KR102257787B1 - Porous transition metal alloy catalyst, synthesys of porous transition metal alloy catalyst, and electrochemical system including porous transition metal alloy catalyst - Google Patents

Abstract

A porous transition metal alloy catalyst according to an embodiment of the present invention is a porous transition metal alloy catalyst obtained by selectively etching a transition metal alloy including a primary phase and a eutectic phase, wherein the transition metal alloy catalyst includes a first metal and a second metal, and includes a nanostructure supported on the surface of the primary phase and made of the second metal.

Description

POROUS TRANSITION METAL ALLOY CATALYST, SYNTHESYS OF POROUS TRANSITION METAL ALLOY CATALYST, AND ELECTROCHEMICAL SYSTEM INCLUDING POROUS TRANSITION METAL ALLOY CATALYST}

The present invention relates to a porous transition metal alloy catalyst, a method for preparing a porous transition metal alloy catalyst, and an electrochemical system including a porous transition metal alloy catalyst, and more particularly, to a thermodynamically phase-controlled porous transition metal alloy catalyst, and It relates to an electrochemical system including this.

Recently, as a countermeasure to solve environmental problems caused by depletion of carbon-based energy and emission of fuel gas, research on a method of storing energy by producing hydrogen and oxygen by water decomposition or obtaining energy through fuel cells has been actively conducted. It's going on. In these methods, an electrochemical reaction is used, and since it is required to secure the performance of the catalyst in order to increase the reaction rate, a rare metal-based catalyst is mainly used and a very high price is required. Transition metal-based catalysts to replace rare metals are being studied, but there is a problem that the performance as a catalyst is low due to high overvoltage and low stability.

One of the technical problems to be achieved by the technical idea of the present invention is to provide a porous transition metal alloy catalyst having various active points according to a composition and a surface area change due to a microstructure through thermodynamic phase control, and an electrochemical system including the same. .

The method of manufacturing a porous transition metal alloy catalyst according to an embodiment of the present invention comprises the steps of forming a transition metal molten alloy by mixing a first metal and a second metal and heating to a temperature equal to or higher than the melting point, and cooling the transition metal molten alloy. Forming a transition metal alloy, and removing the first metal by selectively etching the transition metal alloy.

The porous transition metal alloy catalyst according to an embodiment of the present invention is a porous transition metal alloy catalyst obtained by selectively etching a transition metal alloy including a primary phase and a eutectic phase, and the transition The metal alloy includes a first metal and a second metal, is supported on the surface of the supernormal phase, and includes a nanostructure made of the second metal.

An electrochemical system according to an embodiment of the present invention includes a reactor including an aqueous electrolyte solution, first and second electrodes in which at least a portion is immersed in the aqueous electrolyte solution, and coated on the surface of the first electrode, and a porous transition metal alloy catalyst It includes a catalyst layer comprising a, and a power supply for applying an electrical signal to the first and second electrodes.

A porous transition metal alloy catalyst prepared based on thermodynamic phase control and an electrochemical system including the same may be provided.

Various and beneficial advantages and effects of the present invention are not limited to the above description, and will be more easily understood in the course of describing specific embodiments of the present invention.

1 is a phase diagram of nickel and aluminum.
2A to 2E are SEM images of a nickel-aluminum alloy alloyed by varying the composition ratio of nickel and aluminum.
3A to 3E are SEM images of a porous nickel-aluminum alloy catalyst obtained by selectively etching a nickel-aluminum alloy alloyed by varying the composition ratio of nickel and aluminum.
4 is a schematic diagram of an electrochemical system including a porous nickel aluminum alloy catalyst according to an embodiment of the present invention.
5 is a current-voltage graph showing catalytic properties of a porous nickel aluminum alloy catalyst according to an embodiment of the present invention.
6 is a current-voltage graph showing characteristics of the catalyst when the porous nickel-aluminum alloy catalyst according to an embodiment of the present invention is prepared in ink form.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

The embodiments of the present invention may be modified in various different forms or may be combined with various embodiments, and the scope of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the art. Accordingly, the shape and size of elements in the drawings may be exaggerated for clearer explanation, and elements indicated by the same reference numerals in the drawings are the same elements.

Porous transition metal alloy catalyst manufacturing method

A method of manufacturing a porous transition metal alloy catalyst according to an embodiment of the present invention includes the steps of (1) mixing a first metal and a second metal and heating to a temperature equal to or higher than the melting point to form a transition metal molten alloy, (2) transition Cooling the molten metal alloy to form a transition metal alloy, and (3) selectively etching the transition metal alloy to remove the first metal. Hereinafter, each step will be described in detail.

(1) A transition metal molten alloy can be formed by mixing the first metal and the second metal and heating to a temperature equal to or higher than the melting point.

The first metal may be a metal capable of selective etching in relation to the second metal. For example, sodium (Na), magnesium (Mg), aluminum (Al), potassium (K), calcium ( Ca), gallium (Ga), indium (In), and may contain at least one of tin (Sn). The second metal may be a transition metal exhibiting catalytic activity, for example, titanium (Ti), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc ( It may contain at least one of Zn), molybdenum (Mo), and silver (Ag). The first metal and the second metal may be mixed in an appropriate composition ratio to control the microstructure by referring to the phase equilibrium of the alloy of each metal. Here, the composition ratio may mean atomic percent (at%) of the first and second metals. In addition, according to embodiments, a transition metal molten alloy may be formed by including three or more of the metals, and some impurities may be included.

The alloy of the first and second metals may be heated to a temperature equal to or higher than the melting point so that the first metal and the second metal are completely melted. The transition metal molten alloy may be in a state in which the first and second metals are completely melted and uniformly mixed.

(2) The transition metal molten alloy can be cooled to form a transition metal alloy.

In the step of cooling the transition metal molten alloy, phases having different compositions may be formed to form a fine structure to form a transition metal alloy. For example, as the transition metal molten alloy solidifies, a primary phase may be deposited first, and a eutectic phase may be deposited last. The microstructure of the transition metal alloy may be variously changed according to the composition ratio of the first and second metals. In addition, the cooling method may be variously changed according to embodiments.

(3) The transition metal alloy can be selectively etched to remove the first metal.

The first metal can be removed by selectively etching the transition metal alloy with an acid or basic solution. As the first metal is removed from the transition metal alloy, a porous transition metal alloy catalyst having a porous structure may be formed. In the step of selectively etching the first metal, the second metal remaining while the first metal is removed may form a nanostructure. Due to the structure of the nanostructure, the surface area and the active point of the porous transition metal alloy catalyst are changed, and accordingly, the characteristics of the electrochemical catalyst may be determined.

Examples of porous nickel aluminum alloy catalyst

The porous nickel-aluminum alloy catalyst according to an embodiment of the present invention corresponds to a case where the first metal is aluminum (Al) and the second metal is nickel (Ni) in the method for manufacturing the porous transition metal alloy catalyst described above. Hereinafter, each step of the method for manufacturing a porous nickel aluminum alloy catalyst will be described in detail with reference to FIGS. 1 to 3E.

1 is a phase diagram of nickel and aluminum.

2A to 2E are SEM images of a nickel-aluminum alloy in the first to fifth experimental examples manufactured by varying the composition ratio of nickel and aluminum through steps (1) and (2).

3A to 3E show the porous nickel of the first to fifth embodiments obtained by selectively etching the nickel-aluminum alloy of the first to fifth experimental examples prepared by varying the composition ratio of nickel and aluminum through the step (3). These are SEM images of an aluminum alloy catalyst.

Referring to FIG. 1, nickel and aluminum may be mixed at different composition ratios. For example, nickel and aluminum may be mixed in a composition ratio of more than 0 atomic% of nickel and not more than 25 atomic %. The mixed alloy may be heated at a temperature equal to or higher than the melting point, for example, at a temperature equal to or higher than about 1200° C. (about 1473 K) to form a nickel-aluminum molten alloy. The nickel-aluminum molten alloy may be in a state in which nickel and aluminum are completely melted and uniformly mixed.

According to the technical idea of the present invention, in the step of cooling the nickel-aluminum molten alloy to form a nickel-aluminum alloy, the microstructure of the nickel-aluminum alloy can be controlled by adjusting the composition ratio range, cooling method or cooling rate, impurity content, etc. . Hereinafter, the microstructure of the nickel-aluminum alloy at a specific composition ratio will be exemplarily described, but the microstructure as described above may be variously changed in the embodiments.

Referring to FIGS. 1 and 2A, a nickel-aluminum alloy of the first experimental example (FIG. 1A) in which the composition ratio of nickel is about 5 atomic% may be prepared. As the nickel-aluminum molten alloy is cooled in the liquid phase L, it reaches a temperature of about 697° C. (about 970 K), so that an Al ₃ Ni primary phase may be deposited first. Referring to the phase equilibrium, the composition ratio of nickel and aluminum is changed due to diffusion of nickel and aluminum atoms in an adjacent region of the supernormal, and the supernormal may grow. For example, as the supernormal phase is gradually cooled from about 697° C. (about 970 K) to about 640° C. (about 916.5 K), the supernormal phase can grow with a relatively increase in the composition ratio of aluminum. While the nickel-aluminum molten alloy continues to solidify, the Al ₃ Ni and Al eutectic phases may be deposited upon reaching a temperature of about 640° C. (about 916.5 K). The average composition ratio of nickel and aluminum in the process may be different from the composition ratio of super-normal nickel and aluminum. For example, the process phase may have a higher average composition ratio of aluminum than the supernormal phase. As the temperature of the nickel-aluminum molten alloy is further lowered, the process phase may be deposited in a lamellar structure. In FIG. 2A, it can be seen that the supernormal phase is relatively bright, and the process phase is formed in a layered structure in the surrounding region of the supernormal phase. Referring to the phase equilibrium diagram of FIG. 1, as the composition ratio of nickel increases, the ratio of the supernormal phase may be relatively increased.

Referring to FIGS. 1 and 2B, a nickel-aluminum alloy of the second experimental example (FIG. 1(b)) in which the composition ratio of nickel is about 10 atomic% may be prepared. As the nickel-aluminum molten alloy is cooled in the liquid phase (L), it reaches a temperature of about 757°C (about 1030 K), so that the Al ₃ Ni supernormal phase may be deposited first. Referring to the phase equilibrium, the composition ratio of nickel and aluminum is changed due to diffusion of nickel and aluminum atoms in a region adjacent to the supernormal, and the supernormal may grow. For example, as the supernormal phase is gradually cooled from about 757°C (about 1030 K) to about 640°C (about 916.5 K), the supernormal phase can grow with an increase in the proportion of aluminum. Some of the supernormal phase can grow into a dendrite structure, and another part into a globular structure. _{While the nickel-aluminum molten alloy continues to solidify, the Al 3} Ni and Al eutectic phases may be deposited when the temperature reaches a temperature of about 640° C. (about 916.5 K). As the composition ratio of nickel changes, the width of the stem of the dendrite structure, the spacing between the stems, the width of the branches, the spacing between the branches, the number of branches, etc. can be variously changed. have. Referring to FIG. 2B, it can be seen that a relatively bright image is a supernormal phase, a relatively dark image is a process phase, and a supernormal phase has a dendrite structure or a spherical structure.

Referring to FIGS. 1 and 2C, a nickel-aluminum alloy of the third experimental example (FIG. 1C) in which the composition ratio of nickel is about 15 atomic% may be prepared. As the nickel-aluminum molten alloy is cooled in the liquid phase (L), it reaches a temperature of about 827 °C (about 1100 K), so that the Al ₃ super-normal phase may be precipitated first, and when it reaches a temperature of about 640 °C (about 916.5 K), Al ₃ Ni and Al process phases may be deposited. As described above with reference to FIG. 2B, the supernormal phase may have a dendrite structure and a spherical structure, but the composition ratio may vary. Referring to FIG. 2C, it can be seen that a relatively bright image is a supernormal, and the ratio is relatively increased compared to the supernormal image of FIG. 2B.

Referring to FIGS. 1 and 2D, a nickel-aluminum alloy of the fourth experimental example (FIG. 1(d)) in which the composition ratio of nickel is about 20 atomic% may be prepared. As the nickel-aluminum molten alloy is cooled in the liquid phase (L), it reaches a temperature of about 907 °C (about 1180 K), so that Al ₃ Ni ₂ and Al ₃ Ni supernormal phases can be sequentially deposited, and about 640 °C (about 916.5 K) When the temperature of Al ₃ Ni and Al process phases may be deposited. As described above with reference to FIG. 2C, the supernormal phase may have a dendrite structure and a spherical structure, but the supernormal phase may appear relatively more than the process phase.

Referring to FIGS. 1 and 2E, a nickel-aluminum alloy of the fifth experimental example (FIG. 1(e)) in which the composition ratio of nickel is about 25 atomic% may be prepared. As the nickel-aluminum molten alloy is cooled in the liquid phase (L), it reaches a temperature of about 1097 °C (about 1370 K), so that Al ₃ Ni ₂ and Al ₃ Ni supernormal phases can be sequentially deposited, and about 640 °C (about 916.5 K) _{It is the upper limit at which Al 3} Ni and Al eutectic phases can be deposited when the temperature of is reached. Compared with the one described above with reference to FIG. 2D, it can be seen that the ratio in the process is significantly reduced.

Next, a porous nickel aluminum alloy catalyst prepared by selectively etching a nickel aluminum alloy will be described.

A nickel aluminum alloy can be selectively etched aluminum against nickel with a basic solution, for example a potassium hydroxide (KOH) solution. As aluminum of the nickel aluminum alloy is removed by selective etching, a porous nickel aluminum alloy catalyst may be prepared. _{In this process, as aluminum is removed from Al 3} Ni and Al that formed the process phase, the remaining nickel aggregates to form a nanostructure on the surface of the supernormal phase. The nanostructure may include nickel. Nickel forming the nanostructure may exist in the form of nickel metal or nickel oxide. The nanostructure may have a nanowire or nanoparticle form, and may form an active site while increasing an active surface area on a supernormal surface.

3A shows the porous nickel-aluminum alloy catalyst of the first embodiment obtained by selectively etching the nickel-aluminum alloy of the first experimental example in which the composition ratio of nickel is about 5 atomic%.

Referring to FIG. 3A, it can be seen that the nanostructure has the form of nanowires or nanoparticles, and is distributed on the surface of the porous nickel aluminum alloy catalyst. The nanostructures may be extended and distributed in a certain direction, or may be extended and distributed in an irregular direction. 3A shows a nanostructure in which the supernormal phase is distributed based on a region having a spherical structure, but the nanostructure may be similarly distributed in a region in which the supernormal phase has a dendrite structure. These nanostructures can affect the catalytic properties of the porous nickel aluminum alloy catalyst.

The microstructure of the porous nickel-aluminum alloy catalyst and the characteristics of the catalyst can be applied even when nickel has a composition ratio of about 2 to about 3 atomic% less or greater than about 5 atomic%.

3B shows the porous nickel-aluminum alloy catalyst of the second embodiment obtained by selectively etching the nickel-aluminum alloy of the second experimental example in which the composition ratio of nickel is about 10 atomic%.

Referring to FIG. 3B, a nanostructure distributed based on a region in which the supernormal phase has a dendrite structure can be confirmed. The dendrite structure can be partially retained even after selective etching with a basic solution. However, aluminum included in the supernormal dendrite structure can be removed. The nanostructure may be supported on the surface of the supernormal dendrite structure. The nanostructure may have a nanowire or nanoparticle shape.

The nanostructure may have a size smaller than one branch, which is the basic unit of the dendrite structure. For example, the nanostructure may be in the form of a nanowire having an average diameter corresponding to about 5% to about 20% of the average diameter of one branch constituting the dendrite structure. The nanostructure may be in the form of nanoparticles having an average diameter ranging from about 10 nm to about 100 nm. The nanostructures may be aggregated or entangled with each other, and may be irregularly dispersed and disposed on the supernormal surface. The catalytic properties of the porous nickel-aluminum alloy catalyst may be determined by the microstructure formed by such a nanostructure. This will be described again with reference to FIGS. 5 and 6.

The microstructure of the porous nickel-aluminum alloy catalyst and the characteristics of the catalyst can be applied even when nickel has a composition ratio of about 2 to about 3 atomic% less or greater than about 10 atomic%.

3C shows the porous nickel-aluminum alloy catalyst of the third embodiment in which the nickel-aluminum alloy of the third experimental example is selectively etched, in which the composition ratio of nickel is about 15 atomic%.

3D shows the porous nickel-aluminum alloy catalyst of the fourth embodiment in which the nickel-aluminum alloy of the fourth experimental example is selectively etched, in which the composition ratio of nickel is about 20 atomic%.

3E shows a porous nickel-aluminum alloy catalyst of a fifth example in which the nickel-aluminum alloy of the fifth test example was selectively etched, in which the composition ratio of nickel was about 25 atomic%.

Referring to FIGS. 3C to 3E, the supernormal phase of the nickel-aluminum alloy may have a dendrite or a spherical structure. The microstructure formed by the supernormal and nanostructures may be similar to those described above with reference to FIGS. 3A and 3B.

3A to 3E, the nanostructure may have a size smaller than that of a supernormal. For example, the average diameter of the nanostructure may correspond to about 5% to about 20% of the average diameter of grains forming a supernormal phase. The average diameter of the crystal grains constituting the supernormal may be in the range of about 0.1 μm to about 10 μm, and the average diameter of the nanostructure may be in the range of about 10 nm to about 200 nm. In particular, the average diameter of the nanostructure may range from about 10 nm to about 50 nm.

Application example of electrochemical system containing porous transition metal catalyst

4 is a schematic diagram of an electrochemical system according to an embodiment of the present invention.

Referring to FIG. 4, the electrochemical system 100 includes a reactor 110, an aqueous electrolyte solution 120, a first electrode 130, a second electrode 140, a catalyst layer 150, and a power supply unit 160. can do. The first and second electrodes 130 and 140 may be connected by the power supply unit 160. In addition, according to embodiments, the electrochemical system 100 divides the reference electrode connected to the power supply unit 160, the first and second electrodes 130 and 140, and comprises a membrane made of an ion-permeable material, and a product collection unit. And the like may be further included.

The reactor 110 may be made of a material capable of accommodating the aqueous electrolyte solution 120. The reactor 110 may be made of, for example, pyrex, acrylic, polyvinyl chloride (PVC), or the like. The reactor 110 accommodates the aqueous electrolyte solution 120, and may further include an inlet and an outlet such as an inlet pipe and a drain pipe.

The aqueous electrolyte solution 120 may serve as a source of water used in a water decomposition reaction and a receptor for a proton generated during a water decomposition reaction. The electrolyte aqueous solution 120 may include at least one of potassium phosphate and sodium phosphate such as _{, for example, KH 2} PO ₄ , K ₂ HPO ₄ , K ₃ PO _{4 or a mixture thereof.} The pH of the aqueous electrolyte solution 120 may range from 2 to 14. In order to serve as a receptor for the proton, the aqueous electrolyte solution 120 may include a proton-accepting anion. ^{Accordingly, even if the amount of protons (H +} ) is increased as the water decomposition reaction proceeds, the proton-soluble anion accommodates at least some of these protons, thereby lowering the rate of decrease in pH of the aqueous electrolyte solution 120. The proton-soluble anion may include at least one of a phosphate ion, an acetate ion, a borate ion, and a fluoride ion.

Each of the first and second electrodes 130 and 140 may be made of a conductive material such as a semiconductor or a metal. The first and second electrodes 130 and 140 are, for example, fluorine-doped tin oxide (FTO), cobalt (Co), copper (Cu), nickel (Ni), iron (Fe), iridium (Ir), At least one of ruthenium (Ru), palladium (Pd), gold (Au), platinum (Pt), titanium (Ti), zirconium (Zr), rhodium (Rh), chromium (Cr), and stainless steel It may include.

The catalyst layer 150 may include a catalyst material that promotes a water oxidation or reduction reaction, and may include, for example, a porous transition metal alloy catalyst. Porous transition metal alloy catalyst is a first metal capable of selective etching, sodium (Na), magnesium (Mg), aluminum (Al), potassium (K), calcium (Ca), gallium (Ga), indium (In), And tin (Sn), and as a second metal exhibiting catalytic activity, titanium (Ti), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper ( It may contain at least one of Cu), zinc (Zn), molybdenum (Mo), and silver (Ag). In an exemplary embodiment, the porous transition metal alloy catalyst may be the porous nickel aluminum alloy catalyst described above with reference to FIGS. 3A to 3E. In the case of a porous nickel-aluminum alloy catalyst, nanostructures of various arrangements, shapes, and sizes may be included depending on the supernormal and process microstructures, and these nanostructures may affect the properties of the electrochemical catalyst on the surface of the alloy catalyst. I can. The structure of the porous nickel-aluminum alloy catalyst is the same as described above with reference to FIGS. 3A to 3E, and a description thereof will be omitted.

When a voltage is applied between the first and second electrodes 130 and 140 by the power supply unit 160 in the electrochemical system 100, hydrogen is generated in the first electrode 130 and the second electrode 140 Oxygen is generated in the reaction. Each half reaction is represented by Schemes 1 and 2 as follows.

[Reaction Scheme ^{1] 4H + + 4e - →} 2H 2

[Reaction Scheme _{2] 2H 2 O → O 2} + 4H + + 4e -

The first electrode 130 and the catalyst layer 150 according to an exemplary embodiment of the present invention may participate in a hydrogen generation reaction (HER), which is a reduction reaction in the first electrode 130 represented by Scheme 1 above. Accordingly, HER can be performed with a relatively low overpotential under the function of the stable catalyst layer 150.

As an electrochemical reaction system according to an embodiment of the present invention, a water decomposition system has been exemplarily described, but the present invention is not limited thereto, and the electrode structure according to an embodiment of the present invention is oxidized or oxidized in various electrochemical reaction systems. It may be used in an electrode for reduction reaction.

Evaluation of catalytic properties of porous nickel aluminum alloy catalyst

FIG. 5 is a diagram illustrating a cyclic voltammorgram for hydrogen generation reaction compared to a reversible hydrogen electrode (RHE) when a porous nickel-aluminum alloy catalyst according to an embodiment of the present invention is used.

The composition ratio of nickel is about 5 atomic% (Al ₉₅ Ni ₅ ), about 10 atomic% (Al ₉₀ Ni ₁₀ ), about 15 atomic% (Al ₈₅ Ni ₁₅ ), about 20 atomic% (Al ₈₀ Ni ₂₀ ), and about The catalyst properties of each of the porous nickel-aluminum alloy catalysts of the first to fifth examples having 25 atomic% (Al ₇₅ Ni _{25) were analyzed.} Each porous nickel-aluminum alloy catalyst was adhered on a nickel foil using silver (Ag), and the periphery of the porous nickel-aluminum alloy catalyst was molded with an epoxy resin, and the catalytic active side was exposed, The catalyst properties were analyzed. Cyclic current-voltage method was performed by repeating at a scan rate of 1 mV/s between electrodes of -0.10 V to 0.10 V compared to the reference electrode.

The porous nickel-aluminum alloy catalyst of the second embodiment, in which the composition ratio of nickel is about 10 atomic%, exhibited the best catalytic properties. Specifically, the first embodiment having a nickel composition ratio of about 5 atomic% (Al ₉₅ Ni ₅ ) based on the same current density of about 50 mA/cm ² requires an overvoltage of about 110 mV, and a nickel composition ratio of about 10 atomic% The second embodiment of (Al ₉₀ Ni ₁₀ ) requires an overvoltage of about 48 mV, and the third embodiment with a nickel composition ratio of about 15 atomic% (Al ₈₅ Ni ₁₅ ) requires an overvoltage of about 66 mV, The fourth embodiment having a nickel composition ratio of about 20 atomic% (Al ₈₀ Ni ₂₀ ) requires an overvoltage of about 88 mV, and the fifth embodiment having a nickel composition ratio of about 25 atomic% (Al ₇₅ Ni _{25) is about 80 mV} Overvoltage was required. Therefore, the porous nickel-aluminum alloy catalyst of the second embodiment, in which the nickel composition ratio to the same current density is about 10 atomic%, is required to have the lowest overvoltage for the hydrogen generation reaction.

In general, as the proportion of aluminum increases, the amount of aluminum removed during selective etching of the nickel-aluminum alloy increases, so that a nickel-aluminum alloy having a relatively more porous structure may be formed.

However, according to the technical idea of the present invention, it was found that the catalytic properties of the porous nickel-aluminum alloy catalyst of the second embodiment in which the composition ratio of nickel is about 10 atomic% is the most excellent. The characteristics of these catalysts are analyzed to be due to the fine nanostructures formed on the surface of the porous nickel aluminum alloy catalyst. That is, the catalytic properties of the porous nickel-aluminum alloy catalyst may be determined by changes in surface area and active point due to the porous structure of the porous nickel-aluminum alloy catalyst and the nanostructure supported on the surface of the porous nickel-aluminum alloy catalyst.

Unlike the prior art that did not perform thermodynamic phase control, according to the technical idea of the present invention, by controlling the supernormal structure of the porous nickel-aluminum alloy catalyst and the structure of the nanostructure through thermodynamic phase control, the catalytic performance is improved. It is possible to provide a nickel aluminum alloy catalyst.

In addition, according to the technical idea of the present invention, it is not limited to the nickel-aluminum alloy catalyst, and it is possible to provide a porous transition metal alloy catalyst that thermodynamically considers the phase structure and composition from the phase equilibrium of various metals. A porous transition metal alloy catalyst having excellent catalytic activity in a target electrochemical reaction can be provided by varying the composition ratio of each metal and the shape of the precipitated phases, the cooling method of the alloy, and impurities accordingly. The porous transition metal alloy catalyst can be applied as an electrode of an oxidation and reduction electrochemical system including a hydrogen generation reaction, an oxygen generation reaction, a chlorine generation reaction, a nitrogen reduction reaction, and a carbon dioxide reduction reaction.

Evaluation of catalyst properties in an electrode coated with a porous nickel aluminum alloy catalyst

In an electrochemical system including a large-area electrode coated with a porous nickel aluminum alloy catalyst according to an embodiment of the present invention, characteristics of the catalyst were analyzed.

6 is a cyclic voltammorgram for hydrogen generation reaction occurring in an electrode coated with a porous nickel aluminum alloy catalyst compared to a reversible hydrogen electrode (RHE).

First, a method of manufacturing an electrode coated with a porous nickel aluminum alloy catalyst according to an embodiment of the present invention will be described.

The method of manufacturing an electrode coated with a porous nickel-aluminum alloy catalyst includes (1) mixing nickel and aluminum and heating at a temperature above the melting point to form a nickel-aluminum molten alloy, and (2) cooling the nickel-aluminum molten alloy to form a nickel-aluminum alloy. Forming a porous nickel-aluminum alloy catalyst by removing aluminum of the nickel-aluminum alloy by selective etching, (4) preparing a porous nickel-aluminum alloy catalyst in the form of a powder to form a solvent with a carbon conductor and a binder. Mixing the catalyst ink to prepare a catalyst ink, (5) drop-coating the catalyst ink on a nickel substrate, and drying at room temperature. Steps (1) to (3) are steps according to the method of manufacturing the porous nickel-aluminum alloy catalyst described above with reference to FIGS. 1 to 3E, and thus redundant descriptions will be omitted.

Step (4) is a step of drying the prepared porous nickel-aluminum alloy catalyst, mechanically pulverizing it to collect it in the form of a powder, and mixing the powder in a solvent together with a carbon conductor and a binder to prepare a catalyst ink. .

The carbon conductor may be a material added to prepare the porous nickel aluminum alloy catalyst as an ink-type catalyst, and may include a material added to facilitate the transfer of electrons from the electrode of the electrochemical system to the catalyst.

The binder may include an organic compound that enables the alloy catalyst to be stably applied on the surface of the electrode, and the material is not particularly limited. The binder is, for example, polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), polyamide-imide (PAI), polytetrafluoroethylene. , PTFE), and Nafion. In the present invention, PVDF was used as the binder.

The solvent may be a solvent provided to ink the alloy catalyst. The solvent, for example, methanol (methanol), ethanol (ethanol) isopropanol (isopropanol), ethyl acetate (ethyl acetate), ethyl lactate (ethyl lactate), and at least NMP (N-methyl-2-pyrrolydine) It can contain one. In the present invention, NMP was used as the solvent.

The carbon conductor, the binder, and the porous nickel-aluminum alloy catalyst were mixed in a ratio of about 1:1:5, but the ratio of the porous nickel-aluminum alloy catalyst may be variously changed according to embodiments.

In step (5), the catalyst ink may be drop-coated on a nickel substrate and dried at room temperature. Depending on the embodiments, the amount of drop-coating the catalyst ink may be variously changed.

Next, the results of the cyclic current-voltage method for the hydrogen generation reaction in the electrode coated with the porous nickel aluminum alloy catalyst prepared through the above steps (1) to (5) are analyzed.

The porous nickel-aluminum alloy catalyst of the second embodiment obtained by selectively etching the nickel-aluminum alloy catalyst of the second experimental example containing nickel in a composition ratio of about 10 atomic% was prepared as a catalyst ink. As an example, an electrode coated with a catalyst layer was prepared by varying the drop-coating amount of the catalyst ink. The amount of drop-coating was about 1.65 mg/cm ² , about 5 mg/cm ² , and about 10 mg/cm ² for each electrode. As a plate type example for comparison, a porous nickel aluminum alloy plate catalyst of ^{about 100 mg/cm 2 not prepared in the form of ink was used.}

It can be seen that in the case where the drop-coating amount is about 10 mg/cm ² and the plate-type embodiment, an increase in the magnitude of the current density versus voltage is similar. That is, it can be seen that when the porous nickel-aluminum alloy catalyst is prepared as a catalyst ink, the catalyst performance is similar to that of the plate-type embodiment even in an amount corresponding to about 10% of the amount of the plate-type catalyst. This is analyzed that even when the porous nickel-aluminum alloy catalyst was prepared in the form of ink, the nanostructure supported on the surface had an effect on the catalyst performance improvement.

When a porous nickel-aluminum alloy catalyst is prepared in the form of ink and coated on a large-area electrode, the amount of catalyst required can be reduced. As described above, by thermodynamically controlling the microstructures of nickel and aluminum, a catalyst having excellent catalytic properties for hydrogen generation reaction can be prepared. Accordingly, it is possible to provide a porous transition metal catalyst with low cost bridge efficiency.

The electrode coated with the porous transition metal alloy catalyst can be applied as an electrode of an oxidation and reduction electrochemical system including a hydrogen generation reaction, an oxygen generation reaction, a chlorine generation reaction, a nitrogen reduction reaction, and a carbon dioxide reduction reaction.

The present invention is not limited by the above-described embodiments and the accompanying drawings, but is intended to be limited by the appended claims. Therefore, various types of substitutions, modifications, and changes will be possible by those of ordinary skill in the art within the scope not departing from the technical spirit of the present invention described in the claims, and this also belongs to the scope of the present invention. something to do.

100: electrochemical system
110: reactor
120: aqueous electrolyte solution
130: first electrode
140: second electrode
150: catalyst layer
160: power supply

Claims (13)

Mixing the first metal and the second metal and heating to a temperature equal to or higher than the melting point to form a transition metal molten alloy;
Cooling the transition metal molten alloy to form a transition metal alloy;
And selectively etching the transition metal alloy to remove the first metal,
The first metal includes aluminum (Al),
The second metal includes at least one of titanium (Ti), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), and molybdenum (Mo),
The transition metal alloy includes a primary phase and a eutectic phase,
In the step of removing the first metal, the second metal atoms remaining after the first metal is removed from the process form a nanostructure on the surface of the supernormal phase, of a porous transition metal alloy catalyst for hydrogen generation reaction Manufacturing method.
delete The method of claim 1,
The second metal is nickel (Ni),
The method of the transition metal alloys are Al ₃ Ni second top (primary phase), and Al ₃ Ni, Al and the process of hydrogen generating reaction porous transition metal alloy catalyst containing (eutectic phase).
The method of claim 3,
The nanostructure is a method of producing a porous transition metal alloy catalyst for hydrogen generation reaction in which aluminum is removed from the process and remaining nickel atoms are present in the form of nickel metal or nickel oxide.
The method of claim 3,
The step of forming the transition metal molten alloy,
Heating the first and second metals at a temperature of 1200° C. or higher to completely melt the first and second metals.
As a porous transition metal alloy catalyst for hydrogen generation reaction by selectively etching a transition metal alloy including a primary phase and a eutectic phase,
The transition metal alloy includes a first metal and a second metal,
It is supported on the surface of the supernormal, and includes a nanostructure made of the second metal,
The first metal includes aluminum (Al),
The second metal includes nickel (Ni),
The supernormal phase has a dendrite or globular structure,
The nanostructure is a porous transition metal alloy catalyst for hydrogen generation reaction having the form of nanowires or nanoparticles.
The method of claim 6,
The transition metal alloy is a porous transition metal alloy catalyst for hydrogen generation reaction in which the content of nickel is more than 0 atomic% and 25 atomic% or less with respect to the total 100 atomic% of nickel and aluminum.
The method of claim 7,
The transition metal alloy is a porous transition metal alloy catalyst for hydrogen generation reaction in which the content of nickel is 5 atomic% or more and 15 atomic% or less with respect to 100 atomic% of nickel and aluminum.
The method of claim 6,
The super-crystalline _{phase is made of Al 3} Ni, and the process phase is a porous transition metal alloy catalyst for hydrogen generation reaction consisting of _{Al 3 Ni and Al.}
delete The method of claim 6,
The average diameter of the nanostructure is 5% to 20% of the average diameter of the crystal grains constituting the supernormal porous transition metal alloy catalyst for hydrogen generation reaction.
The method of claim 6,
The average diameter of the nanostructure is in the range of 10 nm to 50 nm for hydrogen generation reaction porous transition metal alloy catalyst.
A reactor containing an aqueous electrolyte solution;
First and second electrodes at least partially immersed in the aqueous electrolyte solution;
A catalyst layer coated on the surface of the first electrode and comprising a porous transition metal alloy catalyst for hydrogen generation reaction according to any one of claims 6 to 9, 11, and 12;
An electrochemical system comprising a power supply for applying an electrical signal to the first and second electrodes.

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