KR102123840B1 - Unitizied bipolar plate with electrodes for water electolysis and water electrolyzer - Google Patents

Abstract

The present invention relates to a separating plate applied to the electrolytic stack, and by applying an electrolytic composite electrode-integrated separating plate directly formed with an electrode to a separating plate formed with a flow path, the electrolytic stack has a high efficiency (70 to 90%). The high current (0.6 to 1.0 A/cm ² ) operation is possible, and at the same time, the number of parts applied to the electrolytic stack is reduced, thereby simplifying the assembly of the electrolytic stack.

Description

Composite electrode-integrated separator for water electrolysis and electrolytic stack {UNITIZIED BIPOLAR PLATE WITH ELECTRODES FOR WATER ELECTOLYSIS AND WATER ELECTROLYZER}

The present invention relates to a separator plate applied to a water electrolyte stack, and more particularly, to a composite electrode separator having an electrode, a gas-liquid diffusion layer, an electrolyte solution, and a current collector function in a water electrolyte system.

In the field of hydrogen production technology, alkaline water electrolysis produces hydrogen and oxygen through electrochemical reaction of alkaline electrolyte (KOH), and chloro-alkali process (Chloro-) to produce caustic soda (NaOH) through electrolysis of salt water (NaCl) alkali process).

Among the water electrolysis technologies, the alkaline water electrolysis technology has been developed around the caustic soda process, and after the industry was formed based on the gap-type cell structure, large research and development other than technology development into zero-gap technology Did not proceed. Since the foam electrode is used in the zero-gap technology, the burden of gas-liquid diffusion is small, and the separator does not require any function other than applications such as inter-cell gas blocking and current collection.

The water electrolysis system consists of a stack that produces hydrogen, a balance of plants that supply and control and manage power, and a gas/liquid separator and a hydrogen storage tank. do.

In the conventional water electrolytic stack, as shown in FIG. 1, a single cell is designed that sequentially combines end plates, current collector plates, gaskets, mesh-type diffusion layers, electrodes, separators, membrane fixing rings, and cell frames in a symmetrical sequence. The stack was constructed by stacking as many as desired. As shown in FIG. 1, the zero-gap type uses two porous electrode plates (eg, Mesh, Foam, Lath etc.) to separate the separation membrane and the gap in order to overcome the problem of the parallel type designed by placing the previous electrode plates at regular intervals in the electrolyte. It is a structure that reduces cell resistance by not placing it, and hydrogen and oxygen gas generated at the electrode surface are discharged from the inside through the porous electrode body. Since there is no gap between the electrode and the separator, it has the advantage of reducing the electrolyte resistance and thus increasing the operating current density.

However, application of a porous electrode in the form of a mesh or foam can induce an increase in contact resistance with the separator or current collector, and also requires high mechanical rigidity of the separator in direct contact with the porous electrode. In addition, it is a weaker environment for the phenomenon of gas mixing of hydrogen and oxygen (the danger of explosion exists when the concentration of hydrogen in the oxygen gas is more than 4% by mixing hydrogen and oxygen gas). When stacking dozens to hundreds of cells, it is difficult to accurately match without a step difference between many parts, and thus assembly productivity is deteriorated.In addition, an increase in the number of stacked components causes volume increase, which decreases hydrogen production density and increases electrical contact resistance. The power consumption efficiency of the electrolytic stack decreases. Further, it leads to increased stack and system prices.

On the other hand, in the case of the PEM water electrolysis technology, in which the function of the separator is relatively important, the porous gas diffuser and the separator are important for proper penetration of the electrolyte and discharge of generated gas when applying the membrane electrode assembly technology. In PEM, it is important to reduce the electrical contact resistance between fuel and product 1) efficient material transfer and 2) separator-gas diffuser-electrode. . When a gap occurs, not only electrical conductivity but also ionic conductivity increases, leading to a decrease in performance. In addition, since the flow path is formed on the front surface of the separation plate (electrolyte is uniformly supplied to the electrode active area), it is difficult to directly coat and mold the electrode on the flow path without forming a reaction portion through etching. When there is no separation between the plate and the electrode during direct coating, mechanical resistance may be generated when gas is generated on the electrode surface, and electrical contact resistance may be increased. It is not suitable for membrane electrode assembly structure cells other than thin and flat separators.

Republic of Korea Registered Patent Publication No. 10-0405163

An object of the present invention, to solve the problems of the prior art, to provide a plurality of component parts of the electrode, gas-liquid diffusion layer, separation plate, current collector plate as a unit component integrated in one configuration.

In order to achieve the above object, the present invention is a plate-shaped conductive member; A flow path portion formed on one or both surfaces of the member; And it provides a composite electrode-integrated separation plate for electrolysis, including a reaction portion is formed with an electrode layer in the region except the flow path portion formed on one or both sides.

The flow path portion may be formed to a depth of 1 mm or less from the surface of the conductive member.

The electrode layer is a group consisting of nickel (Ni), Ni-Zn, NI-Zn-P, Ni-Fe-Zn, Ni-Fe-Zn-P and nickel-iron hydroxide ((Ni,Fe)(OH) ₂ ) It may be 1 or more selected from, more specifically, the anode (anode) in the electrode layer is Ni, Ni-Fe-Zn, Ni-Fe-Zn-P or nickel-iron hydroxide ((Ni,Fe) (OH) ₂ ), and may be Ni, Ni-Zn, or Ni-Zn-P, which is a cathode.

The electrode layer may have a specific surface area of 5 to 100 m ² /g and a pore size of 0.03 to 10 μm.

The electrode layer may have a vertically oriented porous structure.

In addition, the present invention provides a water electrolytic stack comprising one or two or more unit cells composed of the composite electrode-integrated separator for an electrolytic cell and a membrane.

According to the present invention as described above, by applying the electrolytic composite electrode-integrated separator plate directly formed electrode to the separator formed with a flow path to the electrolytic stack, high efficiency (70 to 90%) high current (0.6 to 1.0 A/ cm ² ) It has the effect of enabling driving.

In addition, it is possible to reduce the volume of the stack and the system by enabling high-efficiency, high-current operation.

In addition, the composite electrode separation plate performs the functions of an electrode, a gas-liquid diffusion layer, a separation plate, and a current collector, thereby reducing the number of parts applied to the electrolytic stack, thereby simplifying the assembly of the electrolytic stack.

1 is a block diagram showing a conventional electrolytic stack.
Figure 2 shows a front view (top image) and a side view (bottom image) of a composite electrode-integrated separator for electrolysis formed with an anode and an anode on both sides according to an embodiment of the present invention.
FIG. 3 shows a front view (top image) and a side view (bottom image) of a composite electrode-integrated separator plate for electrolysis in which an anode or an anode is formed only on one surface according to one embodiment of the present invention.
4 is a block diagram showing an example of a water-electrolyte stack to which a composite electrode-integrated separator for water electrolysis according to an embodiment of the present invention is applied.
Figure 5 shows the XRD structure analysis before and after selective leaching of Zn after plating in the cathode (Ni-Zn) of the composite electrode-integrated separator for water electrolysis according to one embodiment of the present invention.
6 shows an SEM microscopic image of the surface of the negative electrode (Ni-Zn) of the composite electrode-integrated separator for water electrolysis according to one embodiment of the present invention.
7 shows an SEM microscopic image of a cross section of a negative electrode (Ni-Zn) of a composite electrode-integrated separator for water electrolysis according to an embodiment of the present invention.
8 shows an SEM microscopic image of a cross-section of an anode (Ni-Fe-Zn) of a composite electrode-integrated separator for water electrolysis according to an embodiment of the present invention.
9 is a SEM microscopic image of a cross section of a cathode (Ni _0.85 Zn _0.1 P _0.05 ) and an anode (Ni _0.65 Fe _0.2 Zn _0.1 P _0.05 ) of a composite electrode-integrated separator for water electrolysis according to an embodiment of the present invention. It is shown.
10 shows the pore distribution of the negative electrode (Ni-Zn-P) and the positive electrode (Ni-Fe-Zn-P) of the composite electrode-integrated separator for water electrolysis according to one embodiment of the present invention.
11 shows the performance (voltage, current density) performance of a single cell of an electrolytic cell in which a composite electrode-integrated separator for electrolysis according to an embodiment of the present invention is applied.
FIG. 12 is a strong alkali (30% KOH) solution at a temperature of 80° C., which is an operating environment of an alkaline water electrolysis system, for an anode (N-Fe-Zn-P) of a composite electrode-integrated separator for water electrolysis according to an embodiment of the present invention. It shows the corrosion evaluation results of the electrode according to the change in voltage potential within.
FIG. 13 shows the results of durability evaluation of the anode (N-Fe-Zn-P) of the composite electrode-integrated separator for electrolysis according to one embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

2 and 3, the composite electrode-integrated separation plates 100a and 100b for water electrolysis according to one embodiment of the present invention include a plate-shaped conductive member 110; A flow path part 130 formed on one or both surfaces of the member; And a reaction unit 150 communicating with a flow path portion formed on one or both surfaces, and an electrode layer is formed on the reaction portion.

The conductive member 110 may be stainless steel 304, stainless 316L, nickel 304 plated with a thickness of 20 µm or more, nickel 316L plated with a thickness of 20 µm or more, titanium 304 plated stainless steel, or titanium plated stainless steel 316L.

It is provided with a guide groove 170 formed on the side of the conductive member 110, so that a separate guide member is seated in the guide groove 170 when assembling the electrolytic stack to facilitate assembly with a separator, gasket, and fastening plate. Can be.

The conductive member 110 is formed with a hole 140a through which an electrolyte is introduced on one side, and a hole through which hydrogen gas or oxygen gas generated by the electrolysis reaction is discharged from the reaction unit on the other side ( 140b) may be formed, and the input hole 140a and the discharge hole 140b are communicated through the flow path portion 130.

More specifically, when the flow path part 130 and the reaction part 150 are formed on both sides of the conductive member 110, one inlet hole 140a and one outlet hole 140b are formed on each surface. , The conductive member 110 may be provided with two inlet holes 140a and outlet holes 140b, and one inlet hole 140a and outlet holes 140b are paired to form a flow path part formed on one surface. It is in communication with 130. On the other hand, when the flow path portion 130 and the reaction portion 150 are formed on only one surface of the conductive member 110, one inlet hole 140a and an outlet hole 140b are formed to communicate with the flow path portion 130. do.

The flow path portion 130 serves as a channel through which the electrolyte, hydrogen gas, and oxygen gas can move, and more specifically, transfers the electrolyte flowing from the input hole 140a to the reaction portion 140 to receive water. The hydrogen gas or oxygen gas generated by the reaction is moved to the discharge hole 140b. The flow path portion 130 is formed in the shape of an intaglio on the conductive member 110 and may be formed through machining, chemical etching, or electrochemical well etching. The flow path portion 130 may be formed to a depth of 1 mm or less from the surface of the conductive member 110.

The electrode layer is formed in the reaction unit 150 region except for the flow path unit 130 region formed on one or both surfaces of the conductive member 110. Referring to FIG. 2, when formed on both surfaces of the conductive member 110, the electrode layer formed on the first surface functions as an anode, and the electrode layer formed on the opposite surface, the second surface, of the cathode. By performing a function, it is possible to provide a bipolar electrode-integrated separator having both an anode and a cathode at the same time. On the other hand, referring to Figure 3, when formed only on one surface of the conductive member 110, it can perform the function of the anode (anode) or cathode (cathode) depending on the active material of the electrode layer.

The electrode layer is a group consisting of nickel (Ni), Ni-Zn, NI-Zn-P, Ni-Fe-Zn, Ni-Fe-Zn-P and nickel-iron hydroxide ((Ni,Fe)(OH) ₂ ) It may be 1 or more selected from, more specifically, the anode (anode) is nickel (Ni), Ni, Ni-Fe-Zn, Ni-Fe-Zn-P or nickel-iron hydroxide ((Ni,Fe) (OH ) ₂ ), and the cathode (chathode) may be nickel (Ni) or Ni-Zn.

The electrode layer may be formed through electrochemical plating, spray coating, PVD deposition, thermal spray coating or hydrothermal synthesis.

When the electrode layer is nickel (Ni), the roughness of the surface of the nickel (Ni) layer is enhanced through sandblasting.

In the case of the electrode layers Ni-Zn, NI-Zn-P, Ni-Fe-Zn or Ni-Fe-Zn-P, after plating, they have a vertically oriented porous structure through selective leaching of Zn.

When the electrode layer is nickel-iron hydroxide ((Ni,Fe)(OH) ₂ ), it is preferably formed by a hydrothermal synthesis method, and the surface of the formed electrode layer has a plate-like structure.

In the case of the composite electrode-integrated separation plate 110 for electrolysis, when the flow path portion 130 and the reaction portion 150 are formed on only one surface, the function and current collecting plate of the electrode are directly connected to the fastening plates at both ends of the electrolytic stack. Can perform the functions of

A method of manufacturing a composite electrode-integrated separator for water electrolysis according to an embodiment of the present invention includes: (1) forming a flow path part and a reaction part on one or both surfaces of a plate-shaped conductive member; And (2) forming an electrode layer in the reaction unit.

In step (1), the conductive member may be a stainless 304 or a stainless 316L member, and the stainless 304 or stainless 316l may be a conductive member having a nickel or titanium plating layer of 20 to 50 μm. By forming nickel or titanium, corrosion resistance of the conductive member can be improved.

In step (1), the flow path portion and the reaction portion are formed through machining center (NCT) processing or etching. The flow path portion is formed to a depth of 1 mm or less in the vertical direction from the surface of the conductive member. The surface of the reaction unit may improve roughness roughness through etching.

The etching in step (1) may be mechanical etching or electrochemical etching. Mechanical etching can increase the roughness of the reaction part through a sandblast process using alumina particles (1 to 5 μm). In addition, electrochemical etching uses platinum or carbon as a counter electrode in a dilute aquatic electrolyte in which hydrochloric acid (3-5%) and nitric acid (1-2%) are mixed 1:1, and is formed in a conductive member. When only the reaction part is exposed (polypropylene or Teflon holder is attached), a 10V constant voltage is applied for 10 minutes as a working electrode to increase the roughness of the reaction part.

In step (2), an electrode layer of an anode or a cathode may be formed with respect to the reaction part of the conductive member having increased roughness, and the electrode layer may be formed by electrochemical plating, plasma spraying, or hydrothermal synthesis. Can be.

In the step (2), the electrode layer formed on the reaction part includes nickel (Ni), Ni-Zn, NI-Zn-P, Ni-Fe-Zn, Ni-Fe-Zn-P, and nickel-iron hydroxide ((Ni, Fe) (OH) ₂ ) It may be 1 or more selected from the group consisting of, the anode in the electrode layer (anode) Ni, Ni-Fe-Zn, Ni-Fe-Zn-P or nickel-iron hydroxide ((Ni, Fe)(OH) ₂ ), and may be Ni, Ni-Zn, or Ni-Zn-P, which is a cathode.

In the step (2), after the Ni plating layer is formed as the electrode layer, the roughness of the surface of the Ni electrode layer may be improved through sandblasting.

In the step (2), an electrode layer having a vertically oriented porous structure may be formed by selectively leaching a Zn component bonded to Ni. Specifically, (a) mixing the NH ₄ Cl in a plating solution for a Ni-Zn based multi-alloy in a molar ratio of 3 to 9 compared to Zn; (b) constructing an electrode by plating the plating solution on a metal substrate at high speed; And (c) immersing the electrode in a strong alkali solution to leach Zn.

The plating solution for the Ni-Zn-based multi-alloy of step (a) includes Ni, Zn and NH4Cl, and NH ₄ Cl may be mixed in a 3 to 9 molar ratio compared to Zn when preparing the plating solution. Preferably, NH ₄ Cl can be mixed in a molar ratio of 4 to 8 compared to Zn. The polyalloy may further include at least one metal of Co and Fe as a component in addition to Ni or Zn. Due to the molar ratio in the plating solution of NH ₄ Cl and Zn, complexation with [Zn(NH ₃ ) ₄ ] ²⁺ can be smoothly performed. The plating rate of Zn ²⁺ decreases due to the complexation. At the same time, due to the ionization of chloride, the ionic conductivity increases and the resistance in the plating solution decreases, so the plating speed of Ni, Fe, Co can increase. The plating solution may have a pH of 3 to 5.

When the ratio of NH ₄ Cl and Zn is outside the molar ratio, the plating speed of Zn is not controlled. If the plating speed of Zn is over-controlled and over-plated, the electrode has a dark gray or black surface, the mechanical stability of the plating surface is poor, and when the Zn is leached in an alkali solution, pores are not properly formed, resulting in low mechanical stability of the electrode. Can be.

According to an embodiment of the present invention, the molar ratio of Ni ²⁺ and Zn ²⁺ in the plating solution is 5:1 to 10:1, preferably 6:1 to 9:1. Another embodiment of Ni-Zn-Fe (Co) electrode produced during the plating solution within the Ni ²⁺ of the invention: Zn ^2+: The molar ratio of Fe ²⁺ (Co ²⁺⁾ is Ni ²⁺ Zn ²⁺ in accordance with the ratio ( 4 mol): Zn ²⁺ (1 to 3 mol): Fe ²⁺ (Co ²⁺ ) (1 to 2). Fe(Co) indicates that Fe or Co in a ternary alloy can be plated.

When Ni ions in the plating solution are added 10 times or more compared to Zn ions, when the Zn ²⁺ of the electrode has a molar ratio of 1/10 or less compared to Ni ²⁺ , pores are formed and the amount of Zn is insufficient, or in the alkali solution. When leaching, Zn is not selectively leached. In addition, the polished nickel plating proceeds and pores are not formed even after leaching in the alkali solution.

The ternary alloy Ni-Fe-Zn electrode manufactured by the manufacturing method of the present invention is an electrode containing 65 to 75 mol% of Ni, 7 to 12 mol% of Zn, and 15 to 25 mol% of Fe compared to Ni, Zn, and Fe. Ni-Fe-Zn-P electrode coated with phosphate is Ni to Zn, Fe, P 60 to 79 mol% Ni, 5 to 10 mol% Zn, 10 to 20 mol% Fe, and 5 to 10 mol% P It includes. Fe in the Ni-Fe-Zn or Ni-Fe-Zn-P electrode may be replaced with Co, and thereby, a Ni-Co-Zn or Ni-Co-Zn-P electrode may be manufactured.

The cross-section and surface of the prepared Ni-(Co or Fe)-Zn binary/ternary alloy plating electrode have a uniform and dense plating layer by controlling the formation of dendrites compared to the plating surface produced by the prior art, and also the plating efficiency. 98% or more.

Due to the difference in the plating speed of Zn and other metals, a γ-phase Ni-Zn alloy layer of Ni ₅ Zn ₂₁ having a body centered cubic (BCC) structure can be formed on the plating layer.

Due to the difference in the plating speed, it is possible to control the formation of vertical alignment pores in the Zn leaching process after plating by inducing vertical alignment plating of Ni.

The current density during plating in step (b) is 20 to 300 mA/cm ^2, but preferably 50 to 200 mA/cm ² . When electroplating, the electroplating may be performed at 25 to 50° C. for 10 to 90 minutes, preferably 15 to 60 minutes, to form an alloy plating layer on the STS or Ni metal substrate. In this step, a nickel or platinum electrode can be used as a counter electrode.

The thickness of the formed plating layer can be variously adjusted to 5 to 100 μm, and a γ-phase Ni-Zn alloy layer of Ni ₅ Zn ₂₁ having a BCC structure is formed on the plating layer. This is because the selective leaching of Zn is possible in the next step only when the γ-phase Ni-Zn alloy layer is formed.

In step (c), it is immersed in a strong alkali solution at 70 to 90°C, preferably 78 to 83°C, more preferably 80°C for 9 to 11 hours. The strong alkali solution may be a 20-30 wt% KOH or NaOH solution, but is not limited thereto.

Consequently, porous Ni-Zn, Ni-Fe-Zn, or Ni-Co-Zn, Ni-Fe-Co-Zn electrodes can be constructed. The surfaces of the electrodes may have a grain size of 40 to 60 nm.

In the above-described method, an active metal catalyst such as Ni, Fe, or Co having oxygen and hydrogen generating activity can be formed by coating a single or binary, ternary alloy coating with Zn on a desired metal substrate, for example, STS or Ni. . At the same time, Zn can be leached selectively in a strong alkali solution to prepare an electrode having vertical alignment pores optimized for the electrolysis reaction.

The pores of the vertical orientation in the electrode manufactured by the above method are easy to infiltrate the electrolyte solution necessary for the electrolysis reaction, thereby increasing the utilization rate of the electrode and also easily discharging the generated gas. As a result, it increases the durability of the electrode and is advantageous for high current operation of the electrolytic cell.

The step (2) may further include the step of (d) coating with phosphate.

In the step of coating with phosphate after leaching Zn, the electrode from which Zn is leached is washed with distilled water to remove impurities, followed by coating treatment in a solution containing 1 to 2 molar phosphate. The temperature of the solution containing the phosphate during coating treatment may be performed at 20 to 100°C, preferably 30 to 80°C.

When the molar concentration of the phosphate solution is greater than or equal to 2 molar concentration, an excessive amount of phosphate may be coated to lower the electrical conductivity of the electrode, leading to a decrease in electrode performance. Typically, the temperature of the phosphate solution is 100° C. or less to prevent vaporization of the solvent. On the other hand, if phosphate combined with ammonium is used, the temperature must be lowered to work below 50°C due to the risk of ammonia gas generation.

The type of phosphate may be ammonium phosphate, zinc phosphate in ammonium hydroxide, phosphoric acid, but is not limited thereto. The phosphate solution contains Dihydrogen phosphate (H ₂ PO ^4- ) ions when hydrated in a solvent such as water or ethanol. Specifically, K _α H _β O ₄ in the form of a combination of potassium and phosphate, Na _α H _β PO ₄ in the form of a combination of sodium and phosphate, and (NH ₄ ) _α H _β PO ₄ in the form of a combination of ammonium and phosphate. , Diammonium phosphate-(NH ₄ ) ₂ HPO ₄ , ammonium iron phosphate-NH ₄ Fe ₂ (PO ₄ ) ₂ , Phosphoric acid (H ₃ PO ₄ ), Zinc phosphate dissolved ammonia solution (ammonium hydroxide-NH ₄ OH) Etc. (The α and β are 1≤α≤3 and 1≤β≤3, respectively.)

For 5 to 10 minutes in a solution containing the phosphate, 1) Dip coating or 2) spray coating is used to coat the electrode with phosphate, followed by washing with distilled water to prepare an electrolytic plating electrode.

Zn and Fe in the phosphated electrolytic plating electrode are present as Zn ₃ (PO ₄ ) ₂ and Zn ₂ Fe(PO ₄ ) ₂ by combining with phosphate through a chemical reaction as shown in Reaction Scheme 1 below. Due to the Zn ₃ (PO ₄ ) ₂ and Zn ₂ Fe (PO ₄ ) ₂ , the phase change and the leaching rate of Zn and Fe are slowed down even after repeated on/off operation of the electrolytic electrode to improve the durability of the Ni-Zn-Fe electrode. Increase. As shown in FIG. 13, in the case of Ni _0.7 Fe _0.2 Zn _0.1 P electrode having a thickness of 25 to 100 μm, which is an electrode coated with phosphate, the overvoltage is less than about 325 mV in all cases of CC, VC, and RCC. This means that the efficiency of alkaline electrolytic anode durability is maintained at about 79% or higher (1.230 V/1.555 V ≒ 9%).

[Scheme 1]

_{^{3Zn 2+ + 2H 2 PO 4 -}} + 4H 2 O → Zn 3 (PO 4) 2 o 4H ₂ O ⁺ 4H +

_{^{2Zn 2+ + Fe 2+ + 2H 2}} PO 4 - + 4H 2 O → Zn 2 Fe (PO 4) 2 o 4H ₂ O ⁺ 4H +

The specific surface area of the electrode produced by the manufacturing method including the step of treating with phosphate may be 5 to 100 m ² /g.

In the step (2), an electrode layer of nickel-iron hydroxide ((Ni,Fe)(OH) ₂ ) may be formed by a hydrothermal synthesis method. Preferably, nickel-iron hydroxide ((Ni,Fe)(OH) ₂ ) can be formed as the anode.

In addition, the present invention can provide a water-electrolyte stack to which the composite electrode-integrated separator 100 for the water-electrolyte is applied.

The faucet stack is provided with end plates on both sides, and a fastening plate from one side to the other side; An anode or a cathode composite electrode-integrated separator; Membrane; A bipolar composite electrode-integrated separator; Membrane; Cathode or anode composite electrode integral separator; And a stacked structure in the order of the fastening plate. At this time, the membrane and the bipolar composite electrode-integrated separation plate can form one unit cell, and the unit cell can be manufactured with a repeating electrolytic stack structure.

As an example, referring to Figure 4, from one side, the first fastening plate (200a); An electrode (anode or cathode) formed on only one surface of the separator 100b; Membrane 300; A bipolar composite electrode-integrated separator 100a; Membrane 300; An integral separation plate 100b on which only one surface of an electrode (anode or cathode) is formed; And it provides a structure of the electrolytic stack 10 stacked in the order of the second fastening plate (200b), each component in the electrolytic stack can be assembled through the guide member 400, the guide member is a composite The electrode-integrated separators 100a and 100b and the guide grooves 170 formed in the membrane 300 are seated to facilitate assembly of the electrolytic stack. As an example, the first fastening plate 200a and the second fastening plate 200b include a gasket 210, an outlet 230 of the electrolyte solution, and a current collector 250 in a passage portion of oxygen and hydrogen gas. can do. At this time, the membrane and the bipolar composite electrode-integrated separator form one unit cell, and from one side, a first fastening plate; An anode integral separator; A first unit cell; A second unit cell; Cathode integral separator; And it can provide a structure of the stacked electrolyte layer in the order of the second fastening plate, the number of repeating unit cells can be variously adjusted according to the purpose of use.

The membrane 300 may be a porous separation membrane or an anion exchange membrane.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention, it will be apparent to those skilled in the art that the scope of the present invention is not to be construed as limited by these examples.

Example 1. Nickel (Ni) anode: Nickel (Ni) cathode

After preparing the conductive plate of stainless steel 304, the flow path portion through which the electrolyte moves on both sides of the conductive plate and the reaction portion where the electrode layer is to be formed are designed through CNC machining or etching. For the conductive plate on which the flow path is formed, nickel (Ni) plating is performed on both sides of the conductive plate except for the flow path portion with an anode and a cathode active material, and an anode having increased roughness through a sandblasting process A bipolar water electrolytic composite electrode-integrated separator is prepared.

Example 2. Nickel (Ni) anode: Ni-Zn cathode (porous vertical alignment structure)

After preparing the conductive plate of stainless steel 304, a flow path portion through which the electrolyte moves on both sides of the conductive plate and a reaction portion to be formed with the electrode layer are designed. For the conductive plate on which the flow path is formed, after roughness is increased through a sandblasting process on both sides of the conductive plate excluding the flow path portion, nickel (Ni) plating is performed as an anode active material on one side, and the other side For this, Raney-Ni (Ni-Zn) was used as a cathode active material. In order to form Ni-Zn on the negative electrode, after preparing a plating bath (pH 3 to 5) having the composition of Table 1 below, in the plating bath of Table 1 at 25 to 50°C, 50 to 300 mA/cm ² Electroplating (counter electrode (nickel electrode)) for 10 to 60 minutes at current density is applied to the γ-phase Ni-Zn electrode layer (BBC structure, Ni ₅ Zn ₂₁ ), and the thickness of the plating layer is 5 to 100 μm. After coating (Ni-Zn plating), the electrolytic separator with the electrode layer applied is immersed for 10 hours in a strong base (20-30 wt% KOH or NaOH) solution at 70 to 90° C., and the pores of vertical orientation have a porous structure. The formed (Zn selective leaching) composite electrode integral separator for water electrolysis is prepared. The composition of the negative electrode at this time has a composition of Ni _X1 -Zn _1-X1 (X1 = 0.7 to 0.8).

Bath Concentration [M] Nickel chloride 1.55 Nickel sulfamate 0.08 Zinc chloride 0.15 Ammonium chloride 0.6 ~ 1.0 Boric acid 0.25 Saccharin 0.005

Example 3. Ni-Fe-Zn anode (porous vertical alignment structure): Ni-Zn cathode (porous vertical alignment structure)

The same procedure as in Example 2 was performed, but Ni-Fe-Zn was used as a positive electrode active material in the plating process. In order to form Ni-Fe-Zn, after preparing a plating bath (pH 3 to 5) having the composition of Table 2 below, in the plating bath of Table 2 at 25 to 50°C, 50 to 300 mA/cm ² After performing electroplating (counter electrode (nickel electrode)) for 10 to 60 minutes at current density, a Ni-Fe-Zn layer is formed (Ni-Fe-Zn plating). The separator is immersed in a solution of a strong base (20-30 wt% KOH or NaOH) for 70 to 90° C. for 10 hours to prepare a composite electrode-integrated separator for water electrolysis in which pores of vertical orientation have a porous structure (selective leaching of Zn). The composition of the anode at this time has a composition of Ni _X2 -Fe _Y1 -Zn _1-X2-Y1 (X2 = 0.7 to 0.85, Y1 = 0.05 to 0.2).

Bath Concentration [M] Nickel chloride 2.0 Nickel sulfamate 0.2 Zinc chloride 0.44 Iron chloride 0.30 Ascorbic acid 0.08 Ammonium chloride 1.5 ~ 3.0 Boric acid 0.50 Saccharin 0.005

Example 4. Nickel-iron hydroxide ((Ni,Fe)(OH) ₂ ) Anode: Ni-Zn cathode (porous vertical alignment structure)

It was carried out in the same manner as in Example 2, but was used as a cathode active material, nickel-iron hydroxide ((Ni,Fe)(OH) ₂ ) prepared by a hydrothermal synthesis method. After the NI-Zn cathode having the porous vertical alignment structure in Example 2 was formed, nickel-iron hydroxide was formed on the anode surface through electrochemical plating or hydrothermal synthesis using urea.

When a nickel-iron hydroxide is formed using a hydrothermal synthesis method, a conductive plate in which a polypropylene or Teflon holder with a protruding reaction portion is placed in a reaction vessel is placed. The conductive plate is placed with the anode side facing up. The nickel and iron precursors and urea are introduced into the reaction vessel, heated to 90 to 120° C. at room temperature, and then cooled to room temperature to prepare a composite electrode-integrated separator for water electrolysis.

Example 5. Ni-Fe-Zn-P anode (vertical orientation structure): Ni-Zn-P cathode (vertical orientation structure)

The water electrolytic composite electrode-integrated separator prepared in Example 3 was 5 to 10 minutes in a solution of ammonium phosphate, zinc phosphate in ammonium hydroxide, phosphoric acid, etc., at a concentration of 1 to 2 mol containing phosphorus salt at 30 to 80°C. Dip coating or spray coating treatment was applied to the phosphate coating. The cathode of the composite electrode-integrated separator for electrolysis prepared through this has a composition of Ni _0.85 Zn _0.1 P _0.05 , and the anode has a composition of Ni _0.65 Fe _0.2 Zn _0.1 P _0.05 .

The compositions of the electrodes prepared in Examples 1 to 5 are summarized in Table 3 below.

Electrode composition Anode Cathode Example 1 Ni Ni Example 2 Ni Ni-Zn Example 3 Ni-Fe-Zn Ni-Zn Example 4 Nickel-iron hydroxide ((Ni,Fe)(OH) ₂ ) Ni-Zn Example 5 Ni-Fe-Zn-P Ni-Zn-P

Manufacturing example. Manufacture of electrolytic stack

A water electrolyte stack including the composite electrode-integrated separator plates prepared in Examples 1 to 4 was manufactured, and the water electrolyte stack includes a fastening plate (end plate); Anode separator; Membrane; Composite electrode separator prepared in Examples 1 to 4; Membrane; Cathode separator; Laminated in the order of the fastening plate (end plate), to prepare a water electrolytic stack to which 4 types of composite electrode separators were applied.

Experimental Example 1. X-ray Differaction (XRD) analysis of the cathode (Ni-Zn)

In the cathode (Ni-Zn) of the composite electrode-integrated separator for water electrolysis prepared in Examples 2 to 4, XRD structure analysis was performed before and after selective leaching of Zn after plating, and the results are shown in FIG. 5.

Referring to FIG. 5, it can be seen that a γ-phase Ni-Zn alloy layer of Ni ₅ Zn ₂₁ was formed after plating, and Zn is shown as a peak of each of Ni(111, 200, 220) after selective leaching of Zn. It can be confirmed that it was leached.

On the other hand, in the case of the anode (Ni-Fe-Zn) (not shown), when analyzing the XRD peak, the same peak as in FIG. 5 was observed to confirm Zn leaching, and the Fe peak was additionally observed.

Experimental Example 2. Surface analysis of cathode (Ni-Zn)

The surfaces of the cathode (Ni-Zn) of the composite electrode-integrated separator for water electrolysis prepared in Examples 2 to 4 were observed through SEM microscopy, and after plating, the surfaces after selective precipitation of Zn were observed. The results are shown in FIG. 6.

Referring to FIG. 6, the lower image of FIG. 6 shows the distribution of Ni and Zn through EDS elemental analysis, and it can be seen that after the selective leaching of Zn, vertically oriented pores were formed on the electrode surface.

Experimental Example 3. Cross section analysis of cathode (Ni-Zn) and anode (Ni-Fe-Zn)

The cross sections of the cathode (Ni-Zn) of the composite electrode-integrated separator for electrolysis prepared in Examples 2 to 4 and the anode (Ni-Fe-Zn) prepared in Example 3 were observed through an SEM microscope. The results are shown in FIGS. 7 (cathode) and 8 (anode).

Referring to FIG. 7, it can be seen that the cathode (Ni-Zn) (the right image in FIG. 4) formed pores in a vertical orientation.

Referring to FIG. 8, it can be confirmed that Ni _0.7 Fe _0.2 Zn _0.1 has a compositional capacity and formed vertically oriented pores.

Experimental Example 4. Cross-sectional analysis of negative electrode (Ni-Zn-P) and positive electrode (Ni-Fe-Zn-P)

The cross sections of the cathode (Ni _0.85 Zn _0.1 P _0.05 ) and the anode (Ni _0.65 Fe _0.2 Zn _0.1 P _0.05 ) of the composite electrode-integrated separator for water electrolysis prepared in Example 5 were observed through an SEM microscope. Fig. 9 shows the results.

Referring to FIG. 9, it can be seen that both the cathode (left image) and the anode (right image) maintain the pores in the vertical orientation even when the phosphoric acid (P) film is formed.

Experimental Example 5. Surface analysis of cathode (Ni-Zn-P) and anode (Ni-Fe-Zn-P)

The pore distribution of the cathode and the anode of the composite electrode-integrated separator for water electrolysis prepared in Example 5 is illustrated in FIG. 10.

Referring to FIG. 10, all of the electrodes have vertically oriented pores, but in the case of the electrode to which Fe is added, the electrodes further have fine pores having a size of 0.01 to 1 μm. The pore size distribution of both electrodes is 0.03 to 10 μm, and macro-size pores of 50 nm or more are mainly distributed. Further, the electrode layer has a specific surface area of 5 to 100 m ² /g.

Experimental Example 6. Single cell performance analysis

The performance (voltage, current density) of the electrolytic single cell to which the composite electrode-integrated separators of Examples 1 to 5 were applied through the electrolytic stack prepared in the manufacturing example was 25 wt% KOH, 80° C., 1 bar, separator The thickness was analyzed under the condition of 460 μm, and the results are shown in FIG. 11 (X-axis is the current density, which is proportional to the hydrogen and oxygen generation density, and Y-axis is the voltage corresponding to the current density).

Referring to FIG. 11 (Case 1: Example 1, Case 2: Example 2, Case 3: Example 3, Case 4: Example 4), for Example 1, 1.53V, 97 at 200 mA/cm ² % Efficiency (based on HHV (Higher Heating Value)) and 1.95V, 76% efficiency (based on HHV), compared to showing 70% efficiency (HHV) of a conventional gap type alkaline water electrolyte stack It can be confirmed that the improvement. In the case of Example 2 in which the active catalyst layer was additionally coated on the negative electrode surface, Example 79 (Case 3) in which 1.79V, 82% efficiency at 200 mA/cm ² (based on HHV), and additionally the active catalyst layer was additionally coated on both the positive electrode and the negative electrode surface In the case of 1.60V at 200 mA/cm ² , 92% efficiency (based on HHV) and 1.82V at 600 mA/cm ² , 81% efficiency (based on HHV) was achieved. In the case of Example 4 (Case 4) to which the nickel-iron hydroxide anode was applied, a higher efficiency of 1.53 V, 97% (based on HHV (Higher Heating Value)) than that of Example 3 was achieved at 200 mA/cm ² , and 600 mA At /cm ² , similar to Example 3, 1.83V, 80% efficiency (based on HHV) was achieved. This, it can be seen that in the conventional alkaline water electrolysis system, compared to the 50 to 70 efficiency% (HHV standard) at low current (200 mA/cm ² ).

On the other hand, in the case of Example 5, it showed the same results as in Example 3, which improves the durability of the electrode to be described later without affecting the electrolytic performance due to the formation of a phosphate film.

Experimental Example 7. Electrode corrosion evaluation

For the positive electrode (N-Fe-Zn-P) in Example 5, the corrosion evaluation result of the electrode according to the change in voltage potential in a strong alkaline (30% KOH) solution at a temperature of 80° C., which is the operating environment of the alkaline water electrolysis system 12 is shown.

Referring to FIG. 12, in the case of Ni _0.65 Fe _0.2 Zn _0.1 P _0.05 electrode coated with phosphate compared to Ni _0.7 Fe _0.2 Zn _0.1 electrode leaching zinc, corrosion current is about 10 ^-3 A/cm ^{2, which} is 100 times or more. Improved.

The water electrolysis system using the electrode coated with phosphate is connected to the water electrolysis system to reduce the volatility of the output of renewable energy, so it secures stability for on/off repetitive operation and prevents it from intermittent renewable energy such as solar or wind power. Linking can be enabled. In addition, it utilizes surplus power to make it possible to utilize the device by receiving water for a long time and storing large amounts of energy through hydrogen production.

Experimental Example 8. Evaluation of electrode durability

Durability evaluation (CC, VC, RCC) was performed on the positive electrode Ni _0.65 Fe _0.2 Zn _0.1 P _0.05 (electrode thickness: 25 to 100 μm) coated with the phosphate prepared in Example 5, and as a control, coated with phosphate The durability was evaluated in an electrode having a composition of Ni _0.5 Fe _0.4 Zn _0.1 , Ni _0.7 Fe _0.2 Zn _0.1 and Ni _0.6 Co _0.1 Zn _0.3 (thickness 5 to 100 μm), and the results are shown in FIG. 13.

Referring to FIG. 13, in the case of a Ni _0.7 Fe _0.2 Zn _0.1 P electrode having a thickness of 25 to 100 μm, which is an electrode coated with phosphate, the overvoltage is less than about 325 mV in all cases of CC, VC, and RCC. This means that the efficiency of the alkaline electrolytic anode durability is maintained at about 79% or more (1.230 V/1.555 V ≒ 79%).

As described above, since a specific part of the present invention has been described in detail, it is obvious to those skilled in the art that this specific technique is only a preferred embodiment, and the scope of the present invention is not limited thereby. something to do. Therefore, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

100a, 100b: Electrolytic composite electrode-integrated separator
110: conductive member 130: flow path
150: reaction unit

Claims (7)

A plate-shaped conductive member;
A flow path portion formed on one or both surfaces of the member; And
Includes a reaction portion is formed in the electrode layer in the region except the flow path portion formed on one or both sides,
In the electrode layer,
The anode is Ni-Fe-Zn-P,
The cathode is a Ni-Zn-P composite electrode-integrated separator for electrolysis, characterized in that.
delete delete delete According to claim 1,
The electrode layer has a specific surface area of 5 to 100 m ² /g, and a pore size of 0.03 to 10 μm.
According to claim 1,
The electrode layer has a vertically oriented porous structure, characterized in that the composite electrode-integrated separator for water electrolysis.
Claim 1, claim 5 and claim 6, wherein any one or two or more of the unit cell consisting of a composite electrode-integrated separator plate and a membrane for electrolysis of one or more of the electrolyte.

Images