TW201700159A - Method for synthesizing truncated palladium nanocubes - Google Patents

Abstract

A method for synthesizing truncated palladium nanocubes includes providing a reaction solution containing palladium ion and 0.01-0.125 M cetyltrimethylammonium bromide; and mixing the reaction solution with L-ascorbic acid under a temperature of 70-120 DEG C. Each mole of said palladium ion is mixed with 3.2-19.2 mole of L-ascorbid acid. As such, the truncated palladium nanocubes contain (100) planes (111) planes at the same time.

Description

Method for preparing truncated palladium nano cube

The invention relates to a preparation method of palladium nanocrystals, in particular to a preparation method of a truncated palladium nanocrystal cube.

The crystal of palladium has good catalytic activity and can be used as a catalyst for various reactions, for example, for oxygen reduction reaction or formic acid oxidation. The palladium nanocrystals may have different crystal forms and sizes, for example, a palladium nanocube having a (100) plane, or a palladium nanooctahedron having a (111) plane, and may have different sizes.

The current research indicates that the catalytic activity of palladium nanocrystals is closely related to its crystal form, and palladium nanocrystals with different planes are suitable for different catalytic reactions. For example, when an oxygen reduction reaction is carried out in an aqueous perchloric acid solution, the catalytic efficiency of the palladium (100) plane is much larger than that of the palladium (111) plane. If more than two planes exist in a palladium nanocrystal, it can simultaneously have two different catalyst reactivity, and can be applied in a variety of different catalytic reactions. In addition, in general, smaller diameter palladium nanocrystals generally have better catalytic efficiency. Therefore, by regulating the type of palladium nanocrystals, the catalytic activity of the catalyst can be changed, and its applicability as a catalyst can be improved.

The preparation method of the conventional palladium nanocrystal is mixed with poly(vinylpyrrolidone), ascorbic acid (L-ascorbic acid), potassium chloride, potassium bromide and sodium chloropalladate (Na ₂ PdCl) in an aqueous solution. ₄ ), and heating and stirring at 80 ° C for 3 hours to form a palladium nano-cube having a (100) plane. However, the palladium nanocrystals obtained by the above method have only a single type of plane, and the application range is narrow, and there is still room for improvement.

SUMMARY OF THE INVENTION The object of the present invention is to provide a method for preparing a truncated palladium nanocube which has two planes at the same time.

The present invention provides a method for preparing a truncated palladium nanocube, comprising: providing a reaction solution comprising palladium ions and 0.01 to 0.025 M of cetyltrimethylammonium bromide; and 70~ The reaction solution was mixed with ascorbic acid at a temperature of 120 ° C; wherein, per mole of palladium ion was mixed with 3.2 to 19.2 moles of ascorbic acid.

The method for preparing a truncated palladium nanocube of the present invention, wherein the reaction solution is mixed with ascorbic acid at a temperature of 90 to 100 °C.

The method for producing a truncated palladium nanocube of the present invention, wherein the reaction solution is mixed with ascorbic acid at a temperature of 95 °C.

The method for producing a truncated palladium nanocube of the present invention, further comprising mixing the reaction solution with ascorbic acid, and then allowing to stand for 30 minutes to form a truncated palladium nanocrystal cube.

The method for preparing a truncated palladium nanocube of the present invention, wherein the palladium ion is derived from palladium nitrate (Pd(NO ₃ ) ₂ ), palladium acetate (Pd(OAc) ₂ ), palladium chloride (PdCl ₂ ), chlorine Sodium palladium (Na ₂ PdCl ₄ ), potassium hexachloropalladate (K ₂ PdCl ₆ ) or potassium tetrachloropalladate (K ₂ PdCl ₄ ).

The method for preparing a truncated palladium nanocube of the present invention, wherein the reaction solution comprises a solution of 500 μl of a palladium ion aqueous solution having a mixed concentration of 0.01 M and a solution of a cetyltrimethylammonium bromide aqueous solution having a concentration of 0.0125 M, 10 ml. .

The method for producing a truncated palladium nanocube according to the present invention, wherein the reaction solution is mixed with ascorbic acid, and the reaction solution is mixed with an aqueous solution of ascorbic acid having a concentration of 0.01 M.

The method for producing a truncated palladium nanocrystal of the present invention, wherein the aqueous palladium ion solution is an aqueous solution of chloropalladic acid (H ₂ PdCl ₄ ).

In the method for preparing a truncated palladium nanocube of the present invention, the truncated palladium nanocrystal cube can be prepared by mixing the reaction solution containing palladium ions and C ₁₆ TAB with ascorbic acid. The truncated palladium nanocube has both (100) and (111) planes, and can provide dual catalyst reactivity, thereby improving the applicability of the truncated palladium nanocube.

Furthermore, due to the method for preparing the truncated palladium nanocube of the present invention, by adjusting the ratio of ascorbic acid to palladium ions, a truncated palladium nanocrystal having a particle diameter of about 10 to 15 nm can be formed, and the truncated palladium can be reduced. The particle size of the rice cube, in turn, achieves the effect of improving the catalytic efficiency when the chopped palladium nano-cube is used for the catalytic reaction.

In addition, the preparation method of the truncated palladium nanocube of the present invention uses less preparation method than the conventional palladium nanocrystal, and the required heating time is shorter, so that the simplified preparation process can be achieved. Improve process efficiency and reduce energy consumption.

1‧‧‧(100) plane

2‧‧‧(111) plane

Figure 1 is a schematic view showing the structure of a truncated palladium nano-cube.

Figure 2a is a transmission electron micrograph of Group A1.

Figure 2b is a transmission electron micrograph of Group A2.

Figure 2c is a transmission electron micrograph of Group A3.

Figure 2d is a transmission electron micrograph of Group A4.

Figure 3 is a histogram of the crystal morphology distribution of palladium nanoparticles in Groups A1 to A4.

Figure 4a is a transmission electron micrograph of Group B1.

Figure 4b is a transmission electron micrograph of Group B2.

Figure 4c is a transmission electron micrograph of Group B3.

Figure 4d is a transmission electron micrograph of Group B4.

Figure 5 is a histogram of the crystal morphology distribution of palladium nanoparticles in Groups B1 to B4.

Figure 6a is a transmission electron micrograph of Group C1.

Figure 6b is a transmission electron micrograph of Group C2.

Figure 6c is a transmission electron micrograph of Group C3.

Figure 6d is a transmission electron micrograph of Group C4.

Figure 7 is a histogram of the crystal morphology distribution of palladium nanoparticles in Groups C1~C4.

Figure 8 is a high resolution transmission electron micrograph of Group C3.

Figure 9 is the X-ray diffraction spectrum of Group C3.

Figure 10 is an electron diffraction pattern of Group C3.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

The invention relates to a method for preparing a truncated palladium nanocube, which comprises mixing a reaction solution containing palladium ions and cetyltrimethylammonium bromide with ascorbic acid to obtain a truncated palladium nanocrystal cube.

The truncated palladium nanocubes of the present invention are in a cube having a (100) plane, forming a (111) plane at eight corners thereof, respectively. As shown in Fig. 1, the truncated palladium nano-cube has an octagonal (100) plane 1 and a triangular (111) plane 2, and the octagonal plane has 6 in total, and the triangular plane has 8 in total.

The palladium ion may be derived from any salt capable of dissociating to form palladium ions, such as palladium nitrate (Pd(NO ₃ ) ₂ ), palladium acetate (Pd(OAc) ₂ ), palladium chloride (PdCl ₂ ), sodium chloropalladate. (Na ₂ PdCl ₄ ), potassium hexachloropalladate (K ₂ PdCl ₆ ) or potassium tetrachloropalladate (K ₂ PdCl ₄ ), etc., are not limited in the present invention.

Cetyltrimethylammonium bromide (C ₁₆ TAB) is a surfactant which can be used as a nanoparticle capping agent and a structure-directing agent. The formation of an auxiliary truncated palladium metal cube.

More specifically, the above-mentioned salt containing palladium ions and C ₁₆ TAB may be dissolved together in water to form the reaction solution. Or, alternatively, it may be first prepared an aqueous solution of a palladium ion and an aqueous solution of a C ₁₆ TAB, continued mixing the palladium ion solution and the aqueous solution ₁₆ TAB C to form the reaction solution. For example, in the present embodiment, palladium chloride is dissolved in an aqueous hydrochloric acid solution to form an aqueous solution of monochloropalladium acid (H ₂ PdCl ₄ ), which is continuously mixed with the aqueous solution of C ₁₆ TAB.

Ascorbic acid is a reducing agent that can reduce palladium ions to form palladium metal. By adjusting the amount of ascorbic acid added relative to the palladium ion, different types of palladium nanocrystals can be formed. In this embodiment, ascorbic acid can be first dissolved in water to form an aqueous solution of ascorbic acid, which is continued for subsequent reaction.

In the present invention, the reaction solution and ascorbic acid are mixed at a temperature of 70 to 120 ° C. The reaction solution contains 0.01 to 0.025 M of C ₁₆ TAB, and 3.2 to 19.2 moles of ascorbic acid is mixed per mole of palladium ion. By the ratio of the above palladium ion to ascorbic acid, ascorbic acid can be reduced to palladium ions to form the truncated palladium nanocrystal cube. In addition, the chopped palladium nanocrystal cube can be formed by a suitable concentration of C ₁₆ TAB and a specific reaction temperature, and the formation of columnar or tetrahedral palladium nanocrystals can be avoided. If the reaction temperature is controlled at 90 to 100 ° C, the yield of the truncated palladium nanocube can be further improved.

The reaction solution can be prepared by mixing 0.01 ml of a 0.01 M aqueous solution of palladium ion in 0.0125 M of 10 ml of the C ₁₆ TAB aqueous solution, and by using the above ratio, the yield of the truncated palladium nanocube can be improved and The truncated palladium nano-cube is relatively uniform in size. For example, in the present embodiment, 0.01 ml of the aqueous solution of 0.01 mg of the aqueous solution of palladium palladium is mixed with 0.0125 M of 10 ml of the C ₁₆ TAB aqueous solution, and 0.1 M to 0.16 ml of the ascorbic acid aqueous solution is added at a temperature of 95 ° C. The mixture was mixed by electromagnetic stirring for 1 minute, and then allowed to stand for 30 minutes to form a truncated palladium nanocrystal having a particle diameter of about 10 to 15 nm.

The present invention provides a reaction solution containing palladium ions and 0.016 to 0.025M of C ₁₆ TAB, and mixes the reaction solution and ascorbic acid at a temperature of 70 to 120 ° C to mix 3.2 to 19.2 moles per mole of palladium ions. The ascorbic acid of the ear can be generated to form the truncated palladium nanocrystal cube. The above-mentioned truncated palladium nano-cube has both (100) plane and (111) plane, has dual catalyst reactivity, and can be more widely used in catalytic reactions.

In order to confirm the preparation method of the truncated palladium nanocube of the present invention, the truncated palladium nanocube cube can be surely formed by a specific reaction temperature and the ratio of palladium ion to ascorbic acid, and the following experiment is carried out.

(A) Effect of reaction temperature

Take 0.01 ml of this aqueous solution of chloropalladium acid in 0.5 ml and mix 0.015 M of 10 ml of the C ₁₆ TAB aqueous solution as the A1~A4 group, and add 0.1 M of the ascorbic acid aqueous solution at a different reaction temperature, and stir for 1 minute. After standing for 30 minutes, the reaction temperatures of the groups A1 to A4 are shown in Table 1 below.

The structure of the palladium nanocrystals formed in Groups A1 to A4 was observed by a transmission electron microscope as shown in Figures 2a to 2d. The morphology of each group of palladium nanocrystals was also analyzed, and a histogram as shown in Fig. 3 was drawn, and the particle size of the cube was recorded as shown in the first table. From the above results, it can be seen that at the temperature of 70-120 ° C, the formed palladium nanocrystals can be mainly cubic, especially in the group A2. At a temperature of 95 ° C, the yield of the palladium nano-cube is about 95%.

(B) Effect of C ₁₆ TAB concentration

Take 0.01 ml of this aqueous solution of chloropalladium acid in 0.5 ml and mix 10 ml of the C ₁₆ TAB aqueous solution at different concentrations as the B1~B4 group, and then add 0.1 M of the ascorbic acid aqueous solution at a temperature of 95 ° C, and stir for 1 minute. After standing for 30 minutes, the concentration of the C ₁₆ TAB aqueous solution in Groups B1 to B4 is shown in Table 2 below.

The structure of the palladium nanocrystals formed in Groups B1 to B4 was observed by a transmission electron microscope as shown in Figures 4a to 4d. The morphology of each group of palladium nanocrystals was also analyzed, and the histogram as shown in Fig. 5 was plotted, and the particle size of the cube was recorded as shown in the second table. From these results, the first B1, B2 group selected 0.0125 ~ 0.025M aqueous solution of the C ₁₆ TAB (i.e., the reaction solution contains 0.01 ~ 0.025M of C ₁₆ TAB), palladium nanocrystals can be formed in the The cube is dominant. In particular, in Group B2, 0.0125 M of the C ₁₆ TAB aqueous solution was used, and the yield of the palladium nanocube was about 95%.

(C) Effect of the amount of ascorbic acid added

Take 0.01M of 0.5 ml of the aqueous solution of chloropalladium acid and mix 0.015 M of 10 ml of the C ₁₆ TAB aqueous solution as the B1~B4 group, and then add different volumes of 0.1 M aqueous ascorbic acid solution at a temperature of 95 ° C, and stir for 1 minute. After standing for 30 minutes, the volume of the ascorbic acid aqueous solution added to the C1 to C4 groups is shown in Table 3 below.

The structure of the palladium nanocrystals formed in the C1 to C4 groups was observed by a transmission electron microscope as shown in Figs. 6a to 6d. The morphology of each group of palladium nanocrystals was also analyzed, and a histogram as shown in Fig. 7 was drawn, and the particle size of the cube was recorded as shown in the third table. From the above results, it is known that 0.16 to 0.96 ml of the ascorbic acid aqueous solution (that is, 3.2 to 19.2 moles of ascorbic acid per mole of palladium ion) is added, so that the formed palladium nanocrystals are mainly cubic, and the particles thereof The diameter can reach 10~15nm.

Further analysis of the above C2~C4 group shows that the formed palladium nanocrystals are mainly truncated palladium nanocrystals. Taking the C3 group as an example, the high-resolution transmission electron microscope image is shown in Fig. 8, and the X-ray diffraction spectrum analysis (XRD) is shown in Fig. 9, and the electron diffraction pattern is as shown in the figure. Figure 10 shows. The above data can confirm that, by the preparation method of the truncated palladium nano-cube of the present invention, it is indeed possible to generate a truncated palladium nano-cube having both a (100) plane and a (111) plane.

In summary, in the above method for producing a truncated palladium nanocube of the present invention, the truncated palladium nanocrystal cube can be prepared by mixing the reaction solution containing palladium ions and C ₁₆ TAB with ascorbic acid. The truncated palladium nanocube has both (100) and (111) planes, and can provide dual catalyst reactivity, thereby improving the applicability of the truncated palladium nanocube.

Furthermore, due to the method for preparing the truncated palladium nanocube of the present invention, by adjusting the ratio of ascorbic acid to palladium ions, a truncated palladium nanocrystal having a particle diameter of about 10 to 15 nm can be formed, and the truncated palladium can be reduced. The particle size of the rice cube, in turn, achieves the effect of improving the catalytic efficiency when the chopped palladium nano-cube is used for the catalytic reaction.

In addition, the preparation method of the truncated palladium nanocube of the present invention uses less preparation method than the conventional palladium nanocrystal, and the required heating time is shorter, so that the simplified preparation process can be achieved. Improve process efficiency and reduce energy consumption.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of the invention is defined by the scope of the appended claims.

Claims (8)

A method for preparing a truncated palladium nanocube comprises: providing a reaction solution comprising palladium ions and 0.01 to 0.025 M of cetyltrimethylammonium bromide; and 70 to 120 ° C The reaction solution is mixed with ascorbic acid at a temperature; wherein, each mole of palladium ion is mixed with 3.2 to 19.2 moles of ascorbic acid. The method for preparing a truncated palladium nanocube according to claim 1, wherein the reaction solution is mixed with ascorbic acid at a temperature of 90 to 100 °C. The method for producing a truncated palladium nanocube according to claim 2, wherein the reaction solution is mixed with ascorbic acid at a temperature of 95 °C. The method for preparing a truncated palladium nanocube according to claim 1, wherein the reaction solution is mixed with ascorbic acid and allowed to stand for 30 minutes to form a truncated palladium nanocube. The method for preparing a truncated palladium nanocube according to claim 1, wherein the palladium ion is derived from palladium nitrate (Pd(NO ₃ ) ₂ ), palladium acetate (Pd(OAc) ₂ ), and chlorinated. Palladium (PdCl ₂ ), sodium chloropalladate (Na ₂ PdCl ₄ ), potassium hexachloropalladate (K ₂ PdCl ₆ ) or potassium tetrachloropalladate (K ₂ PdCl ₄ ). The method for preparing a truncated palladium nanocube according to any one of claims 1 to 5, wherein the reaction solution comprises 500 μl of a palladium ion aqueous solution having a mixed concentration of 0.01 M and a concentration of 0.0125 M. 10 ml of an aqueous solution of cetyltrimethylammonium bromide. The method for producing a truncated palladium nanocube according to claim 6, wherein the reaction solution is mixed with ascorbic acid, and the reaction solution is mixed with an aqueous solution of ascorbic acid having a concentration of 0.1 M. The method for producing a truncated palladium nanocube according to claim 6, wherein the aqueous palladium ion solution is an aqueous solution of chloropalladium acid (H ₂ PdCl ₄ ).