阅读说明：本技术 低结晶度的锆掺杂的钴铁层状双氢氧化物的制备方法及其应用于电解水制氢 (Preparation method of zirconium-doped cobalt-iron layered double hydroxide with low crystallinity and application of zirconium-doped cobalt-iron layered double hydroxide in hydrogen production by wate) 是由 包健 李倩 江坤 于 2021-06-11 设计创作，主要内容包括：本发明属于功能化纳米电极材料技术领域,涉及一种低结晶度的锆掺杂的钴铁层状双氢氧化物的制备方法,包括：将二价钴源、三价铁源、四价锆源溶于硝酸钾的去离子水溶液中,以恒定速度搅拌,使其充分混合均匀；经预处理的基底NF置于溶液中,以三电极系统进行沉积负电位的恒定电压电沉积600～1200s；所制得材料洗涤后60～80℃真空干燥2～4 h,即得。本发明还将将所制得的低结晶度的锆掺杂的钴铁层状双氢氧化物,用作电解水的阳极和阴极,应用于电解水制氢,本发明所公开的制备方法简单易操作,原料来源广,价格低廉,反应温和,对环境友好；所制备的催化剂具有较高双功能的电催化活性,可应用于海水的全解水电催化剂,也可用于淡化海水。(The invention belongs to the technical field of functionalized nano electrode materials, and relates to a preparation method of zirconium-doped cobalt-iron layered double hydroxide with low crystallinity, which comprises the following steps: dissolving a divalent cobalt source, a trivalent iron source and a tetravalent zirconium source in a deionized water solution of potassium nitrate, and stirring at a constant speed to fully and uniformly mix the divalent cobalt source, the trivalent iron source and the tetravalent zirconium source; placing the pretreated substrate NF in a solution, and carrying out constant voltage electrodeposition with negative potential for 600-1200 s by using a three-electrode system; and washing the prepared material, and then drying the washed material in vacuum at the temperature of between 60 and 80 ℃ for 2 to 4 hours to obtain the material. The prepared zirconium-doped cobalt-iron layered double hydroxide with low crystallinity is used as an anode and a cathode of electrolyzed water and is applied to hydrogen production by the electrolyzed water; the prepared catalyst has high bifunctional electrocatalytic activity, can be applied to a full-electrolysis water catalyst of seawater, and can also be used for desalting seawater.)

1. A preparation method of zirconium-doped cobalt iron layered double hydroxide with low crystallinity is characterized by comprising the following steps:

(1) dissolving a divalent cobalt source, a trivalent iron source and a tetravalent zirconium source in a deionized water solution of potassium nitrate, and stirring at a constant speed to fully and uniformly mix the divalent cobalt source, the trivalent iron source and the tetravalent zirconium source, wherein the divalent cobalt source: a ferric iron source: tetravalent zirconium source: potassium nitrate: the solid-liquid ratio of the deionized water is 1-3 mmol: 1-3 mmol: 1-3 mmol: 0.2-0.4 mmol: 100-150 mL;

(2) placing the pretreated substrate NF into a solution, and carrying out negative potential constant voltage electrodeposition for 600-1200 s by using a three-electrode system, wherein a Pt electrode, an Ag/AgCl electrode and the NF are respectively used as a counter electrode, a reference electrode and a working electrode;

(3) the prepared material is washed by deionized water and ethanol for multiple times, and is dried in vacuum at the temperature of 60-80 ℃ for 2-4 h, preferably at the temperature of 60 ℃ for 2h, so that the low-crystallinity zirconium-doped cobalt-iron layered double hydroxide which is dried and in-situ grown on NF is obtained.

2. The method for preparing a zirconium-doped cobalt iron layered double hydroxide with low crystallinity as claimed in claim 1, wherein: the divalent cobalt source in the step (1): a ferric iron source: tetravalent zirconium source: potassium nitrate: the solid-liquid ratio of the deionized water is 2 mmol: 2 mmol: 2 mmol: 0.3 mmol: 100 mL.

3. The method for preparing a zirconium-doped cobalt iron layered double hydroxide with low crystallinity as claimed in claim 1, wherein: in the step (1), the divalent cobalt source is one or a mixture of cobalt chloride, cobalt nitrate and hydrate thereof; the ferric iron source is one or a mixture of ferric chloride, ferric nitrate and hydrate thereof; the tetravalent zirconium source is one or a mixture of zirconium chloride, zirconium nitrate and hydrates thereof.

4. The method for preparing a zirconium-doped cobalt iron layered double hydroxide with low crystallinity as claimed in claim 1, wherein: and (3) putting the pretreated substrate NF in the step (2) into nitric acid to clean surface impurities and remove oxides.

5. The method for preparing a zirconium-doped cobalt iron layered double hydroxide with low crystallinity as claimed in claim 1, wherein: the electrodeposition time in the step (2) is 900 s.

6. The method for preparing a zirconium-doped cobalt iron layered double hydroxide with low crystallinity as claimed in claim 1, wherein: in the step (2), the area of the electrodeposited material is 1cm²。

7. The method for preparing a zirconium-doped cobalt iron layered double hydroxide with low crystallinity as claimed in claim 1, wherein: and (4) washing in the step (3) by using deionized water for 2 times, and then washing by using absolute ethyl alcohol for 2 times.

8. A zirconium-doped cobalt iron layered double hydroxide with low crystallinity prepared by the process according to any one of claims 1 to 7.

9. Use of the low crystallinity zirconium doped cobalt iron layered double hydroxide according to claim 8 wherein: it is used as a bifunctional electrolysis catalyst and is used as an anode and a cathode for electrolyzing water.

10. Use of a zirconium doped cobalt iron layered double hydroxide of low crystallinity according to claim 9, characterized in that: it is used as an anode and a cathode for electrolyzing seawater.

Technical Field

The invention belongs to the technical field of functionalized nano electrode materials, relates to an electrocatalyst, and particularly relates to a preparation method of a zirconium-doped cobalt-iron layered double hydroxide with low crystallinity and application of the zirconium-doped cobalt-iron layered double hydroxide in water electrolysis hydrogen production.

Background

Hydrogen has recently received much attention in the energy field as a renewable, pollution-free, clean energy source. In the field of hydrogen production, electrocatalytic water splitting hydrogen production is considered a promising and low-cost strategy. Electrolyzed water contains an anodic Oxygen Evolution Reaction (OER) and a cathodic Hydrogen Evolution Reaction (HER), but the four-electron reaction kinetics of OER are slow, hindering the efficiency of electrocatalytic water decomposition. Currently, platinum-based noble metals are excellent HER catalysts, with ruthenium, iridium, and alloys thereof exhibiting high OER performance. However, the scarcity, high price and poor stability of noble metals greatly limit their large-scale application. Therefore, it is important to design a low cost bifunctional electrocatalyst capable of simultaneously promoting the OER and HER processes. Compared with high-purity water used for water electrolysis, if seawater with the earth water content of 97% is used as an electrolyte raw material, the application range of hydrogen production by water electrolysis can be further expanded, and the cost can be further reduced.

In recent years, non-noble metal catalysts have shown great potential, including transition metal oxides, hydroxides, oxyhydroxides, phosphides, and chalcogenides. Among them, Layered Double Hydroxides (LDHs) have been widely studied as an OER catalyst for electrocatalytic water decomposition. The LDHs have a two-dimensional layered structure, are composed of a cation layer of metal hydroxide and anions for balancing interlayer charges, and have the advantages of adjustable interlayer cations and interlayer anions and rich and adjustable valence states. To achieve good electrocatalytic activity, the structure of the LDHs needs to be further optimized. Research shows that the cation can regulate the 3d energy level of the electrocatalyst, strengthen the electronic interaction and regulate the surface adsorption energy of the intermediate, so that LDHs are doped with Mo in high valence state⁶⁺、V⁵⁺And Cr^3+/6+Has attracted the attention of scholars. And Zr is a rare earth-rich element having different valence states (+2, +3, and +4), Zr⁴⁺Is in a stable oxidation state and can be used as a dopant to improve the catalytic performance. Adding Zr⁴⁺Doping with LDHs to form a low crystallinity material, and application as a bifunctional electrocatalyst for OER and HER has not been reported, the formed low crystallinity material is capable of exposing more active sites and contributing to defect formation, thereby enhancing electrocatalytic activity. On the other hand, three-dimensional porous foam Nickel (NF) is used asThe electro-catalytic material grown on the conductive substrate can not only enhance the conductivity of the catalyst, but also enlarge the active surface area, and is beneficial to further enhancing the catalytic activity of the catalyst.

For full water splitting, in combination with the above strategy, developing a zirconium-doped CoFe-LDH low crystallinity material grown on NF will provide a new idea for the design of seawater electrocatalysts.

Disclosure of Invention

Aiming at the current situation that efficient and cheap bifunctional electrocatalysts are urgently needed to be found in electrocatalysis decomposition water at present, the invention aims to provide a preparation method of a zirconium-doped cobalt-iron layered double hydroxide material with low crystallinity, and the zirconium-doped cobalt-iron layered double hydroxide material is used for efficient bifunctional seawater decomposition.

The invention prepares the low-crystallinity material of the zirconium-doped cobalt-iron layered double hydroxide with hydrogen production and oxygen production electrocatalysis performances by utilizing an electrodeposition method.

A preparation method of zirconium-doped cobalt iron layered double hydroxide with low crystallinity comprises the following steps:

(1) dissolving a divalent cobalt source, a trivalent iron source and a tetravalent zirconium source in a deionized water solution of potassium nitrate, and stirring at a constant speed to fully and uniformly mix the divalent cobalt source, the trivalent iron source and the tetravalent zirconium source, wherein the divalent cobalt source: a ferric iron source: tetravalent zirconium source: potassium nitrate: the solid-liquid ratio of the deionized water is 1-3 mmol: 1-3 mmol: 1-3 mmol: 0.2-0.4 mmol: 100-150 mL, preferably 2 mmol: 2 mmol: 2 mmol: 0.3 mmol: 100 mL;

(2) placing the pretreated substrate NF into a solution, and performing constant voltage electrodeposition of negative potential for 600-1200 s by using a three-electrode system, preferably for 900s, wherein a Pt electrode, an Ag/AgCl electrode and the NF are respectively used as a counter electrode, a reference electrode and a working electrode;

(3) the prepared material is washed by deionized water and ethanol for multiple times, and is dried in vacuum at the temperature of 60-80 ℃ for 2-4 h, preferably at the temperature of 60 ℃ for 2h, so that the low-crystallinity zirconium-doped cobalt-iron layered double hydroxide which is dried and in-situ grown on NF is obtained.

In a preferred disclosed example of the invention, the divalent cobalt source in the step (1) is one or a mixture of more of cobalt chloride, cobalt nitrate and hydrates thereof; the ferric iron source is one or a mixture of ferric chloride, ferric nitrate and hydrate thereof; the tetravalent zirconium source is one or a mixture of zirconium chloride, zirconium nitrate and hydrates thereof.

In the preferred embodiment of the present invention, the pretreated substrate NF in step (2) is obtained by putting the substrate NF into nitric acid to clean surface impurities and remove oxides.

In the preferred embodiment of the present invention, in the step (2), the area of the electrodeposited material is 1cm²。

In the preferred embodiment of the present invention, in the step (3), the washing method is to wash with deionized water for 2 times and then wash with absolute ethyl alcohol for 2 times.

The invention also aims to use the prepared zirconium-doped cobalt-iron layered double hydroxide with low crystallinity as a bifunctional electrolysis catalyst, as an anode and a cathode of electrolyzed water, and applied to hydrogen production by electrolyzing water, particularly electrolyzing seawater.

The prepared zirconium-doped cobalt-iron layered double hydroxide with low crystallinity is directly used as a cathode and an anode, a two-electrode system is adopted on an electrochemical workstation in an electrolyte of 1.0M KOH +0.5M NaCl for the performance test of electrolyzing simulated seawater, and then the performance test is carried out by linear sweep voltammetry with 5mV s^-1The scan rate of (a) obtains a polarization curve.

Advantageous effects

The preparation method disclosed by the invention is simple and easy to operate, wide in raw material source, low in price, mild in reaction and environment-friendly; the prepared zirconium-doped cobalt-iron layered double hydroxide with low crystallinity has higher bifunctional electrocatalytic activity and can be directly applied to a full-electrolysis water catalyst of seawater. Can also desalt seawater and further expand the application range.

Drawings

FIG. 1 is an X-ray powder diffraction (XRD) analysis of the low crystallinity material of zirconium-doped cobalt iron layered double hydroxide obtained in example 1;

FIG. 2 is an element distribution diagram (EDX Mapping) of the low crystallinity material of the zirconium-doped cobalt iron layered double hydroxide obtained in example 1, wherein a is a Scanning Electron Microscope (SEM) of the low crystallinity material of the zirconium-doped cobalt iron layered double hydroxide obtained in example 1; b is a Transmission Electron Microscope (TEM) of the low crystallinity material of zirconium-doped ferrocobalt layered double hydroxide obtained in example 1; c high transmission electron microscopy (HR-TEM) of the low crystallinity material of the zirconium-doped ferrocobalt layered double hydroxide obtained in example 1, inset is the selected area electron diffraction pattern (SAED) of the nanosheet; d-g is a graph showing the element distribution diagram (EDX Mapping) of the low crystallinity material of zirconium-doped ferrocobalt layered double hydroxide obtained in example 1;

FIG. 3 is a Linear Sweep Voltammogram (LSV) of the low crystallinity material of zirconium-doped ferrocobalt layered double hydroxide obtained in examples 2-4;

FIG. 4 is a Linear Sweep Voltammogram (LSV) comparing performance of the zirconium-doped ferrocobalt layered double hydroxide low-crystallinity material simulated seawater (1M KOH +0.5M NaCl) obtained in example 1 with oxygen evolution reaction in 1M KOH;

FIG. 5 is a Linear Sweep Voltammogram (LSV) comparing the performance of the zirconium-doped ferrocobalt layered double hydroxide low crystallinity material obtained in example 1 in simulated seawater (1M KOH +0.5M NaCl) and 1M KOH in full water splitting.

Detailed Description

The invention is illustrated below with reference to specific examples, but the following examples are only illustrative and are not intended to limit the scope of the invention. In addition, it should be understood that after reading the detailed description of the present invention, those skilled in the art can more clearly understand the present invention and make innovations to better solve the problems of energy consumption and environmental pollution.

Example 1

The preparation method of the low-crystallinity material of the zirconium-doped cobalt iron layered double hydroxide comprises the following steps:

will contain 2mM Co (NO)₃)₂·6H₂O(0.582g),2mM Fe(NO₃)₃·9H₂O(0.808g),2mM ZrCl₄(0.466g),0.3M KNO₃(3.03g) was dissolved in 100mL of deionized water and stirred at a constant rate for 1 hour to form a homogeneous solution; substrate NF was placed in nitric acid to clean surface impuritiesRemoving oxide; in the solution, CoFeZr/NF-900s electrodeposition is carried out through a three-electrode system, a Pt electrode, an Ag/AgCl electrode and NF are respectively used as a counter electrode, a reference electrode and a working electrode, and electrodeposition is carried out in 900s time by using a constant voltage of-1.1V (vs Ag/AgCl electrode) in the specific experimental process. Further, the area of the electrodeposited material was 1cm²(ii) a The prepared material was washed twice with deionized water and ethanol, respectively, and vacuum dried at 60 ℃ for 2 h.

FIG. 1 is an XRD pattern of a low-crystallinity material of zirconium-doped cobalt-iron layered double hydroxide obtained in this example, and the presence of CoFe-LDH is confirmed by a peak around 22 degrees derived from the (006) plane of LDH (JCPDS No. 46-0605), in which Zr is introduced⁴⁺The latter material showed a lower crystallinity, probably due to Zr⁴⁺Substituted Fe³⁺Due to lattice distortion, such low crystallinity facilitates exposure of active sites and formation of defects, thereby enhancing catalytic activity. SEM images demonstrate that many nanoplate arrays are grown on NF surfaces, TEM images further show the nanoplate structure, which can expose abundant active sites and provide efficient penetration of electrolyte. The SAED pattern shows clear concentric rings, demonstrating the formation of a polycrystalline phase, which shows a 0.19nm fringe spacing, corresponding to the (108) plane of CoFe-LDH. EDX Mapping images show that cobalt, zirconium, iron and oxygen are uniformly distributed on CoFeZr-LDH nano-sheets, and based on the data, the low-crystallinity material of the zirconium-doped cobalt-iron layered double hydroxide growing on NF is proved to be successfully synthesized.

The obtained low-crystallinity material of zirconium-doped cobalt-iron layered double hydroxide is used as an oxygen evolution electrode material for electrolyzing water and seawater, a three-electrode system is adopted for oxygen evolution reaction, and a Linear Sweep Voltammogram (LSV) of the oxygen evolution reaction is shown in figure 4, and the current density is 100mA cm^-2When the OER overpotential in fresh water is 294mV and the OER overpotential in seawater is 303mV, the performance is not obviously attenuated in alkaline simulated seawater (1M KOH +0.5M NaCl), and the material is further used as an electrolytic water device, such as a picture, and Zr is doped in the material⁴⁺Thereafter, NiFeZr/NF exhibited in both 1M KOH and alkaline simulated seawater (1M KOH +0.5M NaCl)More excellent electrocatalytic properties.

Example 2

The preparation method of the low-crystallinity material of the zirconium-doped cobalt iron layered double hydroxide comprises the following steps:

will contain 2mM Co (NO)₃)₂·6H₂O(0.582g),2mM Fe(NO₃)₃·9H₂O(0.808g),2mM ZrCl₄(0.466g),0.3M KNO₃(3.03g) was dissolved in 100mL of deionized water and stirred at a constant rate for 1 hour to form a homogeneous solution. Subsequently, the substrate NF was placed in nitric acid to clean surface impurities and remove oxides. Then, electrodeposition of CoFeZr/NF-800s was carried out in the above solution by a three-electrode system. The Pt electrode, Ag/AgCl electrode and NF were used as an auxiliary electrode, a reference electrode and a working electrode, respectively. Experimental procedures electrodeposition was carried out using a constant voltage of-1.1V (vs Ag/AgCl electrode) over a period of 800 s. Further, the area of the electrodeposited material was 1cm². Finally, the prepared material was washed twice with deionized water and ethanol, respectively, and vacuum-dried at 60 ℃ for 2 h.

The obtained material is used as an oxygen evolution electrode material and a hydrogen evolution electrode material of electrolyzed water, polarization curve tests of oxygen evolution reaction and hydrogen evolution reaction are carried out under a three-electrode system, and a linear sweep voltammetry curve (LSV) of the oxygen evolution reaction is shown in figure 3.

Example 3

The preparation method of the low-crystallinity material of the zirconium-doped cobalt iron layered double hydroxide comprises the following steps:

will contain 2mM Co (NO)₃)₂·6H₂O(0.582g),2mM Fe(NO₃)₃·9H₂O(0.808g),2mM ZrCl₄(0.466g),0.3M KNO₃(3.03g) was dissolved in 100mL of deionized water and stirred at a constant rate for 1 hour to form a homogeneous solution. Subsequently, the substrate NF was placed in nitric acid to clean surface impurities and remove oxides. Then, electrodeposition of CoFeZr/NF-1000s was carried out in the above solution by a three-electrode system. The Pt electrode, Ag/AgCl electrode and NF were used as an auxiliary electrode, a reference electrode and a working electrode, respectively. The experimental procedure used a constant of-1.1V (vs Ag/AgCl electrode)Voltage, electrodeposition was performed for 1000 s. Further, the area of the electrodeposited material was 1cm². Finally, the prepared material was washed twice with deionized water and ethanol, respectively, and vacuum-dried at 60 ℃ for 2 h.

The obtained material is used as an oxygen evolution electrode material and a hydrogen evolution electrode material of electrolyzed water, polarization curve tests of oxygen evolution reaction and hydrogen evolution reaction are carried out under a three-electrode system, and a linear sweep voltammetry curve (LSV) of the oxygen evolution reaction is shown in figure 3.

Example 4

The preparation method of the low-crystallinity material of the zirconium-doped cobalt iron layered double hydroxide comprises the following steps:

will contain 2mM Co (NO)₃)₂·6H₂O(0.582g),2mM Fe(NO₃)₃·9H₂O(0.808g),0.3M KNO₃(3.03g) was dissolved in 100mL of deionized water and stirred at a constant rate for 1 hour to form a homogeneous solution. Subsequently, the substrate NF was placed in nitric acid to clean surface impurities and remove oxides. Then, electrodeposition of CoFe/NF was carried out in the above solution by a three-electrode system. The Pt electrode, Ag/AgCl electrode and NF were used as an auxiliary electrode, a reference electrode and a working electrode, respectively. Experimental procedures electrodeposition was carried out using a constant voltage of-1.1V (vs Ag/AgCl electrode) over a period of 900 s. Further, the area of the electrodeposited material was 1cm². Finally, the prepared material was washed twice with deionized water and ethanol, respectively, and vacuum-dried at 60 ℃ for 2 h.

The obtained material is used as an oxygen evolution electrode material and a hydrogen evolution electrode material of electrolyzed water, polarization curve tests of oxygen evolution reaction and hydrogen evolution reaction are carried out under a three-electrode system, and a linear sweep voltammetry curve (LSV) of the oxygen evolution reaction is shown in figure 3.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present invention or directly or indirectly applied to other related technical fields are included in the scope of the present invention.