Porous metal catalyst and preparation method therefor

Abstract

The present invention provides a method for preparing a porous metal catalyst, comprising: providing a microporous substrate, a second metal, and a filler; mixing the second metal with the filler to form a mixture; placing the microporous substrate into an alloying device, the microporous substrate being in the shape of a mesh, a foam, or a felt; covering a surface of the microporous substrate with the mixture; once the surface of the microporous substrate has been covered with the mixture, annealing the microporous substrate and the second metal to form an alloy layer on the surface of the microporous substrate; and placing the microporous substrate with the alloy layer formed on the surface into a vacuum heat treatment device to perform vacuum heat treatment so as to form the porous metal catalyst. The technical solution provided by the present invention improves catalytic activity while ensuring the mechanical strength of the porous metal catalyst.

Description

Porous metal catalysts and their preparation methods Technical Field

[0001] This invention relates to the field of electrode materials, and more particularly to a porous metal catalyst and a method for preparing the porous metal catalyst. Background Technology

[0002] Compared with traditional micro- and nanoparticles and bulk materials, micro- and nanoporous metals have many superior physicochemical properties, which mainly come from the unique structural features of micro- and nanoporous metals, such as high porosity, large specific surface area, high electrical conductivity, and tunable composition, structure, and size. Therefore, the development of novel micro- and nanoporous metals has always attracted widespread attention.

[0003] Hydrogen energy, as a clean and efficient secondary energy source, boasts advantages such as high energy density (140 MJ / kg), multiple production methods, storability, transportability, and wide applicability. Furthermore, as an energy interconnection medium, hydrogen energy can be first produced from renewable energy sources, then stored on a large scale for peak shaving, and finally recycled through water to achieve a closed loop of clean, pollution-free, and highly efficient energy storage / release, providing a feasible path for deep decarbonization in transportation, industry, and construction sectors.

[0004] Among various hydrogen production processes, using renewable energy for water electrolysis is widely recognized as the optimal approach. The catalytic electrode, as one of the most crucial components in water electrolysis, is typically found in the form of metal mesh, metal foam, or metal felt. Currently, the mainstream catalytic electrode preparation processes are spraying and electroplating, but both generally suffer from high overpotentials or poor durability during hydrogen evolution reaction, primarily due to a limited number of catalytically active sites and the ease with which the coating / plating layer can detach. In recent years, micro- and nano-porous metals prepared via the dealloying method have demonstrated excellent performance as catalytic electrodes or substrate materials in water electrolysis, thanks to their large specific surface area and self-supporting properties.

[0005] However, micro / nano porous metal catalytic electrodes still face many challenges in practical water electrolysis applications. For example, the methods for preparing porous metal precursors are typically smelting-spinning or smelting-pressure processing. The precursors obtained by these methods, and the micro / nano porous metals subsequently prepared through dealloying, generally fail to meet the morphological requirements of the catalytic electrode in the electrolyzer (network, foam, or felt-like). Furthermore, because micro / nano porous metals are composed entirely of micro / nano-scale porous structures without a solid matrix support, their overall mechanical properties are poor, making them prone to structural collapse or decomposition during hydrolysis. Moreover, most dealloying processes for preparing micro / nano porous metal catalytic electrodes suffer from numerous problems, including difficulty in scaling up production, long processing times, high costs, the need for highly corrosive liquids during production, and potential environmental pollution.

[0006] To address the aforementioned problems, the inventors of this application have proposed a porous metal catalyst and a method for preparing the porous metal catalyst. Summary of the Invention

[0007] This invention provides a porous metal catalyst and a method for preparing the porous metal catalyst, in order to solve the problems of poor mechanical properties and insufficient catalytic efficiency of porous catalytic electrodes.

[0008] According to a first aspect of the present invention, a method for preparing a porous metal catalyst is provided, comprising:

[0009] Provides a micron-porous substrate, a second metal, and a filler;

[0010] The second metal and the filler are mixed to form a mixture;

[0011] The micron-porous substrate is placed in an alloying device, and the shape of the micron-porous substrate is: mesh, foam, or felt.

[0012] The mixture is applied to the surface of the microporous substrate;

[0013] After the mixture is applied to the surface of the microporous substrate, the microporous substrate and the second metal are annealed to form an alloy layer on the surface of the microporous substrate.

[0014] A micron-sized porous substrate with the alloy layer formed on its surface is placed in a vacuum heat treatment device for vacuum heat treatment to form a porous metal catalyst.

[0015] Optionally, during annealing, the alloying temperature is 300℃~500℃, and the holding time is 0.5h~5h.

[0016] Optionally, the thickness of the alloy layer is 10μm to 100μm.

[0017] Optionally, the vacuum heat treatment conditions are: gas pressure below 50 Pa, temperature range of 450℃~850℃, and heat preservation time of 0.5h~3.5h.

[0018] Optionally, the ligament size in the porous metal catalyst ranges from 100 nm to 2.5 μm.

[0019] Optionally, the filler may include alumina or silica sand.

[0020] Optionally, the second metal and the filler are in powder form.

[0021] Optionally, when the microporous substrate is mesh or foam, the mesh size of the microporous substrate is 10 to 110 mesh; when the microporous substrate is felt, the filament diameter of the microporous substrate is 3 μm to 100 μm.

[0022] Optionally, the particle size of the second metal is 120 mesh to 325 mesh, and the particle size of the filler is 40 mesh to 325 mesh.

[0023] Optionally, the mass ratio of the second metal to the filler is 1:1 to 1:3.

[0024] Optionally, the alloying equipment includes a box furnace or a tube furnace.

[0025] Optionally, during annealing, a protective gas is introduced into the alloy lamination equipment for 15 to 30 minutes before heating is started. The protective gas is argon or nitrogen.

[0026] Optionally, the microporous substrate includes a first characteristic metal, and after an alloy layer is formed on the surface of the microporous substrate, the method further includes:

[0027] A micron-sized porous substrate with an alloy layer on its surface is etched in an acidic solution to obtain a metal catalyst with tertiary porous characteristics.

[0028] Optionally, the first characteristic metal includes two or more micron-porous substrate elements, and at least one of the two or more micron-porous substrate elements is Mn or Al.

[0029] Optionally, the acidic solution is ammonium sulfate.

[0030] Optionally, the concentration of the ammonium sulfate is greater than or equal to 0.5M.

[0031] Optionally, the alloy layer includes a first metal element and a second metal element, wherein the first metal element includes at least one of Ni, Fe, Cu, Co, Mn, Ti, Cr, Mo, W, Ta, Au, Ag, Nb, Zr, and V; and the second metal element includes any one of Zn, Mg, Bi, and Cd.

[0032] According to a second aspect of the present invention, a method for preparing an electrode catalytic component is provided, comprising the method for preparing a porous metal catalyst as described in any one of the first aspects of the present invention.

[0033] According to a third aspect of the present invention, a porous metal catalyst is provided, comprising:

[0034] The micron-porous substrate has an alloy layer formed by the first metal element and the second metal on its surface, the alloy layer further includes a filler, and the alloy layer has micro-nano pores.

[0035] Optionally, in the alloy layer, the molar percentage of the first metal element is 20%-50%; and the molar percentage of the second metal element is 50%-80%.

[0036] Optionally, the alloy layer may also include nanoscale pores.

[0037] Optionally, the specific surface area of ​​the porous metal catalyst is 75–95 m². 2 / g.

[0038] Optionally, the pore size of the micro-sized pores in the micro-porous substrate is 5μm to 500μm, the ligament size of the micro-nano pores is 0.1μm to 10μm, and the ligament size of the nano-sized pores is 10nm to 99nm.

[0039] According to a fourth aspect of the present invention, a catalytic electrode assembly is provided, comprising the porous metal catalyst described in the third aspect of the present invention.

[0040] According to a fifth aspect of the present invention, an application of a catalytic electrode assembly as described in the fourth aspect of the present invention in hydrogen production by water splitting is provided.

[0041] Optionally, the catalytic electrode assembly exhibits catalytic activity for the oxygen evolution reaction.

[0042] Optionally, the catalytic electrode assembly exhibits catalytic activity for the hydrogen evolution reaction.

[0043] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0044] This invention provides a method for preparing a porous metal catalyst. The method involves coating a micron-sized porous substrate with a uniformly mixed second metal and a filler. The micron-sized porous substrate and the second metal are then annealed in an alloying layering apparatus to form an alloy layer on the surface of the micron-sized porous substrate. The micron-sized porous substrate with the alloy layer on its surface is then placed in a vacuum heat treatment apparatus for vacuum heat treatment. The porous metal catalytic electrode prepared by this method exhibits a porous structure only in the surface alloy layer, achieving improved activity of the porous metal catalyst while maintaining the mechanical strength of the formed porous metal catalyst within the micron-sized porous substrate. The technical solution provided by this invention eliminates the need for subsequent processing and shaping. Compared to vapor-phase alloying layering, the technical solution provided by this invention requires less time and is more efficient in preparing an alloy layer of the same thickness. Furthermore, the preparation method described in this invention does not require various chemical reagents such as acids, alkalis, and salts, and the sublimated metal vapor during vacuum heat treatment can be recovered and reused after treatment using a condenser. Therefore, the experimental scheme provided by this invention has a smaller environmental impact, lower production costs, and is easier to scale up for production. The technical solution provided by this invention can also control the thickness of the alloy layer and the size of the ligament. Specifically, the thickness of the alloy layer can be controlled by changing the time and temperature of surface alloying, and the size of the porous ligament can be controlled by controlling the temperature, duration and vacuum degree of vacuum heat treatment.

[0045] Furthermore, after forming an alloy layer on the surface of a micron-sized porous substrate, the present invention further forms nano-sized pores on the surface of the micro-nano-sized porous alloy layer by immersing the micron-sized porous substrate containing the first characteristic metal in an acidic solution for corrosion. This results in the formation of a tertiary porous catalyst structure on the micron-sized porous substrate, which greatly increases the specific surface area of ​​the porous metal catalyst, improves the catalytic activity, and ensures the mechanical strength of the porous metal catalyst.

[0046] This invention also provides a porous metal catalyst in which a micro- and nano-porous alloy layer is formed on the surface of a micron-porous substrate, thereby improving the activity of the porous metal catalyst. The micron-porous substrate ensures the mechanical strength of the porous metal catalyst. Therefore, the technical solution provided by this invention improves the catalytic activity of the porous metal catalyst while also ensuring the mechanical strength of the porous metal catalyst structure.

[0047] Furthermore, the porous metal catalyst provided by the present invention also includes nanoscale pores, forming a tertiary porous catalyst structure with the microscale pores in the microscale porous substrate and the micro-nanoscale pores in the alloy layer, thereby increasing the specific surface area of ​​the porous metal catalyst and greatly improving its catalytic activity. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 is a schematic flowchart of a method for preparing a porous metal catalyst according to an embodiment of the present invention;

[0050] Figure 2 is a cross-sectional scanning electron microscope image and an EDS elemental distribution diagram of a single wire after the surface alloying of Ni mesh and Zn powder in Embodiment 1 of the present invention.

[0051] Figure 3 is a scanning electron microscope image of the micro-nano porous metal Ni mesh obtained after vacuum heat treatment in Embodiment 1 of the present invention (the inset is a partial magnified view);

[0052] Figure 4 is the XRD diffraction pattern of the micro-nano porous metal Ni mesh obtained after vacuum heat treatment in Example 1 of the present invention.

[0053] Figure 5 is a linear scan diagram of the hydrogen evolution reaction on the surface of the micro-nano porous metal Ni mesh in Example 1 of the present invention;

[0054] Figure 6 is a linear scan diagram of the oxygen evolution reaction on the surface of the micro-nano porous metal Ni mesh in Example 1 of the present invention;

[0055] Figure 7 is a scanning electron microscope image of the micro-nano porous metal Ni felt obtained after vacuum heat treatment in Example 2 of the present invention (the inset is a partial magnified view);

[0056] Figure 8 is a scanning electron microscope image of the micro-nano porous Ni-Cu alloy layer obtained after vacuum heat treatment in Example 3 of the present invention (the inset is a partial magnified view);

[0057] Figure 9 is the XRD diffraction pattern of the micro-nano porous Ni-Cu alloy layer obtained after vacuum heat treatment in Example 3 of the present invention.

[0058] Figure 10 is a scanning electron microscope image of the micro-nano porous Ni-Mo-Cr-Fe alloy layer obtained after vacuum heat treatment in Example 4 of the present invention (the inset is a partial magnified view);

[0059] Figure 11 is the XRD diffraction pattern of the micro-nano porous Ni-Mo-Cr-Fe alloy layer obtained after vacuum heat treatment in Example 4 of the present invention.

[0060] Figure 12 is a scanning electron microscope image of the micro-nano porous Ni-Fe-Cr alloy layer obtained after vacuum heat treatment in Example 5 of the present invention (the inset is a partial magnified view);

[0061] Figure 13 is a transmission electron lattice contrast image of the metal catalyst with tertiary porous characteristics obtained after vacuum heat treatment and free corrosion in Example 6 of the present invention.

[0062] Figure 14 is a scanning electron microscope image of a nickel mesh with Raney nickel sprayed on its surface, as shown in Comparative Example 1 of the present invention (the inset is a partial enlarged view).

[0063] Figure 15 is a linear scan diagram of the hydrogen evolution reaction on the surface of the nickel mesh coated with Raney nickel in Comparative Example 1 of the present invention. Detailed Implementation

[0064] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0066] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0067] Figure 1 is a schematic flowchart of a method for preparing a porous metal catalyst provided by the present invention.

[0068] Please refer to Figure 1. According to an embodiment of the present invention, a method for preparing a porous metal catalyst is provided, comprising:

[0069] S11: Provides a micron-porous substrate, a second metal, and a filler;

[0070] S12: Mix the second metal and the filler to form a mixture;

[0071] S13: Place the micron-porous substrate into an alloying device. The shape of the micron-porous substrate is: mesh, foam, or felt.

[0072] S14: Cover the surface of the microporous substrate with the mixture;

[0073] S15: After covering the surface of the microporous substrate with the mixture, the microporous substrate and the second metal are annealed to form an alloy layer on the surface of the microporous substrate;

[0074] S16: The micron-sized porous substrate with the alloy layer formed on its surface is placed in a vacuum heat treatment device for vacuum heat treatment to form a porous metal catalyst.

[0075] This invention provides a method for preparing a porous metal catalyst. The method involves coating a micron-sized porous substrate with a uniformly mixed second metal and a filler. The micron-sized porous substrate and the second metal are then annealed in an alloying layering apparatus to form an alloy layer on the surface of the micron-sized porous substrate. The micron-sized porous substrate with the alloy layer on its surface is then placed in a vacuum heat treatment apparatus for vacuum heat treatment. The porous metal catalytic electrode prepared by this method exhibits a porous structure only in the surface alloy layer, thus improving the activity of the porous metal catalyst while maintaining the mechanical strength of the formed porous metal catalyst on the micron-sized porous substrate. The technical solution provided by this invention eliminates the need for subsequent processing and shaping. Compared to vapor-phase alloying layering, it requires less time and is more efficient in preparing an alloy layer of the same thickness.

[0076] The micron-porous substrate is placed in an alloying layering device, and a uniformly mixed second metal and filler are applied to the surface of the micron-porous substrate. The micron-porous substrate is in the shape of a mesh, foam, or felt, and serves as the base metal.

[0077] Micron-sized porous substrates can be a mixture of metals or a single metal.

[0078] In one embodiment, the microporous substrate includes at least one of Ni, Fe, Cu, Co, Mn, Ti, Cr, Mo, W, Ta, Au, Ag, Nb, Zr, and V; the second metal includes any one of Zn, Mg, Bi, and Cd.

[0079] Micron-sized porous substrates provide mechanical support for porous metal catalysts, resulting in high mechanical strength in the final prepared porous metal catalysts. Furthermore, porous metal catalysts formed on micron-sized porous substrates composed of multiple metals exhibit lattice distortion due to differences in the atomic volumes of different alloying elements, thereby enhancing activity. Simultaneously, the different alloying elements form a more structurally stable phase, thus improving electrochemical stability. Therefore, porous metal catalysts formed on micron-sized porous substrates composed of multiple metals can exhibit improved catalyst activity or stability due to the alloying layering effect.

[0080] In one embodiment, the filler includes alumina or quartz sand.

[0081] In one embodiment, the second metal and the filler are in powder form.

[0082] In one embodiment, when the microporous substrate is mesh or foam, the mesh size of the microporous substrate is 10 to 110 mesh; when the microporous substrate is felt, the filament diameter ranges from 3 μm to 100 μm.

[0083] Mesh, foam, or felt-like microporous substrates are used to increase the specific surface area of ​​porous metal catalysts. When the mesh size of the microporous substrate is 10 to 110 mesh, it can ensure the specific surface area while avoiding problems such as poor electrolyte flow or difficulty in detaching generated bubbles during water electrolysis.

[0084] In one embodiment, the particle size of the second metal is 120-325 mesh, and the particle size of the filler is 40-325 mesh.

[0085] The second metal or filler is set within the aforementioned particle size range, primarily based on considerations of alloy layering uniformity. When the particles of the second metal or filler are too large, it will lead to incomplete contact between the powder and metal A, thus affecting the alloy layering effect; while excessively high powder mesh size does not significantly improve the alloy layering effect, but significantly increases the price.

[0086] In one embodiment, the mass ratio of the second metal to the filler is 1:1 to 1:3. The filler is used to bond the second metal to the microporous substrate.

[0087] The micron-porous substrate and the second metal are annealed to form an alloy layer on the surface of the micron-porous substrate.

[0088] Annealing is used to form an alloy layer on the surface of a micron-porous substrate through solid thermal diffusion.

[0089] After the alloy layer is formed, the cooled microporous substrate is separated from the mixed powder of the second metal and filler, and the residual powder of the second metal and filler on the surface of the microporous substrate is cleaned.

[0090] In one embodiment, there is a difference in saturated vapor pressure between the first metal element and the second metal element, which allows the second metal element to sublimate partially or completely from the alloy layer, thereby achieving a dealloying process and forming a micro-nano scale porous structure.

[0091] In one embodiment, the alloy layer includes a first metal element and a second metal element. The first metal element includes at least one of Ni, Fe, Cu, Co, Mn, Ti, Cr, Mo, W, Ta, Au, Ag, Nb, Zr, and V. The second metal element includes any one of Zn, Mg, Bi, and Cd.

[0092] The raw materials and equipment involved in this invention are all commercially available.

[0093] In one embodiment, the alloying equipment includes a box furnace or a tube furnace.

[0094] In one embodiment, during the annealing process, a protective gas is introduced into the alloy lamination equipment for 15 to 30 minutes before heating is started. The protective gas is either argon or nitrogen. To prevent residual oxygen in the furnace chamber from oxidizing the workpiece, heating is started only after the protective gas has been introduced for 15 to 30 minutes.

[0095] In one embodiment, during annealing, the alloy layering temperature is 300–500°C, and the holding time is 0.5–5 h.

[0096] In one embodiment, the thickness of the alloy layer is 10–100 μm.

[0097] The thickness of the alloy layer can be controlled by adjusting the alloying temperature and holding time. To ensure the catalytic activity of the final porous catalyst, the alloying temperature is controlled to be no less than 300℃, the holding time no less than 0.5h, and the alloy layer thickness no less than 10μm. Meanwhile, to avoid cracking and detachment of the alloy layer, the alloying temperature is controlled to be no higher than 500℃, the holding time no less than 5h, and the alloy layer thickness no less than 100μm.

[0098] A micron-sized porous substrate with an alloy layer on its surface is placed in a vacuum heat treatment device for vacuum heat treatment to form a porous metal catalyst.

[0099] The second metal element in the alloy layer will partially or completely sublimate out of the alloy layer due to the difference in saturated vapor pressure between the first metal element and the second metal element. The remaining elements in the alloy layer will self-assemble to form a micro-nano scale porous structure, thereby obtaining a porous metal catalyst with a specific shape of the micron porous substrate itself and a surface with a micro-nano porous layer formed by vacuum heat treatment to achieve de-alloying.

[0100] In one embodiment, the vacuum heat treatment conditions are: gas pressure below 50 Pa, temperature range of 450℃~850℃, and heat preservation time of 0.5h~3.5h.

[0101] In one embodiment, the ligament size in the porous metal catalyst ranges from 100 nm to 2.5 μm.

[0102] The ligament size of micro / nano porous structures can be controlled by changing the temperature, duration, and vacuum level of vacuum heat treatment. Holding times below 0.5 hours are insufficient to form porous structures and guarantee catalytic activity; holding times above 3.5 hours result in significant coarsening of the porous structure, reducing the specific surface area of ​​the porous metal catalyst and thus decreasing catalytic activity. The preparation of porous catalysts with ligament sizes below 100 nm is very difficult and difficult to achieve; when the ligament size exceeds 2.5 μm, the specific surface area decreases, leading to reduced catalytic activity.

[0103] In one embodiment, the microporous substrate includes a first characteristic metal, and after an alloy layer is formed on the surface of the microporous substrate, the method further includes:

[0104] A micron-sized porous substrate with an alloy layer on its surface is etched in an acidic solution to obtain a metal catalyst with tertiary porous characteristics.

[0105] A micron-sized porous substrate with an alloy layer formed on its surface is etched in an acidic solution to further increase the specific surface area of ​​the porous metal catalyst, improve its catalytic activity, and at the same time ensure the mechanical strength of the porous metal catalyst.

[0106] In one embodiment, the first feature metal comprises two or more micron-porous substrate elements, and at least one of the two or more micron-porous substrate elements is Mn.

[0107] In one embodiment, the acidic solution is ammonium sulfate.

[0108] In one embodiment, the concentration of ammonium sulfate is greater than or equal to 0.5 M. This is because if the concentration of ammonium sulfate is lower than 0.5 M, the reaction rate will be too slow. Experiments have verified that the reaction rate is more suitable when the concentration of ammonium sulfate is between 0.5 M and 2 M.

[0109] In summary, the present invention provides a method for preparing a porous metal catalyst. This method involves forming an alloy layer on the surface of a micron-sized porous substrate and then creating pores within the alloy layer through vacuum heat treatment. The porous metal catalytic electrode prepared by this method has a porous structure only in the surface alloy layer, without damaging the original shape of the micron-sized porous substrate, thus eliminating the need for subsequent processing. Compared to vapor-phase alloy layering, this method requires less time and is more efficient in preparing an alloy layer of the same thickness. It also improves the activity of the porous metal catalyst while maintaining the mechanical strength of the porous metal catalyst structure.

[0110] The technical solution provided by this invention can also control the thickness of the alloy layer by changing the time and temperature of surface alloying, and control the ligament size of the porous structure by controlling the temperature, duration and vacuum degree of vacuum heat treatment.

[0111] In addition, the preparation method described in this invention does not require the use of various chemical reagents such as acids, alkalis and salts, and the sublimated metal vapor during the vacuum heat treatment process can be recovered by a condensation device and reused after treatment. Therefore, it has less impact on the environment, lower production costs, and is easier to scale up.

[0112] According to an embodiment of the present invention, a porous metal catalyst is provided, comprising:

[0113] The micron-porous substrate has an alloy layer formed by the first metal element and the second metal on its surface, the alloy layer further includes a filler, and the alloy layer has micro-nano pores.

[0114] In one embodiment, the alloy layer contains a first metal element with a molar percentage of 20%-50% and a second metal element with a molar percentage of 50%-80%.

[0115] This invention provides a porous metal catalyst by forming a micro / nano porous alloy layer on the surface of a micron-porous substrate, thereby improving the activity of the porous metal catalyst. The micron-porous substrate ensures the mechanical strength of the porous metal catalyst. Therefore, the technical solution provided by this invention improves the catalytic activity of the porous metal catalyst while also ensuring the mechanical strength of the porous metal catalyst structure.

[0116] In one embodiment, the alloy layer further includes nanoscale pores.

[0117] The porous metal catalyst has a specific surface area of ​​75–95 m². 2 / g.

[0118] The nanoscale pores, together with the microscale pores in the microscale porous substrate and the micro-nanoscale pores in the alloy layer, form a tertiary porous catalyst structure, which increases the specific surface area of ​​the porous metal catalyst and greatly improves its catalytic activity.

[0119] In one embodiment, the pore size of the micro-sized pores in the micro-porous substrate is 5μm to 500μm, the ligament size of the micro-nano pores is 0.1μm to 10μm, and the ligament size of the nano-sized pores is 10nm to 99nm.

[0120] It is evident that the technical solution provided by this invention enhances catalytic activity while ensuring the mechanical strength of porous metal catalysts.

[0121] According to an embodiment of the present invention, a method for preparing an electrode catalytic component is provided, including the method for preparing a porous metal catalyst as described in any of the foregoing embodiments of the present invention.

[0122] According to one embodiment of the present invention, a catalytic electrode assembly is also provided, comprising the porous metal catalyst described in the foregoing embodiments of the present invention.

[0123] According to one embodiment of the present invention, an application of the catalytic electrode assembly as described in the foregoing embodiments of the present invention in hydrogen production by water splitting is provided.

[0124] The catalytic electrode assembly can be directly applied to the water electrolysis hydrogen production process, and when the catalytic electrode assembly is used as a cathode, it exhibits catalytic activity for the hydrogen evolution reaction and has excellent hydrogen evolution performance and stability.

[0125] In addition, the catalytic electrode assembly can also be used as an anode in the water electrolysis hydrogen production process. In this case, the catalytic electrode assembly exhibits catalytic activity for the oxygen evolution reaction and has excellent oxygen evolution performance and stability.

[0126] In one embodiment, when the porous metal catalyst is used in the water electrolysis process, the surface hydrogen evolution overpotential is as low as 80–140 mV.

[0127] The preparation method and performance of a porous metal catalyst provided by the present invention will be described in detail below with reference to specific embodiments and Figures 2-8:

[0128] Example 1

[0129] The method for preparing porous metal catalysts provided in this embodiment includes:

[0130] 1) Cut a metal Ni mesh as a micron porous substrate with a mesh size of 50 mesh; select metal Zn as the alloying layering element, which is in powder form with a particle size of 325 mesh; select alumina (Al2O3) as the filler, which is in powder form with a particle size of 325 mesh.

[0131] 2) First, place the Ni mesh into the tube furnace, then mix Zn powder and Al2O3 powder evenly in a mass ratio of 1:1 and cover the surface of the Ni mesh, ensuring that the surface of the Ni mesh is not exposed.

[0132] 3) Argon was selected as the protective gas. After argon was continuously introduced for 30 minutes, the Ni mesh covered with mixed powder was heated in the tube furnace to a temperature of 500℃ and held for 0.5 hours.

[0133] Figure 2 is a cross-sectional scanning electron microscope image of a single wire after the surface alloying of Ni mesh and Zn powder in Embodiment 1 of the present invention, and an EDS elemental distribution map of Ni and Zn.

[0134] Please refer to Figure 2. Zn and Ni will form a Ni-Zn alloy layer on the surface of the Ni mesh through solid thermal diffusion, with a thickness of approximately 80 μm.

[0135] After the surface alloying is completed, the cooled Ni mesh is separated from the mixed powder and the residual powder on the surface is cleaned.

[0136] The cleaned Ni mesh was placed in a vacuum heat treatment furnace and heated at a pressure of 50 Pa and a temperature of 450 °C for 3 hours.

[0137] Figure 3 is a scanning electron microscope image of the micro-nano porous metal Ni mesh obtained after vacuum heat treatment in Example 1 of the present invention (the inset is a partial magnified view), and Figure 4 is its XRD diffraction pattern.

[0138] Please refer to Figures 3 and 4. After vacuum heat treatment, a porous structure is formed on the surface of the Ni mesh, with a ligament size of 300-500 nm and an elemental composition of 92 at.% Ni and 8 at.% Zn.

[0139] Figure 5 is a linear scan diagram of the hydrogen evolution reaction on the surface of the micro-nano porous metal Ni mesh in Example 1 of the present invention.

[0140] Please refer to Figure 5. When this micro / nano porous Ni metal mesh is used as a catalytic electrode for water electrolysis, a linear scan of the hydrogen evolution reaction on the surface of the micro / nano porous Ni metal mesh is obtained. In the figure, the potential relative to the reversible hydrogen electrode is plotted on the x-axis (in V), and the current density is plotted on the y-axis (in mA / cm²). 2 As shown in Figure 5, when the potential at 10 mA / cm2 is taken as the hydrogen evolution overpotential of the cathode catalytic electrode assembly, the surface hydrogen evolution overpotential of the cathode catalytic electrode assembly is 110 mV.

[0141] Figure 6 is a linear scan diagram of the oxygen evolution reaction on the surface of the micro-nano porous Ni metal mesh in Example 1 of the present invention. As shown in Figure 6, when the potential at 20 mA / cm2 is taken as the oxygen evolution overpotential of the anode catalytic electrode assembly, the surface oxygen evolution overpotential of the anode catalytic electrode assembly is 326 mV.

[0142] Example 2

[0143] The method for preparing porous metal catalysts provided in this embodiment includes:

[0144] 1) Cut a certain size of Ni metal felt as a micron-sized porous substrate with a filament diameter of 35 μm. Select metallic Zn as the alloying layering element, in powder form with a particle size of 325 mesh. Select alumina (Al2O3) as the filler, in powder form with a particle size of 200 mesh.

[0145] 2) First, place the Ni felt into the tube furnace, then mix Zn powder and Al2O3 powder evenly in a mass ratio of 1:2 and cover the surface of the Ni felt, ensuring that the surface of the Ni felt is not exposed.

[0146] 3) Nitrogen was selected as the protective gas. After continuously introducing nitrogen for 20 minutes, the Ni felt covered with the mixed powder was heated in a tube furnace to 400℃ and held for 0.5 hours. Zn and Ni will form a Ni-Zn alloy layer on the surface of the Ni felt through thermal diffusion, with a thickness of approximately 15 μm. After the surface alloying is completed, the cooled Ni felt was separated from the mixed powder, and the residual powder on the surface was cleaned.

[0147] 4) Place the cleaned Ni felt into a vacuum heat treatment furnace and heat it at a pressure of 10. -3 Pa, temperature 600℃, heat preservation time 1.5h.

[0148] Figure 6 is a scanning electron microscope image of the micro-nano porous metal Ni felt obtained after vacuum heat treatment in Example 2 of the present invention (the inset is a partial magnified view).

[0149] Please refer to Figure 6. After vacuum heat treatment, a porous structure is formed on the surface of the Ni felt, with a ligament size of 400-600 nm and an elemental composition of 95 at.% Ni and 5 at.% Zn.

[0150] When this micro-nano porous metal Ni felt is used as a catalytic electrode for water electrolysis, the surface hydrogen evolution overpotential is 80mV.

[0151] Example 3

[0152] The method for preparing porous metal catalysts provided in this embodiment includes:

[0153] 1) Cut a Ni-Cu alloy layer mesh of a certain size as a micron porous substrate with a mesh size of 50 mesh. Select metallic Zn as the alloying element, in powder form with a particle size of 325 mesh. Select silica sand (SiO2) as the filler, in powder form with a particle size of 200 mesh.

[0154] 2) First, place the Ni-Cu alloy mesh into the box furnace, then mix Zn powder and SiO2 powder evenly in a mass ratio of 1:2 and cover the surface of the Ni-Cu alloy mesh to ensure that the surface of the Ni-Cu alloy mesh is not exposed.

[0155] 3) Argon was selected as the protective gas. After continuously introducing argon for 30 minutes, the Ni-Cu alloy mesh covered with mixed powder was heated in a tube furnace to 450℃ and held for 0.5 hours. Zn, Ni, and Cu will form a Ni-Cu-Zn alloy layer on the surface of the Ni-Cu alloy mesh through thermal diffusion, with a thickness of approximately 60 μm. After the surface alloying is completed, the cooled Ni-Cu alloy mesh was separated from the mixed powder, and the residual powder on the surface was cleaned.

[0156] 4) Place the cleaned Ni-Cu alloy mesh into a vacuum heat treatment furnace and heat it at a pressure of 10. -2 Pa, temperature 550℃, heat preservation time 1.5h.

[0157] Figure 7 is a scanning electron microscope image of the micro-nano porous Ni-Cu alloy layer obtained after vacuum heat treatment in Example 3 of the present invention (the inset is a partial magnified view), and Figure 8 is its XRD diffraction pattern.

[0158] Please refer to Figures 7 and 8. After vacuum heat treatment, a porous structure is formed on the surface of the Ni-Cu alloy layer mesh, with a ligament size of 450-600 nm and an elemental composition of 66 at.% Ni, 27 at.% Cu, and 7 at.% Zn.

[0159] When this micro-nano porous Ni-Cu alloy layer is used as a catalytic electrode for water electrolysis, the surface hydrogen evolution overpotential is 140mV.

[0160] Example 4

[0161] The method for preparing porous metal catalysts provided in this embodiment includes:

[0162] 1) Cut a Ni-Mo-Cr-Fe alloy layer mesh of a certain size as a micron porous substrate with a mesh size of 40 mesh. Select metallic Zn as the alloying element, in powder form with a particle size of 325 mesh. Select alumina (Al2O3) as the filler, in powder form with a particle size of 325 mesh.

[0163] 2) First, place the Ni-Mo-Cr-Fe alloy mesh into the box furnace, then mix Zn powder and Al2O3 powder evenly in a mass ratio of 1:1 and cover the surface of the Ni-Mo-Cr-Fe alloy mesh to ensure that the surface of the Ni-Mo-Cr-Fe alloy mesh is not exposed.

[0164] 3) Argon was selected as the protective gas. After continuously introducing argon for 30 minutes, the Ni-Mo-Cr-Fe alloy mesh covered with mixed powder was heated in a box furnace to 400℃ and held for 4 hours. Zn, Ni, Fe, Mo, and Cr will form a Ni-Mo-Cr-Fe-Zn alloy layer on the surface of the Ni-Mo-Cr-Fe alloy mesh through thermal diffusion, with a thickness of approximately 70 μm. After the surface alloying is completed, the cooled Ni-Mo-Cr-Fe alloy mesh was separated from the mixed powder, and the residual powder on the surface was cleaned.

[0165] 4) Place the cleaned Ni-Mo-Cr-Fe alloy mesh into a vacuum heat treatment furnace and heat it at a pressure of 10. -3 Pa, temperature 650℃, heat preservation time 1h.

[0166] Figure 9 is a scanning electron microscope image of the micro-nano porous Ni-Mo-Cr-Fe alloy layer obtained after vacuum heat treatment in Example 4 of the present invention (the inset is a partial magnified view), and Figure 10 is its XRD diffraction pattern.

[0167] Please refer to Figures 9 and 10. After vacuum heat treatment, a porous structure is formed on the surface of the Ni-Mo-Cr-Fe alloy mesh, with ligament sizes ranging from 100 to 300 nm. The elemental composition is 61 at.% Ni, 15 at.% Cr, 9 at.% Mo, 7 at.% Fe, and 8 at.% Zn, as shown in Figure 9. When this micro-nano porous Ni-Mo-Cr-Fe alloy mesh is used as a catalytic electrode for water electrolysis, the surface hydrogen evolution overpotential is 101 mV, and the surface oxygen evolution overpotential is 200 mV.

[0168] Example 5

[0169] The method for preparing porous metal catalysts provided in this embodiment includes:

[0170] 1) Cut a Ni-Fe-Cr alloy layer mesh of a certain size as a micron porous substrate with a mesh size of 100 mesh. Select metallic Zn as the alloying element, which is in powder form with a particle size of 325 mesh. Select alumina (Al2O3) as the filler, which is in powder form with a particle size of 325 mesh.

[0171] 2) First, place the Ni-Fe-Cr alloy mesh into the tube furnace, then mix Zn powder and Al2O3 powder evenly in a mass ratio of 1:3 and cover the surface of the Ni-Fe-Cr alloy mesh to ensure that the surface of the Ni-Fe-Cr alloy mesh is not exposed.

[0172] 3) Argon was selected as the protective gas. After continuously introducing argon for 30 minutes, the Ni-Fe-Cr alloy mesh covered with mixed powder was heated in a tube furnace to 500℃ and held for 0.5 hours. Zn, Ni, Fe, and Cr will form a Ni-Fe-Cr-Zn alloy layer on the surface of the Ni-Fe-Cr alloy mesh through thermal diffusion, with a thickness of approximately 50 μm. After the surface alloying is completed, the cooled Ni-Fe-Cr alloy mesh was separated from the mixed powder, and the residual powder on the surface was cleaned.

[0173] 4) Place the cleaned Ni-Fe-Cr alloy mesh into a vacuum heat treatment furnace and heat it at a pressure of 10. -2 Pa, temperature 550℃, heat preservation time 2.5h.

[0174] Figure 11 is a scanning electron microscope image of the micro-nano porous Ni-Fe-Cr alloy layer obtained after vacuum heat treatment in Example 5 of the present invention (the inset is a partial magnified view).

[0175] Please refer to Figure 11. After vacuum heat treatment, a porous structure is formed on the surface of the Ni-Fe-Cr alloy layer mesh, with a ligament size of 300-400 nm and an elemental composition of 68 at.% Ni, 18 at.% Cr, 9 at.% Fe, and 5 at.% Zn.

[0176] When this micro-nano porous Ni-Fe-Cr alloy layer is used as a catalytic electrode for water electrolysis, the surface hydrogen evolution overpotential is 132mV.

[0177] Example 6

[0178] Compared to Examples 1-5, this embodiment further involves etching a Ni mesh with a porous surface in an acidic solution, resulting in a catalyst with a tertiary porous structure. Specifically, the preparation method of the porous metal catalyst provided in this embodiment includes:

[0179] 1) Cut a Ni-Mn alloy mesh as the first metal with a mesh size of 50; select Zn metal as the alloying element, which is in powder form with a particle size of 325; select alumina (Al2O3) as the filler, which is in powder form with a particle size of 325.

[0180] 2) First, place the Ni-Mn alloy mesh into the tube furnace. Then, mix Zn powder and Al2O3 powder evenly in a mass ratio of 1:1 and cover the surface of the metal mesh to ensure that the surface of the metal mesh is not exposed.

[0181] 3) Argon was selected as the protective gas. After argon was continuously introduced for 30 minutes, the Ni-Mn alloy mesh covered with mixed powder was heated in a tube furnace to a temperature of 500℃ and held for 0.5 hours.

[0182] Zn, Ni, and Mn will form a Ni-Mn-Zn alloy layer on the surface of the Ni-Mn alloy mesh through solid thermal diffusion, with a thickness of approximately 80 μm.

[0183] After the surface alloying is completed, the cooled Ni alloy mesh is separated from the mixed powder and the residual powder on the surface is cleaned.

[0184] The cleaned Ni mesh was placed in a vacuum heat treatment furnace and heated at a pressure of 50 Pa and a temperature of 450 °C for 3 hours.

[0185] A Ni mesh with a porous surface is placed in an acidic solution of ammonium sulfate with a concentration of 0.5M to 2M for corrosion to obtain a metal catalyst with a tertiary porous feature. Its ligament structure is composed of crystals, as shown in Figure 12.

[0186] After vacuum heat treatment and free corrosion, a three-level porous structure is formed on the surface of the Ni mesh, with a ligament size of 20-30 nm and an elemental composition of 88 at.% Ni, 8.2 at.% Zn, and 3.5 at.% Mn.

[0187] Comparative Example 1

[0188] Comparative Example 1 is a nickel mesh with Raney nickel sprayed on its surface. Figure 13 is a scanning electron microscope image of the nickel mesh with Raney nickel sprayed on its surface in Comparative Example 1 of the present invention (the inset is a partial magnified view); the linear scanning diagram of its surface hydrogen evolution reaction is shown in Figure 14, and its surface hydrogen evolution overpotential is 182mV.

[0189] Examples 1-5 were prepared with micron-sized porous substrates of different structures and compositions. Under different alloying temperatures and times, and vacuum heat treatment temperatures and times, cathode catalytic electrode assemblies were obtained and applied to the electrolysis of water. The surface hydrogen evolution overpotentials of the cathode catalytic electrode assemblies in Examples 1-5 were obtained respectively. As shown in Figures 3, 5, and 8, Examples 1-5 all have relatively low surface hydrogen evolution overpotentials. However, the surface hydrogen evolution overpotential of Comparative Example 1 is higher than that of Examples 1-5 provided by this invention. Compared to Comparative Example 1, the cathode catalytic electrode assemblies provided in Examples 1 to 5 not only ensure the mechanical strength of the cathode catalytic electrode assembly but also significantly improve its catalytic activity.

[0190] Compared to Examples 1-5, the Ni mesh in Example 6 was etched in an acidic solution: ammonium sulfate with a concentration of 0.5M to 2M, resulting in a metal catalyst with tertiary porous characteristics. As a cathode catalytic electrode assembly, the surface hydrogen evolution overpoint was lower, and the catalytic activity was far superior to the cathode catalytic electrode assemblies in Examples 1-5.

[0191] Furthermore, as can be seen from Examples 1 and 4, the porous metal catalyst provided in the embodiments of the present invention can be used as both a cathode and an anode in the water electrolysis hydrogen production process. When used as a cathode, it exhibits catalytic activity for the hydrogen evolution reaction, and when used as an anode, it exhibits catalytic activity for the oxygen evolution reaction.

[0192] In summary, the technical solution provided by this invention improves the activity of porous metal catalysts while ensuring the mechanical strength of the porous metal catalyst structure. Compared with vapor-phase alloy layering, it requires less time and is more efficient to prepare alloy layers of the same thickness. In addition, the preparation method described in this invention has less environmental impact, lower production costs, and is easier to scale up for production.

[0193] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a porous metal catalyst, characterized by, The method comprises the following steps: providing a microporous substrate, a second metal and a filler; mixing the second metal and the filler to form a mixture; putting the microporous substrate into an alloying device, the microporous substrate being in a shape of a net, a foam or a felt; covering the surface of the microporous substrate with the mixture; after covering the surface of the microporous substrate with the mixture, annealing the microporous substrate and the second metal to form an alloy layer on the surface of the microporous substrate; putting the microporous substrate with the alloy layer on the surface into a vacuum heat treatment device to perform vacuum heat treatment and form a porous metal catalyst.

2. The method of claim 1, wherein the porous metal catalyst is prepared by the steps of: During the annealing, the alloy layer formation temperature is 300-500℃, and the holding time is 0.5-5h.

3. The method of claim 1, wherein the porous metal catalyst is prepared by the steps of: The thickness of the alloy layer is 10-100μm.

4. The method of claim 1, wherein the porous metal catalyst is prepared by The vacuum heat treatment is performed under a pressure of less than 50Pa, at a temperature of 450-850℃, and for a holding time of 0.5-3.5h.

5. The method of claim 1, wherein the porous metal catalyst is prepared by the steps of: The ligament size of the porous metal catalyst is 100nm-2.5μm.

6. The method of claim 1, wherein the porous metal catalyst is prepared by the steps of: The filler comprises alumina or quartz sand.

7. The method according to claim 1, wherein the second metal and the filler are in a powder shape.

8. The method of claim 7, wherein the porous metal catalyst is prepared by, When the microporous substrate is in a shape of a net or a foam, the mesh number of the microporous substrate is 10-110, and when the microporous substrate is in a shape of a felt, the wire diameter of the microporous substrate is 3-100μm.

9. The method of claim 7, wherein the porous metal catalyst is prepared by a method comprising: The particle size of the second metal is 120-325 mesh, and the particle size of the filler is 40-325 mesh.

10. The method of claim 1, wherein the porous metal catalyst is prepared by the steps of: The mass ratio of the second metal to the filler is 1:1-1:

3.

11. The method of claim 1, wherein the porous metal catalyst is prepared by a process comprising: providing a metal powder; and sintering the metal powder to form a porous metal catalyst. The alloy layer formation device comprises a box furnace or a tube furnace.

12. The method of claim 1, wherein the porous metal catalyst is prepared by a method comprising: providing a metal powder; and sintering the metal powder to form a porous metal catalyst. During the annealing, the protective gas is introduced into the alloy layer formation device for 15-30 minutes before starting heating, and the protective gas is argon or nitrogen.

13. The method of claim 1, wherein the porous metal catalyst is prepared by a method comprising: providing a metal powder; and sintering the metal powder to form a porous metal catalyst. The microporous substrate comprises a first characteristic metal, and after the microporous substrate with the porous metal catalyst is formed, the method further comprises the following steps: putting the microporous substrate with the porous metal catalyst into an acid solution to perform etching and obtain a metal catalyst with a tertiary porous structure.

14. The method of claim 13, wherein the porous metal catalyst is prepared by The first characteristic metal comprises two or more microporous substrate elements, and at least one of the two or more microporous substrate elements is Mn or Al.

15. The method of claim 13, wherein the porous metal catalyst is prepared by a method comprising: The acid solution is ammonium sulfate.

16. The method of claim 15, wherein the porous metal catalyst is prepared by The concentration of the ammonium sulfate is greater than or equal to 0.5M.

17. The method of claim 1, wherein the alloy layer comprises a first metal element and a second metal element, the first metal element comprising at least one of Ni, Fe, Cu, Co, Mn, Ti, Cr, Mo, Al, W, Ta, Au, Ag, Nb, Zr, V, and the second metal element comprising: Any one of Zn, Mg, Bi and Cd.

18. A method for preparing an electrode catalytic assembly, comprising the method for preparing the porous metal catalyst according to any one of claims 1-17.

19. A porous metal catalyst, characterized by, The method comprises the following steps: a microporous substrate with an alloy layer of a first metal element and a second metal on the surface, the alloy layer further comprising a filler, and the alloy layer having micro-nano porosity.

20. The porous metal catalyst of claim 19, wherein, In the alloy layer, the mole percentage of the first metal element is 20%-50%, and the mole percentage of the second metal element is 50%-80%.

21. The porous metal catalyst of claim 19, wherein, The alloy layer further comprises nanoscale porosity.

22. The porous metal catalyst of claim 21, wherein, The specific surface area of the porous metal catalyst is 75-95 m 2 / g.

23. The porous metal catalyst of claim 22, wherein, The micrometer-scale pores in the micrometer-porous substrate have a pore size of 5-500 micrometers, the micro-nano-porous substrate has a ligament size of 0.1-10 micrometers, and the nanoscale-porous substrate has a ligament size of 10-99 nanometers.

24. A catalysed electrode assembly characterised in that, The porous metal catalyst comprises the porous metal catalyst of claim 15 or 17.

25. Use of the catalytic electrode assembly of claim 18 in hydrogen production by water splitting.

26. Use of the catalytic electrode assembly according to claim 25 for the hydrogen production by water splitting, characterized in that, The catalytic electrode assembly exhibits catalytic activity for the oxygen evolution reaction.

27. Use of the catalytic electrode assembly according to claim 25 for the hydrogen production by water splitting, characterized in that, The catalytic electrode assembly exhibits catalytic activity for the hydrogen evolution reaction.

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