CN107175105A - Graphene-supported palladium iridium nanoparticle catalyst preparation method and its Oxidation of Formic Acid electro-catalysis application - Google Patents

Abstract

The invention belongs to the technical field of preparation of supported catalysts, and in particular relates to a method for preparing a graphene-supported palladium-iridium nanoparticle catalyst and its electrocatalytic application for formic acid oxidation. The method comprises the following steps: 1) adding graphene to formic acid solution and ultrasonically mixing; 2) dispersing the mixed solution prepared by chloroiridic acid and sodium chloropalladate evenly under ultrasonic conditions; 3) mixing the mixed solution obtained in step 2) heating; 4) quickly inject the mixed solution obtained in step 3) into the mixed solution of graphene and formic acid in step 1), and perform ultrasonic treatment under sealed conditions; 5) the obtained product is dried after cleaning. The catalyst has a high electrochemical activity specific surface area and formic acid oxidation catalytic activity, and the method does not involve the use of highly toxic materials, is simple and convenient to operate, has high repeatability, and is suitable for large-scale production.

Description

Preparation method of graphene supported palladium iridium nanoparticle catalyst and its electrocatalysis for formic acid oxidation application

technical field

The invention belongs to the technical field of preparation of supported catalysts, and in particular relates to a method for preparing a graphene-supported palladium-iridium nanoparticle catalyst and its electrocatalytic application for formic acid oxidation.

Background technique

Direct formic acid fuel cells using liquid formic acid as fuel have high energy conversion efficiency and are environmentally friendly, and have shown great application potential as automobile power and portable power sources. Formic acid oxidation is an essential anode catalytic reaction for direct formic acid fuel cells. At present, the commonly used palladium/carbon catalysts have insufficient catalytic activity for formic acid oxidation and cannot meet the needs of current commercialization. In order to speed up the commercialization process of direct formic acid fuel cells, it is particularly important to research and prepare high-performance formic acid oxidation catalysts. Compared with palladium, iridium metal is relatively cheap, and iridium has high chemical stability to acids and is the most corrosion-resistant metal. Adding an appropriate amount of iridium to palladium can not only change the original electronic structure and surface structure of palladium, but also reduce the adsorption of poisonous species while reducing the activation energy of formic acid oxidation reaction, thus showing higher catalytic performance.

Catalytic reactions involve charge transfer processes at the surface of catalyst particles. Nanoparticles with small particle size and clean surface not only have ultra-high specific surface area and utilization rate, but also exhibit more active sites to promote the effective progress of catalytic reactions and the improvement of electrode process kinetics. The preparation of current small particle size uniform palladium iridium alloy particles often needs the help of surfactants (such as polyvinylpyrrolidone, cetyltrimethylammonium bromide) and highly toxic reducing agents (such as sodium borohydride, oleylamine , hydrazine hydrate), etc. Since the surfactant is easy to coat on the surface of the prepared metal nanoparticles and is difficult to remove, thus covering part of the active sites, the catalytic performance cannot be fully exerted; and the use of highly toxic reducing agents is likely to cause environmental pollution and pose a safety hazard. In addition, graphene has excellent electrical and mechanical properties and ultra-high specific surface area, which helps to reduce the charge transfer resistance and the mass transfer process effectively, and has been widely used as a catalyst carrier for fuel cells.

Therefore, it is of great significance to study a green method that is easy to operate and suitable for large-scale production to load surface-clean, ultra-small and uniformly dispersed palladium-iridium nanoparticles on the surface of graphene as a formic acid oxidation catalyst to accelerate the commercial development of direct formic acid fuel cells. .

Contents of the invention

In view of this, the object of the present invention is to provide an ultrasonic-assisted method to prepare graphene loaded surface clean ultra-small and uniformly dispersed palladium iridium nanoparticle catalyst, the prepared catalyst has a very high electrochemical activity specific surface area and formic acid oxidation catalytic activity, and The method does not involve the use of highly toxic materials, is easy to operate, has high reproducibility, and is suitable for large-scale production.

The technical scheme that the present invention adopts is as follows:

A preparation method of graphene supported palladium iridium nanoparticle catalyst, comprising the following steps:

1) adding graphene to the formic acid solution and ultrasonically mixing;

2) The mixed solution prepared by chloroiridic acid and sodium chloropalladate is uniformly dispersed under ultrasonic conditions;

3) heating the mixed solution obtained in step 2);

4) Step 3) the resulting mixed solution is quickly injected into the mixed solution of step 1) graphene and formic acid, and ultrasonic treatment is carried out under sealed conditions;

5) The obtained product is washed and then dried.

In the step 1), the concentration of the graphene in the formic acid solution is 1-5 mg/mL, and ultrasonic treatment is performed at 75-95°C.

In the step 2), the molar ratio of palladium to iridium is 1:1˜4:1.

In the step 2), the ultrasonic time is 0.5h-5h, and the power is 100-600W.

In the step 3), the solution is heated to 60°C-95°C.

In the step 4), the mass ratio of the palladium-iridium alloy to the graphene is 1:5˜1:1.

In the step 4), the ultrasonic treatment is carried out under the sealed condition of 60°C-95°C, the ultrasonic time is 2h-10h, and the power is 100-600W.

In the step 5), the drying temperature is 40°C-100°C, and the drying time is 10-20h.

The graphene-loaded palladium-iridium nanoparticle catalyst prepared by the method.

The application of the graphene-loaded palladium iridium nanoparticle catalyst in the electrocatalytic reaction of formic acid oxidation.

Compared with the commercial palladium/carbon catalyst, the palladium iridium/graphene prepared by the present invention has larger electrochemically active specific surface area and higher formic acid oxidation catalytic activity, and can replace the commercial palladium/carbon catalyst for direct formic acid fuel The field of batteries and other energy conversions has high practical value; and the method of the invention does not involve the use of highly toxic materials, is easy to operate, has high repeatability, can expand the preparation of other nanoparticles, and has a wide range of applications and prospects.

Description of drawings

In order to make the purpose, technical scheme and beneficial effect of the present invention clearer, the present invention provides the following drawings for illustration:

Fig. 1 is the transmission electron microscope figure of the palladium iridium/graphene catalyst prepared by embodiment 1;

Fig. 2 is the palladium iridium/graphene catalyst prepared in embodiment 1 and the commercialization palladium/carbon catalyst in _0.5MH SO _The cyclic voltammetry curve comparative figure in solution;

Fig. 3 is the palladium iridium/graphene catalyst prepared in embodiment 1 and the commercialized palladium/carbon catalyst in 0.5MH ₂ SO ₄ +0.5M HCOOH solution catalytic activity comparative figure;

Fig. 4 is the transmission electron microscope figure of the palladium iridium/graphene catalyst prepared by embodiment 2;

Fig. 5 is the palladium iridium/graphene catalyst prepared in embodiment 2 and the commercialization palladium/carbon catalyst in 0.5MH ₂ SO _The cyclic voltammetry curve comparative figure in solution;

Fig. 6 is the comparative figure of the catalytic activity of palladium iridium/graphene catalyst prepared in Example 2 and commercial palladium/carbon catalyst in 0.5MH ₂ SO ₄ +0.5M HCOOH solution;

Fig. 7 is the transmission electron microscope figure of the palladium iridium/graphene-1 catalyst prepared by embodiment 3;

Fig. 8 is the palladium iridium/graphene-1 catalyst prepared in embodiment 3 and commercialization palladium/carbon catalyst in 0.5MH ₂ SO ₄ solution in the cyclic voltammetry curve comparative figure;

Fig. 9 is the comparative diagram of the catalytic activity of the palladium iridium/graphene-1 catalyst prepared in Example 3 and the commercial palladium/carbon catalyst in 0.5MH ₂ SO ₄ +0.5M HCOOH solution;

Fig. 10 is the transmission electron microscope figure of the palladium iridium/graphene-2 catalyst prepared by embodiment 4;

Fig. 11 is the palladium iridium/graphene-2 catalyst prepared in embodiment 4 and commercialization palladium/carbon catalyst in 0.5MH ₂ SO ₄ solution in the cyclic voltammetry curve comparative figure;

Fig. 12 is a comparison chart of the catalytic activity of the palladium-iridium/graphene-2 catalyst prepared in Example 4 and the commercial palladium/carbon catalyst in 0.5M H ₂ SO ₄ +0.5M HCOOH solution.

detailed description

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Example 1

The preparation method of the palladium iridium/graphene high-performance formic acid oxidation catalyst of the present embodiment may further comprise the steps:

1) Add 15mg of graphene to 8mL of formic acid solution and mix uniformly by ultrasonic at 90°C, the ultrasonic power is 300W.

2) The mixed solution prepared by 0.286mL chloroiridic acid (7mg·mL ^-1 _Ir ) and 0.221mL sodium chloropalladate (20mg·mL ^-1 _Pd ) was sonicated for 1h, and the ultrasonic power was 300W.

3) Heat the solution homogeneously mixed in step 2) to 90°C.

4) Rapidly inject the mixed solution in step 3) into the mixed solution of graphene and formic acid in step 1), and perform ultrasonic treatment for 5 hours under sealed conditions at 90° C., and the ultrasonic power is 300W.

5) The product obtained by the reaction is washed and dried at 60° C. for 10 h, which is a palladium-iridium/graphene high-performance formic acid oxidation catalyst.

Fig. 1 is the transmission electron microscope figure of the palladium-iridium/graphene catalyst prepared in embodiment 1; From the figure, it can be clearly seen that ultra-small palladium-iridium alloy particles are evenly dispersed on the graphene surface, and the average particle diameter is about 3.4 nanometers.

Fig. 2 is the palladium iridium/graphene catalyst prepared in embodiment 1 and commercialization palladium/carbon catalyst in 0.5MH ₂ SO _The cyclic voltammetry curve comparative figure in solution; Find and commercialization palladium/carbon catalyst compared (26.6m ² g ^-1 ), the palladium iridium/graphene catalyst prepared in Example 1 shows a higher electrochemical activity specific surface area (76.3m ² g ^-1 ), indicating that the palladium iridium/graphene catalyst prepared in Example 1 has a higher many catalytically active sites.

Fig. 3 is the palladium iridium/graphene catalyst prepared in embodiment 1 and the current density comparison figure of commercialization palladium/carbon catalyst in 0.5MH ₂ SO ₄ +0.5M HCOOH solution; It is found that compared with commercialization palladium/carbon catalyst ( 286.1mA mg ^-1 _metal ), the palladium iridium/graphene catalyst prepared in Example 1 showed a higher peak current density (576.4mA mg ^-1 _metal ), and had a more negative The electrode potential shows that the palladium-iridium/graphene catalyst prepared in Example 1 has higher formic acid oxidation catalytic activity.

The above experimental data show that the palladium iridium/graphene catalyst prepared in Example 1 has more active specific surface area for formic acid oxidation and higher catalytic activity, so it can replace commercial palladium/carbon catalyst and be applied to direct formic acid fuel cell and other energy sources Convert field.

Example 2

The preparation method of the palladium iridium/graphene high-performance formic acid oxidation catalyst of the present embodiment may further comprise the steps:

1) Add 15 mg of graphene to 5 mL of formic acid solution and mix uniformly by ultrasonic at 80° C., and the ultrasonic power is 300 W.

2) The mixed solution prepared by 0.286mL chloroiridic acid (7mg·mL ^-1 _Ir ) and 0.221mL sodium chloropalladate (20mg·mL ^-1 _Pd ) was sonicated for 2h, and the ultrasonic power was 500W.

3) Heat the solution homogeneously mixed in step 2) to 80°C.

4) Rapidly inject the mixed solution in step 3) into the mixed solution of graphene and formic acid in step 1), and perform ultrasonic treatment for 8 hours under sealed conditions at 80° C., with an ultrasonic power of 500 W.

5) The product obtained by the reaction is washed and dried at 80° C. for 16 hours, which is a palladium-iridium/graphene high-performance formic acid oxidation catalyst.

Fig. 4 is the transmission electron micrograph of the palladium-iridium/graphene catalyst prepared in embodiment 2; From the figure, it can be clearly seen that ultra-small palladium-iridium alloy particles are evenly dispersed on the graphene surface, and the average particle diameter is about 3.6 nanometers.

Fig. 5 is the palladium iridium/graphene catalyst prepared in embodiment 2 and commercialization palladium/carbon catalyst in 0.5MH ₂ SO _The cyclic voltammetry curve comparative figure in solution; Find and commercialization palladium/carbon catalyst compared (26.6m ² g ^-1 ), the palladium iridium/graphene catalyst prepared in Example 2 shows a higher electrochemical activity specific surface area (74.6m ² g ^-1 ), illustrating that the palladium iridium/graphene catalyst prepared in Example 2 has more many catalytically active sites.

Fig. 6 is the palladium iridium/graphene catalyst prepared in embodiment 2 and the current density comparison figure of commercial palladium/carbon catalyst in 0.5MH ₂ SO ₄ +0.5M HCOOH solution; It is found that compared with commercial palladium/carbon catalyst ( 286.1mA mg ^-1 _metal ), the palladium iridium/graphene catalyst prepared in Example 2 showed a higher peak current density (509.9mA mg ^-1 _metal ), while having a more negative The electrode potential shows that the palladium iridium/graphene catalyst prepared in Example 2 has higher catalytic activity for formic acid oxidation.

The above experimental data show that the palladium iridium/graphene catalyst prepared in Example 2 has more formic acid oxidation activity specific surface area and higher catalytic activity, thereby it can replace commercial palladium/carbon catalyst and be applied to direct formic acid fuel cell and other energy sources Convert field.

Example 3

The preparation method of the palladium iridium/graphene formic acid oxidation catalyst of the present embodiment may further comprise the steps:

1) Add 15 mg of graphene to 8 mL of sodium borohydride aqueous solution (2 mg/mL) and mix uniformly by ultrasonic at 90° C. with an ultrasonic power of 300 W.

2) The mixed solution prepared by 0.286mL chloroiridic acid (7mg·mL ^-1 _Ir ) and 0.221mL sodium chloropalladate (20mg·mL ^-1 _Pd ) was sonicated for 1h, and the ultrasonic power was 300W.

3) Heat the solution homogeneously mixed in step 2) to 90°C.

4) Rapidly inject the mixed solution in step 3) into the mixed solution of graphene and sodium borohydride in step 1), and perform ultrasonic treatment for 5 hours under sealed conditions at 90° C., and the ultrasonic power is 300W.

5) The product obtained by the reaction is washed and dried at 60° C. for 10 h, which is the palladium iridium/graphene-1 formic acid oxidation catalyst.

Figure 7 is a transmission electron microscope image of the palladium iridium/graphene-1 catalyst prepared in Example 3; it can be clearly seen from the figure that the palladium iridium alloy particles are dispersed on the graphene surface, but the particle size span is large and inhomogeneous.

Fig. 8 is the palladium iridium/graphene-1 catalyst prepared by embodiment 3 and the commercialization palladium/carbon catalyst in 0.5MH ₂ SO _The cyclic voltammetry curve comparison figure in the solution; Find and commercialization palladium/carbon catalyst compared ( 26.6m ² g ^-1 ), the palladium/graphene-1 catalyst prepared in Example 3 showed a higher electrochemical activity specific surface area (49.6m ² g ^-1 ), illustrating that the palladium iridium/graphene prepared in Example 3 -1 catalyst has more catalytic active sites.

Fig. 9 is the comparison diagram of the current density of palladium iridium/graphene-1 catalyst prepared in Example 3 and commercial palladium/carbon catalyst in 0.5MH ₂ SO ₄ +0.5M HCOOH solution; discovery and commercial palladium/carbon catalyst phase than (286.1mA mg ^-1 _metal ), the palladium iridium/graphene catalyst prepared in Example 3 shows a higher peak current density (374.2mA mg ^-1 _metal ), and has a relatively Negative electrode potential shows that the palladium iridium/graphene catalyst prepared in Example 3 has certain formic acid oxidation catalytic activity.

Above-mentioned experimental data shows, the formic acid oxidation activity specific surface area and catalytic activity of palladium iridium/graphene-1 catalyst that adopt sodium borohydride to prepare in embodiment 3 are all higher than commercial palladium/carbon catalyst but all lower than embodiment 1 and implementation The palladium iridium/graphene catalyst prepared in example 2.

Example 4

The preparation method of the palladium iridium/graphene formic acid oxidation catalyst of the present embodiment may further comprise the steps:

1) Add 15mg of graphene to 8mL of formic acid solution and mix uniformly by ultrasonic at 90°C, the ultrasonic power is 300W.

2) The mixed solution prepared by 0.286mL chloroiridic acid (7mg·mL ^-1 _Ir ) and 0.221mL sodium chloropalladate (20mg·mL ^-1 _Pd ) was sonicated for 1h, and the ultrasonic power was 300W.

3) Heat the solution homogeneously mixed in step 2) to 90°C.

4) Rapidly inject the mixed solution in step 3) into the mixed solution of graphene and formic acid in step 1), and stir for 5 hours at 90° C. under sealed conditions.

5) The product obtained by the reaction is washed and dried at 60° C. for 10 h, which is the palladium iridium/graphene-2 formic acid oxidation catalyst.

Fig. 10 is the transmission electron micrograph of the palladium-iridium/graphene-2 catalyst prepared in Example 4; it can be clearly seen from the figure that the palladium-iridium alloy particles are dispersed on the graphene surface, but its particle size span is large and inhomogeneous.

Fig. 11 is the palladium iridium/graphene-2 catalyst prepared in embodiment 4 and the commercialization palladium/carbon catalyst in 0.5MH ₂ SO _The cyclic voltammetry curve comparative figure in the solution; Find and commercialization palladium/carbon catalyst compared ( 26.6m ² g ^-1 ), the palladium/graphene-1 catalyst prepared in Example 4 shows a higher electrochemical activity specific surface area (46.3m ² g ^-1 ), illustrating that the palladium iridium/graphene prepared in Example 4 -2 catalyst has more catalytic active sites.

Fig. 12 is the comparison diagram of the current density of palladium iridium/graphene-2 catalyst prepared in Example 4 and commercial palladium/carbon catalyst in 0.5MH ₂ SO ₄ +0.5M HCOOH solution; discovery and commercial palladium/carbon catalyst phase than (286.1mA mg ^-1 _metal ), the palladium iridium/graphene-2 catalyst prepared in Example 4 showed a higher peak current density (350.2mA mg ^-1 _metal ), and at the same time in the forward sweep process under the same current density It has a relatively negative electrode potential, indicating that the palladium iridium/graphene-2ene catalyst prepared in Example 4 has certain formic acid oxidation catalytic activity.

Above-mentioned experimental data shows, the formic acid oxidation activity specific surface area and catalytic activity of palladium iridium/graphene-2 catalyst prepared by the embodiment 4 of step 4) without ultrasonic treatment are all higher than commercial palladium/carbon catalyst but are all lower than implementation The palladium iridium/graphene catalyst prepared in example 1 and embodiment 2.

Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that it can be described in terms of form and Various changes may be made in the details without departing from the scope of the invention defined by the claims.

Claims (10)

1. a kind of preparation method of graphene-supported palladium iridium nanoparticle catalyst, it is characterised in that：Comprise the following steps：

1) that graphene is added into ultrasonic mixing in formic acid solution is uniform；

2) it is uniformly dispersed under the mixed solution ultrasound condition that chloro-iridic acid and the sour sodium of chlorine palladium are prepared；

3) by step 2) gained mixed solution heating；

4) by step 3) gained mixed solution is rapidly injected step 1) in the mixed solution of graphene and formic acid, in air-proof condition Lower progress is ultrasonically treated；

5) the once purged drying of products therefrom, you can.

2. the preparation method of graphene-supported palladium iridium nanoparticle catalyst according to claim 1, it is characterised in that：Institute State step 1) in, concentration of the graphene in formic acid solution is 1~5mg/mL, ultrasonically treated in being carried out at 75-95 DEG C.

3. the preparation method of graphene-supported palladium iridium nanoparticle catalyst according to claim 1, it is characterised in that：Institute State step 2) in, the mol ratio of palladium and iridium is 1:1~4:1.

4. the preparation method of the graphene-supported palladium iridium nanoparticle catalyst according to claim 1 or 3, its feature exists In：The step 2) in, ultrasonic time is 0.5h~5h, and power is 100~600W.

5. the preparation method of graphene-supported palladium iridium nanoparticle catalyst according to claim 1, it is characterised in that：Institute State step 3) in, solution is heated to 60 DEG C~95 DEG C.

6. the preparation method of graphene-supported palladium iridium nanoparticle catalyst according to claim 1, it is characterised in that：Institute State step 4) in, the mass ratio of palladium iridium alloy and graphene is 1:5~1:1.

7. the preparation method of the graphene-supported palladium iridium nanoparticle catalyst according to claim 1 or 6, its feature exists In：The step 4) in, carried out under 60 DEG C~95 DEG C air-proof conditions ultrasonically treated, ultrasonic time is 2h~10h, and power is 100~600W.

8. the preparation method of graphene-supported palladium iridium nanoparticle catalyst according to claim 1, it is characterised in that：Institute State step 5) in, drying temperature is 40 DEG C~100 DEG C, and the time is 10~20h.

9. a kind of graphene-supported palladium iridium nano particle catalysis prepared such as claim 1-8 any one methods describeds Agent.

10. a kind of graphene-supported palladium iridium nanoparticle catalyst as claimed in claim 9 is in Oxidation of Formic Acid electrocatalytic reaction In application.