JP2009098027A - Multichannel flow double-electrode measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multichannel flow double-electrode measuring apparatus, capable of efficiently measuring and evaluating the electrochemical properties of a plurality of materials for a short time, which are different from others in any one among composition, structure, mechanical characteristics, or the like. <P>SOLUTION: A channel (flow path)-forming body is made up of a first block 1 and a second block 2, which are constituted of an electrolyte-resistant insulator, and a sheet spacer 3, which is inserted so as to be sandwiched by these blocks. A channel 4, in which an electrolyte flows is formed inside the channel-forming body, and a plurality of electrode pairs, each being constituted of electrodes 801, 802, are arranged side by side on the surface of a wall of the channel 4, perpendicular to the direction in which the electrolyte flows. In each electrode pair, constituted of the electrodes 801, 802, the electrode 801 disposed on the upstream side of the flow of the electrolyte, is used as a working electrode, and the electrode 802 which is disposed on the downstream side of the flow of the electrolyte, is used as a detection electrode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrochemical measurement apparatus effective for analysis of electrode reactions, and more specifically, novel developments in technical fields such as electrode catalysts for electrochemical reactions, electrodes for secondary batteries and fuel cells, various surface treatments, The present invention relates to a multi-channel flow dual electrode measuring apparatus useful for improvement.

  Primary battery, secondary battery, fuel cell, corrosion, plating, surface treatment, electrolysis, improving the level of research and development and industrial technology in the field of manufacturing and processing of substances by electrochemical reaction, and improving product performance In order to achieve this, it is essential to analyze the electrochemical electrode reaction and elucidate the phenomenon.

  In general, an electrode reaction proceeds through three processes: (1) diffusion of a reactant to the electrode surface, (2) charge transfer on the electrode surface, and (3) dissipation of the product from the electrode surface. The slowest process determines the electrode reaction rate. That is, it becomes a rate-limiting process of the electrode reaction.

  As an electrochemical device for elucidating the electrode reaction, a rotating electrode measuring device and a rotating ring disk electrode measuring device are used. The rotating electrode measuring apparatus is used by embedding a disk-shaped disk electrode in one end of a support tube made of an insulator and rotating it in an electrolytic solution. One end face in the axial direction of the buried disk electrode and the support tube is polished so as to be in the same plane. A rotating shaft is attached to the other end surface in the axial direction of the support tube, and this shaft is rotated by a motor. The disk electrode and the shaft are electrically connected through a thin wire. The rotating shaft is also connected to a measuring instrument such as a potentiostat through a brush that is in sliding contact with the shaft.

  When the disk electrode of the rotating electrode measuring device is immersed in the electrolyte and rotated, the electrolyte just below the disk electrode flows outward while drawing a vortex along the plane of the disk electrode. It is supplied to the disk electrode surface from a direction perpendicular to the electrode.

  The measurement method using the rotating electrode measuring device is an electrochemical measurement method for controlling the mass transfer rate in the process (1) and (3) of the electrode reaction, and the charge transfer rate in the process (2), that is, Useful when you want to analyze electrode activity quantitatively.

  In addition to the information obtained by the rotating electrode measuring device, a rotating ring disk electrode measuring device is used when it is desired to obtain quantitative knowledge about the reaction mechanism. In the rotating ring disk electrode measuring apparatus, concentric ring electrodes are provided outside the disk electrode of the rotating disk electrode measuring apparatus via a thin layer made of an insulator.

  When the disk electrode of the rotating ring disk electrode measuring device is rotated, a radial liquid flow is generated from the rotating shaft toward the ring electrode. The potential of the ring electrode is set so that reaction intermediates and products generated on the disk electrode can be oxidized or reduced. The potential of the disk electrode and the potential of the ring electrode are controlled independently with respect to a common reference electrode by a dual potentiostat.

  The measuring method using the rotating electrode measuring device and the rotating ring electrode measuring device are both useful methods, but in these measuring methods, it is difficult to gas seal the rotating shaft, so the measuring temperature is from room temperature to around 50 ° C. Limited. Further, since noise is generated at the brush contact portion, measurement up to a minute current is impossible.

  In recent years, channel flow double electrode measurement devices have attracted attention as a device that avoids these drawbacks and enables measurement up to a higher temperature range and measurement up to a minute current range in the absence of electrical noise. Is being used.

  In the channel flow double electrode measuring device, a channel (electrolyte flow path) is formed in a channel forming body made of an electrolyte-resistant insulator, and one working electrode and one detection electrode are provided on the inner wall of the channel. Buried. The working electrode and the detection electrode are embedded in the channel forming body with the working electrode positioned on the upstream side in the direction in which the electrolyte flows, and the inner surface of the inner wall of the channel and the electrode surface of the working electrode and the detection electrode are positioned on the same plane. So that it is polished. On the other hand, a counter electrode is provided on the other surface facing the surface in which the working electrode and the detection electrode of the inner wall of the channel are embedded, and a port connected to the reference electrode is provided.

  A portion including the channel forming body and a working electrode, a detection electrode, a counter electrode, and the like formed therein is called a channel flow electrode cell. The channel flow electrode cell, an electrolyte tank containing the electrolyte, a pump for supplying the electrolyte in the electrolyte tank into the channel of the channel flow electrode cell, and between the counter electrode and the working electrode and between the counter electrode and the detection electrode A channel flow double electrode measuring device is configured by a potentiostat that controls the voltage applied between the two.

  With this measurement device, when the measurement is performed with the electrolyte flowing through the channel in a laminar flow, accurate and reproducible measurement results can be obtained, and useful electrochemical knowledge can be obtained. . A rotating electrode measuring device, a rotating ring electrode measuring device, and a channel flow double electrode measuring device are disclosed in Non-Patent Document 1, for example.

In recent years, a polymer electrolyte fuel cell (PEFC) has attracted attention as a clean energy source, and research for achieving high performance and high reliability is being promoted for its practical use. One of the most important issues in achieving high performance and high reliability of PEFC is the development of a highly active cathode oxygen reduction catalyst. The true oxygen reduction activity of a practical high dispersion catalyst in the practical temperature range of PEFC ranging from room temperature to 110 ° C. and the production rate of hydrogen peroxide H ₂ O ₂ , which is a harmful byproduct, have a working electrode and a detection electrode. Non-Patent Documents 2 and 3 have already reported that accurate measurement can be performed using the channel flow double electrode measurement method.
The Electrochemical Society of Japan "Electrochemical Measurement Manual Basics" Publication Place Maruzen Co., Ltd. Date of issue April 5, 2002 (pages 127-141) H. Yano, E. Higuchi, H. Uchida, and M. Watanabe, J. Phys. Chem. B 110 (2006) 16544. H. Yano, J. Inukai, H. Uchida, M. Watanabe, PK Babu, T. Kobayashi, JH Chung, E. Oldfield, and A. Wieckowski, Phys. Chem. Chem. Phys, 8 (2006) 4932.

  With the rotating electrode measuring device, the rotating ring disk electrode measuring device, and the channel flow double electrode measuring device, a lot of electrochemical knowledge has been obtained, and the technology has progressed. However, in recent years, there has been a long-awaited demand for more rapid technological progress in a wide range of fields such as energy and the environment, and as a result, there is a strong demand for speeding up research and development. It has become. In order to speed up research and development, it is necessary to shorten the time required for electrochemical measurements.

  The object of the present invention is to enable measurement up to a high temperature region and measurement up to a minute current region, to speed up the measurement, and to make a total measurement as compared with the case of using a conventional channel flow double electrode measurement device. It is an object of the present invention to provide a multi-channel flow dual electrode measuring apparatus capable of greatly reducing time.

  The multi-channel flow double electrode measuring apparatus according to the present invention is provided with a channel through which an electrolytic solution flows in a channel forming body made of an insulator having an electrolytic solution resistance, and is arranged in the channel in the direction in which the electrolytic solution flows. A channel flow electrode cell having a configuration in which a plurality of electrode pairs each including two electrodes is provided and the plurality of electrode pairs are arranged in a direction perpendicular to the direction in which the electrolyte flows is provided.

  When configured as described above, it was confirmed that the measurement of the electrochemical electrode reaction can be accelerated and performed more quickly than when only one electrode pair is provided. For example, when the number of electrode pairs is 4, it has been confirmed that the time required for measurement can be reduced to ¼ compared to the case where only one electrode pair is provided.

  When the quantitative analysis of the electrode activity is performed by the multi-channel flow double electrode measuring apparatus according to the present invention and the quantitative knowledge about the reaction mechanism is obtained, the two electrodes constituting each of the electrode pairs are analyzed. The electrode disposed so as to be located upstream of the flow of the electrolyte generated in the channel and the electrode disposed so as to be located downstream are configured to act as a working electrode and a detection electrode, respectively. That is, it is possible to individually control the voltage applied to the electrode arranged to be upstream and the electrode arranged to be downstream, and measure the voltage and current. In this way, the electrodes respectively arranged on the upstream side and the downstream side of the flow of the electrolytic solution are used as the working electrode and the detection electrode.

  Similarly to the rotating electrode measuring apparatus, when it is sufficient to perform quantitative analysis of the electrode activity, the two electrodes constituting each of the electrode pairs can be configured to work as working electrodes. That is, a voltage controlled in common is applied to the electrode arranged to be located upstream of the electrolyte flow and the electrode arranged to be located downstream, so that the upstream of the electrolyte flow and Both electrodes arranged on the downstream side work as working electrodes.

  In order not to disturb the laminar flow of the electrolyte in the channel, the two electrodes constituting each electrode pair are a pair of wall portions of the channel facing in a direction perpendicular to the direction in which the electrolyte flows. It is preferable that the electrode surfaces of the two electrodes constituting each electrode pair are placed on the same plane as the inner surface of the one wall portion.

  According to the present invention, a plurality of electrode pairs composed of two electrodes arranged in the direction in which the electrolytic solution flows are provided in the channel, and the plurality of electrode pairs are arranged in a direction perpendicular to the direction in which the electrolytic solution flows. As a result, the measurement of the electrochemical electrode reaction can be greatly accelerated and the time required for the measurement can be greatly shortened. As described above, according to the present invention, various measurements in the electrochemical field can be performed in a short time, so that it is possible to meet a social demand for speeding up research and development.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
In the present embodiment, the channel constituting members constituting the channel are the first block 1 shown in FIG. 1, the second block 2 shown in FIG. 2, and the sheet spacer (sheet-like or thin plate) shown in FIG. Shaped spacer) 3. The first block 1, the second block 2, and the sheet spacer 3 are made of an insulating material having an electrolytic solution resistance such as polytetrafluoroethylene (PTFE) or an acrylic resin, and as shown in FIG. A channel in which the first block 1 is disposed on the second block 2 via the sheet spacer 3 and the electrolyte flows between the second block 2 and the first block 1 (inside the sheet spacer 3). 4 is formed.

  The second block 2 is formed of a rectangular plate, and a rectangular first groove extending in the width direction of the second block is formed in a portion near the one end 2a in the longitudinal direction and a portion near the other end 2b. 201 and a second groove 202 are formed. The 1st groove | channel 201 and the 2nd groove | channel 202 are provided in the state opened to the main surface 2c which faces the channel 4 of the 2nd block 2. As shown in FIG. Inside the portion of the second block 2 near the one end 2a, there is formed an electrolyte inflow hole 203 having one end 203a opened on the end surface on the one end side of the second block, and the other end of the electrolyte inflow hole 203 is formed. 203 b is opened in the groove 201 at the center in the longitudinal direction of the first groove 201. Inside the portion of the second block 2 near the other end 2b, an electrolyte outflow hole 204 having one end 204a opened at the end surface of the second block on the other end 2b side is formed. The other end 204 b of the second groove 202 is open in the groove 202 at the center in the longitudinal direction of the second groove 202. The main surface 2c of the second block 2 is formed with a rectangular gasket (O-ring) receiving groove 205 that surrounds the first groove 201 and the second groove 202 and a portion between both grooves.

  A counter electrode 5 made of a platinum wire penetrating the second block 2 is inserted into the opening into the second groove 202 at the other end of the electrolyte outflow hole 204 of the second block 2. Further, a reference electrode connection port 7 connected to the reference electrode is formed at a position facing a region where the electrode pairs 8a to 8d of the first block described later are provided. The port 7 is connected to a container provided with a reference electrode through a hole 7a provided in the second block 2 and a pipe (not shown).

  As shown in FIG. 1, the first block 1 is composed of a rectangular plate made of an electrolytic solution-resistant insulating material having the same length and width as the second block 2, and its longitudinal direction is In a state where the one end 1a and the other end 1b are aligned with the one end 2a and the other end 2b of the second block 2, respectively, and both ends in the width direction thereof are aligned with both ends in the width direction of the second block 2. It is arranged above the block 2. On the main surface 1c of the first block 1 that faces the main surface 2c of the second block 2, a rectangular gasket receiving groove 105 that is aligned with the gasket receiving groove of the second block 2 is formed. Further, in the region near the other end 1b of the main surface 1c of the first block 1, when the first block 1 is arranged on the second block 2, it is closer to the reference electrode connection port 7 side than the counter electrode 5. A plurality (four in the illustrated example) of electrode pairs 8a to 8d are embedded so as to face the position. As shown in FIG. 5, each electrode pair is composed of a pair of strip-shaped electrodes 801 and 802 arranged in the direction of the flow of the electrolyte in the channel 4 (arrow f direction). The strip-shaped electrodes 801 and 802 constituting each electrode pair have their longitudinal directions oriented in the direction perpendicular to the direction in which the electrolyte flows (the width direction of the first block 1 and the second block 2), and They are provided in parallel in a state where they are arranged in the direction in which the electrolyte flows.

  In order not to disturb the laminar flow of the electrolyte in the channel 4, the strip electrodes constituting each electrode pair have their respective electrode surfaces positioned on the same plane as the main surface 2 c of the first block 1. In this state, it is embedded in the first block 1. In order to avoid the vicinity of both ends in the width direction of the channel 4 where the laminar flow of the electrolyte solution may be disturbed, the series of electrode pairs 8a to 8d is formed between the electrode pairs 8a and 8b at the both ends and both ends in the width direction of the channel 4. They are provided with a sufficient space between them. Lead wires 901 and 902 are led out from the electrodes 801 and 802, respectively.

  The sheet spacer 3 is composed of a frame-like plate in which a rectangular plate having the same length and width as the second block 2 and the first block 1 is punched to form a rectangular hole 301, and the second block 2 2 and the first block 1 are arranged in a sandwiched state. A rectangular hole 301 in the second block 2 defines the contour shape of the channel 4. The rectangular hole 301 of the second block 2 is provided so as to be located inside the gasket housing grooves 105 and 205.

  As shown in FIG. 4, the second block 2, the sheet spacer 3, and the first block 1 in a state where the gasket 10 made of an elastic material having an electrolytic solution resistance is accommodated in the gasket accommodation grooves 105 and 205. The second block 2, the sheet spacer 3, and the first block 1 are screwed into the through bolts (not shown) penetrating through these four corners and the through bolts. The channel flow electrode cell 11 of the multi-channel flow double electrode device is configured by fastening with a nut.

  In the present embodiment, each electrode 801 disposed on the upstream side of the flow of the electrolytic solution is used as a working electrode, and each electrode 802 disposed on the downstream side of the electrolytic solution is used as a detection electrode. In this embodiment and the examples to be described later, the electrodes 801 of the electrode pairs 8a to 8d are used as the working electrodes, and the working electrodes respectively constituted by the electrodes 801 of the electrode pairs 8a to 8d are identified by the symbols W1 to W4. . Further, the electrodes 802 of the electrode pairs 8a to 8d are used as detection poles, and the detection poles respectively constituted by the electrodes 802 of the electrode pairs 8a to 8d are identified by reference numerals C1 to C4. In this example, each electrode 801 used as a working electrode is made of gold, and each electrode 802 used as a detection electrode is made of platinum.

As shown in FIG. 6, the electrolyte inflow hole 203 of the channel flow electrode cell 11 is connected to the discharge port of the pump 24 through the pipe 21, the flow meter 22 and the pipe 23. The suction port of the pump 24 is connected through a pipe 28 to the other end of a pipe 27 whose one end is inserted into an electrolyte solution 26 accommodated in an electrolyte solution tank 25. In addition, the electrolyte outlet hole 204 of the channel flow electrode cell 11 is connected through the pipe 30 to the other end of the pipe 29 having one end inserted in the electrolyte 26 in the electrolyte tank 25. A gas such as O ₂ or N ₂ is supplied into the electrolyte tank 25 through the pipe 31. Also. The reference electrode connection port 7 is connected through a pipe 32 to a container in which a reference electrode made of a reversible hydrogen electrode or the like is accommodated.

  The channel flow electrode cell 11, the electrolyte tank 25, the pump 24, the piping that connects them, the counter electrode 5 and each electrode 801 of the channel flow electrode cell, and between the counter electrode 5 and each electrode 802. The present invention is based on a dual potentiostat (not shown) that can individually control the voltage applied and measure the voltage applied to the electrodes 801 and 802 and the current flowing through the electrodes 801 and 802, respectively. A multi-channel flow double electrode measuring apparatus is constructed. In the present invention, “multiple” is used in the sense that a plurality of electrode pairs are provided.

  In the present embodiment, a channel forming body is constituted by the first block 1 and the second floc 2 made of an electrolytic solution-resistant insulator and the sheet spacer 3, and the first block 1 and the second block 2 The channel 4 is formed by interposing the sheet spacer 3 therebetween, but the channel can also be formed by providing a groove extending in the longitudinal direction on the main surface of one block. In the present embodiment, the electrode pairs 8a to 8d are provided in the first block 1, but these electrode pairs may be provided on the second block 2 side.

  That is, the channel flow electrode cell 11 used in the present invention is provided with a channel through which an electrolytic solution flows in a channel forming body made of an electrolytic solution-resistant insulator, and an electrode pair composed of two electrodes arranged in the direction in which the electrolytic solution flows. A plurality of electrode pairs are provided in the channel, and the electrode pairs are arranged in a direction perpendicular to the direction in which the electrolyte flows.

  If the channel flow electrode cell 11 is configured in this way, the electrochemical electrode reaction measurement can be accelerated and performed more quickly than when only one electrode pair is provided in the channel flow electrode cell. As a result, the time required for measurement can be greatly reduced compared to the case where only one electrode pair is provided.

  In the above embodiment, the electrode 801 of each electrode pair arranged on the upstream side of the electrolyte flow is used as a working electrode, and the electrode 802 arranged on the downstream side of the electrolyte flow is used as a detection electrode. Quantitative analysis of activity and quantitative knowledge about the reaction mechanism were made available, but if quantitative analysis of electrode activity should be performed, it should be positioned upstream of the electrolyte flow. It is also possible to apply a commonly controlled voltage to the electrode 801 arranged so as to be arranged and the electrode 802 arranged so as to be located on the downstream side so that both the electrodes 801 and 802 work as working electrodes. .

  In the above embodiment, the counter electrode 5 is configured by inserting a platinum wire into the opening of the electrolyte outflow hole 204 into the groove 202, but the portion of the main surface 2 c of the second block 2 near the groove 202. A counter electrode having a plate-like shape or a net-like shape can also be provided in a state of being embedded in the electrode.

  In the multi-channel flow dual electrode measuring apparatus of the present invention, the most technical concern is whether the reaction at one electrode pair affects the reaction at another adjacent electrode. . If this problem is solved, it can be said that the benefits of the present invention have been demonstrated.

  Therefore, a full-scale multi-channel flow dual electrode measuring device was manufactured, and it was examined whether or not the reaction at one electrode pair affects the reaction at another adjacent electrode. In this example, the channel flow electrode cell 11 having the configuration shown in FIGS. 1 to 4 was used, and the dimensions (unit: mm) of each part were set as shown in FIG.

  The blocks 1 and 2 and the sheet spacer 3 constituting the channel forming body were formed of PTFE (polytetrafluoroethylene). The thickness of the sheet spacer 3 was 0.5 mm, and a channel 4 having a height of 0.5 mm was formed inside the sheet spacer. Fluoro rubber was used as the gasket 10 for sealing the joints between the sheet spacer 3 and the first block 1 and between the sheet spacer 3 and the second block 2.

  In the first block 1, four electrode pairs 8 a to 8 d composed of an electrode (working electrode) 801 made of a gold plate and an electrode (detection electrode) 802 made of a platinum plate are connected to the flow of the electrolyte. Embedded in a direction perpendicular to the direction of. The dimensions of the respective portions of the electrodes 801 and 802 constituting the four electrode pairs were all set equal.

  As shown in FIG. 5, the width dimension of each electrode 801 and 802 is w, the length dimension is x1, the distance from one end of the electrode 801 to one end of the electrode 802 is x2, w = 4 mm, x1 = 1 mm, The distance between the electrodes 801 and 802 of each electrode pair was 0.5 mm (= x2-x1). The distance between the electrodes 801, 801,... Constituting the working electrodes W1 to W4 is 7 mm, and the distance between the electrodes 802, 802,.

  Further, the distance between the upstream end of the channel 4 and the electrode pair is defined as Ie in the drawing, and Ie = 80 mm. A counter electrode 5 made of a platinum wire was inserted in the center of the opening into the groove 202 of the electrolyte outflow hole 204.

As the electrolyte flowing in the channel 4, 1 mM K ₃ [Fe (CN) ₆ ] + 0.5 M K ₂ SO ₄ was used, and degassed with N ₂ gas for 1 hour or more before measurement. As a reference electrode, a KCl saturated Ag | AgCl electrode was used. As the pump 24 for circulating the electrolytic solution, a chemical gear pump (manufactured by Kyowa Kagaku Co., Ltd.) is used. By this pump 24, the electrolytic solution tank 25 -the pump 24 -the flow meter 22 -the channel flow electrode cell 11 -the electrolytic solution tank 25 The electrolyte was circulated along the electrolyte flow path, and the flow rate was measured with the flow meter 22 before the electrolyte flowed into the channel flow electrode cell 11.

First, in order to perform the reduction reaction at each electrode 801 used as a working electrode, the potential with respect to the reference electrode of the electrode 801 constituting the working electrode is set to a negative potential, and the potential of each electrode 801 is swept at a sweep rate of 20 mV / sec. The experiment for obtaining the convective voltammogram of the reduction reaction of [Fe (CN) ₆ ] ^3- at each electrode represented by the formula (1) was performed at room temperature while varying the average flow rate Um of the electrolyte.
[Fe (CN) ₆ ] ³⁻ + e ⁻ → [Fe (CN) ₆ ] ⁴⁻ (1)

As an example, FIG. 8 shows a convective voltammogram obtained with the working electrode W1 arranged at the extreme end. In the figure, curves a, b, c, d and e are obtained when the flow rate Um of the electrolyte is 11 cm / sec, 19 cm / sec, 25 cm / sec, 32 cm / sec and 47 cm / sec, respectively. As is clear from FIG. 8, the reduction current starts to flow around 0.37 V and reaches the diffusion limit current at about 0.1 V. As the flow rate Um of the electrolyte increased, the diffusion limit current value increased. It should hold the following equation between the velocity Um of the diffusion limiting current I _L and the electrolyte.
I _L = 1.165 × nF [Ox] w (Um D ² x1 ² / h) ^1/3 (2)

Here, n is the total number of reaction electrons, F is the Faraday constant, w is the width of the working electrode (4 mm), [Ox] and D are the reactive species in the solution (in this case, [Fe (CN) ₆ ] ^3- ), And x1 is the length of the working electrode (1 mm), and h is half the channel height (0.25 mm).

FIG. 9 shows the Um ^1/3 dependence of the limit current I _L measured at the working electrodes W1, W2, W3, and W4. FIG. 10 shows the limit current I _L measured at the detection electrodes C1, C2, C3, and C4. Of Um ^1/3 . The critical currents that were well matched within the experimental error were observed for all electrodes, and a linear relationship through the origin was obtained. Thus, it was confirmed that the electrolyte solution could be supplied to all the electrodes in a laminar flow state by the structure of the measuring apparatus of this example.

Next, while the reaction of the equation (1) is advanced at the working electrode, the potential of the detection electrode with respect to the reference electrode is set to 0.45 V vs. Ag-AgCl, and the current that oxidizes [Fe (CN) ₆ ] ⁴⁻ is measured. Then, the capture rate was obtained. FIG. 11 shows convective voltammograms of the working electrodes W1, W2, W3, W4 and the detection electrodes C1, C2, C3, C4. Responses in good agreement were obtained for the four working electrodes and the four detection electrodes. The capture rates determined from the ratio of the working electrode and detection electrode currents are summarized in Table 1 below. As is clear from the table, the combination of the working electrode and the detection electrode constituting each electrode pair had a capture rate of 0.29, but the action of the electrode pairs adjacent in the direction perpendicular to the electrolyte flow In the combination of the pole and the detection pole, the capture rate was zero.

  As described above, the most important thing in the multi-electrode system channel flow dual electrode measuring apparatus is that each detection electrode is in contact with the working electrode other than the working electrode immediately upstream of the electrolytic solution, that is, with respect to the electrolytic solution flow. The product of the working electrode located diagonally is not detected. In the multi-channel flow double electrode measuring apparatus of this example, as shown in Table 1, the detection sensitivity with respect to the working electrode located obliquely was zero. For example, when only the working electrode W2 is operated, the product is detected only in the detection electrode C2, and the detection electrodes C1 and C3 positioned obliquely with respect to the working electrode W2 are generated in the working electrode W2. No product was detected. Similarly, with respect to the other working electrodes W1, W3, and W4, the detection currents at the respective detection electrodes located obliquely are zero, and the excellent performance of the multi-channel flow double electrode measuring device according to the present invention is excellent. We were able to verify that everything was maintained.

As mentioned above, one of the most important issues for improving the performance and reliability of polymer electrolyte fuel cells (PEFC) is the development of a highly active cathode oxygen reduction catalyst. Channel flow with a pair of working electrode and detection electrode, with the true oxygen reduction activity of a practical high dispersion catalyst in the PEFC practical temperature range and the production rate of hydrogen peroxide H ₂ O ₂ which is a harmful byproduct Non-patent documents 2 and 3 have already reported that accurate measurement can be performed using the double electrode measurement method.

Therefore, using the multi-channel flow dual electrode measuring device shown in FIGS. 1 to 4 having four pairs of working electrodes and detection electrodes, four different high dispersion electrode catalysts are respectively provided on the four working electrodes W1 to W4. An experiment was conducted in which the oxygen reduction activity and the H ₂ O ₂ production rate of these four types of highly dispersed electrode catalysts were simultaneously measured. In the experiment, Hokuto Denko HA1010mM8S was used as a multi-potentiostat. Samples No. 1, No. 2, No. 3 and No. 4 were used as the PtCo / C highly dispersed catalysts uniformly dispersed in the working electrodes W1 to W4 made of gold. _{The 2} O ₂ production rate was measured simultaneously. As the electrolytic solution, a 0.1 M HCl ₄ electrolytic solution saturated with oxygen was used. The temperature of the electrolytic solution was 60 ° C., the flow rate Um of the electrolytic solution was 23 cm / sec, and the potential sweep rate was 0.5 mV / sec. FIG. 12 shows a convection voltammogram showing the relationship between the current flowing through the detection electrodes C1 to C4 and the potential of each detection electrode with respect to the reference electrode, and the relationship between the current flowing through the working electrodes W1 to W4 and the potential of each working electrode with respect to the reference electrode. FIG. 13 shows a convection voltammogram showing

From this experiment, it was found that PtCo alloy / C catalyst No. 1 showed the most positive rising potential. Moreover, it was shown that the catalyst No. 2 has the lowest H ₂ O ₂ production rate. This multi-channel flow double electrode measurement device maintains the same accuracy as the conventional channel flow double electrode measurement device, while greatly accelerating the test and greatly increasing the time required for the test (four electrode pairs). In this case, it was confirmed that it could be shortened to 1/4).

  In the above description, the number of electrode pairs is four. However, in the present invention, the number of electrode pairs may be two or more, and is not limited to the above embodiment and examples.

It is the bottom view which showed the 1st block which comprises the channel flow electrode cell used by embodiment of this invention. It is the top view which showed the 2nd block which comprises the channel flow electrode cell used by embodiment of this invention. It is the top view which showed the sheet | seat spacer which comprises the channel flow electrode cell used by embodiment of this invention. It is the longitudinal cross-sectional view which showed the structure of the channel flow electrode cell used by embodiment of this invention. It is the enlarged view which showed the structure of the electrode pair provided in the channel of a channel flow electrode cell in embodiment of this invention. It is the block diagram which showed roughly an example of the whole structure of the multi-channel flow double electrode measuring apparatus of this embodiment. It is explanatory drawing used in order to demonstrate the dimension of each part of the channel flow electrode cell used in the Example of this invention. It is the graph which showed the convection voltammogram acquired by one working electrode W1 when making the reduction reaction in a working electrode in the Example of this invention. In an embodiment of the present invention, Um ^1/3 dependence of critical current I _L were measured in four working electrode (Um flow velocity of the electrolytic solution) is a graph showing a. In an embodiment of the present invention, it is a graph showing the Um ^1/3 dependency of the limit current I _L measured at four detection electrode. In the Example of this invention, it is the graph which showed the convection voltammogram acquired by the working electrode and the detection electrode when the oxidation current was measured by four working electrodes, making a reduction reaction advance in four working electrodes. In an example of the present invention, four different highly dispersed electrocatalysts were dispersed and attached to four working electrodes, and the oxygen reduction activity and H ₂ O ₂ production rate of these four highly dispersed electrocatalysts were measured simultaneously. It is the graph which showed the convection voltammogram acquired by each detection pole when performing experiment to do. In an example of the present invention, four different highly dispersed electrocatalysts were dispersed and attached to four working electrodes, and the oxygen reduction activity and H ₂ O ₂ production rate of these four highly dispersed electrocatalysts were measured simultaneously. It is the graph which showed the convective voltammogram acquired at each working electrode when performing the experiment to do.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st block 2 2nd block 3 Sheet spacer 4 Channel 8a-8d Electrode pair 801,802 Electrode W1 thru | or W4 Working electrode C1 thru | or C4 Detection pole

Claims (3)

  A channel forming body made of an electrolyte-resistant insulator is provided with a channel through which the electrolyte flows, and a plurality of electrode pairs each including two electrodes arranged in the direction in which the electrolyte flows are provided in the channel, Is a multi-channel flow double electrode measuring device provided with a channel flow electrode cell in which the cells are arranged in a direction perpendicular to the direction in which the electrolyte flows.   Of the two electrodes constituting each of the plurality of electrode pairs, one electrode arranged to be located upstream of the flow of the electrolytic solution generated in the channel and arranged to be located downstream The multi-channel flow double electrode measuring device according to claim 1, wherein the other electrode is configured to function as a working electrode and a detection electrode, respectively.   The multi-channel flow double electrode measuring apparatus according to claim 1, wherein two electrodes constituting each of the plurality of electrode pairs are configured to work together as working electrodes.

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