KR20210029605A - Electrode for water electrolysis comprising catalyst with three-dimensional dendrite structure, method for preparing same and water electrolyzer comprising same - Google Patents

Abstract

The present invention relates to a water electrolysis electrode including catalyst having a three-dimensional (3D) dendrite structure, which has a lower overvoltage and excellent catalyst activity, a manufacturing method thereof, a water electrolysis apparatus including the same. According to the present invention, the water electrolysis electrode comprises a porous catalyst layer including a complex metal body having a 3D dendrite structure, and an electrode substrate. Moreover, a method for manufacturing the water electrolysis electrode comprises a step of immersing the electrode substrate in an electrolyte containing a metal precursor and a phosphorus (P) precursor, and applying a current density to perform electrodeposition. The water electrolysis apparatus comprises the water electrolysis electrode as a negative electrode.

Description

TECHNICAL FIELD [ELECTRODE FOR WATER ELECTROLYSIS COMPRISING CATALYST WITH THREE-DIMENSIONAL DENDRITE STRUCTURE, METHOD FOR PREPARING SAME AND WATER ELECTROLYZER COMPRISING SAME}

The present invention relates to a water electrolytic electrode comprising a catalyst having a three-dimensional dendrite structure, a method of manufacturing the same, and a water electrolysis apparatus including the same. Specifically, it relates to a water electrolytic electrode having excellent efficiency in a hydrogen generation reaction, a method of manufacturing the same, and a water electrolysis apparatus including the same.

The demand for renewable energy is increasing due to the acceleration of global warming caused by the use of carbon-based energy storage devices. Accordingly, a method of electrochemically producing hydrogen using water electrolysis has been extensively studied, and the produced hydrogen can be used in fuel cells or direct combustion engines.

Electrochemical water decomposition occurs in two reactions, the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Ideally, water electrolysis can proceed when a voltage of 1.23V is applied. However, in practice, in order to produce hydrogen through water electrolysis due to the influence of surface resistance, an overvoltage of 1.23V or more must be applied. Accordingly, in order to improve water electrolysis efficiency by reducing electric energy cost, since overvoltage for water electrolysis must be reduced, catalysts capable of reducing overvoltage in hydrogen generation reaction and oxygen generation reaction are required, respectively.

The catalytic performance in water decomposition needs to be evaluated in terms of hydrogen generation and oxygen generation. In terms of hydrogen generation reaction, a catalyst based on a noble metal such as Pt is the most effective.

However, the Pt-based catalysts are very expensive and scarce, and a material to replace them is required. Accordingly, transition metal sulfides, carbides, and phosphides that can be used as hydrogen generation reaction catalysts have been widely studied as highly active and rich catalysts. However, since the catalytic activity is not as good as the Pt-based catalysts, it is necessary to change the composition of the catalytic material in order to improve the catalytic activity.

In addition, an electrode that is advantageous for catalytic reaction requires a structure that enables an efficient reaction and has a large surface area. Since the hydrogen generation reaction is a gas generation reaction, the hydrogen gas generated by water electrolysis must be quickly removed from the electrode because hydrogen bubbles on the electrode surface block the active site of the hydrogen generation reaction to reduce the amount of hydrogen generation reaction. Accordingly, the porous three-dimensional (3D) structure is regarded as an ideal electrode structure that is advantageous for hydrogen generation reaction because many pores generate a large surface area. Therefore, it is necessary to develop a material having a wider surface area and high catalytic activity.

The technical problem to be achieved by the present invention is to provide a water electrolytic electrode including a catalyst layer having an inexpensive and excellent catalytic activity, a method of manufacturing the same, and a water electrolysis device including the same.

According to an aspect of the present invention, the electrode substrate; And a porous catalyst layer positioned on the electrode substrate, wherein the porous catalyst layer includes Cu; P; And at least one of Co, Mn, Fe, Ni, W, and Mo; and a metal composite, wherein the metal composite provides a water electrolytic electrode having a three-dimensional dendrite structure.

According to another aspect of the present invention, a Cu precursor; P precursor; And Co, Mn, Fe, Ni, W and Mo at least one precursor; forming an electrolyte solution containing; Immersing an electrode substrate in the electrolyte solution; And Cu on the surface of the electrode substrate by applying a current to the immersed electrode substrate. P; And at least one of Co, Mn, Fe, Ni, W, and Mo; forming a porous catalyst layer by electrodeposition.

According to another aspect of the present invention, there is provided a water electrolysis device comprising the electrolytic electrode according to the present invention as a cathode.

The water electrolytic electrode according to an exemplary embodiment of the present invention includes a material having high catalytic activity, and the surface area of the catalyst layer is increased, so that it may have excellent catalytic efficiency. The method of manufacturing a water-receiving electrode according to another embodiment of the present invention can simply control the composition of the catalyst, and when the water-receiving electrode according to an embodiment of the present invention is introduced into the water-electrolytic device, low resistance and overvoltage It can increase the water electrolysis efficiency.

1 is a view schematically showing an electrodeposition step in a method of manufacturing a water-electrolytic electrode according to an exemplary embodiment of the present invention.
2A to 2E are scanning electron microscope (SEM) photographs at 1000 and 100,000 magnifications (inserted drawings) of the surface of the catalyst layer of the water-electrolytic electrode prepared in Examples 1 to 3, Comparative Examples 1 and 2, respectively. .
3A to 3D are SEM photographs at 1000 magnification of cross-sections of the catalyst layer of the water-electrolytic electrodes prepared in Examples 1 to 3 and Comparative Example 1, respectively.
4 is a transmission electron microscope (TEM) photograph at 1,000,000 magnification of a catalyst layer of a water electrolytic electrode prepared in Example 2. FIG.
5A to 5C are graphs of EDS spectra of Cu, Co, and P of the catalyst layer of the water-receiving electrode prepared in Example 2, respectively.
6 is a graph showing the XRD pattern of the catalyst layer of the water-electrolytic electrode prepared in Example 2 and Comparative Example 1. FIG.
7 is a graph showing the atomic content in the catalyst layer of the water-electrolytic electrode prepared in Examples 1 to 3 and Comparative Example 1.
8 is a graph showing the pore area ratio of the electrolytic electrode prepared in Examples 1 to 3 and Comparative Example 1 to the surface of the catalyst layer and the number of pores per unit area of the surface of the catalyst layer of the electrolytic electrode.
9 is a graph showing the catalyst load per unit area of the catalyst layer of the water-electrolytic electrode prepared in Examples 1 to 3 and Comparative Example 1. FIG.
10A to 10C are respective XPS patterns of Cu 2p, Co 2p, and P 2p of the catalyst layer of the water-electrolytic electrode prepared in Example 2 and Comparative Example 1. FIG.
11 is a graph showing LSV polarization curves of the electrolytic electrodes prepared in Examples 1 to 3, Comparative Example 1, Comparative Example 2, and Reference Example 1. FIG.
12A to 12D are graphs showing cyclic voltammetry curves of current versus voltage of the water-receiving electrodes prepared in Examples 1 to 3 and Comparative Example 1 and current curves according to scanning speed in the non-Faraday region to be.
13 is a graph showing the electrochemical active surface area (ECSA) and overvoltage of the water-receiving electrode prepared in Examples 1 to 3 and Comparative Example 1. FIG.
14 is a graph showing the electrochemical impedance spectrum of the electrolytic electrode prepared in Examples 1 to 3 and Comparative Example 1.
15 is a graph showing _{the charge transfer resistance (R ct} ) and the surface area correction charge transfer resistance (R _cct ) of the catalyst layer of the water-receiving electrode prepared in Examples 1 to 3 and Comparative Example 1.
16 is a graph showing a voltage curve over time measured by applying a constant current ^{of 10 mA/cm 2} to the water-receiving electrode prepared in Example 2. FIG.

In the present specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

Hereinafter, the present invention will be described in more detail.

A water electrolytic electrode according to an aspect of the present invention includes an electrode substrate; And a porous catalyst layer positioned on the electrode substrate, wherein the porous catalyst layer includes Cu; P; And at least one of Co, Mn, Fe, Ni, W, and Mo; and a metal complex, wherein the metal complex has a three-dimensional dendrite structure.

In the present specification, the term "stereo-dendrite structure" is a crystal form, also called a dendritic crystal, and corresponds to a form in which a plurality of branches are located on a central stem. Since the porous catalyst layer includes a metal composite having a three-dimensional dendrite structure, the surface area of the catalyst layer may be increased, thereby improving catalyst efficiency.

According to an exemplary embodiment of the present invention, the porous catalyst layer may have a form in which the metal composite and pores exist therebetween. The metal composite is, for example, Cu; Co; And a metal composite of P.

When a water electrolytic electrode including a porous catalyst layer according to an exemplary embodiment of the present invention is introduced into a water electrolysis device, oxygen or hydrogen gas generated by the water electrolysis reaction is easily transferred from the surface of the porous catalyst, so that the surface area of the electrolyte and the catalyst interface And by relatively increasing the active point may not significantly lower the reaction rate.

According to an exemplary embodiment of the present invention, the electrode substrate may include at least one of Ni, SUS (Stainless Steel), Ti, Au, carbon cloth, and carbon paper. Preferably, the electrode substrate may include Ni.

According to an exemplary embodiment of the present invention, the porous catalyst layer may have a thickness of 10 μm to 20 μm, 12 μm to 20 μm, or 12 μm to 17 μm. When the thickness of the porous catalyst layer has a value within the above numerical range, the electrochemical effect may be excellent because the catalyst layer has excellent wettability while providing a large catalyst surface area.

According to an exemplary embodiment of the present invention, the porous catalyst layer may have an average pore diameter of 5 μm to 10 μm, 6 μm to 10 μm, or 6 μm to 9 μm. When the average diameter of the pores of the porous catalyst layer is within the above numerical range, hydrogen gas generated on the catalyst surface can be rapidly removed from the catalyst surface, and diffusion of the electrolyte can be facilitated, so that the reaction speed of the electrode is increased. It can be excellent.

According to an exemplary embodiment of the present invention, the total cross-sectional area of the pores formed on the surface of the porous catalyst layer may be 35% to 55%, or 38% to 51% of the total surface area of the catalyst layer.

According to an exemplary embodiment of the present invention, the number of pores per unit area of the surface of the porous catalyst layer may be 5500 pieces/mm ² to 8500 pieces/mm ² . Specifically, the "porous catalyst layer surface" means a surface opposite to the surface of the porous catalyst layer adjacent to the electrode substrate. When the number of pores per unit area of the surface of the porous catalyst layer within the above numerical range or the surface area value of the pores of the surface of the porous catalyst layer is provided, a large catalyst surface area is provided to provide many catalytic active points while reducing the transfer resistance of reactants and products. Can increase performance.

According to an exemplary embodiment of the present invention, the metal composite included in the porous catalyst layer has _{a formula of Cu b} M _100-ab P a, wherein M is at least one of Co, Mn, Fe, Ni, W, and Mo. , 1≤a≤5 and 40≤b≤50, 1.5≤a≤4 and 41≤b≤48 or 1.8≤a≤3.6 and 42≤b≤46.4 may be satisfied.

When the metal composite contains P within the above numerical range, the catalytic activity of the porous catalyst layer including the metal composite in the hydrogen generation reaction may be improved. Specifically, when the metal composite contains Cu in an amount within the above numerical range, the porous structure can be formed more firmly, and the electrochemically active surface area (ECSA) of the catalyst layer of the water electrolytic electrode is wide, so that it can have excellent catalytic activity. have.

When the metal composite contains Cu within the above numerical range, a three-dimensional dendrite structure of the metal composite may be formed. Cu forms most of the stem of the three-dimensional dendrite structure, and when Cu is included in an amount within the above numerical range, the three-dimensional dendrite structure can be formed more clearly.

According to an exemplary embodiment of the present invention, most of the Cu may be located on the stem of the three-dimensional dendrite structure, and most of the one or more of Co, Mn, Fe, Ni, W, and Mo may be located in a branch that is a peripheral portion of the stem. . This may be because when forming the metal composite layer of the three-dimensional dendrite structure, Cu first forms a stem, and then at least one of Co, Mn, Fe, Ni, W, and Mo forms branches.

According to another aspect of the present invention, the water electrolytic electrode is a Cu precursor; P precursor; And Co, Mn, Fe, Ni, W and Mo at least one precursor; forming an electrolyte solution containing; Immersing an electrode substrate in the electrolyte solution; And Cu on the surface of the electrode substrate by applying a current to the immersed electrode substrate. P; And at least one of Co, Mn, Fe, Ni, W, and Mo; forming a porous catalyst layer by electrodeposition.

According to an exemplary embodiment of the present invention, the Cu precursor; And a precursor of at least one of Co, Mn, Fe, Ni, W and Mo; each may independently be a hydrochloride, nitrate, sulfate, or acetate salt of these metals. In particular a Cu precursor; And Co, Mn, Fe, Ni, W, and one or more of the precursors of Mo; It may be preferable that it is a sulfate of these metals.

According to an exemplary embodiment of the present invention, the electrolyte may further include a solvent. The solvent may be an aqueous solvent, specifically distilled water, or an organic solvent such as ethanol, methanol, acetone, or ethylene glycol.

According to an exemplary embodiment of the present invention, the P precursor may be disodium phosphate.

According to an exemplary embodiment of the present invention, the P precursor is 0.1 to 15 parts by weight, 1 to 10 parts by weight, 2.5 to 10 parts by weight based on 100 parts by weight of one or more precursors of Co, Mn, Fe, Ni, W and Mo. It may be included in the electrolyte in an amount of 2.5 to 7.5 parts by weight or 2.5 to 7.5 parts by weight. When the electrolyte contains a P precursor within the above content range, the catalyst layer has a large number of pores and thus has a wide catalyst surface area and a low overvoltage, so that catalyst efficiency may be excellent.

According to an exemplary embodiment of the present invention, the Cu precursor is 5 to 20 parts by weight, 5 to 15 parts by weight, or 7 to 11 parts by weight based on 100 parts by weight of one or more precursors among the Co, Mn, Fe, Ni, W and Mo It may be included in the electrolyte in an amount by weight. When the electrolyte contains a Cu precursor within the above content range, the resulting metal composite may firmly form a dendrite structure.

According to an exemplary embodiment of the present invention, the electrode substrate is immersed in the electrolyte solution, and a porous catalyst layer is formed on the surface of the electrode substrate by electrodeposition. That is, Cu; P; And at least one of Co, Mn, Fe, Ni, W, and Mo; to be electrodeposited.

Electrodeposition means electrical vapor deposition, and is also known as electrolytic plating. The electrodeposition may be performed by a two-electrode system using the electrode substrate as a working electrode.

According to an exemplary embodiment of the present invention, the electrodepositing is performed on the immersed electrode substrate 1 A/cm ² to 3 A/cm ² , 1 A/cm ² to 2.5 A/cm ² or 1 A/cm ² to 2 It may be performed by applying a current for 5 seconds to 30 seconds, 10 seconds to 25 seconds, or 15 seconds to 20 seconds at a current density of A/cm ^2. When electrodeposition is performed within the current density range and the time range, the occurrence of side reactions such as electrolysis of the solvent is prevented, and the catalyst layer can be formed smoothly.

According to an exemplary embodiment of the present invention, the pores of the porous catalyst layer may be formed by hydrogen bubbles generated in the electrodeposition step.

A schematic diagram of the electrodeposition step according to an exemplary embodiment of the present invention is shown in FIG. 1. Electrodeposition starts when the electrode substrate is immersed in the electrolyte and a current is applied to the electrode substrate. According to an exemplary embodiment of the present invention, when electrodeposition begins, the following four reactions proceed on the surface of the electrode substrate.

^{(1) Co 2+ + 2e -} -> Co

^{(2) Cu 2+ + 2e -} -> Cu

^{_{(3) H 2 PO 2 -}} + 2H + + e - -> P + 2H 2 O

^{(4) 2H + + 2e -} -> H 2

Referring to FIG. 1, in the electrodeposition step along with the above reaction, the metal composite is electrodeposited, and hydrogen generation reaction proceeds, thereby forming a catalyst layer having a porous structure. That is, the more hydrogen is generated, the larger and more pores may be formed in the catalyst layer. The amount of hydrogen generated may increase as the concentration of hydrogen ions in the electrolyte solution increases, the intensity of the current applied to the electrode substrate in the electrodeposition step increases, and the length of time for applying the current increases.

According to an exemplary embodiment of the present invention, as the electrodeposition occurs mostly earlier than the electrodeposition of at least one of Co, Mn, Fe, Ni, W, and Mo in the form of a stem, the three-dimensional dendrite structure of the formed catalyst layer is later It will be able to serve as a support that can be stably maintained. Most of one or more of Co, Mn, Fe, Ni, W, and Mo around the formed Cu stem are formed in a branched form to form a three-dimensional dendrite structure.

The method of manufacturing a water electrolytic electrode according to an exemplary embodiment of the present invention may further include a step of drying after the electrodepositing step. Since the electrode after the electrodeposition step corresponds to a state in which the electrolyte is wet, a predetermined drying process may be required.

According to an exemplary embodiment of the present invention, the drying may be performed at a temperature of 60°C to 80°C or 65°C to 75°C for 50 to 70 minutes or 55 to 65 minutes.

A water electrolytic device according to another aspect of the present invention includes the electrolytic electrode according to the present invention as a cathode.

According to an exemplary embodiment of the present invention, the water electrolysis device may include the water electrolysis electrode as a hydrogen generating electrode, that is, a cathode. Such a water electrolysis device may be an alkaline water electrolysis device, and in particular, may be an anion exchange membrane water electrolysis device. As the oxygen generating electrode, a metal or alloy such as Ni, Co, Fe, and Cu may be used.

Hereinafter, in order to describe the present invention in detail, an exemplary embodiment will be described in detail. However, the exemplary embodiments according to the present invention may be modified into various other forms, and the scope of the present invention is not construed as being limited to the exemplary embodiments described below. The exemplary embodiments of the present specification are provided to more completely describe the present invention to those of ordinary skill in the art.

Example 1

In 200 ml of distilled water, CuSO ₄ (SIGMA-ALDRICH, 98.0%) is 0.04M, CoSO ₄ (Junsei, 99.0%) is 0.4 M, NaCl (SAMCHUN, 99.5%) is 1M, and H ₂ SO ₄ (SAMCHUN) is an electrolyte. , 95.0%) was 1M, NaH ₂ PO ₂ (SIGMA-ALDRICH, 99%) was added to 0.01M and stirred to prepare an electrolyte. A stainless steel foil (type 304, 0.025 mm, Alfa Aesar) as an electrode substrate was prepared as a specimen having a size of 0.5 cm * 0.5 cm, and then subjected to mechanical polishing, followed by ultrasonic treatment in acetone, ethanol, and deionized water for 15 minutes to degrease. The degreased stainless steel foil was immersed in the prepared electrolyte with a working electrode, and a platinum mesh of the same standard as the stainless steel foil was used as the counter electrode, and a two-electrode system was constructed in which the distance between the electrodes was 1 cm. ^{Electrodeposition was performed by applying a current density of 2 A/cm 2} with a constant current to the two-electrode system for 20 seconds using a potentiometer (WONATECH, ZIVE MP5). The electrode substrate on which electrodeposition was performed was washed with deionized water and dried in a convection oven at 70° C. for 60 minutes to prepare a water electrolytic electrode.

Example 2

A water electrolytic electrode was manufactured in the same manner as in Example 1, except that _{NaH 2} PO _{2 (SIGMA-ALDRICH, 99%) was added to be 0.02M.}

Example 3

A water electrolytic electrode was manufactured in the same manner as in Example 1, except that _{NaH 2} PO _{2 (SIGMA-ALDRICH, 99%) was added to be 0.03M.}

Comparative Example 1

In 200 ml of distilled water, CuSO ₄ (SIGMA-ALDRICH, 98.0%) is 0.04M, CoSO ₄ (Junsei, 99.0%) is 0.4M, NaCl (SAMCHUN, 99.5%) is 1M, H ₂ SO ₄ (SAMCHUN, 95.0%) ) Was added to 1M and stirred to prepare an electrolytic solution in the same manner as in Example 1, except that an electrolytic solution was prepared.

Comparative Example 2

_{The same as in Example 1, except that CuSO 4} (SIGMA-ALDRICH, 98.0%) was added so that 0.04M, H ₂ SO ₄ (SAMCHUN, 95.0%) was 1M to 200 ml of distilled water, and stirred to prepare an electrolyte. A water electrolytic electrode was manufactured by the method.

Comparative Example 3

_{Except that CoSO 4} (Junsei, 99.0%) is 0.4M, NaCl (SAMCHUN, 99.5%) is 1M, and H ₂ SO ₄ (SAMCHUN, 95.0%) is 1M and stirred to prepare an electrolyte solution to 200 ml of distilled water. Then, a water electrolytic electrode was manufactured in the same manner as in Example 1.

Reference Example 1

A stainless steel foil (type 304, 0.025 mm, Alfa Aesar) was prepared as a specimen having a size of 0.5cm * 0.5cm, and then commercial Pt/C (40% by weight) was dispersed on the specimen to prepare a water electrolytic electrode.

Observation of the surface and cross section of the catalyst layer

Scanning electron microscope (SEM) pictures were taken of the surface and cross-section of the catalyst layer of the water-electrolytic electrode prepared in Examples 1 to 3, Comparative Example 1 and Comparative Example 2 using an electron microscope (JEOL, JSM-7001F).

2A to 2E correspond to SEM photographs of 1,000 magnification or 100,000 magnification (inset drawing) of the surface of the catalyst layer of the water-electrolytic electrode prepared in Examples 1 to 3, Comparative Examples 1 and 2; Figure 2e does not show the inset.

Referring to FIGS. 2A to 2E, it can be seen that the catalyst layer of the water electrolytic electrode prepared in Examples 1 to 3 is porous. On the other hand, the surfaces of the water-electrolytic electrodes prepared in Comparative Example 1 without using a P precursor and Comparative Example 2 without using a Co and P precursor were shown in Examples 1 to 3 as shown in FIGS. 2D and 2E. It can be seen that the number of pores is smaller than the surface of the prepared electrolytic electrode. That is, it can be seen that the water electrolytic electrode according to the present invention has a large surface area of the catalyst due to the large number of pores having an appropriate size, and has high catalytic activity due to the large number of reaction sites for hydrogen generation reaction.

3A to 3D correspond to SEM photographs at 1000 magnification of cross-sections of the catalyst layers of the water-electrolytic electrodes prepared in Examples 1 to 3 and Comparative Example 1.

Referring to FIGS. 3A to 3D, it can be seen that the thickness of the catalyst layer of the water-receiving electrode prepared in Examples 1 to 3 decreases as the concentration of the P precursor in the electrolyte solution increases. This may be because the higher the concentration of the P precursor, the more actively the hydrogen generation reaction occurs, and accordingly, the thickness of the catalyst layer decreases as more electrons are consumed for hydrogen generation instead of electrodeposition.

Observation and analysis of dendrite structure and components of metal composites

A transmission electron microscope (TEM) photograph was taken at about 100,000 magnification using a transmission electron microscope (JEOL, JEM2100F) of the catalyst layer of the water electrolytic electrode prepared in Example 2, and this is shown in FIG. 4.

Referring to FIG. 4, it can be seen that the catalyst layer of the water-electrolytic electrode prepared in Example 2 has a three-dimensional dendrite structure. Specifically, it can be seen that the three-dimensional dendrite structure has a stem portion and a twig-shaped stem periphery.

In addition, by using energy dispersive X-ray spectroscopy (EDS) using an energy dispersive spectrometer (Oxford Aztec, Energy X-Max 80mm ² ), each element based on the solid line shown in FIG. 4 of the catalyst layer of the water electrolytic electrode prepared in Example 2 EDS spectra are shown in Figs. 5a to 5c.

5A to 5C, it can be seen that Cu, Co, and P are distributed in the metal composite included in the catalyst layer of the water-electrolytic electrode prepared in Example 2. Specifically, in the three-dimensional dendrite structure identified in FIG. 4, it can be seen that Cu is generally present at the stem side, Co is generally present at the stem periphery, and P is evenly distributed. That is, a Cu stem is formed at the initial stage of electrodeposition, and as the electrodeposition proceeds, after the Cu ions near the electrode substrate are depleted, the formation of the Co stem surrounds the Cu stem. As a result, it can be seen that a core-shall structure having a relatively Cu-rich stem and a Co-rich stem periphery was formed. Accordingly, it can be seen that the stem formation rate of Cu is relatively higher than that of Co, and it can be seen that P is uniformly distributed in the catalyst layer regardless of the reduction of Cu and Co.

Using X-ray diffraction spectroscopy (XRD) with an X-ray diffraction analyzer (Bruker, D8 Advance) device, each XRD pattern of the catalyst layer of the water-electrolytic electrode prepared in Example 2 and Comparative Example 1 was derived, and it is shown in FIG. I got it.

Referring to FIG. 6, although the catalyst layer of the water electrolytic electrode prepared in Example 2 has a composition of Cu-Co-P, the peak of P does not appear in the XRD pattern. That is, it can be seen that P does not affect the crystal structure of the metal composite of Cu-Co-P. On the other hand, when compared with the XRD pattern of the catalyst layer of the water-receiving electrode prepared in Comparative Example 1, it can be seen that the Cu peak has a stronger intensity and the Co peak has a lower intensity. That is, it can be seen that the content of Cu is higher than that of Co in the catalyst layer of the water-receiving electrode of Example 2.

The atomic content in the catalyst layer of the water-electrolytic electrode prepared in Examples 1 to 3 and Comparative Example 1 was measured under 1000 magnification conditions using an ^{energy dispersive spectrometer (Oxford Aztec, Energy X-Max 80 mm 2 ), and each} The atomic contents of Co, Cu, and P in the catalyst layer are shown in FIG. 7.

Referring to FIG. 7, it can be seen that as the concentration of the P precursor in the electrolyte solution increases, the content of P and Cu in the catalyst layer increases, and the content of Co decreases. This means that the higher the concentration of the P precursor in the electrolyte, the lower the Cu reduction overvoltage, so that the reduction of Cu occurs more actively and the electrodeposition speed of Cu increases.

The ratio of the pore area to the total area of the surface of the catalyst layer and the number of pores per unit area

From the SEM photographs at 1000 magnification of the surface of the catalyst layer of the water-receiving electrode prepared in Examples 1 to 3 and Comparative Example 1, the sum of the areas of the pores on the surface of the catalyst layer and the number of pores were obtained, respectively, with respect to the total area of the surface of the catalyst layer. I did. By dividing this by the total area of the surface of the catalyst layer, the ratio (%) of the area of the pores to the area of the surface of the catalyst layer and the ^{number of pores per unit area (mm 2} ) of the surface of the catalyst layer were calculated, and are shown in FIG. 8.

Referring to FIG. 8, it can be seen that the ratio of the pore area to the surface area of the electrolytic electrodes prepared in Examples 1 to 3 and the number of surface pores per unit area are higher than those of the electrolytic electrodes prepared in Comparative Example 1. That is, it can be seen that the area ratio of the pores on the surface of the catalyst layer of the electrolytic electrode prepared in Examples 1 to 3 is greater than the area ratio of the pores on the surface of the catalyst layer of the electrolytic electrode prepared in Comparative Example 1. It can be seen that the catalytic activity will also be excellent because the surface area is large and the catalytic activity point is large.

Catalyst load per unit area of catalyst bed

Using a mass spectrometric balance (METTLER TOLEDO, M: 204/01), the weight of a stainless steel foil (type 304, 0.025 mm, Alfa Aesar) specimen was measured, and in Examples 1 to 3 and Comparative Example 1 The weight of the prepared electrolytic electrode was measured and the catalyst load was calculated by the difference, and the catalyst load per unit area was derived by dividing it by the surface area, and the results are shown in FIG. 9.

Referring to FIG. 9, it can be seen that the electrolytic electrode prepared in Examples 1 to 3 has a smaller catalyst load per unit area of the catalyst layer than the electrolytic electrode prepared in Comparative Example 1. As confirmed in FIG. 8, it can be seen that the pore area ratio and the number of pores increase, and the density of the catalyst layer decreases. Accordingly, the water electrolysis device using the water electrolysis electrode according to the present invention can be introduced into a device requiring portability because it has excellent catalyst efficiency and light weight.

XPS spectrum analysis of catalyst layer

Using an X-ray photoelectron spectroscopy (Thermo VG Scientific, K-alpha) device, XPS patterns were derived for each of Cu 2p, Co 2p and P 2p of the catalyst layer of the water electrolytic electrode prepared in Example 2 and Comparative Example 1 And it is shown in Figures 10a to 10c.

10A and 10B, the peak position of Cu 2p was changed from 933.0 eV of Comparative Example 1 to 932.7 eV of Example 2, and the peak position of Co 2p was changed from 778.25 eV of Comparative Example 1 to 778.55 of Example 2. It can be confirmed that it has been changed to eV. This is because the binding energy of Cu and Co is shifted, and thus it can be seen that the catalytic activity is excellent.

In addition, referring to FIG. 10C, it can be seen that P is included in two forms of a P oxide and a P atom. Among them, the peak of the P atom is known to be 132.2 eV, but it can be seen that it appears at 130.0 eV in FIG. 10C. That is, P is introduced into the metal complex to change the electronic structure of the P atom, and accordingly, it can be seen that the catalytic activity is excellent.

Evaluation of electrochemical properties of catalyst bed

Using a potentiostat (Bio-Logic, VMP3), the water electrolytic electrodes prepared in Examples 1 to 3, Comparative Examples 1, 2 and Reference Example 1 were used as working electrodes, respectively, and Ag/AgCl ( 1M KCl) as a reference electrode, a graphite rod as a counter electrode, and a voltage in the range of -0.25V to 0V using a linear scanning method (LSV) at a scanning speed of 5 mV/s in a nitrogen saturated 1M KOH electrolyte. Added.

11 shows LSV polarization curves corresponding to the current density versus the applied voltage of the catalyst layers of the water-electrolytic electrodes prepared in Examples 1 to 3, Comparative Example 1, Comparative Example 2, and Reference Example 1.

Referring to FIG. 11, it can be seen that the overvoltage of the receiving electrode prepared in Examples 1 to 3 is lower than the overvoltage of the receiving electrode prepared in Comparative Examples 1 and 2. Specifically, in the case of Comparative Example 2 in which the catalyst layer of the water electrolytic electrode was composed of only Cu, it ^{exhibited a high overvoltage of 382 mV at 10 mA/cm 2} , and about 105 in the case of Comparative Example 1 in which the catalyst layer of the water electrolytic electrode was composed of Cu and Co. mV decreased, resulting in an overvoltage of 277 mV. On the other hand, in the case of Examples 1 to 3 in which the catalyst layer of the water electrolytic electrode was composed of Cu, Co, and P, the overvoltage was 154 mV, 139 mV, and 151 mV, respectively, which was smaller than that of the comparative example, and Example 2 was the smallest. Indicated overvoltage. That is, it can be seen that when Co is added to Cu, the overvoltage is reduced, and when P is added thereto, the overvoltage is further reduced.

For reference, the overvoltage value of Comparative Example 3 is 10 mA/cm ² At 371 mV, it has a value much higher than the overvoltage value of the catalyst layer of the water-electrolytic electrode prepared in Examples 1 to 3, about 139 to about 151 mA/cm ^2. That is, it can be seen that the overvoltage of the catalyst layer of the water-receiving electrode according to the present invention is lower than the overvoltage of the Co catalyst and has excellent electrochemical properties.

Meanwhile, using a potentiometer (Bio-Logic, VMP3) device, the water electrolytic electrodes prepared in Examples 1 to 3 and Comparative Example 1 were used as operating electrodes, and Ag/AgCl (1M KCl) was used as a reference electrode. The graphite rod is used as the counter electrode, and in an electrolyte solution of nitrogen saturated 1M KOH, the range is 0.14 V to 0.17 V at a scanning speed of 2.5 mV/s, 5 mV/s, 10 mV/s, 20 mV/s, or 40 mV/s. The current was measured by applying the internal voltage by cyclic voltammetry.

In addition, when voltage was applied by the cyclic voltammetry method, the maximum negative current and the maximum positive current were measured for each of the scanning speeds to show a curve of the current according to the scanning speed in the non-Faraday region.

12A to 12D show circulating voltage current curves of current versus voltage of the water-receiving electrodes prepared in Examples 1 to 3 and Comparative Example 1, and curves of current according to scanning speed in the non-Faraday region.

_{On the other hand, C dl} , that is, a double layer capacitance, can be obtained from a curve of a current according to a scanning speed in the non-Faraday region. Specifically, in the non-Faraday region, current data according to the scanning speed is linearly plotted to obtain a slope, and a C _dl value can be obtained as an absolute value of the slope. _{The C dl} values of the water-electrolytic electrodes prepared in Examples 1 to 3 and Comparative Example 1 are shown in Table 1 below.

Referring to FIGS. 12A to 12D, it can be seen that the electrolytic electrode prepared in Examples 1 to 3 has a larger double-layer capacitance than the electrolytic electrode prepared in Comparative Example 1.

In addition, the overvoltages of the electrolytic electrodes prepared in Examples 1 to 3 and Comparative Example 1 from FIG. 11 are shown in Tables 1 and 13 below. _{In addition, the C dl} value of each of the electrolytic electrodes and the electrochemical active surface area (ECSA) were calculated according to Equation 1 below, and the ECSA of the electrolytic electrodes prepared in Examples 1 to 3 and Comparative Example 1 were shown in Table 1 and Fig. It is shown together in 15.

[Equation 1]

ECSA = C _dl /C _s

(Cs is the planar capacitance of the metal surface, Cs=40 mf/cm ² )

division C _dl (mF) ECSA (cm ² ) Overvoltage (mV) Example 1 3.24 81 154 Example 2 3.50 87.5 138 Example 3 2.7 67.5 151 Comparative Example 1 1.65 41.25 277

Referring to Table 1 and FIG. 13, the catalyst layer of the electrolytic electrode prepared in Examples 1 to 3 has a higher ECSA value than the catalyst layer of the electrolytic electrode prepared in Comparative Example 1, and has a lower overvoltage value. You can check the point. That is, since the electrolytic electrode according to the present invention has high ECSA and low overvoltage, it has excellent electrochemical properties.

Resistance measurement and evaluation of the electrolytic electrode

The water electrolytic electrodes prepared in Examples 1 to 3 and Comparative Example 1 were used as a working electrode in 1M KOH electrolyte, respectively, and a potentiometer (Bio-Logic, VMP3) with a -150 mV coincidence using RHE as a reference electrode The impedance was measured using electrochemical impedance spectroscopy (EIS). 14 shows the electrochemical impedance spectra of the electrolytic electrodes prepared in Examples 1 to 3 and Comparative Example 1.

_{In addition, the charge transfer resistance (R ct} ) of the catalyst layer of the water-receiving electrode prepared in Examples 1 to 3 and Comparative Example 1 was obtained from FIG. 14. Specifically, after the measurement point of FIG. 14 is followed by a curve, the resistance value between the point where it meets the horizontal axis and the start point of the curve by extending it corresponds to _{R ct.} However, since a catalyst with a larger surface area appears to have _{a smaller R ct , R ct} may vary depending on the surface area. Therefore, the surface area corrected charge transfer resistance (R _cct ) corrected by multiplying the ECSA of Table 1 is shown in FIG. 15.

14 and 15, R _ct and R _{cct of the catalyst layer of the water electrolytic electrode prepared in Examples 1 to 3} were lower than _{R ct} and R cct of the catalyst layer of the water electrolytic electrode prepared in Comparative Example 1. You can see that it has a value. That is, since the low resistance means that current can flow more easily, it can be confirmed that the catalyst layer of the water-receiving electrode according to the present invention has excellent electrical properties.

Stability test

After immersing the water electrolytic electrode prepared in Example 2 in an electrolytic solution of nitrogen-saturated 1M KOH, ^{a constant current of 10 mA/cm 2} was applied with a potentiometer (Bio-Logic, VMP3) device to conduct a hydrogen generation experiment, and time The curve of the voltage according to is shown in FIG. 16.

Referring to FIG. 16, even when the electrolytic electrode prepared in Example 2 was used for the hydrogen generation reaction for 21600 seconds (that is, 6 hours), the overvoltage increased by only 4.3%, that is, the catalyst efficiency decreased by 4.3%. Specifically, the initial overvoltage was 138 mV, but only 6 mV increased to 144 mV after 6 hours of use, and it can be confirmed that the catalytic activity is maintained even when used for a long period of time, resulting in high stability.

In summary, the water electrolytic electrode according to the present invention includes a porous catalyst layer including a metal composite having a nanostructure in the form of a three-dimensional dendrite, and has a large surface area, excellent catalytic activity for hydrogen generation reaction, and electrical It can be seen that the resistance and overvoltage are low, and the electrochemical active surface area is large, so that excellent electrochemical properties are also retained.

Claims (15)

Electrode substrate; And
As a water electrolytic electrode comprising; a porous catalyst layer located on the electrode substrate,
The porous catalyst layer is Cu; P; And at least one of Co, Mn, Fe, Ni, W, and Mo; and a metal composite, wherein the metal composite has a three-dimensional dendrite structure.
The method of claim 1,
The electrode substrate is a water electrolytic electrode comprising at least one of Ni, SUS, Ti, Au, carbon cloth, and carbon paper.
The method of claim 1,
The porous catalyst layer is a water electrolytic electrode having a thickness of 10 μm to 20 μm.
The method of claim 1,
The porous catalyst layer is a water electrolytic electrode in which pores having an average diameter of 5 μm to 10 μm are formed.
The method of claim 1,
The porous catalyst layer is a water electrolytic electrode having a total cross-sectional area of the pores formed on the surface of 35% to 55% of the total surface area.
The method of claim 1,
The metal composite has _{a formula of Cu b} M _100-ab P a, wherein M is at least one of Co, Mn, Fe, Ni, W, and Mo, and satisfies 1≤a≤5 and 40≤b≤50 A water electrolytic electrode.
Cu precursor; P precursor; And Co, Mn, Fe, Ni, W and Mo at least one precursor; forming an electrolyte solution containing;
Immersing an electrode substrate in the electrolyte solution; And
Cu on the surface of the electrode substrate by applying a current to the immersed electrode substrate; P; And Co, Mn, Fe, Ni, W, and at least one of Mo; forming a porous catalyst layer by electrodeposition (electrodeposition); Containing
A method of manufacturing a water-electrolytic electrode according to any one of claims 1 to 6.
The method of claim 7,
The Cu precursor; And one or more precursors of Co, Mn, Fe, Ni, W, and Mo; are each independently a hydrochloride, nitrate, sulfate, or acetate salt of these metals.
The method of claim 7,
The P precursor is a method of manufacturing a water electrolytic electrode of disodium phosphate.
The method of claim 7,
The P precursor is included in the electrolyte in an amount of 0.1 to 15 parts by weight based on 100 parts by weight of one or more precursors of Co, Mn, Fe, Ni, W, and Mo, and the Cu precursor is the Co, Mn, Fe, A method of manufacturing a water electrolytic electrode contained in the electrolyte in an amount of 5 to 20 parts by weight based on 100 parts by weight of one or more precursors of Ni, W and Mo.
The method of claim 7,
Step 1 A / cm ² number of a current density of 1 to 3 A / cm ² is performed by applying a current for 5 seconds to 30 seconds electrolytic method of dipping the electrodes in the electrode substrate for the electro-deposition.
The method of claim 7,
The method of manufacturing a water electrolytic electrode, wherein the pores of the porous catalyst layer are formed by hydrogen bubbles generated in the electrodepositing step.
The method of claim 7,
The method of manufacturing a water electrolytic electrode further comprising the step of drying after the electrodepositing step.
The method of claim 13,
The drying step is a method of manufacturing a water electrolytic electrode to be carried out for 50 to 70 minutes at a temperature of 60 ℃ to 80 ℃.
A water electrolysis device comprising the water electrolytic electrode according to any one of claims 1 to 6 as a cathode.

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