CN114394603A

CN114394603A - Amorphous nickel-iron-based boride nano material and preparation method and application thereof

Info

Publication number: CN114394603A
Application number: CN202111672916.8A
Authority: CN
Inventors: 郑昭科; 赵云瑞; 黄柏标; 王泽岩; 王朋; 刘媛媛; 程合锋; 张倩倩; 张晓阳
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2021-12-31
Filing date: 2021-12-31
Publication date: 2022-04-26
Anticipated expiration: 2041-12-31
Also published as: CN114394603B

Abstract

The invention belongs to the technical field of new materials, and relates to an electrocatalyst for preparing oxygen by electrocatalytic decomposition of water, in particular to an amorphous nickel-iron-based boride nano material and a preparation method and application thereof. When the amorphous nickel-iron-based boride nano material provided by the invention is used as an electrocatalyst, a lower oxygen generation overpotential can be realized, and the amorphous nickel-iron-based boride nano material has better stability.

Description

Amorphous nickel-iron-based boride nano material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of new materials, relates to an electrocatalyst for preparing oxygen by electrocatalytic decomposition of water, and particularly relates to an amorphous nickel-iron-based boride nano material as well as a preparation method and application thereof.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

The water splitting reaction consists of two half-reactions: oxygen Evolution Reactions (OER) and Hydrogen Evolution (HER) reactions. It is known from the studies of the inventors that amorphous boride is easily corroded during electrochemical reaction when it is used as an electrocatalyst due to its inherent structure and low thermodynamic stability. Therefore, the reasonable design and construction of the amorphous nickel-iron-based boride to simultaneously obtain high OER activity and high stability are crucial to the realization of the application of the industrial electrolyzed water of the transition metal boride.

Disclosure of Invention

In order to solve the defects of the prior art, the invention aims to provide the amorphous nickel-iron-based boride nano material and the preparation method and application thereof. The material has the advantages of easily available reaction raw materials, simple preparation method, good element environment, low cost, contribution to industrialization and the like. Therefore, the material has good application value.

In order to achieve the purpose, the technical scheme of the invention is as follows:

on the one hand, the preparation method of the amorphous NiFeB-based boride nano material comprises the steps of preparing a mixed solution of ferrous salt and nickel salt, dropwise adding a solution of borohydride into the mixed solution under the conditions of inert atmosphere and ice water bath to react to obtain the amorphous NiFeB nano material, and calcining the amorphous NiFeB nano material at low temperature under the condition of inert atmosphere to obtain the amorphous NiFeB nano material.

The amorphous NiFeB nano material prepared under the conditions of inert atmosphere and ice-water bath has a specific structure, such as a core-shell structure, a sheet structure and the like, and then is calcined at low temperature to adjust a boron electronic structure and maintain the specific structure, so that the obtained amorphous nickel iron-based boride nano material has low oxygen generation overpotential and good stability.

Research shows that when the amorphous nickel-iron-based boride nano material is in a core-shell structure, the amorphous nickel-iron-based boride nano material has more excellent electrocatalytic oxygen evolution activity and stability. When the nickel salt is nickel chloride, the obtained amorphous NiFeB nano material is of a core-shell structure, and the structure can be maintained through low-temperature calcination.

On the other hand, the amorphous ferronickel-based boride nano material is obtained by the preparation method.

In a third aspect, the amorphous ferronickel boride nano material is applied to electrocatalytic decomposition of water as an electrocatalyst.

In a fourth aspect, an apparatus for the electrolysis of water comprises a working electrode attached to the above-described amorphous nickel iron based boride nanomaterial.

Compared with the prior art, one or more technical schemes of the invention have the following beneficial effects:

the amorphous nickel-iron-based boride nano material prepared by the invention has a specific microstructure (such as a core-shell structure, a sheet structure and the like), wherein the synergistic effect of the core-shell structure is favorable for the generation of NiFeOOH active species. In one aspect, the boride core, due to its higher electrical conductivity, can facilitate charge transfer during OER. On the other hand, the borate shell exposes more active sites, and promotes the generation of NiFeOOH. In addition, the proportion of surface borate of the amorphous ferronickel boride nano material is increased after low-temperature calcination, so that the number of active sites and the valence state of nickel in the active substance are further increased. Compared with the amorphous nickel-iron-based boride nano material with a sheet structure, the core-shell structure of the amorphous NiFeB NPs-300 catalyst is beneficial to the catalyst to keep stable in the OER process, and the ordered nano particle structure shows a larger electrochemical active area compared with a nano sheet structure in disordered distribution. In the OER process, the shape and the electronic structure of the amorphous nickel-iron-based boride nano material with the core-shell structure are more favorable for reconstruction to generate NiFeOOH active substances. Thanks to these characteristics, the amorphous NiFeB NPs-300 catalyst exhibits excellent electrocatalytic oxygen evolution activity and stability.

The amorphous nickel-iron-based boride nano material has the advantages of easily obtained reaction raw materials, simple preparation method, good element environment, low cost, contribution to industrialization and the like. In the research process of the invention, the amorphous nickel-iron-based boride nano material with different morphologies can be prepared by changing the type of nickel salt in the reaction process, and the difference between the electronic structure of the catalyst and the performance of the catalyst is caused by the morphological difference.

The amorphous nickel-iron-based boride nano material is coated on foamed nickel to be used as a working electrode, and only 231mV overpotential is needed to generate 20mA cm in OER reaction^-2And at a current density of 10mA cm^-2The amorphous nickel-iron-based boride nano material prepared by the invention has good electrocatalytic oxygen production activity and stability, and has wide prospect in the aspect of practical application.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is an electron microscope image of an amorphous NiFeB NPs catalyst and an amorphous NiFeB NPs-300 catalyst prepared in example 1 of the present invention, a is an SEM image of the amorphous NiFeB NPs catalyst, b is an SEM image of the amorphous NiFeB NPs-300 catalyst, c is a low-magnification TEM image of the amorphous NiFeB NPs catalyst, d is a low-magnification TEM image of the NiFeB NPs-300 catalyst, e is an HRTEM image of the amorphous NiFeB NPs catalyst, and f is an HRTEM image of the amorphous NiFeB NPs-300 catalyst.

FIG. 2 shows XRD patterns and XPS images of amorphous NiFeB NPs catalyst and amorphous NiFeB NPs-300 catalyst prepared in example 1 of the present invention, where a is XRD, B is Ni 2p XPS image, c is Fe 2p XPS image, and d is B1 s XPS image.

Fig. 3 is an electron microscope image of an amorphous NiFeB NSs catalyst and an amorphous NiFeB NSs-300 catalyst prepared in example 2 of the present invention, where a is an SEM image of the amorphous NiFeB NSs catalyst, b is an SEM image of the amorphous NiFeB NSs-300 catalyst, c is a low-magnification TEM image of the amorphous NiFeB NSs catalyst, and d is a low-magnification TEM image of the amorphous NiFeB NSs-300 catalyst.

Fig. 4 shows XRD patterns and XPS images of the amorphous NiFeB NSs catalyst and the amorphous NiFeB NSs-300 catalyst prepared in example 2 of the present invention, where a is XRD, B is Ni 2p XPS image, c is Fe 2p XPS image, and d is B1 s XPS image.

Fig. 5 is a graph showing the results of electrochemical oxygen evolution activity tests of the amorphous NiFeB NPs catalyst, the amorphous NiFeB NPs-300 catalyst, the amorphous NiFeB NSs catalyst, and the amorphous NiFeB NSs-300 catalyst prepared in examples 1 to 2 of the present invention, wherein a is an LSV curve, b is a tafel slope diagram, c is an EIS impedance spectrum, and d is an electric double layer capacitance diagram.

FIG. 6 is a graph of electrochemical oxygen evolution stability test results for amorphous NiFeB NPs catalysts, amorphous NiFeB NPs-300 catalysts, amorphous NiFeB NSs catalysts, and amorphous NiFeB NSs-300 catalysts prepared in examples 1-2 of the present invention.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The calcination according to the present invention is generally a heat treatment at a temperature of not less than 100 ℃. The low-temperature calcination in the invention means that the calcination temperature is not higher than 350 ℃.

In view of the problems of low OER activity, poor stability and the like of the existing amorphous nickel-iron-based boride, the invention provides an amorphous nickel-iron-based boride nano material and a preparation method and application thereof.

The invention provides a typical implementation mode of a preparation method of an amorphous nickel-iron-based boride nano material.

Research shows that when the amorphous nickel-iron-based boride nano material is in a core-shell structure, the amorphous nickel-iron-based boride nano material has more excellent electrocatalytic oxygen evolution activity and stability. In some embodiments of this embodiment, the nickel salt is nickel chloride. The obtained amorphous NiFeB nano material is of a core-shell structure, and the structure can be maintained through low-temperature calcination.

In some examples of this embodiment, the mixed solution is subjected to an oxygen-scavenging treatment prior to dropping the solution of borohydride. The oxygen-removing treatment is carried out by introducing an inert gas (e.g., nitrogen, helium, neon, argon) into the mixed solution. The exhaust time is 25-35 minutes.

In some examples of this embodiment, the solution of borohydride is subjected to an oxygen-scavenging treatment prior to dropwise addition.

In some examples of this embodiment, the molar ratio of nickel salt, ferrous salt, and borohydride is 1:0.20 to 0.30:3 to 4.

In some examples of this embodiment, the concentration of the nickel salt in the mixed solution is 0.020 to 0.030 mol/L.

In some examples of this embodiment, the reaction is continued for 1 to 3 hours after dropping the solution of borohydride. The preferable reaction time is 1.9-2.1 h.

In some examples of this embodiment, the low temperature calcination is at a temperature of 250 to 350 ℃. The low-temperature calcination time is 1.5-2.5 h.

In another embodiment of the invention, the amorphous nickel-iron-based boride nano material is obtained by the preparation method.

In a third embodiment of the invention, the application of the amorphous ferronickel boride nano material as an electrocatalyst in electrocatalytic decomposition of water is provided.

In a fourth embodiment of the present invention, there is provided an apparatus for the electrolysis of water comprising a working electrode to which is attached the above amorphous nickel iron based boride nanomaterial.

Specifically, the device is an electrolytic cell device, and the working electrode is foamed nickel coated with the amorphous nickel iron-based boride nano material.

In order to make the technical solutions of the present invention more clearly understood by those skilled in the art, the technical solutions of the present invention will be described in detail below with reference to specific embodiments.

The test materials used in the following examples are all conventional in the art and are commercially available.

Example 1

An amorphous NiFeB NPs-300 catalyst with excellent electrocatalytic oxygen evolution performance and a preparation method and application thereof comprise the following steps:

(1) synthesizing amorphous NiFeB NPs catalyst by chemical reduction method:

0.2377g of nickel chloride hexahydrate and 0.0795g of ferrous sulfate heptahydrate were dissolved in 40 ml of deionized water, stirred under ice bath conditions and argon was passed for 30 minutes to exclude oxygen from the solution. Then, 0.1419g of sodium borohydride dissolved solution which was exhausted for 30 minutes was dropped into the ferronickel solution, and stirring was continued for 2 hours while maintaining the ice bath and argon atmosphere. And centrifuging the reaction solution, washing, drying and collecting to obtain the amorphous NiFeB NPs catalyst.

(2) Low-temperature calcination synthesis of amorphous NiFeB NPs-300 catalyst:

and (2) placing the amorphous NiFeB NPs catalyst obtained in the step (1) into a porcelain boat, placing the porcelain boat into a tube furnace, and introducing argon for 30 minutes to remove oxygen. Then, heat treatment was carried out at 300 ℃ for 2 hours in an atmosphere of argon. Finally obtaining the amorphous NiFeB NPs-300 catalyst.

Example 2

An amorphous NiFeB NSs-300 catalyst with excellent electrocatalytic oxygen evolution performance and a preparation method and application thereof comprise the following steps:

(1) synthesizing an amorphous NiFeB NSs catalyst by a chemical reduction method:

0.2908g of nickel nitrate hexahydrate and 0.0795g of iron sulfite heptahydrate were dissolved in 40 ml of deionized water, stirred under ice bath conditions and argon was passed for 30 minutes to exclude oxygen from the solution. Then, 0.1419g of sodium borohydride dissolved solution which was exhausted for 30 minutes was dropped into the ferronickel solution, and stirring was continued for 2 hours while maintaining the ice bath and argon atmosphere. And centrifuging the reaction solution, washing and drying to obtain the amorphous NiFeB NSs catalyst.

(2) And (3) synthesizing an amorphous NiFeB NSs-300 catalyst by low-temperature calcination:

and (2) placing the amorphous NiFeB NSs catalyst obtained in the step (1) into a porcelain boat, placing the porcelain boat into a tube furnace, and introducing argon for 30 minutes to remove oxygen. Then, heat treatment was carried out at 300 ℃ for 2 hours in an atmosphere of argon. Finally obtaining the amorphous NiFeB NSs-300 catalyst.

Morphology schematic and phase analysis of amorphous NiFeB NPs-300 catalyst and amorphous NiFeB NSs-300 catalyst:

SEM and TEM spectra of the amorphous NiFeB NPs catalyst and the amorphous NiFeB NPs-300 catalyst prepared in example 1 are shown in FIG. 1. As can be seen in the SEM images of FIGS. 1(a-b), both the amorphous NiFeB NPs catalyst and the amorphous NiFeB NPs-300 catalyst have nanoparticle morphology. FIGS. 1(c-f) TEM and HRTEM images show that the nanoparticles of amorphous NiFeB NPs catalyst and amorphous NiFeB NPs-300 catalyst have core-shell structures. FIG. 1 illustrates that amorphous NiFeB NPs-300 catalyst formed from amorphous NiFeB NPs catalyst by low temperature calcination retains the amorphous nanoparticle morphology.

XRD and XPS spectra of the amorphous NiFeB NPs catalyst and the amorphous NiFeB NPs-300 catalyst prepared in example 1 are shown in FIG. 2. The XRD pattern in FIG. 2(a) has only one broad peak indicating the amorphous structure of the amorphous NiFeB NPs catalyst and the amorphous NiFeB NPs-300 catalyst. It can be seen from the XPS spectrum of FIG. 2(B-d) that the ratio of B-O bonds is higher and the ratio of M-B bonds is lower in the amorphous NiFeB NPs-300 catalyst, indicating that the borate is converted from boride in the amorphous NiFeB NPs-300 catalyst. FIG. 2 illustrates that the amorphous NiFeB NPs-300 catalyst formed from the amorphous NiFeB NPs catalyst by low temperature calcination only changes the electronic structure of the surface, but not the crystallinity.

SEM and TEM spectra of the amorphous NiFeB NSs catalyst and the amorphous NiFeB NSs-300 catalyst prepared in example 2 are shown in FIG. 3. The SEM images of FIG. 3(a-b) show that the amorphous NiFeB NSs catalyst and the amorphous NiFeB NSs-300 catalyst both have nanosheet morphology. FIG. 3(c-d) Low magnification TEM it can be seen that the amorphous NiFeB NSs catalyst and the amorphous NiFeB NSs-300 catalyst are composed of thick nanoplates. FIG. 3 illustrates that amorphous NiFeB NSs-300 catalyst formed from amorphous NiFeB NSs catalyst by low temperature calcination retains amorphous nanosheet morphology.

The XRD and XPS spectra of the amorphous NiFeB NSs catalyst and the amorphous NiFeB NSs-300 catalyst prepared in example 2 are shown in FIG. 4. The XRD pattern in fig. 4(a) has only one broad peak, which indicates the amorphous structure of the amorphous NiFeB NSs catalyst and the amorphous NiFeB NSs-300 catalyst. It can be seen from the XPS spectrum of FIG. 4(B-d) that the ratio of B-O bonds in the amorphous NiFeB NSs-300 catalyst is not significantly changed, indicating that the borate content in the amorphous NiFeB NSs-300 catalyst is not increased by calcination.

And (3) testing the oxygen precipitation activity of the electrochemically decomposed water:

1. the test method comprises the following steps:

the electrochemical oxygen production test was recorded by means of an electrochemical workstation (CHI 750E) using a three-electrode cell unit. The tests were carried out at room temperature with the foamed nickel coated with the amorphous NiFeB NPs catalyst, amorphous NiFeB NPs-300 catalyst, amorphous NiFeB NSs catalyst and amorphous NiFeB NSs-300 catalyst prepared in example 1-2 as the working electrode, the carbon rod as the counter electrode, the mercury oxide electrode as the reference electrode, and 1M KOH as the electrolyte solution.

2. And (3) test results:

each electrochemical oxygen evolution activity test of the amorphous NiFeB NPs catalyst, the amorphous NiFeB NPs-300 catalyst, the amorphous NiFeB NSs catalyst and the amorphous NiFeB NSs-300 catalyst prepared in example 1-2 is shown in FIG. 5. As shown in FIG. 5(a), the amorphous NiFeB NPs-300 catalyst has the most excellent electrocatalytic oxygen evolution performance at 20mA cm^-2The overpotential at current density of (a) is only 231 mV. In comparison, 257mV, 287mV, and 266mV for the amorphous NiFeB NPs catalyst, the amorphous NiFeB NSs catalyst, and the amorphous NiFeB NSs-300 catalyst, respectively, at the same current density. As shown in FIG. 5(b), the amorphous NiFeB NPs-300 catalyst also has a superior Tafel slope. FIG. 5(c) shows the EIS impedance spectra of each catalyst, showing that the amorphous NiFeB NPs-300 catalyst has the lowest EIS impedance, indicating that the amorphous NiFeB NPs-300 catalyst is more favorable for electron transfer during the reaction. As shown in FIG. 5(d), the crystalline NiFeB NPs-300 catalyst has the largest electrochemically active area, indicating that the crystalline NiFeB NPs-300 catalyst contains the most active sites. In addition, stability tests were performed on the amorphous NiFeB NPs catalyst, the amorphous NiFeB NPs-300 catalyst, the amorphous NiFeB NSs catalyst, and the amorphous NiFeB NSs-300 catalyst prepared in example 1-2. As shown in FIG. 6, in the stability test of the chronoamperometry method for 12h, only non-chronoamperometryThe crystalline NiFeB NPs-300 catalyst can keep 10mA cm in the test process^-2The current density of the catalyst, amorphous NiFeB NPs catalyst, amorphous NiFeB NSs catalyst and amorphous NiFeB NSs-300 catalyst all showed a 20% current density drop. The low overpotential and high stability of the amorphous NiFeB NPs-300 catalyst benefit from core-shell structured nanoparticles consisting of a boride core and a borate shell. And the amorphous NiFeB NPs-300 catalyst has higher borate ratio by low-temperature calcination, promotes the surface reconstruction of the catalyst, increases the active sites of oxygen evolution reaction, and is beneficial to keeping the catalyst stable. The low overpotential and long-term stability indicate that the amorphous NiFeB NPs-300 catalyst prepared in example 1 has a great industrial application value.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of an amorphous NiFeB-based boride nano material is characterized by preparing a mixed solution of ferrous salt and nickel salt, dropwise adding a solution of borohydride into the mixed solution under the conditions of inert atmosphere and ice water bath to react to obtain the amorphous NiFeB nano material, and calcining the amorphous NiFeB nano material at a low temperature under the condition of inert atmosphere to obtain the amorphous NiFeB nano material.

2. The method for preparing an amorphous nickel-iron-based boride nanomaterial according to claim 1, wherein the nickel salt is nickel chloride.

3. The method for preparing an amorphous nickel-iron-based boride nanomaterial according to claim 1, wherein the mixed solution is subjected to an oxygen-removing treatment before dropping a solution of borohydride;

or, the solution of borohydride is subjected to oxygen discharge treatment before being added dropwise.

4. The method for preparing the amorphous nickel-iron-based boride nanomaterial according to claim 1, wherein the molar ratio of the nickel salt, the ferrous salt and the borohydride is 1: 0.20-0.30: 3-4.

5. The method for preparing the amorphous nickel-iron-based boride nanomaterial according to claim 1, wherein the concentration of the nickel salt in the mixed solution is 0.020 to 0.030 mol/L.

6. The method for preparing the amorphous nickel-iron-based boride nanomaterial according to claim 1, wherein the solution of borohydride is dripped and then the reaction is continued for 1 to 3 hours; the preferable reaction time is 1.9-2.1 h.

7. The method for preparing the amorphous nickel-iron-based boride nanomaterial according to claim 1, wherein the low-temperature calcination temperature is 250 to 350 ℃; preferably, the low-temperature calcination time is 1.5-2.5 h.

8. An amorphous ferronickel based boride nanomaterial, characterized by being obtained by the preparation method of any one of claims 1 to 7.

9. Use of the amorphous nickel iron based boride nanomaterial of claim 8 as an electrocatalyst in the electrocatalytic decomposition of water.

10. An apparatus for the electrolysis of water comprising a working electrode, wherein the amorphous nife-based boride nanomaterial of claim 8 is attached to the working electrode.