Electrocatalytic oxygen evolution material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of water electrolysis hydrogen production, in particular to an electrocatalytic oxygen evolution material and a preparation method and application thereof. In order to solve the technical problems that an existing precious metal-based OER catalyst is high in cost, and a transition metal-based catalyst is poor in conductivity and insufficient in stability, the NiFe layered double hydroxides (NiFe-LDHs) and CeZrOx solid solution heterojunction composite material is provided, and the activity and stability of the OER are remarkably improved through a heterojunction and oxygen vacancy synergistic mechanism.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production by electrolyzing water, and particularly to an electrocatalytic oxygen evolution material, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of the hydrogen energy economy, the electrolytic water hydrogen production technology has become the core approach for large-scale production of green hydrogen. However, the sluggish kinetics of the anodic oxygen evolution reaction (OER) requires a high overpotential for driving, which severely restricts the overall energy conversion efficiency. Currently, commercial OER catalysts are mainly RuO2 and IrO2, but precious metal resources are scarce and the cost is high, making it difficult to meet the demands of large-scale applications. In recent years, transition metal-based catalysts (such as NiFe-LDHs) have received extensive attention due to their low cost and high activity, but problems such as poor intrinsic conductivity and insufficient structural stability have not been solved yet.

[0003] Research shows that doping some oxides (such as CeO2, ZrO2) can optimize the OER performance by regulating the oxygen vacancy concentration and electronic structure. The solid solution of CeO2 and ZrO2 (CeZrO x ) has unique oxygen storage capacity and high oxygen vacancy density, but its conductivity is limited when used alone. If CeZrO x is compounded with highly active NiFe-LDHs to construct a heterojunction interface, it is expected to achieve the synergistic effects of interfacial charge rearrangement, increased active site density, and enhanced structural stability. Summary of the Invention

[0004] The present invention provides an electrocatalytic oxygen evolution material, a preparation method thereof, and an application thereof. An OER catalyst obtained by electro-depositing NiFe-LDHs on a nickel foam substrate and hydrothermally compounding with a CeZrO x solid solution significantly improves the OER activity and stability through the synergistic effect of the double-metal layered hydroxide and the solid solution.

[0005] The principle of the present invention is to introduce a small amount of CeZrO x solid solution to construct a heterojunction interface with NiFe-LDHs, enhance the active sites, and significantly improve the activity and stability of the electrocatalytic oxygen evolution reaction. Secondly, the ionic radius difference between Ce x / Ce 3+ and Zr 4+ in the CeZrO 4+ solid solution causes lattice distortion, forming a high density of oxygen vacancies. These oxygen vacancies, as the key active sites of the OER reaction, directly participate in the adsorption and conversion of intermediates (*OH, *O, *OOH). In the LOM mechanism, the oxygen vacancies supplement the lattice oxygen lost in the reaction through dynamic migration, inhibit the passivation of active sites, and at the same time, the strong oxygen migration ability of the CeZrO x solid solution accelerates the regeneration of oxygen vacancies, maintaining the continuous activity of the catalytic reaction.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides an electrocatalytic oxygen evolution material, comprising NiFe layered double hydroxide and CeZrO solid solution with oxygen vacancies compounded on its surface, and the composite interface between the NiFe layered double hydroxide and the CeZrO solid solution has a heterojunction structure. x CeZrO x

[0008] The present invention provides a preparation method of an electrocatalytic oxygen evolution material, comprising:

[0009] S1. Using a nickel source, an iron source, and urea as raw materials, growing NiFe layered double hydroxide on the surface of a current collector by electrodeposition to obtain a precursor material A;

[0010] S2. After mixing a cerium source, a zirconium source, and the precursor material A in a solvent, adding a complexing agent and carrying out an aging reaction to obtain a precursor material B, and then performing hydrothermal treatment on the precursor material B to obtain the electrocatalytic oxygen evolution material.

[0011] The present invention provides an electro-deposition-hydrothermal composite oxygen evolution reaction (OER) catalyst based on a nickel foam substrate, and its core lies in constructing an efficient catalytic system through the synergistic effect of a double-metal layered hydroxide and a rare earth solid solution.

[0012] Specifically, the catalyst uses nickel foam as a substrate, and NiFe layered double hydroxide nanosheet arrays are grown on the surface by electrodeposition. Subsequently, CeZrO solid solution is loaded on its surface by hydrothermal method to form a composite structure with a heterojunction interface. The thickness of the NiFe-LDHs nanosheets is controlled within the range of 50 - 200 nm, and the size of the CeZrO is 20 - 50 nm. The two are closely combined to optimize the interfacial charge transfer efficiency. During the preparation process, first, an electrolyte containing nickel nitrate, iron nitrate, and urea is prepared, and NiFe-LDHs nanosheet arrays are formed on the surface of nickel foam by constant voltage electrodeposition; subsequently, cerium nitrate and zirconium oxychloride are used as precursors, and citric acid is used as a complexing agent to compound CeZrO under hydrothermal conditions x to regulate the interfacial electronic structure. Through the synergistic effect of the NiFe-LDHs and the CeZrO, the OER activity and stability of the composite material are significantly improved. Among them, the interfacial oxygen vacancies optimize the adsorption ability of intermediates, and the heterojunction interface promotes charge separation. Experimental results show that in 1 M KOH solution, this catalyst has a current density of 100 mA / cm x x CeZrO x 2 ​​​The overpotential is as low as 251 mV, and the activity retention rate is greater than 95% after continuous electrolysis for 100 hours, showing excellent electrocatalytic performance and potential for industrial applications.

[0013] Preferably, in S1, the current collector is nickel foam; the thickness of the nickel foam is 0.5 - 1 mm, the pore density is 100 - 130 PPI, and the pore diameter is 0.1 - 0.3 mm.

[0014] Preferably, in S1, the nickel source includes nickel nitrate and / or nickel chloride, the iron source includes iron nitrate and / or iron chloride, and the molar ratio of nickel in the nickel source to iron in the iron source is (1 - 3):1.

[0015] Preferably, the concentration of the nickel source is 0.1 - 0.3 M.

[0016] Preferably, the concentration of the iron source is 0.05 - 0.15 M.

[0017] Preferably, in S1, the concentration of the urea is 0.5 - 1.5 M.

[0018] Preferably, in S1, the conditions of the electrodeposition method are: the voltage is 1.5 - 2.5 V, and the deposition reaction is carried out at 50 - 80 °C for 1 - 3 h.

[0019] Preferably, in S1, the nickel source, the iron source, and urea are first dissolved in a solvent; the solvent for dissolution is at least one of deionized water, ethanol, methanol, and N,N-dimethylformamide.

[0020] Preferably, in S1, after the electrodeposition reaction, NiFe-LDHs are obtained after cleaning to remove impurities and then drying. Preferably, the cleaning reagent is deionized water and / or ethanol.

[0021] Preferably, in S2, the cerium source includes cerium nitrate, the zirconium source includes zirconium oxychloride, and the molar ratio of cerium in the cerium source to zirconium in the zirconium source is (1 - 3):1.

[0022] Preferably, in S2, the complexing agent is citric acid, and the aging reaction time is 8 - 12 h.

[0023] Preferably, in S2, the hydrothermal temperature is 160 - 200 °C, and the hydrothermal time is 5 - 10 h.

[0024] Preferably, in S2, the cerium source, the zirconium source, and the precursor material A are mixed in anhydrous ethanol.

[0025] An OER catalyst includes the above electrocatalytic oxygen evolution material or the electrocatalytic oxygen evolution material prepared by the above preparation method.

[0026] Therefore, the present invention has the following beneficial effects:

[0027] (1) The present invention provides a nickel foam substrate. NiFe-LDHs nanosheet arrays are prepared by an electrodeposition method, and then CeZrO x solid solution is compounded by a hydrothermal method to form a heterojunction and oxygen vacancy structure. Thereby, the catalytic activity and stability can be improved, the conductivity and active site density of NiFe-LDHs-based catalysts can be enhanced, and the electrocatalytic oxygen evolution performance can be synergistically enhanced.

[0028] (2) The present invention uses low-cost raw materials such as cerium sources and zirconium sources, combines the mature hydrothermal method and electrodeposition method, and has good scalability. The use of precious metals (such as Ru, Ir) is avoided, and the total cost is reduced by more than 80% compared with IrO2, which is suitable for large-scale industrial production. Description of the Drawings

[0029] Figure 1 is the LSV polarization curve;

[0030] Figure 2 is the stability test curve. Detailed Embodiments

[0031] The present invention will be further described below in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following descriptions are usually only a part of the embodiments of the present invention, rather than all the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention shall fall within the scope of protection of the present invention.

[0032] Example 1 CeZrO x / NiFe-LDHs / NF Composite Electrode

[0033] (1) Preparation of NiFe-LDHs / NF: Nickel nitrate hexahydrate (Ni(NO3)2·6H2O, 0.3 M), iron nitrate nonahydrate (Fe(NO3)3·9H2O, 0.1 M), urea (CH4N2O, 1 M), and the solvent is deionized water to prepare the electrolyte; at room temperature, on the current collector of nickel foam (commercially available, thickness 1 mm, areal density 550, pore diameter 0.2 mm, pore density 110, purity above 99.9%, size 1×1 cm 2)Ultrasonic for 1 min with 1M HCl solution to remove the possible oxide layer, then ultrasonic for 1 min and 5 min with ethanol and deionized water respectively to remove organic pollutants and water-soluble impurities, and obtain the pretreated nickel foam (NF). Using the pretreated nickel foam as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, electro-deposit at a constant voltage of 2V in an 80°C water bath for 2 hours. After electro-deposition, rinse with deionized water and dry in vacuum at 60°C.

[0034] (2) Gel composite CeZrO x : Dissolve cerium nitrate (Ce(NO3)3·6H2O, 0.1M) and zirconium oxychloride (ZrOCl2·8H2O, 0.05M) in anhydrous ethanol according to the ratio of n(Ce 3+ ):n(Zr 4+ ) = 2:1. Immerse the prepared NiFe-LDHs / NF into the above-mentioned CeZrO x precursor solution. Then add 0.1M citric acid as a complexing agent and stir until a transparent sol is formed, and age for 10 hours.

[0035] (3) Preparation of CeZrO x / NiFe-LDHs / NF composite electrode: Transfer the sol to a 100 mL Teflon-lined stainless steel autoclave. Place the autoclave in an electric furnace at 180°C. After reacting for 7h, wait for the reaction system to cool to room temperature. Wash the final product with deionized water and anhydrous ethanol several times to remove any possible ions; dry naturally at room temperature to obtain the CeZrO x / NiFe-LDHs / NF composite electrode.

[0036] Comparative example 1 CeO2 / NiFe-LDHs / NF composite electrode

[0037] (1) Preparation of NiFe-LDHs / NF: Nickel nitrate hexahydrate (Ni(NO3)2·6H2O, 0.3M), iron nitrate nonahydrate (Fe(NO3)3·9H2O, 0.1M), urea (CH4N2O, 1M), with deionized water as the solvent, configure the electrolyte; use the pretreated nickel foam as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, electro-deposit at a constant voltage of 2V in an 80°C water bath for 2 hours. After electro-deposition, rinse with deionized water and dry in vacuum at 60°C.

[0038] (2) Gel composite CeZrO x : Dissolve cerium nitrate (Ce(NO3)3·6H2O, 0.1M) in anhydrous ethanol. Immerse the prepared NiFe-LDHs / NF into the above-mentioned precursor solution. Then add 0.1M citric acid as a complexing agent and stir until a transparent sol is formed, and age for 10 hours.

[0039] (3) Preparation of CeO2 / NiFe-LDHs / NF composite electrode: Transfer the sol to a 100 mL Teflon-lined stainless steel autoclave. Place the autoclave in an electric furnace at 180 °C and react for 7 h. After the reaction system cools to room temperature, wash the final product several times with deionized water and absolute ethanol to remove any possible ions; air-dry it naturally at room temperature to obtain the CeO2 / NiFe-LDHs / NF composite electrode.

[0040] Comparative Example 2 ZrO2 / NiFe-LDHs / NF composite electrode

[0041] (1) Preparation of NiFe-LDHs / NF: Dissolve nickel nitrate hexahydrate (Ni(NO3)2·6H2O, 0.3 M), iron nitrate nonahydrate (Fe(NO3)3·9H2O, 0.1 M), and urea (CH4N2O, 1 M) in deionized water as the solvent to prepare the electrolyte; use the pretreated nickel foam as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, and electro-deposit at a constant voltage of 2 V in an 80 °C water bath for 2 h. After electro-deposition, rinse with deionized water and dry in a vacuum at 60 °C.

[0042] (2) Gel composite with ZrO2: Dissolve zirconium oxychloride (ZrOCl2·8H2O, 0.05 M) in absolute ethanol, and immerse the prepared NiFe-LDHs / NF in the above precursor solution. Then add 0.1 M citric acid as a complexing agent and stir until a transparent sol is formed, and age for 10 h.

[0043] (3) Preparation of ZrO2 / NiFe-LDHs / NF composite electrode: Transfer the sol to a 100 mL Teflon-lined stainless steel autoclave. Place the autoclave in an electric furnace at 180 °C and react for 7 h. After the reaction system cools to room temperature, wash the final product several times with deionized water and absolute ethanol to remove any possible ions; air-dry it naturally at room temperature to obtain the ZrO2 / NiFe-LDHs / NF composite electrode.

[0044] Comparative Example 3 NiFe-LDHs / NF composite electrode

[0045] (1) Preparation of NiFe-LDHs / NF: Dissolve nickel nitrate hexahydrate (Ni(NO3)2·6H2O, 0.3 M), iron nitrate nonahydrate (Fe(NO3)3·9H2O, 0.1 M), and urea (CH4N2O, 1 M) in deionized water as the solvent to prepare the electrolyte; use the pretreated nickel foam as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, and electro-deposit at a constant voltage of 2 V in an 80 °C water bath for 2 h. After electro-deposition, rinse with deionized water and dry in a vacuum at 60 °C.

[0046] Comparative Example 4 NiFe-LDHs / CeZrO x / NF composite electrode

[0047] (1) Gel composite CeZrO x / NF: Dissolve cerium nitrate (Ce(NO3)3·6H2O, 0.1M) and zirconium oxychloride (ZrOCl2·8H2O, 0.05M) in absolute ethanol according to the ratio of n(Ce 3+ ):n(Zr 4+ ) = 2:1. Immerse nickel foam into the above CeZrO x precursor solution. Then add 0.1M citric acid as a complexing agent and stir until a transparent sol is formed. Age for 10 hours.

[0048] (2) Preparation of CeZrO x / NF composite electrode: Transfer the sol to a 100 mL Teflon-lined stainless steel autoclave. Place the autoclave in an electric furnace at 180 °C. After reacting for 7 h, wait for the reaction system to cool to room temperature. Wash the final product several times with deionized water and absolute ethanol to remove any possible ions; air dry naturally at room temperature to obtain the CeZrO x / NF composite electrode.

[0049] (3) Preparation of NiFe-LDHs / CeZrO x / NF composite electrode: Nickel nitrate hexahydrate (Ni(NO3)2·6H2O, 0.3M), iron nitrate nonahydrate (Fe(NO3)3·9H2O, 0.1M), urea (CH4N2O, 1M), with deionized water as the solvent, prepare the electrolyte; use the CeZrO x / NF composite electrode as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode. Electrodeposit at a constant voltage of 2V in an 80 °C water bath for 2 hours. After electrodeposition, rinse with deionized water and dry in vacuum at 60 °C.

[0050]

Performance Test

[0051] Perform performance tests on the final products obtained in Example 1 and Comparative Examples 1-4, and the results are as Figures 1 to 2 shown. To confirm the influence of CeZrO x and the heterojunction on the electrocatalytic performance, polarization curves are carried out in an alkaline medium to evaluate the OER performance. Polarization curves are carried out in 1M KOH to estimate the OER activity. As Figure 1 shown, the current density of the electrodeposited NiFe-LDHs / NF (Comparative Example 3) at 100 mA / cm 2 (η 100 ) is 392 mV, while Comparative Example 2 has an overpotential at η 100 and Comparative Example 1 has an overpotential at η 100The overpotentials are 356 mV and 365 mV, showing little improvement compared to Comparative Example 3, indicating that individual CeO2 and ZrO2 do not play an obvious role in electrocatalysis.

[0052] More significantly, the η of the CeZrO x / NiFe-LDHs / NF composite electrode (Example 1) 100 is significantly reduced compared to Comparative Example 3, indicating that the unique oxygen vacancy regulation ability of the CeZrO x solid solution, and the formation of a heterojunction with NiFe-LDHs further enhances the active sites, significantly improving the OER performance. At the same time, its stability is also tested. After continuous electrolysis for 100 hours, the activity retention rate is greater than 95%, indicating that the CeZrO x solid solution structure inhibits the dissolution of NiFe-LDHs in the alkaline environment, improving the stability of the catalyst. For NiFe-LDHs / CeZrO x / NF (Comparative Example 4), due to the reversed preparation order (first composite CeZrO x and then deposit LDHs), because the CeZrO x solid solution has poor conductivity, and the subsequent electrodeposition of NiFe-LDHs leads to insufficient conductivity, limited active sites, and a decrease in performance. The overpotential further increases to 435 mV.

Claims

1. An electrocatalytic oxygen evolution material, characterized in that, Including NiFe layered double hydroxide and CeZrO solid solution with oxygen vacancies compounded on its surface, the composite interface between NiFe layered double hydroxide and CeZrO solid solution has a heterojunction structure. x solid solution, the composite interface between NiFe layered double hydroxide and CeZrO x solid solution has a heterojunction structure.

2. A preparation method of an electrocatalytic oxygen evolution material, characterized in that, Comprising: S1. Using a nickel source, an iron source, and urea as raw materials, growing NiFe layered double hydroxide on the surface of a current collector by electrodeposition to obtain precursor material A; S2. After mixing a cerium source, a zirconium source, and precursor material A in a solvent, adding a complexing agent and subjecting to an aging reaction to obtain precursor material B, and then performing hydrothermal treatment on precursor material B to obtain an electrocatalytic oxygen evolution material.

3. The preparation method according to claim 2, characterized in that, In S1, the current collector is nickel foam; the thickness of the nickel foam is 0.5 - 1 mm, the pore density is 100 - 130 PPI, and the pore diameter is 0.1 - 0.3 mm.

4. The preparation method according to claim 2, characterized in that, In S1, the nickel source includes nickel nitrate and / or nickel chloride, the iron source includes iron nitrate and / or iron chloride, and the molar ratio of nickel in the nickel source to iron in the iron source is (1 - 3):

1.

5. The preparation method according to claim 2 or 4, characterized in that, In S1, the concentration of urea is 0.5 - 1.5 M.

6. The preparation method according to claim 2, wherein In S1, the conditions of the electrodeposition method are: the voltage is 1.5 - 2.5 V, and the deposition reaction is carried out at 50 - 80 °C for 1 - 3 h.

7. The preparation method according to claim 2, wherein In S2, the cerium source includes cerium nitrate, the zirconium source includes zirconium oxychloride, and the molar ratio of cerium in the cerium source to zirconium in the zirconium source is (1 - 3):

1.

8. The preparation method according to claim 2, characterized in that, In S2, the complexing agent is citric acid, and the time of the aging reaction is 8 - 12 h.

9. The preparation method according to claim 2, characterized in that, In S2, the hydrothermal temperature is 160 - 200 °C, and the hydrothermal time is 5 - 10 h.

10. An OER catalyst, characterized in that, Comprising the electrocatalytic oxygen evolution material as described in claim 1 or the electrocatalytic oxygen evolution material prepared by the preparation method as described in any one of claims 2 - 9.

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