CN113560593B

CN113560593B - Preparation method of two-dimensional Pd nano-sieve rich in catalytic activity boundary

Info

Publication number: CN113560593B
Application number: CN202110821344.9A
Authority: CN
Inventors: 郭俊杰; 田嘉康; 宋艳慧; 刘培植; ***
Original assignee: Taiyuan University of Technology
Current assignee: Shanxi Qingfeng New Material Technology Co.,Ltd.
Priority date: 2021-07-20
Filing date: 2021-07-20
Publication date: 2023-03-10
Anticipated expiration: 2041-07-20
Also published as: CN113560593A

Abstract

The invention relates to the technical field of two-dimensional precious metal nano materials, and discloses a preparation method of a two-dimensional Pd nano-sieve rich in a catalytic activity boundary; adding palladium acetylacetonate, molybdenum hexacarbonyl, hexadecyl trimethyl ammonium bromide and ascorbic acid into a mixed solution of ethanol and water, uniformly stirring for reaction, separating the obtained solid-liquid mixture, cleaning and drying to obtain the Pd nano-sieve; high efficiency electrocatalysts useful in fuel cells and in electrochemical oxygen reduction processes; the ultrathin porous nano structure has large specific surface area and excellent charge transmission capability; a large number of low-index crystal faces and steps which are beneficial to oxygen reduction catalysis are exposed at the edge of the hole, so that the number of unsaturated active sites is greatly increased, and the electrocatalytic activity is effectively improved; the method has the advantages of high yield, easy operation and low energy consumption, and is favorable for further scientific research, popularization and application of the two-dimensional noble metal nano material.

Description

Preparation method of two-dimensional Pd nano-sieve rich in catalytic activity boundary

Technical Field

The invention belongs to the technical field of preparation of two-dimensional metal materials, and relates to a preparation method of a two-dimensional Pd nano-sieve rich in a catalytic activity boundary.

Background

In recent years, two-dimensional nanomaterials exhibit many unique physicochemical properties due to their quantum effects, small-size effects, surface effects, and macroscopic quantum tunneling effects, and thus have attracted considerable attention from researchers. The noble metal nano material has potential application value in the fields of catalysis, electrochemistry, new energy, medicine, optics and the like due to the surface plasma effect, the quantum effect and the biocompatibility of the noble metal nano material. However, the scarcity of precious metals and their expensive price have greatly hindered their widespread use. The performance of the noble metal nano material is closely related to the shape and the size of the noble metal nano material, so that the research on the synthesis of the noble metal nano material with controllable size and shape and the performance thereof is a research hotspot in the field of the nano material at present. For non-layered materials represented by metals, the non-directionality of metal bonds causes metal atoms to be closely packed in three dimensions in space, and the intrinsic driving force of two-dimensional anisotropic growth is lacked. Thus, efficient, low-cost, controllable preparation of two-dimensional metal nanomaterials is currently still a challenging topic.

For the catalytically active metal Pd, synthesis of many different shapes has been achieved by precisely controlling the thermodynamic or kinetic pathways involved in its nanocrystal growth. Among various Pd nanomaterials, two-dimensional Pd nanomaterials are of great research interest due to their anisotropic structure, excellent properties, and application prospects in electrocatalysis. However, in most of the conventional two-dimensional metal nanomaterial synthesis processes, the use of some typical chemicals greatly increases the experimental risk and the operation difficulty, and severely limits the yield of the catalyst, such as oleic acid, oleylamine, carbon monoxide and the like; the two-dimensional metal catalyst synthesis process is usually based on a hydrothermal synthesis method, the growth temperature of the catalyst needs to be controlled to about 60-180 ℃, and cost control is not facilitated; in addition, compared with other nano materials, the two-dimensional nano material has fewer exposed active crystal faces, so that the intrinsic catalytic performance of the catalyst is poor. Therefore, how to increase the number and the type of the exposed catalytic active sites while maintaining the two-dimensional morphology is also a problem worthy of intensive research. The method for manufacturing the nanometer-sized holes in the two-dimensional metal material not only can effectively improve the specific surface area and the number of active sites of the material, but also is beneficial to improving the mass transfer capacity of the material. On the basis, if the edge of the hole of the two-dimensional metal nano-sieve is composed of a specific crystal face with catalytic activity, the structure is beneficial to exposing more catalytic activity structures such as active crystal faces, crystal edges, steps and the like, so that the electrocatalytic performance of the structure is further improved. However, the noble metal nanomaterials synthesized by conventional methods are generally non-porous due to the strong isotropy of the metal bonds. Therefore, the synthesis of two-dimensional noble metal porous nano-materials with precisely controllable element compositions, material morphologies and active crystal faces remains a great challenge.

Disclosure of Invention

The invention overcomes the defects of the prior art and provides a preparation method of a two-dimensional Pd nano-sieve rich in a catalytic activity boundary. The method solves the defect that the element composition, the size and the appearance of the noble metal nano material synthesized by the traditional method are uncontrollable, and aims to comprehensively improve the performance of the electrocatalyst of the two-dimensional noble metal nano sheet.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a preparation method of a two-dimensional Pd nano-sieve rich in a catalytic activity boundary specifically comprises the following steps:

a) Palladium acetylacetonate, molybdenum hexacarbonyl, hexadecyl trimethyl ammonium bromide and ascorbic acid are added into an ethanol solution, and stirred at room temperature to fully react.

b) And (4) separating and cleaning the solid-liquid mixture after reaction for many times to obtain a black solid.

c) And drying the black solid to obtain the two-dimensional Pd nano-sieve.

Preferably, the ethanol solution in the step a is prepared by mixing absolute ethanol and ultrapure water according to a volume ratio of 1.

Preferably, the molar weight ratio of palladium acetylacetonate, molybdenum hexacarbonyl, cetyltrimethylammonium bromide to ascorbic acid is 1.01-1.

Preferably, the stirring and mixing time of the step a is 6-120 h.

Preferably, the room temperature in step a is 10-25 ℃.

Preferably, the cleaning solution adopted in the step b is a mixed solution of ethanol and water in a volume ratio of 1.

Preferably, the drying in step c is freeze drying or vacuum drying.

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

the two-dimensional Pd nano-sieve synthesized by the invention can be used as a high-efficiency electrocatalyst in fuel cells, metal-air cells and electrochemical oxygen reduction processes. In the process of stirring at room temperature, cetyl trimethyl ammonium bromide is used as a two-dimensional template, palladium acetylacetonate and molybdenum hexacarbonyl are fully reduced under the action of a reducing agent ascorbic acid, sufficient divalent palladium ions can replace molybdenum elements, the positions of the rest molybdenum elements are shifted, and the processes are in interweaving circulation, so that the defect-rich two-dimensional Pd nano-sieve is finally obtained.

Compared with the prior art, the ultrathin two-dimensional porous nano structure enables the material to have abundant defects and lattice mismatch, so that the local electronic environment can be adjusted, and excellent catalytic performance is provided. On the other hand, the unique porous structure enables the material to have a large specific surface area, more 'spaces' can be provided for charge transmission and mass transfer, meanwhile, the formation of holes exposes a large number of catalytically beneficial low-index crystal faces, and a plurality of highly reactive atomic steps are arranged at the edges of the crystal faces and used as unsaturated active sites, so that the electrocatalytic activity can be greatly improved.

In conclusion, the advantages of the two are combined, so that the prepared two-dimensional Pd nano-sieve has excellent electro-catalysis application prospect. The method has high yield and easy operation, and is favorable for further scientific research, popularization and application of the two-dimensional noble metal nano material.

Drawings

FIG. 1 is a low-power transmission electron microscope photograph of the Pd nanosieve prepared in example 1.

FIG. 2 is a high-power transmission electron microscope photograph of the Pd nanosieve prepared in example 1.

FIG. 3 is the zone diffraction pattern of the Pd nanosieve prepared in example 1.

FIG. 4 is a high-resolution transmission electron microscope photograph of the Pd nanosieve prepared in example 1.

FIG. 5 is the LSV curve (1600 rpm) in 0.1M KOH of the Pd nanosieve prepared in example 1 and a commercial platinum-carbon catalyst.

Detailed Description

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail with reference to the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical solution of the present invention is described in detail below with reference to the embodiments and the drawings, but the scope of protection is not limited thereto.

Example 1

A two-dimensional Pd nano-sieve: the preparation method of the Pd nano-sieve specifically comprises the following steps:

first, 250 mg of palladium acetylacetonate, 150 mg of molybdenum hexacarbonyl, 2.5 g of hexadecyltrimethylammonium bromide and 2,5 g of ascorbic acid were added to 600 mL of a mixed solution of ethanol and deionized water, and stirred at room temperature for 48 hours. The volume ratio of ethanol to deionized water was 5.

Then, the solid-liquid mixture after the reaction is centrifugally separated to obtain a black solid product. And washing the product with a mixed solution of ethanol and deionized water for 5 times, wherein the volume ratio of the ethanol to the deionized water is 1.

Fig. 1 is a scanning electron microscope image of the Pd nanosieve prepared in example 1, from which it can be seen that the morphology of the sample prepared in example 1 is nanosheet.

Fig. 2 is a transmission electron microscope image of the Pd nanosieve prepared in example 1, from which it can be seen that the morphology of the sample obtained in example 1 is nanosheet, consistent with the scanning results.

FIG. 3 is a diffraction pattern of selected regions of the Pd nanosieve prepared in example 1, and it can be seen from the figure that the obtained Pd nanosieve has a polycrystalline structure.

Fig. 4 is a high-resolution transmission electron microscope image of the Pd nanosieve prepared in example 1, from which it can be seen that the crystal faces exposed at the boundary of the obtained Pd nanosieve are Pd (111) and Pd (200), and a large number of atomic steps are distributed at the edge of the pore channel.

From the above map, it can be clearly seen that the ultrathin two-dimensional porous nanostructure in this embodiment not only has a large specific surface area, but also has excellent charge transport capability and a large number of active sites, so that the prepared two-dimensional Pd nanosieve has excellent electrocatalytic performance.

Fig. 5 is an LSV curve (rotation speed 1600 rpm) of the Pd nano-sieve prepared in example 1 and the commercial platinum carbon catalyst in 0.1M KOH, and it can be seen that the obtained Pd nano-sieve has a half-wave potential of 0.96V and a performance far exceeding 0.86V of the commercial platinum carbon catalyst.

Example 2

The preparation method of the Pd nano-sieve comprises the following steps:

first, 20 mg of palladium acetylacetonate, 20 mg of molybdenum hexacarbonyl, 0.1 g of hexadecyltrimethylammonium bromide and 0.1 g of ascorbic acid were added to a mixed solution of 30 mL of ethanol and deionized water, and stirred at room temperature for 72 hours. The volume ratio of ethanol to deionized water was 5.

Example 3

The preparation method of the Pd nano-sieve comprises the following steps:

400 mg of palladium acetylacetonate, 200 mg of molybdenum hexacarbonyl, 3 g of hexadecyl trimethyl ammonium bromide and 3 g of ascorbic acid are added into 500 mL of a mixed solution of ethanol and deionized water, and the mixture is stirred for 72 hours at room temperature. The volume ratio of ethanol to deionized water was 5.

The above is a further detailed description of the present invention with reference to specific preferred embodiments, which should not be considered as limiting the invention to the specific embodiments described herein, but rather as a matter of simple derivation or substitution within the scope of the invention as defined by the appended claims, it will be understood by those skilled in the art to which the invention pertains.

Claims

1. A preparation method of a two-dimensional Pd nano-sieve rich in a catalytic activity boundary is characterized by comprising the following steps:

a) Adding palladium acetylacetonate, molybdenum hexacarbonyl, hexadecyl trimethyl ammonium bromide and ascorbic acid into an ethanol solution, and stirring at 10-25 ℃ to fully react; the molar weight ratio of the palladium acetylacetonate, the molybdenum hexacarbonyl, the hexadecyl trimethyl ammonium bromide to the ascorbic acid is 1.01-1;

b) Separating and cleaning the solid-liquid mixture after reaction for many times to obtain black solid;

c) And drying the black solid to obtain the two-dimensional Pd nano-sieve.

2. The method for preparing a two-dimensional Pd nano-sieve with rich catalytic activity boundary according to claim 1, wherein the ethanol solution obtained in the step a) is prepared by mixing absolute ethanol and ultrapure water according to a volume ratio of 1.

3. The method for preparing a two-dimensional Pd nanosieve rich in a catalytically active boundary according to claim 1, wherein the stirring and mixing time of step a) is 6-120 h.

4. The method for preparing a two-dimensional Pd nanosieve rich in a catalytic activity boundary according to claim 1, wherein the cleaning solution used in the step b) is a mixed solution of ethanol and water in a volume ratio of 1.

5. The method for preparing a two-dimensional Pd nanosieve rich in a catalytically active boundary according to claim 1, wherein the drying in step c) is freeze-drying or vacuum-drying.