Electrolytic water generating device

Abstract

Provided is an electrolytic water generator that electrolyzes water containing chlorine ions to generate electrolytic water containing hypochlorous acid. The electrolytic water generator includes an electrolysis cell through which the water passes and an electrode provided in the electrolysis cell. The electrode has a catalyst layer containing iridium oxide, tantalum oxide, and rhodium oxide. In the catalyst layer, the proportion of the atomic number of rhodium to the sum of the atomic number of iridium contained in the iridium oxide, the atomic number of tantalum contained in the tantalum oxide, and the atomic number of rhodium contained in the rhodium oxide is 31% or more and 60% or less.

Description

Technical Field

[0001] The solutions of this invention generally relate to an electrolytic water generation device. Background Technology

[0002] Patent document 1 discloses a technique of electrolyzing water containing chloride ions in an electrolytic cell and spraying the resulting bactericidal water containing hypochlorous acid onto a toilet to inhibit bacterial growth.

[0003] In this type of electrolysis, tap water is primarily used. Therefore, scale, mainly composed of sodium, calcium, potassium, and magnesium found in tap water, adheres to the cathode surface. If the amount of scale adhering to the electrodes increases, there is a possibility of reduced electrolytic performance and decreased ability to generate sterilizing water.

[0004] Therefore, to suppress scale buildup, a "polarity reversal" is performed by periodically switching the polarities of the cathode and anode to remove scale adhering to the cathode. However, while it is known that polarity reversal can suppress scale buildup on the electrodes, it also shortens the electrode lifespan. Therefore, Patent Document 2 discloses a technique for extending electrode lifespan and improving the ability to generate sterilizing water even after polarity reversal.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 5029930

[0008] Patent Document 2: Japanese Patent No. 5646677 Summary of the Invention

[0009] However, for water electrolysis generators, it is desirable to further extend their lifespan. To extend the lifespan of the electrodes, there are methods such as forming a thicker catalyst layer for the electrodes placed inside the electrolyzer, and increasing the size of the electrodes. However, this leads to the problem of increasing the size of the water electrolysis generator and the cost.

[0010] This invention is based on the understanding of this subject and aims to provide an electrolytic water generation device that can suppress large-scale production, increase costs, and further extend electrode life.

[0011] The first invention is an electrolytic water generating device that electrolyzes water containing chloride ions to generate electrolytic water containing hypochlorous acid. The device includes an electrolytic cell through which the water passes and electrodes disposed within the electrolytic cell. The electrodes have a catalyst layer containing iridium oxide, tantalum oxide, and rhodium oxide. In the catalyst layer, the proportion of rhodium atoms relative to the sum of the number of iridium atoms in the iridium oxide, the number of tantalum atoms in the tantalum oxide, and the number of rhodium atoms in the rhodium oxide is 31% or more and 60% or less.

[0012] Using this water electrolysis generator can prevent large-scale production, increased costs, and extended service life.

[0013] The second invention is the water electrolysis generating apparatus described in the first invention, wherein the ratio of the number of tantalum atoms to the number of iridium atoms is 0.3 or more and 1.8 or less.

[0014] Using this water electrolysis generator can further extend its service life.

[0015] The third invention is the water electrolysis generating apparatus described in the first invention, wherein the ratio of the number of tantalum atoms to the number of iridium atoms is 0.4 or more and 1.1 or less.

[0016] Using this water electrolysis generator can further extend its service life.

[0017] According to the present invention, an electrolytic water generation device that can further extend the electrode life can be provided. Attached Figure Description

[0018] Figure 1 This is a perspective view of a toilet device having an electrolytic water generation apparatus according to an embodiment.

[0019] Figure 2 It is a block diagram showing the main components of the water circuit system including the water electrolysis generating apparatus according to the embodiments.

[0020] Figure 3 This is a cross-sectional view showing the water electrolysis generating apparatus involved in the embodiment.

[0021] Figure 4 This is a cross-sectional view showing the configuration of the electrodes included in the water electrolysis generating apparatus according to the embodiment.

[0022] Figure 5 This is a graph showing the change in durability when the rhodium content in the catalyst layer of the electrode is varied.

[0023] Figure 6 This is a graph showing the change in durability when the rhodium content in the catalyst layer of the electrode is varied.

[0024] Figure 7 This is a graph showing the change in durability when the tantalum content in the catalyst layer of the electrode is varied.

[0025] Figure 8 This is a graph showing the change in durability when the Ta / Ir ratio in the catalyst layer of the electrode is varied.

[0026] Figure 9 It is a graph showing the results of the compositional analysis of the electrodes. Detailed Implementation

[0027] The following is a reference to the appendix. Figure 1 The embodiments of the present invention will be described below. It should be noted that in the accompanying drawings, the same constituent elements are labeled with the same symbols and detailed descriptions are omitted where appropriate.

[0028] Figure 1 This is a perspective view of a toilet device having an electrolytic water generation apparatus according to an embodiment.

[0029] Figure 1 The toilet device shown includes a Western-style toilet (hereinafter referred to as "toilet" for ease of explanation) 80 and a sanitary washing device 10 disposed thereon. The sanitary washing device 10 has a housing 40, a toilet seat 20, and a toilet lid 30. The toilet seat 20 and the toilet lid 30 are respectively supported by a shaft on the housing 40 and can be opened and closed freely.

[0030] Inside the outer casing 40, there is a built-in body washing function unit, which is used to wash the "buttocks" and other parts of the user sitting on the toilet seat 20. In addition, inside the outer casing 40, there are appropriately installed human body sensors that detect when the user approaches and leaves the toilet seat, and seating sensors that detect when the user is sitting on the toilet seat 20.

[0031] The user can, for example, operate the remote control 50 to extend the washing nozzle 44 into the basin 81 of the toilet 80, or to retract the washing nozzle 44 into the housing 40. It should be noted that... Figure 1 The hygiene cleaning device 10 shown indicates that the cleaning nozzle 44 is extended into the basin 81.

[0032] Multiple water outlets (spray holes) 45 are provided at the front end of the cleaning nozzle 44. The cleaning nozzle 44 can spray water from the water outlets 45 provided at its front end to clean the "buttocks" of the user sitting on the toilet seat 20.

[0033] It should be noted that in this application specification, from the perspective of a user sitting on the toilet seat 20, "above" is designated as "above" and "below" is designated as "below". Additionally, from the perspective of a user sitting on the toilet seat 20, "in front" is designated as "in front" and "behind" is designated as "behind". Furthermore, from the perspective of a user sitting on the toilet seat 20, "right side" is designated as "right side" and "left side" is designated as "left side".

[0034] Figure 2 It is a block diagram showing the main components of the water circuit system including the water electrolysis generating apparatus according to the embodiments.

[0035] The sanitary cleaning device 10 has a flow path (piping) 40a that guides tap water supplied by a water source such as a water pipe or water tank to the outlet 45 of the cleaning nozzle 44. A valve 42, such as a solenoid valve, is provided on the upstream side of the flow path 40a. The valve 42 controls the supply of tap water to the flow path 40a based on instructions from a control unit 41 located inside the housing 40.

[0036] The electrolytic water generating device 1 according to the embodiment is provided downstream of valve 42. In addition, between valve 42 and the electrolytic water generating device 1, a safety valve, a pressure regulating valve for adjusting the pressure of water flowing in flow path 40a, a pump for changing the flow rate of water, a heat exchanger for heating water, etc., can be appropriately provided.

[0037] The water electrolysis generator 1 has a pair of electrodes inside, and tap water flowing inside is electrolyzed by being energized by the control unit 41. Since tap water contains chloride ions, hypochlorous acid can be produced by electrolyzing the chloride ions. As a result, the electrolyzed water (electrolyzed water) in the water electrolysis generator 1 becomes a liquid containing hypochlorous acid.

[0038] Hypochlorous acid acts as a bactericidal component. Electrolyzed water containing hypochlorous acid is sprayed from the outlet 45 of the cleaning nozzle 44, or sprayed toward the outer peripheral surface (body) of the cleaning nozzle 44 and the outlet 45. Thus, sterilization can be performed using the flow path, the outer peripheral surface of the cleaning nozzle 44, and the outlet 45, which are located downstream of the electrolyzed water generating device 1.

[0039] A flow path switching valve 43 is provided downstream of the water electrolysis generator 1. The flow path switching valve 43 has a vacuum circuit breaker (atmospheric open port) 431 and a flow regulating valve 432. The vacuum circuit breaker 431 is positioned midway in the flow path that guides the water or electrolyzed water supplied from the water electrolysis generator 1 to the discharge port 45 of the cleaning nozzle 44, preventing backflow of water or electrolyzed water. Alternatively, the vacuum circuit breaker 431 can facilitate drainage within the flow path 40a by drawing in air.

[0040] A flow regulating valve 432 is provided downstream (on the air-open side) of the vacuum circuit breaker 431. The flow regulating valve 432 switches the water supply to the following paths: a path that directs washing water to the posterior wash outlet 45; a path that directs washing water to the feminine wash outlet; and a path that directs washing water to the nozzle wash chamber 47, etc. That is, the flow regulating valve 432 has multiple ports that can be selectively connected to multiple outlets 45.

[0041] A washing nozzle 44 is provided downstream of the flow regulating valve 432. The washing nozzle 44 receives driving force from the nozzle motor 46 and can extend from inside the housing 40 into the basin 81 of the toilet 80, or retract into the housing 40. That is, the nozzle motor 46 can move the washing nozzle 44 forward and backward based on commands from the control unit 41. The flow regulating valve 432 moves along with the forward and backward movement of the washing nozzle 44. In other words, the flow regulating valve 432 moves together with the washing nozzle 44.

[0042] A nozzle cleaning chamber 47 is provided downstream of the flow regulating valve 432. The nozzle cleaning chamber 47 is fixed inside the housing 40 and is capable of cleaning the cleaning nozzle 44 in a standby state after it has retracted into the housing 40. Alternatively, the nozzle cleaning chamber 47 can clean the outer peripheral surface of the cleaning nozzle 44 during its forward and backward movement. Specifically, the nozzle cleaning chamber 47 can sterilize or clean the outer peripheral surface of the cleaning nozzle 44 by spraying electrolyzed water or water from a discharge section (not shown) located inside it.

[0043] Figure 3 This is a cross-sectional view showing the water electrolysis generating apparatus involved in the embodiment.

[0044] like Figure 3 The electrolytic water generating device 1 comprises an electrolytic cell 2 and a pair of electrodes 3 and 4. Electrodes 3 and 4 are disposed inside the electrolytic cell 2 and connected to a power source. By applying voltage to electrodes 3 and 4, tap water passing inside the electrolytic cell 2 is electrolyzed. It should be noted that... Figure 3 (a) indicates a state in which voltage is applied with electrode 3 as the cathode and electrode 4 as the anode. Figure 3 (b) indicates the state in which voltage is applied with electrode 3 as the anode and electrode 4 as the cathode.

[0045] like Figure 3 As shown in (a), if tap water is electrolyzed, chlorine is generated from chloride ions at electrode 4 on the anode side. The generated chlorine then dissolves in water to form hypochlorous acid. At this time, scale is formed from calcium ions and other substances contained in the tap water at electrode 3 on the cathode side, adhering to the surface of electrode 3. Therefore, the control unit 41 performs electrolysis at a predetermined time. Figure 3 (a) shows the state towards Figure 3The polarity reversal of the state shown in (b) causes the polarity of the voltage applied to electrodes 3 and 4 to be reversed.

[0046] By reversing the polarity, electrode 3, which functions as a cathode, becomes an anode, and electrode 4, which functions as an anode, becomes a cathode. Acid is generated on electrode 3, which is covered with scale, and this acid dissolves the scale, thus enabling the scale attached to electrode 3 to be removed.

[0047] The control unit 41 measures, for example, the accumulated time of electrolysis in the water electrolysis generator 1 after the previous polarity reversal. Furthermore, the control unit 41 presets an accumulation time for polarity reversal. When the accumulated electrolysis time reaches the preset accumulation time, the control unit 41 controls the power supply to reverse the polarity. For example, when the voltage applied between electrodes 3 and 4 is 5V, the polarity is reversed every 60 seconds.

[0048] Figure 4 This is a cross-sectional view showing the configuration of the electrodes included in the water electrolysis generating apparatus according to the embodiment.

[0049] like Figure 4 As shown, electrode 3 has a substrate 3a and a catalyst layer 3b disposed thereon. It should be noted that... Figure 4 The configuration of electrode 3 is illustrated, but electrode 4 has the same configuration.

[0050] The matrix 3a is, for example, composed of titanium or a titanium-based alloy. As a titanium-based alloy, a corrosion-resistant and conductive alloy with titanium as the main component can be used. Examples include Ti-Ta-Nb, Ti-Pd, Ti-Zr, and Ti-Al.

[0051] Catalyst layer 3b contains iridium oxide, tantalum oxide, and rhodium oxide. Catalyst layer 3b is, for example, as shown in... Figure 4 The catalyst layer shown consists of multiple layers, each containing iridium oxide, tantalum oxide, and rhodium oxide. Alternatively, other intermediate layers may be provided between the substrate 3a and the catalyst layer 3b.

[0052] It is believed that iridium oxide acts as a catalyst in the formation of chlorine, promoting chlorine production. Conversely, it is believed that rhodium oxide acts as a catalyst in the formation of hydrogen, promoting hydrogen production. Tantalum oxide supports both iridium oxide and rhodium oxide.

[0053] Electrodes 3 and 4 are manufactured, for example, by the following method.

[0054] First, prepare a substrate 3a and roughen its surface by methods such as sandblasting. Then, the treated substrate 3a can be fired in the atmosphere to oxidize its surface.

[0055] Then, a solution containing, for example, an iridium compound, a tantalum compound, and a rhodium compound is coated onto the surface of the substrate 3a. Next, by firing the substrate 3a coated with the solution, the iridium compound, tantalum compound, and rhodium compound are converted into iridium oxide, tantalum oxide, and rhodium oxide, respectively, forming a catalyst layer 3b. If the required thickness of the catalyst layer 3b cannot be obtained through a single coating and firing, the coating and firing process can be repeated.

[0056] If water electrolysis is repeatedly performed using electrodes 3 and 4, the concentration of hypochlorous acid produced will decrease over time, and eventually, hypochlorous acid will cease to be produced. This is believed to be because the iridium oxide contained in catalyst layer 3b detaches from catalyst layer 3b, or catalyst layer 3b peels off from substrate 3a.

[0057] The inventors of this application investigated the cumulative time (durability life) during which hypochlorous acid could be generated in the water electrolysis generator 1 while varying the proportion of rhodium oxide contained in the catalyst layer 3b. Table 1 and Figure 5 , Figure 6 This indicates the change in durability when the rhodium content in catalyst layer 3b is varied.

[0058] [Table 1]

[0059] Ir content [mol%] 62.5 60.6 56.3 42.8 31.3 18.8 Ta content [mol%] 37.5 36.4 33.7 25.7 18.7 11.2 Rh content [mol%] 0 3 10 31.5 50 70 Durability life [hr] 48 220 434 571 682 219

[0060] Table 1 shows the content (mol%) of each metal element (iridium (Ir), tantalum (Ta), and rhodium (Rh) in catalyst layer 3b and their durability at this time. Figure 5 , Figure 6 In the graph, the horizontal axis represents the rhodium content, and the vertical axis represents the durability life. Additionally, Figure 6 Yes Figure 5 The diagram further includes dashed lines on the horizontal and vertical axes. Figure 6 In the figure, the dashed line on the horizontal axis represents a durability life of 500 hours, and the dashed line on the vertical axis represents an Rh content of 60 mol%.

[0061] In this experiment, the thickness of catalyst layer 3b was 3.6 μm. Furthermore, for tantalum and iridium (excluding rhodium), the ratio of tantalum content to iridium content was 0.6.

[0062] It should be noted that the content rate of each metal element refers to the ratio of the number of atoms of each metal element to the sum of the number of iridium atoms in iridium oxide, the number of tantalum atoms in tantalum oxide, and the number of rhodium atoms in rhodium oxide.

[0063] Based on the experiment, the inventors of this application discovered the following:

[0064] Without rhodium, the durability life is significantly shorter. When the rhodium content is 3 mol% or 10 mol%, the durability life is extended compared to the case without rhodium. Then, when the rhodium content is 31 mol% or higher, the durability life is further extended. On the other hand, if the rhodium content exceeds 50 mol% and reaches 70 mol%, the durability life becomes shorter.

[0065] In addition, the general lifespan of the product is 10 years. When the sanitary cleaning device 10 is used for 10 years, the average cumulative energization time of electrodes 3 and 4 is 500 hours. If the rhodium content exceeds 60 mol% and reaches 70 mol%, the lifespan is shorter than the 500 hours of energization time considered as a 10-year lifespan.

[0066] Specifically, the inventors of this application have discovered that a suitable long service life, with an on-time of 500 hours or more and a service life of 10 years or more, is obtained when the rhodium content (excluding the rhodium content disclosed in Patent Document 2) is 31 mol% or more and 60 mol% or less. In particular, it has been found that the longest service life is obtained when the rhodium content is 50 mol%. That is, in the catalyst layer, the ratio of the number of rhodium atoms to the sum of the number of iridium atoms in iridium oxide, the number of tantalum atoms in tantalum oxide, and the number of rhodium atoms in rhodium oxide is preferably 31% or more and 60% or less. In particular, this ratio is more preferably 50% or less.

[0067] As mentioned above, rhodium oxide is considered to act as a catalyst in the generation of hydrogen from water. That is, rhodium oxide does not directly participate in the formation of chlorine. Therefore, conventionally, as disclosed in Patent Document 2, the content of rhodium oxide in the catalyst layer was set to 30 mol% or less, which is lower than the content of iridium or the like. However, the inventors of this application have discovered from experimental results that by setting the content of rhodium oxide to 31 mol% or more, which is higher than conventionally, the durability can be improved.

[0068] Table 2 and Figure 7 This represents the change in durability when the rhodium content in catalyst layer 3b is kept essentially constant while the contents of iridium and tantalum are varied. In this experiment, the thickness of catalyst layer 3b was 3.6 μm.

[0069] [Table 2]

[0070] Ir content [mol%] 0 42.8 Ta content [mol%] 69.3 25.7 Rh content [mol%] 30.7 31.5 Durability life [hr] 120 571

[0071] From Table 2 and Figure 7 The results show that when the iridium content is 0 mol%, the durability is significantly reduced. On the other hand, for tantalum, it is believed that if the proportion of tantalum oxide in the catalyst layer 3b is low, iridium oxide and rhodium oxide cannot be adequately supported, and these components become easily detached, resulting in a shorter durability. Therefore, it is preferable that the catalyst layer 3b contains at least iridium oxide, tantalum oxide, and rhodium oxide.

[0072] Table 3 and Table 2 and Figure 7 Similarly, this indicates the change in durability when the rhodium content in catalyst layer 3b is kept essentially constant and the experimental conditions are further changed.

[0073] Figure 8 This is a graph showing the change in durability when the Ta / Ir ratio in the catalyst layer of the electrode is varied. In this experiment, the thickness of the catalyst layer 3b was 3.6 μm.

[0074] [Table 3]

[0075] Ir content [mol%] 11.8 20.1 31.1 42.8 52.7 Ta content [mol%] 56.7 48.4 37.4 25.7 15.8 Rh content [mol%] 31.5 31.5 31.5 31.5 31.5 Ta / Ir ratio [-] 4.8 2.4 1.2 0.6 0.3 Durability life [hr] 87 297 714 571 522

[0076] From Table 3 and Figure 8 The results show that if the Ta / Ir ratio is 0.3 or higher, the product has a suitable long lifespan, with an on-state time of 500 hours or more, which is generally considered a 10-year lifespan. Conversely, if the Ta / Ir ratio is 1.1 or higher, the lifespan becomes shorter. Furthermore, if the Ta / Ir ratio is greater than 1.8, the product has a short lifespan, with an on-state time of less than 500 hours, which is considered a 10-year lifespan.

[0077] That is, in the catalyst layer 3b, the ratio of the number of tantalum atoms in tantalum oxide to the number of iridium atoms in iridium oxide is preferably 0.3 or more and 1.8 or less. Furthermore, in the catalyst layer 3b, the ratio of the number of tantalum atoms in tantalum oxide to the number of iridium atoms in iridium oxide is even more preferably 0.4 or more and 1.1 or less.

[0078] Figure 9 It is a graph showing the results of the compositional analysis of the electrodes.

[0079] Figure 9 (a) represents the result before using the water electrolysis generator 1. Figure 9 (b) shows the results after 730 hours of electrolysis using the water electrolysis generator 1. Compositional analysis was performed using an electrode with a catalyst layer containing 31 mol% rhodium by energy dispersive X-ray spectroscopy (SEM-EDX).

[0080] Depend on Figure 9 (a) and Figure 9 (b) shows that the peak intensity of iridium (Ir) hardly decreased after using the water electrolysis generator 1. That is, it can be seen that if the water electrolysis generator 1 according to the embodiment is used, the detachment of iridium from the catalyst layer and the peeling of the catalyst layer from the substrate with the generation of water electrolysis can be suppressed.

[0081] As described above, according to this embodiment, the lifespan of the electrode can be extended without increasing the thickness or size of the catalyst layer. That is, according to this embodiment, the increase in size and cost of the water electrolysis generator can be suppressed, and the lifespan of the water electrolysis generator can be extended. For example, by using the long-life water electrolysis generator 1 in a toilet device, the decrease in hypochlorous acid concentration as water is generated can be suppressed, and the reduction in bactericidal effect can be suppressed. Furthermore, the replacement cycle of the water electrolysis generator 1 can be extended, allowing for longer continuous use of the toilet device.

[0082] It should be noted that the application of the electrolyzed water generating device 1 to a toilet has been described here. However, the electrolyzed water generating device 1 according to this embodiment can also be applied to uses other than toilets. For example, by distributing the electrolyzed water generated by the electrolyzed water generating device 1 to the surface of a urinal, the floor of a shower area in a bathroom, the basin of a sink, etc., it is possible to inhibit the growth of bacteria in these places.

[0083] The embodiments of the present invention have been described above. However, the present invention is not limited to these descriptions. Embodiments obtained by those skilled in the art through appropriate design modifications, provided they possess the features of the present invention, are also included within the scope of the present invention. For example, the shape, size, configuration, and arrangement of the various elements of the electrolytic water generating apparatus 1 are not limited to the illustrated shape, size, configuration, and arrangement, and can be appropriately modified.

[0084] Furthermore, the elements of each of the above embodiments can be combined as long as it is technically possible, and any embodiment obtained by combining them is also included within the scope of the present invention as long as it contains the features of the present invention.

[0085] Symbol Explanation

[0086] 1. Electrolytic water generation device; 2. Electrolytic cell; 3, 4. Electrodes; 3a. Substrate; 3b. Catalyst layer; 10. Sanitary cleaning device; 20. Toilet seat; 30. Toilet lid; 40. Outer shell; 40a. Flow path; 41. Control unit; 42. Valve; 43. Flow path switching valve; 431. Vacuum circuit breaker; 432. Flow regulating valve; 44. Cleaning nozzle; 45. Water outlet; 46. Nozzle motor; 47. Nozzle cleaning chamber; 50. Remote control; 80. Toilet bowl; 81. Basin

Claims

1. An electrolytic water generating device, which electrolyzes water containing chloride ions to generate electrolyzed water containing hypochlorous acid. The device includes an electrolytic cell through which the water passes and electrodes disposed within the electrolytic cell. The electrode has a catalyst layer containing iridium oxide, tantalum oxide, and rhodium oxide. In the catalyst layer, the proportion of rhodium atoms relative to the sum of the number of iridium atoms in the iridium oxide, the number of tantalum atoms in the tantalum oxide, and the number of rhodium atoms in the rhodium oxide is 31.5% or more and 50% or less. The ratio of the number of tantalum atoms to the number of iridium atoms is 0.6.

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