A Janus Pd-AuPd melon seed-shaped nanomaterial and a one-step preparation method and application thereof

Abstract

The present invention discloses a Janus Pd-AuPd melon seed-shaped nanomaterial and a one-step preparation method and application thereof. + An auxiliary agent, a reducing agent and a coating agent are dispersed in water and stirred to obtain a mixed solution; under a protective atmosphere with an initial pressure of 1.0-1.2 MPa, the mixed solution is placed at 170-190°C for reaction for 8-12 hours, and the product is cooled, centrifuged and washed to obtain a Janus Pd-AuPd melon seed-shaped nanomaterial. The two components of the Janus structure of the present invention are AuPd alloy and Pd single metal, respectively. The present invention realizes the one-step synthesis of Janus Pd-AuPd melon seed-shaped nanomaterials, and the synthesis method has good stability and reproducibility. The nanomaterial prepared by the present invention exhibits good ORR catalytic performance and has application prospects in the field of fuel cells.

Description

Technical Field

[0001] The invention belongs to the technical field of nanomaterials, and specifically relates to a Janus Pd-AuPd melon seed-shaped nanomaterial and a one-step preparation method and application thereof. Background Art

[0002] Janus structure refers to a combination of two or more chemically different composite materials. Composite materials are generally arranged side by side in space, breaking the traditional symmetry and facilitating functionalization. Therefore, they are widely used in biosensing, drug delivery, nanomotors and other fields. In particular, the different metal components of Janus bimetallic nanoparticles not only have their own characteristics, but also can optimize the overall function through the interaction between electrons, and show unique advantages in the fields of optics and catalysis.

[0003] The methods commonly used to prepare Janus bimetallic nanoparticles include dimerization, phase separation, seeding, and co-reduction. Among them, the seeding method is favored due to its high repeatability, wide application range, and controllable product morphology. To prepare Janus bimetallic nanoparticles by seeding, it is necessary to synthesize seeds first, and then use appropriate growth factors to induce the asymmetric growth of the second metal on the seeds. In the preparation process of seeding, it is necessary to strictly control the growth kinetic factors to prevent the symmetrical deposition of metal atoms and the growth of core-shell, block and other structures (Controlled Growth of Ag / AuBimetallic Nanorods through Kinetics Control). The co-reduction method can simplify the synthesis steps and efficiently prepare Janus bimetallic nanoparticles, but related research is very challenging. The main reason is that metal precursors are easy to form alloy structures during the co-reduction process, and self-nucleation may occur, resulting in a decrease in the yield of Janus bimetallic nanoparticles. Therefore, it is of great significance to explore a simple and reliable co-reduction method for the precise preparation of Janus bimetallic nanoparticles. The solution to this problem will undoubtedly further broaden the application space of Janus bimetallic nanoparticles. Summary of the invention

[0004] In view of the deficiencies of the above-mentioned prior art, the object of the present invention is to provide a one-step preparation method of Janus Pd-AuPd melon seed-shaped nanomaterial, and at the same time apply the Janus Pd-AuPd melon seed-shaped nanomaterial as an electrocatalyst in an efficient oxygen reduction reaction.

[0005] The purpose of the present invention is achieved through the following technical solutions.

[0006] A one-step preparation method of Janus Pd-AuPd melon seed-shaped nanomaterial comprises the following steps:

[0007] (1) Gold precursor, palladium precursor, Ag + The auxiliary agent, the reducing agent and the encapsulating agent are dispersed in water and stirred to obtain a mixed solution;

[0008] (2) Under a protective atmosphere with an initial pressure of 1.0-1.2 MPa, the mixed solution is placed at 170-190° C. for reaction for 8-12 hours, and the product is cooled, centrifuged, and washed to obtain Janus Pd-AuPd melon seed-shaped nanomaterials.

[0009] Preferably, the gold precursor in step (1) is one or more of chloroauric acid and gold chloride;

[0010] Preferably, the concentration of gold precursor in the mixed solution in step (1) is 0.25 mM;

[0011] Preferably, the palladium precursor in step (1) is one or more of chloropalladic acid, palladium chloride, and sodium chloropalladate;

[0012] Preferably, the concentration of palladium precursor in the mixed solution in step (1) is 0.25 mM.

[0013] Preferably, the molar ratio of the gold precursor to the palladium precursor in step (1) is 1:1.

[0014] Preferably, in step (1), the Ag + The auxiliary agent is silver nitrate;

[0015] Preferably, in step (1), the mixed solution contains Ag + The concentration of the adjuvant was 0.204-0.408 mM.

[0016] Preferably, the reducing agent in step (1) is one or more of polyvinyl pyrrolidone, ascorbic acid, and sodium citrate;

[0017] Preferably, the mass percentage concentration of the reducing agent in the mixed solution of step (1) is 0.95wt%-1.5wt%.

[0018] Preferably, the encapsulating agent in step (1) is one or more of cetyltrimethylammonium bromide and cetyltrimethylammonium chloride;

[0019] Preferably, the mass percentage concentration of the encapsulating agent in the mixed solution of step (1) is 3.8wt%-4.5wt%.

[0020] Preferably, the centrifugal speed in step (2) is 8000-12000 rpm / min;

[0021] Preferably, the protective atmosphere in step (2) is nitrogen.

[0022] Preferably, the solution used for washing in step (2) is one or more of ultrapure water and ethanol solution.

[0023] The Janus Pd-AuPd melon seed-shaped nanomaterial prepared by the above preparation method.

[0024] The application of the above-mentioned Janus Pd-AuPd melon seed-shaped nanomaterial in electrocatalytic oxygen reduction reaction under alkaline conditions.

[0025] Preferably, the Janus Pd-AuPd melon seed-shaped nanomaterial is used to prepare a working electrode, comprising the following steps:

[0026] Carbon black, Janus Pd-AuPd melon seed-shaped nanomaterials, ethanol and Nafion are mixed and ultrasonically treated to obtain a Janus Pd-AuPd / C ethanol solution; the Janus Pd-AuPd / C ethanol solution is dropped onto a glassy carbon electrode and naturally air-dried to obtain an electrochemical working electrode for oxygen reduction reaction.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention prepares Janus Pd-AuPd melon seed-shaped nanomaterial by a one-step method. The nanomaterial consists of two parts, namely, AuPd alloy and Pd single metal; the nanomaterial is a five-fold twin structure and has a melon seed-shaped conical end.

[0029] (2) The one-step method used in the present invention is simple to operate and has good repeatability. It breaks through the barrier of preparing Janus nanomaterials by the co-reduction method and realizes the preparation of Janus nanomaterials with good monodispersity and controllable morphology and structure.

[0030] (3) The Janus Pd-AuPd melon seed-shaped nanomaterial prepared by the present invention has good ORR catalytic performance, with a half-wave potential of 0.882 V and a current density of 167 mA / mg at 0.9 V. Pd , and its catalytic performance is better than that of commercial Pt / C catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a transmission electron microscope image of the Janus Pd-AuPd melon seed-shaped nanomaterial prepared in Example 1 of the present invention.

[0032] Figure 2This is the linear sweep voltammetry curve of the Janus Pd-AuPd melon seed-shaped nanomaterial prepared in Example 1 of the present invention at a rotation speed of 1600 rpm / min.

[0033] Figure 3 This is a transmission electron micrograph of the Janus Pd-AuPd melon seed-shaped nanomaterial prepared in Example 2 of the present invention.

[0034] Figure 4 This is a transmission electron micrograph of the Janus Pd-AuPd melon seed-shaped nanomaterial prepared in Example 3 of the present invention.

[0035] Figure 5 This is a transmission electron microscope image of the AuPd nanoparticles prepared in Comparative Example 1 of the present invention.

[0036] Figure 6 This is the linear sweep voltammetry curve of the AuPd nanoparticles prepared in Comparative Example 1 of the present invention at a rotation speed of 1600 rpm / min.

[0037] Figure 7 This is a transmission electron microscope image of the Pd-AuPd nanoparticles prepared in Comparative Example 2 of the present invention.

[0038] Figure 8 This is the linear sweep voltammetry curve of the Pd-AuPd nanoparticles prepared in Comparative Example 2 of the present invention at a rotation speed of 1600 rpm / min. DETAILED DESCRIPTION

[0039] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are processes that are not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. If the manufacturer of the reagents or instruments used is not indicated, they are deemed to be conventional products that can be purchased commercially.

[0040] Example 1

[0041] Soak all glassware in newly prepared aqua regia for 1 hour, wash with ultrapure water, and dry for later use.

[0042] (1) Add 100 mg of polyvinyl pyrrolidone, 401 mg of hexadecyltrimethylammonium bromide, 125 ul of 20 mM chloroauric acid solution, 125 ul of 20 mM chloropalladic acid solution, 30 ul of 102 mM silver nitrate solution and ultrapure water to a polytetrafluoroethylene liner and stir thoroughly to form a uniform mixed solution. The total volume of the mixed solution is 10 mL.

[0043] (2) The mixed solution was transferred to a reactor, which was sealed and filled with nitrogen to make the initial pressure of the reactor 1.1 MPa; the reactor was then transferred to an oil bath at 180° C. for reaction for 12 h.

[0044] (3) After the reaction is completed, the pressure in the reactor reaches 1.8 MPa. The reactor is taken out and placed in the air to cool naturally to room temperature. The reaction solution is transferred to a centrifuge tube for high-speed centrifugation at 10000 rpm / min. The resulting precipitate is washed and dispersed in ultrapure water for storage. The resulting solution is a dispersion of Janus Pd-AuPd melon seed-shaped nanomaterials.

[0045] The transmission electron microscope photo of the Janus Pd-AuPd melon seed-shaped nanomaterial prepared in this example is shown in FIG. Figure 1 As shown in the figure, the contrast of the head and the end of the Janus Pd-AuPd melon seed-shaped nanomaterial is different, indicating that the metal composition of the head and the end is different. Combining the element surface scanning energy spectrum and line scanning energy spectrum, it can be seen that the metal composition of the head of the Janus Pd-AuPd melon seed-shaped nanomaterial is AuPd alloy, and the metal composition of the side and the end is Pd single metal.

[0046] The Janus Pd-AuPd melon seed-shaped nanomaterial prepared in Example 1 was mixed with carbon black, ethanol, and Nafion solution by ultrasound, and the mass ratio of Janus Pd-AuPd melon seed-shaped nanomaterial to carbon black was 1:4 to obtain a Janus Pd-AuPd / C ethanol solution. The Janus Pd-AuPd / C ethanol solution was added dropwise to a glassy carbon electrode as an oxygen reduction working electrode. A standard three-electrode system was used to perform a linear voltammetric scan in the potential range of 0.3V-1.2V (vs.RHE). The linear scanning voltammetric curve ( Figure 2 ) It can be concluded that the half-wave potential of Janus Pd-AuPd / C is at 0.882 V, showing excellent ORR catalytic activity, which is better than commercial Pt / C (the half-wave potential of commercial Pt / C is at 0.847 V).

[0047] Example 2

[0048] Soak all glassware in newly prepared aqua regia for 1 hour, wash with ultrapure water, and dry for later use.

[0049] (1) Add 100 mg of polyvinyl pyrrolidone, 364 mg of hexadecyltrimethylammonium bromide, 125 ul of 20 mM chloroauric acid solution, 125 ul of 20 mM chloropalladic acid solution, 40 ul of 102 mM silver nitrate solution and ultrapure water to a polytetrafluoroethylene liner and stir thoroughly to form a uniform mixed solution. The total volume of the mixed solution is 10 mL.

[0050] (2) The mixed solution was transferred to a reactor, which was sealed and filled with nitrogen to make the initial pressure of the reactor 1.0 MPa; the reactor was then transferred to an oil bath at 170° C. for reaction for 12 h.

[0051] (3) After the reaction is completed, the pressure in the reactor reaches 1.75 MPa. The reactor is taken out and placed in the air to cool naturally to room temperature. The reaction solution is transferred to a centrifuge tube for high-speed centrifugation at 11000 rpm / min, the resulting precipitate is washed, dispersed in ultrapure water for storage, and the resulting solution is the dispersion of Janus Pd-AuPd melon seed-shaped nanomaterials.

[0052] The transmission electron microscope photo of the Janus Pd-AuPd melon seed-shaped nanomaterial prepared in this example is shown in FIG. Figure 3 As shown, the Janus Pd-AuPd melon-seed-shaped nanomaterial has good uniformity; due to the deposition of Pd atoms on the sides and ends of the melon-seed morphology, its surface becomes rough.

[0053] Example 3

[0054] Soak all glassware in newly prepared aqua regia for 1 hour, wash with ultrapure water, and dry for later use.

[0055] (1) Add 150 mg of polyvinyl pyrrolidone, 430 mg of hexadecyltrimethylammonium bromide, 125 ul of 20 mM chloroauric acid solution, 125 ul of 20 mM sodium chloropalladate solution, 20 ul of 102 mM silver nitrate solution and ultrapure water to a polytetrafluoroethylene liner and stir thoroughly to form a uniform mixed solution. The total volume of the mixed solution is 10 mL.

[0056] (2) The mixed solution was transferred to a reactor, which was sealed and filled with nitrogen to make the initial pressure of the reactor 1.2 MPa; the reactor was then transferred to an oil bath at 190° C. for reaction for 8 h.

[0057] (3) After the reaction is completed, the pressure in the reactor reaches 1.85 MPa. The reactor is taken out and placed in the air to cool naturally to room temperature. The reaction solution is transferred to a centrifuge tube for high-speed centrifugation at 8000 rpm / min. The resulting precipitate is washed and dispersed in ultrapure water for storage. The resulting solution is a dispersion of Janus Pd-AuPd melon seed-shaped nanomaterials.

[0058] The transmission electron microscope photo of the Janus Pd-AuPd melon seed-shaped nanomaterial prepared in this example is shown in FIG. Figure 4 shown.

[0059] Comparative Example 1

[0060] Soak all glassware in newly prepared aqua regia for 1 hour, wash with ultrapure water, and dry for later use.

[0061] (1) Add 100 mg of polyvinyl pyrrolidone, 401 mg of hexadecyltrimethylammonium bromide, 125 ul of 20 mM chloroauric acid solution, 125 ul of 20 mM chloropalladic acid solution, 30 ul of 102 mM silver nitrate solution and ultrapure water to a polytetrafluoroethylene liner and stir thoroughly to form a uniform mixed solution. The total volume of the mixed solution is 10 mL.

[0062] (2) The mixed solution was transferred to a reactor, which was sealed and filled with nitrogen to make the initial pressure of the reactor 1.1 MPa; the reactor was then transferred to an oil bath at 180° C. for reaction for 3 h.

[0063] (3) After the reaction is completed, the pressure in the reactor reaches 1.8 MPa. The reactor is taken out and placed in the air to cool naturally to room temperature. The reaction solution is transferred to a centrifuge tube for high-speed centrifugation at 12000 rpm / min, and the resulting precipitate is washed and dispersed in ultrapure water for storage.

[0064] The transmission electron microscope photo of the product prepared in this comparative example is as follows Figure 5 As shown, its morphology is also melon seed-shaped, but the composition is AuPd alloy, recorded as AuPd nanoparticles. The difference between this comparative example and Example 1 is that the reaction time is shortened, indicating that in the early stage of the reaction, the gold precursor and the palladium precursor are co-reduced to generate melon seed-shaped alloy nanoparticles.

[0065] The AuPd nanoparticles prepared in Comparative Example 1 were mixed with carbon black, ethanol, and Nafion solution by ultrasound, with the mass ratio of AuPd nanoparticles to carbon black being 1:4, to obtain an AuPd / C ethanol solution; the AuPd / C ethanol solution was dripped onto a glassy carbon electrode as an oxygen reduction working electrode. A standard three-electrode system was used to perform a linear voltammetric scan in the potential range of 0.3V-1.2V (vs. RHE). The linear scanning voltammetric curve ( Figure 6 ) It can be concluded that the half-wave potential of AuPd / C is at 0.801V.

[0066] Comparative Example 2

[0067] Soak all glassware in newly prepared aqua regia for 1 hour, wash with ultrapure water, and dry for later use.

[0068] (1) Add 100 mg of polyvinyl pyrrolidone, 401 mg of hexadecyltrimethylammonium bromide, 125 ul of 20 mM chloroauric acid solution, 125 ul of 20 mM chloropalladic acid solution, 30 ul of 102 mM silver nitrate solution and ultrapure water to a polytetrafluoroethylene liner and stir thoroughly to form a uniform mixed solution. The total volume of the mixed solution is 10 mL.

[0069] (2) The mixed solution was transferred to a reactor, which was sealed and filled with nitrogen to make the initial pressure of the reactor 1.1 MPa; the reactor was then transferred to an oil bath at 180° C. for reaction for 6 h.

[0070] (3) After the reaction is completed, the pressure in the reactor reaches 1.8 MPa. The reactor is taken out and placed in the air to cool naturally to room temperature. The reaction solution is transferred to a centrifuge tube for high-speed centrifugation at 11000 rpm / min, and the resulting precipitate is washed and dispersed in ultrapure water for storage.

[0071] The transmission electron microscope photo of the product prepared in this comparative example is as follows Figure 7 As shown, when the reaction time is 6h, Pd atoms are partially deposited on the side of the melon seed-shaped AuPd nanoparticles to form islands, which are recorded as Pd-AuPd nanoparticles. Example 1 and Comparative Examples 1 and 2 illustrate the growth process of Janus Pd-AuPd nanomaterials, that is, the gold precursor and the palladium precursor are co-reduced to generate AuPd nanoparticles, and then Pd atoms are partially deposited on the side of the AuPd nanoparticles to generate Pd-AuPd nanoparticles. With the further deposition of Pd atoms and atomic diffusion, Janus Pd-AuPd nanomaterials are generated.

[0072] The Pd-AuPd nanoparticles prepared in Comparative Example 2 were mixed with carbon black, ethanol, and Nafion solution by ultrasound, with the mass ratio of Pd-AuPd nanoparticles to carbon black being 1:4, to obtain a Pd-AuPd / C ethanol solution; the Pd-AuPd / C ethanol solution was dripped onto a glassy carbon electrode as an oxygen reduction working electrode. A standard three-electrode system was used to perform a linear voltammetric scan in the potential range of 0.3V-1.2V (vs. RHE). The linear scanning voltammetric curve ( Figure 8 ) It can be concluded that the half-wave potential of Pd-AuPd / C is at 0.851 V. Combining Example 1 with Comparative Examples 1 and 2, it can be seen that the Janus Pd-AuPd nanomaterial has the most positive half-wave potential and exhibits excellent oxygen reduction electrocatalytic performance.

[0073] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A one-step preparation method of Janus Pd-AuPd melon seed-shaped nanomaterial, characterized in that: The following steps are involved: (1) Mix gold precursor, palladium precursor, Ag + The auxiliary agent, the reducing agent and the encapsulating agent are dispersed in water and stirred to obtain a mixed solution; (2) Under a protective atmosphere with an initial pressure of 1.0-1.2 MPa, the mixed solution is placed at 170-190 °C for reaction for 8-12 h, and the product is cooled, centrifuged, and washed to obtain a Janus Pd-AuPd melon seed-shaped nanomaterial; the head metal composition of the Janus Pd-AuPd melon seed-shaped nanomaterial is AuPd alloy, and the side and end metal compositions are Pd single metal; Step (1) Ag + The auxiliary agent is silver nitrate. The Ag in the mixed solution in step (1) + The concentration of the adjuvant was 0.204-0.408 mM; The reducing agent in step (1) is one or more of polyvinyl pyrrolidone, ascorbic acid, and sodium citrate, and the mass percentage concentration of the reducing agent in the mixed solution in step (1) is 0.95wt%-1.5wt%; The encapsulating agent in step (1) is one or more of hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride, and the mass percentage concentration of the encapsulating agent in the mixed solution in step (1) is 3.8 wt%-4.5 wt%.

2. The one-step preparation method of Janus Pd-AuPd melon seed-shaped nanomaterial according to claim 1, characterized in that: The gold precursor in step (1) is one or more of chloroauric acid and gold chloride; the concentration of the gold precursor in the mixed solution in step (1) is 0.25 mM; the palladium precursor in step (1) is one or more of chloropalladic acid, palladium chloride, and sodium chloropalladate; the concentration of the palladium precursor in the mixed solution in step (1) is 0.25 mM.

3. The one-step preparation method of Janus Pd-AuPd melon seed-shaped nanomaterial according to claim 1, characterized in that: The centrifugal speed in step (2) is 8000-12000 rpm / min; the protective atmosphere is nitrogen.

4. The one-step preparation method of Janus Pd-AuPd melon seed-shaped nanomaterial according to claim 1, characterized in that: The washing solution in step (2) is one or more of ultrapure water and ethanol solution.

5. Janus Pd-AuPd melon seed-shaped nanomaterial prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the Janus Pd-AuPd melon seed-shaped nanomaterial according to claim 5 in electrocatalytic oxygen reduction reaction under alkaline conditions.

7. The use according to claim 6, characterized in that: The Janus Pd-AuPd melon seed-shaped nanomaterial is used to prepare a working electrode, comprising the following steps: Carbon black, Janus Pd-AuPd melon seed-shaped nanomaterials, ethanol and Nafion are mixed and ultrasonically treated to obtain a Janus Pd-AuPd / C ethanol solution; the Janus Pd-AuPd / C ethanol solution is dropped onto a glassy carbon electrode and naturally air-dried to obtain an electrochemical working electrode for oxygen reduction reaction.

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