CN113967741A

CN113967741A - Method for rapidly synthesizing platinum nanoparticles with large amount of dislocation

Info

Publication number: CN113967741A
Application number: CN202111181801.9A
Authority: CN
Inventors: 刘丝靓; 陈亚楠; 邓意达; 胡文彬
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2021-10-11
Filing date: 2021-10-11
Publication date: 2022-01-25
Anticipated expiration: 2041-10-11
Also published as: CN113967741B

Abstract

The invention provides a method for rapidly preparing unit metal nanoparticles with dislocation effect, which utilizes joule heat to rapidly raise temperature and rapidly lower temperature in a liquid nitrogen environment, so that the obtained metal nanoparticles are fine, uniformly dispersed and have a large amount of dislocations, and the performance of the unit metal nanoparticles is better than that of a commercial Pt/C catalyst, for example, the Pt nanoparticles with the large amount of dislocations rapidly prepared by the method have obvious strain effect, the overpotential of hydrogen evolution reaction is only 26mV, the mass activity is about 4 times of that of the commercial Pt/C catalyst, and the unit metal nanoparticles also have higher electrocatalytic stability and structural stability in 20h continuous test.

Description

Method for rapidly synthesizing platinum nanoparticles with large amount of dislocation

Technical Field

The invention belongs to the preparation of high-performance materials, and particularly relates to a method for quickly synthesizing platinum nanoparticles with a large number of dislocations.

Background

Hydrogen energy is an important alternative energy source for fossil fuels, contributing to the goal of carbon neutralization. Electrocatalytic water splitting is one of the promising hydrogen production technologies, which includes two parts, Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER), and is receiving increasing attention. The electrocatalytic decomposition of water has the advantages of easy large-scale production and high product purity.

The adjustment of the electronic structure of the surface of the catalyst is an effective strategy for improving the electrocatalytic water cracking reaction of the metal, and the defect engineering is one of means for adjusting the electronic structure. Because the defects can induce a strain field on the surface of the catalyst, the strain field adjusts the electronic structure of the adsorption sites, and the interaction between the adsorption intermediates and the adsorption sites is improved. Dislocations, as a typical type of bulk defect, can introduce a strain field on the surface of the catalyst during the catalytic process, effectively optimizing the electronic structure of the catalyst and being more stable than surface defects.

At present, methods for introducing dislocation into metal nano materials include a template method, an anodic treatment/fluorination method, a metal nitride reduction method and the like. However, the above method has a complex synthesis process, requires template organic or inorganic substances other than the metal salt reactant, and is time-consuming and energy-consuming in the reduction process, and generates waste gas. High temperature thermal shock (HTS) is an unbalanced preparation method for introducing dislocations into electrocatalysts such as alloy nanoparticles. However, the reaction and kinetic conditions of the current traditional thermal shock are still insufficient to form abundant dislocations in single metal electrocatalysts due to the small size of the single metal nanoparticles and the fast crystallization process.

Disclosure of Invention

The invention overcomes the defects that the traditional thermal shock method is difficult to introduce dislocation into the single metal nano particles and the performance of the catalyst is not obviously improved. The invention adopts the thermal shock to rapidly prepare the single metal nano-particles with a large amount of dislocation in the liquid nitrogen environment. Compared with the single metal nano particles prepared by the traditional thermal shock method, the method has the advantages that the cooling rate is high in the cooling process, the dislocation is induced to form by utilizing the extreme environment formed by liquid nitrogen, and the thermal stress and the tissue stress in the particles act simultaneously during heating, so that the dislocation is formed in the single metal nano particles and is reserved. The prepared single metal nano-particles with a large amount of dislocations have excellent electrochemical performance and good stability, and the method can be used for preparing the traditional method of the single metal nano-particle electrocatalytic material with a large amount of dislocations.

The scheme for introducing the dislocation into the single metal nanoparticle based on the liquid nitrogen is different from the scheme for introducing the dislocation into the block material, the liquid nitrogen introduces the dislocation into the block material, the dynamic recovery in the metal plastic deformation is inhibited by utilizing the liquid nitrogen environment, the deformation energy is improved, and the dislocation is accumulated, and the single metal nanoparticle does not have the process of the dynamic recovery in the plastic deformation, so that the technical personnel in the field can not directly introduce the dislocation into a system of the single metal nanoparticle. The invention utilizes the thermal stress generated by the temperature difference between the inside and the outside of the particle and the tissue stress induced dislocation caused by the inconsistent crystallization speed between the inside and the outside of the particle, and the ultralow temperature environment formed by liquid nitrogen can effectively freeze the tissue, inhibit the structural evolution inside the nano particles and ensure that the dislocation is retained in the single metal nano particles

Specifically, the method comprises the following steps: and loading current to the carbon carrier loaded with chloroplatinic acid in a liquid nitrogen environment to rapidly heat up and thermally shock, heating to the decomposition temperature of the chloroplatinic acid, and then cutting off a power supply to obtain uniformly dispersed single metal nanoparticles.

In this application, the device is placed in a liquid nitrogen bath and a sufficiently large instantaneous current is applied to instantaneously joule heat the carbon support and generate sufficient heat to decompose the metal salt.

In order to achieve a suitable temperature rise rate, the field can determine a feasible current interval by applying different currents to a specific carbon carrier and combining an infrared thermal imager for testing. According to the detection of an infrared thermal imager, based on the thermal shock of the carbon carrier, the temperature rise speed can reach 2000-class 10000 ℃/s, and the temperature reduction speed can reach 2000-class 10000 ℃/s in the liquid nitrogen environment.

Further, the carbon carrier is carbon cloth, carbon nanotube foam, carbon fiber, carbon nanotube, carbon black, graphene.

Preferably, a carbon cloth carbon carrier is selected, the current is 3.1A, the power supply is cut off after 20 milliseconds, and the particle size of the obtained single metal nano-particles is 50-100 nm.

The beneficial results of the invention lie in that a simple and convenient non-equilibrium thermal shock method is provided, and dislocation-rich single metal nano-particles are generated in an extreme environment by introducing a liquid nitrogen cooling medium. The formation of dislocation is induced by utilizing the thermal stress generated by the temperature difference between the inside and the outside of the particles and the tissue stress caused by the inconsistent crystallization speed between the inside and the outside of the particles, and the ultra-low temperature environment formed by liquid nitrogen can effectively freeze the tissue, inhibit the structural evolution inside the nanoparticles and ensure that the dislocation is retained in the single-metal nanoparticles. The strain effect caused by dislocation regulates the electronic structure of Dr-Pt, optimizes the catalytic activity of Dr-Pt, reduces overpotential, and improves stability. This work underscores the potential of environmental thermal shock in inducing dislocations in platinum nanoparticles to achieve a more efficient electrocatalyst, which may facilitate the design of different defect-rich nanomaterials.

Drawings

FIG. 1 is a structural representation of Pt nanoparticles with a large number of dislocations (Dr-Pt) produced by thermal shock in liquid nitrogen. (a) High Resolution Transmission Electron Microscopy (HRTEM) images of Dr-Pt nanoparticles.

Fig. 1(b-c) is an inverse fourier transform image of the (110) and (011) planes of the marker region Pt nanoparticles in (a), and the place marked with "T" indicates a dislocation.

FIGS. 1(d) and (h) are strain distributions of the (110) and (011) crystal planes.

Fig. 1(e) is an inverse fourier transform image of the Pt nanoparticles of (a) containing information on all crystal planes, showing a clearer image of the arrangement of atomic columns.

(f-g) an enlarged area corresponding to the area of (e) containing surface dislocations, wherein the atomic columns are marked with colored circles.

(i-l) (f-g) analysis of the interplanar spacing of surface dislocations. (compressive strain is represented by green to dark blue, tensile strain is represented by red to bright yellow.);

FIG. 2 is a HER activity and stability test for Dr-Pt. (a) At 5mV s^-1Linear Sweep Voltammograms (LSV) of Dr-Pt and Dp-Pt measured below.

FIG. 2(b) initial and LSV curves after 2000 cycles.

FIG. 2(c) shows a comparison of the mass activity of the catalysts.

FIG. 2(d) Tafel plot for each catalyst.

FIG. 2(e) Dr-Pt at 10mA cm^-2Current-time timed potential curves.

FIG. 2(f) Dr-Pt with other HER electrocatalysts at 10mA cm^-2And (4) overpotential comparison.

FIG. 3(a) HRTEM image of Dp-Pt nanoparticles.

Fig. 3(b-c) (IFFT) image corresponding to the box area in fig. 3 (a). (d-e) (b-c) atomic plane strain analysis.

FIG. 4(a-C-1) HRTEM image of Pt nanoparticles in commercial Pt/C.

FIG. 4(a-c-2-3) IFFT image

FIG. 4(a-c-4) corresponds to the strain analysis of the box area in (a-c-1).

FIG. 5(a) (d) HRTEM image of Dr-Pt nanoparticles 2000 after cycling.

Fig. 5(b-c) (IFFT image corresponding to square region in a).

Fig. 5(e-f) (d) shows an IFFT image corresponding to the square region.

FIG. 6 is a schematic diagram of the thermal shock of a liquid nitrogen environment to produce dislocation-rich platinum nanoparticles. (a) Chloroplatinic acid is decomposed into Pt atoms and chlorine gas by heating. The Pt atoms rapidly condense and crystallize to Dr-Pt on the carbon nanotubes.

Fig. 6(b) tissue stress and thermal stress act together on Pt nanoparticles triggering the formation of dislocations. The extremely fast cooling rate kinetically freezes dislocations in the nanoparticles.

Fig. 6(c) change of the d-charged electronic structure of Pt with compressive strain.

Detailed Description

Example 1

The dislocation-rich Pt nanoparticles loaded on the carbon cloth prepared by thermal shock in liquid nitrogen are carried out according to the following steps:

step 1, soaking the carbon carrier by concentrated nitric acid for 12 hours, and then washing the carbon carrier to be neutral by deionized water.

And 2, soaking the treated carbon carrier in a chloroplatinic acid aqueous solution with the concentration of 30mM for about 12 hours, and then taking out and drying.

And 3, sticking the carbon cloth loaded with chloroplatinic acid together with a copper conductive adhesive tape by using silver adhesive to prepare a device capable of carrying out thermal shock.

And 4, placing the device obtained in the step 3 in a container filled with liquid nitrogen, and connecting a direct-current power supply with the conductive adhesive tape. The applied current was about 3A, and the power was cut off after 20 msec to obtain a sample Dr-Pt supported on the carbon support.

FIG. 1(a) shows a High Resolution Transmission Electron Microscopy (HRTEM) image of Dr-Pt. The particle size of Dr-Pt is about 15nm and the inset shows the corresponding Fast Fourier Transform (FFT) pattern. The places marked with "T" are dislocations. FIG. 1(b-c) is the IFFT of FIG. 2(a), corresponding to the (110) and (011) crystal planes, respectively. FIGS. 1(d) and (h) show the Geometric Phase Analysis (GPA) images of the (110) and (011) crystal planes, respectively.

It can be seen that dislocations produce a significant strain effect on the nanoparticle surface. In addition to observing dislocations inside the particle, we also observed dislocations on the surface of the particle, as shown in FIG. 1(e-g), corresponding to the regions marked by boxes in FIG. 1 (b-c). The atomic columns of dislocations are indicated by dots. The additional half-atom planes in the surface dislocations cause distortion of the lattice around the Pt nanoparticles (as shown in fig. 1 (f-g)). Fig. 1(i-l) shows the strain distribution and the (110) interplanar spacing of the compressive region, respectively, in the region where the surface dislocations of the Pt nanoparticles are located. The pitch of the platinum nanoparticle (110) planes is 0.26 to 0.265nm, and the compression ratio is about 5 to 5.8% when the theoretical pitch d (011) is 0.276 nm.

In addition, we also conducted comparative experiments in which the device made in step 3 was placed in a glove box under Ar atmosphere at room temperature to prepare Pt nanoparticles, and the current was applied at about 3A as in the above example, and the power was turned off after 20 ms to obtain nanoparticles of Dp-Pt, Dp-Pt as a sample supported on a carbon support in HRTEM of fig. 3, and dislocations in a 20 wt.% industrial Pt/C catalyst of fig. 4. As shown in fig. 3-4, the Dp-Pt nanoparticles contained only a small number of dislocations, while there were no dislocations in the Pt nanoparticles of the commercial Pt/C catalyst. Thus, the extreme environment induced by liquid nitrogen can rapidly "freeze" dislocations in the Dr-Pt nanoparticles.

The HER activity of the Pt catalyst was tested in a 1M KOH electrolyte using a graphite rod as a counter electrode and the carbon support loaded with Dr-Pt and Dp-Pt as a cathode. Such asFIG. 2(a) shows that the HER activity of Dr-Pt is significantly improved compared to Dp-Pt. In particular, Dr-Pt exhibits excellent HER activity at 10mA cm^-2The overpotential at the current density was 26 mV. As shown in FIG. 2(d), the Tafel slope of Dr-Pt is 52mV/dec, which is much lower than that of advanced electrocatalysts such as Dp-Pt (45mV,71mV/dec) (FIG. 2 (f)). As shown in FIG. 2(C), the mass activities of Dr-Pt, Dp-Pt and commercial 20 wt.% Pt/C at an overpotential of 50mV are 1.16A mg^-1 _Pt、0.42A mg^-1 _PtAnd 0.32A mg^-1 _Pt. Further, the Dr-Pt catalyst showed negligible decay after 2000 cycles. Furthermore, chronopotentiometric measurements (FIG. 2(e)) were performed at a current density of 10mA cm-2, indicating that Dr-Pt exhibited negligible decrease in catalytic stability and activity after 20 hours.

Fig. 5 is an HRTEM image of a Dr-Pt sample after a stability test, and it can be seen from an IFFT image of each crystal plane that the number of dislocations in the sample remained good after a long electrochemical test, indicating that the defect is relatively stable.

FIG. 1 is a schematic diagram depicting the thermal shock process and dislocation formation mechanism for Dr-Pt production in liquid nitrogen media. Immediately after the thermal shock, chloroplatinic acid decomposed into Pt and Cl atoms (fig. 1 a). Since chloroplatinic acid lacks a thermodynamically stable molecular structure, a platinum chloride molecular model is substituted for chloroplatinic acid. Chlorine atoms can form chlorine gas and escape. Pt atoms are accumulated on the carbon support at an extremely fast rate. Structural stress is generated at the junction between the uncrystallized Pt atoms and the crystallized Pt atoms during the crystallization process. Thermal stress caused by the temperature gradient of the nanoparticles also has a significant effect on the atomic structure. As shown in fig. 1b, these two stresses act together on the Pt nanoparticles, causing plastic deformation in local areas and triggering the formation of dislocations. The extremely fast cooling rate also results in the dislocations produced being dynamically frozen in the nanoparticles. The strain induced by the rich dislocation reduces the d-band center of the Pt d-orbital electron (fig. 1 c). With the reduction of the center of the d-band, the d-state of the reverse bond moves to the Fermi level, the occupancy rate is increased, the adsorption energy between the metal and the reaction intermediate is weakened, and the electrocatalytic reaction is optimized.

Example 2

Dislocation-rich Pt nanoparticles supported on carbon nanotube foam prepared by thermal shock in liquid nitrogen were carried out according to the following steps:

step 1, soaking carbon nanotube foam in concentrated nitric acid for 12 hours, and then washing the carbon nanotube foam to be neutral by deionized water.

And 3, sticking the carbon nano tube foam loaded with chloroplatinic acid and a copper conductive adhesive tape together by using silver adhesive to prepare a device capable of carrying out thermal shock.

And 4, placing the device obtained in the step 3 in a container filled with liquid nitrogen, and connecting a direct-current power supply with the conductive adhesive tape. The applied current was about 3A, and the power was cut off after 15 msec to obtain a sample Dr-Pt supported on the carbon support.

The product prepared in this example was also HRTEM demonstrated to contain a large number of dislocations.

Electrochemical testing of a cell assembled with a graphite electrode according to the method of example 1 also showed excellent HER performance.

Example 3

The dislocation-rich Pt nano-particles loaded on carbon black prepared by thermal shock in liquid nitrogen are carried out according to the following steps:

step 1, uniformly mixing carbon black with 30mM chloroplatinic acid methanol solution, completely drying in an oven, and fully grinding.

And 2, placing the ground carbon powder loaded with chloroplatinic acid between two pieces of carbon cloth, and sticking the two pieces of carbon cloth and the copper conductive adhesive tape together by using silver adhesive to prepare a device capable of carrying out thermal shock.

And 3, placing the device obtained in the step 2 in a container filled with liquid nitrogen, and connecting the direct-current power supply with the conductive adhesive tape. The applied current was about 3.5A, and the power was turned off after 30 msec to obtain a sample Dr-Pt supported on the carbon support.

Electrochemical testing of a cell constructed with graphite electrodes according to the method of example 1 also showed HER performance superior to commercial Pt/C catalysts.

Claims

1. A method for rapidly synthesizing platinum nanoparticles having a large number of dislocations, characterized in that: the method comprises the following steps: and loading current to the carbon carrier loaded with chloroplatinic acid in a liquid nitrogen environment to rapidly raise the temperature, heating to the decomposition temperature of the chloroplatinic acid, and then cutting off a power supply to obtain the single metal nanoparticles with a large amount of dislocation.

2. The method of claim 1, wherein the carbon support is carbon cloth, carbon nanotube foam, carbon fiber, carbon nanotube, carbon black, graphene.

3. The method of claim 1, wherein the chloroplatinic acid has a decomposition temperature above 400 degrees celsius.

4. The method of claim 1, wherein the applied current is 2-3.5A.