ELECTROLYSIS DEVICE FOR PRODUCING HYDROGEN AND OXYGEN

Abstract

Disclosed is an electrolysis device including an electrolytic cell composed of an anode compartment equipped with an anode, a cathode compartment equipped with a cathode, and a diaphragm separating the anode compartment and the cathode compartment from each other. The device further includes an alkaline solution supply unit for supplying an alkaline solution as an electrolyte to the anode compartment, an acidic solution supply unit for supplying an acidic solution as an electrolyte to the cathode compartment, and first and second outlets for discharging electrolyzed water from the anode compartment and the cathode compartment, respectively. In the anode compartment, hydroxide ions of the alkaline solution generate oxygen through an electrode reaction, and, in the cathode compartment, hydrogen ions generate hydrogen through an electrode reaction.

Claims

1. An electrolysis device for producing hydrogen and oxygen, the device comprising: an anode installed in an anode compartment of an electrolytic cell; a cathode installed in a cathode compartment of the electrolytic cell; a diaphragm configured to separate the anode compartment and the cathode compartment from each other; an alkaline solution supply unit configured to supply an alkaline solution as an electrolyte to the anode compartment; an acidic solution supply unit configured to supply an acid solution as an electrolyte to the cathode compartment; and first and second outlets configured to discharge electrolyzed water from the anode compartment and the cathode compartment, respectively, wherein hydroxide ions of the alkaline solution generate oxygen through an electrode reaction in the anode compartment, and hydrogen ions of the acid solution generates hydrogen through an electrode reaction in the cathode compartment.

2. The device according to claim 1, wherein the diaphragm comprises a porous diaphragm allowing permeation of cations and anions.

3. The device according to claim 2, wherein the porous diaphragm comprises a water decomposition catalyst.

4. The device according to claim 1, wherein the diaphragm comprises an ion exchange membrane selected between a cation exchange membrane that is selectively permeable to cations or an anion exchange membrane that is selectively permeable to anions.

5. The device according to claim 4, wherein the ion exchange membrane comprises a water decomposition catalyst layer disposed on a first side surface of the ion exchange membrane.

6. The device according to claim 1, wherein the diaphragm comprises an anion exchange membrane positioned to face the anode in the anode compartment and a cation exchange membrane positioned to face the cathode in the cathode compartment, the cation exchange membrane and the anion exchange membrane being adjacent to each other.

7. The device according to claim 6, wherein the diaphragm further comprises a water decomposition catalyst layer disposed between the cation exchange membrane and the anion exchange membrane.

8. The device according to claim 7, wherein the water decomposition catalyst layer contains an absorbent capable of absorbing water.

9. The device according to claim 7 or 8, wherein the diaphragm comprises an amphoteric ion exchange membrane that is an integrated single body in which the cation exchange membrane, the water decomposition layer, and the anion exchange membrane are integrally formed.

10. The device according to any one of claims 1 to 8, further comprising an electrolyte regeneration unit configured to regenerate electrolyzed water produced through an electrolysis reaction and discharged from the electrolytic cell, thereby generating hydroxide ions and hydrogen ions that are used to replenish the hydroxide ions consumed in the anode compartment due to the electrolysis reaction and the hydrogen ions consumed in the cathode compartment due to the electrolysis reaction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 is a schematic configuration diagram illustrating a conventional alkaline water electrolysis device;

[0039] FIG. 2 is a schematic configuration diagram illustrating a conventional polymer electrolyte membrane electrolysis device;

[0040] FIG. 3 is a schematic configuration diagram illustrating an electrolysis device according to a first embodiment of the present invention;

[0041] FIG. 4 is a schematic configuration diagram illustrating an electrolysis device according to a second embodiment of the present invention;

[0042] FIG. 5 is a schematic configuration diagram illustrating an electrolysis device according to a third embodiment of the present invention; and

[0043] FIG. 6 is a schematic configuration diagram illustrating an electrolysis device according to a fourth embodiment of the present invention.

DETAILED DESCRIPTION

[0044] Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0045] Referring to FIG. 3, an electrolysis device 100 according to a first embodiment of the present invention includes an electrolytic cell composed of an anode compartment 110 in which an anode 111 is installed, a cathode compartment 120 in which a cathode 121 is installed, and a diaphragm 130 separating the anode compartment 110 and the cathode compartment 120 from each other. The electrolysis device 100 further includes an alkaline solution supply unit 141 for supplying an alkaline solution as an electrolyte to the anode compartment 110, an acidic solution supply unit 143 for supplying an acidic solution as an electrolyte to the cathode compartment 120, and first and second outlets 151 and 153 for discharging electrolyzed water generated in the anode compartment 110 and the cathode compartment 120.

[0046] Specifically, the electrolysis device 100 is structured such that the body 101 of the electrolytic cell is divided into the anode compartment 110 and the cathode compartment 120 by the diaphragm 130. The anode 111 is installed in the anode compartment 110 and the cathode 121 is installed in the cathode compartment 120.

[0047] The diaphragm 130) is preferably implemented with a porous diaphragm 131 and is more preferably includes a catalyst layer 133 embedded therein for helping water decomposition.

[0048] Although the catalyst layer 133 is illustrated as being provided only in a portion of the porous diaphragm 131 in the drawings, it is only for convenience of representation. Preferably, the catalyst layer 133 is provided in the entire region of the porous diaphragm 131.

[0049] The alkaline solution supply unit 141 for supplying an alkaline solution as an electrolyte is connected to the anode compartment 110 and the acidic solution supply unit 143 for supplying an acidic solution as an electrolyte is connected to the cathode compartment 120. The anode compartment 110 and the cathode compartment 120 are respectively connected to the first and second outlets 151 and 153 to discharge the salts produced through the electrolysis.

[0050] In the electrolysis device 100 according to the first embodiment of the present invention, an anodic reaction represented by Reaction Formula 3 below occurs in the anode compartment 110, thereby generating oxygen gas (O.sub.2). The theoretical standard potential for the anodic reaction is 0.401 V.

[0051] [Reaction Formula 3]

4OH.sup.−.fwdarw.O.sub.2+2H.sub.2O+4e.sup.−,E.sub.0=0.401 V

[0052] On the other hand, a cathodic reaction represented by Reaction Formula 4 below occurs in the cathode compartment 120, thereby generating hydrogen gas. The theoretical standard potential for the cathodic reaction is 0.00 V.

[0053] [Reaction Formula 4]

4H.sup.++4e.sup.−.fwdarw.2H.sub.2,E.sub.0=0.00V

[0054] The overall reaction is represented by Reaction Formula 5 shown below and the standard potential for the overall reaction is 0.401 V.

[0055] [Reaction Formula 5]

2H.sub.2O.fwdarw.2H.sub.2+O.sub.2,E.sub.0=0.401 V

[0056] Cations move to the cathode compartment 120 from the anode compartment 110 through the diaphragm 130, and anions move to the anode compartment 110 from the cathode compartment 120 through the diaphragm 130 so that an ionic balance can be achieved.

[0057] The catalyst layer 133 embedded in the diaphragm 130 decomposes water in the porous diaphragm 131 to produce hydroxide ions (OH.sup.−) and hydrogen ions (H.sup.+). The generated hydroxide ions (OH.sup.−) move to the anode compartment 110 and the generated hydrogen ions (H.sup.+) move to the cathode compartment 120, resulting in the ionic balance between the anode compartment 110 and the cathode compartment 120.

[0058] The salts generated in the anode compartment 110 and the cathode compartment 120 through the electrolysis reactions are expelled to the outside through the first and second outlets 151 and 153. The first and second outlets 151 and 153 serve as salt sources and the salts are sent to a process requiring the use of salts. Additionally, the generated salts may be converted into an acidic solution and an alkaline solution by a separate electrolyte regeneration unit 160 installed outside the electrolytic cell 101 and then supplied to the alkaline solution supply unit 141 and the acidic solution supply unit 143 for reuse.

[0059] The electrolyte regeneration unit 160 is a device for regenerating the salts generated to achieve the ionic balance back into an acidic solution and an alkaline solution. For electrolyte regeneration, various methods may be used: ion adsorption, electrolysis, electro dialysis, water decomposition electro dialysis, chemical reaction, and catalytic reaction. The electrolyte regeneration method used in the present invention is not particularly limited thereto, and any method can be used if it can convert salts into an acidic solution and an alkaline solution.

[0060] According to the present invention that has been described so far, oxygen and hydrogen are produced through electrolysis while an alkaline solution and an acidic solution are supplied to the anode compartment 110 and the cathode compartment 120, respectively. The overall theoretical standard potential required for the electrolysis is 0.401 V which is significantly lower than that of conventional techniques. Therefore, the power consumption required for electrolysis can be reduced so that the electrolysis can be cost-effectively performed. In addition, since the ionic balance between the anode compartment 110 and the cathode compartment 120 is maintained, electrolysis can be stably and continuously performed.

[0061] Referring to FIG. 4, an electrolysis device 100′ according to a second embodiment of the present invention includes: an anode 111 installed in an anode compartment 110 of an electrolytic cell; a cathode 121 installed in a cathode compartment 120 of the electrolytic cell; a diaphragm 130′ that separates the anode compartment 111 and the cathode compartment 121 from each other; an alkaline solution supply unit 141 for supplying an alkaline solution as an electrolyte to the anode compartment 110; an acidic solution supply unit 143 for supplying an acidic solution as an electrolyte to the cathode compartment 120; and first and second outlets 151′ and 153 for discharging electrolyzed water generated in the anode compartment 110 and the cathode compartment 120, respectively.

[0062] The anodic reaction and the cathodic reaction performed respectively at the anode 111 and the cathode 121 are the same as in the first embodiment that has been described with reference to FIG. 3.

[0063] The diaphragm 130′ includes a cation exchange membrane 132. The cation exchange membrane 132 allows cations to move from the anode compartment 110 to the cathode compartment 120 but blocks anions moving from the cathode compartment 120 to the anode compartment 110. The cations reaching the cathode compartment 120 after passing through the diaphragm 130′ react with the anions in the cathode compartment 120 to form a salt, thereby maintaining the ionic balance.

[0064] The salt produced in the cathode compartment 120 is supplied to a salt-consuming process or an electrolyte regeneration unit 160 through the second outlet 153, along with the unreacted acidic solution that remains.

[0065] The first outlet 151′ is a port for discharging an aqueous solution (H.sub.2O) including the alkaline solution remaining in the anode compartment 110 after the electrolysis.

[0066] Preferably, one side surface of the cation exchange membrane 132 is provided with a catalyst layer 133. Preferably, the cation exchange membrane 132 has the catalyst layer 133 on a side surface thereof facing the anode compartment. Water undergoes a catalytic reaction in the catalyst layer 133, thereby producing hydroxide ions (OH.sup.−) and hydrogen ions (H.sup.+). The produced hydrogen ions (H.sup.+) move to the cathode compartment 120 through the cation exchange membrane, thereby supplementing hydrogen ions (H.sup.+) consumed through the cathodic reaction at the cathode 121. The produced hydroxide ions (OH.sup.−) cannot permeate through the cation exchange membrane and thus remain in the anode compartment 110, thereby supplementing hydroxide ions (OH.sup.−) consumed through the anodic reaction in the anode compartment 110. This can reduce or prevent the production of a salt formed by the ions that permeate into the cathode compartment 120 for electrolytic reactions and ionic balance. Therefore, the soundness of the solution can be maintained.

[0067] Although the catalyst layer 133 is illustrated as being provided only in a portion of the cation exchange membrane 132 in the drawings, this is for convenience of representation. Preferably, the catalyst layer 133 is provided over the entire area of the cation exchange membrane 132.

[0068] In addition, the alkaline solution supply unit 141 for supplying an alkaline solution as an electrolyte is connected to the anode compartment 110 and the acidic solution supply unit 145 for supplying an acidic solution as an electrolyte is connected to the cathode compartment 120.

[0069] In addition, the salt solution generated in the cathode compartment 120 and discharged through the second outlet 153 and the electrolyzed water discharged through the first outlet 151′ are separately or collectively supplied to the electrolyte regeneration unit 160 disposed outside the electrolytic cell. Thus, the salt solution and/or the electrolyzed water may be regenerated into an acidic solution and an alkaline solution by the electrolyte regeneration unit 160 and then be returned to the electrolytic cell for reuse.

[0070] The electrolysis device 100′ configured as described above, according to the second embodiment of the present invention, has a theoretical standard potential of 0.401 V for the anodic reaction and a standard potential of 0.00 V for the cathodic reaction. Accordingly, the standard potential for an overall reaction becomes 0.401 V, thereby significantly reducing the power consumption for electrolysis compared to conventional techniques.

[0071] Referring to FIG. 5, an electrolysis device 100″ according to a third embodiment of the present invention includes: an anode 111 installed in an anode compartment 110 of an electrolytic cell; a cathode 121 installed in a cathode compartment 120 of the electrolytic cell; a diaphragm 130″ for separating the anode compartment 111 and the cathode compartment 121 from each other; an alkaline solution supply unit 141 for supplying an alkaline solution as an electrolyte to the anode compartment 110; an acidic solution supply unit 143 for supplying an acidic solution as an electrolyte to the cathode compartment 120; and first and second outlets 151 and 153′ for discharging a salt and electrolyzed water generated in the anode compartment 110 and the cathode compartment 120, respectively.

[0072] The diaphragm 130″ includes an anion exchange membrane 134. The anion exchange membrane 134 allows anions generated in the cathode compartment 120 to pass therethrough and permeate into the anode compartment 110 and prevents cations from moving from the anode compartment 110 to the cathode compartment 120. Thus, the anions having moved from the cathode compartment 120 to the anode compartment 110 react with the cations in the anode compartment 110 to form a salt.

[0073] Preferably, one side surface of the anion exchange membrane 134 is provided with a catalyst layer 133. In this embodiment, the anion exchange membrane 134 has the catalyst layer 133 on a side surface thereof facing the cathode compartment 120. The catalyst layer 133 decomposes water into hydroxide ions (OH.sup.−) and hydrogen ions (H.sup.+). The hydroxide ions (OH.sup.−) generated in the cathode compartment 120 by the catalyst layer 133 move to the anode compartment 110 through the anion exchange membrane 134, thereby supplementing hydrogen ions (H.sup.+) and hydroxide ions (OH.sup.−) consumed through the electrolysis reactions, thereby maintaining the soundness of the electrolyte solution.

[0074] The first outlet 151 is configured such the salt generated in the anode compartment 110 110 can be transferred to a salt-consuming process, and the second outlet 153′ is configured to discharge electrolyzed water (H.sub.2O) generated in the cathode compartment 120 to the outside.

[0075] In addition, the salt solution generated in the anode compartment 110 and discharged through the first outlet 151 and the electrolyzed water discharged through the second outlet 153′ are separately or collectively supplied to the electrolyte regeneration unit 160 disposed outside the electrolytic cell. Thus, the salt solution and/or the electrolyzed water can be regenerated into an acidic solution and an alkaline solution by the electrolyte regeneration unit 160 and then be returned to the electrolytic cell for reuse.

[0076] The electrolysis device 100″ illustrated in FIG. 5 also has a standard potential of 0.401 for the overall reaction, thereby significantly reducing power consumption compared to conventional techniques.

[0077] Referring to FIG. 6, an electrolysis device 200 according to a fourth embodiment of the present invention includes: an anode 111 installed in an anode compartment 110 of an electrolytic cell 201; a cathode 121 installed in a cathode compartment 120; a diaphragm 230 that separates the anode compartment 110 and the cathode compartment 120 from each other; an alkaline solution supply unit 141 for supplying an alkaline solution as an electrolyte to the anode compartment 110; an acidic solution supply unit 143 for supplying an acidic solution as an electrolyte to the cathode compartment 120; and first and second outlets 151″ and 153″ for discharging electrolyzed water from the anode compartment 110 and the cathode compartment 120, respectively.

[0078] The diaphragm 230 is equipped with a cation exchange membrane 232 installed to face the cathode compartment 120 and an anion exchange membrane 234 installed to face the anode compartment 110. Preferably, the diaphragm 230 further includes a catalyst layer 233 disposed between the cation exchange membrane 232 and the anion exchange membrane 234.

[0079] With this configuration, the same anodic reaction as described above occurs in the anode compartment 110 and the same cathodic reaction as described above occurs in the cathode compartment 120. These reactions disturb the ionic balance. For the electrolytic cell to recover from the ionic imbalance, cations in the anode compartment 110 and anions in the cathode compartment 120 attempt to move to the cathode compartment 110 and the anode compartment 120, respectively. However, the cations and anions cannot permeate through the ion exchange membranes 232 and 234 because of the selective permeation property of each of the ion exchange membranes 232 and 234.

[0080] On the other hand, water between the cation exchange membrane 232 and the anion exchange membrane 234 is decomposed into hydrogen ions (H.sup.+) and hydroxide ions (OH.sup.−), and the hydrogen ions (H.sup.+) and the hydroxide ions (OH.sup.−) move to the cathode compartment 120 and the anode compartment 110, respectively through the cation exchange membrane and the anion exchange membrane, respectively. Therefore, the ionic balance can be attained.

[0081] In this case, it is preferable that the catalyst layer 233 be interposed between the cation exchange membrane 232 and the anion exchange membrane 234. The catalyst layer 233 preferably contains an absorbent capable of absorbing water externally supplied.

[0082] The absorbent is a material having a high affinity for water (H.sub.2O), and examples of the absorbent include: hydrophilic polymers such as Chitosan, poly(acrylamide) (PAM), poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA), poly(vinylpyrrolidone) (PNVP), and poly(hydroxyethyl acrylate) (PHEA); inorganic hydrophilic materials such as silica gel and aerogel; and other hydrophilic chemical compounds. That is, materials that have a high absorptiveness for water (H.sub.2O) while maintaining their shape can be used as the absorbent. Therefore, the catalyst layer 233 can absorb water and cause a more effective water decomposition reaction, resulting in the production of hydroxide ions (OH.sup.−) and hydrogen ions (H.sup.+) so that the ionic balance can be effectively attained.

[0083] Each of the catalyst layers 133 and 233 used in the first to fourth embodiments of the present invention is made of a hydroxide or oxide of a metal such as Fe or Cr. Alternatively, it is made of a hydroxide or oxygen of a metal selected from the group consisting of Pt, Pd, Rh, Kr, Re, Os, Ru, and Ni.

[0084] Preferably, in the basic form, the diaphragm 230 includes the cation exchange membrane 232 and the anion exchange membrane 234. The diaphragm 230 may further include a catalyst layer disposed between the cation exchange membrane 232 and the anion exchange membrane 234. Preferably, the diaphragm 230 is an integrated type in which the cation exchange membrane, the catalyst layer, and the anion exchange membrane are integrally formed to be a single body. In this case, the diaphragm 230 is called an amphoteric ion exchange membrane. Due to the integrated body, the diaphragm can be easily installed and have a compact size.

[0085] In addition, when the diaphragm is an amphoteric ion exchange membrane and is implemented as a single integrated body, the resistance across the diaphragm can be reduced during the cathodic and anodic reactions. In addition, since the state of the electrolyte does not change like in a conventional water electrolysis process, it is not necessary to separate and treat produced salts, and thus the electrolytes can be continuously used without the burden of salt removal and treatment.

[0086] In the electrolysis device 200 according to the fourth embodiment, which has the configuration described above, the cathodic reaction and the anodic reaction that are the same as described above are performed in the anode compartment 110 and the cathode compartment 120, respectively. In addition, since only a standard potential of 0.401 V is required for the overall reaction, the power consumption is reduced.

[0087] The alkaline solution supply unit 141 supplies an alkaline solution as an electrolyte to the anode compartment 110 and the acidic solution supply unit 143 supplies an acidic solution as an electrolyte to the cathode compartment 120. In addition, since the electrolytes supplied to the anode compartment 110 and the cathode compartment 120 do not change in quality. Therefore, additional salt removal and treatment processes are not necessary. The alkaline solution used for electrolysis in the anode compartment 110 is discharged through the first outlet 1351 and is then returned to the alkaline solution supply unit 141 for reuse. Likewise, the acidic solution used for electrolysis in the cathode compartment 120 is discharged through the second outlet 153 and is then returned to the acid solution supply unit 143 for reuse.

[0088] The electrolyzed water discharged through the first outlet 151″ and the electrolyzed water discharged through the second outlet 153″ may be regenerated into the alkaline solution and the acidic solution by the electrolyte regeneration unit 160 disposed outside the electrolytic cell, and the alkaline solution and the acidic solution that are produced by the electrolyte regeneration unit 160 may be supplied to the electrolytic cell to replenish the alkaline solution and the acidic solution for a case where the electrolytes are unintentionally reduced for some reasons.

[0089] As described above, since it is not necessary to separate and treat salts, the electrolysis device may have a simple structure and a compact size. In particular, since there is no need to separate a salt from an electrolyte or to treat the collected salt, the electrolytes can be continuously used, resulting in reduction of cost.

[0090] In addition, although not illustrated in FIGS. 5 and 6, the electrolysis device according to the present embodiment also includes the electrolyte regeneration unit 160 that regenerates the electrolyzed water into an alkaline solution and an alkaline solution so as to be returned to the electrolytic cell.

[0091] Although the present invention has been described in conjunction with the preferred embodiments and the accompanying drawings, the present invention should not be construed as being limited to the embodiments, and those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope and spirit of the invention as defined by the appended claims. Accordingly, such modifications or variations should not be construed as being independent of the spirit or idea of the present invention, and it is noted that the modifications or variations fall within the scope of the present invention.