Catalyst structure and method for manufacturing catalyst structure

Abstract

To provide a catalyst structure that is easy to manufacture and handle and has a large specific surface area, and a method for manufacturing the catalyst structure.SOLUTION: A catalyst structure used for a reforming reaction for reforming a substance comprises: a substrate having a first surface and a second surface that have a front-back relationship with each other; a roughened coating that is provided on the first surface of the substrate, contains a first metal element, and has a concavo-convex structure with an average pitch from 0.1 μm to 5.0 μm inclusive; and a plurality of granular bodies that contain a second metal element, are in contact with the roughened coating, and have an average particle diameter smaller than the average pitch.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a catalyst structure and a method for making the catalyst structure. [Background technology]

[0002] In reforming reactions, in which a raw material is reformed to obtain a reformate, a catalyst is used to improve the reaction efficiency. The catalyst comprises a support and an active material supported on the support. One method for improving the reaction efficiency of reforming reactions is to increase the specific surface area of ​​the catalyst, thereby increasing the contact efficiency between the raw material and the catalytic active sites. However, catalysts with large specific surface areas often have unstable shapes, making them difficult to handle.

[0003] For example, Patent Document 1 discloses a zeolite catalyst used for reforming raw materials. This zeolite catalyst contains a mixture of zeolite and a compound containing an alkaline earth metal and silicon. Such a zeolite catalyst is produced by kneading powdered zeolite and the compound, extruding the mixture, and then calcining the mixture. This produces a catalyst with a large specific surface area and a shape that is easy to use industrially. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-136702 Summary of the Invention [Problem to be solved by the invention]

[0005] The zeolite catalyst described in Patent Document 1 is produced by molding a mixture of powdered zeolite and a compound, followed by calcining the mixture. Therefore, the production of such a catalyst requires large-scale production equipment, making it difficult to produce. Furthermore, since calcination is performed at high temperatures, there is room for further study in terms of stably producing a catalyst with high catalytic activity.

[0006] Therefore, the realization of a catalyst structure that is easy to manufacture and handle and has a large specific surface area is a challenge. [Means for solving the problem]

[0007] The catalyst structure according to the application example of the present invention is A catalyst structure for use in a reforming reaction for reforming a substance, comprising: a substrate having a first surface and a second surface that are opposite surfaces to each other; a roughened coating film provided on the first surface of the substrate, the roughened coating film containing a first metal element and having an uneven structure with an average pitch of 0.1 μm or more and 5.0 μm or less; a plurality of granules containing a second metal element, in contact with the roughened coating, and having an average particle diameter smaller than the average pitch; Equipped with.

[0008] A method for producing a catalyst structure according to an application example of the present invention includes: 1. A method for producing a catalyst structure for use in a reforming reaction to reform a substance, comprising: a metal film forming step of forming a metal film containing a first metal element on a first surface of a substrate having a first surface and a second surface that are opposite surfaces to each other; a roughening step of irradiating the metal film with a pulsed laser to perform sublimation processing to obtain a roughened coating having an uneven structure; a granule forming step of forming, by atomic layer deposition, a plurality of granules in contact with the roughened coating, containing a second metal element, and having an average particle diameter smaller than the average pitch of the uneven structure; It has. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a catalyst structure according to an embodiment. [Figure 2] FIG. 2 is an enlarged view of part A in FIG. [Figure 3] 1A to 1C are process diagrams illustrating a method for producing a catalyst structure according to an embodiment. [Figure 4]4 is a cross-sectional view illustrating a method for manufacturing the catalyst structure shown in FIG. 3. FIG. [Figure 5] 4 is a cross-sectional view illustrating a method for manufacturing the catalyst structure shown in FIG. 3. FIG. [Figure 6] 4 is a cross-sectional view illustrating a method for manufacturing the catalyst structure shown in FIG. 3. FIG. [Figure 7] 4 is a cross-sectional view illustrating a method for manufacturing the catalyst structure shown in FIG. 3. FIG. [Figure 8] 1 is a table showing collision relaxation times of main first metal elements. [Figure 9] This is an example of an SEM (scanning electron microscope) image showing the textured structure created on the surface of a metal film using a pulsed laser. [Figure 10] FIG. 10 is a partially enlarged view of the concave-convex structure shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE INVENTION A catalyst structure and a method for manufacturing a catalyst structure according to the present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings.

[0011] 1.Catalyst structure First, the catalyst structure according to the embodiment will be described.

[0012] Fig. 1 is a cross-sectional view showing a catalyst structure 1 according to an embodiment. Fig. 2 is an enlarged view of part A in Fig. 1. In addition, for convenience of illustration, the dimensional ratios of the various parts in each drawing are different from the actual ratios.

[0013] 1 and 2, the X-axis, Y-axis, and Z-axis are set as three mutually orthogonal axes. Each axis is represented by an arrow, with the tip of the arrow being "plus" and the base of the arrow being "minus." In the following description, for example, the "X-axis direction" includes both the plus and minus directions of the X-axis. The same applies to the Y-axis and Z-axis directions. In the following description, the plus side of the Z-axis will also be referred to as "up" and the minus side of the Z-axis will also be referred to as "down."

[0014] The catalyst structure 1 shown in Figures 1 and 2 is used as a catalyst in a reforming reaction for reforming a substance. The substance to be reformed (substance to be reformed) may be a gaseous substance or a liquid substance, but is particularly preferably used for reforming gaseous substances. Examples of applications of the catalyst structure 1 include an environmental purification catalyst that reforms exhaust gases generated from internal combustion engines to make them less harmful, and a chemical synthesis catalyst that reforms raw materials to synthesize chemical products.

[0015] The catalyst structure 1 shown in FIGS. 1 and 2 comprises a substrate 2, a roughened coating 3, and a plurality of granules 4.

[0016] The substrate 2 has a plate shape extending along the XY plane, and has a first surface 21 that is the upper surface and a second surface 22 that is the lower surface.

[0017] The roughened coating 3 is a coating provided on the first surface 21 of the substrate 2 and contains a first metal element. The roughened coating 3 also has an uneven structure 31 with an average pitch of 0.1 μm or more and 5.0 μm or less.

[0018] The granules 4 are particulate matter that are in contact with the roughened coating 3 and contain a second metal element. The average particle diameter of the granules 4 is smaller than the average pitch of the uneven structure 31.

[0019] One of the roughened coating 3 and the particulate material 4 is a catalyst component, and the other is a support. When these come into contact with each other, catalytic active sites C are formed near the interface between the roughened coating 3 and the particulate material 4. By forming more catalytic active sites C per unit area of ​​the catalyst structure 1, the efficiency of the reforming reaction by the catalyst structure 1 can be increased. As a result, the reaction product can be obtained efficiently.

[0020] The surface area of ​​the concave-convex structure 31 is sufficiently larger than the area of ​​the first surface 21. This makes it possible to realize a catalyst structure 1 in which catalytic active sites C are formed at a high density. Furthermore, because the catalyst structure 1 is plate-shaped, it is easy to handle and can be stacked, for example, which allows for high-density packaging. In other words, by stacking multiple catalyst structures 1 with a predetermined gap between them and placing them in a container, it is possible to construct a reformer in which catalytic active sites C are three-dimensionally accumulated. Such a reformer can achieve high reforming efficiency even in a small space.

[0021] 1.1.Substrate As described above, the substrate 2 has a first surface 21 and a second surface 22 which are opposite surfaces. The substrate 2 is not irregular in shape, and therefore is easy to manufacture and handle. Therefore, the catalyst structure 1 including the substrate 2 is also easy to manufacture and handle.

[0022] Examples of materials constituting the substrate 2 include silicon materials such as silicon and silicon carbide, metal materials such as aluminum and iron, glass materials, ceramic materials, and organic materials such as various resins. Also, the substrate 2 may be a composite material that combines two or more of these materials.

[0023] Of these, it is preferable that the substrate 2 contains silicon. Substrates 2 containing silicon are distributed as silicon wafers, have stable quality, and are easily available. Furthermore, precision processing technology using an etching method has been established for silicon-containing materials, making them suitable as constituent materials for the substrate 2.

[0024] The silicon may be single crystal silicon, polycrystalline silicon, or amorphous silicon.

[0025] The thickness of the substrate 2 in the Z-axis direction is not particularly limited, but is preferably 100 μm or more and 2000 μm or less, more preferably 200 μm or more and 1000 μm or less, and even more preferably 300 μm or more and 600 μm or less. This allows the catalyst structure 1 to be made lighter and thinner while maintaining its rigidity. As a result, a catalyst structure 1 can be realized that is particularly easy to manufacture and handle and that can accumulate catalytic active sites C at a high density.

[0026] The size of the substrate 2 in the XY plane is not particularly limited, but is, for example, preferably 20 mm to 1000 mm, more preferably 50 mm to 500 mm. This allows for a substrate 2 that is easy to manufacture and handle. The above size refers to the maximum length possible in the XY plane.

[0027] 1.2. Roughening coating The roughened coating 3 covers the first surface 21 of the substrate 2. The roughened coating 3 preferably covers the entire first surface 21, but may cover only a portion of the first surface 21. The roughened coating 3 may also cover the second surface 22.

[0028] The roughened coating 3 contains a first metal element. There are no particular limitations on the first metal element, as long as it is an element that can function as a catalyst when present in close proximity to a second metal element. Specific examples of the first metal element include Cu, Pt, In, Zn, Ru, Sn, Au, and Re. Of these, Au is preferred as the first metal element. These elements, including Au, exert particularly high catalytic activity on catalytic active sites C when in contact with the second metal element. When a material to be reformed comes into contact with these catalytic active sites C, it undergoes a reforming reaction and is reformed.

[0029] The content of the first metal element in the roughened coating 3 is not particularly limited, but is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, and particularly preferably 90% by mass or more. If the content of the first metal element is within the above range, the catalytic activity of the catalytic active sites C can be further enhanced, thereby making it possible to further improve the efficiency of the reforming reaction of the raw material by the catalyst structure 1.

[0030] The content of the first metal element in the roughened coating 3 can be determined by qualitative and quantitative analysis using, for example, an electron probe microanalyzer (EPMA).

[0031] If necessary, the roughened coating 3 may contain elements other than the first metal element. That is, the first metal element may exist as a single element, or may exist as a compound or mixture with other elements.

[0032] The roughened coating 3 has an uneven structure 31 as shown in Figure 2. The uneven structure 31 is formed, for example, by adjacent recesses 312. By providing the uneven structure 31, it is possible to increase the surface area of ​​the roughened coating 3 even if the projected area remains the same. In other words, by providing the uneven structure 31, it is possible to increase the specific surface area of ​​the roughened coating 3. This increases the area available for contact with the granular material 4, which will be described later, and increases the number of catalytically active sites C that can be formed per unit area on the surface of the roughened coating 3.

[0033] The average value (average pitch) of the pitch P of the concave-convex structure 31 is 0.1 μm or more and 5.0 μm or less, preferably 0.2 μm or more and 4.0 μm or less, and more preferably 0.3 μm or more and 1.0 μm or less. If the average pitch of the concave-convex structure 31 is within this range, the surface area of ​​the roughened coating 3 can be sufficiently large, and the concave-convex structure 31 can be formed relatively easily.

[0034] If the average pitch is below the lower limit, it becomes more difficult to form the concave-convex structure 31, resulting in an increase in the cost and decrease in production efficiency of the catalyst structure 1. On the other hand, if the average pitch is above the upper limit, the surface area of ​​the roughened coating 3 cannot be made sufficiently large, and the number density of the catalytic active sites C cannot be increased sufficiently.

[0035] The pitch P of the concave-convex structure 31 is the distance between the center points of two adjacent concave portions 312, 312 included in the concave-convex structure 31, as shown in FIG. 2. The center point of the concave portion 312 is the center of gravity of the image of the concave portion 312 in an image (enlarged image) taken from above the concave-convex structure 31. The center of gravity of the image of the concave portion 312 can be identified by performing image processing on the enlarged image. The average value of the pitch P is the average value of 10 pitches P randomly extracted from the enlarged image.

[0036] The average value (average height) of the height H of the concave-convex structure 31 is preferably 0.05 μm or more and 10.0 μm or less, more preferably 0.1 μm or more and 5.0 μm or less, and even more preferably 0.2 μm or more and 2.0 μm or less. If the average height of the concave-convex structure 31 is within this range, the surface area of ​​the roughened coating 3 can be sufficiently large, and the concave-convex structure 31 can be formed relatively easily.

[0037] If the average height is below the lower limit, the surface area of ​​the roughened coating 3 cannot be made sufficiently large, which may result in an insufficient increase in the number density of the catalytic active sites C. On the other hand, if the average height exceeds the upper limit, it becomes more difficult to form the uneven structure 31, which may result in an increase in the manufacturing cost of the catalyst structure 1 and a decrease in manufacturing efficiency.

[0038] The height H of the concave-convex structure 31 is the height of a convex portion 314 located between two adjacent concave portions 312, 312 included in the concave-convex structure 31, as shown in Figure 2. The height H of the convex portion 314 is the height from the center point of the concave portion 312 to the apex of the convex portion 314 in the thickness direction of the roughened coating 3. The average value of the height H is the average value of 10 heights H randomly sampled from the enlarged image.

[0039] The coverage of the roughened coating 3 on the first surface 21 is preferably 30% or more, more preferably 50% or more, and even more preferably 70% or more. This sufficiently increases the density of catalytic active sites C in the catalyst structure 1. The coverage is the ratio of the area occupied by the roughened coating 3 to the total area of ​​the first surface 21.

[0040] The average thickness of the roughened coating 3 is not particularly limited, but is preferably 0.5 μm to 30.0 μm, more preferably 1.0 μm to 10.0 μm, and even more preferably 1.5 μm to 5.0 μm. If the average thickness of the roughened coating 3 is within the above range, the adhesion of the roughened coating 3 can be ensured, thereby achieving a catalyst structure 1 with excellent long-term reliability. Furthermore, a catalyst structure 1 with a sufficiently high density of catalytic active sites C can be achieved.

[0041] If the average thickness of the roughened coating 3 is below the lower limit, the adhesion of the roughened coating 3 may decrease and the density of catalytically active sites C may become insufficient. On the other hand, if the average thickness of the roughened coating 3 exceeds the upper limit, the effects of increasing the adhesion of the roughened coating 3 and the density of catalytically active sites C may plateau, and the roughened coating 3 may become more susceptible to peeling.

[0042] The average thickness of the roughened coating 3 is the average value of thicknesses measured at 10 or more randomly selected locations in an enlarged observation image of the cross section of the roughened coating 3.

[0043] 1.3. Granules A plurality of granules 4 are in contact with the roughened coating 3. The granules 4 are in a granular shape. This increases the contact efficiency between the raw material and catalytically active sites C formed at the interface between the granules 4 and the roughened coating 3, compared to when the granules 4 are present in layers rather than in granular form. As a result, a catalyst structure 1 with high reforming reaction efficiency can be achieved, even when the catalytically active sites C are present at a high density.

[0044] The shape of the granular materials 4 when the catalyst structure 1 is viewed in plan from the Z-axis direction is not particularly limited as long as it is granular, and may be a specific shape such as a circle or a polygon, or may be an irregular shape that is not a specific shape. Furthermore, the shapes of the granular materials 4 may be the same as each other or may be different from each other.

[0045] The granules 4 contain a second metal element and function as a carrier for supporting, for example, a catalyst. Specific examples of the second metal element include Pd, Pt, Rh, Ru, Ir, and Os. Of these, the second metal element is preferably Pd. These elements, including Pd, exert particularly high catalytic activity at the catalytic active sites C by contacting with the first metal element.

[0046] In particular, when the first metal element is Au and the second metal element is Pd, a particularly high catalytic activity can be obtained.

[0047] If necessary, elements other than the second metal element may be contained in the granules 4. That is, the second metal element may exist as a simple substance, or may exist as a compound or a mixture with other elements.

[0048] The granules 4 may be in contact with one another, but are preferably spaced apart as shown in Figure 1. This increases the contact efficiency between the catalytically active sites C formed at the interfaces between the granules 4 and the roughened coating 3 and the material to be modified, compared to when the granules 4 are in contact with one another.

[0049] The average particle diameter of the granules 4 is not particularly limited, but is preferably 1 nm or more and 100 nm or less, more preferably 2 nm or more and 50 nm or less, and even more preferably 3 nm or more and 20 nm or less. If the average particle diameter of the granules 4 is within the above range, the number density of the catalytic active sites C can be sufficiently increased and the difficulty of manufacturing the granules 4 can be reduced. This makes it possible to realize a catalyst structure 1 that has particularly high reforming reaction efficiency and is easy to manufacture.

[0050] If the average particle size of the granules 4 is below the lower limit, it may be difficult to manufacture the granules 4. On the other hand, if the average particle size of the granules 4 is above the upper limit, the granules 4 may be more likely to fall off, or the number density of the catalytic active sites C may decrease, resulting in a decrease in the efficiency of the reforming reaction.

[0051] The average particle diameter of the granular material 4 is the average value of the particle diameters (circle equivalent diameters) measured for 10 or more randomly selected particle images after identifying the particle images of the granular material 4 based on differences in contrast, etc., in an enlarged observation image of the surface of the catalyst structure 1.

[0052] 2.Method for manufacturing catalyst structure Next, a method for producing a catalyst structure according to an embodiment will be described, taking as an example a method for producing a catalyst structure 1 shown in FIG.

[0053] Fig. 3 is a process diagram illustrating a method for producing a catalyst structure according to an embodiment, and Figs. 4 to 7 are cross-sectional views illustrating a method for producing the catalyst structure 1 shown in Fig. 3.

[0054] The method for producing a catalyst structure shown in FIG. 3 is a method for producing a catalyst structure 1 used in a reforming reaction for reforming a substance, and includes a pretreatment step S102, a metal film formation step S104, a surface roughening step S106, and a granular body formation step S108.

[0055] 2.1.Pretreatment process In the pretreatment step S102, the substrate 2 shown in FIG. 4 is prepared, and the first surface 21 is pretreated. The pretreatment is performed prior to the metal film forming step S104. The pretreatment includes, for example, a cleaning process for cleaning the first surface 21 of the substrate 2, and a drying process for drying the first surface 21 after the cleaning process. By performing these pretreatments, dirt and foreign matter adhering to the first surface 21 are removed.

[0056] Examples of cleaning treatments include wet cleaning using a cleaning solution, and dry cleaning using plasma, ultraviolet light, or the like.

[0057] The cleaning liquid is selected appropriately depending on the constituent material of the substrate 2 and the substances to be removed, but examples include chemical solutions containing hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, hydrogen peroxide, ammonia, ozone, etc., and water such as ultrapure water, pure water, ion-exchanged water, and hydrogen water.

[0058] Examples of drying methods include spin drying, IPA drying, and Marangoni drying.

[0059] By carrying out these pretreatments, it is possible to clean the first surface 21. This improves the film-forming properties and adhesion of the metal film 30 to the first surface 21, which is formed in the metal film forming step S104.

[0060] 2.2.Metal film formation process In the metal film forming step S104, a metal film 30 shown in FIG.

[0061] The metal film 30 contains a first metal element and is a coating for forming the roughened coating 3. Examples of methods for forming the metal film 30 include vapor phase deposition methods such as vacuum deposition, sputtering, and CVD. Of these, sputtering is preferably used. Sputtering can provide a metal film 30 with high adhesive strength.

[0062] The pressure when forming the metal film 30 by sputtering is preferably 100 Pa or less, more preferably 0.001 Pa or more and 10 Pa or less, and even more preferably 0.001 Pa or more and 1 Pa or less. This makes it possible to particularly increase the coverage and density of the metal film 30. As a result, the catalytic active sites C can be particularly highly densified.

[0063] The distance between the sputtering target and the substrate 2 is not particularly limited, but is preferably 10 mm or more and 100 mm or less, and more preferably 20 mm or more and 50 mm or less. This can particularly increase the coverage and density of the metal film 30. As a result, the catalytic active sites C can be particularly highly densified.

[0064] The discharge method used when forming the metal film 30 by sputtering may be either an RF (radio frequency) method or a DC (direct current) method, with the DC method being preferred.

[0065] The thickness of the metal film 30 is not particularly limited as long as it is thicker than the thickness of the roughened coating 3 to be formed.

[0066] 2.3.Roughening process In the roughening step S106, the metal film 30 is irradiated with a pulsed laser PL to perform sublimation processing on the metal film 30. In addition, by moving the pulsed laser PL as shown in Fig. 6, it is possible to perform sublimation processing over a wide range. As a result, the concave-convex structure 31 shown in Fig. 6 is formed, and the roughened coating 3 shown in Fig. 7 is obtained.

[0067] Compared to a continuous wave (CW) laser, a pulsed laser PL can suppress the thermal effect on the metal film 30. This allows for precise control of the pitch and depth of the concave-convex structure 31. This allows for the concave-convex structure 31 to have the desired shape. As a result, a concave-convex structure 31 with a large specific surface area can be formed.

[0068] Pulsed laser PL is a laser generated by pulse oscillation. Known pulsed laser PL includes picosecond lasers, femtosecond lasers, and attosecond lasers, each with a different pulse width. Of these, femtosecond lasers are preferred for their accuracy in forming the concave-convex structure 31 and ease of handling. Femtosecond lasers are suitable for sublimation processing because they have a femtosecond pulse width and cause little thermal denaturation of the irradiated material. Furthermore, by using a femtosecond laser, concave-convex structures 31 with optimized pitch and depth can be formed in a shorter time, thereby easily increasing the processing speed of sublimation processing. Furthermore, because the processing is less likely to generate scattered material or debris, the pitch between adjacent concave-convex structures 31 can be sufficiently narrowed, which also allows the formation of concave-convex structures 31 with a large specific surface area.

[0069] Sublimation processing refers to laser processing that involves sublimation of the irradiated material, rather than melting the irradiated material. With pulsed lasers (PL), optimizing the pulse width ensures that all or part of the energy is used for sublimation, a non-thermal process, rather than being used for thermal vibration of the irradiated material. This enables processing with minimal generation of debris. Note that sublimation and melting of the irradiated material may occur simultaneously or with a time lag.

[0070] The pulse width of the pulsed laser PL is preferably shorter than the collision relaxation time of the first metal element. The collision relaxation time is the time at which the boundary between a thermal process and a non-thermal process occurs when the pulsed laser PL is irradiated onto an irradiated material. In other words, it can be said to be the time at which the boundary between melt processing and sublimation processing occurs. If the pulse width is shorter than the collision relaxation time, the proportion of sublimation processing in the processing mechanism increases. This makes it possible to particularly suppress the generation of scattered matter and debris associated with processing, and to form a concave-convex structure 31 with a particularly large specific surface area.

[0071] The collision relaxation time varies depending on the type of first metal element. FIG. 8 is a table showing the collision relaxation times of main first metal elements. As shown in FIG. 8, for example, when the first metal element is Au, the collision relaxation time is 25.3 picoseconds. Therefore, when the metal film 30 contains Au, it is preferable to set the pulse width of the pulse laser PL to less than 25.3 picoseconds.

[0072] The pulse width of the pulsed laser PL is preferably within a range based on the collision relaxation time described above, but is further optimized depending on the constituent material of the metal film 30, the wavelength of the pulsed laser PL, the spot size, etc. Specifically, the pulse width is preferably 1 fs or more and 1000 fs or less, and more preferably 100 fs or more and 800 fs or less.

[0073] If the pulse width is less than the lower limit, depending on other conditions, the generation of flying particles may be suppressed, but the processing speed of the sublimation process may decrease. Also, the height H of the concave-convex structure 31 may decrease. On the other hand, if the pulse width exceeds the upper limit, the pitch P of the concave-convex structure 31 may become narrower or wider, and the average pitch may deviate from the aforementioned range.

[0074] The wavelength of the pulsed laser PL is not particularly limited, but is preferably 10 nm to 800 nm, more preferably 200 nm to 700 nm, and even more preferably 400 nm to 600 nm. Pulsed laser PL with such a wavelength can lower the threshold value for the irradiation energy at which processing begins, thereby increasing the processing speed. This allows the catalyst structure 1 to be produced efficiently.

[0075] If the wavelength of the pulsed laser PL is below the lower limit, the pulsed laser PL may be difficult to handle, whereas if the wavelength of the pulsed laser PL is above the upper limit, the processing speed may decrease.

[0076] The repetition frequency of the pulsed laser PL mainly affects the processing speed and the generation of scattered particles, etc. The repetition frequency of the pulsed laser PL is preferably 1 kHz or more and 2 MHz or less, more preferably 50 kHz or more and 1 MHz or less, and even more preferably 100 kHz or more and 500 kHz or less. By setting the repetition frequency within the above range, it is possible to improve the processing speed while suppressing the generation of scattered particles, etc.

[0077] If the repetition frequency is lower than the lower limit, the processing speed may decrease. On the other hand, if the repetition frequency is higher than the upper limit, scattering may occur. In addition, the average pitch of the concave-convex structure 31 may become larger than the range, or the average height may become smaller.

[0078] The energy of one pulse of the pulsed laser PL is preferably 5 nJ to 5 mJ, more preferably 100 nJ to 100 μJ, and even more preferably 500 nJ to 5 μJ, which makes it possible to improve the processing speed while suppressing the generation of flying debris.

[0079] Fig. 9 is an example of an SEM (scanning electron microscope) image showing a concave-convex structure 31 formed on the surface of a metal film 30 using a pulsed laser PL. Fig. 10 is a partially enlarged view of the concave-convex structure 31 shown in Fig. 9. The pulsed laser PL used to form the concave-convex structure 31 shown in Figs. 9 and 10 had a pulse width of 300 fs, a wavelength of 515 nm, a repetition frequency of 200 kHz, and energy per pulse of 1 μJ. The metal film 30 is an Au sputtering film.

[0080] In Fig. 9, a pulsed laser PL is irradiated to one location on the surface of the metal film 30, forming a concave-convex structure 31 in a circular region. When a portion of the circular region in Fig. 9 is enlarged, it can be seen that a large number of concave portions 312 have been formed, and that convex portions 314 have been formed in the areas where the concave portions 312 are adjacent to each other, as shown in Fig. 10.

[0081] In the example shown in FIG. 10, the average pitch of the concave-convex structure 31 is about 0.5 μm, and the average height of the concave-convex structure 31 is about 0.1 μm.

[0082] 2.4. Granule formation process In the granule formation step S108, a plurality of granules 4 are formed in contact with the roughened coating 3. The granules 4 contain a second metal element and have an average particle diameter smaller than the average pitch of the uneven structure 31.

[0083] The method for forming the granules 4 is atomic layer deposition (ALD). Atomic layer deposition allows for efficient formation of minute granules 4 without the need for patterning or the like. Specifically, in atomic layer deposition, island-shaped nuclei are first formed on the surface of the concave-convex structure 31 of the roughened coating 3, and then the nuclei grow to form the granules 4. Therefore, by adjusting the film formation time according to the growth stage of the nuclei, the granules 4 can be efficiently formed.

[0084] Furthermore, atomic layer deposition allows for precise control of the amount of film formation at the atomic layer level, thereby enabling precise control of the particle size of the granules 4. Furthermore, atomic layer deposition allows the raw material gas and oxidant to flow into the recesses 312 and form a film therein, thereby enabling efficient formation of the granules 4 on the surfaces of the recesses 312. Therefore, atomic layer deposition allows for the manufacture of a catalyst structure 1 in which catalytic active sites C are formed at a particularly high density.

[0085] The raw material gas and oxidizing agent used in the atomic layer deposition method are appropriately selected depending on the constituent materials of the granules 4. The raw material gas is a gas containing a precursor of the constituent material. For example, when the second metal element contained in the granules 4 is Pd, examples of the precursor include palladium acetylacetone, palladium hexafluoroacetylacetonate, and palladium trifluoroacetylacetonate.

[0086] An example of a procedure for forming the granules 4 using atomic layer deposition is described below. First, the substrate 2 on which the roughened coating 3 is formed is placed in a chamber capable of evacuation and atmospheric control. Next, a raw material gas containing precursors is introduced into the chamber and allowed to adsorb to the roughened coating 3. Next, after evacuating excess precursors, an oxidizing agent is introduced into the chamber. Examples of oxidizing agents include ozone, plasma oxygen, and water vapor. The introduced oxidizing agent reacts with the precursors adsorbed to the roughened coating 3, forming the granules 4.

[0087] The temperature of the roughened coating 3 when forming the granules 4 by atomic layer deposition is preferably a temperature below the melting temperature of the roughened coating 3. This makes it possible to form fine granules 4 with a sufficiently high number density while preventing damage to the uneven structure 31.

[0088] The temperature of the roughened coating 3 when forming the granules 4 is set appropriately depending on the constituent materials of the roughened coating 3, the types of precursor and oxidizing agent, etc., but is preferably 100°C or higher and 350°C or lower, and more preferably 150°C or higher and 250°C or lower. This allows the precursor to react with high precision while suppressing the reduction or disappearance of the uneven structure 31. As a result, it is possible to form granules 4 that have a sufficiently high content of the desired constituent material, have particle diameters within the above-mentioned range, and can sufficiently increase the reaction efficiency of the reforming reaction.

[0089] Since the concave-convex structure 31 is a fine structure, its shape may change even when heated at a temperature lower than the melting point of the constituent material. Therefore, when the average pitch of the concave-convex structure 31 is within the above range, it is preferable to heat it within the above temperature range.

[0090] The pressure in the chamber when forming the granules 4 is preferably 100 Pa or less, more preferably 0.001 Pa or more and 10 Pa or less, and even more preferably 0.001 Pa or more and 1 Pa or less. This allows the concentrations of the precursor and oxidant to be optimized, thereby increasing the reaction efficiency of the precursor. As a result, it is possible to form granules 4 that have a sufficiently high content of the desired constituent material, a particle size within the above-mentioned range, and can sufficiently increase the reaction efficiency of the reforming reaction.

[0091] When the granules 4 are formed in the above manner, catalytic active points C shown in Fig. 2 are formed at the interfaces between the granules 4 and the roughened coating 3. In this way, the catalyst structure 1 shown in Fig. 2 is obtained.

[0092] 3. Effects of the embodiment As described above, the catalyst structure 1 according to the embodiment is a catalyst structure used in a reforming reaction to reform a substance, and comprises a substrate 2, a roughened coating 3, and a plurality of granules 4. The substrate 2 has a first surface 21 and a second surface 22 that are opposite each other. The roughened coating 3 is provided on the first surface 21 of the substrate 2, contains a first metal element, and has an uneven structure 31 with an average pitch of 0.1 μm or more and 5.0 μm or less. The granules 4 contain a second metal element, are in contact with the roughened coating 3, and have an average particle diameter smaller than the average pitch.

[0093] According to this configuration, the provision of the uneven structure 31 makes it possible to increase the specific surface area of ​​the roughened coating 3. This increases the area with which the granules 4 can come into contact, and increases the number of catalytically active sites C that can be formed per unit surface area of ​​the roughened coating 3. As a result, a catalyst structure 1 is obtained that can improve the efficiency of the reforming reaction. Furthermore, because the structure includes the substrate 2, a catalyst structure 1 that is easy to manufacture and handle is obtained. For example, by stacking (layering) multiple catalyst structures 1 with a specified gap between them and placing them in a container, a reformer can be constructed in which catalytically active sites C are three-dimensionally accumulated. Such a reformer can achieve high reforming efficiency even in a small space.

[0094] In the catalyst structure 1 according to the embodiment, the substrate 2 contains silicon. According to this configuration, the catalyst structure 1 can be obtained, which has the advantages that the silicon-containing substrate 2 is distributed as a silicon wafer, has stable quality, is easily available, etc. Furthermore, for silicon-containing materials, precision processing technology by etching is established, so that the material is suitable as a constituent material of the substrate 2.

[0095] In the catalyst structure 1 according to the embodiment, the first metal element is Au, and the second metal element is Pd. With this configuration, a catalyst structure 1 having particularly high catalytic activity can be obtained.

[0096] In the catalyst structure 1 according to the embodiment, the average thickness of the roughened coating 3 is 0.5 μm or more and 30.0 μm or less.

[0097] This configuration ensures adhesion of the roughened coating 3, thereby realizing a catalyst structure 1 with excellent long-term reliability. It also makes it possible to realize a catalyst structure 1 with a sufficiently high density of catalytic active sites C.

[0098] In the catalyst structure 1 according to the embodiment, the average height of the concave-convex structure 31 is 0.05 μm or more and 10.0 μm or less.

[0099] With this configuration, the surface area of ​​the roughened coating 3 can be made sufficiently large, and the uneven structure 31 can be formed relatively easily.

[0100] In the catalyst structure 1 according to the embodiment, the average particle size of the granules 4 is 1 nm or more and 100 nm or less.

[0101] According to this configuration, it is possible to sufficiently increase the number density of the catalytic active sites C and reduce the difficulty of manufacturing the granules 4. This makes it possible to realize a catalyst structure 1 that has particularly high efficiency in the reforming reaction and is easy to manufacture.

[0102] The method for producing a catalyst structure according to the embodiment is a method for producing a catalyst structure 1 used in a reforming reaction to reform a substance, and includes a metal film forming step S104, a surface roughening step S106, and a granule forming step S108. In the metal film forming step S104, a metal film 30 containing a first metal element is formed on the first surface 21 of a substrate 2 having a first surface 21 and a second surface 22 that are opposite each other. In the surface roughening step S106, a pulsed laser PL is irradiated onto the metal film 30 to perform sublimation processing, thereby obtaining a roughened coating 3 having a concave-convex structure 31. In the granule forming step S108, a plurality of granules 4 are formed by atomic layer deposition in contact with the roughened coating 3, containing a second metal element, and having an average particle diameter smaller than the average pitch of the concave-convex structure 31.

[0103] According to this configuration, it is possible to manufacture a catalyst structure 1 that is easy to manufacture and handle and has a large specific surface area. In particular, sublimation processing using a pulsed laser PL suppresses the generation of debris and the like that accompanies processing, and the pitch between adjacent uneven structures 31 can be sufficiently narrowed, making it possible to form an uneven structure 31 with a large specific surface area. Furthermore, according to the atomic layer deposition method, it is possible to manufacture a catalyst structure 1 in which catalytic active sites C are formed at an especially high density.

[0104] The method for producing a catalyst structure according to the embodiment includes a pretreatment step S102. In the pretreatment step S102, a cleaning treatment is performed to clean the first surface 21 of the substrate 2, and a drying treatment is performed to dry the first surface 21 after the cleaning treatment. With this configuration, dirt and foreign matter adhering to the first surface 21 can be removed.

[0105] In the method for producing a catalyst structure according to the embodiment, the particles 4 are formed by atomic layer deposition while the roughened coating 3 is heated at a temperature below the melting point.

[0106] According to this configuration, it is possible to form fine granules 4 having a sufficiently high number density while preventing damage to the uneven structure 31.

[0107] In the method for producing a catalyst structure according to the embodiment, the pulse width of the pulsed laser PL is less than the collision relaxation time of the first metal element.

[0108] With this configuration, the proportion of sublimation processing in the processing mechanism increases, which makes it possible to particularly suppress the generation of scattering matter and debris that accompanies processing, and to form a concave-convex structure 31 with an especially large specific surface area.

[0109] Although the catalyst structure and the method for manufacturing the catalyst structure of the present invention have been described above based on preferred embodiments, the present invention is not limited thereto. For example, the catalyst structure of the present invention may be one in which each part of the embodiment is replaced with any component having the same function, or one in which any component is added to the embodiment.

[0110] Furthermore, the method for producing a catalyst structure of the present invention may be such that any step for any purpose is added to the above-described embodiment. [Explanation of symbols]

[0111] 1...catalyst structure, 2...substrate, 3...roughened coating, 4...granules, 21...first surface, 22...second surface, 30...metal film, 31...uneven structure, 312...concave portion, 314...protrusion portion, C...catalytic active site, H...height, P...pitch, PL...pulse laser, S102...pretreatment step, S104...metal film formation step, S106...roughening step, S108...granule formation step

Claims

1. A catalyst structure for use in a reforming reaction for reforming a substance, comprising: a substrate having a first surface and a second surface which are opposite surfaces to each other; a roughened coating film provided on the first surface of the substrate, the roughened coating film containing a first metal element and having an uneven structure with an average pitch of 0.1 μm or more and 5.0 μm or less; a plurality of granules containing a second metal element, in contact with the roughened coating, and having an average particle diameter smaller than the average pitch; A catalyst structure comprising:

2. The catalytic structure of claim 1 wherein the substrate comprises silicon.

3. the first metal element is Au, 3. The catalyst structure according to claim 1, wherein the second metal element is Pd.

4. 3. The catalyst structure according to claim 1, wherein the roughened coating has an average thickness of 0.5 μm or more and 30.0 μm or less.

5. 3. The catalyst structure according to claim 1, wherein the average height of the uneven structure is 0.05 μm or more and 10.0 μm or less.

6. 3. The catalyst structure according to claim 1, wherein the average particle size of the particulate material is 1 nm or more and 100 nm or less.

7. 1. A method for producing a catalyst structure for use in a reforming reaction to reform a substance, comprising: a metal film forming step of forming a metal film containing a first metal element on a first surface of a substrate having a first surface and a second surface that are reverse to each other; a roughening step of irradiating the metal film with a pulsed laser to perform sublimation processing to obtain a roughened coating having an uneven structure; a granule forming step of forming, by atomic layer deposition, a plurality of granules in contact with the roughened coating, containing a second metal element, and having an average particle diameter smaller than the average pitch of the uneven structure; A method for producing a catalyst structure, comprising:

8. The method for producing a catalyst structure according to claim 7 , further comprising a pre-treatment step of performing a cleaning treatment for cleaning the first surface of the substrate and a drying treatment for drying the first surface after the cleaning treatment.

9. 9. The method for producing a catalyst structure according to claim 7, wherein the granules are formed while the roughened coating is heated at a temperature lower than the melting point in the atomic layer deposition method.

10. 9. The method for producing a catalyst structure according to claim 7, wherein the pulse width of the pulsed laser is shorter than the collision relaxation time of the first metal element.

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