JP6672931B2 - Electrode catalyst ink manufacturing method and electrode catalyst ink manufacturing apparatus - Google Patents

Description

  The present invention relates to a method for producing an electrode catalyst ink and an apparatus for producing an electrode catalyst ink.

  A polymer electrolyte fuel cell used in a fuel cell vehicle or the like has a structure in which a membrane electrode assembly in which an electrochemical reaction proceeds is sandwiched between separators, and these are laminated. The membrane electrode assembly has an electrolyte membrane and an electrode catalyst layer disposed on a surface of the electrolyte membrane.

  There are various methods for forming the electrode catalyst layer, and one of them is a method using a transfer sheet. In this method, a liquid electrode catalyst ink is applied to a transfer sheet, dried to form an electrode catalyst layer on the transfer sheet, and then transferred to an electrolyte membrane, thereby transferring the electrode catalyst layer to the electrolyte membrane. To place.

  The electrode catalyst ink includes a solvent, an ionomer, and catalyst particles. The power generation performance of the membrane electrode assembly depends on the adsorption amount of the ionomer that contributes to the proton conduction effective for power generation to the catalyst particles. Specifically, if the amount of ionomer adsorbed on the catalyst particles is large, the proton conduction resistance decreases, and the power generation performance increases.

  Therefore, if the adsorption amount of the ionomer to the catalyst particles can be evaluated in the state of the electrode catalyst ink, the quality of the power generation performance of the membrane electrode assembly can be determined to some extent on the upstream side of the manufacturing process, but the ionomer adsorption amount can be easily evaluated. The method has not been established.

  For example, in Patent Literature 1, although evaluation is performed using a zeta potential as an index for a carbon powder dispersion, this conventional technique evaluates using a zeta potential as an index. And the amount of ionomer adsorbed on the catalyst particles was not evaluated. What is known from the evaluation by the prior art is that when the absolute value of the zeta potential is large, the repulsive force between the colloid particles is large and the dispersibility is high (it is difficult to aggregate), and the adsorption amount of the ionomer to the catalyst particles is small. It is not evaluated whether it is more or less.

  Therefore, the quality of the electrode catalyst ink cannot be determined unless the membrane electrode assembly is once manufactured and the actual power generation performance is measured, and the electrode catalyst ink is evaluated from the measurement result.

Japanese Patent No. 5093817

  However, in such an evaluation method, factors after the preparation of the electrode catalyst ink are included in the evaluation result, and the degree of the influence is unknown. Therefore, it cannot be said that the electrode catalyst ink is evaluated. If a defective electrode catalyst ink is used as it is based on an erroneous evaluation, a membrane electrode assembly that does not exhibit the desired power generation performance is produced, which may cause a reduction in yield.

  Then, the present inventors diligently studied a method for evaluating the quality of the electrode catalyst ink in a state of the ink. As a result, the present inventors have found that there is a correlation between the amount of ionomer adsorbed on the catalyst particles that contributes to the proton conduction and, consequently, the power generation performance, and the zeta potential of the catalyst particles, and utilize this correlation. To evaluate the electrode catalyst ink.

  That is, the present invention has been made based on a new finding which has not existed in the past. The present invention evaluates proton conductivity in the state of an electrode catalyst ink, and manufactures an electrode catalyst ink capable of improving the yield based on the evaluation. An object of the present invention is to provide a method and an apparatus for producing an electrode catalyst ink.

  According to the method for producing an electrode catalyst ink of the present invention for achieving the above object, at least a solvent, an ionomer, and catalyst particles are mixed to produce an electrode catalyst ink. In the method for preparing an electrode catalyst ink of the present invention, the zeta potential of the catalyst particles having the ionomer adsorbed on the surface is measured, and the amount of the ionomer adsorbed on the catalyst particles is determined using the zeta potential. In the method for producing an electrode catalyst ink of the present invention, when it is determined that the amount of ionomer adsorbed on the catalyst particles is small, the electrode catalyst ink is adjusted so that the amount of ionomer adsorbed increases.

  The electrode catalyst ink producing apparatus of the present invention for achieving the above object has a mixing section for producing an electrode catalyst ink by mixing at least a solvent, an ionomer, and catalyst particles. The apparatus for preparing an electrode catalyst ink of the present invention includes a zeta potential measurement unit that measures the zeta potential of the catalyst particles having ionomer adsorbed on the surface thereof, and an electrode catalyst that performs adjustment such that the zeta potential changes with respect to the electrode catalyst ink. An ink adjustment unit. The zeta potential measuring unit determines the amount of the ionomer adsorbed on the catalyst particles by using the zeta potential. When it is determined that the amount of the ionomer adsorbed on the catalyst particles is small, the electrode catalyst ink adjusting unit adjusts the electrode catalyst ink such that the amount of the ionomer adsorbed increases.

  According to the present invention, based on the correlation between the amount of ionomer adsorbed on the catalyst particles and the zeta potential, an evaluation of the proton conductivity effective for power generation is performed in the state of the electrode catalyst ink, and based on the evaluation result, An electrocatalyst ink having good proton conductivity is provided. For this reason, it is possible to prevent the defective electrode catalyst ink from being used in a subsequent step, and to improve the yield.

It is a figure showing the outline of the electrode catalyst ink manufacture device of a 1st embodiment. It is a figure showing an example of a dispersing machine. It is a figure showing other examples of a dispersing machine. It is a figure which shows another example of a dispersing machine. It is a flowchart which shows the outline | summary of the electrode catalyst ink manufacturing method of 1st Embodiment. It is a figure which shows typically the state which ionomer adsorb | sucked to the catalyst particle. It is a figure which shows typically the state where the adsorption amount of the ionomer to a catalyst particle increased. 4 is a graph showing a correlation between the amount of ionomer adsorbed on catalyst particles and zeta potential. It is a figure showing the outline of the electrode catalyst ink production device of a 2nd embodiment. It is a flowchart which shows the outline | summary of the electrode catalyst ink manufacturing method of 2nd Embodiment. It is a figure showing the outline of the electrode catalyst ink manufacture device of a 3rd embodiment. It is a flowchart which shows the outline | summary of the electrode catalyst ink manufacturing method of 3rd Embodiment. It is a graph which shows the particle size distribution of ionomer measured by changing a heating temperature. It is a graph which shows the relationship between the heating temperature of an ionomer, and a zeta potential difference. It is a graph which shows the zeta potential difference at the time of changing the presence or absence of heating before and at the time of mixing of ionomer and other components. It is a figure showing the outline of the electrode catalyst ink manufacture device of a 4th embodiment. It is a figure which shows typically the state which liquid entered into the hole formed in the catalyst particle in the catalyst containing material which made the powder of the catalyst particle contain the liquid. It is a figure which shows typically the hole which the space | gap was formed in the powdery catalyst particle. It is a graph which shows the relationship between the solid content ratio of the catalyst particle contained in a catalyst content, and a zeta potential difference.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the dimensional ratios in the drawings are exaggerated for convenience of explanation, and are different from the actual ratios.

<First embodiment>
As shown in FIG. 1, an electrode catalyst ink manufacturing apparatus 100 according to the first embodiment includes an ink tank 110 (mixing unit), an ink adjustment device 120 (electrode catalyst ink adjustment unit), and an ink adjustment device 130 (electrode catalyst ink). An adjustment unit) and a zeta potential measurement device 140 (a zeta potential measurement unit).

  The ink tank 110 contains the electrode catalyst ink 111. The electrode catalyst ink 111 includes a solvent, an ionomer, and catalyst particles. The electrode catalyst ink 111 may further include additives such as a water repellent, a dispersant, a thickener, and a pore former in addition to the above. The electrode catalyst ink 111 is stirred in the ink tank 110.

  Examples of the solvent include water such as tap water, pure water, ion-exchanged water, and distilled water, cyclohexanol, methanol, ethanol, n-propanol (n-propyl alcohol), isopropanol, n-butanol, sec-butanol, and isobutanol. And lower alcohols having 1 to 4 carbon atoms such as tert-butanol, propylene glycol, benzene, toluene, xylene and the like, but are not limited thereto. Besides these, butyl acetate, dimethyl ether, ethylene glycol and the like may be used as the solvent. These solvents may be used alone or in a mixture of two or more.

  Examples of the ionomer include, but are not limited to, a fluorine-based polymer electrolyte material and a hydrocarbon-based polymer electrolyte material. Examples of the fluorine-based polymer electrolyte material include perfluorocarbon sulfonic acid-based polymers such as Nafion (registered trademark), Aciplex (registered trademark), and Flemion (registered trademark), perfluorocarbon phosphonic acid-based polymers, and trifluorostyrene sulfonic acid. Polymer, an ethylene-tetrafluoroethylene-g-styrenesulfonic acid-based polymer, an ethylene-tetrafluoroethylene copolymer, a polyvinylidene fluoride-perfluorocarbonsulfonic acid-based polymer, and the like. Examples of the hydrocarbon-based polymer electrolyte materials include sulfonated polyethersulfone (S-PES), sulfonated polyaryletherketone, sulfonated polybenzimidazole alkyl, phosphonated polybenzimidazole alkyl, sulfonated polystyrene, and sulfonated polystyrene. Polyether ether ketone (SPEEK), sulfonated polyphenylene (S-PP) and the like are included.

  The catalyst particles include at least a substance having a catalytic action, and include, for example, a catalytic metal having a catalytic action and a catalyst carrier supporting the catalytic metal.

  The catalyst metal is, for example, a platinum-containing catalyst metal, but is not limited thereto. As the platinum-containing catalyst metal, for example, platinum (Pt) simple particles or platinum particles and ruthenium (Ru), iridium (Ir), rhodium (Rh), palladium (Pd), osmium (Os), tungsten (W) , Lead (Pb), iron (Fe), chromium (Cr), cobalt (Co), nickel (Ni), manganese (Mn), vanadium (V), molybdenum (Mo), gallium (Ga) and aluminum (Al) And a mixture with at least one other metal particle selected from the group consisting of: and an alloy of platinum and another metal.

  The catalyst carrier has, for example, electron conductivity and a main component is made of carbon. Examples of the catalyst carrier include, but are not limited to, carbon black (Ketjen black, oil furnace black, channel black, lamp black, thermal black, acetylene black, etc.), and carbon particles made of activated carbon.

  The ink adjusting device 120 includes an ionomer storage unit 121, an ionomer introduction pipe 122, and a valve 123 (opening / closing unit).

  The ionomer storage section 121 is a tank that stores the ionomer dispersion liquid 124. The ionomer dispersion liquid 124 includes a solvent and ionomer dispersed in the solvent.

  The ionomer introduction pipe 122 allows the ionomer storage 121 to communicate with the ink tank 110. The ionomer introduction pipe 122 forms a path for introducing the ionomer dispersion liquid 124 into the ink tank 110. A valve 123 is provided in this introduction path.

  The valve 123 is not particularly limited, but is, for example, an electromagnetic valve that opens and closes in response to an electric signal. By opening and closing the valve 123, the amount of the ionomer charged into the ink tank 110 is adjusted. When the valve 123 operates to open, the ionomer is supplied to the ink tank 110. When the valve 123 operates to close, the charging of the ionomer into the ink tank 110 stops.

  The ink adjusting device 130 includes a circulation pipe 131, a pump 132, and a disperser 133 (dispersion unit).

  The circulation pipe 131 communicates with the ink tank 110. The circulation pipe 131 forms a circulation path for re-introducing the electrode catalyst ink 111 derived from the ink tank 110 into the ink tank 110. The pump 132 and the disperser 133 are provided in this circulation path.

  The pump 132 promotes the flow of the electrode catalyst ink 111 in the circulation pipe 131, and circulates the electrode catalyst ink 111 smoothly.

  The disperser 133 applies mechanical energy to the electrode catalyst ink 111 derived from the ink tank 110, and promotes the dispersion of the ionomer and the catalyst particles in the electrode catalyst ink 111.

  The disperser 133 is, for example, a media stirring type disperser 133A as shown in FIG. 2, an ultrasonic homogenizer 133B as shown in FIG. 3, or a wet jet mill 133C as shown in FIG. 4, but is not limited thereto. .

  As shown in FIG. 2, the media stirring type dispersion machine 133A is provided between a circulation pipe 131A on the upstream side of the circulation path and a circulation pipe 131B on the downstream side of the circulation path. The media stirring type dispersion machine 133A introduces the electrode catalyst ink 111 into the vessel A1 through the circulation pipe 131A, and stirs the electrode catalyst ink 111 together with the spherical medium A2 by the rotating rotor A3. In this manner, mechanical energy is applied to the electrode catalyst ink 111, and the ionomer and the catalyst particles in the electrode catalyst ink 111 are dispersed. After passing through the media stirring type dispersion machine 133A, the electrode catalyst ink 111 is returned to the ink tank 110 through the circulation pipe 131B.

  As shown in FIG. 3, the ultrasonic homogenizer 133B is provided between the circulation pipe 131A on the upstream side of the circulation path and the circulation pipe 131B on the downstream side of the circulation path. The ultrasonic homogenizer 133B introduces the electrode catalyst ink 111 into the container B1 through the circulation pipe 131A. The ultrasonic homogenizer 133B applies ultrasonic waves from the chip B2 to the electrode catalyst ink 111 to vibrate the electrode catalyst ink 111. In this manner, mechanical energy is applied to the electrode catalyst ink 111, and the ionomer and the catalyst particles in the electrode catalyst ink 111 are dispersed. After passing through the ultrasonic homogenizer 133B, the electrode catalyst ink 111 is returned to the ink tank 110 through the circulation pipe 131B.

  As shown in FIG. 4, the wet jet mill 133C is provided between a circulation pipe 131A on the upstream side of the circulation path and a circulation pipe 131B on the downstream side of the circulation path. The wet jet mill 133C introduces the electrode catalyst ink 111 through the circulation pipe 131A, and causes collision between the electrode catalyst inks 111 by using pressurized injection by the plunger pump C1. In this manner, mechanical energy is applied to the electrode catalyst ink 111, and the ionomer and the catalyst particles in the electrode catalyst ink 111 are dispersed. After passing through the wet jet mill 133C, the electrode catalyst ink 111 is returned to the ink tank 110 through the circulation pipe 131B. Next, FIG. 1 is referred to again.

  As shown in FIG. 1, the zeta potential measuring device 140 communicates with the ink tank 110 through an electrode catalyst ink introduction pipe 141. The electrode catalyst ink introduction pipe 141 branches off from the circulation pipe 131. A part of the electrode catalyst ink 111 is introduced into the zeta potential measuring device 140 through the electrode catalyst ink introduction pipe 141.

  The zeta potential measuring device 140 determines the zeta potential from the introduced electrode catalyst ink 111 according to, for example, an electrophoretic light scattering measurement method (laser Doppler method). Since the electrophoretic light scattering measurement method (laser Doppler method) itself is conventionally known, a detailed description of the derivation of the zeta potential will be omitted here. In brief, the amount of frequency shift due to the Doppler effect of the laser light applied to the electrode catalyst ink 111, the electric field applied to the electrode catalyst ink 111, and the like are measured, and the migration speed and the electric mobility are calculated from these values. Further, the zeta potential is derived from the electric mobility based on the Smoluchowski equation.

  In order to perform such a measurement method, the zeta potential measuring device 140 includes, for example, an electrode that applies an electric field to the electrode catalyst ink 111, a laser device that irradiates the electrode catalyst ink 111 with a laser, and scattering from the electrode catalyst ink 111. Includes a detector that detects light. Further, the zeta potential measuring device 140 includes a computer, such as a computer, which performs calculations using actual measurement values and the like obtained from the electrode catalyst ink 111 and generates a control signal based on the calculation results.

  The configuration of the zeta potential measuring device 140 is not particularly limited. The zeta potential measurement device 140 is a measurement execution unit in which the measurement is performed including the laser device and the detector as described above, and a control unit that includes the calculator as described above and calculates the zeta potential and performs control based on the calculation result. However, they may have a configuration in which they are unitized and integrated, or may have a configuration in which they are separately provided separately.

  Next, a method for producing an electrode catalyst ink according to the first embodiment will be described.

  As shown in FIG. 5, the method for producing an electrode catalyst ink of the present embodiment includes an ink tank charging step S1, a zeta potential measuring step S2, a determining step S3, and an ink adjusting step S4.

  In the ink tank charging step S1, a solvent, ionomer, and catalyst particles are charged into the ink tank 110. The order of charging them is not particularly limited, and they may be charged separately or simultaneously. Further, in addition to the solvent, the ionomer, and the catalyst particles, additives such as a water repellent, a dispersant, a thickener, and a pore former may be added to the ink tank 110.

  In the present embodiment, the ionomer is introduced into the ink tank 110 by opening the valve 123 and introducing the ionomer dispersion liquid 124 through the ionomer introduction pipe 122, but is not limited to this. The worker may directly put the ionomer into the ink tank 110.

  In the ink tank charging step S1, the solvent, the ionomer, and the catalyst particles are stirred and mixed in the ink tank 110. By doing so, the electrode catalyst ink 111 is formed. The ionomer is adsorbed on the surfaces of the catalyst particles by mixing the solvent, the ionomer, and the catalyst particles.

  In the zeta potential measuring step S2 after the ink tank charging step S1, the zeta potential is measured for the electrode catalyst ink 111, and the zeta potential of the catalyst particles having the ionomer adsorbed on the surface is obtained. The zeta potential measuring device 140 measures the zeta potential. A part of the electrode catalyst ink 111 produced in the ink tank 110 is introduced into the zeta potential measuring device 140, and the zeta potential measuring device 140 performs the zeta potential measurement on the zeta potential measuring device 140, and the ionomer adsorbs the surface of the catalyst particles. The zeta potential of is derived.

  After the zeta potential measurement step S2, in the determination step S3, it is determined whether the amount of ionomer adsorbed on the catalyst particles is large or small using the measured zeta potential. The zeta potential measuring device 140 makes such a determination.

  Conventionally, the zeta potential was known as an index for evaluating the dispersibility and aggregability of colloid particles.However, the present inventors differed between the zeta potential and the amount of ionomer adsorbed on the catalyst particles. We newly focused on the correlation. Specifically, the relationship between the ionomer adsorption amount and the zeta potential will be described below, taking as an example the case where Nafion (registered trademark, hereinafter abbreviated), which is an example of ionomer, is adsorbed on catalyst particles.

  As shown in FIG. 6, the ionomer 10 made of Nafion is adsorbed around the catalyst particles 20. The catalyst particles 20 include catalyst carrier particles 21 and catalyst metal particles 22 supported on the catalyst carrier particles.

  The ionomer 10 made of Nafion has a hydrophobic group 11 and a hydrophilic group 12, and the zeta potential of the catalyst particles 20 becomes negative due to the hydrophilic group 12.

  Then, as shown in FIG. 7, as the adsorption amount of the ionomer 10 increases, the zeta potential of the catalyst particles 20 decreases (the absolute value increases).

  In fact, as shown in FIG. 8, the adsorption amount of the ionomer is a zeta potential difference ΔV (ΔV = −V) between the zeta potential (−V1) of the catalyst particles adsorbed by the ionomer and a predetermined zeta potential value (−V2). V2-(-V1)) increased. Here, the predetermined zeta potential value (-V2) is the zeta potential of the catalyst particles before ionomer adsorption. The magnitude of the adsorption amount of the ionomer was estimated from the magnitude of the electric resistance measured for the catalyst particles before and after the adsorption of the ionomer.

  Ionoma contributes to effective proton conduction for power generation. For this reason, when an electrode catalyst layer is formed from the electrode catalyst ink 111 and this is disposed on the electrolyte membrane to produce a membrane electrode assembly, the power generation performance of the membrane electrode assembly is large due to the large zeta potential difference ΔV described above. The larger the amount of ionomer adsorbed on the particles, the higher the amount.

  Based on this, in the determination step S3 of the present embodiment, if the zeta potential difference ΔV is equal to or greater than a preset reference value, the amount of ionomer adsorbed is large, and the amount necessary to exhibit desired proton conductivity is obtained. It is determined that the above ionomer is adsorbed on the catalyst particles.

  On the other hand, if the zeta potential difference ΔV is smaller than a preset reference value, it is determined that the amount of ionomer adsorbed is small, and that the ionomer in an amount necessary to exhibit the desired proton conductivity is not adsorbed on the catalyst particles. You.

  These determinations in the determination step S3 are performed by the zeta potential measurement device 140. The zeta potential measuring device 140 calculates the zeta potential difference ΔV, compares it with a previously stored reference value, and determines whether or not the zeta potential difference ΔV is equal to or greater than the reference value.

  If it is determined in the determination step S3 that the zeta potential difference ΔV is smaller than the predetermined value (the amount of adsorption of the ionomer is small), the electrode catalyst ink 111 is adjusted in the ink adjustment step S4.

  In the ink adjusting step S4, the electrode catalyst ink 111 is adjusted such that the zeta potential difference ΔV increases, that is, the amount of ionomer adsorbed increases. Such adjustment is performed by the ink adjustment device 120 and the ink adjustment device 130. When determining that the zeta potential difference ΔV is smaller than the predetermined value, the zeta potential measuring device 140 sends control signals 142 and 143 to the ink adjusting device 120 and the ink adjusting device 130 to operate them so as to increase the zeta potential difference ΔV. The zeta potential measuring step S2, the determining step S3, and the ink adjusting step S4 are repeated until the zeta potential difference ΔV becomes equal to or more than a predetermined value.

  Upon receiving the control signal 142 from the zeta potential measuring device 140, the ink adjusting device 120 opens the valve 123 and puts ionomer into the electrode catalyst ink 111 in the ink tank 110. As a result, the amount of ionomer contained in the electrode catalyst ink 111 and the amount of ionomer adsorbed on the catalyst particle surface increase, and as a result, the zeta potential difference ΔV increases.

  Upon receiving the control signal 143 from the zeta potential measuring device 140, the ink adjusting device 130 applies mechanical energy to the electrode catalyst ink 111 moving through the circulation path by the disperser 133. This promotes the dispersion of the ionomer and the catalyst particles contained in the electrode catalyst ink 111, and increases the frequency of contact thereof. As a result, the amount of ionomer adsorbed on the catalyst particle surface increases, and the zeta potential difference ΔV increases.

  When the dispersing device 133 is, for example, the media stirring type dispersing device 133A shown in FIG. 2, factors that increase the mechanical energy include, for example, the rotation speed of the rotor A3, the processing time, the specific gravity of the media A2, the filling rate of the media A2, And the internal pressure of the vessel A1.

  When the dispersing machine 133 is, for example, the ultrasonic homogenizer 133B shown in FIG. 3, factors that increase the mechanical energy include, for example, the output of ultrasonic waves and the time for applying ultrasonic waves.

  When the disperser 133 is, for example, a wet jet mill 133C shown in FIG. 4, factors that increase mechanical energy include, for example, a flow rate, a pressure, and a processing time.

  When it is determined that the zeta potential difference ΔV measured for the electrode catalyst ink 111 is equal to or larger than a predetermined value, the production of the electrode catalyst ink 111 ends. The produced electrode catalyst ink 111 may then be used immediately for producing a membrane electrode assembly, or may be stored.

  Next, the operation and effect of the present embodiment will be described.

  In the present embodiment, for the electrode catalyst ink 111, the amount of adsorption of the ionomer to the catalyst particles is determined using the measurement result of the zeta potential, and for those having a small amount of adsorption of the ionomer, the amount of adsorption of the ionomer, that is, Proton conductivity is improved.

  Therefore, the electrode catalyst ink 111 is provided to the next step of fabricating the membrane / electrode assembly in a state having good proton conductivity, and is prevented from being used with poor proton conductivity. Therefore, according to the present embodiment, the yield can be improved.

Unlike the present embodiment, it is conceivable to estimate the amount of ionomer adsorbed on the catalyst particles by measuring the counter ion concentration of the functional group of the ionomer. For example, in the case of Nafion shown in FIG. 6 described above, there is a possibility that the adsorption amount of ionomer can be estimated by measuring the concentration (pH) of hydrogen ions H ⁺ , which are counter ions of SO ₃ ⁻ in the functional group. .

  However, for example, carbonate ions derived from carbon dioxide gas in the air and anions derived from contamination that dissolve in the electrode catalyst ink 111 can also be counter ions of hydrogen ions, so that the amount of ionomer adsorbed can be accurately evaluated based on the hydrogen ion concentration. It is difficult to do.

  On the other hand, in the present embodiment, since the amount of adsorption of the ionomer is determined using the zeta potential, the amount of adsorption of the ionomer can be more accurately evaluated.

  In addition, since the measurement of the zeta potential itself is performed in the evaluation of the dispersibility of the colloid and the like, it is not necessary to design a new apparatus for measuring the zeta potential. Therefore, according to the present embodiment, the amount of ionomer adsorbed can be easily evaluated.

  In the present embodiment, when the electrode catalyst ink 111 is adjusted so as to increase the amount of ionomer adsorbed on the catalyst particles, the valve 123 is opened and the amount of ionomer charged into the electrode catalyst ink 111 is increased. As a result, the amount of ionomer contained in the electrode catalyst ink 111 increases. The ionomer containing a hydrophilic group has a property of retaining water, and protons move through the water. Therefore, if ionomer is added to the electrode catalyst ink 111 to increase the content of ionomer, proton conductivity can be more effectively increased.

  Further, if the amount of ionomer adsorbed is increased by applying mechanical energy as in the disperser 133 of the present embodiment, it is not necessary to increase the amount of ionomer charged into the electrode catalyst ink 111. For this reason, the amount of ionomer used is suppressed, and raw materials can be saved.

<Second embodiment>
As shown in FIG. 9, the electrode catalyst ink manufacturing apparatus 200 of the second embodiment includes a dispersion liquid adjustment device 210 (ionomer dispersion liquid adjustment unit) and a branch pipe 220 in addition to the configuration of the first embodiment. In addition, the electrode catalyst ink manufacturing apparatus 200 includes a catalyst particle storage unit 230, a catalyst particle introduction tube 250, a dispersion liquid adjustment device 260 (catalyst particle dispersion liquid adjustment unit), and a branch tube 270. In the drawings, the same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and redundant description is omitted.

  The dispersion liquid adjusting device 210 is provided on an introduction path of the ionomer dispersion liquid 124 toward the ink tank 110. The dispersion liquid adjusting device 210 is, for example, a media stirring type dispersion machine 133A, an ultrasonic homogenizer 133B, or a wet jet mill 133C as shown in FIGS. 2 to 4, but is not limited thereto.

  The branch pipe 220 branches off from the ionomer introduction pipe 122, and connects the ionomer introduction pipe 122 and the zeta potential measurement device 240.

  The catalyst particle storage section 230 is a tank that stores the catalyst particle dispersion 231. The catalyst particle dispersion liquid 231 includes a solvent and catalyst particles dispersed in the solvent.

  The catalyst particle introduction pipe 250 connects the catalyst particle storage section 230 with the ink tank 110 and forms an introduction path of the catalyst particle dispersion 231 toward the ink tank 110. A dispersion liquid adjusting device 260 is provided in this introduction path.

  The dispersion liquid adjusting device 260 is, for example, a media stirring type dispersion device 133A, an ultrasonic homogenizer 133B, or a wet jet mill 133C as shown in FIGS. 2 to 4, but is not limited thereto.

  The branch pipe 270 branches from the catalyst particle introduction pipe 250, and connects the catalyst particle introduction pipe 250 and the zeta potential measurement device 240.

  The zeta potential measuring device 240 measures the zeta potential of the ionomer dispersion 124 and the zeta potential of the catalyst particle dispersion 231 and controls the dispersion adjusting devices 210 and 260 based on the zeta potential. This is different from the zeta potential measuring device 140 of the first embodiment. Other configurations and operations of the zeta potential measuring device 240 are the same as those of the zeta potential measuring device 140 of the first embodiment.

  The zeta potential measuring device 240 measures the zeta potential of the ionomer dispersion liquid 124 and the zeta potential of the catalyst particle dispersion liquid 231 in the same manner as the zeta potential measurement of the electrode catalyst ink 111. The ionomer dispersion liquid 124 is introduced into the zeta potential measurement device 240 through the branch pipe 220. The catalyst particle dispersion 231 is introduced into the zeta potential measuring device 240 through the branch pipe 270.

  Next, a method for producing an electrode catalyst ink according to the second embodiment will be described.

  As shown in FIG. 10, the method for producing an electrode catalyst ink according to the second embodiment includes a zeta potential measuring step S10, a determining step S11, and a dispersion liquid adjusting step S12. These steps are performed before the ink tank charging step S1.

  Further, the method for preparing an electrode catalyst ink of the present embodiment includes a zeta potential measuring step S20, a determining step S21, and a dispersion liquid adjusting step S22. These steps are performed before the ink tank charging step S1. The ink tank charging step S1 and the subsequent steps S2 to S4 are the same as those in the first embodiment, and a duplicate description thereof will be omitted.

  In the zeta potential measuring step S10, the zeta potential of the ionomer dispersion liquid 124 is measured. The ionomer dispersion liquid 124 is introduced into the zeta potential measuring device 240 through the branch pipe 220, and the zeta potential is measured by the zeta potential measuring device 240.

  In the determination step S11, it is determined whether the zeta potential of the ionomer dispersion liquid 124 is a predetermined value. The zeta potential measuring device 240 compares the measured zeta potential of the ionomer dispersion 124 with a previously stored reference value, and determines whether the measured zeta potential is substantially equal to the reference value.

  When it is determined in the determination step S11 that the zeta potential is out of the range of the reference value, the ionomer dispersion 124 is adjusted in the dispersion adjustment step S12 such that the zeta potential is substantially equal to the reference value.

  The zeta potential measuring device 240 sends a control signal 241 to the dispersion liquid adjusting device 210 according to the determination result based on the measured zeta potential. In accordance with this, the dispersion adjusting device 210 adjusts the ionomer dispersion 124 so that the zeta potential becomes substantially equal to the reference value.

  The dispersion liquid adjusting device 210 adjusts the zeta potential by applying mechanical energy to the ionomer dispersion liquid 124 moving through the ionomer introduction pipe 122. For example, when the dispersion liquid adjusting device 210 is a media stirring type dispersion device 133A as shown in FIG. 2, the zeta potential is increased by increasing the rotation speed of the rotor A3 and promoting the dispersion of the ionomer contained in the ionomer dispersion liquid 124. adjust.

  Until the zeta potential of the ionomer dispersion 124 becomes substantially equal to the predetermined value, the zeta potential measurement step S10, the determination step S11, and the dispersion liquid adjustment step S12 are repeated. The ionomer dispersion liquid 124 is charged into the ink tank 110 in a state adjusted to a desired zeta potential.

  In the zeta potential measuring step S20, the zeta potential of the catalyst particle dispersion 231 is measured. The catalyst particle dispersion liquid 231 is introduced into the zeta potential measuring device 240 through the branch pipe 270, and the zeta potential is measured by the zeta potential measuring device 240.

  In the determination step S21, it is determined whether the zeta potential of the catalyst particle dispersion 231 is a predetermined value. The zeta potential measuring device 240 compares the measured zeta potential of the catalyst particle dispersion liquid 231 with a reference value stored in advance and determines whether the measured zeta potential is substantially equal to the reference value.

  When it is determined in the determination step S21 that the zeta potential is out of the range of the reference value, the catalyst particle dispersion 231 is adjusted in the dispersion adjustment step S22 such that the zeta potential becomes substantially equal to the reference value.

  The zeta potential measuring device 240 sends a control signal 242 to the dispersion adjusting device 260 according to the determination result based on the measured zeta potential. In accordance with this, the dispersion adjusting device 260 adjusts the catalyst particle dispersion 231 such that the zeta potential becomes substantially equal to the reference value.

  The dispersion adjusting device 260 adjusts the zeta potential by applying mechanical energy to the catalyst particle dispersion 231 moving through the catalyst particle introduction tube 250. For example, in the case where the dispersion liquid adjusting device 260 is a media stirring type dispersion machine 133A as shown in FIG. 2, the rotation speed of the rotor A3 is increased to promote the dispersion of the catalyst particles contained in the catalyst particle dispersion liquid 231 to thereby produce a zeta. Adjust the potential.

  Until the zeta potential of the catalyst particle dispersion liquid 231 becomes substantially equal to a predetermined value, the zeta potential measurement step S20, the determination step S21, and the dispersion liquid adjustment step S22 are repeated. The catalyst particle dispersion liquid 231 is charged into the ink tank 110 in a state adjusted to a desired zeta potential.

  Next, the operation and effect of the present embodiment will be described.

  In the present embodiment, in the dispersion liquid adjustment step S12, the zeta potential of the ionomer dispersion liquid 124 is adjusted by the dispersion liquid adjustment device 210 to be a predetermined value.

  Thus, one ionomer dispersion liquid 124 to be charged into the ink tank 110 when one electrode catalyst ink 111 is prepared, and separately charged into the ink tank 110 when another electrode catalyst ink 111 is prepared. The dispersion of the zeta potential with another ionomer dispersion liquid 124 is suppressed.

  In the present embodiment, in the dispersion adjusting step S22, the zeta potential of the catalyst particle dispersion 231 is adjusted by the dispersion adjusting device 260 so as to be a predetermined value.

  Thereby, one catalyst particle dispersion liquid 231 to be charged into the ink tank 110 when one electrode catalyst ink 111 is prepared, and another catalyst particle dispersion liquid 231 to be separately charged into the ink tank 110 when another electrode catalyst ink 111 is prepared. Zeta potential variation with other catalyst particle dispersion 231 is suppressed.

  As described above, since the variation in the zeta potential for each raw material of the electrode catalyst ink 111 is suppressed, the adjustment conditions when the electrode catalyst ink 111 is adjusted to have a desired ionomer adsorption amount and, consequently, proton conductivity, It is difficult to change for each raw material lot. Therefore, according to the present embodiment, it is possible to stably produce the electrode catalyst ink 111 having a desired ionomer adsorption amount and hence proton conductivity.

  In addition, the present embodiment has the same operation and effect as the first embodiment by the configuration common to the first embodiment.

<Third embodiment>
As shown in FIG. 11, the electrode catalyst ink manufacturing apparatus 300 of the third embodiment differs from the electrode catalyst ink manufacturing apparatus 100 of the first embodiment in having a first heater 301 and a second heater 302. About another structure, the electrode catalyst ink manufacturing apparatus 300 is substantially the same as the electrode catalyst ink manufacturing apparatus 100 of the first embodiment, The description of the operation is omitted.

  The first heater 301 is, for example, a jacket heater provided around the ionomer accommodating portion 121, but is not particularly limited as long as it can heat the ionomer. The first heater 301 is temperature-adjustable, and heats the ionomer contained therein by heating the ionomer dispersion liquid 124 to a desired temperature.

  The second heater 302 is, for example, a jacket heater provided around the ink tank 110, but is not particularly limited as long as it can heat the electrode catalyst ink 111. The second heater 302 is adjustable in temperature and heats the electrode catalyst ink 111 in the ink tank 110 to a desired temperature.

  Next, a method for producing an electrode catalyst ink of the present embodiment will be described.

  As shown in FIG. 12, the method for producing an electrode catalyst ink of the present embodiment is different from the method for producing an electrode catalyst ink of the first embodiment in having an ionomer heating step S30. Further, in the present embodiment, the ink tank charging step S1a is different from the ink tank charging step S1 of the first embodiment. The other steps, the order thereof, and the like are the same as those of the first embodiment in the method for producing an electrode catalyst ink according to the present embodiment, and thus redundant description will be omitted.

  In the ionomer heating step S30, the first heater 301 heats the ionomer.

  In the ink tank charging step S1a, the ionomer heated in the ionomer heating step S30 is charged into the ink tank 110. Further, in the ink tank charging step S1a, the charged ionomer is mixed by the second heater 302 while being heated together with other components such as a solvent and catalyst particles.

  The heating temperature in each of the ionomer heating step S30 and the ink tank charging step S1a is not particularly limited, but is preferably 50 ° C. or higher. The diameter of the ionomer particles is reduced by heating.

  As shown in FIG. 13, in the measurement results of the particle size distribution of the ionomer actually performed by the present inventors, the peak of the particle size (the top of the curve shown by the solid line in FIG. 13) is smaller as the heating temperature increases. And it was confirmed that the ionomer particles were reduced in diameter by heating. The graph of FIG. 13 shows the result of measuring the particle size distribution of the ionomer based on the dynamic light scattering method (DLS). The solid line indicates the frequency distribution, and the dotted line indicates the integrated distribution.

  By setting the heating temperature to, for example, 50 ° C. or higher, an ionomer having a preferable particle size can be obtained. Even if the type of ionomer is different, those particles decrease in size substantially similarly as the heating temperature increases.

  When the particle size of the ionomer becomes smaller, the ionomer is more likely to enter fine pores or concave portions formed in the catalyst particles, and thus the amount of the ionomer adsorbed on the catalyst particles is further increased.

  It is understood from the experimental results shown in FIG. 14 that the higher the heating temperature and the smaller the ionomer diameter is, the larger the zeta potential difference ΔV described in the first embodiment, ie, the larger the ionomer adsorption amount. It was confirmed that.

  In the present embodiment, the ionomer is not only heated before being mixed with the solvent, the catalyst particles, and the like, but also is heated by the second heater 302 during the mixing. For this reason, it is prevented that the particle size of the ionomer, which has been heated and reduced in diameter before mixing, is reduced to the original size due to the temperature drop due to the mixing with other components. Since the ionomer particles are maintained in a reduced diameter, the ionomer is easily adsorbed on the catalyst particles.

  This can be understood from the experimental results shown in FIG. In the case where the ionomer was heated both before and during mixing with the other components (indicated by ◎ in FIG. 15), when the ionomer was not heated in any of them (indicated by ○ and 中 in FIG. 15). ), The zeta potential difference ΔV was further increased, and it was confirmed that the ionomer adsorption amount was further increased.

  Here, the mark ○ indicates a case where the ionomer was heated in the same manner as the mark 混合 before mixing, but was returned to normal temperature during mixing. The mark ● indicates that the ionomer was not heated before being mixed, but was heated after being mixed with other components.

  Also, the particle size distribution of FIG. 13 shown above was measured in the same manner as in the case where the ionomer heated to 60 ° C. and the ionomer heated to 50 ° C. were cooled to 30 ° C. and 30 ° C. which was not heated originally. The results were obtained, and it was confirmed that the particle size of the ionomer returned to the original size.

  As described above, in the present embodiment, the first heater 301 is provided, and the ionomer is heated and reduced in diameter before being mixed with other components such as a solvent and catalyst particles. 302 are provided and they are mixed while being heated, so that the ionomer maintains a reduced diameter.

  For this reason, the ionomer is more likely to enter fine pores and concave portions formed in the catalyst particles. According to the present embodiment, in addition to the effect of the first embodiment, an effect that more ionomer can be adsorbed to the catalyst particles. Can be obtained.

<Fourth embodiment>
As shown in FIG. 16, the electrode catalyst ink manufacturing apparatus 400 according to the fourth embodiment differs from the electrode catalyst ink manufacturing apparatus 100 according to the first embodiment in having a box 401 that accommodates the ink tank 110. About another structure, the electrode catalyst ink manufacturing apparatus 400 is substantially the same as the electrode catalyst ink manufacturing apparatus 100 of 1st Embodiment, and attaches | subjects the same code | symbol as 1st Embodiment in a figure, and overlaps here. The description of the operation is omitted.

  The box 401 is, for example, a glove box that houses the ink tank 110, but is not particularly limited as long as it houses the ink tank 110 and can introduce an inert gas. For example, the box 401 may include a manipulator that can be operated from the outside, and the raw materials may be charged into the ink tank 110 by this. The inert gas introduced into the box 401 is, for example, nitrogen, but is not limited thereto.

  The method for producing the electrode catalyst ink of the present embodiment is substantially the same as the method for producing the electrode catalyst ink of the first embodiment shown in FIG. 5, except that in the ink tank charging step S1, the catalyst particles are in the form of a powder or solvent or ionomer. It is characterized in that it is mixed with

  In the present embodiment, the catalyst particles are prepared in the box 401 in a powder state, and are directly charged into the ink tank 110 in a powder state under an inert gas atmosphere, and mixed with a solvent or ionomer.

  Unlike the present embodiment, a paste- or liquid-state catalyst-containing substance obtained by adding a large amount of water to powder of catalyst particles may be charged into the ink tank 110 and mixed with a solvent, ionomer, or the like.

  In this case, as shown in FIG. 17, water 24 has entered the gaps 25 of the aggregate formed by the catalyst particles 20 and many of the fine holes 23 formed in the catalyst particles 20.

  On the other hand, as shown in FIG. 18, in the powdery catalyst particles 20, most of the gaps 25 and the holes 23 do not contain water, and the gaps are still open. Therefore, when the catalyst particles 20 are mixed with the ionomer, the ionomer easily enters the gaps 25 and the holes 23, and the amount of the ionomer adsorbed further increases.

  This can be understood from the experimental results shown in FIG. As shown by the two points on the left side of the graph shown in FIG. 19, compared to the catalyst containing a large amount of water when the solid content ratio of the catalyst particles is 50 wt% or less, the powdery catalyst particles having the solid content ratio of 100 wt% on the right side of the graph. It was confirmed that the zeta potential difference ΔV described in the first embodiment was increased, that is, the ionomer adsorption amount was increased. Here, the solid content ratio of the catalyst particles is obtained by dividing the weight of the catalyst particles contained in the catalyst-containing material by the weight of the catalyst-containing material (the sum of the weight of the catalyst particles and the weight of water).

  As described above, in the present embodiment, since the catalyst particles are prepared in the form of powder in the box 401 and are used as they are for mixing with the ionomer or the like, most of the fine holes or recesses formed in the catalyst particles are water. Etc. are not filled with the liquid and the gaps are still open.

  Therefore, when the catalyst particles and the ionomer are mixed, the ionomer easily enters the fine pores and recesses of the catalyst particles. According to this embodiment, in addition to the effects of the first embodiment, more ionomer is added to the catalyst particles. The effect of being able to be adsorbed is obtained.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the claims.

  For example, in the above embodiment, for the electrode catalyst ink 111, the amount of ionomer adsorbed on the catalyst particles is determined based on whether or not the zeta potential difference ΔV is equal to or greater than a predetermined value, but the present invention uses the zeta potential to determine the ionomer. What is necessary is just to determine the amount of adsorption, and it is not limited to the above embodiment.

  For example, if the negative zeta potential measured for the electrode catalyst ink is equal to or less than the reference value, or if the absolute value of the measured negative zeta potential is equal to or more than the reference value, the ionomer adsorption amount is large and the proton conductivity is good. May be determined.

  Further, in the above embodiment, the ink adjustment device 120 and the ink adjustment device 130 are provided as the electrode catalyst ink adjustment units, but the present invention includes a mode in which only one of these is provided.

  Further, the first heater and the second heater as in the third embodiment may be applied to other embodiments. By combining them with, for example, the fourth embodiment, the ionomer is reduced in size, and the catalyst particles are mixed with many pores left open, so that the amount of ionomer adsorbed on the catalyst particles can be reduced. Can be significantly increased.

  In addition, the catalyst particles of the fourth embodiment may contain some water as long as they are in a powder state, and the solid content ratio does not necessarily need to be 100%.

10 Ionoma,
11 hydrophobic groups,
12 hydrophilic groups,
20 catalyst particles,
21 catalyst support particles,
22 catalytic metal particles,
23 holes,
24 water,
25 gaps,
100 electrode catalyst ink producing apparatus,
110 ink tank (mixing unit)
111 electrode catalyst ink,
120 ink adjusting device (electrode catalyst ink adjusting unit),
121 Ionoma accommodation,
122 Ionoma introduction pipe,
123 valve (opening / closing part),
124 ionomer dispersion,
130 ink adjustment device (electrode catalyst ink adjustment unit),
131, 131A, 131B circulation pipe,
132 pumps,
133 dispersion machine (dispersion unit),
133A media stirring type dispersion machine,
133B ultrasonic homogenizer,
133C wet jet mill,
140 Zeta potential measuring device (Zeta potential measuring unit)
141 electrode catalyst ink introduction tube,
142, 143 control signals,
200 Electrode catalyst ink producing device,
210 dispersion liquid adjusting device (ionomer dispersion liquid adjusting unit),
220 branch pipe,
230 catalyst particle storage section,
231 catalyst particle dispersion,
240 zeta potential measuring device (zeta potential measuring unit),
241, 242 control signals,
250 catalyst particle introduction tube,
260 dispersion liquid adjustment device (catalyst particle dispersion liquid adjustment unit),
270 branch pipe,
300 electrode catalyst ink production equipment,
301 first heater,
302 second heater,
400 electrode catalyst ink producing apparatus,
401 box,
S1 ink tank charging process,
S1a Ink tank charging step,
S2 zeta potential measuring step,
S3 determination step,
S4 ink adjustment process,
S10 zeta potential measurement step,
S11 determination step,
S12 dispersion liquid adjusting step,
S20 zeta potential measurement step,
S21 determination step,
S22 dispersion liquid adjusting step,
S30 Ionomer heating step.

Claims (12)

At least a solvent, an ionomer, and an electrode catalyst ink manufacturing method of manufacturing an electrode catalyst ink by mixing catalyst particles,
When the ionomer measures the zeta potential of the catalyst particles adsorbed on the surface, the amount of adsorption of the ionomer to the catalyst particles is determined by using the zeta potential, and when the adsorption amount is determined to be small, A method for preparing an electrode catalyst ink, wherein the electrode catalyst ink is adjusted so that the adsorption amount of the ionomer increases.   The method for producing an electrode catalyst ink according to claim 1, wherein the adjustment of the electrode catalyst ink includes charging the ionomer to the electrode catalyst ink, and the charging increases the adsorption amount of the ionomer.   The adjustment of the electrode catalyst ink includes applying mechanical energy to the electrode catalyst ink, and increases the amount of adsorption of the ionomer by promoting the dispersion of the ionomer and the catalyst particles by applying the mechanical energy. The method for producing an electrode catalyst ink according to claim 1.   The said ionomer is heated before the said mixing, The said heated ionomer is mixed with heating at least with the said solvent and the said catalyst particle, The any one of Claims 1-3. 3. The method for producing an electrode catalyst ink according to item 1.   The method for producing an electrode catalyst ink according to any one of claims 1 to 4, wherein the catalyst particles are mixed with at least the solvent and the ionomer in a powder state. In order to produce one of the electrode catalyst inks, before mixing one ionomer dispersion containing the ionomer, and one catalyst particle dispersion containing the catalyst particles,
The other ionomer dispersion used for producing the other electrode catalyst ink, and the one ionomer dispersion, so that the dispersion of the zeta potential thereof is controlled, the one ionomer dispersion is adjusted. With
The other catalyst particle dispersion used for producing the other electrode catalyst ink, and the one catalyst particle dispersion, so that the dispersion of their zeta potential is suppressed, the one catalyst particle dispersion The method for producing an electrode catalyst ink according to any one of claims 1 to 4, wherein is adjusted. A mixing unit for preparing an electrode catalyst ink by mixing at least a solvent, an ionomer, and catalyst particles,
A zeta potential measurement unit that measures the zeta potential of the catalyst particles having the ionomer adsorbed on the surface thereof,
An electrode catalyst ink adjustment unit that performs adjustment such that the zeta potential changes with respect to the electrode catalyst ink,
The zeta potential measurement unit determines the amount of adsorption of the ionomer to the catalyst particles using the zeta potential, and if it is determined that the adsorption amount is small, the electrode catalyst ink adjustment unit, An electrocatalyst ink producing apparatus, wherein the electrocatalyst ink is adjusted so that the adsorption amount of ionomer increases.   The electrode catalyst ink adjustment unit includes an opening / closing unit provided on an introduction path of the ionomer to the mixing unit. The electrode catalyst ink adjustment unit opens the opening / closing unit and puts the ionomer into the mixing unit. The electrode catalyst ink producing apparatus according to claim 7, wherein the amount of adsorption of the ionomer is increased by doing.   The electrode catalyst ink adjustment unit including a dispersion unit provided in a circulation path for re-introducing the electrode catalyst ink derived from the mixing unit into the mixing unit, the electrode catalyst ink adjustment unit includes the dispersion unit The electrode catalyst ink producing apparatus according to claim 7 or 8, wherein a mechanical energy is applied to the electrode catalyst ink to promote dispersion of the ionomer and the catalyst particles, thereby increasing an adsorption amount of the ionomer. A first heater for heating the ionomer;
The electrode catalyst ink producing device according to any one of claims 7 to 9, further comprising: a second heater configured to heat the electrode catalyst ink in the mixing unit.   The catalyst according to any one of claims 7 to 10, further comprising a box accommodating the mixing unit and capable of introducing an inert gas, wherein the catalyst particles are in the box in a powder state. Electrode catalyst ink production equipment. One ionomer dispersion to be supplied to the mixing section, and between the other ionomer dispersion separately supplied to the mixing section separately from the dispersion, so that the dispersion of their zeta potential is suppressed. An ionomer dispersion adjusting unit for adjusting the ionomer dispersion,
The dispersion of the zeta potential between one catalyst particle dispersion supplied to the mixing section and another catalyst particle dispersion separately supplied to the mixing section separately from the dispersion is suppressed. The apparatus for producing an electrode catalyst ink according to any one of claims 7 to 10, further comprising: a catalyst particle dispersion liquid adjusting unit that adjusts the catalyst particle dispersion liquid.