of any one of claims 1 to 8.
10. Use of the alkaline electrolyzed water catalyst of claim 9 in an oxygen evolution reaction.
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