Electrochemical reaction electrodes

Abstract

This invention provides an electrochemical reaction electrode that significantly reduces the recycling costs of used electrolytes. [Solution] An electrochemical reaction electrode is provided, comprising at least two porous conductive layers formed from carbon fiber fabric and laminated together.

Description

Technical Field

[0001] The present disclosure relates to an electrochemical reaction electrode, and more specifically, to an electrochemical reaction electrode including one or more porous conductive layers.

Background Art

[0002] In current mechanical industry, electrolytic polishing is a common process for forming a shiny surface on a workpiece. After electrolytic polishing, metal contaminants in the electrolytic solution that interfere with polishing are removed by reverse electrolysis, thereby enabling regeneration. During reverse electrolysis, a metal plate is usually used as a cathode that cooperates with a filter bag (sometimes called a diaphragm bag). However, due to the small specific surface area of the filter bag, a slow reaction rate is caused, and the removal rate of metal ions such as iron (Fe) ions may not reach the desired level of at least about 50%. For this reason, attempts have been made in some studies to use graphite felt as a cathode.

[0003] However, although a cathode using graphite felt can improve the reaction rate and the removal rate of metal ions due to its high porosity and high specific surface area, its structural strength is relatively low. Therefore, when deposits occur on the cathode due to reverse electrolysis, the structural strength of the cathode is not strong enough to withstand structural damage caused by cleaning treatments such as water washing treatment or ultrasonic stirring treatment for removing the deposits. As a result, the cathode cannot be reused, and the recycling cost of the used electrolytic solution increases significantly. In other words, currently, neither the method of using a metal plate cooperating with a filter bag as a cathode nor the method of using graphite felt as a cathode can achieve the required level of improving the reaction rate and reaching at least about 50% of the removal rate of metal ions while ensuring the cleaning and reuse of the cathode.

Summary of the Invention

[0004] This disclosure provides an electrochemical reaction electrode comprising one or more porous conductive layers formed of carbon fiber fabric or having a certain degree of structural strength, thereby enabling the electrochemical reaction electrode to achieve a metal ion removal rate of at least about 50% by increasing the reaction rate while being cleaned and reused, thereby significantly reducing the recycling cost of used electrolyte.

[0005] One embodiment of the present disclosure provides an electrochemical reaction electrode comprising at least two porous conductive layers formed from a carbon fiber fabric and laminated together.

[0006] Other embodiments of the present disclosure provide an electrochemical reaction electrode comprising at least one conductive porous conductive layer. The tensile strength of the at least one porous conductive layer is in the range of 20 MPa to 4400 MPa, and the Young's modulus of the at least one porous conductive layer is in the range of 1.0 GPa to 540 GPa.

[0007] According to the electrochemical reaction electrode disclosed in the above embodiment, at least two porous conductive layers are formed from carbon fiber fabric and laminated together, or the tensile strength of the porous conductive layers is in the range of 20 MPa to 4400 MPa, and the Young's modulus of the porous conductive layers is in the range of 1.0 GPa to 540 GPa. Therefore, the structural strength of the electrochemical reaction electrode is strong enough that it can undergo cleaning treatments such as water washing and ultrasonic stirring without damage. In this way, the electrochemical reaction electrode can be cleaned and reused while increasing the reaction rate to achieve a metal ion removal rate of at least about 50%, thereby significantly reducing the recycling cost of used electrolyte. [Brief explanation of the drawing]

[0008] This disclosure will be better understood from the following detailed description herein and the accompanying drawings, which are for illustrative purposes only and are not intended to limit this disclosure.

[0009] [Figure 1]This is a schematic side view of an electrochemical reaction electrode according to the first embodiment of this disclosure. [Figure 2] Figure 1 is a schematic plan view of the porous conductive layer of the electrochemical reaction electrode. [Figure 3] Figure 1 is a schematic plan view of the porous conductive layer of the electrochemical reaction electrode. [Figure 4] Figure 1 is a schematic plan view of the porous conductive layer of the electrochemical reaction electrode. [Figure 5] Figure 1 is a schematic plan view of the clamp frame of the electrochemical reaction electrode. [Figure 6] This is a cross-sectional view of an electrochemical reaction electrode according to a second embodiment of the present disclosure. [Figure 7] This is a schematic diagram of a clamp frame according to a third embodiment of the present disclosure. [Figure 8] This is a schematic side view of an electrochemical reaction electrode according to the fourth embodiment of this disclosure. [Modes for carrying out the invention]

[0010] The following detailed description includes numerous specific details disclosed for illustrative purposes to provide a complete understanding of the embodiments. However, it will be apparent that one or more embodiments can be implemented without these specific details. In other examples, well-known structures and devices are shown schematicly for the sake of simplicity in the drawings.

[0011] First Embodiment Please refer to Figure 1. Figures 1 to 4 are schematic diagrams of an electrochemical reaction electrode 10 according to a first embodiment of the present disclosure. In this embodiment, the electrochemical reaction electrode 10 includes a current collector 100, a plurality of porous conductive layers, a plurality of end conductive films 300, a plurality of channel layers 400, and two clamp frames 500. The electrochemical reaction electrode 10 is, for example, a cathode for regenerating polishing electrolytes, but the present disclosure is not limited thereto. The electrochemical reaction electrode 10 is used in art fields involving electrochemical reactions, such as other types of electrolyte regeneration, precious metal recovery, and electrolytic reduction electrodes. Applicable products include electrolytic filter membranes, microcavity heaters, catalyst supports, and fluidized beds.

[0012] In this embodiment, the current collector 100 has a first surface 110 and a second surface 120 that face each other. The porous conductive layer includes, for example, a plurality of first porous conductive layers 210, 211, 212 and a plurality of second porous conductive layers 220, 221, 222. The first porous conductive layers 210, 211, 212 are laminated on the first surface 110 and are, for example, conductive fiber layers (e.g., conductive fiber fabric). The second porous conductive layers 220, 221, 222 are laminated on the second surface 120 and are, for example, conductive fiber layers (e.g., conductive fiber fabric).

[0013] Furthermore, the porous conductive layers (i.e., the first porous conductive layers 210, 211, 212 and the second porous conductive layers 220, 221, 222) are conductive (i.e., electrically conductive), the tensile strength of the porous conductive layers is in the range of 20 MPa to 4400 MPa, and the Young's modulus of the porous conductive layers is in the range of 1.0 GPa to 540 GPa. For example, the porous conductive layers are formed from carbon fiber fabric, and the weaving methods include plain weave, twill weave, and satin weave.

[0014] Due to the structural strength design of the porous conductive layer or the properties of the carbon fiber fabric, the structural strength of the electrochemical reaction electrode is strong enough to withstand cleaning treatments such as water washing and ultrasonic stirring without damage. Therefore, the electrochemical reaction electrode is reusable, significantly reducing its usage costs. The porous conductive layer is not limited to being formed from carbon fiber fabric. In other embodiments, the porous conductive layer is reusable as long as it has the aforementioned structural strength design or is formed from carbon fiber fabric.

[0015] Since the first porous conductive layers 210, 211, 212 and the second porous conductive layers 220, 221, 222 have similar structures, only the detailed structures of the first porous conductive layers 210, 211, 212 will be illustrated by referring to Figures 2 to 4. Please refer to Figures 1 to 4. Figures 2 to 4 are schematic plan views of the porous conductive layers of the electrochemical reaction electrode 10 in Figure 1. The first porous conductive layer 211 is located between the first porous conductive layers 210 and 212, which are located on the same side, and the first porous conductive layer 210 is located further from the current collector 100 than the other porous conductive layers (e.g., the first porous conductive layer 212) located on the same side.

[0016] The first porous conductive layers 210, 211, and 212 are, for example, plain weave fabrics and each contains multiple fiber bundles 2100, 2110, and 2120 interwoven to form multiple meshes E1, E2, and E3, respectively. The first porous conductive layers 210, 211, and 212 have, for example, different weave densities. For example, the weave density of the first porous conductive layer 210 is lower than that of the adjacent first porous conductive layer 211 located on the same side, and the weave density of the first porous conductive layer 211 is lower than that of the adjacent first porous conductive layer 212 located on the same side. In other words, the weave densities of the first porous conductive layers 210, 211, and 212 increase toward the inside. Furthermore, the electrolyte may flow inward in the electrochemical reaction electrode 10 along the flow directions F1 and F2 shown in Figure 1, for example. In this way, the electrochemical reaction electrode can achieve a metal ion removal rate of at least about 50% by increasing the reaction rate.

[0017] Generally, the K value in a fabric indicates the number of threads contained in one fiber bundle. For example, a fabric with a K value of 3K indicates that one fiber bundle contains 3000 threads. For the first porous conductive layers 210, 211, and 212, a higher K value indicates higher density, fewer meshes (corresponding to mesh E1 of the first porous conductive layer 210, mesh E2 of the first porous conductive layer 211, and mesh E3 of the first porous conductive layer 212) for the same thickness, narrower mesh widths, or more compact fiber bundles 2100, 2110, and 2120. Conversely, a lower K value indicates lower density, more meshes, wider mesh widths, or looser fiber bundles 2100, 2110, and 2120.

[0018] For example, as shown in Figure 2, the width W of the mesh E1 of the outermost first porous conductive layer 210 is 0.15 millimeters (mm) or more, and the outermost first porous conductive layer 210 has a mesh of 80 to 120. Note that Figures 2 to 4 show the first porous conductive layers 210, 211, and 212 in an exemplary and schematic manner, and the configuration of the first porous conductive layers 210, 211, and 212 (for example, the size of the first porous conductive layers 210, 211, and 212 and the number of meshes) is not limited to the configurations shown in Figures 2 to 4.

[0019] Furthermore, in this embodiment, the thickness T1 of the first porous conductive layer 210 is smaller than the thickness T2 of the first porous conductive layer 211, and the thickness T2 of the first porous conductive layer 211 is smaller than the thickness T3 of the first porous conductive layer 212. In other embodiments, the thicknesses of the first porous conductive layers 210, 211, and 212 increase toward the inside. In other embodiments, the first porous conductive layers may have the same thickness, and the thickness of the first porous conductive layers may be adjusted according to actual requirements. In some embodiments, the thickness of the first porous conductive layers may be in the range of 0.1 mm to 3 mm.

[0020] Note that the present disclosure is not limited to the number of porous conductive layers in FIG. 1. In other embodiments, the electrochemical reaction electrode may include fewer or more (e.g., nine) porous conductive layers. In other embodiments, the porous conductive layer may include only the first porous conductive layer or the second porous conductive layer disposed on one side of the current collector. In other embodiments, when the porous conductive layer has the aforementioned structural strength design, the electrochemical reaction electrode may include only one porous conductive layer. In other embodiments, when the porous conductive layer is formed of a carbon fiber fabric, the electrochemical reaction electrode may include at least two porous conductive layers laminated to each other, and the electrochemical reaction electrode may not include a current collector.

[0021] In order to promote electrical conduction in the electrochemical reaction electrode 10, an end conductive film 300 may be disposed on the porous conductive layer. The end conductive film 300 may be disposed on two opposing ends of the fiber bundles 2100, 2110, 2120 of the first porous conductive layers 210, 211, 212, respectively. In this way, the electrical connection between the fibers is strengthened, the resistance of the fibers in the fiber bundles 2100, 2110, 2120 of the first porous conductive layers 210, 211, 212 is reduced, and electrical conduction cannot be achieved only by contact between the fibers. The end conductive film 300 is located at the ends of the fiber bundles 2100, 2110, 2120, and thus prevents the chemical reaction of the electrolyte regeneration from being hindered by the end conductive film 300. In other embodiments, when the requirement for the electrical conductivity of the electrochemical reaction electrode is low, the end conductive film may be disposed on only one end of these fiber bundles.

[0022] The end conductive film 300 may be made of a metal such as, for example, nickel, gold, silver, aluminum, or a combination thereof. However, the present disclosure is not limited thereto. In other embodiments, the end conductive film may be made of copper or another type of metal resistant to oxidation. In other embodiments, when the requirement for the electrical conductivity of the electrochemical reaction electrode is low, the upper end metallization may not be performed on the electrochemical reaction electrode (that is, the electrochemical reaction electrode may not include the end conductive film). In other embodiments, the end conductive film may be another conductive coating such as a coating containing carbon nanotubes, graphene, or a transparent conductive material (for example, indium tin oxide (ITO)).

[0023] The channel layer 400 is for promoting the movement of metal ions and reducing the resistance in the thickness direction after lamination. The channel layer may be made of a highly porous conductive material such as conductive fiber paper (for example, carbon fiber paper) or non-woven conductive fiber yarns (for example, carbon fiber yarns) in which the fibers are not woven but arranged without orientation. The electrochemical reaction electrode shown in FIG. 1 is composed of a laminated structure of seven layers (that is, the current collector 100, the first porous conductive layers 210, 211, 212, and the second porous conductive layers 220, 221, 222). The channel layer 400 is disposed between two adjacent layers in the laminated structure. Since the carbon fibers in the channel layer 400 are arranged without orientation, the electrical conduction between two adjacent porous conductive layers in the thickness direction (Z-axis direction) is promoted by the channel layer 400. Therefore, the channel layer 400 reduces the resistance between two adjacent layers in the laminated structure and reduces the overall resistance of the electrochemical reaction electrode 10 in the thickness direction. In the present embodiment, the channel layer 400 is, for example, plate-shaped, but the present disclosure is not limited thereto. In other embodiments, the channel layer may be frame-shaped.

[0024] Two clamp frames 500 may be positioned around the electrochemical reaction electrode 10 to enhance the overall rigidity of the electrochemical reaction electrode 10. See Figures 1 and 5. Figure 5 is a schematic plan view of the clamp frames 500 of the electrochemical reaction electrode 10 in Figure 1. Each clamp frame 500 includes a frame body 510, a first pressing body 520, and a second pressing body 530. In each clamp frame 500, the frame body 510 has an opening 511. The first pressing body 520 and the second pressing body 530 are rod-shaped. The two opposing ends of the first pressing body 520 are connected to the frame body 510, and the first pressing body 520 covers a portion of the opening 511. The two opposing ends of the second pressing body 530 are connected to the frame body 510, and the second pressing body 530 covers a portion of the opening 511. The extending direction D1 of the first presser 520 is different from the extending direction D2 of the second presser 530, and the extending direction D1 is, for example, perpendicular to the extending direction D2. The two frame bodies 510 of the two clamp frames 500 are each positioned on two opposing sides of the current collector 100, the porous conductive layer and the channel layer 400, and fix the current collector 100, the porous conductive layer and the channel layer 400 together. In other embodiments, the shape of the frame bodies may be adjusted based on the shape of the current collector, the porous conductive layer and the channel layer, and the number of horizontal or vertical pressers may be increased or decreased by a constant or variable number.

[0025] Other embodiments are described below for illustrative purposes. In the following embodiments, reference numbers and some of the content of the above embodiments are used, the same reference numbers are used to indicate the same or similar elements, and descriptions of the same technical content are omitted. References to the above embodiments may be made to explain the omitted parts, and details are not described in the following embodiments.

[0026] Second Embodiment In the first embodiment, a first design is adopted in which the weave density and thickness increase toward the inside, and in the second embodiment, a second design is adopted in which the weave density and thickness decrease toward the inside (as shown in the cross-sectional view of Figure 6). In both the first and second designs, the electrolyte flows first through the porous conductive layer with low weave density or thinness, and then through the porous conductive layer with high weave density or thickness. In this way, deposits are prevented from clogging the porous conductive layer that comes into contact with the electrolyte first, thereby ensuring a reaction area between the electrolyte and the porous conductive layer that comes into contact with the electrolyte later. Therefore, in other embodiments, the weave density and thickness of the porous conductive layer may be adjusted based on the position or orientation in which the electrochemical reaction electrodes are placed, as long as the electrolyte flows first through the porous conductive layer with low weave density and then through the porous conductive layer with high weave density.

[0027] This disclosure is not limited by the shape of the current collector, the shape of the porous conductive layer, or the design of the weave density and thickness of the porous conductive layer. Please refer to Figure 6. Figure 6 is a cross-sectional view of an electrochemical reaction electrode 10c according to a second embodiment of this disclosure. The main differences between the electrochemical reaction electrode 10c of this embodiment and the electrochemical reaction electrode 10 of the first embodiment are the shape of the current collector, the shape of the porous conductive layer, and the design of the weave density and thickness of the porous conductive layer. In this embodiment, the current collector 100c and the porous conductive layers 210c, 211c, 212c, and 213c of the electrochemical reaction electrode 10c are, for example, cylindrical in shape and arranged concentrically. The electrolyte may also flow outward in the electrochemical reaction electrode 10c along the radial flow direction R1 to R8 in Figure 6. Furthermore, one or more cylindrical channel layers (similar to the channel layer 400 of the first embodiment) may be present between the current collector 100c and the porous conductive layers 210c, 211c, 212c, and 213c to reduce radial resistance. The weave density of the porous conductive layers 210c, 211c, 212c, and 213c may decrease toward the inside, and the thickness of the porous conductive layers 210c, 211c, 212c, and 213c may also decrease toward the inside. Other features of the porous conductive layers 210c, 211c, 212c, and 213c can be understood by referring to the description of the first porous conductive layers 210, 211, and 212 or the second porous conductive layers 220, 221, and 222 of the first embodiment, and therefore will not be described again.

[0028] However, in some cases, if the pores of the porous conductive layer are large enough to prevent deposits from clogging the space through which the electrolyte flows, the porous conductive layer may have the same weave density.

[0029] Third Embodiment This disclosure is not limited by the structure of the clamp frame. See Figure 7, which is a schematic diagram of a clamp frame 500a according to a third embodiment of this disclosure. In this embodiment, the clamp frame 500a includes a frame body 510 and a first pressing body 520. That is, the clamp frame 500a of this embodiment does not include the second pressing body 530 of the first embodiment. The clamp frame 500 of the electrochemical reaction electrode 10 in the first embodiment may be replaced with the clamp frame 500a. In other embodiments, the clamp frame may include only one second pressing body and may not include a first pressing body. Alternatively, in other embodiments, the number of first and second pressing bodies may be adjusted according to actual requirements.

[0030] Fourth Embodiment The channel layer of this disclosure is not limited to being in direct contact with the current collector. See Figure 8. Figure 8 is a schematic side view of an electrochemical reaction electrode 10b according to a fourth embodiment of this disclosure. The only difference between the electrochemical reaction electrode 10b of this embodiment and the electrochemical reaction electrode 10 of the first embodiment is that the electrochemical reaction electrode 10b does not include a channel layer 400 that is in direct contact with the current collector 100 in Figure 1. In this embodiment, two opposing sides of the current collector 100 are in contact with the first porous conductive layer 212 and the second porous conductive layer 222, respectively.

[0031] According to the electrochemical reaction electrode disclosed in the above embodiment, at least two porous conductive layers are formed from carbon fiber fabric and laminated together, or the tensile strength of the porous conductive layers is in the range of 20 MPa to 4400 MPa, and the Young's modulus of the porous conductive layers is in the range of 1.0 GPa to 540 GPa. Therefore, the structural strength of the electrochemical reaction electrode is strong enough that it can undergo cleaning treatments such as water washing and ultrasonic stirring without damage. In this way, the electrochemical reaction electrode can be cleaned and reused while increasing the reaction rate to achieve a metal ion removal rate of at least about 50%, thereby significantly reducing the recycling cost of used electrolyte.

[0032] According to the experimental examples of this disclosure, carbon fiber fabrics of different weave densities (e.g., TC-55 from Formosa Plastics Co., Ltd., M40J from Toray Industries, Inc., or similar fiber materials) are used as porous conductive layers, including 1K / 0.16mm, 3K / 0.24mm, 6K / 0.34mm, 12K / 0.55mm, and 24K / 0.85mm (yarn count / thickness), and the porous conductive layers are arranged in the order of 1K / 3K / 6K / 12K / 24K / 12K / 6K / 3K / 1K, and carbon fiber paper (which may be understood as a channel layer and has a thickness of about 0.19mm) is used as a channel layer placed between the carbon fiber fabrics (which may be understood as a porous conductive layer), thereby completing the assembly of the electrochemical reaction electrode. Next, the electrochemical reaction electrode is placed in an electrolytic cell and subjected to first electropolishing for 40 hours at a current density of 1.0 ASD (amperes per square decimeter). In the first electropolishing, the iron ion removal rate can reach 50.9%. The carbon fiber fabric is then removed from the electrode and reused after undergoing a first cleaning process with ultrasonic stirring. New carbon fiber paper is then used to complete the assembly of the electrochemical reaction electrode. The second electropolishing is performed under the same conditions as the first electropolishing, and the iron ion removal rate can reach 52.2%. The carbon fiber fabric is then removed from the electrode and reused after undergoing a second cleaning process with ultrasonic stirring. New carbon fiber paper is then used to complete the assembly of the electrochemical reaction electrode. In the subsequent electropolishing, performed under the same conditions as the first electropolishing, the iron ion removal rate can reach 51.8%. As a result, after reuse following a cleaning process (e.g., water washing or ultrasonic stirring), the iron ion removal rate of the electrochemical reaction electrode disclosed in the above embodiment changes by less than 2%, and in some cases may even increase by 2%. Therefore, the electrochemical reaction electrode disclosed in the above embodiment can be cleaned and reused without reducing the electrolytic efficiency.

[0033] It will be apparent to those skilled in the art that various modifications and changes can be made to the disclosed embodiments. This specification and the examples are to be considered merely illustrative, and the true scope of this disclosure is intended to be indicated by the following claims and their equivalents.

Claims

1. An electrochemical reaction electrode comprising at least two porous conductive layers formed from carbon fiber fabric and laminated together.

2. The electrochemical reaction electrode according to claim 1, wherein the at least two porous conductive layers have different weaving densities.

3. Equipped with an additional current collector, The electrochemical reaction electrode according to claim 1, wherein the at least two porous conductive layers are laminated on one side surface of the current collector.

4. The electrochemical reaction electrode according to claim 3, wherein the weaving density of one of the at least two porous conductive layers located near the current collector is different from the weaving density of the other of the at least two porous conductive layers located far from the current collector.

5. The electrochemical reaction electrode according to claim 4, wherein the weave density of the other of the at least two porous conductive layers located far from the current collector is lower than the weave density of the one of the at least two porous conductive layers located near the current collector.

6. The electrochemical reaction electrode according to claim 3, wherein the thickness of the other of the at least two porous conductive layers located far from the current collector is less than the thickness of one of the at least two porous conductive layers located near the current collector.

7. The electrochemical reaction electrode according to claim 3, wherein the current collector has a first surface and a second surface opposite to each other, and the at least two porous conductive layers comprise a plurality of first porous conductive layers and a plurality of second porous conductive layers, the plurality of first porous conductive layers are laminated on the first surface and the plurality of second porous conductive layers are laminated on the second surface.

8. The electrochemical reaction electrode according to claim 1, further comprising a plurality of end conductive films, wherein each of the at least two porous conductive layers comprises a plurality of interwoven fiber bundles, and each of the plurality of end conductive films is disposed at at least one end of the plurality of fiber bundles.

9. The electrochemical reaction electrode according to claim 1, further comprising at least one channel layer disposed between the at least two porous conductive layers, wherein the at least one channel layer is conductive fiber paper or conductive fiber yarn.

10. An electrochemical reaction electrode comprising at least one conductive porous conductive layer, wherein the tensile strength of the at least one porous conductive layer is in the range of 20 MPa to 4400 MPa, and the Young's modulus of the at least one porous conductive layer is in the range of 1.0 GPa to 540 GPa.

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