WO2019151715A1 - Catalyst for carbon dioxide conversion and method for preparing same - Google Patents

Abstract

The present invention relates to an electrochemical cell used for decomposing carbon dioxide and reducing into useful converted product, and a catalyst used for a cathode electrode in the cell. According to the present invention, provided is a composite catalyst comprising: a first catalyst layer comprising a Cu polycrystalline base having {100} preferred orientation; and a second catalyst layer positioned on the first catalyst layer and comprising a polycrystalline layer formed from Cu.

Description

Carbon dioxide conversion catalyst and its manufacturing method

The present invention relates to an electrochemical cell used when decomposing carbon dioxide and converting it into a useful product, and a catalyst used for an electrode for a cathode in the cell.

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.

Carbon dioxide is known to be a major cause of global warming. Accordingly, 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.

The application of energy to carbon dioxide has recently received a lot of attention as a method of removing carbon dioxide generated by the conversion technology that converts it into useful resources such as carbon compounds and oxygen. Pressure conversion at high temperatures or the use of catalysts include such conversion techniques.

Among the 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 is very easy to scale up to a commercial scale. In addition, the method using the catalyst has the advantage that it can selectively produce a variety 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 production of hydrocarbons of C2 or more have attracted attention.

In case of the Cu catalyst, C1 (carbon monovalent hydrocarbon such as CH ₄ ) is more generated than C2 + (carbon divalent hydrocarbon such as C ₂ H ₄₎ among the products generated by the reduction of carbon dioxide. It is known.

Meanwhile, in the case of the Cu ₂ O catalyst, the C2 + production rate is higher than the C1 production rate. However, the reduction reaction proceeds in accordance with Cu ₂ O in the catalyst from the monovalent Cu + 1 ions are to occur the reduction of the Cu atom thereby C2 + generation rate of carbon dioxide, there is a problem that continues to decrease.

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.

In a catalyst for a cathode in which reduction occurs in an electrochemical cell used for the decomposition of carbon dioxide, the present invention provides a novel catalyst comprising a surface structure having crystallographic preferential orientation for the production of C2 or higher hydrocarbons. 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 preparing a catalyst that is easy to scale up on an economical and commercial scale using equipment or processes that are conventional and commercially widely used in the existing metal field without any expensive equipment or process. I would like to.

According to one embodiment of the present invention in order to include a surface structure having a crystallographically preferential orientation favoring C2 or higher hydrocarbon generation and having different interface or grain boundary properties on the surface, the {100} plane is A first catalyst layer comprising a Cu polycrystalline base having a preferred orientation; 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.

Another method of the present invention is to provide a manufacturing method that is easy to scale up on an economical and commercial scale by using equipment or processes that are conventional and commercially widely used in the existing metal field without any expensive equipment or process. According to an embodiment, 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, specifically, C2 or more useful hydrocarbon compounds in the decomposition of carbon dioxide can be selectively produced in higher proportion than other hydrocarbons.

Accordingly, the catalyst of the present invention is more effective in producing C2 or more hydrocarbons than other catalysts.

In addition, since the catalyst of the present invention includes a large number of 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, the method of preparing the catalyst of the present invention makes it easy to prepare a catalyst having excellent carbon dioxide conversion efficiency by applying equipment and processes commercially readily 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.

Meanwhile, another method for preparing a catalyst of the present invention can produce a catalyst having excellent hydrocarbon conversion efficiency of C2 or higher without additional subsequent heat treatment.

Therefore, another catalyst manufacturing method of the present invention can omit a long time and energy-consuming unit process such as heat treatment, thereby having an excellent productivity and economic efficiency.

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

FIG. 2 illustrates the ratio of hydrocarbons generated when carbon dioxide is decomposed on a surface of a copper oxide catalyst composed of a Cu catalyst and a Cu ion having an oxidation number of +1.

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.

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

FIG. 5 shows energy levels in the transition and final levels required for the formation of hydrocarbons above C2 on various catalyst surfaces.

6 is a flowchart illustrating a method according to one embodiment 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 flowchart illustrating a method according to another embodiment of preparing a composite catalyst of the present invention.

FIG. 10 illustrates 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 an experimental result of analyzing a reaction gas converted in an electrochemical cell for decomposing carbon dioxide, which is prepared using a composite catalyst having a first catalyst layer and a second catalyst layer and having a different {100} preferred orientation.

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. When 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 And a membrane positioned between the cathodes and selectively passing only the desired components on the electrolyte.

Although not shown in FIG. 1, the cell includes an energy supply source for supplying energy from the outside to drive the cell. In addition, an extractor for extracting the by-product generated from the reduction of the carbon dioxide is further included. In addition, an electrolyte supply device may be added as necessary.

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

When carbon dioxide is decomposed and reduced in a cell as shown in FIG. 1, it is known that various by-products (or conversion products or products) are produced depending on the type of catalyst in which a reduction reaction occurs.

_{^{CO 2 + nH + + ne -}} → C x H y O z (1)

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

_{^{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)

FIG. 2 illustrates the ratio of hydrocarbons generated when carbon dioxide is decomposed on a surface of a copper oxide catalyst composed of a Cu catalyst and a Cu ion having an oxidation number of +1.

As shown in FIG. 2, when Cu in a metal state is used as a catalyst, CH ₄ and C ₂ H ₄ are generated on the surface of the Cu catalyst by reduction of carbon dioxide. At this time, the formation rate of each of CH ₄ and C ₂ H ₄ is similar, but it can be seen that CH ₄ occupies more fraction than C ₂ H ₄ .

In contrast, if Cu having an oxidation number of +1 is used as the catalyst, the reduction of carbon dioxide at the surface of the +1 Cu catalyst produces mainly CH ₄ and C ₂ H ₄ . However, C ₂ H ₄ in the resulting hydrocarbon is the ratio of CH ₄ can be seen to occupy a greater fraction of up to 15 or more times that of the C ₂ H ₄ CH _4. Accordingly, it can be seen that Cu having an oxidation number of +1 has a very advantageous effect on the generation of C2 or more hydrocarbons as a catalyst of an electrochemical cell for reducing carbon dioxide.

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

Although the Cu catalyst is chemically the same catalyst, the orientation of the {100} plane rather than the {111} plane orientation has been investigated as in FIG. 3 to maintain a lower energy state for all C2 hydrocarbon productions investigated.

3 shows, by way of example, a free energy state for the production of a hydrocarbon called "+ OCCHO". Considering the free energy state of the entire thermodynamic system, FIG. 3 shows that the free energy of the state where "+ OCCHO" is generated is higher than the free energy of the two carbon monoxide combinations on the {111} plane of Cu. The results of FIG. 3 indicate that in order to generate “+ OCCHO” hydrocarbons from carbon monoxide, energy must be supplied externally to compensate for the thermodynamically high energy state of the final “+ OCCHO” hydrocarbons, in addition to the This means that more energy must be supplied from outside to overcome the activation step.

On the contrary, on the {100} side of Cu, the free energy state of two carbon monoxide bonds and the free energy state of the hydrocarbon "+ OCCHO" were almost identical. In addition, the activation energy of the hydrocarbon production reaction was also found to be lower than the activation energy of the {111} plane.

These results indicate that the {100} plane of Cu can form thermodynamically stable "+ OCCHO" hydrocarbons with less energy than the {111} plane. In addition, the activation energy for causing the hydrocarbon generation or carbon monoxide conversion reaction on the Cu surface also means that the {100} plane of Cu is required to be smaller than the {111} plane.

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, Cu metal is produced by melting and casting, hot working and / or cold working, heat treatment and, if necessary, etching or surface treatment.

On the other hand, face centered cubic (FCC) such as Cu generally has the lowest surface energy in terms of surface energy, and thus the {111} plane becomes the most stable surface. On the other hand, in a metal having a cubic lattice such as Cu, the <100> direction is the softest direction elastically.

However, due to thermodynamic factors or the fine turbulence that occurs during the melting and casting process, the as-cast microstructure formed through melting or casting, which is a common metal fabrication process, is a single crystal composed of only one grain. It is not formed into a single crystal. Instead, the cast microstructure consists of poly-crystal microstructures consisting of grains with different crystallographic orientations.

The cast microstructures are all destroyed by hot working and / or cold working and subsequent heat treatment to finally form a processed microstructure consisting of fine polycrystals.

At this time, the orientations of the respective grains in the final polycrystalline microstructure are generally known to be randomly distributed as shown in FIG. 4. The result of Cu polycrystal orientation analysis in FIG. 4 is consistent with the orientation distribution obtained after hot and / or cold working and subsequent heat treatment of a general metal material. Specifically, FIG. 4 shows the orientation of {111} planes or {100} planes having a small surface energy or elastic energy, but a small number and a high distribution of {101} planes.

On the other hand, the crystallographic orientation measurement results of the conventional Cu catalyst of FIG. 4 agree well with those of FIGS. 2 and 3.

The crystal orientation analysis of the conventional Cu catalyst in FIG. 4 shows that the proportion of {100} planes occupying the surface of the Cu catalyst is very small, 2.1%. The results in FIG. 4 mean that, as shown in FIG. 3, the {100} plane of Cu advantageous for C2 hydrocarbon production is scarce on the surface of a conventional Cu catalyst. And the small fraction of the {100} plane on the Cu surface is in good agreement with the relatively small C ₂ H ₄ conversion ratio in the Cu catalyst shown in FIG.

FIG. 5 shows energy levels in the transition and final levels required for the formation of hydrocarbons above C2 on various catalyst surfaces.

First, when the surface of the Cu metal catalyst mainly has the {111} plane, the CO molecules adsorbed on the surface of the catalyst are inclined in order for the C2 hydrocarbon-forming dimerization called OCCO to occur by the combination of CO and CO. Then, after passing through a transition stage where the two CO molecules come close to each other, a surface species called OCCO is finally formed. The free energy at the transition and final stages is 1.1 eV and 0.86 eV, respectively, compared to the free energy of the two initial CO molecular stages. The free energy difference means that dimerization may occur due to the combination of CO (carbon monoxide) and CO in a Cu metal catalyst having a surface of {111} when only an energy of 1.1 eV or more is supplied from the outside. In other words, in the Cu metal catalyst having the {111} plane, dimerization by the combination of CO (carbon monoxide) and CO has a free energy barrier of 1.1 eV.

On the other hand, in a composite catalyst in which a metal oxide of Cu ₂ O and a Cu metal having a {111} plane coexist, when a C2 hydrocarbon-forming dimerization reaction of CO in a Cu atom and a CO atom in a + 1-valent Cu ion occurs, OCCO, The free energy in the stage and the final stage differs by 0.71 eV and 0.12 eV, respectively, compared to the free energy of the initial stage. The free energy difference means that the reaction may occur in a catalyst in which a metal oxide of Cu ₂ O and a Cu metal catalyst having a {111} surface coexist 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 Cu ₂ O metal oxide and Cu metal is that C in CO adsorbed at +1 valence Cu ions is positively charged while adsorption at Cu atoms. This is because C in the CO is negatively charged. Thus electrostatic attraction for the formation of CC bonds between the two Cs makes energy energizing better CC coupling in the composite catalyst of Cu ₂ O metal oxide and Cu metal. This means that the electrostatic attraction increases the kinetics or thermodynamic driving forces for the C2 dimerization reaction.

In general, since the surface of the metal is in an unstable state in which the bonds of the metal atoms are broken, the metal atoms located on the surface cannot exist only in the state of the metal atoms. As a result, an oxide film is naturally formed on the surface of pure metal. In addition, the general characteristics of the metal surface are applied to the Cu metal catalyst as it is, and Cu atoms on the Cu metal surface exist as oxides such as CuOx, not pure metal states.

Accordingly, the present invention completed a Cu metal catalyst having a new structure by controlling and controlling the crystallographic orientation of the conventional Cu metal catalyst to convert carbon dioxide to form C2 or more hydrocarbons with high efficiency.

To this end, in one embodiment of the present invention, the catalyst includes a first catalyst layer including a Cu polycrystalline base having a {100} plane in a preferred direction, and a second catalyst layer disposed on the first catalyst layer and including a polycrystalline layer made of Cu. It is a composite catalyst comprising a.

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 crystallographic effects on C2 hydrocarbon formation.

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

In addition, the composite catalyst according to the embodiment of the present invention has a surface structure in which a height difference or a step is formed between the first catalyst layer and the second catalyst layer. As described above, the multi-layered composite catalyst having a height difference can widen the reaction area where the catalyst reacts, and as a result, the effective area of the catalyst can be widened, thereby 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.

Such a morphology of the second catalyst can be determined to be the most efficient shape that matches the processing method for forming the second catalyst.

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

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

Meanwhile, the composite catalyst in the embodiment of the present invention may additionally include elements such as oxygen, nitrogen, or hydrogen in the Cu catalyst naturally or by an artificial subsequent process such as oxidation treatment, nitriding treatment, or hydrogenation treatment.

In addition, the composite catalyst in the embodiment of the present invention may additionally include Cu oxide, Cu nitride, Cu oxynitride, Cu hydrate, or the like within the Cu catalyst naturally or by artificial subsequent processes such as oxidation treatment, nitriding treatment, or hydrogenation treatment. It may also contain a compound.

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

As described above in FIG. 5, the C2 dimerization reaction is more advantageous near the interface of Cu in different oxidation states in terms of reaction rate or thermodynamics. When the metal including Cu is formed in an alloy state including the base or the base material and different components, the metal component having a high ionization tendency is more easily oxidized due to the difference in ionization tendency between different metal components. Therefore, if the first catalyst layer and the second catalyst layer in the composite catalyst in the embodiment of the present invention contains different elements, the oxidation state of each Cu in the first catalyst layer and the second catalyst layer may be different from each other. And the C2 dimerization reaction may be further promoted due to the different oxidation states of Cu.

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

First, Cu raw materials are prepared (S1). At this time, various forms such as copper plate, copper foil, and copper can be used as the Cu raw material. In addition, the Cu raw material may 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, multi-slip easily occurs because of the interdependency of neighboring grains. As a result, work hardening, which is a phenomenon that the material is hardened by work, occurs. The so-called cold working refers to plastic deformation performed in a temperature range and time at which the work hardening is not solved.

The plastic deformation causing work hardening increases the number of dislocations inside the Cu raw material. In the annealing metal, the number of dislocations is about 10 ⁶ to 10 ⁸ per cm 2, whereas the dislocation density in the heavily deformed metal is about 10 ¹² / cm 2. Dislocation tangles are formed in the cold processed tissue, and the dislocation tangles develop back into a dislocation web.

Most of the energy consumed by cold processing Cu raw materials is transformed into heat. Only about 10% of the energy consumed is stored inside the metal, or lattice, and the internal energy of the metal increases. Most of this stored energy comes from 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 energy stored inside the metal. In addition, the elastic strain energy is also responsible for only a small amount of the stored energy.

Thereafter, a second catalyst layer of the composite catalyst of the embodiment 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 stage of the first machining step.

More specifically, the low stress machining process in the embodiment of the present invention locally forms the second catalyst layer through a process such as deposition, plating, or printing on Cu raw material serving as a raw material of the base and / or the first catalyst layer. It is a process to do it.

If the formed second catalyst layer is shaped like a dot, the shape of the second catalyst layer 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.

The annealing process greatly changes the microstructure inside the metal.

In general, cold worked metals have greater internal energy by machining than undeformed metals. Thus, dislocation cell tissue in the cold worked metal may be mechanically stable but thermodynamically unstable. And the cold worked state becomes more unstable by the thermal activation of atoms as the temperature increases. When the temperature rises, the metal eventually changes into a softening and non-deforming tissue. This whole process is called annealing.

The annealing process can be generally classified into three stages: recovery, recrystallization, and grain growth. However, the smaller the grain size of the catalyst in the embodiment of the present invention, the larger the grain boundary, which is the boundary portion between the grains, and therefore, the annealing process of the embodiment of the present invention is preferably not performed until the grain growth step.

Recovery is a step in which the microstructure of the cold worked metal is little changed and the physical properties of the metal are mainly recovered. During recovery, the conductivity increases sharply and the deformation of the lattice decreases considerably. The physical properties most affected by recovery are those that are sensitive to point defects. In contrast, the intensity controlled by dislocations is not much affected by recovery.

Recrystallization refers to the replacement 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 embodiment of the present invention, the microstructure of the composite catalyst including the cold-processed Cu raw material and the second catalyst layer by the low stress machining process located on the raw material is changed through recovery and recrystallization during the annealing process.

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. 8. As a result, in the composite catalyst of the present invention, the Cu raw material corresponding to the base becomes a first catalyst layer including a microstructure having a preferred 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, a sufficient processing amount to be recrystallized by the annealing step is not provided to the secondary catalyst layer by low stress machining. As a result, the secondary catalyst layer does not have a preferred orientation or at least elastically does not have the softest {100} preferred orientation.

On the other hand, if the secondary processing step proceeds to processes such as deposition and plating, and the processes are performed under conditions in which the movement of atoms is very free, the second catalyst layer by secondary processing has the smallest 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 second catalyst layer after the annealing step is likely to have a {100} priority direction the same as the first catalyst layer.

As described above with reference to 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. . Therefore, it is preferable that the second catalyst layer does not have a preferential orientation unlike the first catalyst layer or has a {111} or {110} preferred orientation different from the preferred orientation of the first catalyst layer even if it has. Therefore, it is more preferable that secondary processing uses a low stress processing process.

Meanwhile, the composite catalyst of the embodiment of the present invention may be prepared by the same method as in FIG. 9, unlike FIGS. 6 and 7.

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

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

This process in which recrystallization occurs together in the machining step is called dynamic re-crystallization. The dynamic recrystallization is a concept opposite to the static recrystallization which is a recrystallization occurring during the annealing process, and the dynamic recrystallization means that nucleation and growth of new grains without defects occur 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-displacement curve.

Therefore, when dynamic recrystallization occurs through the control of process variables or conditions, the first catalyst layer having a preferential orientation may be formed through recrystallization without performing a subsequent heat treatment process. In addition, productivity can be greatly improved by reducing the time for preparing the composite catalyst through dynamic recrystallization.

Example

In the embodiment of 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.

First, a cold rolling of 1 to 3 passes was performed on the copper plate using a rolling mill as a specific method of cold working, and the rolling reduction rate per pass was set to 18% to 30%.

A second catalyst layer was then formed on the cold rolled copper plate through sputtering.

Specifically, the sputtering process is as follows. DC sputtering using a polycrystalline Cu target at an acceleration voltage range of 20 to 50 V and a power condition of 200 to 1000 W under a chamber vacuum of 1 mTorr after first maintaining an initial vacuum of <10 ^-6 torr and then filling 100 sccm of Ar into the chamber. The copper layer thin film of about 100 ~ 500nm thickness was deposited on the copper plate through.

The copper plate on which the thin copper layer is deposited is annealed for 1 hour at a temperature of 200 ° C. in a vacuum atmosphere to prevent oxidation, and the Cu oxide layer of the surface, which may be formed on a part of the surface, may be HCl or the like for precise analysis. Chemically etched.

Table 1 summarizes the crystal orientation according to the number of cold rolling passes of the final annealed copper sheet. FIG. 10 illustrates the microstructure of the copper plate according to the number of rolling passes when performing the primary processing step with cold rolling.

Table 1. Crystal orientation of copper plate according to the number of cold rolling passes (%)

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

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 in which a new microstructure composed of new grains free of defects during annealing is produced. As a result, the recrystallized microstructure has the softest elasticity, that is, the {100} preferred orientation having the smallest Young's modulus.

10 is a diagram showing the crystallographic orientation of the material along the cold rolling pass. It can be clearly seen from FIG. 10 that as the cold rolling pass increases, more grains are arranged in the {100} direction.

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

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

Looking at the more specific experimental conditions, as a working electrode (composite) a composite catalyst comprising a first catalyst layer and a second catalyst layer prepared in an embodiment of the present invention was used 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 gases were analyzed using gas chromatography (GC).

In this case, Faradaic efficiency for ethylene (C ₂ H ₄ ) is defined as follows.

Faradaic Efficiency = (number of generated C ₂ H ₄ moles XC ₂ H ₄ electron number X Faraday constant needed to generate 1 mole) / total amount of charge applied to the cathode X 100%

11, the Faradaic efficiency for ethylene (C ₂ H ₄ ) in a cathodic catalyst using copper (Cu) with {100} preferred orientation of 24% is maximum of about 43% at the beginning of the reduction reaction. After showing efficiency, it was measured to decrease with time. In contrast, Faradaic efficiency for ethylene (C ₂ H ₄ ) in a catalyst for anodes using copper (Cu) having a {100} preferred orientation of 95.5%, corresponding to an embodiment of the present invention, was about 63 at the beginning of the reaction. It was measured to decrease over time after showing the maximum efficiency of%.

The above results on Faradic efficiency of ethylene (C ₂ H ₄ ) according to the catalyst for the negative electrode of Figure 11 means that the copper catalyst having the {100} preferred orientation of the embodiment of the present invention is very effective for the production of hydrocarbons of C2 or more It is.

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)

1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
6. 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.
7. 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.
8. 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.
9. The method of claim 1,

   The first catalyst layer and the second catalyst layer each containing different elements;

   Complex catalyst characterized in that.
10. 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.
11. 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.
12. 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.
13. 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.

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