SPHERICAL ELECTRODE AND ELECTROLYSIS CELL INCLUDING SAME
The present invention relates to a spherical electrode and to a spherical electrode cell, and more particularly, to a method for forming an electrode on an ion-exchange resin or forming an electrolysis cell on an ion-exchange resin. The spherical electrode or spherical electrolysis cell of the present invention can be used for: electrolysis reactors, for example in hydrolysis for producing hydrogen and oxygen gas; for the production of oxidants by means of the electrolysis of electrolytes such as a sodium chloride solution and sodium chlorite; or fuel cells that generate electricity using oxygen and hydrogen.
The present invention relates to a spherical cell suitable for electrolysis of water or an aqueous solution of electrolyte (e.g. sodium chloride or sodium chlorite) or the like, and to an electrolysis cell including the same.
BACKGROUND ARTAn electrochemical cell is a kind of energy conversion system. For example, such electrochemical cells may be classified into electrolysis cells producing oxygen or hydrogen gas by using reactants, such as water, or decomposing a solution containing sodium chloride or sodium chlorite electrolyte, and fuel cells generating electricity by using oxygen and hydrogen fuel.
Fundamental constitutional unit elements of an electrochemical cell include an anode, a cathode and an electrolyte.
NaClO2→Na++ClO2− (dissociation of electrolyte at anode) [Reaction Formula 1]
ClO2−→ClO2 (gas)+e− (oxidation at anode) [Reaction Formula 2]
H2O+e−→1/2H2+OH− (reduction at cathode) [Reaction Formula 3]
Na++OH−→NaOH (production of sodium hydroxide at cathode) [Reaction Formula 4]
In addition, the system of
2H2O→4H++4e−+O2 (oxidation at anode) [Reaction Formula 5]
4H++4e−→2H2 (reduction at cathode) [Reaction Formula 6]
Meanwhile, in a fuel cell, reactions occur through a mechanism opposite to the reaction mechanism of the above-described electrolysis of water. In other words, in a fuel cell, hydrogen, methanol or other hydrogen fuel sources react with oxygen to generate electricity. Herein, general reactions occurring in a fuel cell are represented by the following Reaction Formulae 7 and 8
2H2→4H++4e− (oxidation at anode) [Reaction Formula 7]
4H++4e−+O2→2H2O (reduction at cathode) [Reaction Formula 8]
In the above-mentioned electrochemical reactions (Reaction Formulae 2 & 3, Reaction Formulae 5 & 6, and Reaction Formulae 7 & 8), reactions occur at the interface of an electrode. At the interface of an electrode, a solid-liquid-gas three-phase reaction is involved. Particular phenomena involved herein include provision of an electron transfer path in a solid portion, transfer of ions to an electrode in a liquid as an electrolyte, transfer of a product (in the case of a liquid) to a bulk solution, and transfer of a gas product to a bulk solution in a gaseous portion. Therefore, to maximize the efficiency of an electrochemical reaction, it is required to maximize electrolyte transferability (conductivity), to maximize an electron transfer path (electrode area), and to maximize gas product transfer (electrode shape). As a result, a general electrochemical reactor, in which an electrode having a predetermined space takes a structure of a plate-like electrode or a mesh-like electrode, requires stacking of a plurality of electrodes, thereby limiting significant improvement in its performance.
A particular example of patents related to a spherical electrode is U.S. Pat. No. 6,024,850 (Title: Modified Ion Exchange Materials, Applicant: Assignee: Halox technologies Corporation). The spherical electrode disclosed therein is characterized in that an ion-exchange resin is used as a matrix and an electrode catalyst is present in the ion-exchange resin.
However, such a spherical electrode having an electrode catalyst in an ion-exchange resin is functionally problematic, as described hereinafter with reference to
First, an electrolyte is transferred into an ion-exchange membrane to cause an electrochemical reaction, thereby causing degradation of reaction efficiency (this is because diffusion resistance is too high to transfer ions into the ion-exchange resin, and it is more difficult to transfer thus generated gas to the exterior of the ion-exchange resin).
Second, there is no electron transfer path (specifically, metal) for the electron formed by the electrochemical reaction in the ion-exchange resin, thereby increasing electron resistance and reducing reaction efficiency.
Moreover, in the case of an electrochemical reaction dealing with a high-concentration electrolyte, an electrode catalyst may be discharged, resulting in rapid degradation of durability. The electrode of the related art includes a structure having an electrode catalyst containing a counterion at the active site in the ion-exchange resin. Thus, when electrolyzing a high-concentration electrolyte, such as saturated brine, the catalyst ion may be discharged easily. This may be predicted easily from a regeneration process using brine in a general ion-exchange resin.
DISCLOSURE Technical ProblemThe present invention is directed to providing a spherical electrode structure capable of being filled in an electrolysis cell and applicable to various conditions including electrolytes or concentration.
Technical SolutionIn one general aspect, the present invention provides an electrode for an electrochemical cell including an ion-exchange resin matrix and a first electrode layer coated on a surface of the ion-exchange resin matrix, characterized in that the electrode has a shape selected from the group consisting of spheres, granules, beads, grains and fibers.
According to an embodiment, the first electrode layer may be coated on 1-100% of the total surface area of the electrode for an electrochemical cell. Particularly, a coating ratio of at least 70% is preferable in view of overall electrochemical performance or efficiency.
According to another embodiment, the electrode for an electrochemical cell further includes a second electrode layer, wherein the second electrode layer is coated on a surface of the ion-exchange resin matrix, and may be provided as a multilayer type electrode in which the first electrode layer is coated on a surface of the second electrode layer. In addition, the electrode for an electrochemical cell may further include a third electrode layer coated on a surface of the first electrode layer. Such a multilayer type electrode may exhibit electrode quality equal to or better than an electrode using a noble metal catalyst, while reducing the amount of an expensive noble metal catalyst significantly.
In another general aspect, the present invention provides an electrochemical cell including an ion-exchange resin matrix, a first electrode layer coated on a surface of the ion-exchange resin matrix, and a second electrode layer coated on the surface of the ion-exchange resin matrix, characterized in that the electrode has a shape selected from the group consisting of spheres, granules, beads, grains and fibers, and the first electrode layer and the second electrode layer correspond to an anode and a cathode, respectively, or to a cathode and an anode, respectively.
According to an embodiment, the first electrode layer and the second electrode layer have a combined surface area corresponding to 1-99%, particularly 30-90% of the total surface area of the electrode chemical cell. According to another embodiment, to provide the above-defined range of combined surface area, each of the first electrode layer and the second electrode layer may be coated on 0.5-60% of the total surface area of the electrochemical cell.
Particularly, when the first electrode layer and the second electrode layer have a combined surface area corresponding to 50-70% of the total surface area of the electrochemical cell, and each of the anode and the cathode is coated in such a manner that each surface area is 30-35% of the total surface area of the electrochemical cell, the resultant electrochemical cell is capable of normal operation even without a short-preventing medium, such as a non-woven web, between the anode and the cathode.
Controlling the surface coating degree of the electrode may be performed easily by those skilled in the art as long as it is based on the present disclosure.
The matrix may be selected from the group consisting of: strongly acidic crosslinked polystyrene-divinylbenzene cationic resins; weakly acidic crosslinked polystyrene-divinylbenzene cationic resins; iminodiacetic acid-chelated crosslinked polystyrene-divinylbenzene cationic resins; strongly basic polystyrene-divinylbenzene anionic resins; weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic acrylic anionic resins; strongly acidic perfluorosulfonated cationic resins; strongly basic perfluroroaminated anionic resins; natural anion exchangers; natural cation exchangers; porous inorganic materials; and combinations thereof.
The first electrode layer may be selected from the group consisting of platinum group metals (platinum, ruthenium, rhodium, palladium, osmium, iridium), as well as gold, silver, chrome, iron, lead, titanium, manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc, tin and alloys or combinations thereof. The second electrode layer may be selected from the group consisting of titanium, silver, copper, tin and alloys or combinations thereof. In addition, the first electrode layer may have a thickness of 0.1-5 μm.
In still another general aspect, the present invention provides a hollow sphere electrode capable of being filled between an anode and a cathode, between an anode and a membrane, between a cathode and a membrane, between a membrane and a membrane, or the like, in an electrolysis cell for an aqueous solution containing an electrolyte, characterized in that the electrode is filled in such a manner that the electrode has an area of 1,000-1,000,000 cm2 per m3 of volume of the electrolysis cell.
According to an embodiment, the hollow sphere electrode has a structure in which a metal is precipitated as an electrochemical catalyst on a surface of a medium capable of ion exchange in an amount of 1-100%.
The electrolysis cell includes a medium capable of ion exchange, and at least one metal precipitated as an electrochemical catalyst on a surface of the medium at a ratio of 1-99%.
Advantageous EffectsThe electrode according to an embodiment has an electrode surface area up to 100 m2 per m3 of an electrolysis cell, and thus maximizes the performance of an electrolysis system, makes an electrolysis system compact, and reduces manufacturing cost.
Hereinafter, the embodiments of the present disclosure will be described in detail with reference to accompanying drawings.
The matrix 410 may be any medium capable of ion exchange. Particular examples of the matrix material include: strongly acidic crosslinked polystyrene-divinylbenzene cationic resins; weakly acidic crosslinked polystyrene-divinylbenzene cationic resins; iminodiacetic acid-chelated crosslinked polystyrene-divinylbenzene cationic resins; strongly basic polystyrene-divinylbenzene anionic resins; weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic acrylic anionic resins; strongly acidic perfluorosulfonated cationic resins; strongly basic perfluroroaminated anionic resins; natural anion exchangers, such as clay; natural cation exchangers, such as manganese greensand; porous inorganic materials, such as zeolite, capable of absorbing ions; and combinations thereof. Such matrix materials are commercially available.
The catalyst 420 coated on the matrix may be selected from the group consisting of platinum group metals (platinum, ruthenium, rhodium, palladium, osmium, iridium), as well as gold, silver, chrome, iron, lead, titanium, manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc, tin and alloys or oxides thereof.
Although there is no limitation in thickness of the electrode catalyst layer 420, the electrode catalyst layer may have a thickness of 0.1-5 μm, more particularly 0.1-2 μm. In the case of a thickness greater than 2 μm, a non-active reaction layer that does not participate in a reaction becomes too thick, thereby causing catalyst loss and poor cost efficiency.
The electrode catalyst layer 420 may have a surface area covering 1-100% of the surface of the matrix depending on the particular purpose of electrochemical reaction.
Methods for forming the electrode catalyst layer on the ion exchange resin body include chemical methods, such as adsorption-reduction and electroplating, physical methods, such as vacuum deposition, etc. However, considering coating on a large amount of spherical ion exchanger particles, chemical adsorption-reduction methods may be used. Chemical adsorption-reduction methods are carried out by allowing an electrode catalyst material to be adsorbed on an ion exchange resin and reducing the electrode catalyst material on the surface of the ion exchange resin. Such methods may be applied and performed easily by those skilled in the art.
In the spherical electrochemical cell, the electrode catalyst layer may have a thickness of 1-5 μm. In the case of a thickness greater than 5 μm, a non-active reaction layer that does not participate in a reaction becomes too thick, thereby causing catalyst loss.
The surface area (combined surface area of the anode layer surface with the cathode layer surface) may be within a range of 1-99% depending on the particular purpose of electrochemical reaction. More particularly, the surface area (combined surface area of the anode catalyst surface with the cathode catalyst surface) may be within a range of 30-90%. The surface area that equals to 100% means a contact between the anode and the cathode, suggesting a short between the anode and the cathode as a physical meaning. Thus, in this case, no electrochemical reaction occurs.
Methods for forming the anode catalyst metal 720 and the cathode catalyst metal 730 are the same as described above with reference to
The examples and experiments will now be described. The following examples and experiments are for illustrative purposes only and not intended to limit the scope of the present disclosure.
Examples 1-10 Manufacture of Spherical Electrodes
1. Manufacture of Spherical Electrode (see Example 9)
2. Structure of Electrolysis Cell
(1) Schematic View of Electrolysis Cell:
(2) Structural Parameters of Electrolysis Cell
3. Operation Condition of Electrolysis Cell
4. Analysis of Performance
(1) Method of Calculating Current Efficiency
Current efficiency is obtained by dividing a measured value of hypochlorous acid generated under an applied current (I) by a theoretical value according to the following formula:
Current efficiency (%)={(F×ρ×V)/(35500 (mg)×l×t)}×100,
wherein F is the Faraday constant (96500 (C)), ρ is an actual residual chlorine concentration (ppm, mg/L), V is a volume (L) of water supplied to an electrolysis cell, I is an applied current (A), and t is a time (s) of electrolysis.
(2) Performance parameters and Determination Methods
1. Structure of Electrolysis Cell
2. Operation Condition of Electrolysis Cell
3. Performance Analysis
As shown in
Claims
1. An electrode for an electrochemical cell, comprising an ion-exchange resin matrix and a first electrode layer coated on a surface of the ion-exchange resin matrix, characterized in that the electrode has a shape selected from the group consisting of spheres, granules, beads, grains and fibers.
2. The electrode for an electrochemical cell according to claim 1, wherein the first electrode layer is coated on 1-100% of a total surface area of the electrode for an electrochemical cell.
3. The electrode for an electrochemical cell according to claim 2, which further comprises a second electrode layer, wherein the second electrode layer is coated on a surface of the ion-exchange resin matrix, and the first electrode layer is coated on a surface of the second electrode layer.
4. The electrode for an electrochemical cell according to claim 3, which further comprises a third electrode layer coated on a surface of the first electrode layer.
5. The electrode for an electrochemical cell according to claim 3, wherein the matrix is selected from the group consisting of: strongly acidic crosslinked polystyrene-divinylbenzene cationic resins; weakly acidic crosslinked polystyrene-divinylbenzene cationic resins; iminodiacetic acid-chelated crosslinked polystyrene-divinylbenzene cationic resins; strongly basic polystyrene-divinyl benzene anionic resins; weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic acrylic anionic resins; strongly acidic perfluorosulfonated cationic resins; strongly basic perfluroroaminated anionic resins; natural anion exchangers; natural cation exchangers; porous inorganic materials; and combinations thereof,
- the first electrode layer is selected from the group consisting of platinum group metals (platinum, ruthenium, rhodium, palladium, osmium, iridium), as well as gold, silver, chrome, iron, lead, titanium, manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc, tin and alloys or combinations thereof,
- the second electrode layer is selected from the group consisting of titanium, silver, copper, tin and alloys or combinations thereof, and
- each of the first electrode layer and the second electrode layer has a thickness of 0.1-5 μm.
6. An electrochemical cell comprising an ion-exchange resin matrix, a first electrode layer coated on a surface of the ion-exchange resin matrix, and a second electrode layer coated on the surface of the ion-exchange resin matrix, characterized in that the electrode has a shape selected from the group consisting of spheres, granules, beads, grains and fibers, and the first electrode layer and the second electrode layer correspond to an anode and a cathode, respectively, or to a cathode and an anode, respectively.
7. The electrochemical cell according to claim 6, wherein the first electrode layer and the second electrode layer have a combined surface area corresponding to 1-99% of the total surface area of the electrode chemical cell, and each of the first electrode layer and the second electrode layer is coated on 0.5-60% of the total surface area of the electrochemical cell.
8. The electrochemical cell according to claim 7, wherein the matrix is selected from the group consisting of: strongly acidic crosslinked polystyrene-divinylbenzene cationic resins; weakly acidic crosslinked polystyrene-divinylbenzene cationic resins; iminodiacetic acid-chelated crosslinked polystyrene-divinylbenzene cationic resins; strongly basic polystyrene-divinylbenzene anionic resins; weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic polystyrene-divinylbenzene anionic resins; strongly basic/weakly basic acrylic anionic resins; strongly acidic perfluorosulfonated cationic resins; strongly basic perfluroroaminated anionic resins; natural anion exchangers; natural cation exchangers; porous inorganic materials; and combinations thereof,
- the first electrode layer is selected from the group consisting of platinum group metals (platinum, ruthenium, rhodium, palladium, osmium, iridium), as well as gold, silver, chrome, iron, lead, titanium, manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc, tin and alloys or combinations thereof, and
- the first electrode layer has a thickness of 0.1-5 μm.
Type: Application
Filed: Nov 26, 2009
Publication Date: Oct 25, 2012
Applicants: ELCHEM TECH CO, LTD. (Seoul), (Seoul)
Inventors: Sang Bong Moon (Seoul), Tae-Lim Lee (Seoul), Eun-Soo Kim (Seoul), Yun-Ki Choi (Seoul)
Application Number: 13/504,235
International Classification: C25B 11/08 (20060101); C25B 11/02 (20060101); C25B 11/06 (20060101);