CN114045515A

CN114045515A - A general preparation method for loading silver nanoparticles into oxygen evolution electrocatalysts

Info

Publication number: CN114045515A
Application number: CN202111517903.3A
Authority: CN
Inventors: 宋钫; 张俊杰
Original assignee: Shanghai Jiao Tong University
Current assignee: Shanghai Jiao Tong University
Priority date: 2021-12-13
Filing date: 2021-12-13
Publication date: 2022-02-15
Anticipated expiration: 2041-12-13
Also published as: CN114045515B

Abstract

The invention relates to a general preparation method for loading silver nanoparticles to an oxygen evolution electrocatalyst. The method comprises the steps of loading metal hydroxide nanosheets on a three-dimensional metal structure substrate, putting the nanosheets into a silver nanoparticle colloidal solution for dipping, and drying to obtain the silver nanoparticle loaded oxygen evolution electrocatalyst. The noble metal silver nanoparticles are efficiently and stably loaded on the surface of the transition metal hydroxide electrocatalyst by adopting a simple and general one-step physical composite method, and the composite material has excellent oxygen evolution reaction activity and simultaneously gets rid of the more complicated nano material composite processes of traditional chemical hydrothermal, water bath and the like.

Description

Universal preparation method for loading silver nanoparticles to oxygen evolution electrocatalyst

Technical Field

The invention belongs to the field of electrocatalysts, and particularly relates to a general preparation method for loading silver nanoparticles to an oxygen evolution electrocatalyst, in particular to a preparation process for loading silver nanoparticles to a transition metal hydroxide oxygen evolution electrocatalyst by a general physical composite method.

Background

Since the 21 st century, energy crisis and environmental pollution have become two major problems that human society needs to solve. The hydrogen production by water electrolysis is an ideal scheme for people to get rid of traditional fossil energy and excessive carbon emission. However, the energy barrier of the water electrolysis process is large, and the power consumption cost is too high, so that the reduction of energy consumption and the improvement of the water electrolysis efficiency become important researches of people. The oxygen evolution reaction at the anode, which is two half reactions of the electrolyzed water, has a larger potential energy barrier than the hydrogen evolution reaction at the cathode due to the complicated four-electron transfer process, and is a bottleneck for the large-scale application of the electrolyzed water. Therefore, the development of an efficient anodic oxygen evolution electrocatalyst is a research focus that promotes the wide application of electrolyzed water.

The transition metal hydroxide catalyst is a hotspot for the research of the anode oxygen evolution reaction catalyst due to low cost. Then, the catalyst has the defects of poor activity, few active sites, low conductivity and the like, and further development of the catalyst is limited. Therefore, in order to improve the performance of the transition metal hydroxide catalyst, noble metal silver nanoparticles are introduced, which can effectively improve the conductivity and oxygen evolution reaction activity of the catalyst. For the industrial requirement, the preparation is simple, and the silver nanoparticles and the hydroxide are easily compounded by utilizing the electrostatic attraction effect between the silver nanoparticles and the hydroxide. Tests show that the composite material has excellent oxygen evolution reaction activity, overcomes the defects of hydroxide catalysts, and has good commercial application prospect.

At present, the reports of the noble metal silver nanostructure composite transition metal hydroxide are basically catalysts for electrolyzing water by combining silver nanostructures with transition metal hydroxide materials through a chemical method. For example, NiFe LDH material is grown on silver nanowires loaded on foam nickel by a hydrothermal method for bifunctional electrolysis of water (ACS appl. Mater. interfaces 2021,13,22, 26055-.

The silver nanostructure is proved by a plurality of articles to be capable of improving the catalytic effect of the transition metal hydroxide catalyst, but the articles use a complex hydrothermal method, and the silver nanostructure can be loaded on the transition metal hydroxide under the conditions of high temperature and the like.

Disclosure of Invention

The invention aims to provide a preparation method for loading silver nanoparticles to an oxygen evolution electrocatalyst, aiming at the technical problems in the prior art. The silver nano particles are loaded on the catalyst by adopting an impregnation physical composite method, have high universality and can be applied to various common metal hydroxide catalysts.

The purpose of the invention can be realized by the following scheme:

the invention provides a general preparation method for loading silver nanoparticles to an oxygen evolution electrocatalyst, which comprises the following steps:

s1, loading metal hydroxide nanosheets on a three-dimensional metal substrate;

s2, preparing a silver nanoparticle colloid solution: heating the silver nitrate solution to boiling, quickly adding the sodium citrate aqueous solution, keeping boiling, and cooling to obtain a silver nanoparticle colloidal solution;

s3, preparing a composite material: and putting the prepared three-dimensional metal substrate loaded with the metal hydroxide into a silver nanoparticle colloidal solution for dipping, and drying to obtain the silver nanoparticle loaded oxygen evolution electrocatalyst.

As an embodiment of the present invention, the metal in step S1 includes one of nickel and iron. The three-dimensional nickel substrate is a foamed nickel substrate.

As an embodiment of the present invention, in step S1, the three-dimensional metal substrate is subjected to a cleaning and drying treatment before being loaded with the metal hydroxide nanosheets. The cleaning is ultrasonic cleaning for 10-20 minutes by using 10 wt% hydrochloric acid solution, deionized water, ethanol and acetone respectively; the drying temperature is 60 ℃, and the drying time is 6 h.

As an embodiment of the present invention, the metal hydroxide nanosheets in step S1 include NiFe LDH, CoFe LDH, Co (OH)₂LDH、Ni(OH)₂LDH.

As an embodiment of the invention, the specific steps of loading NiFe LDH on the foamed nickel substrate are as follows: 0.5mmol of nickel nitrate, 0.5mmol of iron nitrate and 5mmol of urea were added to 30mL of deionized water and stirred vigorously for 30 minutes. A piece of 2 x 2cm nickel foam was dipped into a 50ml teflon lined stainless steel autoclave containing the above solution. The autoclave was sealed and held at 120 ℃ for 12 hours. The modified nickel foam was thoroughly rinsed with distilled water and dried in a vacuum oven at 80 ℃ for 3 hours.

As an embodiment of the invention, the specific steps of loading CoFe LDH on the foamed nickel substrate are as follows: 0.5mmol of ferric nitrate, 0.5mmol of cobalt nitrate, 10mmol of urea and 4mmol of ammonium fluoride were dissolved in 30mL of deionized water at room temperature to form a yellow solution, which was transferred to a 50mL stainless steel autoclave lined with polytetrafluoroethylene, into which foamed nickel was immersed. The autoclave was maintained at 120 ℃ for 6 hours. The modified nickel foam was then washed with ethanol and deionized water and then dried in a vacuum oven at 80 ℃ for 3 hours.

As an embodiment of the present invention, Co (OH) is supported on a nickel foam substrate₂The specific steps of LDH are as follows: 5mmol of cobalt nitrate and 10mmol of hexamethylenetetramine were dissolved in 40mL of deionized water. The solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene (50mL capacity) and the NF was immersed in the solution. The autoclave was sealed and kept in a constant temperature oven at 100 ℃ for 8 hours. After cooling to room temperature, the product was taken out, rinsed several times with deionized water and dried in an oven at 80 ℃ for 3 hours.

As an embodiment of the present invention, Ni (OH) is supported on a foamed nickel substrate₂The specific steps of LDH are as follows: the nickel foam was immersed in a 60mL stainless steel autoclave charged with 50mL ultrapure water. The autoclave was sealed and kept at 160 ℃ for 24 hours. The resulting sample was washed 3 times with ethanol and dried at 80 ℃ for 3 hours.

As an embodiment of the present invention, the concentration of the silver nitrate solution in the step S2 is 0.5-3 mM. The silver nitrate solution concentration is preferably 1 mM.

As an embodiment of the present invention, the concentration of the sodium citrate solution in the step S2 is 15-40 mM. The concentration of the sodium citrate solution is preferably 30 mM. The sodium citrate plays the roles of a reducing agent and a protective agent, silver nitrate is reduced to form silver nanoparticles, and meanwhile, citrate ions are adsorbed on the surfaces of the silver nanoparticles to provide surface electronegativity for the silver nanoparticles. The core of the physical impregnation method is that the surface of the silver nano-particles is negatively charged, and the surface of the metal hydroxide is positively charged.

As an embodiment of the present invention, the time for keeping boiling in step S2 is 4 to 30 minutes. The boiling time is preferably 5 minutes. The longer the boiling time, the larger the size of the silver nanoparticles. The cooling is to room temperature. The solution was a dark yellow liquid, followed by 3 washes with deionized water and ethanol. And then storing in dark to avoid the decomposition and agglomeration of Ag nano particles. This liquid is a silver nanoparticle colloidal solution and the washing is to wash out other ions in the colloidal solution, such as excess Ag +, Na +, etc. (affecting final properties and sample purity).

As one embodiment of the present invention, the silver nanoparticles in step S2 have a particle size of 5 to 100 nm. The particle size of the silver nanoparticles is preferably 5 to 30 nm. The silver nanoparticle colloidal solution is a colloid in which 20nm silver nanoparticles are dispersed, and the silver nanoparticles with small sizes are used, so that the uniformity is better, the nanoparticles can be directly and uniformly loaded on the surface of the catalyst, and the silver nanoparticle colloidal solution has more advantages in the aspects of conductivity and uniformity. Meanwhile, the prepared silver nanoparticles have smaller sizes, can more easily enter between two-dimensional catalyst layers, and improve the material transmission and charge transfer capacity between the layers. If the particle size of the silver nanoparticles is larger, the interlayer transmission capability cannot be improved.

As an embodiment of the present invention, the impregnation in step S3 is carried out under the condition of keeping out light for 1-3 h. The impregnation time is preferably 2 h. And taking out the three-dimensional metal substrate material after impregnation and washing the three-dimensional metal substrate material by using water.

As one embodiment of the present invention, the temperature of the drying in step S3 is 60 to 80 ℃, and the time of the drying is 5 to 7 hours. The temperature for drying is preferably 70 ℃ and the drying time is preferably 6 hours. And the drying is to put the three-dimensional metal substrate material into an oven.

Compared with the prior art, the invention has the following technical effects:

1) the novel composite material is used as a catalyst for the electrolytic water oxygen evolution reaction and has excellent activity of the oxygen evolution reaction.

2) In a three-electrode test, compared with a control sample processed without loading silver nanoparticles, the oxygen evolution electrocatalytic activity obtained by the process is obviously improved. Wherein the concentration is 100mA cm compared with the catalyst without silver nanoparticles^-2The overpotential of NiFe LDH decreased by 28mV, the overpotential of CoFe LDH decreased by 19mV, Co (OH) at current density₂By 25mV, Ni (OH)₂The overpotential of (a) is reduced by 55 mV.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a preparation process diagram of a metal hydroxide nanosheet loaded on a three-dimensional metal substrate;

FIG. 2 is a charge distribution diagram of silver nanoparticles and the surface of a NiFe LDH catalyst;

FIG. 3 is a micro-topography, SEM image and EDS elemental profile of a composite material; wherein a is the micro-topography and SEM image of the composite material of comparative example 5, b is the EDS element spectrum of the composite material of comparative example 1, c is the micro-topography and SEM image of the composite material of example 1, d is the EDS element spectrum of the composite material of example 1, e is the micro-topography and SEM image of the composite material of example 2, f is the EDS element spectrum of the composite material of example 1, g is the micro-topography and SEM image of the composite material of example 3, h is the EDS element spectrum of the composite material of example 1, i is the micro-topography and SEM image of the composite material of example 4, and j is the EDS element spectrum of the composite material of example 1;

FIG. 4 is a linear sweep voltammogram of a composite material.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The following examples, which are set forth to provide a detailed description of the invention and a detailed description of the operation, will help those skilled in the art to further understand the present invention. It should be noted that the scope of the present invention is not limited to the following embodiments, and that several modifications and improvements made on the premise of the idea of the present invention belong to the scope of the present invention.

The application provides a preparation method for loading silver nanoparticles to an oxygen evolution electrocatalyst, as shown in fig. 1, firstly loading metal hydroxide nanosheets on a three-dimensional metal substrate; heating the silver nitrate solution to boiling, quickly adding the sodium citrate aqueous solution, keeping boiling, and cooling to obtain a silver nanoparticle colloidal solution; and putting the prepared three-dimensional metal substrate loaded with the metal hydroxide into a silver nanoparticle colloidal solution for dipping, and drying to obtain the silver nanoparticle loaded oxygen evolution electrocatalyst.

Example 1

1. Cutting the three-dimensional metal substrate foamed nickel to 2 x 2cm, respectively ultrasonically cleaning the three-dimensional metal substrate foamed nickel for 10 minutes by using 10 wt% hydrochloric acid solution, deionized water, ethanol and acetone, drying the three-dimensional metal substrate foamed nickel at 60 ℃ for 6 hours, and taking the three-dimensional metal substrate foamed nickel out for later use.

2. And (3) loading the metal hydroxide nanosheets NiFe LDH on a foamed nickel substrate. The synthesis scheme of the specific material is as follows:

0.5mmol of nickel nitrate, 0.5mmol of iron nitrate and 5mmol of urea were added to 30mL of deionized water and stirred vigorously for 30 minutes. A piece of 2 x 2cm nickel foam was dipped into a 50ml teflon lined stainless steel autoclave containing the above solution. The autoclave was sealed and held at 120 ℃ for 12 hours. The modified nickel foam was thoroughly rinsed with distilled water and dried in a vacuum oven at 80 ℃ for 3 hours.

3. Preparing a silver nanoparticle colloidal solution: 150mL of 1mM silver nitrate solution was heated to boiling and 10mL of 30mM aqueous sodium citrate solution was added rapidly. The mixed solution was kept boiling for 5 minutes and then cooled to room temperature. The solution was a dark yellow liquid, followed by 3 washes with deionized water and ethanol. And then storing in dark to avoid the decomposition and agglomeration of the Ag nano particles, wherein the particle size of the silver nano particles is 20 nm.

4. Preparing a composite material: and putting the prepared metal hydroxide-loaded foam nickel into the silver nanoparticle colloidal solution, soaking for 2 hours in a dark condition, and then taking out the foam nickel material and washing with water. The foam nickel material is then put into an oven and dried for 6 hours at 70 ℃, and the surface of the prepared foam nickel material is light yellow.

Example 2

2. And (3) loading the metal hydroxide nanosheet CoFe LDH on a foamed nickel substrate. The synthesis scheme of the specific material is as follows:

0.5mmol of ferric nitrate, 0.5mmol of cobalt nitrate, 10mmol of urea and 4mmol of ammonium fluoride were dissolved in 30mL of deionized water at room temperature to form a yellow solution, which was transferred to a 50mL stainless steel autoclave lined with polytetrafluoroethylene, into which foamed nickel was immersed. The autoclave was maintained at 120 ℃ for 6 hours. The modified nickel foam was then washed several times with ethanol and deionized water and then dried in a vacuum oven at 80 ℃ for 3 hours.

Example 3

1. Cutting the three-dimensional metal substrate foamed nickel to 2 x 2cm, respectively ultrasonically cleaning the three-dimensional metal substrate foamed nickel for 15 minutes by using 10 wt% hydrochloric acid solution, deionized water, ethanol and acetone, drying the three-dimensional metal substrate foamed nickel at 60 ℃ for 6 hours, and taking the three-dimensional metal substrate foamed nickel out for later use.

2. Subjecting metal hydroxide nanosheets Co (OH)₂The LDH was supported on a foamed nickel substrate. Of particular materialsThe synthesis scheme is as follows:

5mmol of cobalt nitrate and 10mmol of hexamethylenetetramine were dissolved in 40mL of deionized water. The solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene (50mL capacity) and the NF was immersed in the solution. The autoclave was sealed and kept in a constant temperature oven at 100 ℃ for 8 hours. After cooling to room temperature, the product was taken out, rinsed several times with deionized water and dried in an oven at 80 ℃ for 3 hours.

Example 4

1. Cutting the three-dimensional metal substrate foamed nickel to 2 x 2cm, respectively ultrasonically cleaning the three-dimensional metal substrate foamed nickel for 20 minutes by using 10 wt% hydrochloric acid solution, deionized water, ethanol and acetone, drying the three-dimensional metal substrate foamed nickel at 60 ℃ for 6 hours, and taking the three-dimensional metal substrate foamed nickel out for later use.

2. Mixing metal hydroxide nanosheets Ni (OH)₂The LDH was supported on a foamed nickel substrate. The synthesis scheme of the specific material is as follows:

the nickel foam was immersed in a 60mL stainless steel autoclave charged with 50mL ultrapure water. The autoclave was sealed and kept at 160 ℃ for 24 hours. The resulting sample was washed 3 times with ethanol and dried at 80 ℃ for 3 hours.

Comparative example 1

This comparative example provides a method for preparing an oxygen evolution electrocatalyst loaded with silver nanoparticles, which has the specific steps similar to those of example 1, except that: and after the metal hydroxide nanosheets NiFe LDH are loaded on the foamed nickel substrate, no silver is loaded.

Comparative example 2

This comparative example provides a method for preparing an oxygen evolution electrocatalyst loaded with silver nanoparticles, which has the specific steps similar to example 2, except that: and after the metal hydroxide nanosheets CoFe LDH are loaded on the foamed nickel substrate, no silver is loaded.

Comparative example 3

This comparative example provides a method for preparing an oxygen evolution electrocatalyst loaded with silver nanoparticles, which has the specific steps similar to example 3, except that: metal hydroxide nanosheet Co (OH) supported on foamed nickel substrate₂No silver loading after LDH.

Comparative example 4

This comparative example provides a method for preparing an oxygen evolution electrocatalyst loaded with silver nanoparticles, which has the specific steps similar to example 4, except that: metal hydroxide nanosheet Ni (OH) supported on foamed nickel substrate₂No silver loading after LDH.

Comparative example 5

This comparative example provides a method for preparing an oxygen evolution electrocatalyst loaded with silver nanoparticles, which has the specific steps similar to example 4, except that: metal hydroxide nanosheet Ni (OH) is not loaded on foamed nickel substrate₂LDH，Silver is directly loaded.

As shown in fig. 2, the graph is a schematic view of Zeta potential distribution of NiFe LDH metal hydroxide and silver nanoparticle surface. It can be confirmed from the figure that the metal hydroxide prepared by the same hydrothermal method in each example is positively charged, and the citrate ions on the surface of the silver nanoparticles cause the metal hydroxide to be negatively charged. The electrostatic attraction effect can uniformly load silver nanoparticles on the surface of the metal hydroxide during impregnation.

As shown in fig. 3, the figure is an SEM topography and EDS element distribution map of each composite material after impregnation compounding.

As shown in fig. 4, the oxygen evolution absorption of the composite catalyst prepared in each example was measured in a linear sweep voltammetry curve test by a three-electrode test, with a nickel foam/nickel mesh as a working electrode, a platinum sheet and mercury-mercury oxide as a counter electrode and a reference electrode, respectively, and an electrolyte solution of 1M KOH solution. Compared with a comparison sample which is not attached with silver nanoparticles for treatment, the oxygen evolution electrocatalytic activity obtained by the treatment process is obviously improved. Wherein the concentration is 100mA cm compared with the catalyst without silver nanoparticles^-2The overpotential of NiFe LDH decreased by 28mV, the overpotential of CoFe LDH decreased by 19mV, Co (OH) at current density₂By 25mV, Ni (OH)₂The overpotential of (a) is reduced by 55 mV.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.

Claims

1. a general preparation method that silver nanoparticle is loaded to oxygen evolution electrocatalyst, is characterized in that, described general preparation method comprises the steps:

S1, supporting metal hydroxide nanosheets on a three-dimensional metal substrate;

S2, prepare silver nanoparticle colloidal solution: heat the silver nitrate solution to boiling, quickly add sodium citrate aqueous solution and keep boiling, and cool to obtain silver nanoparticle colloidal solution;

S3. Preparation of composite material: the prepared three-dimensional metal hydroxide-supported metal substrate is put into a silver nanoparticle colloidal solution, immersed, and then dried to obtain an oxygen evolution electrocatalyst supported by silver nanoparticles.

2 . The preparation method according to claim 1 , wherein in step S1 , the three-dimensional metal substrate is cleaned and dried before the metal hydroxide nanosheets are loaded. 3 .

3 . The preparation method according to claim 1 , wherein the metal hydroxide nanosheets in step S1 comprise one of NiFe LDH, CoFe LDH, Co(OH) ₂ LDH, and Ni(OH) ₂ LDH. 4 .

4. The preparation method according to claim 1, wherein the concentration of the silver nitrate solution described in step S2 is 0.5-3mM.

5 . The preparation method according to claim 1 , wherein the concentration of the aqueous sodium citrate solution in step S2 is 15-40 mM. 6 .

6 . The preparation method according to claim 1 , wherein the time for keeping the boiling described in step S2 is 4-30 minutes. 7 .

7 . The preparation method according to claim 1 , wherein the particle size of the silver nanoparticles in step S2 is 5-100 nm. 8 .

8 . The preparation method according to claim 1 , wherein the immersion in step S3 is under light-proof conditions, and the immersion time is 1-3h. 9 .

9 . The preparation method according to claim 1 , wherein the drying temperature in step S3 is 60-80° C. 10 .

10 . The preparation method according to claim 1 , wherein the drying time in step S3 is 5-7 hours. 11 .