KR20190094651A - Catalyst for carbon dioxide conversion and method for manufacturing thereof - Google Patents

Abstract

The present invention relates to an electrochemical cell used to decompose carbon dioxide to a useful conversion and to a catalyst used for the electrode for the cathode in the cell.
According to the present invention, a carrier having an electrical conductivity; A main catalyst which is a compound in which carbon dioxide is converted to a hydrocarbon and contains +1 valent Cu ions; By providing a catalyst characterized in that it comprises a secondary catalyst for supplying oxygen or oxygen ions to the main catalyst, by converting carbon dioxide to produce a hydrocarbon compound of C2 or more selectively and stably, thereby providing a catalyst with durability Can provide.

Description

Catalyst for carbon dioxide conversion and its manufacturing method {CATALYST FOR CARBON DIOXIDE CONVERSION AND METHOD FOR MANUFACTURING THEREOF}

TECHNICAL FIELD The present invention relates to catalysts, and in particular, to electrochemical cells used to decompose carbon dioxide and convert them into useful products, and to catalysts used for the electrodes for cathodes in the cells.

As the industry develops, energy use is greatly increased, and accordingly, the use of hydrocarbons including fossil fuels is also rapidly increasing. All hydrocarbons are basically in a certain proportion of carbon and hydrogen, which inevitably generates carbon dioxide when they are burned.

However, since carbon dioxide is known as a major factor of global warming, the reduction of carbon dioxide has emerged as a very important issue worldwide.

On the other hand, there are many industrial plants, chemical plants, steel mills, and cement plants, which emit a lot of carbon dioxide.

Recently, as a method of removing the generated carbon dioxide, the conversion technology that converts energy into carbon dioxide and useful resources such as oxygen has attracted great attention. Such a conversion technique may use a method of applying pressure at a high temperature or using a catalyst.

Among these conversion techniques, the method of using a catalyst has many advantages that the apparatus and the method itself are very simple, can use electricity produced from renewable energy as it is, and it is very easy to scale up to a commercial scale. . In addition, the method using a catalyst has the advantage that it can selectively produce various kinds of carbon compounds.

On the other hand, in order for the method using the catalyst to be put into practical use, it is necessary to be able to stably and continuously produce useful hydrocarbons of C2 or more such as ethylene, ethanol, propanol and butanol having excellent practicality.

Recently, some catalysts such as Cu and Cu ₂ O have been reported to have an effect on the generation of hydrocarbons of C2 or more have attracted attention.

However, in the case of Cu catalyst, it is known that there is a problem that CH ₄ has a higher generation rate than C ₂ H ₄ in the product generated by the reduction reaction of carbon dioxide.

On the other hand, in the case of the Cu ₂ O catalyst, the production rate of C ₂ H ₄ is higher than that of CH ₄ , but as the catalytic reaction proceeds, reduction of Cu atoms from + monovalent Cu ions occurs, thereby resulting in continuous conversion efficiency to C ₂ H ₄ . There is a problem that is reduced to.

As a result, in order to selectively and stably convert carbon dioxide to C2 or more hydrocarbons using a catalyst, it is necessary to increase the conversion rate of Cu catalyst to C2 or more hydrocarbons.

Therefore, the present invention intends to invent a Cu catalyst having a high conversion rate from carbon dioxide to C2 or more hydrocarbons.

The present invention provides a novel catalyst comprising a surface structure having a crystallographic preferential orientation for the production of C2 or more hydrocarbons in a catalyst for a cathode in which reduction occurs in an electrochemical cell used for the decomposition of carbon dioxide. For the purpose of

It is also an object of the present invention to provide new catalysts which are advantageous for the production of hydrocarbons above C2 by having different interface or grain boundary properties at the surface of the catalyst.

On the other hand, the present invention provides a method for producing a catalyst that is easy to scale up on an economical and commercial scale using equipment or processes commonly used in the existing metal field without expensive equipment or processes. I would like to.

In order to solve the above technical problem, according to an aspect of the present invention, the first catalyst layer comprising a Cu polycrystalline base having a {100} plane in the first direction; A second catalyst layer is disposed on the first catalyst layer and includes a polycrystalline layer made of Cu. The complex catalyst may be provided.

Preferably, the fraction of the {100} plane in the Cu polycrystalline base is 30% or more; a composite catalyst may be provided.

Preferably, the polycrystalline layer in the second catalyst layer may be provided with a composite catalyst, characterized in that the orientation is not formed first.

Alternatively, the polycrystal layer in the second catalyst layer may have a preferred orientation of {111} or {110} planes.

Preferably, a complex catalyst may be provided between the first catalyst layer and the second catalyst layer having a surface structure in which a height difference or a step is formed.

Preferably, the second catalyst layer is a 0-dimensional structure such as a dot or a 1-dimensional structure of a wire, a needle, and a thin column, or a 2-dimensional structure of a thin film or an island; A complex catalyst characterized in that may be provided.

Preferably, the complex catalyst may be provided with a complex catalyst, characterized in that containing at least one element of oxygen, nitrogen, or hydrogen in the catalyst.

Preferably, the complex catalyst may be provided with a complex catalyst comprising at least one of Cu oxide, Cu nitride, Cu oxynitride or Cu hydroxide in the catalyst.

Preferably, the first catalyst layer and the second catalyst layer may each include a different element; a complex catalyst may be provided.

According to another aspect of the invention, the step of preparing a Cu raw material constituting the first catalyst layer; A primary processing step of deforming the Cu raw material; Forming a second catalyst layer on the Cu raw material; Annealing step; may be provided a method for producing a composite catalyst comprising a.

According to another aspect of the invention, preparing a Cu raw material constituting the first catalyst layer; A primary processing step of dynamically recrystallizing the Cu raw material; The secondary processing step of forming a second catalyst layer on the Cu raw material; may be provided a method for producing a composite catalyst comprising a.

Preferably, the primary processing step is a multi-pass (multi-pass) rolling; it can be provided a method for producing a composite catalyst characterized in that.

Preferably, the secondary processing step may include a process of one or more of deposition, plating, or printing; may be provided a method for producing a complex catalyst characterized in that.

According to the catalyst comprising the surface structure having preferential orientation of the present invention, hydrocarbons useful for decomposing carbon dioxide, specifically C2 or more hydrocarbon compounds, can be selectively produced in a higher proportion than other hydrocarbons.

Through this, it is possible to obtain a catalyst that is advantageous for the production of C2 or more hydrocarbons compared to other catalysts.

In addition, since the catalyst of the present invention includes many different interfaces or grain boundaries on the surface, C2 hydrocarbon-forming dimerization at the interface or grain boundaries is more enhanced in terms of reaction rate or thermodynamic energy.

In addition, through the production method of the catalyst of the present invention, it is possible to prepare a catalyst having excellent carbon dioxide conversion efficiency by applying equipment and processes that are readily commercially available in the conventional metal field.

Through this method of producing a catalyst of the present invention has the advantage of excellent economy and easy scale-up.

On the other hand, another method for producing a catalyst of the present invention can produce a catalyst excellent in hydrocarbon conversion efficiency of C2 or more without a separate subsequent heat treatment.

Therefore, the catalyst manufacturing method of the present invention can omit a unit process that consumes a long time and energy, such as heat treatment, and has an effect of very excellent productivity and economy.

1 is a schematic diagram of an electrochemical cell for decomposing and reducing carbon dioxide.
Figure 2 shows the ratio of the type of hydrocarbon produced when carbon dioxide is decomposed on the surface of Cu and Cu ions.
FIG. 3 shows the free energy state at the interface according to the crystallographic orientation of the surface of Cu when generating a hydrocarbon having 2 or more carbon atoms (C2) using a Cu catalyst.
4 is a microstructure photograph showing the crystallographic orientation of a conventional Cu catalyst.
FIG. 5 shows the energy levels in the transition and final levels required for the formation of hydrocarbons above C2 on various surfaces.
6 is a flow chart showing one method of preparing the composite catalyst of the present invention.
FIG. 7 is a diagram schematically illustrating the manufacturing method in FIG. 6.
8 shows Young's modulus according to the crystallographic orientation of Cu.
9 is a flow chart showing another method of preparing the composite catalyst of the present invention.
FIG. 10 shows the microstructure of the copper plate according to the number of rolling passes when performing the primary processing step with cold rolling.
FIG. 11 shows experimental results of analyzing a reaction gas converted in an electrochemical cell for decomposing carbon dioxide, which is prepared using a composite catalyst having different {100} preferred orientations and having a first catalyst layer and a second catalyst layer, respectively.

Hereinafter, a catalyst and a method of preparing the same according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, only this embodiment to make the disclosure of the present invention complete and to those skilled in the art to fully understand the scope of the invention It is provided to inform you.

In order to clearly describe the present invention, parts irrelevant to the description are omitted, and like reference numerals designate like elements throughout the specification. In addition, some embodiments of the invention will be described in detail with reference to exemplary drawings. In adding reference numerals to components of each drawing, the same components may have the same reference numerals as much as possible even though they are shown in different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description may be omitted.

In describing the components of the present invention, terms such as first, second, A, B, (a), and (b) can be used. These terms are only to distinguish the components from other components, and the terms are not limited in nature, order, order or number of the components. If a component is described as being "connected", "coupled" or "connected" to another component, that component may be directly connected to or connected to that other component, but between components It is to be understood that the elements may be "interposed" or each component may be "connected", "coupled" or "connected" through other components.

In addition, in the implementation of the present invention may be described by subdividing the components for convenience of description, these components may be implemented in one device or module, or one component is a plurality of devices or modules It can also be implemented separately.

1 is a schematic diagram of a typical electrochemical cell for decomposing and reducing carbon dioxide.

As shown in FIG. 1, the electrochemical cell includes a cathode for receiving an oxidation reaction in which oxygen is generated, a cathode for reducing carbon dioxide, a compartment for accommodating an electrolyte containing the anode and the cathode, and Included are membranes positioned between the cathodes and selectively passing only the desired components on the electrolyte.

On the other hand, although not shown in Figure 1, the cell includes an energy supply source for supplying energy from the outside to drive the cell. The apparatus further includes an extractor for extracting a by-product generated from the reduction of the carbon dioxide. In addition, an electrolyte supply device can be added as needed.

Apart from this, if the by-product resulting from the reduction of carbon dioxide requires another additional reaction, it may optionally also comprise a secondary reactor for the reaction.

When the carbon dioxide is decomposed and reduced in the cell as shown in FIG. 1, carbon dioxide, hydrogen ions, and electrons react with each other in the cathode (cathode) to generate a hydrocarbon compound.

It is known that various by-products (or conversions or products) are produced depending on the type of catalyst in which the reduction reaction takes place.

CO₂ + nH⁺ + ne^-   C_xH_yO_z (One)

For example, when Ag or Sb is used as a catalyst, in this case, carbon dioxide reduced in the catalyst generates carbon monoxide through the following reaction formula (2). On the other hand, when Cu or Cu ₂ O is used as a catalyst, carbon dioxide is known to generate resources such as methane, ethane and ethylene through the following reaction formulas (3) to (6).

_{^{CO 2 + 2H + + 2e -}} → CO + H 2 O -0.51 V (2)

_{^{CO 2 + 8H + + 8e -}} → CH 4 + 2H 2 O -0.24 V (3)

_{^{2CO 2 + 12H + + 12e -}} → C 2 H 4 + 4H 2 O -0.33 V (4)

_{^{2CO 2 + 12H + + 12e -}} → C 2 H 5 OH + 3H 2 O -0.32 V (5)

_{^{3CO 2 + 18H + + 18e -}} → C 3 H 7 OH + 5H 2 O -0.31 V (V vs.NHE) (6)

On the other hand, in the oxidation electrode, water is oxidized through the following equation (7) to generate oxygen, hydrogen ions, and electrons.

_{n / 2 H 2 O → nH} + + n / 4O 2 + ne - (7)

Figure 2 shows the ratio of the type of hydrocarbon produced when carbon dioxide is decomposed on the catalyst surface of Cu and Cu ions.

As shown in FIG. 2, when metal Cu is used as a catalyst, CH ₄ and C ₂ H ₄ are mainly generated by reduction of carbon dioxide on the surface of Cu. In this case, although the production rates of CH ₄ and C ₂ H ₄ are similar to each other, it can be seen that CH ₄ occupies a larger fraction than C ₂ H ₄ .

In contrast, if +1 Cu is used as the catalyst, the reduction of carbon dioxide on the surface of +1 Cu ion produces mainly CH ₄ and C ₂ H ₄ , but the proportion of hydrocarbons produced is C _2. It can be seen that H ₄ occupies a much larger fraction up to 15 times higher than CH ₄ . This means that the use of Cu in the +1 ionic state as a catalyst of the electrochemical cell for carbon dioxide reduction has a very advantageous effect on the generation of hydrocarbons above C2.

FIG. 3 shows the free energy state at the interface according to the crystallographic orientation of the surface of Cu when generating C2 or more hydrocarbons using a Cu catalyst.

As shown in FIG. 3, the Cu catalyst, although chemically identical, was found to maintain a lower energy state for all C2 hydrocarbon productions investigated in the {100} plane than in the {111} plane.

For example, to generate a hydrocarbon called "+ OCCHO", it can be seen from FIG. 3 that the free energy of the entire system after the "+ OCCHO" generation reaction increases in the {111} aspect than the state where two carbon monoxides are combined. The results of FIG. 3 indicate that if the "+ OCCHO" hydrocarbons are to be produced from carbon monoxide, energy must be applied externally to compensate for the thermodynamically high energy of the final "+ OCCHO" hydrocarbons, in addition to the production or conversion reaction This means that energy must be supplied from outside to overcome the activation step.

On the contrary, in the case of {100}, the state where two carbon monoxides are bonded and the free energy state of the hydrocarbon "+ OCCHO" are almost identical. In addition, the activation energy of the {100} plane was lower than the activation energy of the {111} plane.

This result means that the {100} plane can form thermodynamically stable "+ OCCHO" hydrocarbons with less energy than the {111} plane. In addition, the activation energy for causing the production or conversion reaction also means that less {100} plane is needed.

4 is a microstructure photograph showing the crystallographic orientation of a conventional Cu catalyst.

In general, metals such as Cu are produced via conventional metallurgical processes. Specifically, it is manufactured by melting and casting, hot working and / or cold working, heat treatment and, if necessary, etching or surface treatment.

Face centered cubic (FCC), such as Cu, is generally the most stable surface because the {111} plane has the lowest energy in terms of surface energy. Meanwhile, in the case of a metal having a cubic lattice such as Cu, the <100> direction is the softest direction elastically.

However, in the general metal fabrication process, due to the thermodynamics or the fine turbulence generated during the melting and casting process, as-cast microstructures consist of only one crystal grain. It has a poly-crystal microstructure consisting of crystal grains which cannot be formed and have different crystallographic orientations.

Thereafter, hot and / or cold working and subsequent heat treatment cause all the cast microstructures to be broken down to form a processed microstructure consisting of fine polycrystals.

At this time, the orientations of the respective grains are generally known to be distributed randomly as shown in FIG. The results of Cu polycrystal orientation analysis in FIG. 4 are consistent with the azimuth distribution obtained through hot and / or cold working and subsequent heat treatment in common metallic materials. 4 shows that the distribution of {111} planes or {100} planes with small surface energy or elastic energy is rather small and the distribution of {101} planes is high.

However, the crystal orientation of the conventional Cu catalyst of FIG. 4 is in good agreement with the results of FIGS. 2 and 3.

Specifically, the results of the crystal orientation analysis of the conventional Cu catalyst of FIG. 4 indicate that the ratio of the {100} plane is very small at 2.1%. The results of FIG. 4 mean that, as shown in FIG. 3, there is no {100} plane on the surface of the conventional Cu catalyst, which is advantageous for C2 hydrocarbon production, and this expectation is again shown in FIG. 2. The relatively small C ₂ H ₄ conversion ratio agrees well.

On the other hand, Figure 5 shows the energy level in the transition stage and the energy level in the final stage, necessary for the formation of C2 or more hydrocarbons on a variety of surfaces with an external potential of -0.9V based on the standard hydrogen reduction potential .

First, in the case of the Cu metal catalyst having the {111} plane, for the C2 hydrocarbon-forming dimerization called OCCO by combining CO (carbon monoxide) and CO, the adsorbed CO molecules are tilted and then two CO After a transition stage leading the molecules closer together, a surface species called OCCO is created. Compared to the initial two CO molecular stages, there is a difference of free energy of 1.1 eV in the transition stage and 0.86 eV in the final stage. The physical meaning of this free energy difference is that in the case of the Cu metal catalyst having the {111} plane, for dimerization by combining CO (carbon monoxide) and CO, an energy of 1.1 eV or more must be supplied from the outside. It means there is an energy barrier that can arise.

On the other hand, in the case of the composite catalyst in which the metal oxide of Cu ₂ O and the Cu metal having the {111} plane coexist, the C 2 hydrocarbon-forming dimerization reaction in which the CO atom in the Cu atom and the CO atom in the + 1-valent Cu ion is OCCO This results in a difference of free energy of 0.71 eV in the transition stage and 0.12 eV in the final stage. This means that in a catalyst in which a metal oxide of Cu ₂ O and a Cu metal catalyst having a {111} plane coexist, the reaction may occur only when an energy of 0.71 eV or more is supplied from the outside.

The reason why CC coupling occurs more energetically in the complex catalyst of the Cu ₂ O metal oxide and the Cu metal is that C in the CO adsorbed on the + monovalent Cu ions is positively charged, while Cu atoms This is because C in CO adsorbed at is negatively charged. Thus, due to the electrostatic attraction for the formation of CC bonds between the two Cs, CC coupling occurs more energetically in the complex catalyst of Cu ₂ O metal oxide and Cu metal. This means that for the C2 dimerization reaction, the electrostatic attraction increases kinetics or thermodynamic driving forces.

In general, however, the surface of the metal is unstable because the bonds of the metal atoms are broken, and thus the metal atoms cannot exist alone. Because of this, even if no surface treatment is performed, pure metal naturally forms an oxide film on the surface. In addition, the general characteristics of the metal are applied to the Cu metal catalyst as it is, and Cu is present on the Cu metal surface as an oxide such as CuOx instead of the metal state.

Accordingly, the present inventors have completed a Cu metal catalyst having a new structure in which the crystallographic orientation of the conventional Cu metal catalyst is controlled and controlled in order to convert carbon dioxide to form C 2 or more hydrocarbons with high efficiency.

To this end, the catalyst in the present invention includes a first catalyst layer including a Cu polycrystalline base having a {100} plane in an orientation and a second catalyst layer positioned on the first catalyst layer and including a polycrystalline layer made of Cu. It is a composite catalyst characterized by the above-mentioned.

At this time, it is preferable that the fraction of the {100} plane in the said Cu polycrystal base is 30% or more. If the fraction of the {100} plane is less than 30%, it is difficult to expect a crystal orientation effect on the formation of C2 hydrocarbons.

On the other hand, the second catalyst layer is a polycrystalline catalyst in which {111}, {110}, and {100} are mixed. At this time, unlike the first catalyst layer, the polycrystalline layer in the second catalyst layer is preferably not formed orientation. Alternatively, even if the second catalyst layer has a preferential orientation, in this case, the preferred orientation of the second catalyst layer preferably has a preferred orientation of the {111} or {110} plane.

In addition, it has a surface structure in which a height difference or a step is formed between the first catalyst layer and the second catalyst layer. The multilayered composite catalyst structure having a height difference as described above can further widen the reaction area in which the catalyst reacts, thereby increasing the effective area of the catalyst and improving the conversion efficiency of carbon dioxide.

The second catalyst layer may be a 0-dimensional structure such as a dot or a 1-dimensional structure such as a wire, a needle, and a thin column.

In addition, the second catalyst layer may be a thin film or have a two-dimensional planar structure such as island-shaped particles.

The morphology of this second catalyst can be determined to be the most efficient shape in accordance with the processing method for forming the secondary catalyst.

For example, if the secondary catalyst layer is formed by vapor deposition, the secondary catalyst layer formed in this case may mainly have a two-dimensional planar structure such as a thin film.

On the other hand, if the secondary catalyst layer is formed by a process such as printing, in this case, the secondary catalyst layer may be in the form of a thick film or an island-shaped two-dimensional planar structure, depending on the shape of the screen or the paste, It may be one-dimensional such as or have a zero-dimensional shape such as a dot.

On the other hand, the composite catalyst in the present invention may further contain elements such as oxygen, nitrogen, or hydrogen in the Cu catalyst, either naturally or by artificial subsequent steps such as oxidation treatment, nitriding treatment, or hydrogenation treatment.

In addition, the composite catalyst according to the present invention may naturally add compounds such as Cu oxide, Cu nitride, Cu oxynitride or Cu hydrate to the Cu catalyst by an artificial subsequent process such as oxidation treatment, nitriding treatment or hydrogenation treatment. It may also include.

The first catalyst layer and the second catalyst layer in the composite catalyst of the present invention may each contain different elements.

As described above in FIG. 5, the C 2 dimerization reaction is more advantageous in terms of reaction rate or thermodynamic in the vicinity of Cu interfaces in different oxidation states. In the case of a metal including Cu, when the alloy is formed by including different components from the matrix or the base metal, the metal having a high ionization tendency is more easily oxidized due to the difference in ionization tendency between different metal components. Thus, if the first and second catalyst layers in the composite catalyst of the present invention contain different elements, the respective Cus in the first and second catalyst layers may have different oxidation states, thereby resulting in a C2 dimerization reaction. Can be further promoted.

The complex catalyst in the present invention may be prepared through the method as shown in FIGS. 6 and 7.

First, Cu raw materials are prepared (S1). At this time, the Cu raw material may be in various forms such as copper plate, copper foil, and copper. It may also be a Cu alloy based on Cu and containing some other components.

Next, the Cu raw material is subjected to the first processing step such as cold working (S2).

In polycrystalline metals such as Cu raw materials, multi-slip easily occurs due to the interdependence of neighboring grains, which causes work hardening, a hardening phenomenon in which the material is hardened by processing. The plastic deformation performed in the temperature range and time at which such work hardening does not loosen is generally called cold working.

Plastic deformation causing work hardening increases the number of dislocations inside Cu raw materials. In the annealing metal, the number of dislocations is about 10 ⁶ to 10 ⁸ per cm 2, whereas the dislocation density of the heavily deformed metal is about 10 ¹² . These cold processed tissues form high potential densities (tangles), which develop into a tangled dislocation web.

Most of the energy consumed by cold working Cu raw materials is actually converted to heat. Only about 10% of the energy consumed is stored inside the metal, ie the lattice, increasing the internal energy. Most of this stored energy is due to the generation and interaction of dislocations during cold working. Vacancies can also account for some of the stored energy of the deformed metal at very low temperatures, but the vacancy is easier to move away from the dislocation at room temperature because it is much more mobile than the potential. Stacking faults and twin faults also account for only a fraction of the stored energy. In addition, elastic strain energy is also responsible for only a small amount of stored energy.

After the deformation step, a second catalyst layer of the composite catalyst of the present invention is formed on the Cu raw material through a secondary processing step (S3) such as a low stress processing process.

The low stress machining process refers to a process that does not apply relative or absolute stress to the previous deformation step.

More specifically, the low stress machining step in the present invention is a step of locally forming the second catalyst layer through a process such as deposition, plating, or printing on the Cu raw material serving as the raw material of the matrix and the first catalyst layer.

If the second catalyst layer formed at this time is shaped like a dot, this corresponds to a 0-dimensional structure. On the other hand, the second catalyst layer may be a one-dimensional structure such as a wire, a needle, and a thin column. Furthermore, the second catalyst layer may be a thin film or have a two-dimensional planar structure such as island-shaped particles.

Next, the cold processed Cu raw material and the catalyst which has undergone the low stress processing process go through an annealing process step (S4).

More specifically, the annealing process refers to annealing the composite catalyst including the cold-processed Cu raw material and the second catalyst layer by a low stress processing process located on the raw material.

This annealing process greatly changes the microstructure in the metal.

In general, the cold worked state is a state that has a greater internal energy by processing than the undeformed metal. Thus, the dislocation cell structure in the cold worked material may be mechanically stable but thermodynamically unstable. And as the temperature increases, the cold worked state becomes more unstable. Eventually, the metal changes into a softening, strain-free tissue. This whole process is called annealing.

In general, the annealing process can be classified into three stages: recovery, recrystallization, and grain growth. However, in the annealing step of the catalyst in the present invention, the smaller the grains, the more grain boundaries, which are boundary portions between the grains, and therefore, it is preferable not to proceed until the grain growth step.

Recovery is the step in which the physical properties of the metal are restored without much change in the microstructure of the cold worked metal. During recovery, the conductivity increases sharply and the deformation of the lattice decreases considerably. The property most affected by recovery is that it is sensitive to point defects. The intensity controlled by the potential is not much affected by the recovery temperature.

Recrystallization refers to the substitution of cold grains with new grains without deformation. Recrystallization can be easily determined by observing the microscopic tissue. When recrystallization occurs, hardness or strength decreases, ductility increases, dislocation density decreases significantly, and all effects of work hardening are lost. The thermodynamic driving force for recovery and recrystallization is the energy stored by cold working.

In the present invention, the composite catalyst including the cold-processed Cu raw material and the second catalyst layer by the low stress working process positioned on the raw material undergoes recovery and recrystallization during the annealing process to change the microstructure.

More specifically, during the annealing process, the Cu raw material corresponding to the base in the composite catalyst of the present invention has a microstructure having new grains without deformation through stress relaxation in a high stress state where deformation is severe. At this time, a new microstructure without deformation due to recrystallization is grown with the {100} direction having the smallest Young's modulus as the first direction, as shown in FIG. As a result, the Cu raw material corresponding to the base in the composite catalyst according to the present invention becomes a first catalyst layer of a microstructure having a preferential orientation in the {100} direction.

On the other hand, the second catalyst layer positioned on the Cu raw material constituting the first catalyst layer may have various orientations without the preferred orientation by the secondary processing step or may have the {100} preferred orientation.

If the secondary machining step is a low stress machining process, sufficient processing amount to be recrystallized by the annealing step is not provided to the secondary catalyst layer, so that the secondary catalyst layer has no orientation or at least elastically the most flexible. (soft) {100} will not have priority.

On the other hand, if the secondary processing step proceeds to processes such as deposition and plating, and the processes are carried out under conditions in which the movement of atoms is very free, the secondary catalyst layer by secondary processing has the smallest {111} interfacial energy of Cu. First of all, the possibility of having a bearing becomes very high.

On the other hand, if the secondary processing step is carried out in a process with a large amount of processing, such as the primary processing step, the secondary catalyst layer after the annealing step is likely to have the same {100} preferred orientation as the primary catalyst layer.

As shown in FIG. 5, for dimerization in which CO (carbon monoxide) and CO are bonded by CC coupling, it is more preferable that the surfaces of the catalysts to which carbon monoxide is adsorbed have different surface characteristics. Do. Therefore, it is better to use a low stress machining process in which the second catalyst layer does not have a preferential orientation unlike the first catalyst layer, or may have a {111} or {110} preferred orientation different from the preferred orientation of the first catalyst layer even if it has the first catalyst layer. desirable.

On the other hand, the composite catalyst of the present invention can be prepared through other methods as shown in Figure 9, unlike the above 6 and 7.

Specifically, the method in FIG. 9 does not require an annealing process step, unlike in FIGS. 6 and 7.

More specifically, the method of FIG. 9 includes preparing a Cu raw material (S'1), performing a primary processing step (S '2) for hot deformation of the Cu raw material at a temperature above a temperature at which dynamic recrystallization occurs, and dynamic recrystallization. It occurs by forming a second catalyst layer through the secondary processing step (S'3), such as a low stress processing process occurs on the Cu raw material formed {100} first orientation.

The method in FIG. 9 is characterized by having a {100} preferred orientation in the Cu raw material by generating recrystallization with processing in the primary processing step as compared to the method comprising the annealing process described above.

The process in which recrystallization occurs in the machining step is called dynamic recrystallization. This dynamic recrystallization is in contrast to static recrystallization, which is a recrystallization that occurs during the annealing process, which means that nucleation and growth of new grains without defects occurs during processing or deformation.

Since the dynamic recrystallization has a softening effect due to the recrystallization during processing, the occurrence of the dynamic recrystallization can be confirmed from the occurrence of a peak peculiar to the recrystallization in the stress curve in the stress-displacement curve.

Therefore, when dynamic recrystallization is generated by adjusting process variables or conditions, it is possible to form a first catalyst layer having a preferential direction through recrystallization without performing a subsequent heat treatment process. In this way, the production time of the composite catalyst can be reduced, thereby greatly increasing productivity.

Example

In the present invention, a copper plate having a purity of 98% having a thickness of 100 to 150 um was prepared as a Cu raw material.

As a specific method of cold working, the copper plate was first subjected to cold rolling in one to three passes using a rolling mill on the copper plate, and the rolling reduction per pass was set to 18% to 30%.

The cold rolled copper plate again formed a second catalyst layer on the copper plate through sputtering.

Specifically, the sputtering process uses a polycrystalline Cu target first initial vacuum <10 ^{- 6} torr maintained then back filled with Ar of 100sccm into the chamber, 1mTorr of 200 ~ 1000W from an acceleration voltage range of 20 ~ 50V in the chamber vacuum A copper layer thin film having a thickness of about 100 to 500 nm was deposited on the copper plate through DC sputtering under power conditions.

The copper plate on which the copper layer was deposited was subjected to annealing in a vacuum atmosphere for 1 hour at a temperature of 200 ° C. again to prevent oxidation, and the Cu oxide layer on the surface of some formable was chemically etched with HCl for precise analysis. .

Table 1 summarizes the crystal orientation of the copper plate according to the number of passes after the annealing treatment, and FIG. 10 shows the microstructure of the copper plate according to the number of passes.

Table 1. Crystal Orientation (%) of Old Plates According to Number of Passes

First, as shown in Table 1, it can be seen that as the number of passes increases, the {100} preferred orientation becomes larger.

As described above, first, as the amount of cold deformation increases, the amount of strain energy accumulated in the copper plate increases. As such, the strain energy accumulated in the metal acts as a driving force for recrystallization into new grains without defects during annealing. As a result, the recrystallized microstructure has the softest elasticity, that is, the {100} preferred orientation having the smallest Young's modulus.

On the other hand, Figure 10 is a diagram showing the crystallographic orientation of the material for each rolling pass, it can be clearly seen that the more grains arranged in the {100} direction as the pass increases.

FIG. 11 shows experimental results of analyzing a reaction gas converted in an electrochemical cell for decomposing carbon dioxide, which is prepared using a composite catalyst having different {100} preferred orientations and having a first catalyst layer and a second catalyst layer, respectively.

The electrochemical cell used in FIG. 11 has a structure as shown in FIG. 1 and was manufactured using a beaker cell of three electrodes.

Looking at more specific experimental conditions, as a working electrode (working electrode) was used a complex catalyst including a first catalyst layer and a second catalyst layer prepared in an embodiment of the present invention, as a counter electrode and a reference electrode Pt and Ag / AgCl were used, respectively. 0.1 M KHCO ₃ was used as an electrolyte, and a reaction gas generated by applying a charge amount of 4 to 10 coulombs (C) at -1.9 V (vs. Ag / AgCl) was collected. The collected reaction gas was analyzed using gas chromatography (GC).

At this time, Faraday's efficiency (Faradaic efficiency) for ethylene (C ₂ H ₄ ) is defined as follows.

Faradaic Efficiency = (generated C ₂ H ₄ Confiscated XC ₂ H ₄ Number of electrons needed to produce 1 mole X Faraday constant) / Total amount of charge applied to cathode X 100%

Referring to FIG. 11, first, when copper (Cu) having a {100} preferred orientation of 24% was used as a catalyst for a cathode, the Faradaic efficiency for ethylene (C ₂ H ₄ ) was about 43% at the beginning of the reaction. It was measured to decrease over time after showing maximum efficiency. In contrast, when copper (Cu) having a {100} preferred orientation of 95.5%, which corresponds to an embodiment of the present invention, was used as a catalyst for a negative electrode, Faraday's efficiency for ethylene (C ₂ H ₄ ) was reacted. It was initially measured to show a maximum efficiency of about 63% and then decrease over time.

The results of FIG. 11 may indicate that the copper catalyst having the {100} preferred orientation of the present invention is very effective for generating C 2 or more hydrocarbons.

As described above, the present invention has been described with reference to the drawings, but the present invention is not limited to the embodiments and drawings disclosed herein, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. It is obvious that modifications can be made. In addition, even if the above described embodiments of the present invention while not explicitly described and described the operation and effect according to the configuration of the present invention, it is obvious that the effect predictable by the configuration is also to be recognized.

Claims (13)

A first catalyst layer comprising a Cu polycrystalline base having the {100} plane first in orientation;
A second catalyst layer positioned on the first catalyst layer, the second catalyst layer including a polycrystalline layer made of Cu;
Composite catalyst comprising a. The method of claim 1,
The fraction of the {100} plane in the Cu polycrystalline base is 30% or more;
Complex catalyst characterized in that. The method of claim 1,
The polycrystalline layer in the second catalyst layer is not first formed in an orientation;
A composite catalyst characterized by the above. The method of claim 1,
The polycrystalline layer in the second catalyst layer has a preferred orientation of the {111} or {110} plane;
A composite catalyst characterized by the above. The method of claim 1,
Having a surface structure in which a height difference or a step is formed between the first catalyst layer and the second catalyst layer;
Complex catalyst characterized in that. The method of claim 1,
The second catalyst layer is a one-dimensional structure in the form of a dot or a one-dimensional structure in the form of a wire, a needle, and a column, or a two-dimensional structure in the form of a thin film or an island;
Complex catalyst characterized in that. The method of claim 1,
The composite catalyst includes one or more elements of oxygen, nitrogen, or hydrogen in the catalyst;
Complex catalyst characterized in that. The method of claim 1,
The composite catalyst comprises at least one of Cu oxide, Cu nitride, Cu oxynitride or Cu hydride inside the catalyst;
Complex catalyst characterized in that. The method of claim 1,
The first catalyst layer and the second catalyst layer each containing different elements;
Complex catalyst characterized in that. Preparing a Cu raw material constituting the first catalyst layer;
A primary processing step of deforming the Cu raw material;
Forming a second catalyst layer on the Cu raw material;
Annealing step;
Method for producing a composite catalyst comprising a. Preparing a Cu raw material constituting the first catalyst layer;
A primary processing step of dynamically recrystallizing the Cu raw material;
Forming a second catalyst layer on the Cu raw material;
Method for producing a composite catalyst comprising a. The method according to claim 11 or 12, wherein
The first machining step is multi-pass rolling;
Method for producing a composite catalyst, characterized in that. The method according to claim 11 or 12, wherein
The secondary processing step includes one or more processes of deposition, plating, or printing;
Method for producing a composite catalyst, characterized in that.

Images