JP2008021521A - Fuel cell reaction analyzer and fuel cell operation state monitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell reaction analyzer capable of quickly analyzing the anode oxidation reaction of fuel and to provide a fuel cell operation monitor capable of quickly monitoring the operation state of a fuel cell. <P>SOLUTION: The fuel cell reaction analyzer analyzes the oxidation reaction of fuel in an anode 43, and includes at least a probe 46 installed in the vicinity or on the surface of the anode 43 for introducing the component of gas and liquid; a mass spectrometer 47 for analyzing the component introduced from the probe 46; a differential pumping device for exhausting the inside of the mass spectrometer 47; and piping through which the component introduced from the probe 46 is transferred to the mass spectrometer 47. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell reaction analyzer and a fuel cell operating state monitoring device.

  A fuel cell using hydrogen gas as a fuel generally provides a high output density. In particular, a solid polymer electrolyte fuel cell (PEFC) using hydrogen fuel is a power source for a high-speed moving body such as an electric vehicle or a distributed type. Expected as a power source.

  In general, in a solid polymer electrolyte fuel cell using hydrogen as a fuel, a membrane electrode comprising two electrodes, an anode (fuel electrode) and a cathode (oxygen electrode), and a solid polymer electrolyte membrane (PEM) sandwiched between them. A joined body (MEA) is formed, and a plurality of these are stacked as a cell unit to form a stack. Hydrogen is supplied to the anode of the cell unit and oxygen or air is supplied to the cathode as an oxidant, and an electromotive force is obtained by an oxidation reaction or a reduction reaction generated at each electrode.

  In order to activate the electrochemical reaction at the electrode, a platinum catalyst is used for the electrode in most cases, and protons (hydrogen ions) generated at the anode are conducted to the cathode through the solid polymer electrolyte membrane, Electricity is generated. The solid polymer electrolyte fuel cell using hydrogen as a fuel has many problems to be solved in the storage and transportation of hydrogen fuel, the method of supplying fuel, etc. It is generally recognized that it is unsuitable for personal use. Recently, as a technology for solving these problems and realizing a small and light fuel cell, a fuel cell that generates electricity by directly oxidizing an organic liquid fuel has attracted attention recently. One form of the direct alcohol fuel cell (DAFC) is a power cell configuration similar to that of a solid polymer electrolyte fuel cell, in which alcohol is directly supplied to the anode as a fuel to perform an anodic oxidation reaction. is there. Direct methanol fuel cells (DMFCs) that generate electricity using aqueous methanol solutions are smaller and lighter than fuel cells that generate electricity using hydrogen and fuel cells that use hydrogen as fuel by reforming the fuel. Because of its superiority, it is highly expected as a power source for portable electronic devices and the like. However, the direct methanol fuel cell has a problem that the overvoltage of the anodic oxidation reaction of methanol is large. In the hydrogen fuel cell that generates power using hydrogen, the overvoltage of the oxygen reduction reaction at the cathode is large, but in DMFC, the overvoltage of the methanol oxidation reaction at the anode is larger than this.

  By the way, although it is known that a platinum catalyst is suitable for anodic oxidation of methanol or ethanol, it is also known that an alloy of platinum and ruthenium is more suitable (see Non-Patent Document 1). However, the use of an alloy of platinum and ruthenium for the anode is not sufficient for the anodic oxidation of alcohol fuels such as methanol and ethanol.

  For this reason, development of an electrode catalyst having output characteristics equivalent to or better than those of a direct methanol fuel cell is desired. For this reason, the mechanism of the alcohol anodic oxidation reaction of the direct alcohol fuel cell has been studied and many studies have been made for the purpose of developing an effective catalyst (see Non-Patent Documents 2 to 5). However, in the combination of elements constituting the catalyst, the energy density of an alcohol oxidation catalyst having practical performance, particularly ethanol having 2 carbons, isopropyl alcohol having 3 carbons (2-propanol), etc. A large alcohol fuel oxidation catalyst has not been realized. The reason for this is that the elucidation of the mechanism of the anodic oxidation reaction of alcohol is limited to a part of the understanding, the established theory has not been established, that is, the mechanism of the anodic oxidation reaction is not well understood. Moreover, it is mentioned that the optimal preparation method of the multi-component catalyst which implement | achieves the combination of the element system which comprises a highly active catalyst is not established.

  The electrode reaction of a fuel cell consists of an anode reaction and a cathode reaction. The cathode reaction is an oxygen reduction reaction, and in order to obtain appropriate power generation characteristics of the fuel cell, it is desirable that the overvoltage of the oxidation reaction at the anode is small and the anode reaction does not become the rate-determining factor of the overall reaction. At this time, the reaction of the anode when alcohol or an aqueous alcohol solution is used is a complicated reaction that cannot be explained by a surface reaction such as catalytic metal and hydrogen.

With regard to this point, representative knowledge is presented in Non-Patent Documents 4 and 5, but no established theory has been established by those skilled in the art. In direct methanol fuel cells (DMFC), the reason why methanol oxidation is rate limiting is that carbon monoxide (CO) generated in the process of anodic oxidation is one of the factors that reduce the reaction activity. It is said to be adsorbed on the electrode and poison the electrode catalyst mainly composed of platinum. In order to solve this problem, various electrode catalysts have been studied. In particular, when a Pt—Ru alloy is used, it is known that CO poisoning is reduced. In this case as well, the anode reaction is rate-limiting compared to the cathode reaction. At this time, even in Non-Patent Documents 2 to 5, although the anodic oxidation reaction of methanol has not been analyzed in detail, it is considered as follows when a platinum-ruthenium catalyst is used. In a direct methanol fuel cell, at the anode,
CH ₃ OH + H ₂ O → 6H ⁺ + 6e ⁻ + CO ₂
The reaction of
CH ₃ OH + xPt → Pt _x CH ₂ OH + H ⁺ + e ⁻
CH ₂ OH + xPt → Pt _x CHOH + H ⁺ + e ⁻
CHOH + xPt → Pt _x COH + H ⁺ + e ⁻
CHOH + xPt → Pt _x CO + 2H ⁺ + 2e ⁻
Pt _x CHOH + PtOH → HCOOH + H ⁺ + e ⁻ + xPt
It is thought that such reactions occur. At this time, COH (or HCO) and CO are strong adsorption species for platinum, and ruthenium is considered to exert the following actions.

Ru + H ₂ O → RuOH + H ⁺ + e ⁻
Pt _x COH + RuOH → CO ₂ + 2H ⁺ + 2e ⁻ + xPt + Ru
Pt _x CO ⁺ + RuOH → CO ₂ + H ⁺ + e ⁻ + xPt + Ru
On the other hand,
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O
It is thought that this reaction occurs.

  The anodic oxidation reaction in other alcohols, such as ethanol having 2 carbons, is more complicated because even the methanol having 1 carbon has the complicated reaction estimated as described above. For example, it is easily understood by those skilled in the art that it is described in detail on pages 800 to 802 of Non-Patent Document 3.

On the other hand, the anodic oxidation reaction of ethanol
C ₂ H ₅ OH + 3H ₂ O → 12H ⁺ + 12e ⁻ + 2CO ₂
Is expressed as a strong adsorption species to platinum, causing so-called poisoning, -COH, CO, -COOH, -CH _3, etc., dissociated species and intermediate products produced in the anode oxidation reaction of ethanol, for example , CH ₃ CH ₂ OH, CH ₃ CHO, CH ₃ COOH and the like.

  Thus, fuel cells, particularly direct alcohol fuel cells that directly anodically oxidize alcohol fuel, are highly active because the electrode reaction that forms the basis of the power generation reaction, that is, the reaction of the anode and cathode, is not known in detail. When developing a catalyst, there is a problem that basic ideas such as the guiding principle of catalyst design cannot be obtained, and the development method of trial and error must be relied upon. In the anodic oxidation reaction of an alcohol such as ethanol having a plurality of carbons, the intermediate reaction is more complicated than methanol. For example, what is happening quantitatively, although it is easily understood by those skilled in the art that the factors inhibiting the anodic oxidation of ethanol are the intermediate products, the amount of by-products, and the complexity. Is not understood.

  Non-Patent Document 6 discloses a DEMS technique (Differential Electrochemical Mass Spectroscopy) using mass spectrometry as an example of a method for investigating an anodic oxidation reaction. However, this method can investigate the anodic oxidation reaction of a catalyst half-cell (half-cell) fixed to the electrode substrate by a specific method, but has a problem that it cannot cope with various forms of catalyst fixation (support).

  Patent Document 1 discloses analysis of a fuel cell using mass spectrometry. However, this method uses an atmospheric pressure ionization method and is suitable for analyzing trace impurities, but has a problem that the analyzer is complicated and large. Furthermore, it can be applied to analysis of a power generation cell, but is not suitable for characteristic analysis of a half cell or a membrane electrode assembly (MEA).

Patent Document 2 has a description of the DEMS technique, but there is no disclosure data, and as with Non-Patent Document 6, it is limited to application to anodic oxidation of a half cell.
JP 2004-157057 A Special table 2006-501983 gazette Souza et al, Journal of Electroanalytical Chemistry, 420 (1997), 17-20, Performance of a co-electrodeposited Pel-Ru electrodeposited the electro-oxidized. Lamy et al, Journal of Power Sources, 105 (2002) 283-296, Regent advancements in the development of alcohol fuel cells (DAFC) Lamy et al, Journal of Applied Electrochemistry, 31, 799-809 (2001), Electrocatalytic oxidation of aliphatic alcohols: Application to the biodielectric group (FC). Zhu et al, Langmuir 2001, 17, 146-154, Attenuated Total Reflection-Fourier Transform Infrared Study of Methane Oxidation on Spun Pt Wasmas et al, Journal of Electrochemical Chemistry 461 (1999), 14-31, methanol oxidation and direct methanol fuel cells: a selective review T.A. Handbook of Fuel Cells- Fundamentals, Technology and applications; Volume2: electrocatalysis; John Wiley & Sons, Ltd. (2003), ISBN: 0-471-49926-9; Chapter 41 “Methanol and CO electrooxidation”, 603-624.

  However, in the above prior art, a volatile component remaining or dissolved in a liquid or an object containing a liquid is identified (identified) by taking it out using a syringe and then analyzing it with an analysis device. Analyzes related to electrode reactions cannot be performed quickly. That is, the anodic oxidation reaction and the reaction analysis in the power generation cell of the fuel cell cannot be performed quickly, and as a result, it is not possible to perform an appropriate catalyst design or cell design test or efficient development. Furthermore, in order to improve the power generation characteristics of the fuel cell, regardless of the form of the reactive surface such as a catalyst that plays an important role in the electrode reaction, a half cell, a membrane electrode assembly (MEA), a power generation cell, and In an electrode reaction at each stage in a power generation system, a highly versatile analyzer for detecting a substance involved in the reaction and leading to an optimum design has not been obtained. In particular, in a direct alcohol fuel cell, the reaction in the solution is very complicated, and thus reaction analysis is an essential requirement. In addition, by knowing the mass balance at the fuel inlet and outlet of the fuel cell, the dissipation (leakage) of the fuel and oxidant, the crossover amount of the fuel, and the stoichiometric state of the electrode reaction, A device for quickly monitoring the operating state of the fuel cell, such as power generation efficiency, has not been obtained.

  In view of the above-described problems of the prior art, the present invention provides a fuel cell reaction analyzer capable of quickly analyzing the anodic oxidation reaction of fuel and a fuel cell capable of quickly monitoring the operating state of the fuel cell. It aims at providing a driving | running state monitoring apparatus.

  The invention according to claim 1 is a fuel cell reaction analyzer for analyzing an oxidation reaction of fuel at an anode, a probe provided near or on the surface of the anode for introducing gaseous and liquid components, and introduced from the probe. And a differential exhaust system that exhausts the inside of the mass spectrometer, and a pipe that transports the component introduced from the probe to the mass spectrometer. .

  According to a second aspect of the present invention, in the fuel cell reaction analyzer according to the first aspect, the probe comprises a porous polymer membrane.

  A third aspect of the present invention is the fuel cell reaction analyzer according to the first or second aspect, further comprising an electrochemical measurement device capable of synchronizing the analysis operation and the measurement operation of the mass spectrometer. Features.

  A fourth aspect of the present invention is the fuel cell reaction analyzer according to any one of the first to third aspects, wherein the fuel contains one or more alcohols.

  The invention according to claim 5 is a fuel introduction part for introducing fuel to be supplied to the anode, a fuel discharge part for discharging fuel supplied to the anode, an oxidant introduction part for introducing oxidant to be supplied to the cathode, and a supply to the cathode. In a fuel cell operating state monitoring device for monitoring the operating state of a fuel cell having an oxidant discharge part for discharging the oxidized oxidant, at least one of the fuel introduction part, the fuel discharge part, the oxidant introduction part and the oxidant discharge part A probe for introducing gas and liquid components, a mass spectrometer for analyzing the components introduced from the probe, a differential exhaust system for exhausting the interior of the mass spectrometer, and a probe introduced from the probe And at least a pipe for transporting the components to the mass spectrometer.

  A sixth aspect of the present invention is the fuel cell operation state monitoring apparatus according to the fifth aspect, wherein the probe includes a porous polymer film.

  A seventh aspect of the present invention is the fuel cell operation state monitoring apparatus according to the fifth or sixth aspect, wherein the fuel contains one or more alcohols.

  According to the present invention, there are provided a fuel cell reaction analysis device capable of quickly analyzing an anodic oxidation reaction of a fuel and a fuel cell operation state monitoring device capable of quickly monitoring an operation state of the fuel cell. Can do.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  First, the structure of the fuel cell used in the present invention will be described.

  FIG. 1 shows a single cell structure constituting a single component of a general solid polymer electrolyte fuel cell. The fuel cell shown in FIG. 1 is provided with an electrolyte membrane 2 between housings 1a and 1b, and an anode 3 (fuel electrode) so that the electrolyte membrane 2 is sandwiched between housings 1a and 1b. And a cathode 4 (air electrode). Further, a fuel supply unit 5 and an oxidant supply unit 6 are provided outside the anode 3 and the cathode 4, respectively. As the fuel, hydrogen gas, reformed gas fuel, or the like can be used, and as the oxidant, air, oxygen, hydrogen peroxide, or the like can be used.

  The electrolyte membrane 2 can be either an anion or a cation conduction type, but a proton conduction type is preferably used. As the electrolyte membrane 2, a known material such as a polymer membrane such as a perfluoroalkylsulfonic acid polymer can be used.

  As the anode 3 and the cathode 4, porous carbon paper coated with platinum or an alloy catalyst containing platinum as a main component can be used, but it is a porous material having conductivity and inhibits diffusion of fuel and oxidant. If not, materials other than porous carbon paper can be used. A membrane electrode assembly (MEA) is formed by sandwiching the electrolyte membrane 2 between the anode 3 and the cathode 4 or joining the three members by hot press, cast film formation, or the like. be able to. A water repellent such as polytetrafluoroethylene (PTFE) can be added to or laminated on the porous carbon paper as necessary.

  A fuel introduction part 21 for introducing fuel is provided below the fuel supply part 5, and a fuel discharge part 22 for discharging unreacted fuel and water is provided above. At this time, a forced intake means and / or a forced exhaust means may be provided.

  An oxidant introduction unit 23 for introducing an oxidant is provided above the oxidant supply unit 6, and an unreacted oxidant and a product (in many cases, water) are discharged below the oxidant supply unit 6. An oxidant discharge part 24 is provided for this purpose. At this time, a forced intake means and / or a forced exhaust means may be provided. Moreover, you may provide the natural convection port of air in the housing | casing 1a.

  FIG. 2 shows a single cell structure of a direct alcohol fuel cell. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. The fuel cell shown in FIG. 2 has the same configuration as that of FIG. 1, but an anode 3 A having an electrode catalyst for alcohol oxidation is used instead of the anode 3. The electrode catalyst may be any of single crystal, polycrystal, and amorphous, and may be a structure in which each element is alloyed or an aggregate of fine particle clusters. This electrode catalyst can be used alone as the anode 3A, but can also be supported on a conductive support and used as an electrode catalyst structure. Examples of the conductive support include metal thin films such as gold, platinum, stainless steel and nickel, mesh or sponge metal films, conductive materials, carbon fine particles (fine powder), conductive materials such as titanium oxide, silica and tin oxide. Include particles.

  As a method for forming the electrode catalyst structure, a gas phase such as a PVD (Physical Vapor Deposition) method other than the sputtering method such as a sputtering method, a vacuum vapor deposition method, a gas evaporation method, or a CVD (Chemical Vapor Deposition) method such as a thermal CVD method is used. Synthetic methods (substantially synonymous with vacuum thin film fabrication methods) can be applied, but in addition to these, known chemical or electrochemical methods such as electrolytic plating, electroless plating, and impregnation methods can also be applied. .

  The cathode 4 can be formed by bringing carbon particles carrying platinum into a well-mixed state together with an ion conductive material and contacting the electrolyte membrane 2. At this time, the ion conductive material is preferably the same material as the electrolyte membrane 2. As a method for bringing the cathode 4 into contact with the electrolyte membrane 2, methods such as hot pressing and cast film formation can be used. As the cathode 4, a noble metal or a metal on which it is supported, an organometallic complex, or a material obtained by firing this may be used.

  The fuel supply unit 5 may be a fuel storage unit that stores alcohol fuel, or may be in communication with a fuel storage unit that stores alcohol fuel provided outside. The alcohol fuel is agitated by natural convection and / or forced convection, but if necessary, forced convection means may be provided.

  A fuel introduction part 21 for introducing alcohol fuel is provided below the fuel supply part 5, and a fuel discharge part 22 for discharging unreacted fuel, water and carbon dioxide is provided above. It has been. At this time, a forced intake means and / or a forced exhaust means may be provided.

  The alcohol fuel is preferably alcohol alone or a mixture of alcohol and water, but in general, methanol, ethanol, isopropanol, etc. sold in large quantities as organic liquid fuels are used. When these are used as a mixture with water, crossover can be effectively suppressed, and more favorable cell electromotive voltage and output can be obtained.

  The fuel cell shown in FIGS. 1 and 2 is a single cell. However, in the present invention, a single cell may be used, or a mounted fuel cell in which a plurality of single cells are connected in series and / or in parallel is used. May be. When connecting multiple single cells, bipolar plates with fluid passage grooves in expanded graphite, bipolar plates with a mixture of carbon material such as expanded graphite and heat resistant resin, metal plates such as stainless steel base Alternatively, a connection method using a bipolar plate such as a bipolar plate coated with an oxidation resistant film and a conductive film may be employed, or a planar connection method may be employed. Furthermore, other known connection methods may be employed.

  FIG. 3 shows an example of the fuel cell reaction analyzer of the present invention. The reaction system 30 of the electrode reaction in the solution contains dissolved volatile components and products generated by the electrode reaction, and a probe 31a is installed in the reaction system 30 to detect them. When the electrode reaction is performed in an electrolyte solution, the electrolyte solution is usually acidic or alkaline, but in order to ensure resistance to these, the probe 31a is made of an acid-resistant and alkali-resistant material such as a fluororesin. It is preferable to be configured. As shown in FIG. 3B, the probe 31a is sealed by an O-ring 31c (manufactured by Viton) whose surface is covered with a fluororesin, and is provided on the surface of the anode 31b. As the probe 31a, it is possible to use a porous polymer membrane having a function of making it difficult to pass moisture, that is, a so-called gas-liquid separation effect, while easily taking in volatile components and electrode reaction products dissolved from the reaction system 30. In FIG. 3, a porous PTFE membrane having a thickness of about 100 μm is used. The average pore diameter of the porous polymer membrane is preferably 0.2 to 1.0 μm, particularly preferably 0.5 μm. The material of the porous polymer membrane is not limited to PTFE as long as it has a gas-liquid separation action.

  The probe 31a is connected to a vacuum piping, and is connected to the mass spectrometer 39 via a stop valve 32 and an introduction valve 33 (flow rate adjustment type). The inside of the mass spectrometer 39 is exhausted to a high vacuum during analysis by a differential exhaust system using a plurality of turbo molecular pumps 37 and auxiliary rotary pumps 38. The mass spectrometer 39 is provided with an orifice 36 so that the pressure does not increase suddenly even if the amount of the sample gas introduced from the probe 31a increases, and the amount of the sample gas introduced into the mass spectrometer 39 is small. Limited. Further, when the amount of sample gas introduced from the probe 31a is large, bypass exhaust is performed by the bypass valve 34 (flow rate adjustment type) and the rotary pump 35, and a predetermined pressure can be maintained. Since the mass spectrometer 39 may not be used when the pressure in the system becomes high, it is interlocked by a pressure measuring instrument (not shown) such as a vacuum gauge. Although not shown in FIGS. 4 to 7, as in FIG. 3, the probe is connected to a vacuum piping, and the inside of the mass spectrometer is high during analysis by a differential exhaust system. Exhausted to vacuum.

  The mass spectrometer 39 is composed of a system mainly including a mass spectrometer, and discriminates a sample gas by its mass-to-charge ratio (m / z: m is mass and z is ion valence). Mass spectrometers include magnetic mass spectrometers, time-of-flight mass spectrometers, ion trap mass spectrometers, etc., but high-speed mass sweeping, ease of operation, compactness, portability, and other measurements In consideration of measurement, influence of electromagnetic noise on the analyzer, etc., a quadrupole mass spectrometer is preferable.

  The quadrupole mass spectrometer includes an ionization unit, a mass separation unit, and an ion detection unit. In the ionization unit, as in a general magnetic field mass spectrometer, ionization is performed by colliding thermal electrons with the sample gas introduced into the ionization unit by an electron impact method. Mass separation is performed according to the mass-to-charge ratio of ions by performing an electrical sweep. In a quadrupole mass spectrometer, four circular or elliptical metal electrodes are precisely opposed to each other, and a quadrupole electric field is formed by applying high frequency and direct current waves to the four electrodes. By doing so, mass separation is performed. As a method for ionizing (ionizing) a sample gas, atmospheric pressure ionization, which is a soft ionization method, is suitable in consideration of fragment generation. However, in the atmospheric pressure ionization method using ion-molecule reaction, primary ions are Discharge for generation and an inert gas for discharge are required. For this reason, it is preferable to use the electron impact method which can be ionized simply. In this method, fragment ions are generated when ionizing a sample gas depending on ionization conditions. However, in the present invention, since many sample gases such as fuel and oxidant are known, this is an obstacle. There are few things.

  Although the electrode reaction reaction system 30 in the solution has been described with reference to FIG. 3, the fuel cell reaction analyzer of the present invention can be used for other purposes, and the probe is included in the solution or contains the solution. Except for being introduced into an object, for example, a fermenter, orange, or peach pulp, by adopting the same configuration as in FIG. It is possible to capture and analyze specific substances important for quality control.

  FIG. 4 shows another example of the fuel cell reaction analyzer of the present invention. The fuel cell reaction analyzer shown in FIG. 4 is an apparatus for analyzing the electrode reaction of a half cell, and an electrode reaction is performed using a glass three-electrode electrolytic cell 40. The electrolytic cell 40 is filled with an electrolyte solution 41 (for example, a 0.5 M sulfuric acid aqueous solution). When an anodic oxidation of alcohol is performed, an alcohol having a predetermined concentration is mixed with the electrolyte solution 41. As the anode 43, a gold or glassy carbon substrate on which a catalyst is supported can be used. When the catalyst is supported, an ink-like mixture (catalyst ink) in which the conductive carbon fine particles supporting the catalyst and the ion conductive polymer are mixed may be applied and dried, or by a film formation method such as sputtering. The catalyst may be formed in the porous layer. As the catalyst, it is possible to use alloys with other metals such as Ru, Sn, and Ir based on Pt, alloys with transition metals, oxides thereof, and the like.

  In the electrolysis cell 40, a diaphragm 42 (porous glass), a reference electrode 44, a cathode 45, and a rugin tube 49 are disposed at predetermined positions according to a normal measurement method. The electrode reaction performed in the electrolytic cell 40 is controlled by the electrochemical measuring device 48, and electrochemical measurements such as cyclic voltammetry (CV) can be performed. The product of the oxidation reaction at the anode 43 is contained in the solution, but is introduced into the mass spectrometer 47 through the probe 46. At this time, the probe 46 is different from the probe 31 a shown in FIG. 3B in that it is provided in the vicinity of the anode 43. At this time, the distance between the anode 43 and the probe 46 is not particularly limited, but is preferably 0 to 5.0 mm in order to efficiently introduce the product of the oxidation reaction in the anode 46 from the probe 46. -1.0 mm is more preferable. The mass spectrometer 47 has the same configuration as that shown in FIG. 3, but is directly connected to the electrochemical measurement device 48 and can be synchronized with the operation of the electrochemical measurement device 48. Specifically, as shown in FIG. 14 (a), an I / O connector of an electrochemical measuring device HZ-5000 (manufactured by Hokuto Denko) and a mass spectrometer having a computer and a control system are provided in a mass spectrometer. A digital input / output board (DIO board) of the control / data processing apparatus is connected. Specifically, as shown in FIG. 14 (b), the digital output signal of the CV measurement start / end output from the electrochemical measurement device is sent to the interface of the mass spectrometry control / data processing device via the input / output interface. The TTL level signal is received and taken into the computer software of the mass spectrometer, and the analysis start / end of the mass spectrometer is synchronized with the electrochemical measurement device.

  FIG. 5 shows another example of the fuel cell reaction analyzer of the present invention. The fuel cell reaction analyzer shown in FIG. 5 analyzes a product generated by an electrode reaction performed using the membrane electrode assembly 51. The membrane electrode assembly 51 has a structure in which the electrolyte membrane 51a and the anode 51b are joined by hot pressing or the like. In the reaction cell 50 made of Teflon (registered trademark), the left and right systems are separated through the electrolyte membrane 51a constituting the membrane electrode assembly 51. The electrolyte membrane 51a is sealed with an appropriate sealing material, and a reference electrode 52, a cathode 53, and an electrolyte solution 54 are disposed at predetermined positions on the side of the electrolyte membrane 51a in the reaction cell 50. The anode 51b side is filled with an alcohol aqueous solution 55, and the anodic oxidation of the alcohol is performed. The reaction cell 50 can be heated to a predetermined temperature by the heating device 57, and is thermally managed by a thermocouple or a thermometer (not shown). At this time, the anode 51b, the reference electrode 52, and the cathode 53 are each connected to the electrochemical measurement device 58, and the electrochemical measurement device 58 is directly connected to the mass spectrometer 59. The product of the electrode reaction of the anode 51b is introduced into the mass spectrometer from the solution system via the probe 56, and the configuration of the probe 56, the method of introducing the product, and the analysis method are the same as in the case of FIG.

  FIG. 6 shows an example of the fuel cell operating state monitoring device of the present invention. The fuel cell operating state monitoring apparatus shown in FIG. 6 introduces sample gas from probes 21a and 22a provided in the fuel introduction part 21 and the fuel discharge part 22 of the fuel cell shown in FIG. By analyzing, the operating state of the fuel cell is monitored. By analyzing in this way, the ratio of the alcohol fuel introduced into the anode 3A and the alcohol fuel consumed by the power generation in the cell over time, the fluctuation of the alcohol consumption depending on the power generation conditions, the generation of the anodic oxidation reaction of alcohol The quantitative relationship between things can be grasped. When the sample gas is introduced from the probes 21a and 22a provided in the fuel introduction part 21 and the fuel discharge part 22, they are controlled by sampling valves (not shown), respectively. When analyzing the fuel introduction part 21, the sampling valve on the fuel introduction part 21 side is opened, and the sampling valve on the fuel discharge part 22 side is closed. When analyzing the fuel discharge part 22, the sampling valve on the fuel discharge part 22 side is opened, and the sampling valve on the fuel introduction part 21 side is closed. When analyzing the fuel introduction part 21 and the fuel discharge part 22 alternately at high speed, the sampling valves on the fuel introduction part 21 and fuel discharge part 22 side are alternately opened and closed at high speed. By analyzing in this way, the ratio of the alcohol fuel introduced into the anode 3A and the alcohol fuel consumed by the power generation in the cell over time, the fluctuation in consumption due to power generation conditions, and the quantitative relationship between the products are grasped. can do. Furthermore, if precise measurement is repeated, it becomes possible to grasp the stoichiometric deviation of the reaction due to power generation conditions and disturbance. The mass spectrometer 25 is the same as the configuration shown in FIG. 3, and the probes 21a and 22a are the same as the configuration shown in FIG. Further, although the fuel cell shown in FIG. 2 is used in FIG. 6, the fuel cell shown in FIG. 1 may be used.

  FIG. 7 shows another example of the fuel cell operating state monitoring device of the present invention. In FIG. 7, the same components as those in FIG. 6 are denoted by the same reference numerals, and the description thereof is omitted. If the fuel cell operation state monitoring apparatus shown in FIG. 7 is used, it is possible to quantitatively grasp the phenomenon in which the fuel supplied to the anode 3A permeates the cathode 4 and crosses over. Although alcohol fuel is not specifically limited, DMFC which supplies methanol aqueous solution is demonstrated below. When methanol crosses over from the anode 3A, it reacts with oxygen at the cathode 4 and causes the electrolyte membrane 2 to deteriorate. Therefore, the evaluation of the crossover amount is an important performance evaluation item for the DMFC. At this time, when evaluating the static crossover amount without generating the power of the fuel cell, the sample is taken from the probe 24a of the oxidant discharge unit 24 while flowing nitrogen or an inert gas through the oxidant introduction unit 23. Gas is introduced, and the amount of crossover trace methanol contained in the sample gas is detected by the mass spectrometer 25. Further, when evaluating the dynamic crossover amount while generating power from the fuel cell, methanol that has permeated through the electrolyte membrane 2 of the membrane electrode assembly (MEA) has a certain amount of dioxide due to the catalytic action of the cathode 4. Since it changes to carbon, the sample gas is introduced from the probe 24 a of the oxidant discharge unit 24, and a trace amount (approximately several tens of ppm order) of carbon dioxide contained in the sample gas is detected by the mass spectrometer 25. In this way, by grasping the quantitative relationship of the trace components contained in each sample gas of the fuel introduction unit 21, the fuel discharge unit 22, and the oxidant discharge unit 24, changes with time, and fluctuations due to power generation conditions, Design items for more efficient power generation can be clarified. Moreover, since the fuel crossover characteristic of an electrolyte membrane can be grasped, it can be used to improve the material properties of the electrolyte membrane. The probe 24a has the same configuration as that shown in FIG. 4, and when a sample gas is introduced from the probe 24a provided in the oxidant discharge unit 24, it is controlled by a sampling valve (not shown) as in FIG. Is done. In FIG. 7, the fuel cell shown in FIG. 2 is used, but the fuel cell shown in FIG. 1 may be used.

  6 and 7, a single cell of a fuel cell is used, but a practical fuel cell in which single cells are stacked may be used. This makes it possible to monitor leakage of hydrogen fuel, capture abnormal changes in moisture in the cell during fuel cell power generation, monitor changes in the power generation reaction, and monitor deviations from normal power generation conditions. It is possible to provide system monitoring data to a control system that issues an alarm and returns it to an appropriate operating state. The present embodiment is not limited to a fuel cell using hydrogen fuel, but a fuel cell such as a fuel cell using reformed hydrogen fuel, a direct methanol fuel cell (DMFC), or a direct alcohol fuel cell (DAFC). Can be applied to.

In the following reference examples and examples, the mass spectrometer uses a method called MID (Multi Ion Detection), and simultaneously detects and records a spectrum corresponding to a plurality of specific mass numbers.
[Reference Example 1]
FIG. 8 shows the result of measuring a trace amount of ethanol (volatile component) dissolved in the solution using the fuel cell reaction analyzer shown in FIG. In Reference Example 1, the anode 31b is not provided, and the probe 31a is used to introduce the sample gas from the solution, and a solution is used instead of the reaction system 30. Specifically, an ethanol aqueous solution of about 0.0003M (about 18 ppm) was prepared, and the probe 31a was inserted into the obtained solution. When the stop valve 32 was opened, a trace amount of ethanol was identified along with water. In addition, in order to identify ethanol, the main peak of ethanol whose mass to charge ratio (m / z) is 31 was used. When ethanol is ionized by the electron impact method, a spectrum pattern composed of several peaks (standard spectrum of ethanol) is obtained, and analysis was performed focusing on the main peak having the strongest intensity. The partial pressure ratio of ethanol to water was calculated from the spectrum of the sample gas introduced by opening the stop valve 32, and the background measured by closing the stop valve 32 was subtracted. Although the mass spectrum is displayed in partial pressure, the mass spectrometer signal is measured by the current value (ion current value). Therefore, if the instrument-specific parameters are calibrated as sensitivity, the ratio of the ion current value It is also possible to determine the composition ratio of the sample gas.
[Example 1]
FIG. 9 shows the same reaction using the fuel cell reaction analyzer shown in FIG. 4 for the electrochemical measurement (CV) of anodic oxidation in an electrolyte solution containing ethanol (0.5 M sulfuric acid aqueous solution) and the measurement by a mass spectrometer. The result carried out in the system is shown. In Example 1, instead of the anode 43 and the probe 46, a probe 31a provided on the surface of the anode 31b shown in FIG. Further, as the anode 31b, a porous layer in which carbon black and a fluorine-containing polymer are mixed is formed on carbon paper, and an electrode catalyst (Pt—Sn binary alloy catalyst) is fixed (supported) thereon. Was used. The catalyst was supported by applying and drying an ink-like mixture (catalyst ink) in which conductive carbon fine particles carrying a catalyst and an ion conductive polymer were mixed. At this time, the supported amount of the catalyst is about 1 mg / cm ² in terms of Pt. The anode 31b was immersed in an electrolyte solution containing ethanol, and a three-electrode electrolytic cell 40 was configured using gold (Au) lead wires in electrical contact with the anode 31b. In this way, electrochemical measurement (CV) was performed, and the reaction product was identified by the mass spectrometer 47.

In FIG. 9A, A indicates a specific change in mass spectrum according to CV of 8 cycles (the sweep speed is 10 mV / second) (see FIG. 9B), and when the CV sweep is stopped. The mass spectrum will not change. B shows the change in the specific mass spectrum when a constant potential (potential) is applied (see FIGS. 9C and 9D), and how the product changes. You can see easily. m / z = 43 is the main peak of acetic acid, and m / z = 44 is the peak of the parent ion of carbon dioxide or acetaldehyde. Since it corresponds to the sweep state, it is considered as an intermediate product or by-product of the anodic oxidation reaction of ethanol. It is considered that m / z = 29 is a superposition of fragment ions of various substances. However, since it corresponds to the sweep state of CV, the main peak of acetaldehyde, which is an intermediate product of ethanol anodic oxidation reaction, is probably large. It is thought that it is included.
[Example 2]
FIG. 10 shows the results of electrochemical measurement (CV) of anodic oxidation in an electrolyte solution containing methanol (0.5 M sulfuric acid aqueous solution) and measurement using a mass spectrometer in the same reaction system.
In Example 2, methanol was used as the fuel, a multi-component alloy catalyst of Pt—Ru—W—Mo was used as the electrode catalyst, and 8 cycles of CV (see FIG. 10B) and 5 cycles of CV were used. (See FIG. 10 (c)) Measurement was carried out in the same manner as in Example 1 except that (the sweep speed was 10 mV / second for all). Note that the mass spectrum does not change when the CV potential (potential) sweep is stopped. It is considered that m / z = 60 is the peak of the parent ion of methyl formate, and m / z = 46 is the peak of the parent ion of formic acid. 10 (d) and 10 (e) show enlarged views of C and D in FIG. 10 (a), respectively. When m / z = 44, it is considered that the parent ion peak of carbon dioxide, which is the final product of the anodic oxidation reaction of methanol, is probably contained.
Example 3
FIG. 11 shows the results of electrochemical measurement (CV) of anodic oxidation in an electrolyte solution containing methanol (0.5 M sulfuric acid aqueous solution) and measurement using a mass spectrometer in the same reaction system. In Example 3, the electrocatalyst was supported by a sputtering method, and CV (see FIG. 11C) of 2 cycles (E and F) (sweep speed was 2 mV / sec) was performed, and completely synchronized with this. The measurement was carried out in the same manner as in Example 2 except that the change in mass spectrum was recorded. From FIG. 11 (a), it can be seen that when the CV sweep rate is lowered, the mass spectrum changes depending on the noble potential direction (forward) and the base potential direction (return). Further, in FIG. 11B showing the partial pressure logarithmically, changes in methyl formate and formic acid, which are intermediate products of methanol anodic oxidation, and carbon dioxide, which is the final product, appear.
Example 4
FIG. 12 shows the results obtained by performing electrochemical measurement (CV) of anodic oxidation in an electrolyte solution containing ethanol (0.5 M sulfuric acid aqueous solution) and measurement by a mass spectrometer in the same reaction system. In Example 4, measurement was performed in the same manner as in Example 3 except that ethanol was used as the fuel and 20 cycles of CV were performed. m / z = 43 is the main peak of acetic acid, m / z = 44 is the peak of the parent ion of carbon dioxide, and m / z = 29 is the main peak of acetaldehyde. The main peak of acetaldehyde may overlap with other intermediate products and the fragment peak of ethanol, but since this peak change appears in synchronization with CV, this peak contains the main peak of acetaldehyde. It is thought that.
Example 5
FIG. 13 shows the results obtained by performing electrochemical measurement (CV) of anodic oxidation in an electrolyte solution containing ethanol (0.5 M sulfuric acid aqueous solution) and measurement by a mass spectrometer in the same reaction system. In Example 5, the measurement was performed in the same manner as in Example 4 except that a Pt—Sn alloy catalyst was used as the electrode catalyst, the electrode catalyst was directly supported on the probe 46, and five cycles of CV were performed. At this time, the catalyst was supported by spray-coating and drying an ink-like mixture (catalyst ink) in which the conductive carbon fine particles carrying the catalyst and the ion conductive polymer were mixed. The change in the mass spectrum thus obtained is the same as that in Example 4.

It is a figure which shows the single cell structure of a solid polymer electrolyte type fuel cell. It is a figure which shows the single cell structure of a direct alcohol type fuel cell. It is a figure which shows an example of the fuel cell reaction analyzer of this invention. It is a figure which shows the other example of the fuel cell reaction analyzer of this invention. It is a figure which shows the other example of the fuel cell reaction analyzer of this invention. It is a figure which shows an example of the fuel cell operating condition monitoring apparatus of this invention. It is a figure which shows the other example of the fuel cell operating condition monitoring apparatus of this invention. It is a figure which shows the measurement result of the reference example 1. FIG. It is a figure which shows the measurement result of Example 1. It is a figure which shows the measurement result of Example 2. It is a figure which shows the measurement result of Example 3. It is a figure which shows the measurement result of Example 4. It is a figure which shows the measurement result of Example 5. It is a figure which shows the example of a connection of an electrochemical measuring device and a mass spectrometer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Case 2 Electrolyte membrane 3, 3A Anode 4 Cathode 5 Fuel supply part 6 Oxidant supply part 21 Fuel introduction part 22 Fuel discharge part 23 Oxidant introduction part 24 Oxidant discharge part 21a, 22a, 24a, 31a, 46 , 56 Probe 25, 39, 47, 59 Mass spectrometer 31b, 43, 51b Anode 31c O-ring 32 Stop valve 33 Introduction valve 34 Bypass valve 35 Rotary pump 36 Orifice 37 Turbo molecular pump 38 Rotary pump 40 Electrolytic cell 41, 54 Electrolyte Solution 42 Diaphragm 44, 52 Reference electrode 45, 53 Cathode 48, 58 Electrochemical measuring device 49 Lugin tube 50 Reaction cell 51 Membrane electrode assembly 51a Electrolyte membrane 55 Alcohol aqueous solution 57 Heating device

Claims (7)

In a fuel cell reaction analyzer for analyzing the oxidation reaction of fuel at the anode,
A probe provided near or on the surface of the anode for introducing gas and liquid components; a mass spectrometer for analyzing the components introduced from the probe; and a differential exhaust system for exhausting the interior of the mass spectrometer. A fuel cell reaction analyzer comprising at least a pipe for transporting a component introduced from the probe to the mass spectrometer.   The fuel cell reaction analyzer according to claim 1, wherein the probe comprises a porous polymer membrane.   The fuel cell reaction analyzer according to claim 1 or 2, further comprising an electrochemical measurement device capable of synchronizing an analysis operation and a measurement operation of the mass spectrometer.   The fuel cell reaction analyzer according to any one of claims 1 to 3, wherein the fuel contains one or more alcohols. A fuel introduction part for introducing fuel supplied to the anode, a fuel discharge part for discharging fuel supplied to the anode, an oxidant introduction part for introducing oxidant supplied to the cathode, and an oxidant discharge for discharging the oxidant supplied to the cathode In the fuel cell operation state monitoring device for monitoring the operation state of the fuel cell having a section,
Provided in at least one of the fuel introduction part, the fuel discharge part, the oxidant introduction part and the oxidant discharge part, a probe for introducing gas and liquid components, and a mass spectrometer for analyzing the components introduced from the probe And a differential exhaust system that exhausts the inside of the mass spectrometer, and a pipe that transports the component introduced from the probe to the mass analyzer.   The fuel cell operating state monitoring apparatus according to claim 5, wherein the probe includes a porous polymer membrane.   The fuel cell operating state monitoring device according to claim 5 or 6, wherein the fuel contains one or more alcohols.

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