KR101814162B1 - Formic acid dehydrogenation catalyst and method of manufacturing the same - Google Patents

Abstract

One embodiment of the present invention is a method of manufacturing a carbon-based support, comprising: preparing a nitrogen-carbon support by doping a carbon-based support with nitrogen (N); And supporting a palladium (Pd) nanoparticle on the nitrogen-carbon support to form a supported catalyst; And a formic acid dehydrogenation catalyst prepared by such a method. Accordingly, it is an object of the present invention to provide a formic acid dehydrogenation catalyst which is excellent in activity at low temperature, high in TOF (Trunover Frequency), excellent in catalyst stability, mass-producible, And a process for producing the same.

Description

FORMIC ACID DEHYDROGENATION CATALYST AND METHOD OF MANUFACTURING THE SAME Field of the Invention < RTI ID = 0.0 >

The present invention relates to a formic acid dehydrogenation catalyst and a process for its preparation.

Recently, efforts are being made to develop new low-carbon energy for solving energy and environmental problems. As one of such low-carbon energy technologies, fuel cell utilization technology has been proposed. This fuel cell technology utilizes the potential difference generated during the oxidation or dehydrogenation of fuel to produce electricity.

A typical example of the fuel used in such a fuel cell is formic acid. Formic acid has a good hydrogen storage density of 53 g / L at room temperature, which is superior to the existing hydrogen storage gas of 14.7 g / L at 350 bar of compressed hydrogen gas. Such formic acid is used as a fuel in direct formic acid fuel cell (DFAFC) or polymer electrolyte membrane fuel cell (PEMFC), and is used as an environmentally friendly energy source. For example, when formic acid is used as a fuel for a PEMFC, formate hydrogen is produced from formic acid at room temperature using formic acid dehydrogenation catalyst. In connection with the fuel cell, , Political development, and so on.

Conventionally, a platinum (Pt) catalyst is used as a formic acid dehydrogenation catalyst, but platinum is poisoned by carbon monoxide (CO), which is a reaction intermediate, and is easily degraded in performance. To develop a catalyst having excellent formic acid oxidation ability is very important for the commercialization of formic acid hydrogenation. Particularly, a method of using palladium (Pd) for replacing expensive platinum has been proposed, but palladium has low stability, so it is difficult to maintain its activity for a long time and it is difficult to realize high activity.

Accordingly, there is an increasing demand for a catalyst having excellent formic acid oxidizing ability and high stability while using a material having a low cost.

It is an object of the present invention to provide a process for producing a catalyst which is excellent in activity at low temperature, has high TOF (Trunover Frequency), excellent catalyst stability, mass production, Catalyst and a method for producing the same.

One embodiment of the present invention is a method of manufacturing a carbon-based support, comprising: preparing a nitrogen-carbon support by doping a carbon-based support with nitrogen (N); And supporting a palladium (Pd) nanoparticle on the nitrogen-carbon support to form a supported catalyst; To a process for preparing a formic acid dehydrogenation catalyst.

The step of preparing the nitrogen-carbon support may include adsorbing the amine-based functional groups on the porous carbon-based support and doping the nitrogen atoms into the structure of the porous carbon-based support.

The step of preparing the nitrogen-carbon support may include reacting the aqueous solution of the nitrogen precursor with the porous carbon-based support, and then removing water to prepare the carbon-based support on which the nitrogen precursor is adsorbed.

The step of preparing the nitrogen-carbon support may include pyrolyzing the carbon-based support on which the nitrogen precursor has been adsorbed at a temperature of 500 ° C to 600 ° C, and doping nitrogen atoms in the structure of the carbon-based support.

The step of preparing the supported catalyst may include reacting the palladium precursor aqueous solution with the nitrogen-carbon support, and then reducing the palladium nanoparticles supported on the nitrogen-carbon support.

The nitrogen-carbon support may be controlled to have a hollow structure.

The average particle size of the palladium nanoparticles can be controlled to 2 nm to 7 nm.

Another embodiment of the present invention is a nitrogen-carbon support doped with nitrogen (N) atoms; And a palladium (Pd) nanoparticle supported on the nitrogen-carbon support.

The formic acid dehydrogenation catalyst may have a doped nitrogen atom content of 3 wt% to 9 wt%.

The formic acid dehydrogenation catalyst may have a content of supported palladium nanoparticles of 1 wt% to 9 wt%.

The nitrogen-carbon support may have a hollow structure.

The palladium nanoparticles may have an average particle diameter of 2 nm to 7 nm.

Another embodiment of the present invention is directed to a fuel cell comprising a formic acid dehydrogenation catalyst as described above.

Another embodiment of the present invention relates to a hydrogen generator comprising a formic acid dehydrogenation catalyst as described above.

The present invention relates to a formic acid dehydrogenation catalyst which is excellent in activity at a low temperature and has a high conversion frequency (TOF, Trunover Frequency), excellent catalyst stability, mass production, Method can be provided.

1 is a transmission electron microscope (TEM) photograph of a formic acid dehydrogenation catalyst of Example 1 of the present invention.
2 is a scanning transmission electron microscope (STEM) photograph of the formic acid dehydrogenation catalyst of Example 1 of the present invention.
3 is a photograph showing the result of element mapping analysis of the formic acid dehydrogenation catalyst of Example 1 of the present invention with a high-angle annular night-light scanning transmission microscope (HADDF-STEM).
4 is a graph showing the results of X-ray diffraction analysis of Example 1 of the present invention.
5 is a graph showing the degree of hydrogen generation in the formic acid dehydrogenation catalyst of Example 1 of the present invention.
6 is a graph showing the evaluation results of formic acid decomposition activity of Example 1 of the present invention and Comparative Examples 1 and 2.
7 is a graph showing the conversion frequency (TOF) evaluation results of Example 1 of the present invention and Comparative Examples 1 and 2. FIG.

One embodiment of the present invention is a method of manufacturing a carbon-based support, comprising: preparing a nitrogen-carbon support by doping a carbon-based support with nitrogen (N); And supporting a palladium (Pd) nanoparticle on the nitrogen-carbon support to form a supported catalyst; To a process for preparing a formic acid dehydrogenation catalyst. Accordingly, it is an object of the present invention to provide a formic acid dehydrogenation catalyst which is excellent in activity at low temperature, high in TOF (Trunover Frequency), excellent in catalyst stability, mass-producible, Can be provided. The formic acid dehydrogenation catalysts prepared by this method can enhance the catalytic performance of palladium (Pd) nanoparticles by increasing the electron density of palladium (Pd) atoms through nitrogen doping, improve the thermal stability of the catalyst, It is possible to suppress the agglomeration between the catalyst particles and simultaneously realize the advantages of excellent activity and high durability. In addition, the advantages of homogeneous catalysts and heterogeneous catalysts can be achieved at the same time.

The process for preparing a formic acid dehydrogenation catalyst of one embodiment comprises first preparing a nitrogen-carbon support by doping nitrogen (N) on a carbon-based support. The step of preparing the nitrogen-carbon support can stabilize the formic acid dehydrogenation catalyst and enhance the low-temperature activity by doping nitrogen atoms into the structure of the carbon-based support.

The carbon-based support may specifically include at least one of carbon black, activated carbon, carbon nanotube, carbon fiber, fullerene, and graphene. These may be used singly or in combination of two or more. When such a carbon-based support is used, the nitrogen-carbon support serves as a heterogeneous carrier, and a more advantageous effect can be obtained in separating the reaction by-product and the produced catalyst after the production of the formic acid dehydrogenation catalyst. Further, such a carbon-based scaffold is excellent in economical efficiency because the supply source is stable.

More specifically, the carbon-based support may be carbon black, which is a porous carbon-based support. In this case, it is advantageous to dope the nitrogen atom into the carbon-based support, which is advantageous for mass production, and the surface area can be widened to further improve the activity of the catalyst. For example, the carbon black that is the porous carbon-based support may be ketjen black. In this case, the carbon-based support can provide a more stable and more stable formic acid dehydrogenation catalyst with a better surface area.

The step of preparing the nitrogen-carbon support may include adsorbing the amine-based functional groups on the porous carbon-based support and substituting nitrogen atoms for some carbon atoms in the porous carbon-based support structure using adsorbed amine-based functional groups. In this case, nitrogen atoms can be uniformly and efficiently doped into the structure of the porous carbon-based support, and the fixing power of the palladium nanoparticles and the nitrogen-carbon support can be improved.

The step of preparing the nitrogen-carbon support may include reacting the aqueous solution of the nitrogen precursor with the porous carbon-based support, and then removing water to prepare the carbon-based support on which the nitrogen precursor is adsorbed.

Specifically, the step of preparing the nitrogen-carbon support may include adding a porous carbon-based support to an aqueous solution of nitrogen precursor, and then stirring the solution at a temperature of 50 ° C to 70 ° C to prepare a carbon-based support on which a nitrogen precursor is adsorbed . The stirring can be performed until all of the water is evaporated. In this case, the carbon-based support on which the nitrogen precursor is adsorbed can improve the dispersion and homogeneity of the doped nitrogen in the structure, and is advantageous for controlling the doping amount of nitrogen.

The step of preparing the nitrogen-carbon support may include heat treating the carbon-based support on which the nitrogen precursor has been adsorbed at a temperature of 500 ° C to 600 ° C and a nitrogen (N) gas atmosphere to thereby form a nitrogen- . In this case, the doped nitrogen atom can form a new bond with the carbon atoms in the carbon-based support, while at the same time producing a reaction site capable of interacting with the palladium nanoparticles. As a result, it is possible to provide a formic acid dehydrogenation catalyst having an excellent reaction rate and further improved low-temperature activity.

The nitrogen-carbon support prepared through the step of producing the nitrogen-carbon support may include, for example, a hollow structure. In this case, the nitrogen-carbon support may have a further improved surface area and thus a better catalytic activity.

The step of preparing the nitrogen-carbon support may include controlling the content of doped nitrogen to 3 wt% to 9 wt%. Within the above range, the stability of the palladium can be further improved, and the activity of the formic acid dehydrogenation catalyst can be further improved.

The method for producing a formic acid dehydrogenation catalyst comprises carrying the palladium nano-particles on the nitrogen-carbon support to prepare a supported catalyst. In this case, the palladium nanoparticles and the nitrogen-carbon carrier interact to each other to have a more advantageous effect of shifting the electron density from the nitrogen atom to the palladium. This can stabilize the palladium nanoparticles and improve the activity of the catalyst by lowering the cohesive force between the palladium nanoparticles or the catalyst particles.

The step of preparing the supported catalyst may include reacting the palladium precursor aqueous solution with the nitrogen-carbon support, and then reducing the palladium nanoparticles supported on the nitrogen-carbon support. In this case, the supported catalyst plays a role similar to the homogeneous catalyst through the palladium nanoparticles, realizing high activity and further improving the recoverability after the reaction.

The step of preparing the supported catalyst may include controlling the content of the supported palladium nanoparticles to 1 wt% to 9 wt%. Within the above range, the stability and activity of the formic acid dehydrogenation catalyst can be more excellent.

The method for preparing the formic acid dehydrogenation catalyst may include controlling the average particle diameter of the palladium nanoparticles to 2 nm to 7 nm. In this case, the palladium nanoparticles and the doped nitrogen atoms can further promote interaction sites to generate reaction sites.

Another embodiment of the present invention is a nitrogen-carbon support doped with nitrogen (N) atoms; And a palladium (Pd) nanoparticle supported on the nitrogen-carbon support. The formic acid dehydrogenation catalyst of this embodiment can be prepared by the above-described preparation method. In addition, the formic acid dehydrogenation catalyst of this embodiment is capable of mass production, has excellent formic acid dehydrogenation activity at a low temperature, has high TOF (Trunover Frequency), and is excellent in catalyst stability. In particular, it is possible to realize a high activity similar to a homogeneous catalyst, and at the same level of degree of separation after the reaction as the heterogeneous catalyst, an advantageous effect can be realized.

The formic acid dehydrogenation catalyst may have a doped nitrogen atom content of 3 wt% to 9 wt%. Within the above range, the stability of the palladium can be further improved, and the activity of the formic acid dehydrogenation catalyst can be further improved.

The formic acid dehydrogenation catalyst may have a content of supported palladium nanoparticles of 1 wt% to 9 wt%. Within the above range, the stability and activity of the formic acid dehydrogenation catalyst can be more excellent.

The nitrogen-carbon support may have a hollow structure, and the palladium nanoparticles may have an average particle diameter of 2 nm to 7 nm. In this case, the formic acid dehydrogenation catalyst can promote the reaction site formation of the doped nitrogen atom and the palladium nanoparticles, and the stability and activity can be further improved.

Another embodiment of the present invention is directed to a fuel cell comprising a formic acid dehydrogenation catalyst as described above.

Another embodiment of the present invention relates to a hydrogen generator comprising a formic acid dehydrogenation catalyst as described above.

The fuel cell or the hydrogen generator including the formic acid dehydrogenation catalyst of the present invention is excellent in activity at low temperature and high in conversion efficiency (TOF, Trunover Frequency) of the catalyst, so that power generation efficiency or hydrogen generation efficiency is high and durability is maintained for a long time .

Example

Hereinafter, examples and comparative examples of the present invention will be described. It should be understood, however, that these examples are provided for illustration only and are not intended to limit the scope of the present invention.

Example  One

10 g of the nitrogen precursor dicyandiamide was dissolved in 100 ml of distilled water and stirred at room temperature to prepare a nitrogen precursor aqueous solution. 5 g of ketjen black was added to the nitrogen precursor aqueous solution to completely disperse the nitrogen precursor solution. The nitrogen precursor and ketjen black were reacted with stirring for 4 hours while maintaining the temperature at 100 ° C. Thereafter, the mixture was stirred at a temperature of about 60 캜 for about 24 hours until all of the distilled water was evaporated to prepare a carbon precursor-adsorbed carbon support. The nitrogen precursor adsorbed carbon support thus obtained was pyrolysed in a nitrogen atmosphere at 550 캜 for 4 hours to prepare a nitrogen-carbon support having a nitrogen-doped layer in the structure of the carbon-based support.

1 g of a palladium precursor Pd (NO ₃ ) ₂ .2H ₂ O was dissolved in 25 ml of distilled water to prepare a palladium precursor aqueous solution. 4 g of the nitrogen-carbon support formed with the nitrogen-doped layer prepared above was added to the Pd precursor aqueous solution, followed by stirring and dispersing well at room temperature. Then, 10 equivalents of NaBH ₄ was added and the mixture was stirred for 1 hour to carry out a reduction reaction. After completion of the reduction reaction, the mixture was filtered, repeatedly washed with water and ethanol, and dried at about 60 ° C. for about 24 hours until all of the distilled water was evaporated to carry palladium nanoparticles on the nitrogen- 4.58 g of formic acid dehydrogenation catalyst was prepared.

Comparative Example  One

1 g of a palladium precursor Pd (NO ₃ ) ₂ .2H ₂ O was dissolved in 25 ml of distilled water to prepare a palladium precursor aqueous solution. 4 g of ketjen black was added to the palladium precursor aqueous solution, followed by stirring and dispersing well at room temperature. Then, 10 equivalents of NaBH ₄ was added and the mixture was stirred for 1 hour to carry out a reduction reaction. After completion of the reduction reaction, the mixture was filtered, repeatedly washed with water and ethanol, and then dried at about 60 ° C for about 24 hours until all the distilled water was evaporated to obtain palladium on the carbon-based support. Was prepared.

Comparative Example  2

The procedure of Comparative Example 1 was repeated except that 4 g of aluminum oxide carrier (Al ₂ O ₃ ) was used instead of 4 g of ketjen black in the aqueous solution of palladium precursor, Was prepared.

<Characteristic Analysis>

1. Structure analysis of catalyst

(1) Analysis method: The formic acid dehydrogenation catalyst prepared in Example 1 was analyzed by transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and high-angle annular dark- field scanning transmission electron microscopy (HAADF-STEM) images.

(2) Results of analysis: The transmission electron microscope (TEM) image of Example 1 is shown in FIG. 1, the scanning electron microscope (STEM) image is shown in FIG. 2, and the high angle annular night vision scanning transmission microscope image is shown in FIG. 1 and 3, it was confirmed that the nitrogen-carbon support of Example 1 had a hollow structure.

From the results of FIG. 1, it was confirmed that the formic acid dehydrogenation catalyst of Example 1 uniformly dispersed the palladium nanoparticles having an average particle diameter of 5 nm on the nitrogen-carbon support.

From the result of the element mapping analysis of FIG. 3, it was confirmed that the nitrogen-doped layer was uniformly formed on the nitrogen-carbon support.

2. Palladium nanoparticles Bearing  Confirm

(1) Analysis method: X-ray diffraction spectroscopy (XRD), energy dispersive X-ray spectroscopy (EDX) and inductively coupled plasma spectrophotometer (ICP-OES) were used for the formic acid dehydrogenation catalyst prepared in Example 1 Analysis was performed.

(2) Analysis result: X-ray diffraction spectroscopy (XRD) results of Example 1 are shown in FIG. 4, a carbon crystal peak formed in the same region as the nitrogen-carbon support and an independently formed palladium (Pd) crystal peak were identified. It was confirmed that the palladium nanoparticles were well adhered on the nitrogen-carbon support.

Analysis of the formic acid dehydrogenation catalyst of Example 1 using an energy dispersive X-ray analyzer (EDX) and an inductively coupled plasma spectrophotometer (ICP-OES) revealed that 7.3 wt% of palladium was supported .

3. Evaluation of stability of catalyst

(1) Analytical method: 1 g of the formic acid dehydrogenation catalyst prepared in Example 1 was added to the reactor, and an aqueous solution of sodium formate (0.05 mol) was added. Then, formic acid was continuously supplied to the reactor at a rate of 6.0 mL / h using a syringe pump for 3 hours, and the degree of hydrogen evolution was measured to evaluate the stability.

(2) Analysis result: The hydrogen production degree of the formic acid dehydrogenation catalyst prepared in Example 1 was measured, and the result is shown in FIG. 5, it was confirmed that an average of 40 mL of hydrogen gas was generated constantly per minute. As a result, when the formic acid dehydration catalyst prepared in Example 1 continuously supplied formic acid for 3 hours, it was confirmed that the stability of the catalyst was very high because the reaction did not decrease and the reaction continued.

3. Catalytic activity And switching frequency (TOF)  evaluation

(1) Analytical method: In order to confirm the decomposition performance of the catalyst prepared in Example 1 and Comparative Examples 1 and 2, degree of decomposition of formic acid and conversion frequency were measured and evaluated. First, the catalyst of Example 1 and Comparative Examples 1 and 2 was added to a 1 M aqueous solution of formic acid at room temperature while reducing the amount of palladium (Pd) to 0.1 mol%. Then, the amount of gas generation and the conversion frequency were measured according to the elapsed time after the agitation.

(2) Results of analysis: The degree of hydrogen evolution of the formic acid dehydrogenation catalyst prepared in Example 1 and Comparative Examples 1 and 2 was measured, and the results of the conversion frequency measurement are shown in FIG.

6, it was confirmed that the catalyst of Example 1 of the present invention exhibited excellent activity for the decomposition reaction of formic acid under the same conditions and achieved high reactivity. The catalyst of Example 1 was 1.5 times more reactive than the catalyst of Comparative Example 1.

Also, it was confirmed through FIG. 7 that the catalyst of Example 1 of the present invention had a higher conversion frequency and higher reactivity under the same conditions. It was confirmed that the conversion of the catalyst of Example 1 was improved by about 25% as compared with the catalyst of Comparative Example 1.

While the present invention has been described in connection with what is presently considered to be fictitious by those skilled in the art, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. It will be understood that various modifications and changes may be made in the present invention. Accordingly, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

101: Peak analysis results of nitrogen-carbon support crystals
102: Crystal peak analysis result of formic acid dehydrogenation catalyst

Claims (14)

Carbon support by adsorbing a nitrogen precursor on the carbon-based support followed by pyrolysis to form a nitrogen-carbon support in the form of a doped nitrogen atom forming a bond with carbon atoms in the carbon-based support; And
Supporting palladium (Pd) nanoparticles on the nitrogen-carbon support to produce a supported catalyst; Lt; RTI ID = 0.0 &gt; of &lt; / RTI &gt; formic acid dehydrogenation catalyst.
The method according to claim 1,
Wherein the step of preparing the nitrogen-carbon support comprises adsorbing an amine-based functional group on a porous carbon-based support and doping a nitrogen atom in the structure of the porous carbon-based support.
The method according to claim 1,
The step of preparing the nitrogen-carbon support comprises reacting a nitrogen precursor aqueous solution with a porous carbon-based support, and then removing moisture to prepare a carbon-based support having the nitrogen precursor adsorbed thereon.
The method of claim 3,
The step of preparing the nitrogen-carbon support comprises pyrolyzing the carbon-based support on which the nitrogen precursor is adsorbed at a temperature of 500 ° C to 600 ° C, doping nitrogen atoms into the structure of the carbon-based support, Wherein the carbon atoms in the support form a new bond while simultaneously forming a reaction site capable of interacting with the palladium nanoparticles.
The method according to claim 1,
The step of preparing the supported catalyst comprises reacting a palladium precursor aqueous solution with a nitrogen-carbon support, and then reducing the palladium nanoparticles supported on the nitrogen-carbon support.
The method according to claim 1,
Wherein the nitrogen-carbon support has a hollow structure.
The method according to claim 1,
Wherein the palladium nanoparticles have an average particle diameter of 2 nm to 7 nm.
A nitrogen-carbon support doped with nitrogen (N) atoms and forming a new bond with the doped nitrogen atoms and carbon atoms in the carbon-based support; And palladium (Pd) nanoparticles carried on the nitrogen-carbon support.
9. The method of claim 8,
Wherein the formic acid dehydrogenation catalyst is a formate dehydrogenation catalyst having a doped nitrogen atom content of 3 wt% to 9 wt%.
9. The method of claim 8,
Wherein the formic acid dehydrogenation catalyst is a formate dehydrogenation catalyst wherein the content of supported palladium nanoparticles is 1 wt% to 9 wt%.
9. The method of claim 8,
The nitrogen-carbon support has a hollow structure.
9. The method of claim 8,
Wherein the palladium nanoparticles have an average particle diameter of 2 nm to 7 nm.
A fuel cell comprising the formic acid dehydrogenation catalyst according to any one of claims 8 to 12.
A hydrogen generator comprising the formic acid dehydrogenation catalyst of any one of claims 8 to 12.

Images