KR101802644B1 - The method of manufacturing synthesis gas and electrochemical conversion of carbon dioxide with gold nanoclusters and gold nano-based alloy clusters - Google Patents

Abstract

The present invention discloses electrochemical conversion of carbon dioxide using gold nanoclusters and gold nano-based alloy clusters and a method for producing synthesis gas. A method for producing syngas according to an embodiment of the present invention is to produce a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide using a catalyst comprising Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical conversion of carbon dioxide using gold nano clusters and gold nano-based alloy clusters, and a method of manufacturing synthetic gas using gold nano clusters and gold nano-

The present invention relates to electrochemical conversion of carbon dioxide using gold nanoclusters and gold nano-based alloy clusters, and more particularly, to gold nanoclusters of Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ The present invention relates to a method for producing a synthesis gas containing carbon monoxide and hydrogen by electrochemical conversion of carbon dioxide on an aqueous solution using a catalyst comprising a gold nano-based alloy cluster of C ₆ S ₁₈ .

A syngas, or syngas, is a gaseous mixture containing carbon monoxide (CO) and hydrogen (H ₂ ), which may also contain carbon dioxide (CO ₂ ). For example, syngas is generated by gasification into a gaseous product having a specific calorific value of the carbon-containing fuel.

Synthetic gas has an energy density of about 50% of natural gas. The syngas can be burned and accordingly used as a fuel source. Syngas can also be used as an intermediate product in the generation of other chemical products. For example, the syngas can be generated by gasification of coal or waste.

In the generation of synthesis gas, carbon can be reacted with water or hydrocarbons can be reacted with oxygen. There are commercially available techniques for treating syngas to generate industrial gases, fertilizers, chemicals, and other chemical products. However, most known techniques for the generation and conversion of syngas (e.g., water-shift reactions) require a large amount of hydrogen to be released into the atmosphere as a gas harmful to the climate, Resulting in the generation of excess carbon dioxide.

In the partial oxidation of methane with another known technique for the synthesis of syngas, 2CH ₄ + O ₂ 2CO + 4H ₂ , the maximum ratio of CO: H ₂ can reach 2: 1. However, its drawback is that it uses pure oxygen produced in an energy intensive manner. Further, it is known that the reforming reaction of methane using carbon dioxide, which is another known technology, can produce a synthesis gas (CO: H ₂ = 1: 1) having a high carbon monoxide content.

On the other hand, that the carbon dioxide (CO ₂₎ the main causes of global warming is converted to more useful substances, as well as capture and storage of the material used as a raw material of renewable energy is important in the long term abatement of carbon dioxide.

The synthesis of syngas using carbon dioxide and carbon monoxide in an aqueous solution can be utilized not only in the synthesis gas production facility using methane and coal but also in the case of introducing environmentally friendly energy such as solar energy and wind energy, It can have a ripple effect.

Many researchers have attempted to convert carbon dioxide to other useful materials using a variety of modified metal catalysts. There have been attempts to convert carbon dioxide by using noble metals such as gold (Au) or silver (Ag). When gold nano clusters (Au ₂₅ ) composed of 25 gold atoms are used up to now, Has a Faraday efficiency of 90% or more.

PtAu _{24, which} is synthesized by doping platinum (Pt) into gold nanoclusters composed of ₂₅ gold atoms (Au ₂₅ ), has a structure in which a platinum atom is positioned at the center thereof and its energy structure is different from that of Au ₂₅ The function as a chemical catalyst can be finely controlled. Based on the stable structure of Au ₂₅ , PtAu ₂₄ is expected to show different catalyst selectivity than Au ₂₅ as well as being stable as a catalyst by doping the platinum in the center.

An embodiment of the present invention is to provide a method for producing a synthesis gas containing carbon monoxide and hydrogen through electrochemical conversion of carbon dioxide on an aqueous solution using a catalyst including gold nano clusters and gold nano-based alloy clusters.

A method of producing a syngas according to an embodiment of the present invention uses a catalyst comprising Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ to produce synthesis gas containing carbon monoxide and hydrogen from carbon dioxide .

In the method of producing a synthesis gas according to an embodiment of the present invention, a reaction formula for producing a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide is as follows,

[Reaction Scheme]

CO ₂ + H ₂ O (aq) CO + H ₂ + O ₂

The Au ₂₅ (C ₆ S) ₁₈ promotes the reaction to produce carbon monoxide, and the PtAu ₂₄ (C ₆ S) ₁₈ can promote the reaction to generate hydrogen.

A method of manufacturing a synthesis gas according to an embodiment of the present invention, the Au ₂₅ (C ₆ S) ₁₈ and the carbon monoxide and hydrogen in the PtAu ₂₄ (C ₆ S) synthesis gas produced by the ratio control of the ₁₈ The generation ratio can be adjusted.

In the method of producing a synthesis gas according to an embodiment of the present invention, the production ratio of carbon monoxide and hydrogen in the synthesis gas may be 1: 1.2 to 1: 4.

In the method for producing the synthesis gas according to an embodiment of the present invention, the method for producing the synthesis gas containing carbon monoxide and hydrogen from the carbon dioxide may be carried out in an aqueous solution.

The catalyst according to one embodiment of the present invention is a catalyst comprising Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ used for producing a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide , Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ is 1: 0.5 to 2.

The electrode according to an embodiment of the present invention includes Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ in an electrode used for producing a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide , Carbon black, and naphion.

In an electrode according to an embodiment of the present invention, the weight ratio of the catalyst and the carbon black may be 1: 1.

A method of producing a synthesis gas according to another embodiment of the present invention produces a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide using a PtAu ₂₄ (C ₆ S) ₁₈ catalyst.

According to an embodiment of the present invention, a synthesis gas containing carbon monoxide and hydrogen can be easily produced through electrochemical conversion of carbon dioxide on an aqueous solution using a catalyst including gold nano clusters and gold nano-based alloy clusters.

Also, according to an embodiment of the present invention, the composition ratio of the gold nano clusters and the gold nano-based alloy clusters can be adjusted to selectively and selectively control the carbon monoxide and hydrogen production ratios in the syngas.

In addition, according to an embodiment of the present invention, the synthesis gas produced by variously controlling the production ratio of carbon monoxide and hydrogen in the synthesis gas can be variously applied to the production of acetic acid, ethylene, methanol, methane gas and the like.

Figure 1 shows the geometrical structure of (a) the Au ₂₅ (C ₆ S) ₁₈ gold nanoclusters and (b) the geometry of the PtAu ₂₄ (C ₆ S) ₁₈ gold nano-based alloy clusters.
FIG. 2 is a graph showing the results of (a) Au ₂₅ (C ₆ S) ₁₈ gold nanoclusters and (b) PtAu ₂₄ (C ₆ S) ₁₈ A mass analysis graph of a gold nano-based alloy cluster is shown.
FIG. 3 is a graph showing the results of (a) Au ₂₅ (C ₆ S) ₁₈ gold nanoclusters and (b) PtAu ₂₄ (C ₆ S) ₁₈ (UV-Vis-NIR) absorption spectrum on a trichlorethylene solution of a gold nano-based alloy cluster.
FIG. 4 is a graph showing the relationship between (a) Au ₂₅ (C ₆ S) ₁₈ gold nano clusters and (b) PtAu ₂₄ (C ₆ S) ₁₈ nanoparticles through a square-wave Boltammogram (SWV) And graphs showing oxidation and reduction peaks of gold nano-based alloy clusters.
Fig. 5 shows the configuration of an H-shaped cell (reactor) used for the electrochemical conversion reaction of carbon dioxide.
Figure 6 Au ₂₅ (C ₆ S) ₁₈ and ₂₄ PtAu (C S ₆₎ a carbon black and a Nafion composite electrode based on the catalyst containing _{18 (Au 25 (C 6 S} ) 18 -PtAu 24 (C 6 S) ₁₈ / carbon black / Nafion complex electrode). The graph of FIG.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may unnecessarily obscure the subject matter of the present invention. In addition, the terms described below are terms set in consideration of the functions of the present invention, and these may vary depending on the intention of the manufacturer or custom in the industry, and the definition should be based on the contents throughout the specification.

Hereinafter, the present invention will be described in detail.

The present invention relates to a method for manufacturing an electro-chemical conversion and synthesis gas of carbon dioxide using a catalyst comprising gold nanoclusters and alloy clusters of gold nano-based, and more particularly Au ₂₅ (C ₆ S) ₁₈ of gold nanoclusters and PtAu ₂₄ (C ₆ S) ₁₈ The present invention relates to a method for producing a synthesis gas containing carbon monoxide and hydrogen by electrochemical conversion of carbon dioxide on an aqueous solution using a catalyst comprising a gold nano-based alloy cluster.

Method of manufacturing a synthesis gas according to an embodiment of the present invention, Au ₂₅ (C ₆ S) ₁₈ Gold nano-cluster (hereinafter, Au ₂₅ (C ₆ referred to as S) ₁₈₎ and PtAu ₂₄ (C ₆ S) ₁₈ Gold use of a catalyst including a nano-based alloy cluster (hereinafter, PtAu ₂₄ (referred to as C ₆ S) _18), and the Au ₂₅ (C ₆ S) ₁₈ and the PtAu ₂₄ (C ₆ S) ₁₈ controlling the composition ratio of , It is possible to selectively and easily control the generation ratio of carbon monoxide and hydrogen in the synthesis gas containing carbon monoxide and hydrogen.

More specifically, in a method for producing a synthesis gas according to an embodiment of the present invention, a reaction formula for producing a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide is as follows,

[Reaction Scheme]

CO ₂ + H ₂ O (aq) CO + H ₂ + O ₂

The Au ₂₅ (C ₆ S) ₁₈ has a high selectivity for electrochemical conversion to carbon monoxide, which promotes carbon monoxide generation reaction. The PtAu ₂₄ (C ₆ S) ₁₈ has high electrical selectivity to hydrogen It is possible to control the production ratio of carbon monoxide and hydrogen in the synthesis gas produced through controlling the composition ratio of Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ .

In this case, the production ratio of carbon monoxide and hydrogen in the synthesis gas may be 1: 1.2 to 1: 4.

Meanwhile, a method for producing a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide according to an embodiment of the present invention may be performed in an aqueous solution. In the reaction of carbon dioxide using only water and carbon dioxide, the hydrogen cation (H ⁺ ) generated from the cathode, especially from water, can be used to convert carbon dioxide to carbon monoxide. This allows pure hydrogen and carbon monoxide to be obtained without any other chemical emissions.

In addition, the catalyst according to an embodiment of the present invention is a catalyst comprising Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ used for producing a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide , The composition ratio of the Au ₂₅ (C ₆ S) ₁₈ and the PtAu ₂₄ (C ₆ S) ₁₈ may be 1: 0.5 to 2.

In order to utilize the catalyst according to an embodiment of the present invention for producing a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide, an electrode including the catalyst may be prepared and used.

Specifically, the electrode according to an embodiment of the present invention includes Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) in an electrode used for producing a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide, ₁₈ , < / RTI > carbon black, and Nafion.

In an electrode according to one embodiment of the present invention, Nafion is used for firm fixation between the catalyst and the carbon black.

In an electrode according to an embodiment of the present invention, the weight ratio of the catalyst and the carbon black may be 1: 1. Here, the weight ratio may mean a mass ratio. When the weight ratio of the catalyst and the carbon black is 1: 1, the hydrogen gas generating catalyst can cover the surface of the carbon black with a single layer, so that the cost can be reduced using the minimum catalyst and the maximum catalyst efficiency is exhibited .

Further, the synthesis gas process for producing a synthesis gas according to another embodiment of the present invention comprises carbon monoxide and hydrogen from the carbon dioxide by using the _{PtAu 24 (C 6 S) PtAu} 24 consisting of ₁₈ only (C ₆ S) ₁₈ catalyst .

Hereinafter, the present invention will be described in more detail with reference to the drawings and examples. However, the following drawings and examples are provided for illustrative purposes only and should not be construed as limiting the scope of the present invention.

Hereinafter, gold nanoclusters and gold nano-based alloy clusters according to an embodiment of the present invention will be described in detail with reference to FIG. 1 to FIG.

Figure 1 shows the geometrical structure of (a) the Au ₂₅ (C ₆ S) ₁₈ gold nanoclusters and (b) the geometry of the PtAu ₂₄ (C ₆ S) ₁₈ gold nano-based alloy clusters.

1, Au ₂₅ (C ₆ S) ₁₈ gold nanoclusters in (a) were prepared by mixing ₂₅ gold (Au) atoms (orange) with C ₆ S (1-hexanethiol) ligand and found to be protected by the structure, (b) the PtAu ₂₄ (C ₆ S) ₁₈ alloy clusters of gold nano-based gold atoms one platinum in the center in the gold atom (orange) Au ₂₅ consisting of 25 dogs (Pt ) (Blue) is a structure in which PtAu ₂₄ is protected by a C ₆ S ligand (orange).

FIGS. 2 to 4 illustrate (a) Au ₂₅ (C ₆ S) ₁₈ gold nanoclusters and (b) PtAu ₂₄ (C ₆ S) ₁₈ It is a characteristic of the gold nano-based alloy cluster. 2 to in Fig. 4, (a) is Au ₂₅ (C ₆ S) ₁₈ denotes a gold nanoclusters, (b) is PtAu ₂₄ (C ₆ S) ₁₈ Represents a gold nano-based alloy cluster.

2 is a schematic diagram of a gold nanoclust of (a) Au ₂₅ (C ₆ S) ₁₈ and (b) PtAu ₂₄ (C ₆ S) ₁₈ A mass analysis graph of a gold nano-based alloy cluster is shown. Matrix-Assisted Laser Desorption / Ionization (MALDI) was used for mass spectrometry of Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ .

Referring to FIG. 2, only one peak is observed for the two clusters, and the clusters produced are monodispersed, with Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ . Au ₂₅ with a peak of PtAu ₂₄ is observed at around 7032 Da are observed at about 7034 Da are, but can be difficult to distinguish by the overlapping portion corresponds to just because only the difference is 1.89 Da, respectively, simulated isotope patterns (each Black bars in the upper right graph).

FIG. 3 is a graph showing the results of (a) Au ₂₅ (C ₆ S) ₁₈ gold nanoclusters and (b) PtAu ₂₄ (C ₆ S) ₁₈ (UV-Vis-NIR) absorption spectrum on a trichlorethylene solution of a gold nano-based alloy cluster.

Absorption spectrum (Abs (λ)) of the wavelength (λ) standard was converted to the photon energy (E) spectrum (Abs (E)) of the scale, the relationship is as Abs (E) [Abs (λ )] λ 2 . In other words, the change of absorbance was indicated by the photon energy scale to observe the peak of the broad near infrared (NIR) region.

Referring to Figure 3, (a) 1.8, 2.8 and at 3.1 eV showed the absorption tendency of a characteristic Au ₂₅ the absorption band appearing, absorption bands observed multiple is Au ₂₅ are unique molecules have similar properties Is one of the main reasons, and the position of the absorption band means that Au ₂₅ is charged to -1 and is present as [Au ₂₅ ] ^- .

When platinum (Pt) atoms are introduced, the absorption tendency is completely different as in (b). A distinct absorption band at 2.1 eV is evident and a broad near-infrared band at the center of 1.1 eV is seen in the lower energy region. This result agrees with the absorption tendency of PtAu ₂₄ , which has been reported so that the introduced Pt atom is located at the center of the metal core of Au ₂₅ , maintains the molecular-like property, and has a neutral charge [PtAu _24] it can be seen that the presence of ^0.

This distinctly different absorption tendency implies that the specific electronic structure of [Au ₂₅ ] ^- has changed by the introduction of a platinum (Pt) atom at its center, from which the electronic structure of the catalyst is changed Can be achieved.

FIG. 4 is a graph showing the relationship between (a) Au ₂₅ (C ₆ S) ₁₈ gold nano clusters and (b) PtAu ₂₄ (C ₆ S) ₁₈ nanoparticles through a square-wave Boltammogram (SWV) And graphs showing oxidation and reduction peaks of gold nano-based alloy clusters.

Specifically, Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ are dissolved in a solution of tetrabutylammonium hexafluorophosphate (TBAPF 6) and dichloromethane (CH ₂ Cl ₂ ) After the rear argon purging, three electrodes were measured. In FIG. 2C, O1 to O3 represent the first to third oxidation peaks, respectively, and R1 to R2 represent the first to second reduction peaks, respectively.

Voltammetric measurements are a very powerful tool for revealing electronic structures near the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels in metal nanoclusters. For accurate comparison, the measured potential was corrected based on the reduction potential of ferrocene (Fc ^{+ / 0} ), an internal standard.

4, the current peak in the voltamogram is located at a potential at which the charge state of the cluster changes, and in the case of Au ₂₅ , [Au ₂₅ ] ^{+ / 0} , [Au ₂₅ ] ^{0 / -} and [Au ₂₅ ] Three well-separated peak pairs corresponding to ^{- / - 2} charge state couple are observed at -0.39, -0.04, and -2.06 V, respectively.

Since each current peak represents two oxidation reactions and one reduction reaction in turn, homo and ramo, the presence of a current peak indicates that it has a homo and ramo energy levels representing the molecular-like nature of Au ₂₅ do. Further, when a voltage is applied, an oxidation or reduction reaction of Au ₂₅ occurs depending on the difference between the applied voltage and the energy level, so that precise control such as manipulation of the charged state of the metal cluster is possible.

Referring again to FIG. 4, (a) a voltamogram of (a) PtAu ₂₄ different from that of Au ₂₅ can be observed under the same conditions, which can be observed at 0.40, -0.03, -0.78 and -1.10 V, respectively [PtAu ₂₄ ] ^{+ 2 / +} , [PtAu ₂₄ ] ^{+ / 0} , [PtAu ₂₄ ] ^{0 / -} and [PtAu ₂₄ ] ^{- / - 2} charge pairs.

The current peak of -1.10 V corresponding to the [PtAu ₂₄ ] ^{- / - 2} charge pair is shifted by 0.96 V in positive direction from the current peak at -2.06 V, which is the same charge pair of Au ₂₅ . This is attributed to the change in the electronic structure of the Au ₂₅ with the substitution of Pt, and the change is due to the triply degenerate homo-energy level of the Au ₂₅ split into doubly degenerate homo .

This phenomenon occurs when the current peak corresponding to [Au ₂₅ ] ^{- / - 2} disappears and the current peak corresponding to [PtAu ₂₄ ] ^{+ 2 / +} and [PtAu ₂₄ ] ^{+ / 0} at the positive potential centered on the vanished current peak Current peaks corresponding to [PtAu ₂₄ ] ^{0 / -} and [PtAu ₂₄ ] ^{- / - 2} at the negative potentials, respectively, represent new homo and loop moieties.

As a result, when a Pt atom is substituted for Au ₂₅ to become PtAu ₂₄ , a large positive shift of the current peak corresponding to the -1/2 charge pair is observed, which represents a low radome energy level separated from the homo, -2 implies that the charge phase change to the charged state is much easier on the PtAu ₂₄ than on the Au ₂₅ . It can be seen that the electronic structure of the metal nanocluster can be controlled favorably for the catalytic reaction by changing the central metal atom.

Hereinafter, the Au ₂₅ (C ₆ S) ₁₈ gold nanoclusters and the PtAu ₂₄ (C ₆ S) ₁₈ nanoclusters according to one embodiment of the present invention will be described with reference to Examples 1-1 and 1-2. A method of synthesizing a gold nano-based alloy cluster will be described in more detail.

Example 1-1: Preparation of Au ₂₅ (C ₆ S) ₁₈ Synthesis of

A gold nano-cluster Au ₂₅ (C ₆ S) ₁₈ was prepared by using a known Brust synthesis method, in which 25 gold atoms were protected by C ₆ S (1-hexanethiol, 98%) ligand .

0.394 g (1.00 mmol) of tetrachloromonous acid hexahydrate (HAuCl ₄ .3H ₂ O, reagent grade) dissolved in 30 ml of tetrahydrofuran was stirred at a speed of 800 RPM or higher and 0.634 g (1.16 mmol) of tetraoctylammonium bromide (TOABr, Tetraoctylammonium bromide, 98%) was added.

After stirring for 30 minutes, 0.716 mL (5.04 mmol) of 1-hexanethiol was slowly added to the red colored solution. Stirring was continued for about 1 hour at which time the color of the solution gradually changed from red to yellow and from yellow to clear color to form a gold-hexane thiol polymer.

After the color of the solution became transparent, it was dissolved in purified water of 0.380 g (10.0 mmol) of NaBH ₄ (sodium borohydride, 99%) as a reducing agent, and the prepared solution was rapidly added to the stirring solution. The color of the solution immediately turned black. In this process, the gold-hexane thiol polymer is reduced by NaBH ₄ to form gold nanoclusters protected with 1-hexanethiol.

And further stirred for 5 hours. After the reaction, the organic layer was transferred to a circular tube from a solution divided into a tetrahydrofuran layer and a water layer, and a washing process was performed to remove impurities such as TOABr 10 times using water and methanol.

The precipitate remaining on the wall of the round tube was dissolved in dichloromethane and transferred to a 250 ml round bottom flask. The solvent was completely removed using a rotary evaporator, and 100 ml of a 1: 1 mixture of acetonitrile and acetone Was added and extracted for 12 hours.

Thereafter, the solution was purified using a filter having a pore size of 20 μm, and the purified solution was rotary evaporated again to separate the solid Au ₂₅ (C ₆ S) ₁₈ . The production amount is about 20 to 40 mg.

Example 1-2: Preparation of PtAu ₂₄ (C ₆ S) ₁₈ Synthesis of

The procedure was analogous to the synthesis of Au ₂₅ (C ₆ S) ₁₈ gold nanoclusters described in Example 1-1.

15 ㎖ THF with 0.157 g of HAuCl _{4 ·} 3H ₂ O in H ₂ PtCl ₆ dissolved in 0.041g of (platinum chloride salt, hydrate Chloroplatinic acid, reagent grade) was added and the TOABr of 0.317 g, and stirred at room temperature for 15 minutes Respectively. Then, 0.358 ml of 1-hexanethiol was added to form a ligand-metal complex.

Additional stirring was continued for 15 minutes, and 0.190 g of the reducing agent NaBH ₄ dissolved in 5 ml was added rapidly. The color of the solution immediately turned to dark brown, and further stirring was carried out for 5 hours. This process involves the reduction of ligand-metal complexes to grow from small to large particles through kinetic competition between the protective effect of the ligand over time and the growth effect of the core.

When the reaction was completed, the reaction mixture was washed repeatedly with water and methanol, and the organic layer was transferred by centrifugation and extracted with a 1: 1 volume ratio of acetonitrile and acetone for 12 hours.

The solid produced by the extraction was dissolved in 11 ml of dichloromethane solvent, 2 ml of hydrogen peroxide was added and the solution was oxidized for 2 hours. When hydrogen peroxide was added, the solution rapidly changed from greenish yellow to green. The Au ₂₅ (C ₆ S) ₁₈ produced by this process is oxidized and removed, leaving only PtAu ₂₄ (C ₆ S) ₁₈ .

Then, it was repeatedly washed with distilled water. Only the organic layer was transferred to a vial, and PtAu ₂₄ (C ₆ S) ₁₈ was isolated by extraction with acetonitrile and dichloromethane 2: 1 solution. It was made into a solid state by filtration and rotary evaporation and refrigerated.

In the following embodiment examples 2-1 to Example 2-3 Au ₂₅ according to one embodiment of the present invention with reference to the (C ₆ S) ₁₈ of gold nanoclusters and PtAu ₂₄ (C ₆ S) ₁₈ A catalyst including a gold nano-based alloy cluster, and an electrode including the catalyst will be described in more detail.

Example 2-1: Electrode Pretreatment by Electrode Cleaning and Electrochemical Method

[Cleaning of Electrode]

In order to clean the glassy carbon electrode, electrodes were immersed in distilled water solution and sonicated for 5 minutes. In addition, acetone, ethanol and acetone were added to each solution in the order, and sonication was performed for 5 minutes.

[Pretreatment of electrode by electrochemical method]

The glassy carbon plate electrode was applied with a voltage of +1.75 V for 300 seconds in a 0.1 M (pH = 5.5) phosphate buffer solution. After that, the voltage was applied from 0.3 V to 1.3 V by setting the scan speed to 0.1 V / s using the cyclic voltammetry method. The cyclic voltammetry method was repeated until the rectified state appeared, and then the voltage from 0.3 V to -1.3 V was applied by the cyclic voltammetry method.

The electrochemically treated glassy carbon electrode in the form of a plate is modified to hydrophilic properties in the hydrophobic electrode by forming -OH (hydroxyl group) on the surface.

Example 2-2: Preparation of Au ₂₅ (C ₆ S) ₁₈ -PtAu ₂₄ (C ₆ S) ₁₈ / Carbon black / Nafion composite electrode manufacturing

[Preparation of carbon black / Nafion solution]

First, 2.4 mg of carbon black (VULCAN® XC72) was dispersed by ultrasonication in 420 μl of dichloromethane for 2 hours or more. 42 ㎕ Nafion (Nafion, 5 wt%) was added to the dispersed solution, followed by ultrasonic dispersion for 10 minutes to prepare a carbon black / nafion solution.

[Preparation of Au ₂₅ (C ₆ S) ₁₈ -PtAu ₂₄ (C ₆ S) ₁₈ / carbon black / Nafion composite electrode]

Two nanoclusters of Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ were mixed. The two clusters were injected sequentially into the dichloromethane solution in which carbon black and Nafion solution were mixed in the desired ratio.

For example, when a mixture of Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ was mixed at a 2: 1 ratio, each cluster was dissolved in dichloromethane at the same concentration, Lt; RTI ID = 0.0 > Nafion < / RTI > solution. When the Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ were mixed at a ratio of 1: 2, the respective clusters were first dissolved in dichloromethane at the same concentration, To the carbon black / Nafion solution.

The prepared _{Au 25 (C 6 S) 18} -PtAu 24 (C 6 S) 18 / carbon black / Nafion solution of a complex within a Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ratio of ₁₈ to the Table 1.

Au ₂₅ (C ₆ S) ₁₈ : PtAu ₂₄ (C ₆ S) ₁₈ 2: 1 1: 2 0: 1

50 μl of a solution of Au ₂₅ (C ₆ S) ₁₈ -PtAu ₂₄ (C ₆ S) ₁₈ / carbon black / Nafion complex was added to a plate-like glassy carbon electrode having a 0.5 × 1.0 cm 2 area pretreated in Example 2-1 Drop-casting on the front and back sides, respectively, and dried for 2 hours or more. This condition is set so that the mass ratio of the carbon black drop-cast onto the electrode and the Au ₂₅ (C ₆ S) ₁₈ -PtAu ₂₄ (C ₆ S) ₁₈ catalyst is 1: 1.

Example 2-3: Assembling electrochemical conversion cell

5 shows a configuration of an H-type cell used for an electrochemical conversion reaction of carbon dioxide.

Referring to FIG. 5, the cell used for the electrochemical conversion was fabricated as an H-type glass reactor. At this time, the Nafion membrane was used in the middle between the anode and the cathode to facilitate the movement of hydrogen cations. The volume of electrolyte used for each anode and cathode is 60 mL each. Except for the area where the electrode passes, it was assembled so that the gas did not escape with a Teflon lid.

The electrochemical conversion of carbon dioxide using the Au ₂₅ (C ₆ S) ₁₈ -PtAu ₂₄ (C ₆ S) ₁₈ catalyst / carbon black / Nafion composite electrode according to one embodiment of the present invention and The analysis method will be described in detail.

Example  3: Au ₂₅ (C ₆ S) ₁₈ - PtAu ₂₄ (C ₆ S) ₁₈ / Carbon black / Nafion  Electrochemical Conversion and Analysis of Carbon Dioxide Using Composite Electrodes

Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) a carbon black and a Nafion composite electrode based on the catalyst containing _{18 (Au 25 (C 6 S} ) 18 -PtAu 24 (C 6 S) 18 / Carbon black / Nafion composite electrode) was used to electrochemically convert the carbon dioxide present in the aqueous solution. Here, the analysis of the reactants detected carbon monoxide and hydrogen through a mass analyzer and a thermal conductivity detector mounted on gas chromatography, respectively.

All nano cluster-based electrodes were supported on the anodic electrolyte solution of the H-type cell of FIG. 5, and the carbon dioxide was purged through the electrolyte solution for 1 hour. The electrode was a newly formed electrode for each of the applied voltages. The carbon dioxide on the aqueous phase reacted with the electrode, and the aqueous solution was stirred through a magnetic stirrer.

Here, the carbon dioxide is supplied from the electrode to the two electrons (2e ^- ), the two hydrogen cations (2H ⁺ ) are supplied in the aqueous solution and converted into carbon monoxide, and the generated carbon monoxide is converted into the H- . In addition, since a voltage is applied to an electrode in an aqueous solution, water-decomposition is simultaneously performed, and in this case, hydrogen (gas) is also generated by water-decomposition.

The reaction scheme of electrochemical conversion of carbon dioxide is as follows.

[Reaction Scheme]

CO ₂ + H ₂ O (aq) CO + H ₂ + O ₂

All of the gases have low solubility in the aqueous solution, so they move to the upper part of the reactor, and this gas is extracted twice through the gas-only syringe.

First, carbon monoxide was first detected by gas chromatography-mass spectrometry. The amount of carbon monoxide detected was quantified through the carbon monoxide calibration curve, which was also used to calculate the Faraday conversion efficiency. Similarly, for the second extracted hydrogen, the amount was quantified via gas chromatography-thermal conductivity detector, which was also used to calculate the Faraday conversion efficiency.

The amount of generated two gases was found to be 100% of the efficiency of Faraday conversion at all electrodes, which was consistent with the amount of electrons flowing to the electrode. This shows that no other products were generated in the electrochemical conversion of carbon dioxide using the metal nanoclusters of the present invention.

During the entire carbon dioxide conversion process, a constant RPM was maintained through a magnetic stirrer to facilitate the movement of gas in the solution and the gas generated on the electrode surface was easily released from the electrode.

Based on the electrochemical conversion and analysis of carbon dioxide using the Au ₂₅ (C ₆ S) ₁₈ -PtAu ₂₄ (C ₆ S) ₁₈ / carbon black / Nafion composite electrode described in Example 2-2, Experiments were conducted to control the production of carbon monoxide and hydrogen in the synthesis gas produced by varying the compositions of Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ .

To this end, a drop-cast glassy carbon electrode of Au ₂₅ (C ₆ S) ₁₈ -PtAu ₂₄ (C ₆ S) ₁₈ / carbon black / Nafion complex prepared in Example 2-2 was used as a working electrode, The electrochemical conversion of carbon dioxide proceeded. 0.1 M KHCO ₃ was used as the electrolyte and the voltage after electrolysis was -1.03 V based on RHE (real hydrogen electrode) (pH = 6.7).

Hereinafter, results of the third embodiment will be described with reference to FIG.

FIG. 6 is a graph showing a graph of carbon monoxide and hydrogen production ratio generated using Au ₂₅ (C ₆ S) ₁₈ -PtAu ₂₄ (C ₆ S) ₁₈ / carbon black / Nafion composite electrode.

The histogram in Figure 6 of Au ₂₅ (C ₆ S) _18, the gold nano-cluster with PtAu ₂₄ (C ₆ S), carbon monoxide (black) and hydrogen (red) generated in the electrode made of a mixture of ₁₈ Gold nano-based alloy nanoclusters of Respectively.

Here, the x-axis is a composition ratio of Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ contained in the catalyst, and the y-axis on the left side is a molar ratio (CO mol fraction (% The y-axis on the right side shows the molar ratio of hydrogen (H ₂ mol fraction (%)). The voltage applied at this time was -1.0 V (pH 6.7) based on RHE (real hydrogen electrode), and the total of three ratios (Au ₂₅ (C ₆ S) ₁₈ : PtAu ₂₄ (C ₆ S) ₁₈ = 2: 1, 1: 2, 0: 1).

Au ₂₅ (C ₆ S) ₁₈ : PtAu ₂₄ (C ₆ S) ₁₈ CO: H ₂ 2: 1 1: 2 1: 2 1: 3 0: 1 1: 4

The ratio of the mixture of carbon monoxide and hydrogen used in the synthesis gas is 1: 1 for the production of acetic acid, 1: 2 for the production of ethylene and methanol, 1: 3 for the production of methane gas .

In the process for producing a synthesis gas according to an embodiment of the present invention, in the case of catalyst electrodes prepared using Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ , acetic acid, ethylene, The ratio of carbon monoxide and hydrogen required for production can be efficiently controlled.

6 and Table 2, when the compositions of Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ are changed, the ratio of carbon monoxide and hydrogen can be adjusted from 1: 1.2 to 1: 3. When two nano clusters (Au ₂₅ (C ₆ S) ₁₈ : PtAu ₂₄ (C ₆ S) ₁₈ ) serving as catalysts were mixed at a ratio of 2: 1 and 1: 2, the ratio of carbon monoxide to hydrogen It is adjustable from 1: 1.2 to 1: 3.

Specifically, the ratio of hydrogen to carbon monoxide produced by the electrode becomes 1: 1 as the proportion of PtAu ₂₄ (C ₆ S) _{18, which} is four times larger than that of Au ₂₅ (C ₆ S) ₁₈ , 3, respectively. At this time, the density of the current flowing through the actual electrode is 25 to 30 mA / cm 2.

According to one embodiment of the present invention, a synthesis gas containing carbon monoxide and hydrogen can be produced from carbon dioxide using a catalyst comprising Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ .

As specifically discussed through, an embodiment _{3, Au 25 (C 6 S} ) 18 is to accelerate the reaction to produce the carbon monoxide is high electrochemical conversion selectivity to carbon _{monoxide, PtAu 24 (C 6 S)} 18 is hydrogen It can be confirmed that the selectivity to electrochemical conversion to hydrogen is high by promoting the reaction to be generated.

Therefore, a synthesis gas containing carbon monoxide and hydrogen having various production ratios can be prepared by variously controlling the composition ratios of Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ .

According to an embodiment of the present invention, the production ratio of carbon monoxide and hydrogen contained in the synthesis gas may be 1: 1.2 to 1: 4. For this purpose, the composition ratio of Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ contained in the catalyst for electrochemical conversion of carbon monoxide is 1: 0.5 to 2, that is, 2: 1 to 1: have.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. This is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

Claims (9)

Au ₂₅ (C ₆ S) _18, and PtAu ₂₄ (C ₆ S) ₁₈ ,
The reaction scheme for producing a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide is as follows,
[Reaction Scheme]
CO ₂ + H ₂ O (aq) → CO + H ₂ + O ₂
The Au ₂₅ (C ₆ S) ₁₈ promotes the reaction to produce carbon monoxide,
Wherein the PtAu ₂₄ (C ₆ S) ₁₈ promotes the reaction of producing hydrogen to produce a synthesis gas comprising carbon monoxide and hydrogen from carbon dioxide.
delete The method according to claim 1,
And adjusting the composition ratio of Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ to control the production ratio of carbon monoxide and hydrogen in the produced synthesis gas.
The method of claim 3,
Wherein the production ratio of carbon monoxide and hydrogen in the syngas is from 1: 1.2 to 1: 4.
The method according to claim 1,
Wherein the method for producing the synthesis gas containing carbon monoxide and hydrogen from the carbon dioxide is carried out in an aqueous solution.
In a catalyst comprising Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ used for producing a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide,
The reaction formula for producing a synthesis gas containing carbon monoxide and hydrogen from the above carbon dioxide is as follows,
[Reaction Scheme]
CO ₂ + H ₂ O (aq) → CO + H ₂ + O ₂
The Au ₂₅ (C ₆ S) ₁₈ promotes the reaction to produce carbon monoxide,
The PtAu ₂₄ (C ₆ S) ₁₈ promotes the reaction of generating hydrogen,
Wherein the composition ratio of the Au ₂₅ (C ₆ S) ₁₈ and the PtAu ₂₄ (C ₆ S) ₁₈ is 1: 0.5 to 2.
An electrode used for producing a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide,
A catalyst comprising Au ₂₅ (C ₆ S) ₁₈ and PtAu ₂₄ (C ₆ S) ₁₈ , carbon black, and Nafion.
8. The method of claim 7,
Wherein the weight ratio of the catalyst and the carbon black is 1: 1.
PtAu ₂₄ (C ₆ S) ₁₈ catalyst,
The reaction scheme for producing a synthesis gas containing carbon monoxide and hydrogen from carbon dioxide is as follows,
[Reaction Scheme]
CO ₂ + H ₂ O (aq) → CO + H ₂ + O ₂
Wherein the PtAu ₂₄ (C ₆ S) ₁₈ promotes the reaction of producing hydrogen to produce a synthesis gas comprising carbon monoxide and hydrogen from carbon dioxide.

Images