JP2019206755A - Separation plate integrated with electrode for use in water electrolysis, and water electrolysis stack - Google Patents

Abstract

To provide a separation plate to be applied to a water electrolysis stack.SOLUTION: There is provided a separation plate integrated with an electrode(s) for use in water electrolysis, comprising a plate-shaped conductive member, flow path sections formed on one face or both faces of the conductive member, and a reaction section(s) having an electrode layer formed in an area of the conductive member excluding the flow path sections formed on the one face or both faces thereof.SELECTED DRAWING: Figure 2

Description

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

  Among the hydrogen production technologies, alkaline water electrolysis is a chloro-alkali process in which alkaline electrolyte (KOH) produces hydrogen and oxygen by electrochemical reaction, and salt water (NaCl) is used to produce caustic soda (NaOH) ( Similar to Chloro-alkali process).

  Among water electrolysis technologies, alkaline water electrolysis has been developed mainly in the caustic soda process, but after the industry was built based on a gap-type cell structure, the zero-gap technology was developed. No major research and development has been promoted other than the technological development of The zero-gap technology uses a foam electrode, so that the burden of gas-liquid diffusion is small, and the separator plate is not required to have other functions other than uses such as gas blocking between cells and current collection.

  The water electrolysis system is a stack for producing hydrogen, supplying water or an alkaline electrolyte solution under appropriate conditions, and controlling and managing electric power (Balance of Plant), a gas-liquid separator, and a hydrogen storage tank ( (Hydrogen tank).

  As shown in FIG. 1, the conventional water electrolysis stack has an end plate, a current collector plate, a gasket, a mesh type diffusion layer, an electrode, a separation membrane, a separation membrane fixing ring, and a cell frame that are sequentially coupled in a symmetrical manner. A single cell was designed and a stack was constructed by stacking the desired number of cells. As shown in FIG. 1, the zero-gap type has two porous electrodes in order to overcome the problem of a parallel type in which an electrode plate is designed to be spaced apart from an electrolyte. It is a structure that reduces cell resistance by leaving no gap between the plate (for example, Mesh, Foam, Lath, etc.) and the separation membrane, and hydrogen and oxygen gas generated from the surface of the electrode is passed through the porous electrode body. Is discharged to the outside. Since there is no space between the electrode and the separation membrane, there is an advantage that the operating current density can be increased by reducing the electrolyte resistance.

  However, the application of a porous electrode in the form of a mesh or foam can induce an increase in contact resistance with the separation plate or current collector plate, and requires high mechanical rigidity of the separation membrane in direct contact with the porous electrode. To do. In an environment that is even worse than the phenomenon of gas mixture of hydrogen and oxygen (there is a danger of explosion when hydrogen gas and oxygen gas are mixed and the concentration of hydrogen in oxygen gas is 4% or more) is there. When stacking tens to hundreds of cells, it is difficult to accurately match without steps between many parts, which reduces assembly productivity, and an increase in the number of stack components increases volume. As a result, the hydrogen production density is lowered, leading to an increase in electrical contact resistance, and the power consumption efficiency of the water electrolysis stack is lowered. Furthermore, this leads to an increase in stack and system prices.

  On the other hand, the PEM water electrolysis technology, whose function of the separator plate is relatively important, is separated from the porous gas diffuser for proper permeation of the electrolyte and discharge of the generated gas when the membrane electrode assembly technology is applied. The board is important. In PEM, it is important to reduce the electrical contact resistance between 1) efficient mass transfer of fuel and products and 2) separation plate-gas diffuser-electrode. The etching operation for forming the film was not considered. When the interval is generated, not only the electrical conductivity but also the resistance of the ionic conductivity is increased, leading to performance degradation. Further, since a flow path is formed on the front surface of the separator plate (electrolyte is uniformly supplied to the electrode active area), it is difficult to directly coat and form the electrode on the flow path without forming a reaction part by etching. Since there is no gap between the separation 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 increase. It is not suitable for a cell having a membrane electrode assembly structure other than a thin and flat separator.

Korean Registered Patent Publication No. 10-0405163

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

  In order to achieve the above object, the present invention provides a plate-like conductive member, a flow path formed on one or both surfaces of the conductive member, and a flow formed on the one or both surfaces. Provided is a composite electrode-integrated separator for water electrolysis that includes a reaction part in which an electrode layer is formed in a region excluding a path part.

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

The electrode layers include nickel (Ni), Ni—Zn, Ni—Zn—P, Ni—Fe—Zn, Ni—Fe—Zn—P, and nickel-iron hydroxide ((Ni, Fe) (OH). ₂ ) at least one selected from the group consisting of, and more specifically, in the electrode layer, the anode is Ni, Ni-Fe-Zn, Ni-Fe-Zn-P or nickel-iron It is a hydroxide ((Ni, Fe) (OH) ₂ ), and the cathode may be Ni, Ni—Zn or Ni—Zn—P.

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.

  The present invention also provides a water electrolysis stack including one or two or more unit cells each composed of the above-described composite electrode integrated separator for water electrolysis and a membrane.

According to the present invention as described above, a water electrolysis composite electrode integrated separator plate in which electrodes are directly formed on a separator plate in which a flow path is formed is applied to a water electrolysis stack, thereby achieving high efficiency (70 to 70). 90%) of high current (0.6 to 1.0 A / cm ² ) operation is possible.

  In addition, since a high-efficiency high-current operation is possible, the volume of the stack and the system can be reduced.

  In addition, the composite electrode separator functions as an electrode, gas-liquid diffusion layer, separator and collector, thereby reducing the number of components applied to the water electrolysis stack, thereby simplifying the assembly of the water electrolysis stack. There is an effect of making it.

It is a block diagram of the conventional water electrolysis stack. FIG. 2 is a front view (upper image) and a side view (lower image) of a composite electrode integrated separator for water electrolysis in which an anode and a cathode are formed on both sides according to an embodiment of the present invention. 1 is a front view (upper image) and a side view (lower image) of a composite electrode integrated separator for water electrolysis in which an anode or a cathode is formed only on one surface according to an embodiment of the present invention. It is a block diagram which shows an example of the water electrolysis stack to which the composite electrode integrated separator for water electrolysis according to one aspect of the present invention is applied. It is a figure which shows the XRD structure analysis before and behind 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. It is a figure which shows the SEM microscope image of the cathode (Ni-Zn) surface of the composite electrode integrated separator for water electrolysis by one aspect | mode of this invention. It is a figure which shows the SEM microscope image of the cathode (Ni-Zn) cross section of the composite electrode integrated separator for water electrolysis by one aspect | mode of this invention. It is a figure which shows the SEM microscope image of the anode (Ni-Fe-Zn) cross section of the composite electrode integrated separator for water electrolysis by one aspect | mode of this invention. Cathode (Ni _0.85 Zn _0.1 P _0.05 ) and anode (Ni _0.65 Fe _0.2 Zn ₀ ) of a composite electrode integrated separator for water electrolysis according to one embodiment of the present invention _.1 P _0.05 ) Cross-sectional SEM microscope image. It is a figure which shows the pore distribution of the cathode (Ni-Zn-P) and anode (Ni-Fe-Zn-P) of the composite electrode integrated separator for water electrolysis by one aspect | mode of this invention. It is a figure which shows the result of the performance (voltage, current density) of the water electrolysis single cell to which the composite electrode integrated separator for water electrolysis according to one aspect of the present invention was applied. Strong alkali (30% KOH) at a temperature of 80 ° C., which is the operating environment of the alkaline water electrolysis system, with respect to the anode (Ni—Fe—Zn—P) of the composite electrode integrated separator for water electrolysis according to one aspect of the present invention It is a figure which shows the corrosion evaluation result of the electrode by the change of voltage potential in a solution. It is a figure which shows the durability evaluation result of the anode (Ni-Fe-Zn-P) of the composite electrode integrated separator for water electrolysis by 1 aspect of this invention.

Hereinafter, the present invention will be described in detail.
Referring to FIGS. 2 and 3, the water electrolysis composite electrode integrated separators 100 a and 100 b according to an embodiment of the present invention include a plate-shaped conductive member 110 and one or both surfaces of the conductive member. It includes a flow channel portion 130 formed and a reaction portion 150 communicating with the flow channel portion formed on one or both surfaces, and an electrode layer is formed in the reaction portion.

  The conductive member 110 is stainless steel 304, stainless steel 316L, stainless steel 304 plated with nickel 20 μm or more, stainless steel 316L plated with nickel 20 μm or more, stainless steel 304 plated with titanium, or stainless steel 316L plated with titanium. obtain.

  A guide groove 170 formed on the side surface of the conductive member 110 is provided. When the water electrolysis stack is assembled, a separate guide member is attached to the guide groove 170 to facilitate the assembly with the separation membrane, the gasket, and the fastening plate. be able to.

  The conductive member 110 is formed with a hole 140a through which electrolyte flows in on one side, and hydrogen gas or oxygen gas generated by a water electrolysis reaction in the reaction unit is discharged on the other side. A drain hole 140b may be formed. The input hole 140a and the discharge hole 140b communicate with each other through the flow path portion 130.

  More specifically, when the flow path part 130 and the reaction part 150 are formed on both surfaces of the conductive member 110, one input hole 140a and one discharge hole 140b are formed on each surface. The member 110 may have two input holes 140a and two discharge holes 140b. One input hole 140a and one discharge hole 140b make a pair and communicate with the flow path portion 130 formed on one surface. On the other hand, when the flow path part 130 and the reaction part 150 are formed only on one surface of the conductive member 110, one input hole 140 a and one discharge hole 140 b are formed and communicated with the flow path part 130.

  The flow path part 130 plays a role of a channel through which the electrolytic solution, hydrogen gas, and oxygen gas can move. More specifically, the flow path part 130 supplies the electrolytic solution flowing from the charging hole 140a to the reaction part 140. The hydrogen gas or oxygen gas generated by the water electrolysis reaction is transferred to the discharge hole 140b. The channel portion 130 is formed in a negative shape on the conductive member 110, but can be formed by machining, chemical etching, or electrochemical etching. The flow path part 130 can 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 part 150 region excluding the channel part 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 formed on the second surface which is the opposite surface. By performing the function of a cathode, the layer can provide a bipolar electrode-integrated separator having both an anode and a cathode at the same time. On the other hand, referring to FIG. 3, when the conductive member 110 is formed only on one surface, it can function as an anode or a cathode according to the active material of the electrode layer.

The electrode layers include nickel (Ni), Ni—Zn, Ni—Zn—P, Ni—Fe—Zn, Ni—Fe—Zn—P, and nickel-iron hydroxide ((Ni, Fe) (OH). ₂ ) at least one selected from the group consisting of, and more specifically, the anode is nickel (Ni), Ni, Ni—Fe—Zn, Ni—Fe—Zn—P or nickel-iron water. It may be an oxide ((Ni, Fe) (OH) ₂ ) and the cathode may be nickel (Ni) or Ni—Zn.

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

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

  In the case of Ni—Zn, Ni—Zn—P, Ni—Fe—Zn or Ni—Fe—Zn—P as the electrode layer, the porous structure is vertically oriented through selective leaching of Zn after plating. have.

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 is a plate type With the structure of

  When the flow path part 130 and the reaction part 150 are formed only on one surface, the composite electrode integrated separator 110 for water electrolysis is directly connected to the fastening plate at both ends of the water electrolysis stack, thereby functioning and collecting electrodes. The function of the electric plate can be performed simultaneously.

  According to one aspect of the present invention, there is provided a method for manufacturing a water-electrolytic composite electrode-integrated separation plate comprising: (1) forming a flow path portion and a reaction portion on one or both sides of a plate-like conductive member; 2) forming an electrode layer in the reaction part.

  In the step (1), the conductive member is a stainless steel 304 or a stainless steel 316L member, and the stainless steel 304 or the stainless steel 316l is a conductive member in which a nickel or titanium plating layer is formed to a thickness of 20 to 50 μm. obtain. By forming nickel or titanium, the corrosion resistance of the conductive member can be improved.

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

  The etching in the step (1) may be mechanical etching or electrochemical etching. The mechanical etching can increase the roughness of the reaction part by a sandblast process using alumina particles (1 to 5 μm). Electrochemical etching is a thin aqua regia electrolyte in which hydrochloric acid (3-5%) and nitric acid (1-2%) are mixed at a ratio of 1: 1 using platinum or carbon as a counter electrode. When the working part is exposed (only in polypropylene or Teflon (registered trademark) holder) and is used as a working electrode, a 10V constant voltage is applied for 10 minutes to reduce the surface roughness of the reaction part. Increase.

  In the step (2), an anode or cathode electrode layer can be formed on the reaction part of the conductive member having an increased surface roughness. It can be performed by plating, plasma spraying or hydrothermal synthesis.

The electrode layer formed in the reaction part in the step (2) includes nickel (Ni), Ni—Zn, Ni—Zn—P, Ni—Fe—Zn, Ni—Fe—Zn—P, and nickel-iron water. And at least one selected from the group consisting of oxides ((Ni, Fe) (OH) ₂ ), and the anode in the electrode layer is Ni, Ni—Fe—Zn, Ni—Fe—Zn— P or nickel-iron hydroxide ((Ni, Fe) (OH) ₂ ) and can 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 surface roughness of the Ni electrode layer can be improved by sandblasting.

In the step (2), a Zn component bonded to Ni can be selectively leached to form an electrode layer having a vertically oriented porous structure. Specifically, (a) mixing NH ₄ Cl in a molar ratio of 3 to 9 with respect to Zn in a plating solution for a Ni—Zn based multi-component alloy, and (b) applying the plating solution to a metal substrate. And (c) leaching Zn by immersing the electrode in a strong alkaline solution.

Plating solution for step (a) Ni-Zn-based multi-alloy is, Ni, include Zn and _NH 4 Cl, the _NH 4 Cl at the time of manufacture of the plating solution at a molar ratio of 3 to 9 with respect to Zn Can be mixed. Preferably, NH ₄ Cl can be mixed at a molar ratio of 4 to 8 with respect to Zn. The multi-component alloy may further include at least one metal of Co and Fe as a constituent component in addition to Ni and Zn. Complexation to [Zn (NH ₃ ) ₄ ] ²⁺ can be smoothly performed by the molar ratio of the NH ₄ Cl and Zn in the plating solution. The complexing reduces the Zn ²⁺ plating rate. At the same time, the ion conductivity of the chloride increases to decrease the resistance in the plating solution and increase the plating rate of Ni, Fe, and Co. The plating solution may have a pH of 3-5.

When the ratio of NH ₄ Cl and Zn deviates from the above molar ratio, the Zn plating rate is not controlled. When overplating without controlling the Zn plating rate, the electrode has a dark gray or black surface and the mechanical stability of the plating surface is reduced, and pores are formed properly when Zn is leached in an alkaline solution. Therefore, the mechanical stability of the electrode may be reduced.

According to an embodiment of the present invention, the molar ratio of Ni ²⁺ to Zn ²⁺ in the plating solution is 5: 1 to 10: 1, preferably 6: 1 to 9: 1. The molar ratio of Ni ²⁺ : Zn ²⁺ : Fe ²⁺ (Co ²⁺ ) in the plating solution during the manufacture of the Ni—Zn—Fe (Co) electrode according to another embodiment of the present invention depends on the ratio of Zn ^{2+. 2+} (4 mol): Zn ²⁺ (1 to 3 mol): Fe ²⁺ (Co ²⁺ ) (1 to 2). Fe (Co) indicates that Fe or Co in the ternary alloy can be plated.

When Ni ions in the plating solution are added more than 10 times compared to Zn ions, if the electrode Zn ²⁺ has a molar ratio of 1/10 or less compared to Ni ²⁺ , pores are formed and the amount of Zn is insufficient. Alternatively, Zn is not selectively leached during leaching in an alkaline solution. In addition, no pores are formed even after bright nickel plating and leaching in an alkaline solution.

  The Ni—Fe—Zn electrode, which is a ternary alloy manufactured by the manufacturing method of the present invention, contains 65 to 75 mol% of Ni, 7 to 12 mol% of Zn, and 15 to 25 mol% of Fe with respect to Ni, Zn and Fe. It is. The Ni—Fe—Zn—P electrode coated with phosphate is Ni 60 to 79 mol%, Zn 5 to 10 mol%, Fe 10 to 20 mol% and P 5 to 10 mol% with respect to Ni, Zn, Fe and P. including. Fe in the Ni—Fe—Zn or Ni—Fe—Zn—P electrode can be replaced by Co, whereby a Ni—Co—Zn or Ni—Co—Zn—P electrode can be manufactured.

  The Ni- (Co or Fe) -Zn binary / ternary alloy plated electrode has a cross-section and a surface that have a dendrite formation controlled and uniform and dense compared to the plated surface manufactured by the prior art. It has a plating layer, and the plating efficiency corresponds to 98% or more.

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

  The vertical alignment plating of Ni can be induced by the difference in the plating speed, and the formation of vertically aligned pores can be controlled during the Zn leaching process after plating.

In step (b), the current density during plating is 20 to 300 mA / cm ² , preferably 50 to 200 mA / cm ² . During electroplating, an alloy plating layer can be formed on the STS or Ni metal substrate by performing electroplating at 25 to 50 ° C. for 10 to 90 minutes, preferably 15 to 60 minutes. At this stage, 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 only when a γ-phase (γ-phase) Ni—Zn alloy layer is formed, Zn can be selectively leached in the next stage.

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

  As a result, a porous Ni—Zn, Ni—Fe—Zn, Ni—Co—Zn, or Ni—Fe—Co—Zn electrode can be formed. The surface of these electrodes can have a grain size of 40-60 nm.

  An electrode obtained by coating an active metal catalyst such as Ni, Fe, or Co having oxygen and hydrogen generation activity with a desired metal substrate, for example, STS or Ni together with Zn together with Zn in the above-described method. Can be configured. At the same time, Zn can be selectively leached into a strong alkaline solution to produce an electrode having vertically aligned pores optimized for a water electrolysis reaction.

  The vertically oriented pores in the electrode manufactured by the above method can easily penetrate the electrolyte solution necessary for the water electrolysis reaction, so that the utilization rate of the electrode is increased and the generated gas can be easily discharged. . As a result, the durability of the electrode is increased, which is advantageous for high current operation of the water electrolysis cell.

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

  After leaching Zn, in the step of coating with phosphate, the electrode leached with Zn is washed with distilled water to remove impurities, and then coated with a solution containing a phosphate having a molar concentration of 1 to 2. Do. The temperature of the solution containing phosphate during the film treatment is 20 to 100 ° C., preferably 30 to 80 ° C.

  When the molar concentration of the phosphate solution is 2 molar concentration or more, an excessive amount of phosphate may be coated to reduce the electrical conductivity of the electrode, leading to a decrease in electrode performance. Usually, the temperature of the phosphate solution is 100 ° C. or lower in order to prevent vaporization of the solvent. On the other hand, when using a phosphate to which an ammonium salt is bonded, the temperature must be further lowered and the operation must be performed at 50 ° C. or less because of the risk of ammonia gas generation.

The type of phosphate may be, but is not limited to, ammonium phosphate, zinc phosphate in ammonium hydroxide, phosphoric acid, and the like. The phosphate solution contains dihydrogen phosphate (H ₂ PO ⁴⁻ ) ions when hydrated in a solvent such as water or ethanol, specifically, in a form in which potassium and phosphate are combined. K _α H _β O ₄ , Na _α H _β PO ₄ in a form in which sodium and phosphate are combined, (NH ₄ ) _α H _β PO ₄ in a form in which ammonium and phosphate are combined, diammonium 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 (Zinc phosphate) ) Dissolved ammonia aqueous solution (ammonium hydro) roxide-NH ₄ OH) (the α and β are 1 ≦ α ≦ 3 and 1 ≦ β ≦ 3, respectively).

  5-10 minutes in the solution containing the phosphate 1) Dip coating or 2) Spray coating method is used to coat the electrode with phosphate, and then rinse with distilled water to perform water electrolysis. A plated electrode is manufactured.

Zn and Fe in the water electroplating electrode coated with the phosphate are bonded to the phosphate through a chemical reaction as shown in the following reaction formula 1 to form Zn ₃ (PO ₄ ) ₂ and Zn ₂ Fe. (PO ₄ ) ₂ etc. The Zn ₃ (PO ₄ ) ₂ and Zn ₂ Fe (PO ₄ ) ₂ slow the phase change and Zn / Fe leaching rate under repeated on / off operation of the water electrolysis electrode. Increase the durability of the Zn-Fe electrode. As shown in 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, in any of CC, VC and RCC However, the overvoltage is about 325 mV or less. This means that the durability efficiency of the alkaline water electrolysis anode is maintained at about 79% or more (1.230V / 1.555V≈9%).

[Reaction Formula 1]
3Zn ²⁺ + 2H ₂ PO ₄ ⁻ + 4H ₂ O → Zn ₃ (PO ₄ ) ₂ .4H ₂ O + 4H ⁺
2Zn ²⁺ + Fe ²⁺ + 2H ₂ PO ₄ ⁻ + 4H ₂ O → Zn ₂ Fe (PO ₄ ) ₂ .4H ₂ O + 4H ⁺

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

In the step (2), an electrode layer of nickel-iron hydroxide ((Ni, Fe) (OH) ₂ ) can 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 electrolysis stack to which the composite electrode integrated separator 100 for water electrolysis is applied.

  The water electrolysis stack is provided with a fastening plate (end plate) on both sides, a fastening plate from one side to the other side, an anode or a cathode composite electrode integrated separator, a membrane, A bipolar composite electrode integrated separator, a membrane, a cathode or anode composite electrode integrated separator, and a fastening plate may be laminated in this order. At this time, the membrane and the bipolar composite electrode integrated separator can form one unit cell, and a water electrolysis stack having a structure in which the unit cell is repeated can be manufactured.

  As an example, referring to FIG. 4, from one side, the first fastening plate 200a, a separation plate 100b having an electrode (an anode or cathode) formed only on one surface, a membrane 300, a bipolar composite electrode Provided is a structure of a water electrolysis stack 10 in which an integrated separator 100a, a membrane 300, an integrated separator 100b having an electrode (anode or cathode) formed on only one surface, and a second fastening plate 200b are stacked in this order. Each component in the water electrolysis stack is assembled through a guide member 400, and the guide member is mounted on a guide groove 170 formed in the composite electrode integrated separators 100a and 100b and the membrane 300, and the water electrolysis stack. Can be easily assembled. As an example, the first fastening plate 200a and the second fastening plate 200b may include a gasket 210, an electrolyte outlet / outlet 230, and a current collector 250 in the passage of the electrolyte, oxygen, and hydrogen gas. At this time, the membrane and the bipolar composite electrode integrated separator form one unit cell, and from one side, the first fastening plate, the anode integrated separator, the first unit cell, and the second unit A structure of a water electrolysis stack in which a cell, a cathode integrated separator, and a second fastening plate are sequentially stacked can be provided, and the number of repeated unit cells can be variously adjusted according to the purpose of use. .

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

  Hereinafter, the present invention will be described in more detail with reference to examples. It is obvious to those skilled in the art that these examples are only intended to illustrate the present invention and that the scope of the present invention should not be construed to be limited to these examples. Let's go.

Example 1. Nickel (Ni) anode: Nickel (Ni) cathode After preparing a conductive plate of stainless steel 304, on both sides of the conductive plate, there are a flow path portion on which the electrolyte moves and a reaction portion where an electrode layer is formed. Designed by CNC machining or etching. The conductive plate formed with the flow path is plated using nickel (Ni) as an anode and cathode active material for the reaction part excluding the flow path parts on both sides of the conductive plate. After the application, a bipolar bipolar plate with integrated electrolysis electrode with increased roughness is manufactured by a sandblasting process.

Example 2 Nickel (Ni) anode: Ni-Zn cathode (porous vertical alignment structure)
After preparing a conductive plate made of stainless steel 304, a flow path portion through which the electrolytic solution moves and a reaction portion in which an electrode layer is formed are designed on both surfaces of the conductive plate. After increasing the roughness of the reaction plate excluding the flow channel portions on both sides of the conductive plate with respect to the conductive plate formed with the flow channel through a sandblasting process, an anode is formed on one surface. ) Nickel (Ni) was used as the active material, and Raney-Ni (Ni-Zn) was used as the cathode active material for the other surface. In order to form Ni—Zn on the cathode, after preparing a plating bath (pH 3 to 5) having the composition shown in Table 1 below, the plating bath in Table 1 was used at 25 to 50 ° C. and 50 to 300 mA / cm. Electroplating (counter electrode: nickel electrode) at a current density of ² to 10 minutes and applying a γ-phase Ni—Zn electrode layer (BBC structure, Ni ₅ Zn ₂₁ ) The plating layer is applied to a thickness of 5 to 100 μm (Ni—Zn plating). Thereafter, the water electrolysis separator coated with the electrode layer is dipped in a strong base (20-30 wt% KOH or NaOH) solution at 70 to 90 ° C. for 10 hours to form a porous structure having vertically oriented pores. (Zn selective leaching) A composite electrode integrated separator for water electrolysis is manufactured. The composition of the cathode at this time has a composition of Ni _X1 —Zn _1-X1 (X1 = 0.7 to 0.8).

Example 3 FIG. Ni-Fe-Zn anode (porous vertical alignment structure): Ni-Zn cathode (porous vertical alignment structure)
Although it carried out similarly to Example 2, Ni-Fe-Zn was used as an anode active material in the plating process. In order to form Ni-Fe-Zn, a plating bath having a composition shown in Table 2 below (pH 3 to 5) was prepared, and then the plating bath in Table 2 was used at 25 to 50 ° C. and 50 to 300 mA / cm. Electroplating (counter electrode: nickel electrode) is performed at a current density of ² for 10 to 60 minutes to form a Ni—Fe—Zn layer (Ni—Fe—Zn plating). Thereafter, the water electrolysis separator plate coated with the cathode and anode electrode layers is immersed in a strong base (20 to 30 wt% KOH or NaOH) solution at 70 to 90 ° C. for 10 hours to obtain a porous material having vertically oriented pores. A composite electrode integrated separator for water electrolysis having a structure (Zn selective leaching) is manufactured. The composition of the anode at this _{time, Ni X2 -Fe Y1 -Zn 1-} X2-Y1 (X2 = 0.7~0.85, Y1 = 0.05~0.2) having the composition.

Example 4 Nickel - Iron hydroxide ((Ni, Fe) _(OH 2)) anode: Ni-Zn cathode (porous vertically aligned structure)
Although it carries out similarly to Example 2, the nickel-iron hydroxide ((Ni, Fe) (OH) ₂ ) manufactured by the hydrothermal synthesis method was used as an anode active material. After forming the Ni—Zn cathode having a porous vertical alignment structure in Example 2, nickel-iron hydroxide was formed on the anode surface by electrochemical plating or hydrothermal synthesis using urea.

  When nickel-iron hydroxide is formed using the hydrothermal synthesis method, a conductive plate having a reaction part protruding from a polypropylene or Teflon (registered trademark) holder is positioned in the reaction vessel. The conductive plate is placed with the anode side facing up. Nickel, iron precursor, and urea are charged into the reaction vessel, and the temperature is raised from room temperature to 90 to 120 ° C., and then cooled again to room temperature to produce a composite electrode integrated separator for water electrolysis.

Example 5 FIG. Ni-Fe-Zn-P anode (vertical alignment structure): Ni-Zn-P cathode (vertical alignment structure)
The water electrolysis composite electrode integrated separator prepared in Example 3 was used at 30 to 80 ° C. at a phosphate concentration of 1 to 2 molar phosphate ammonium phosphate and zinc phosphate in ammonium hydroxide. (Zinc phosphate in ammonium hydroxide), phosphoric acid (phosphoric acid) and the like, dip coating (spray coating) and spray coating (spray coating) for 5 to 10 minutes to perform a phosphate coating treatment. The cathode of the composite electrode integrated separator for water electrolysis thus produced has a composition of Ni _0.85 Zn _0.1 P _{0.05 and} the anode is Ni _0.65 Fe _{0. 2} having a composition of Zn _0.1 P _0.05 .
The compositions of the electrodes manufactured in Examples 1 to 5 are summarized in Table 3 below.

Manufacturing example. Manufacture of Water Electrolytic Stack A water electrolysis stack including the composite electrode integrated separator manufactured in Examples 1 to 4 was manufactured. The water electrolysis stack is laminated in the following order: fastening plate (end plate); anode separator plate; membrane; composite electrode separator plate manufactured in Examples 1 to 4; membrane; cathode separator plate; Thus, a water electrolysis stack to which four types of composite electrode separators were applied was manufactured.

Experimental Example 1 XRD (X-ray Diffraction) Analysis of Cathode (Ni-Zn) Selective leaching of Zn after plating at cathode (Ni-Zn) of composite electrode integrated separator for water electrolysis produced in Examples 2-4 Before and after XRD structure analysis, the results are shown in FIG.

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

  On the other hand, in the anode (Ni—Fe—Zn) (not shown), during the XRD peak analysis, the same peak as in FIG. 5 is observed, and Zn leaching can be confirmed, and the Fe peak is further observed. .

Experimental Example 2. Surface Analysis of Cathode (Ni-Zn) Using a SEM microscope on the cathode (Ni-Zn) of the composite electrode integrated separator for water electrolysis produced in Examples 2 to 4, after plating and selective Zn The surface after leaching was observed. The results are shown in FIG.

  Referring to FIG. 6, the lower image of FIG. 6 shows the distribution of Ni and Zn by EDS elemental analysis. After the selective leaching of Zn, vertically aligned pores were formed on the surface of the electrode. Can be confirmed.

Experimental Example 3. Cross-sectional analysis of cathode (Ni-Zn) and anode (Ni-Fe-Zn) The cathode (Ni-Zn) of the composite electrode integrated separator for water electrolysis produced in Examples 2 to 4 and Example 3 were used. The cross section of the anode (Ni—Fe—Zn) was observed through an SEM microscope, and the results are shown in FIG. 7 (cathode) and FIG. 8 (anode).

  Referring to FIG. 7, it can be confirmed that the cathode (Ni—Zn) (the image on the right side of FIG. 4) formed vertically aligned pores.

Referring to FIG. 8, it can be confirmed that vertically oriented pores having a composition of Ni _0.7 Fe _0.2 Zn _0.1 were formed.

Experimental Example 4 Cross-sectional analysis of cathode (Ni—Zn—P) and anode (Ni—Fe—Zn—P) Cathode (Ni _0.85 Zn ₀ ) of composite electrode integrated separator plate for water electrolysis produced in Example 5 _.1 P _0.05 ) and an anode (Ni _0.65 Fe _0.2 Zn _0.1 P _0.05 ) were observed through a SEM microscope, and the results are shown in FIG.

  Referring to FIG. 9, it is confirmed that both the cathode (left image) and the anode (right image) maintain the vertically oriented pores despite the formation of the phosphoric acid (P) film. it can.

Experimental Example 5. Surface Analysis of Cathode (Ni—Zn—P) and Anode (Ni—Fe—Zn—P) FIG. 10 shows the pore distribution of the cathode and anode of the composite electrode integrated separator for water electrolysis produced in Example 5. It was.

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

Experimental Example 6. Performance analysis of water electrolysis single cell Performance (voltage, current) of the water electrolysis single cell to which the composite electrode integrated separator of Examples 1 to 5 is applied through the water electrolysis stack produced in the above production example. Density) was analyzed under the conditions of 25 wt% KOH, 80 ° C., 1 bar, and separation film thickness of 460 μm, and the result is shown in FIG. 11 (the X axis is current density, which is proportional to the generation density of hydrogen and oxygen, The axis indicates 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), in the case of Example 1, 1.53V, 97% efficiency at 200 mA / cm ^2. (HHV (Higher Heating Value) standard) is achieved, 1.95V, 76% efficiency (HHV standard) is achieved, and 70% efficiency (HHV) of the conventional gap type alkaline water electrolysis stack is shown. It can be confirmed that there is an improvement compared to. In the case of Example 2 in which an active catalyst layer was additionally coated on the cathode surface, 1.79 V at 200 mA / cm ² , 82% efficiency (HHV standard), and the active catalyst layer was further coated on both the anode and cathode surfaces. In the case of Example 3 (Case 3), 1.60 V and 92% efficiency (HHV standard) were achieved at 200 mA / cm ² , and 1.82 V and 81% efficiency (HHV standard) were achieved at 600 mA / cm ² . In the case of Example 4 (Case 4) to which a nickel-iron hydroxide anode was applied, 1.53 V and 97% efficiency (HHV (Higher Heating Value) standard) higher than Example 3 was achieved at 200 mA / cm ^2. At 600 mA / cm ² , the same 1.83 V and 80% efficiency (HHV standard) as in Example 3 was achieved. This can be confirmed to be a significant improvement over the conventional alkaline water electrolysis system showing 50 to 70% efficiency (HHV standard) at low current (200 mA / cm ² ).

  On the other hand, in the case of Example 5, the same result as Example 3 was shown. This does not affect the water electrolysis performance by the formation of the phosphate film, and improves the durability of the electrode described later.

Experimental Example 7. Electrode Corrosion Evaluation With respect to the anode (Ni—Fe—Zn—P) in Example 5, the electrode due to the change in voltage potential in a strong alkali (30% KOH) solution at 80 ° C., which is the operating environment of the alkaline water electrolysis system The corrosion evaluation results for are shown in FIG.

Referring to FIG. 12, a Ni _0.65 Fe _0.2 Zn _0.1 P _0.05 electrode coated with phosphate as compared to a zinc-leached Ni _0.7 Fe _0.2 Zn _0.1 electrode. In this case, the corrosion current was about 10 ⁻³ A / cm ² , an improvement of 100 times or more.

  The water electrolysis system that uses phosphate-coated electrodes has been linked to the water electrolysis system to reduce variability in the output of renewable energy, so it is stable against repeated on / off operations. Can be ensured to enable cooperation with intermittent renewable energy such as sunlight or wind power. It also makes it possible to use a water electrolysis apparatus for storing large-capacity energy for a long time through hydrogen production using surplus power.

Experimental Example 8. Durability evaluation of electrode Durability evaluation for the anode 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 (CC, VC, RCC) were performed, and as a control group, Ni _0.5 Fe _0.4 Zn _0.1 , Ni _0.7 Fe _0.2 Zn _0.1 not coated with phosphate, and Durability evaluation was performed on an electrode (thickness 5 to 100 μm) having a composition of Ni _0.6 Co _0.1 Zn _0.3 , and the result is shown in FIG.

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

  As described above, specific parts of the contents of the present invention have been described in detail. For those skilled in the art, such a specific technique is only a preferred embodiment, and according to these embodiments, the present invention is described. Obviously, the scope of the invention is not limited. Thus, the substantial scope of the present invention will be defined by the appended claims and equivalents thereof.

100a, 100b Composite electrode integrated separator for water electrolysis 110 Conductive member 130 Flow path part 150 Reaction part

Claims (7)

A plate-like conductive member;
A channel portion formed on one or both surfaces of the conductive member;
A composite electrode-integrated separator for water electrolysis, comprising: a reaction part having an electrode layer formed in a region excluding the flow path part formed on the one or both surfaces.   The composite electrode-integrated separator for water electrolysis according to claim 1, wherein the flow path part is formed to a depth of 1 mm or less from the surface of the conductive member. The electrode layer is made of nickel (Ni), Ni-Zn, Ni-Zn-P, Ni-Fe-Zn, Ni-Fe-Zn-P, and nickel-iron hydroxide ((Ni, Fe) (OH). _{2. The} composite electrode-integrated separator for water electrolysis according to claim 1, wherein the separator is at least one selected from the group consisting of ₂ ). In the electrode layer,
The anode is Ni, Ni—Fe—Zn, Ni—Fe—Zn—P or nickel-iron hydroxide ((Ni, Fe) (OH) ₂ );
The composite electrode integrated separator for water electrolysis according to claim 3, wherein the cathode is Ni, Ni-Zn, or Ni-Zn-P. 4. The composite electrode integrated separator for water electrolysis according to claim 3, wherein 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.   The composite electrode integrated separator for water electrolysis according to claim 3, wherein the electrode layer has a vertically oriented porous structure.   A water electrolysis stack comprising one or two or more unit cells composed of the composite electrode integrated separator for water electrolysis according to any one of claims 1 to 6 and a membrane.