KR102287366B1 - Pt-based core-shell nanoparticle, method of preparing the same and catalyst comprising the same - Google Patents

Abstract

The present invention provides platinum-based core-shell nano particles, a method for manufacturing the same, and a catalyst comprising the same. According to the present invention, platinum-based core-shell nano particles having excellent catalytic activity of hydrogen generation reaction. The platinum-based core-shell nano particles comprise octahedron-based palladium containing nano particles and a platinum layer positioned on the palladium containing nano particles.

Description

Platinum-based core-shell nanoparticles, manufacturing method thereof, and catalyst comprising the same

The present invention relates to platinum-based core-shell nanoparticles, a method for preparing the same, and a catalyst comprising the same. Specifically, it relates to platinum-based core-shell nanoparticles having excellent hydrogen evolution catalytic activity, a method for preparing the same, and a catalyst including the same.

_{Because hydrogen (H 2} ) gas has attracted much attention due to its use as an energy carrier and fuel in electrochemical devices, its production via hydrogen evolution reaction (HER) in acidic and alkaline electrolysers has been intensively studied practically. Alkaline electrolyzers have been mainly installed in hydrogen stations around the world due to their long-term stability, cost savings and large-scale hydrogen production systems, but the slow kinetics and high power consumption of alkaline HERs are emerging as obstacles. Therefore, a rational design of an electrocatalyst based on a HER mechanism (Volmer-Heyrovsky-Tafel) has been proposed to optimize the H adsorption strength for a metal catalyst, but there is no catalyst that satisfies this. There is a need to develop a catalyst.

The technical problem to be achieved by the present invention is to provide platinum-based core-shell nanoparticles having excellent hydrogen evolution catalytic activity, a method for preparing the same, and a catalyst including the same.

According to one aspect of the present invention, octahedral palladium-containing nanoparticles; and a platinum layer positioned on the octahedral palladium-containing nanoparticles, wherein the average length of the edges of the octahedral palladium-containing nanoparticles is 5 to 10 nm. Octahedral platinum-based core-shell nanoparticles are provided do.

According to another aspect of the present invention, preparing an octahedral palladium-containing nanoparticle dispersion; and mixing the octahedral palladium-containing nanoparticle dispersion with the dispersion containing the platinum precursor and then heating; Including, wherein the heating includes the step of heating the temperature elevated while injecting ^{carbon monoxide gas at a flow rate of 1 to 10 cm 3 / min;} .

According to another aspect of the present invention, a carbon-based carrier; and the octahedral platinum-based core-shell nanoparticles supported on the carbon-based support.

The octahedral platinum-based core-shell nanoparticles according to an embodiment of the present invention may have a large surface area due to a small size, excellent catalytic activity, and stable activity for a long time.

In a method for manufacturing an octahedral platinum-based core-shell nanoparticle according to another aspect of the present invention, a platinum layer is formed on the nanoparticles having a very small size to form a core-shell structure, whereby the octahedral platinum-based core-shell nanoparticle is formed. particles can be provided.

The catalyst according to another aspect of the present invention has an excellent effect in the activity of the hydrogen evolution reaction and excellent electrochemical properties.

1i to 1j are TEM images and HRTEM images or HAADF-STEM images of nanoparticles prepared in Preparation Example 1, Preparation Example 2, Examples 1 to 6, Comparative Example 1, and Comparative Example 2;
2A and 2B are EDS element mapping data images of nanoparticles prepared in Examples 3 and 6;
3a to 3d are graphs of the size distribution of nanoparticles prepared in Preparation Example 1, Preparation Example 2, Example 3, and Example 6.
4 is an XRD pattern of nanoparticles prepared in Preparation Example 1, Preparation Example 2, Example 3, and Example 6.
5 is XAS data of nanoparticles prepared in Examples 3 and 6.
6A to 6C are TEM images of catalysts prepared in Examples 1-1 to 6-1 and Comparative Example 2-1.
7 is a CV voltammogram of the cells of Examples 1-2 to 6-2 and Comparative Example 2-2.
8 is a CO stripping profile and ECSA performed with the cells of Examples 1-2 to 6-2 and Comparative Example 2-2.
9 is a HER polarization curve performed with the cells of Examples 1-2 to 6-2 and Comparative Example 2-2.
10A and 10B are Tafel plots in an argon-saturated electrolyte and a Tafel plot in a hydrogen-saturated electrolyte, respectively, for the cells of Examples 1-2 to 6-2 and Comparative Example 2-2, and FIG. 10C is the Tafel plot. Table showing _{j 0} values calculated from the plot.

In the present specification, when a part "includes" a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

Hereinafter, the present invention will be described in more detail.

According to an embodiment of the present invention, octahedral palladium-containing nanoparticles; and a platinum layer positioned on the octahedral palladium-containing nanoparticles, wherein the average length of the edges of the octahedral palladium-containing nanoparticles is 5 to 10 nm. Octahedral platinum-based core-shell nanoparticles are provided do.

The octahedral platinum-based core-shell nanoparticles according to an embodiment of the present invention have a very small size with an average length of an edge of 5 to 10 nm or 7 to 8 nm, and thus have a large specific surface area and generate hydrogen It can have excellent activity as a catalyst for the reaction. That is, it is possible to reduce the amount of platinum and palladium required to prepare particles having the same specific surface area, which can be economical.

The octahedral palladium-containing nanoparticles corresponding to the core of the octahedral platinum-based core-shell nanoparticles have an octahedral shape, and thus have a low surface energy, so that the shape does not change significantly during the catalytic reaction and may be stable.

The octahedral palladium-containing nanoparticles may include palladium or palladium hydride, preferably palladium. Palladium or palladium hydride has a very similar interplanar distance to platinum, so its crystallinity is also similar, making it suitable as a platinum support inside a platinum shell.

According to one embodiment of the present invention, the platinum layer may include one to five platinum atomic layers. The platinum layer may have excellent electrical properties as the number of platinum atomic layers increases.

The thickness of the platinum layer may be 0.2 to 1 nm. Specifically, when including one layer of platinum atomic layers, the thickness of the platinum layer may be about 0.2 to 0.3 nm, and when including two or three layers of platinum atomic layers, the thickness of the platinum layer is about 0.55 to 0.65 nm may be, and when including 4 or 5 platinum atomic layers, the thickness of the platinum layer may be 0.9 to 1 nm. When the platinum layer has a thickness within the above range, the manufacturing cost may be low and the catalytic activity may be excellent.

According to another embodiment of the present invention, preparing an octahedral palladium-containing nanoparticle dispersion; and mixing the octahedral palladium-containing nanoparticle dispersion with the dispersion containing the platinum precursor and then heating; Including, wherein the heating includes the step of heating the temperature elevated while injecting ^{carbon monoxide gas at a flow rate of 1 to 10 cm 3 / min;} .

According to one embodiment of the present invention, the step of preparing the octahedral palladium-containing nanoparticle dispersion may include mixing a palladium precursor solution and a first reducing agent and first heating to form octahedral palladium nanoparticles. . As described above, when the palladium precursor solution and the reducing agent are mixed and the palladium cation is reduced to prepare octahedral palladium nanoparticles, a smaller size octahedral palladium nanoparticles can be prepared without using a separate palladium seed. can Specifically, the octahedral palladium-containing nanoparticles may have an average length of an edge of 3 to 10 nm.

The step of mixing the palladium precursor solution and the first reducing agent may include mixing the palladium precursor solution and the first reducing agent solution, the first reducing agent solution includes a first reducing agent, and at least one of a solvent and a polymer material It may include more. The solvent is not particularly limited, and an aqueous solvent such as water or an organic solvent such as ethanol may be used. The polymer material may be added to control the size of the nanoparticles to be prepared, for example, polyvinylpyrrolidone, cetyltriethyl ammonium bromide (CTAB), cetyltriethyl ammonium chloride (CTAC), polyvinylcapro Lactam (PVCL), polyN,N-dimethylacrylamide (PDMAm), polyvinylpyrrolidone-polyvinylacetate (PVP-PVAc), polyacrylic acid (PAA), and the like can be exemplified.

According to one embodiment of the present invention, the palladium precursor may include at least one of sodium tetrachloro palladate, palladium acetylacetonate, potassium tetrachloro palladate, palladium chloride, palladium nitrate and palladium bromide, The first reducing agent may include, but is not limited to, one or more of citric acid, ascorbic acid, ethylene glycol, diethylene glycol, sodium borohydride and hydrazine hydrate.

The first reducing agent may be mixed with the palladium precursor in a molar ratio of 1:1 to 1:20. When the first reducing agent is added in a ratio within the above range, a side reaction may not occur while smoothly reducing the palladium precursor.

The polymer material may be mixed with the palladium precursor in a weight ratio of 1:1 to 1:10. When the polymer material is added in a ratio within the above range, octahedral palladium-containing nanoparticles of a desired size can be successfully prepared.

The primary heating may be performed at a temperature of 70 to 100° C. for about 2 to 4 hours, and may be performed while stirring. In the case of primary heating within the above temperature and time range, octahedral palladium nanoparticles may be successfully formed.

According to one embodiment of the present invention, in the step of preparing the octahedral palladium-containing nanoparticle dispersion, after forming the octahedral palladium nanoparticles, the octahedral palladium nanoparticles are mixed with a hydrogenating agent, and the 1 It may further include the step of forming octahedral palladium hydride nanoparticles by secondary heating at a temperature higher than the primary heating temperature. In the same manner as described above, the octahedral palladium nanoparticles can be further reduced to be converted into octahedral palladium hydride nanoparticles.

The step of mixing the octahedral palladium nanoparticles with the hydrogenating agent may include mixing the octahedral palladium nanoparticle dispersion and the hydrogenating agent solution, and the hydrogenating agent solution includes a hydrogenating agent, and at least one of a solvent and a polymer material may further include. The solvent and the polymer material are the same as described above.

The hydrogenating agent may include at least one of dimethylformamide, formaldehyde, acetaldehyde, n-butylamine, n-hexylamine, n-octylamine and n-dodecylamine. The reducing power of the hydrogenating agent may be stronger than that of the first reducing agent, and thus the hydrogenating agent may convert palladium to palladium hydride.

The secondary heating may be performed at a higher temperature than the primary heating, and specifically, may be performed at a temperature of 150 to 200° C. for about 15 to 20 hours. Since more energy is required to reduce palladium to palladium hydride than to reduce palladium cations to palladium, secondary heating can be performed at a higher temperature and for a longer period of time using a hydrogenating agent for stronger reduction. .

The first reducing agent solution and the hydrogenating agent solution may be preheated to a heating temperature for about 10 minutes before being mixed with the palladium precursor solution and the octahedral palladium nanoparticle dispersion. Preheating allows precise control of the reaction initiation point and reaction duration.

After forming the octahedral palladium-containing nanoparticles through the above process, they can be separated by centrifugation. After primary heating or secondary heating, octahedral palladium-containing nanoparticles are formed in a dispersed state in a mixture containing a solvent and a polymer. Therefore, only octahedral palladium-containing nanoparticles can be separated by centrifugation.

The separated octahedral palladium-containing nanoparticles may be redispersed in a solvent such as benzyl alcohol to form a platinum layer to prepare an octahedral palladium-containing nanoparticle dispersion.

The octahedral palladium-containing nanoparticle dispersion prepared in this way and the dispersion containing the platinum precursor are mixed.

The dispersion including the platinum precursor includes the platinum precursor, and may further include a solvent, a second reducing agent, and one or more stabilizers. In particular, when the second reducing agent is added, the second reducing agent may reduce the platinum cation to form a platinum layer on the octahedral palladium-containing nanoparticles. The second reducing agent may include at least one of oleyl amine, 1,2-hexanediol, n-octylamine, and pentadecylamine. The stabilizer may include at least one of oleic acid, hexadecinoic acid, octadecinoic acid, and octadecadionic acid.

According to an embodiment of the present invention, the platinum precursor may include at least one of platinum acetylacetonate, potassium tetrachloroplatinate, platinum chloride, sodium tetrachloroplatinate, tetraamine platinum nitrate and chloroplatinic acid. can

According to one embodiment of the present invention, in the dispersion containing the octahedral palladium-containing nanoparticles and the platinum precursor, the weight ratio of platinum contained in the platinum precursor to the octahedral palladium-containing nanoparticles is 1:1 to 1 : 10 can be mixed. When the platinum precursor and the octahedral palladium-containing nanoparticles are mixed in a ratio within the above range, a platinum layer may be successfully formed on the octahedral palladium-containing nanoparticles.

In addition, the number of platinum atomic layers included in the platinum layer may be controlled by adjusting the amount of the platinum precursor added. Specifically, as the content of the platinum precursor increases, the number of platinum atomic layers may increase, and as the number of platinum atomic layers increases, the catalytic properties of the platinum-based core-shell nanoparticles according to an embodiment of the present invention may be excellent. there is.

However, when the amount of the platinum precursor is excessively increased, platinum is not formed in the form of an atomic layer but aggregates in the form of particles, so it is preferable to add an appropriate amount of the platinum precursor.

Then, the mixture can be heated to form a platinum layer on the octahedral palladium-containing nanoparticles. The heating step may include; heating while increasing the temperature while injecting ^{carbon monoxide gas at a flow rate of 1 to 10 cm 3 /min.} It can be carried out in the following three steps including.

The preheating step may be performed by raising the temperature to a temperature of 100 to 150 °C in an inert gas atmosphere. In the preheating step, by heating by raising the temperature in an inert gas atmosphere such as argon, neon, or xenon, the formation of by-products due to side reactions can be suppressed.

Elevated temperature heating step may be performed and temperature rise were injected at a flow rate of ³ / min of carbon monoxide gas from 1 to 10 cm, and specifically introduced into the carbon monoxide gas at a flow rate of about 1 to 10 cm ³ / min from 5 to 10 ℃ / min It can be heated while injecting carbon monoxide gas to reach a temperature of 180 to 220 °C and a partial pressure of carbon monoxide of 0.05 to 0.5 atm by increasing the temperature at a rate of . In the heating step of increasing the temperature, carbon monoxide gas may be injected and heated to form a carbon monoxide atmosphere.

The additional heating step may be performed by stopping the injection of carbon monoxide gas, maintaining the temperature, and heating. When the carbon monoxide gas is injected in the heating step to increase the temperature and reaches a partial pressure of about 0.05 to 0.5 atm, the temperature is not raised further and the temperature at the point when the injection of the carbon monoxide gas is stopped, that is, the temperature of 180 to 220 ℃ is maintained 30 to 60 minutes. In the third heating step, the carbon monoxide gas may allow the platinum layer to be formed in a uniform shape without forming separate platinum particles, and the structure of the octahedral platinum-based core-shell nanoparticles may be successfully formed.

After the heating, after cooling to room temperature, a solvent is added and centrifuged to obtain octahedral platinum-based core-shell nanoparticles. In the heating step, the solvent included in the mixed solution may be evaporated, and due to this evaporation, the resultant after heating may include octahedral platinum-based core-shell nanoparticles and other impurities as a solid material. Therefore, only octahedral platinum-based core-shell nanoparticles can be obtained by centrifugation after redispersing in a solvent.

According to another embodiment of the present invention, a carbon-based carrier; And it may be provided with a catalyst comprising the octahedral platinum-based core-shell nanoparticles according to claim 1 supported on the carbon-based support.

According to one embodiment of the present invention, the catalyst may be prepared by supporting octahedral platinum-based core-shell nanoparticles on a carbon-based support.

The catalyst according to an embodiment of the present invention may be prepared by adding the octahedral platinum-based core-shell nanoparticle dispersion and the carbon-based support to an acid solution and ultrasonicating them.

Specifically, by adding and dispersing the octahedral platinum-based core-shell nanoparticle dispersion and the carbon-based carrier to an acid solution, organic contaminants on the surface of the nanoparticles may be washed and removed.

Then, the octahedral platinum-based core-shell nanoparticles may be supported on the carbon-based support by ultrasonication. Sonication may be performed for about 1 to 3 hours, preferably 2 hours. After being supported, the prepared catalyst may be washed twice or more with a solvent such as ethanol, and may be dried in an inert gas atmosphere after washing.

According to one embodiment of the present invention, the carbon-based carrier may be any one selected from carbon black, Ketjen black, acetylene black, activated carbon powder, carbon nanotube, carbon nanowire, carbon nanohorn, and fullerene. When the octahedral platinum-based core-shell nanoparticles are supported on the carbon-based support, the catalyst surface area is maximized, so that the catalytic activity may be excellent.

According to one embodiment of the present invention, the catalyst may have an electrochemical surface area (ECSA) of 25 to 60 m ² /g _pt . The larger the electrochemical surface area, the more catalytically active sites. The catalyst according to an embodiment of the present invention may have better catalytic activity than a conventional platinum catalyst by having an ECSA within the above range.

Hereinafter, embodiments will be described in detail to describe the present invention in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention is not to be construed as being limited to the embodiments described below. The embodiments of the present specification are provided to more completely explain the present invention to those of ordinary skill in the art.

Preparation Example 1: Preparation of octahedral palladium nanoparticles

Contains 5 ml of deionized water (resistance 18.2 MΩ), 3 ml of ethanol (Duksan), 180 mg of citric acid (Sigma Aldrich, 99%), 105 mg of polyvinylpyrrolidone (hereinafter, PVP) (molecular weight about 55,000, Sigma Aldrich) A reducing agent solution was prepared, and it was preheated for 10 minutes with magnetic stirring in an oil bath at a temperature of 80 °C. After preparing a solution containing 3 ml of water and _{57 mg of Na 2} PdCl ₄ (II) (Sigma Aldrich, 98%), it was added to the reducing agent solution and heated at 80° C. for 3 hours. Then, centrifuged at 12,000 rpm for 10 minutes to obtain octahedral palladium nanoparticles.

Preparation Example 2: Preparation of octahedral palladium hydride nanoparticles

A mixture was prepared by dispersing 10 mg of the octahedral palladium particles prepared in Preparation Example 1 in a mixture containing 15 ml of N,N-dimethylformamide (hereinafter, DMF) (Sigma Aldrich, 99%) and 30 mg of PVP. . The mixture was heated for 16 hours with magnetic stirring in an oil bath at a temperature of 160° C., and centrifuged to obtain octahedral palladium hydride nanoparticles.

Example 1 (Pd@Pt) _1L )

10 mg of the octahedral palladium nanoparticles obtained in Preparation Example 1 were redispersed in 7 ml of benzyl alcohol (Sigma Aldrich, 99%) to prepare an octahedral palladium-containing nanoparticle dispersion.

Platinum (II) acetylacetonate (Alfa Aesar, platinum 48%) 3 mg, oleylamine (Sigma Aldrich, 70%) 2 ml, oleic acid (Sigma Aldrich, 90%) 1 ml of the octahedral palladium-containing nanoparticles It was added to the dispersion, mixed, and heated to 130° C. with magnetic stirring in an argon atmosphere. After the temperature reached 130 °C, argon purging was stopped, carbon monoxide gas ^{was injected at a flow rate of 5 cm 3} /min, and the temperature was raised at a rate of 7 °C/min and heated to 200 °C. After the temperature reached 200 °C, the carbon monoxide purging was stopped and heating was further performed for 40 minutes. After cooling to room temperature, 5 ml of ethanol and 15 ml of n-hexane were added and centrifuged at 3,000 rpm for 10 minutes to prepare octahedral platinum-based core-shell nanoparticles.

Example 2 (Pd@Pt) _2-3L )

In Example 1, octahedral platinum-based core-shell nanoparticles were prepared in the same manner as in Example 1, except that 6 mg of platinum (II) acetylacetonate was used.

Example 3 (Pd@Pt) _4-5L )

In Example 1, octahedral platinum-based core-shell nanoparticles were prepared in the same manner as in Example 1, except that 10 mg of platinum (II) acetylacetonate was used.

Example 4 (PdH@Pt) _ML )

In Example 1, in the same manner as in Example 1, except that 10 mg of the octahedral palladium hydride nanoparticles obtained in Preparation Example 2 were redispersed in 7 ml of benzyl alcohol and used to prepare a dispersion, the octahedral platinum-based core- Shell nanoparticles were prepared.

Example 5 (PdH@Pt) _2-3L )

In Example 4, octahedral platinum-based core-shell nanoparticles were prepared in the same manner as in Example 4, except that 6 mg of platinum (II) acetylacetonate was used.

Example 6 (PdH@Pt) _4-5L )

In Example 4, octahedral platinum-based core-shell nanoparticles were prepared in the same manner as in Example 4, except that 6 mg of platinum (II) acetylacetonate was used.

Comparative Example 1

In Example 1, octahedral nanoparticles were prepared in the same manner as in Example 1, except that 15 mg of platinum (II) acetylacetonate was used.

Comparative Example 2

Platinum (II) acetylacetonate 20 mg and PVP 105 mg were added to 10 ml of benzyl alcohol, heated in an oil bath with magnetic stirring at 200 ° C for 1 hour, and centrifuged at 3,000 rpm for 10 minutes to obtain octahedral platinum nanoparticles. Particles were prepared.

Experimental Example 1: Analysis of TEM images

Using an HT-7700 microscope (HITACHI), the nanoparticles prepared in Preparation Examples 1, 2, Examples 1 to 6, and Comparative Examples 1 and 2 were dropped on a carbon-coated copper grid under a condition of 100 kV, respectively. It was dispersed by casting and dried, and transmission electron microscopy (TEM) images were taken.

A high-resolution TEM (HRTEM) image of the nanoparticles prepared in Preparation Examples 1 and 2 was taken using a Titan G2 ChemiSTEM Cs Prope microscope.

In addition, High-Angle Annular Dark-Field Scanning TEM (HAADF-STEM) images of nanoparticles prepared in Examples 1 to 6 using Double Cs-corrected Titan3 G2 60-300 S/TEM equipment was photographed.

1a to 1h show TEM images (left) and HRTEM images or HAADF-STEM images (right) of nanoparticles prepared in Preparation Example 1, Preparation Example 2 and Examples 1 to 6, FIGS. 1i and 1j TEM images of nanoparticles prepared in Comparative Examples 1 and 2 are shown.

1A and 1B, it can be seen that the octahedral palladium-containing nanoparticles prepared in Preparation Examples 1 and 2 have an octahedral shape. that can be checked

Referring to FIGS. 1C to 1H , as platinum has a larger atomic number than palladium and thus has a larger atomic mass, it can be seen that the platinum layer appears brighter. In addition, it can be seen that Example 1 and Example 4, Example 2 and Example 5, and Example 3 and Example 6 have a thick shell in the order. That is, as the amount of the platinum precursor increases, it can be confirmed that the platinum layer is thicker.

However, referring to FIGS. 1i and 1j, when the content of the platinum precursor is excessive, it can be confirmed that platinum particles are formed instead of the platinum layer, and even when an octahedron is manufactured using only platinum without palladium, it can be confirmed that an octahedral shape is produced. there is.

Experimental Example 2: Element Mapping Analysis

Using an FEI Double Cs-calibrated Titan3 G2 60-300S/TEM instrument from Chemi-STEM Technology and an FEI Nanoport from Eindhoven using a Titan Probe Cs TEM 300 kV, the nanoparticles prepared in Examples 3 and 6 were Energy dispersive X-ray analysis (EDS) was performed.

EDS element mapping data was derived using Super-X detector (XFEG), a high-efficiency detection system.

2A and 2B show EDS element mapping data images of nanoparticles prepared in Examples 3 and 6 for palladium and platinum.

Referring to FIGS. 2A and 2B , palladium is mostly located inside the nanoparticles, and platinum is mostly located outside the nanoparticles, so that it can be confirmed that palladium is mainly contained in the core and platinum is mainly contained in the shell. .

Experimental Example 3: Particle Size Analysis

The size distribution of the nanoparticles prepared in Preparation Example 1, Preparation Example 2, Example 3 and Example 6 was analyzed through the TEM photograph of FIG. 1 .

3A to 3D show the size distribution of the nanoparticles prepared in Preparation Example 1, Preparation Example 2, Example 3, and Example 6, respectively.

3A and 3B, the octahedral palladium nanoparticles prepared in Preparation Example 1 have an average edge length of 6.0 ± 0.7 nm, and the octahedral palladium hydride nanoparticles prepared in Preparation Example 2 have an average edge length of 6.2 ± 0.7 nm. It can be seen that it has an average edge length. That is, it can be seen that the particle size slightly increases due to the incorporation of hydrogen.

3c and 3d, the octahedral platinum-based core-shell nanoparticles prepared in Example 3 have an average edge length of 7.8 ± 0.7 nm, and the octahedral platinum-based core-shell nanoparticles prepared in Example 6 It can be seen that the particles have an average edge length of 7.9 ± 0.5 nm. That is, when the larger octahedral palladium-containing nanoparticles are included, it can be confirmed that the size of the finally produced octahedral platinum-based core-shell nanoparticles is also larger.

Experimental Example 4: XRD analysis

X-ray diffraction analyzer (PANalytical X'pert PRO-MPD/MRD) using Cu-Ka radiation under the conditions of 40 kV, 25 mA in Preparation Example 1, Preparation Example 2, Example 3, and Example 6 nano-prepared An XRD pattern of the particles was obtained.

4 shows the XRD patterns of the nanoparticles prepared in Preparation Example 1 (red dotted line), Preparation Example 2 (blue dotted line), Example 3 (red solid line), and Example 6 (blue solid line). Also, the peaks in the range of 37 to 42 ° were enlarged.

4, in the nanoparticle data of Preparation Example 1 and Preparation Example 2, it can be confirmed that the palladium peak of Preparation Example 2 is shifted in a lower direction than the palladium peak of Preparation Example 1 on the (111) plane. . This appears to be the shifting caused by the mixing of the palladium with the hydride.

In addition, in the nanoparticle data of Examples 3 and 6, the (111) plane peak can be divided into a palladium peak and a platinum peak, and the palladium (black) and platinum (green) peaks are displayed separately on the right. It can be confirmed by drawing.

Referring to the right drawing of FIG. 4 , it can be seen that the platinum peak of Example 6 is shifted in a lower direction than the platinum peak of Example 3. This indicates that the lattice of the platinum layer formed on the palladium hydride nanoparticles expands.

Experimental Example 5: XAS analysis

The X-ray Absorption near edge Structure (hereinafter, XAS) of the nanoparticles prepared in Examples 3 and 6 was performed with an 8C beamline in Pohang Accelerator Laboratory (Korea), and XAS data acquisition and analysis were performed by a standard process. .

In addition, Extended X-ray Absorption Fine Structure (EXAFS) analysis was performed.

5 shows the XAS data of the nanoparticles prepared in Examples 3 and 6. Specifically, (a) and (b) of FIG. 5 are XAS spectral data for a palladium K edge and a platinum L3 edge, respectively, (c) and (d) are EXAFS spectral data for a palladium K edge and a platinum L3 edge, respectively and (e) and (f) are Fourier-transformed EXAFS spectral data for the palladium K edge and the platinum L3 edge, respectively.

In addition, the peak position, energy difference, and peak height ratio of the XAS spectrum data of FIG. 5 (a) are shown in Table 1 below.

Peak position 1 (eV) Peak position 2 (eV) Peak Energy Difference (eV) Peak Height Ratio (I1/I2) palladium 24350.4 24373.9 23.5 0.8956 Example 3 24350.4 24373.4 23.0 0.9303 Example 6 24349.5 24370.2 20.7 0.9288

Referring to (a) of FIG. 5 , it can be seen that electrons move from palladium 1s to vacant 5p and 4f orbitals to generate two peaks. In addition, it can be confirmed that the second peak of Example 6 was formed at a lower position than the second peak of Example 3 and palladium, because palladium hydrogenated was formed.

Referring to (b) of FIG. 5 , since the platinum layers of Examples 3 and 6 have a metal structure, it can be confirmed that the peaks of platinum and platinum generally coincide.

Referring to (c) and (d) of Figure 5, it can be seen that the difference of Example 3 and the phase of Example 6 are slightly different, which is that the nanoparticles of Example 3 and the nanoparticles of Example 6 are different atoms It seems to be due to having a structure.

으로 실시예 3의 거리인 2.48

및 팔라듐의 거리인 2.45

보다 큰 것을 확인할 수 있다. 또한 실시예 6의 피크 높이가 실시예 3보다 낮은 것은 수소 리간드에 의해 형성된 비정렬 결정 구조의 수소화팔라듐 코어 때문인 것으로 보인다. Referring to (e) of FIG. 5, the peak position corresponds to the palladium interatomic spacing, and the peak position of Example 6, that is, the palladium interatomic distance is 2.52 due to the formation of palladium hydride.

to 2.48, the distance in Example 3

and 2.45, the distance in palladium

larger can be seen. In addition, the lower peak height of Example 6 than Example 3 appears to be due to the palladium hydride core having an unordered crystal structure formed by hydrogen ligands.

으로 실시예 3의 거리인 2.79

및 백금의 거리인 2.64

보다 큰 것을 확인할 수 있다. Referring to FIG. 5(f), the peak position corresponds to the platinum interatomic spacing, and the peak position of Example 6, that is, the platinum interatomic distance, is 2.82 due to the tensile stress of the platinum layer located on the palladium hydride core.

to 2.79, the distance in Example 3

and 2.64, the distance of platinum

larger can be seen.

In addition, referring to Table 1, it can be confirmed that the peak 2 of Example 6 has a lower energy than the peaks of Example 6 and palladium by palladium hydride.

Examples 1-1 to 6-1: Preparation of catalyst

Contaminants on the surface of the nanoparticles were washed by dispersing 15 mg of the nanoparticles prepared in Example 1 and 60 mg of Vulcan XC-72R carbon black in a mixed solvent of 15 ml of ethanol and 5 ml of acetic acid to prepare a mixture. The mixture was sonicated for 2 hours to prepare a catalyst, centrifuged to obtain a catalyst, washed with ethanol three times, and dried in an argon atmosphere to prepare the catalyst of Example 1-1.

The catalysts of Examples 2-1 to 6-1 were prepared in the same manner except that the nanoparticles prepared in Examples 2 to 6 were used, respectively.

Comparative Example 2-1: Preparation of catalyst

After 10 mg of the nanoparticles prepared in Comparative Example 2 were dispersed in 15 ml of ethanol, 40 mg of Vulcan XC-72R carbon black was added and sonicated for 2 hours to prepare a catalyst, followed by centrifugation to obtain a catalyst, followed by ethanol The catalyst of Comparative Example 2-1 was prepared by washing with a furnace 3 times and drying in an argon atmosphere.

Experimental Example 6: TEM image of catalyst

Using a HT-7700 microscope (HITACHI), the catalysts prepared in Examples 1-1 to 6-1 and Comparative Example 2-1 were dispersed in a carbon-coated copper grid under a condition of 100 kV by drop casting, respectively, and dried. and a transmission electron microscope (TEM) image was taken.

6A shows TEM images of the catalysts prepared in Examples 1-1 to 6-1, specifically, Example 1-1 (upper left), Example 2-1 (upper middle), and Example in FIG. 6A TEM images of the catalysts prepared in 3-1 (top right), Example 4-1 (bottom left), Example 5-1 (bottom middle) and Example 6-1 (bottom right) are shown. 6b shows a TEM image of the catalyst prepared in Comparative Example 2-1.

Referring to FIGS. 6A and 6B , it can be seen that the nanoparticles are supported on carbon to form a catalyst.

Examples 1-2 to 6-2 and Comparative Example 2-2: cell formation

A cell was formed using a three-electrode system in which a graphite rod was used as a counter electrode, Ag/AgCl was used as a reference electrode, and a glassy carbon rotating disk electrode (A-011169, ALS) with a diameter of 3 mm was applied as a working electrode. . A catalyst ink was prepared by dispersing 5 mg of the catalyst prepared in Example 1-1 in an aqueous solution containing isopropyl alcohol and 5 wt% Nafion solution. Thin-film electrodes were prepared by pipetting drop of catalyst ink onto glassy carbon (metal loading 7.5 μg/cm ^{2 ) having an area of 0.071 cm 2 .} As the electrolyte, 0.1M KOH solution prepared with deionized water (>18.2 MΩ, Arium mini ^® , Satorius) and KOH (99.99%, Sigma Aldrich) was used as the electrolyte of Example 1-2 using a solution saturated with argon or hydrogen. cells were formed.

Examples 2-2 to 6-2 and Comparative Examples were carried out in the same manner as above, except that catalyst inks were prepared using the catalysts prepared in Examples 2-1 to 6-1 and Comparative Example 2-1. 2-2 cells were formed.

Electrochemical characterization

All voltages were converted to RHE scale, and prior to electrochemical analysis, all catalysts were subjected to 50 cycles of Cyclic Voltametry (CV) at a scan rate of 200 mV/s in a voltage range of _{0.05 to 1 V RHE.} was electrochemically clarified.

To prevent surface re-ordefing, the Upper Potential Limit (UPL) was limited to _{1.00 V RHE.}

Experimental Example 7: CV curve

CV was performed at a scan rate of 50 mV/s in a voltage range of _{0.05 to 0.4 V RHE using} an argon-saturated 0.1 M KOH solution as an electrolyte.

7 shows the CV voltammograms of the cells of Examples 1-2 to 6-2 and Comparative Example 2-2 by comparing Examples having the same number of platinum atomic layers, specifically Examples 1-2, CV voltammogram of the cell of Example 4-2 and Comparative Example 2-2 (top), Example 2-2, Example 5-2 and CV voltamogram of the cell of Comparative Example 2-2 (middle), Example CV voltammograms (bottom) of the cells of Example 3-2, Example 6-2 and Comparative Example 2-2 are shown.

Referring to FIG. 7 , as the number of platinum atomic layers included in the platinum layer is smaller, it can be confirmed that the CV voltammogram has a shape different from that of the voltammogram of Comparative Example 2-2. That is, as the number of platinum atomic layers decreases, it can be confirmed that the octahedral palladium-containing nanoparticles as the core can effectively control the catalytic activity of the platinum shell.

Experimental Example 8: ECSA measurement

ECSA was analyzed according to electrochemical CO stripping. For the cells of Examples 1-2 to 6-2 and Comparative Example 2-2, _{after CO adsorption at 0.05 V RHE} and continuous removal of CO in the electrolyte, 50 mv/s at a voltage range of _{0.05 bowl 1.20 V RHE} Two cycles of CV were performed at a scan rate of Although the UPL was limited _{to 1 V RHE} , it was performed at a maximum voltage of _{1.2 V RHE} for complete oxidation _{of CO to CO 2 .}

8 shows the CO stripping profile performed with the cells of Examples 1-2 to 6-2 and Comparative Example 2-2, and ECSA derived therefrom is shown as an insert table.

Referring to FIG. 8 , the smaller the number of platinum atomic layers included in the platinum layer, the higher the ECSA, and the ECSA of Examples 1-2 to 6-2 was higher than ^{the ECSA of 23±1 m 2} /g ^{Pt of Comparative Example 2-2.} It can be confirmed that it is significantly higher than 28±2 m ² /g ^Pt.

Experimental Example 9: HER polarization curve

For the cells of Examples 1-2 to 6-2 and Comparative Example 2-2, a hydrogen-saturated 0.1 M KOH solution was used as an electrolyte, and the hydrogen evolution reaction (HER) was performed at a rotation speed of 1600 rpm and a scanning rate of 5 mV/s. ) polarization curves were analyzed.

In addition, data obtained by correcting the HER polarization curve with the ECSA.

9A shows HER polarization curves performed with the cells of Examples 1-2 to 6-2 and Comparative Example 2-2. Figure 9 (b) shows the HER polarization curves performed with the cells of Examples 1-2 to 6-2 and Comparative Example 2-2 were corrected by ECSA.

Referring to FIG. 9 , it can be seen that Examples 1-2 to 3-2 have slightly superior HER catalytic activity than Examples 4-2 to 6-2. That is, it can be confirmed that the octahedral palladium nanoparticles having the core have superior catalytic activity than the octahedral palladium hydride nanoparticles.

Experimental Example 10: Analysis of Tafel Plot

For the cells of Examples 1-2 to 6-2 and Comparative Example 2-2, using an argon-saturated 0.1 M KOH solution or a hydrogen-saturated 0.1 M KOH solution as an electrolyte, the Tafel plot data were obtained at a scanning rate of 5 mV/s. derived.

In addition, the exchange current density (j ₀ ) was calculated by the following Equation 1.

[Equation 1]

In Equation 1, j _k is the ECSA-corrected kinetic current density, α is the asymmetry factor, F is the Faraday constant, η is the overvoltage, R is the gas constant, and T is the temperature.

10A to 10C show the values _{of j 0} calculated from the Tafel plot in the argon-saturated electrolyte, the Tafel plot in the hydrogen-saturated electrolyte, and the Tafel plot for the cells of Examples 1-2 to 6-2 and Comparative Example 2-2, respectively. was shown.

Referring to Figure 10a, the slope of the Tafel plot of Examples 1-2 to 3-2 containing octahedral palladium nanoparticles and Examples 4-2 to 6-2 containing octahedral palladium hydride nanoparticles is a platinum atom It can be seen that there is almost no difference when the number of floors is the same. In other words, it can be seen that the type of core does not significantly affect the Tafel plot. In addition, as the number of platinum atomic layers increases, the slope of the Tafel plot decreases, confirming that the characteristics are excellent.

FIG. 10b is a Tafel plot with Butler-Volmer fitting including hydrogen oxidation reaction (HOR) as well as hydrogen evolution reaction. _{A value of j 0} can be obtained through FIG. 10B .

Referring to FIG. 10C , as the number of platinum atomic layers increases, j ₀ is higher, and it can be seen that the case where the core is palladium is slightly higher than the case where palladium hydride is used.

Taken together, the octahedral platinum core-shell nanoparticles according to an embodiment of the present invention have electrochemical properties such as small size, high ECSA, excellent catalytic activity for hydrogen evolution, and high exchange current density. It can be seen that this is excellent.

Claims (17)

delete delete delete Preparing an octahedral palladium-containing nanoparticle dispersion; and
mixing the octahedral palladium-containing nanoparticle dispersion with a dispersion containing a platinum precursor and then heating; including,
The heating step includes the step of heating the temperature elevated while injecting ^{carbon monoxide gas at a flow rate of 1 to 10 cm 3 /min;}
The octahedral platinum-based core-shell nanoparticles,
octahedral palladium-containing nanoparticles; and a platinum layer positioned on the octahedral palladium-containing nanoparticles,
The average length of the edge of the octahedral palladium-containing nanoparticles is 5 to 10 nm of the octahedral platinum-based core-shell nanoparticle manufacturing method.
5. The method of claim 4,
The step of preparing the octahedral palladium-containing nanoparticle dispersion is
A method for producing octahedral platinum-based core-shell nanoparticles comprising the step of mixing a palladium precursor solution and a first reducing agent and heating the first to form octahedral palladium nanoparticles.
6. The method of claim 5,
The step of preparing the octahedral palladium-containing nanoparticle dispersion is after the step of forming the octahedral palladium nanoparticles,
The octahedral type platinum-based core-shell nanoparticles further comprising the step of mixing the octahedral palladium nanoparticles with a hydrogenating agent, and performing secondary heating at a higher temperature than the primary heating to form octahedral palladium hydride nanoparticles A method of making the particles.
6. The method of claim 5,
The palladium precursor is octahedral platinum-based core-shell nanoparticles comprising at least one of sodium tetrachloro palladate, palladium acetylacetonate, potassium tetrachloro palladate, palladium chloride, palladium nitrate and palladium bromide method.
6. The method of claim 5,
The first reducing agent will include at least one of citric acid, ascorbic acid, ethylene glycol, diethylene glycol, sodium borohydride, and hydrazine hydrate.
7. The method of claim 6,
The hydrogenating agent is an octahedral platinum-based core-shell comprising at least one of dimethylformamide, formaldehyde, acetaldehyde, n-butylamine, n-hexylamine, n-octylamine and n-dodecylamine. Methods of making nanoparticles.
5. The method of claim 4,
The dispersion containing the platinum precursor will further include a second reducing agent octahedral platinum-based core-shell nanoparticle manufacturing method.
11. The method of claim 10,
The second reducing agent will include at least one of oleylamine, 1,2-hexanediol, n-octylamine, and pentadecylamine.
5. The method of claim 4,
The platinum precursor is an octahedral platinum-based core-shell comprising at least one of platinum acetylacetonate, potassium tetrachloroplatinate, platinum chloride, sodium tetrachloroplatinate, tetraamine platinum nitrate and chloroplatinic acid Methods of making nanoparticles.
5. The method of claim 4,
The octahedral palladium-containing nanoparticle dispersion and the dispersion containing the platinum precursor are mixed so that the weight ratio of platinum contained in the platinum precursor to the octahedral palladium-containing nanoparticles is 1:1 to 1:10 Octagonal A method for preparing body-shaped platinum-based core-shell nanocrystals.
5. The method of claim 4,
The heating step is performed by increasing the temperature to 180 to 220 ℃ octahedral platinum-based core-shell nanoparticle manufacturing method.
5. The method of claim 4,
After the heating step, the heating step further comprises stopping the injection of carbon monoxide gas and further heating the octahedral platinum-based core-shell nanocrystals.
16. The method of claim 15,
The additional heating step is performed for 30 to 60 minutes at a temperature of 180 to 220 ℃ octahedral platinum-based core-shell nanoparticle manufacturing method.
delete

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