CN111438373A

CN111438373A - Preparation method of copper-silver core-shell structure bimetal spherical nanoparticles

Info

Publication number: CN111438373A
Application number: CN202010462116.2A
Authority: CN
Inventors: 卢珍; 赵海东; 秦君; 梁文娟
Original assignee: Shanxi Datong University
Current assignee: Shanxi Datong University
Priority date: 2020-05-27
Filing date: 2020-05-27
Publication date: 2020-07-24
Anticipated expiration: 2040-05-27
Also published as: CN111438373B

Abstract

The invention belongs to the technical field of preparation of copper-silver core-shell structure spherical nanoparticles, and provides a preparation method of copper-silver core-shell structure bimetallic spherical nanoparticles aiming at the problem that the existing non-noble metal catalyst is easy to oxidize and deactivate. Under the condition of oil bath, carbon monoxide gas is used as a reducing agent, a two-step method is adopted, a copper core is prepared by heating, then an oleylamine solution of a silver organic compound is injected, the reaction is continued, after the reaction is finished, a product is ultrasonically and centrifugally washed by n-hexane, and the product is dispersed in the n-hexane. The prepared Cu @ Ag core-shell spherical nano-particles have good carbon dioxide electroreduction catalytic capability and higher product selectivity, and can be used for preparing carbon dioxide₂The transformation and utilization field has great application prospect.

Description

Preparation method of copper-silver core-shell structure bimetal spherical nanoparticles

Technical Field

The invention belongs to the technical field of preparation of copper-silver core-shell structure spherical nanoparticles, and particularly relates to a preparation method of copper-silver core-shell structure bimetal spherical nanoparticles. The size of the nano particles is controllable.

Background

With carbon dioxide (CO) in the atmosphere₂) The concentration is continuously increased, and the harm of global warming and climate change is gradually regarded by human beings. How to directly introduce CO₂The conversion into valuable chemical products is to deal with the greenhouse gas CO₂Optimal solution to emissions challenges. Electrochemical catalytic reduction method as efficient CO₂Treatment technique, can be used to treat CO₂Electrocatalytic reduction to carbon monoxide (CO), methane (CH)₄) Methanol (CH)₃OH, formic acid (HCOOH) and ethanol (C)₂H₅OH) and the like, has been widely noticed by people due to the advantages of clean production process, simple and controllable device, higher conversion efficiency, large-scale production and the like, and restricts CO₂The key to the development and application of electrochemical reduction technology is how to develop CO with low cost, high selectivity and high efficiency₂Electrochemically reducing the catalyst.

Metallic copper (Cu) in CO₂The Cu catalyst shows excellent characteristics in the electro-reduction catalytic reaction, and can be used for directly electro-reduction catalyzing CO₂Generating HCOOH, CH₃OH and C₂H₅OH and other products with higher utilization value, but the non-noble metal catalysts have the defects of easy oxidation, difficult control of surface structure and composition, unstable performance and the like. The proposal for solving the problems is to coat non-noble metal with high conductivity, high stability and CO resistance₂The bimetallic material with the core-shell structure is prepared from a metal material with better electro-reduction catalytic performance.

Disclosure of Invention

The invention provides a preparation method of bimetallic spherical nano particles with a copper-silver core-shell structure, aiming at the problem that the existing non-noble metal catalyst is easy to oxidize and deactivate, and the prepared copper-core silver shell and size are controllable.

The invention adopts the following technical scheme: a process for preparing bimetal spherical nanoparticles with Cu-Ag core-shell structure includes such steps as heating to prepare Cu core, injecting the solution of organic Ag compound in oleylamine, reaction, ultrasonic washing with n-hexane, and dispersing the resultant in n-hexane.

The method comprises the following specific steps:

(1) preparing copper core, namely mixing 26mg of copper organic compound, 0-180 mu L diphenyl ether and 9m L oleylamine in a three-necked flask, placing the mixture in an oil bath at 100 ℃, completely discharging oxygen in the system by using a vacuum exhaust system, introducing carbon monoxide gas at the flow rate of 90 m L/min, raising the reaction temperature to 220 ℃ at the heating rate of 10 ℃/6min, keeping the temperature at 220 ℃ for 2 hours, and cooling to 30 ℃;

(2) and (2) preparing the copper-core silver-shell bimetallic spherical nano particles, namely injecting an organic compound oleylamine solution of silver with the concentration of 1.1mg/m L (5 m L) into the copper-core product system prepared in the step (1) at the speed of 0.5 m L/h by a peristaltic pump, continuously introducing carbon monoxide in the process, keeping the temperature of the reaction system at 30 ℃, continuing to react for 1 hour after the organic compound of the silver is added, cooling to room temperature after the reaction is finished, performing ultrasonic treatment and 10000 r/m centrifugal washing on the product by using n-hexane for three times, and dispersing the final product into the n-hexane for later use.

The organic compound of copper is copper acetylacetonate, i.e. Cu (acac)₂(ii) a The organic compound of silver is silver trifluoroacetate, namely AgCF₃COO。

The method adopts a two-step method, firstly prepares the copper core and then grows the silver shell, successfully prepares the adjustable copper-silver core-shell bimetal spherical nano particles with a plurality of sizes (10.0 +/-1.6, 8.4 +/-0.7 and 6.7 +/-0.6 nm), and the X-ray powder diffraction (XRD) test result shows that the product is the composition of Cu and Ag single metal, but the composition of CuAg alloy is not found; the ultraviolet visible spectrum test result shows that two surface plasma resonance peaks of the product respectively correspond to Cu (about 600 nm) and Ag (about 400 nm) single metal, and the resonance absorption peak of the CuAg alloy does not appear; indicating that the resulting product is a bimetal rather than a copper silver alloy.

The size is controlled mainly by the amount of diphenyl ether in the reaction, the sizes of diphenyl ether are 10.0 +/-1.6 nm, 8.4 +/-0.7 nm and 6.7 +/-0.6 nm when the dosage of diphenyl ether is 0, 90 and 180 mu L respectively.

Further subjecting the product to CO₂An electroreduction catalysis test shows that the prepared Cu @ Ag core-shell spherical nano particle has good carbon dioxide electroreduction catalysis capability and higher product selectivity, and CO is subjected to electroreduction catalysis₂The transformation and utilization field has great application prospect.

Drawings

FIG. 1 is a TEM image of copper-silver core-shell bimetallic spherical nanoparticles prepared by a two-step method; in the figure: a is a transmission diagram of the product obtained in example 1; b is a transmission diagram of the product obtained in example 2; c is a transmission plot of the product obtained in example 3;

FIG. 2 is an XRD spectrum of a copper-silver core-shell bimetallic spherical nanoparticle prepared by a two-step method;

FIG. 3 is a diagram of the UV-Vis spectra of the Cu-Ag core-shell bimetal spherical nanoparticles prepared by a two-step method;

FIG. 4 is a Faraday efficiency curve of carbon dioxide electrocatalytic reduction of copper-silver core-shell bimetallic spherical nanoparticles with the size of 6.7 + -0.6 nm.

Detailed Description

Example 1 preparation of copper nuclei, 26mg of copper acetylacetonate, 0. mu. L diphenyl ether and 9m L oleylamine were mixed in a three-necked flask and placed in a 100 ℃ oil bath, oxygen in the system was completely discharged by a vacuum evacuation system, carbon monoxide gas was introduced at a flow rate of 90 m L/min, and then the reaction temperature was raised to 220 ℃ at a temperature raising rate of 10 ℃/6min, the reaction was maintained at 220 ℃ for 2 hours and cooled to 30 ℃.

And (3) preparing a silver shell, namely injecting a 5m L1.1.1 mg/m L silver trifluoroacetate oleylamine solution into the prepared copper core product system at the speed of 0.5 m L/h by using a peristaltic pump, continuously introducing carbon monoxide during the period, keeping the temperature of the reaction system at 30 ℃, continuing to react for 1 hour after the silver precursor is added, cooling to room temperature after the reaction is finished, performing ultrasonic centrifugal washing on the product by using n-hexane, and dispersing the final product into the n-hexane for later use.

As shown in a diagram in fig. 1, the transmission diagram of the product shows that the product is spherical nanoparticles with the size distribution of 10.0 +/-1.6 nm; the obtained product is copper-silver bimetal rather than copper-silver alloy according to XRD and UV spectrums.

Example 2 preparation of copper nuclei, 26mg of copper acetylacetonate, 90. mu. L diphenyl ether and 9m L oleylamine were mixed in a three-necked flask and placed in a 100 ℃ oil bath, oxygen in the system was completely discharged by a vacuum evacuation system, carbon monoxide gas was introduced at a flow rate of 90 m L/min, and then the reaction temperature was raised to 220 ℃ at a temperature raising rate of 10 ℃/6min, the reaction was maintained at 220 ℃ for 2 hours and cooled to 30 ℃.

As shown in the b diagram in fig. 1, the transmission diagram of the product shows that the product is spherical nanoparticles with the size distribution of 8.4 +/-0.7 nm; the obtained product is copper-silver bimetal rather than copper-silver alloy according to XRD and UV spectrums.

Example 3 preparation of copper nuclei, 26mg of copper acetylacetonate, 180. mu. L diphenyl ether and 9m L oleylamine were mixed in a three-necked flask and placed in a 100 ℃ oil bath, oxygen in the system was completely discharged by means of a vacuum evacuation system, carbon monoxide gas was introduced at a flow rate of 90 m L/min, and then the reaction temperature was raised to 220 ℃ at a temperature raising rate of 10 ℃/6min, the reaction was maintained at 220 ℃ for 2 hours and cooled to 30 ℃.

As shown in the c diagram in fig. 1, the transmission diagram of the product shows that the product is spherical nanoparticles with the size distribution of 6.7 +/-0.6 nm; the obtained product is copper-silver bimetal rather than copper-silver alloy according to XRD and UV spectrums.

Further subjecting the product to CO₂The experimental data of the electro-reduction catalytic test are shown in table 1, and the faradaic efficiency curve of carbon dioxide electro-catalytic reduction of the Cu @ Ag core-shell spherical nano particles with the particle size of 6.7 +/-0.6 nm is shown in figure 4. The products were dominated by ethylene at voltages of-3.50V, -3.00V and-2.75V (vs. Ag/AgCl), by formic acid at cell voltages of-2.25V (vs. Ag/AgCl), and by carbon monoxide at lower cell voltages of-2.00V and-1.75V (vs. Ag/AgCl).

Table 1 shows the relationship between the carbon dioxide electrocatalytic reduction product and the potential of the copper-silver core-shell bimetallic spherical nanoparticles with the size of 6.7 +/-0.6 nm.

Claims

1. A preparation method of bimetallic spherical nano particles with a copper-silver core-shell structure is characterized by comprising the following steps: under the condition of oil bath, carbon monoxide gas is used as a reducing agent, a two-step method is adopted, a copper core is prepared by heating, then an oleylamine solution of a silver organic compound is injected, the reaction is continued, after the reaction is finished, a product is ultrasonically and centrifugally washed by n-hexane, and the product is dispersed in the n-hexane.

2. The preparation method of the bimetallic spherical nano-particle with the copper-silver core-shell structure according to claim 1 is characterized in that: the method comprises the following specific steps:

3. The preparation method of the bimetallic spherical nano-particles with the copper-silver core-shell structure according to claim 2 is characterized in that: the organic compound of copper is copper acetylacetonate, i.e. Cu (acac)₂(ii) a The organic compound of silver is silver trifluoroacetate, namely AgCF₃COO。