JP2019121521A - Catalyst layer for fuel cell, electrolyte membrane-electrode assembly and fuel cell - Google Patents
Catalyst layer for fuel cell, electrolyte membrane-electrode assembly and fuel cell Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 113
- 239000000446 fuel Substances 0.000 title claims abstract description 28
- 239000003792 electrolyte Substances 0.000 title claims description 28
- 229920000554 ionomer Polymers 0.000 claims abstract description 114
- 239000002245 particle Substances 0.000 claims description 21
- 239000012528 membrane Substances 0.000 claims description 15
- 239000002184 metal Substances 0.000 claims description 13
- UQSQSQZYBQSBJZ-UHFFFAOYSA-N fluorosulfonic acid Chemical compound OS(F)(=O)=O UQSQSQZYBQSBJZ-UHFFFAOYSA-N 0.000 claims description 3
- 238000010248 power generation Methods 0.000 abstract description 10
- 239000011148 porous material Substances 0.000 abstract description 9
- 125000004432 carbon atom Chemical group C* 0.000 abstract description 5
- 239000007789 gas Substances 0.000 description 40
- 238000009792 diffusion process Methods 0.000 description 14
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 13
- 229910052799 carbon Inorganic materials 0.000 description 13
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 9
- 239000001301 oxygen Substances 0.000 description 9
- 229910052760 oxygen Inorganic materials 0.000 description 9
- 239000000126 substance Substances 0.000 description 8
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 6
- 239000001257 hydrogen Substances 0.000 description 6
- 229910052739 hydrogen Inorganic materials 0.000 description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 5
- 229920000557 Nafion® Polymers 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 229920001940 conductive polymer Polymers 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000002737 fuel gas Substances 0.000 description 5
- 230000001590 oxidative effect Effects 0.000 description 5
- 239000007787 solid Substances 0.000 description 5
- 238000003487 electrochemical reaction Methods 0.000 description 4
- 230000035699 permeability Effects 0.000 description 4
- 229920003937 Aquivion® Polymers 0.000 description 3
- 229920001774 Perfluoroether Polymers 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- -1 polytetrafluoroethylene Polymers 0.000 description 2
- 230000008961 swelling Effects 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 229910002849 PtRu Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000015271 coagulation Effects 0.000 description 1
- 238000005345 coagulation Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000002484 cyclic voltammetry Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- UJMWVICAENGCRF-UHFFFAOYSA-N oxygen difluoride Chemical compound FOF UJMWVICAENGCRF-UHFFFAOYSA-N 0.000 description 1
- 239000005518 polymer electrolyte Substances 0.000 description 1
- 229920005597 polymer membrane Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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- Inert Electrodes (AREA)
- Fuel Cell (AREA)
- Catalysts (AREA)
Abstract
Description
本発明は、プロトン伝導性を有する電解質膜の両面に電極として形成される触媒層と、この触媒層を電極として電解質膜両面に接合した電解質膜−電極接合体と、この電解質膜−電極接合体を用いた燃料電池に関する。 The present invention comprises a catalyst layer formed as an electrode on both sides of an electrolyte membrane having proton conductivity, an electrolyte membrane-electrode assembly in which the catalyst layer is joined to both sides of the electrolyte membrane using the electrode as an electrode, and this electrolyte membrane-electrode assembly The present invention relates to a fuel cell using the
燃料電池は、燃料と酸化剤、例えば、水素と酸素の電気化学反応によって発電する。この燃料電池では、プロトン伝導性を有する電解質膜（例えば、固体高分子膜）の両膜面に形成したアノードとカソードの両電極に、ガス拡散層を経て燃料ガスと酸化ガス、例えば水素ガスと空気を供給する。 Fuel cells produce electricity by the electrochemical reaction of a fuel and an oxidant, such as hydrogen and oxygen. In this fuel cell, both the anode and the cathode formed on both membrane surfaces of an electrolyte membrane (for example, a solid polymer membrane) having proton conductivity are passed through a gas diffusion layer and a fuel gas and an oxidizing gas such as hydrogen gas Supply air.
これら電極は、カーボン粒子等の導電性担体に金属触媒粒子を担持した触媒と水素イオン伝導性を有するアイオノマーとが混在して触媒層を形成している。 In these electrodes, a catalyst in which a catalyst in which metal catalyst particles are supported on a conductive support such as carbon particles and an ionomer having hydrogen ion conductivity are mixed to form a catalyst layer.
触媒層の形成方法としては、通常、触媒とアイオノマー分散液と溶媒とを混合してインクを調製する。インク中において、触媒は複数の粒子からなる凝集体を形成していて、インク中に分散しているアイオノマーは、触媒の凝集体に吸着する。一般的に、アイオノマーは触媒の凝集体の外表面に大半が吸着する。このインクを基材に塗布乾燥して触媒層を得る。 As a method of forming a catalyst layer, an ink is usually prepared by mixing a catalyst, an ionomer dispersion and a solvent. In the ink, the catalyst forms an aggregate of a plurality of particles, and the ionomer dispersed in the ink is adsorbed to the aggregate of the catalyst. In general, ionomers are mostly adsorbed on the outer surface of catalyst aggregates. The ink is applied to a substrate and dried to obtain a catalyst layer.
このように形成した電極において、触媒を介して電気化学反応を起こしている。 In the electrode thus formed, an electrochemical reaction is caused via a catalyst.
（化１）および（化２）の反応効率を高くするためには金属触媒粒子の有効利用率を高めることが重要である。 In order to increase the reaction efficiency of (Chemical Formula 1) and (Chemical Formula 2), it is important to increase the effective utilization of the metal catalyst particles.
例えば、特許文献１には、燃料電池用の電極触媒層であって、触媒金属を担持した導電性炭素粒子と水素イオン伝導性高分子とからなり、導電性炭素粒子が形成する凝集体内部の細孔に付着している水素イオン伝導性高分子の粒子径が５ｎｍ以上１００ｎｍ以下で平均分子量が１万から３０万である第１の水素イオン伝導性高分子と、導電性微粒子が形成する凝集体外部に付着する水素イオン伝導性高分子の粒子径が１００ｎｍ超１０００ｎｍ以下で平均分子量が３０万から３００万である第２の水素イオン伝導性高分子とからなる構成が開示されている。 For example, Patent Document 1 discloses an electrode catalyst layer for a fuel cell, which is formed of conductive carbon particles carrying a catalyst metal and a hydrogen ion conductive polymer, and in which aggregates are formed by the conductive carbon particles. The first hydrogen ion conductive polymer having a particle diameter of 5 nm or more and 100 nm or less and an average molecular weight of 10,000 to 300,000 adhered to the pores, and the coagulation formed by the conductive fine particles There is disclosed a configuration comprising a second hydrogen ion conductive polymer having a particle diameter of the hydrogen ion conductive polymer attached to the outside of the current collection body of not less than 100 nm and not more than 1000 nm and an average molecular weight of 300,000 to 3,000,000.
ここで、水素イオン伝導性高分子とは、前述した水素イオン伝導性を有するアイオノマーのことである。 Here, the hydrogen ion conductive polymer is an ionomer having the above-described hydrogen ion conductivity.
しかしながら、特許文献１で提案された構成では、第２のアイオノマーの分子鎖が長く結晶性が高いことから、酸素の透過性が低く、導電性微粒子が形成する凝集体内部への酸素の供給が滞りやすく、また、第１のアイオノマーは低分子量であることから結晶性が低く、発電時の水分で膨潤しやすく、凝集体内部の細孔を閉塞してしまい、酸素の供給や生成水の排出が滞りやすく、発電が不安定になるという課題を有していた。 However, in the configuration proposed in Patent Document 1, since the molecular chain of the second ionomer is long and the crystallinity is high, the permeability of oxygen is low and the supply of oxygen to the inside of the aggregate formed by the conductive fine particles is The first ionomer is low in crystallinity due to its low molecular weight, easily swelled by water during power generation, clogs pores inside the aggregate, and supplies oxygen and discharges generated water. The problem is that power generation is unstable.
本発明は、従来の課題を解決するもので、安定して高効率な発電が可能な燃料電池用触媒層を提供することを目的とする。 The present invention is intended to solve the conventional problems, and it is an object of the present invention to provide a fuel cell catalyst layer capable of stably and efficiently generating electricity.
前記従来の課題を解決するために、本発明は、導電性担体に金属触媒粒子を担持した触媒と、触媒の凝集体の微細孔の内壁の少なくとも一部を覆う第１のアイオノマーと、触媒の凝集体の外表面の少なくとも一部を覆う第２のアイオノマーと、で燃料電池用触媒層を構成するにあたって、第１のアイオノマーの側鎖の炭素の数を３以下とすると共に、第２のアイオノマーの側鎖の炭素の数を２以上としたのである。 In order to solve the above-mentioned conventional problems, the present invention provides a catalyst having a metal catalyst particle supported on a conductive support, a first ionomer which covers at least a part of the inner wall of the micropores of the catalyst aggregate, and a catalyst In forming a fuel cell catalyst layer with a second ionomer covering at least a part of the outer surface of the aggregate, the number of carbons in the side chain of the first ionomer is 3 or less, and the second ionomer is The number of carbons in the side chain of is 2 or more.
ここで、触媒の凝集体とは、触媒の一次粒子が形成するアグリゲートが、分子間力によって結合して形成されるアグロメレートのことである。また、微細孔とは、アグロメレートの内部に形成される空隙であり、さらにはアグリゲートのメソ孔も含まれる。また、微細孔の内壁とは、アグロメレートの内部の空隙に面する触媒の表面およびメソ孔の表面のことである。 Here, the aggregate of the catalyst refers to an agglomerate which is formed by combining the aggregates formed by the primary particles of the catalyst by intermolecular force. The fine pores are voids formed inside the agglomerate, and further include mesopores of the aggregate. Also, the inner wall of the micropores refers to the surface of the catalyst and the surface of the mesopores facing the internal voids of the agglomerate.
また、アイオノマー分散液は、水もしくはアルコール水溶液中に分散しており、一般的に側鎖の炭素の数が３以下のアイオノマーは分散粒子径が小さく、触媒の凝集体が形成する空隙の内部微細孔に一定の割合で侵入できる大きさである。 In addition, the ionomer dispersion is dispersed in water or an aqueous alcohol solution, and in general, the ionomer having a side chain carbon number of 3 or less has a small dispersed particle size, and the internal fineness of the voids formed by the aggregates of the catalyst is The size is such that the holes can penetrate at a constant rate.
一般的に、側鎖の炭素の数が３以下のパーフルオロスルフォン酸アイオノマーは、主鎖にポリテトラフルオロエチレンの骨格を持ち、末端にスルフォン酸を持つフルオロエーテル基をもたないペンダント側鎖からなる。このようなアイオノマーを短側鎖アイオノマーという。短側鎖アイオノマーは、剛直な側鎖を持ち側鎖長が短いことから主鎖骨格が密に並びやすく、結晶性を示しやすい傾向にある。 Generally, perfluorosulfonic acid ionomers having 3 or less carbon atoms in the side chain have a backbone of polytetrafluoroethylene in the main chain and a pendant side chain having no fluoroether group having a sulfonic acid at the end. Become. Such ionomers are referred to as short side chain ionomers. The short side chain ionomers have rigid side chains and have a short side chain length, so the main chain skeleton tends to be densely arranged and tends to exhibit crystallinity.
以上のことから、第１のアイオノマーは、導電性担体に金属触媒粒子を担持した触媒の凝集体が形成する空隙の内部微細孔に一定割合で侵入でき、触媒の凝集体の微細孔の内壁の一部を被覆することで、電気化学反応に寄与する金属触媒粒子を増やすことができる。 From the above, the first ionomer can penetrate at a constant rate into the internal micropores of the void formed by the aggregate of the catalyst having the metal catalyst particles supported on the conductive support, and the inner wall of the micropore of the aggregate of the catalyst By partially coating, metal catalyst particles contributing to the electrochemical reaction can be increased.
さらに、第１のアイオノマーは、結晶性が高いので、特許文献１に記載の第１のアイオノマーのように、発電時の生成水で過剰に膨潤して凝集体内部の細孔を閉塞することが無い。 Furthermore, since the first ionomer has high crystallinity, it can swell excessively with generated water at the time of power generation to clog the pores inside the aggregate, like the first ionomer described in Patent Document 1. There is not.
また、第２のアイオノマーの主鎖は、特許文献１に記載の第２のアイオノマーの分子鎖ほど長くないため、結晶性は相対的に低い。そのため、酸素の透過性は確保され、触媒の凝集体の内部へ滞りなく酸素を供給できる。 Moreover, since the main chain of the second ionomer is not as long as the molecular chain of the second ionomer described in Patent Document 1, the crystallinity is relatively low. Therefore, the permeability of oxygen can be secured, and oxygen can be supplied to the inside of the catalyst aggregate without a break.
これによって、本発明の燃料電池用触媒層は、ガス拡散性の低下を抑制し、金属触媒粒子の有効利用率を高めることができる。 Thus, the fuel cell catalyst layer of the present invention can suppress the decrease in gas diffusivity and can increase the effective utilization of metal catalyst particles.
本発明の燃料電池用触媒層および電解質膜−電極接合体および燃料電池は、ガス拡散性に優れ、金属触媒粒子の有効利用率が高く、安定して高効率な運転ができる燃料電池用触媒層を提供できる。また、これを用いて作製した燃料電池は、良好な電池特性を得ることができる。さらに、高性能な発電デバイスや発電システムを提供できる。 The fuel cell catalyst layer, the electrolyte membrane-electrode assembly, and the fuel cell of the present invention are excellent in gas diffusivity, have a high effective utilization of metal catalyst particles, and can stably and efficiently operate. Can provide Moreover, the fuel cell produced using this can acquire a favorable cell characteristic. Furthermore, high-performance power generation devices and power generation systems can be provided.
第１の発明は、導電性担体に金属触媒粒子を担持した触媒と、触媒の凝集体の微細孔の内壁の少なくとも一部を覆う第１のアイオノマーと、触媒の凝集体の外表面の少なくとも一部を覆う第２のアイオノマーと、を備え、第１のアイオノマーは側鎖の炭素の数が３以下であり、第２のアイオノマーは側鎖の炭素の数が２以上であることを特徴とした燃料電池用触媒層である。 According to a first aspect of the present invention, there is provided a catalyst having a metal catalyst particle supported on a conductive support, a first ionomer covering at least a part of the inner wall of the micropores of the catalyst aggregate, and at least one of the outer surfaces of the catalyst aggregate. And the second ionomer is characterized in that the number of carbon in the side chain is 3 or less, and the number of carbon in the side chain is 2 or more. It is a catalyst layer for fuel cells.
これによって、生成水等による第１のアイオノマーの過剰な膨潤が抑制され、触媒の凝集体の内部の細孔を閉塞することが無い。また、第２のアイオノマーは酸素を触媒の凝集体内部に滞りなく供給できる。以上により、ガス拡散性に優れ、金属触媒粒子の有効利用率が高い触媒層を実現することができる。 As a result, excessive swelling of the first ionomer due to generated water or the like is suppressed, and the pores in the aggregates of the catalyst are not clogged. Also, the second ionomer can continuously supply oxygen inside the catalyst aggregate. By the above, it is possible to realize a catalyst layer which is excellent in gas diffusibility and has a high effective utilization of metal catalyst particles.
第２の発明は、特に、第１の発明における、第１のアイオノマーおよび第２のアイオノマーをパーフルオロスルフォン酸からなるアイオノマーとしたものである。これにより、化学的耐久性が高く、長期間安定して高い発電効率を得ることができる。 In the second invention, in particular, the first ionomer and the second ionomer in the first invention are ionomers composed of perfluorosulfonic acid. As a result, chemical durability is high, and high power generation efficiency can be obtained stably for a long time.
第３の発明は、特に第１の発明または第２の発明における触媒層を、プロトン伝導性を有する電解質膜の両面に配置される触媒層の少なくとも一方の主面に配置した電解質膜−電極接合体である。これにより、ガス拡散性に優れ、金属触媒粒子の有効利用率が高い触媒層を有する電解質膜−電極接合体を実現できる。 According to a third invention, in particular, an electrolyte membrane-electrode junction in which the catalyst layer in the first invention or the second invention is disposed on at least one main surface of the catalyst layer disposed on both sides of the electrolyte membrane having proton conductivity. It is a body. Thereby, it is possible to realize an electrolyte membrane-electrode assembly having a catalyst layer which is excellent in gas diffusibility and has a high effective utilization of metal catalyst particles.
第４の発明は、特に第３の発明の電解質膜−電極接合体を備える燃料電池である。これにより、安定して高効率な運転ができる。 A fourth invention is, in particular, a fuel cell provided with the membrane-electrode assembly of the third invention. Thereby, stable and highly efficient operation can be performed.
以下、本発明の実施の形態について、図面を参照しながら説明する。なお、この実施の形態によって本発明が限定されるものではない。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited by the embodiment.
（実施の形態１）
図１は、本発明の実施の形態１におけるカソード触媒層の拡大模式図である。図２は、本発明の実施の形態１における燃料電池単セルの断面模式図である。
Embodiment 1
FIG. 1 is an enlarged schematic view of a cathode catalyst layer in Embodiment 1 of the present invention. FIG. 2 is a schematic cross-sectional view of a single fuel cell according to Embodiment 1 of the present invention.
図１に示すように、本実施の形態のカソード触媒層１０は、導電性担体１１にＰｔ触媒１２を担持した触媒１３と、触媒１３の凝集体からなる触媒凝集体１４と、触媒凝集体１
４が形成する内部微細孔１５の内壁の少なくとも一部を被覆する第１のアイオノマー１６と、触媒凝集体１４の外表面の少なくとも一部を被覆する第２のアイオノマー１７とからなる。
As shown in FIG. 1, in the cathode catalyst layer 10 of the present embodiment, a catalyst 13 having a Pt catalyst 12 supported on a conductive support 11, a catalyst aggregate 14 composed of an aggregate of the catalyst 13, and a catalyst aggregate 1
The first ionomer 16 covers at least a part of the inner wall of the internal micropores 15 formed by 4 and the second ionomer 17 covers at least a part of the outer surface of the catalyst aggregate 14.
ここで、第１のアイオノマー１６には、（化３）に示す構造式を有するＳｏｌｖａｙ社製のＡｑｕｉｖｉｏｎ（登録商標）を用いた。 Here, for the first ionomer 16, Aquivion (registered trademark) manufactured by Solvay having a structural formula shown in (Chemical Formula 3) was used.
次に、第２のアイオノマー１７には、（化４）に示す構造式を有するＣｈｅｍｏｕｒｓ社製のＮａｆｉｏｎ（登録商標）を用いた。 Next, as the second ionomer 17, Nafion (registered trademark) manufactured by Chemours, which has a structural formula shown in (Chem. 4), was used.
（化４）に示す通り、Ｎａｆｉｏｎ（登録商標）の側鎖は枝分かれしており、側鎖全体の炭素の数は５であり、側鎖の主となる骨格の炭素の数は４である。このように、側鎖の炭素の数が４以上のアイオノマーを、長側鎖アイオノマーという。 As shown in (Formula 4), the side chain of Nafion (registered trademark) is branched, the number of carbons in the entire side chain is 5, and the number of carbon atoms in the main backbone of the side chain is 4. Thus, an ionomer having 4 or more carbon atoms in its side chain is referred to as a long side chain ionomer.
図２に示すように、本実施の形態の燃料電池単セル２０は、電解質膜２１の両面に形成されるカソード触媒層１０とアノード触媒層２２とを備える電解質膜−電極接合体２３を両側から挟持するアノードガス拡散層２４およびカソードガス拡散層２５と、アノードガス拡散層２４およびカソードガス拡散層２５のさらに外側に配設されたアノードガスセパレータ２６およびカソードガスセパレータ２７とを備えている。 As shown in FIG. 2, the fuel cell single cell 20 of the present embodiment has an electrolyte membrane-electrode assembly 23 provided with a cathode catalyst layer 10 and an anode catalyst layer 22 formed on both sides of the electrolyte membrane 21 from both sides. An anode gas diffusion layer 24 and a cathode gas diffusion layer 25 to be held, and an anode gas separator 26 and a cathode gas separator 27 disposed outside the anode gas diffusion layer 24 and the cathode gas diffusion layer 25 are provided.
アノードガス拡散層２４およびカソードガス拡散層２５は、ガス透過性を有する導電性部材であるカーボンペーパーによって形成されている。このようなアノードガス拡散層２４およびカソードガス拡散層２５は、電気化学反応に供されるガスをアノード触媒層２２およびカソード触媒層１０に導くと共に、集電を行う。 The anode gas diffusion layer 24 and the cathode gas diffusion layer 25 are formed of carbon paper which is a conductive member having gas permeability. The anode gas diffusion layer 24 and the cathode gas diffusion layer 25 as described above conduct current collection while guiding the gas to be subjected to the electrochemical reaction to the anode catalyst layer 22 and the cathode catalyst layer 10.
アノードガスセパレータ２６およびカソードガスセパレータ２７は、ガス透過性のない導電性部材である圧縮カーボンによって形成される。アノードガスセパレータ２６および
カソードガスセパレータ２７は、それぞれ所定の凹凸形状を有している。
The anode gas separator 26 and the cathode gas separator 27 are formed of compressed carbon which is a conductive member having no gas permeability. The anode gas separator 26 and the cathode gas separator 27 each have a predetermined uneven shape.
この凹凸形状によって、アノードガスセパレータ２６とアノードガス拡散層２４との間には、水素を含有する燃料ガスが流れる燃料ガス流路２８が形成される。また、上記凹凸形状によって、カソードガスセパレータ２７とカソードガス拡散層２５との間には、酸素を含有する酸化ガスが流れる酸化ガス流路２９が形成される。本実施の形態では、燃料ガスには水素を、酸化ガスには空気を用いる。 Due to this uneven shape, a fuel gas flow path 28 in which a fuel gas containing hydrogen flows is formed between the anode gas separator 26 and the anode gas diffusion layer 24. Further, due to the uneven shape, an oxidizing gas flow passage 29 through which an oxidizing gas containing oxygen flows is formed between the cathode gas separator 27 and the cathode gas diffusion layer 25. In the present embodiment, hydrogen is used as the fuel gas, and air is used as the oxidizing gas.
以上のように構成された本実施の形態のカソード触媒層１０、およびカソード触媒層１０を備える電解質膜−電極接合体２３および燃料電池単セル２０について、以下その作用について説明する。 The functions of the cathode catalyst layer 10 of the present embodiment configured as described above and the electrolyte membrane-electrode assembly 23 including the cathode catalyst layer 10 and the fuel cell single cell 20 will be described below.
まず、第１のアイオノマー１６は、発電時の生成水等による過剰な膨潤を防止する。また、第２のアイオノマー１７は、内部微細孔１５へ酸素ガスを滞りなく供給する。それによって、カソード触媒層１０のＰｔ触媒１２の有効利用率が高くなる。 First, the first ionomer 16 prevents excessive swelling due to water or the like generated during power generation. In addition, the second ionomer 17 supplies oxygen gas to the internal fine pores 15 without any trouble. Thereby, the effective utilization of the Pt catalyst 12 of the cathode catalyst layer 10 is increased.
以上のように、本実施の形態においては、カソード触媒層１０の構成を、導電性担体１１にＰｔ触媒１２を担持した触媒１３と、触媒１３の凝集体からなる触媒凝集体１４が形成する内部微細孔１５の内壁の少なくとも一部を被覆する第１のアイオノマー１６と、触媒凝集体１４の外表面の少なくとも一部を被覆する第２のアイオノマー１７とからなり、第１のアイオノマー１６は側鎖の炭素の数が２であり、第２のアイオノマー１７は側鎖の炭素の数を５とすることにより、内部微細孔１５に存在するＰｔ触媒１２を有効に使え、高い発電効率が得られるカソード触媒層１０とすることができる。 As described above, in the present embodiment, the configuration of the cathode catalyst layer 10 is formed by the catalyst 13 having the Pt catalyst 12 supported on the conductive support 11 and the catalyst aggregate 14 formed of the aggregates of the catalyst 13. A first ionomer 16 covering at least a part of the inner wall of the micropores 15 and a second ionomer 17 covering at least a part of the outer surface of the catalyst aggregate 14, the first ionomer 16 having a side chain The second ionomer 17 has a carbon number of 2 and a side chain carbon number of 5 to effectively use the Pt catalyst 12 present in the internal micropores 15 and provide a cathode with high power generation efficiency. The catalyst layer 10 can be used.
このようなカソード触媒層１０を備える電解質膜−電極接合体２３は、ガス拡散性に優れ、Ｐｔ触媒１２の有効利用率が高くなり、これを用いた燃料電池単セル２０は安定して高効率な発電ができる。 The electrolyte membrane-electrode assembly 23 provided with such a cathode catalyst layer 10 is excellent in gas diffusivity, the effective utilization rate of the Pt catalyst 12 is high, and the fuel cell single cell 20 using this is stably high efficiency. Power generation.
なお、本実施の形態の第１のアイオノマー１６および第２のアイオノマー１７の側鎖の炭素の数を３としても、第１のアイオノマー１６の分散粒子径が内部微細孔１５に一定程度侵入できる大きさであればよく、本実施例と同様の効果を得ることができる。 Even if the number of carbons in the side chains of the first ionomer 16 and the second ionomer 17 of this embodiment is 3, the dispersed particle diameter of the first ionomer 16 can penetrate to the internal fine pores 15 to a certain extent. The same effect as the present embodiment can be obtained.
また、本実施の形態の第１のアイオノマー１６の側鎖の炭素の数が３で、第２のアイオノマーの側鎖の炭素の数が２でも、第１のアイオノマー１６の内部微細孔１５に一定程度侵入できる大きさの分散粒子が、内部微細孔１５の内壁の少なくとも一部を第１のアイオノマー１６が被覆するので、本実施の形態と同様の効果を得ることができる。 Further, even if the number of carbons in the side chain of the first ionomer 16 of the present embodiment is 3 and the number of carbons in the side chain of the second ionomer is 2, the internal micropores 15 of the first ionomer 16 are constant. The first ionomer 16 covers at least a part of the inner wall of the internal micropores 15 with the dispersed particles having such a size that can penetrate to a certain degree, so that the same effect as that of the present embodiment can be obtained.
なお、本実施の形態の第１のアイオノマー１６は、内部微細孔１５の内壁の少なくとも一部を被覆していればよく、第１のアイオノマー１６が、触媒凝集体１４の外表面の少なくとも一部を被覆していてもよい。 The first ionomer 16 according to the present embodiment may cover at least a part of the inner wall of the inner micropores 15, and the first ionomer 16 may be at least a part of the outer surface of the catalyst aggregate 14. May be coated.
また、本実施の形態の第２のアイオノマー１７は、触媒凝集体１４の外表面の少なくとも一部を被覆していればよく、第２のアイオノマー１７が、内部微細孔１５の内壁の一部を被覆していてもよい。 Further, the second ionomer 17 according to the present embodiment may cover at least a part of the outer surface of the catalyst aggregate 14, and the second ionomer 17 may be a part of the inner wall of the inner micropores 15. It may be coated.
以下、本実施の形態を実施例を用いて詳細に説明する。なお、この実施例によって本発明が限定されるものではない。 Hereinafter, the present embodiment will be described in detail using examples. The present invention is not limited by this embodiment.
（実施例１）
カソード触媒として、Ｐｔ触媒がカーボン担体に５０ｗｔ％担持されたＴＥＣ１０Ｅ５０Ｅ（田中貴金属工業株式会社製）を、第１のアイオノマーとしてＡｑｕｉｖｉｏｎ Ｄ８３−２４Ｂ（Ｓｉｇｍａ−Ａｌｄｒｉｃｈ社製）（短側鎖アイオノマー）を、第２のアイオノマーとして、Ｎａｆｉｏｎ ＤＥ１０２１（和光純薬工業株式会社製）（長側鎖アイオノマー）をそれぞれ用意した。
Example 1
As a cathode catalyst, TEC 10 E 50 E (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) in which 50 wt% of Pt catalyst is supported on a carbon carrier is used as a cathode catalyst, and Aquivion D 83-24 B (manufactured by Sigma-Aldrich) (short side chain ionomer) as a first ionomer. Nafion DE1021 (manufactured by Wako Pure Chemical Industries, Ltd.) (long side chain ionomer) was prepared as a second ionomer.
これらをエタノール水溶液に混合し、カソードインクを得た。このとき、アイオノマーの総和（短側鎖アイオノマーと長側鎖アイオノマーの和）に対する短側鎖アイオノマーの固形分重量比が０．２５となるようにした。また、アイオノマーの総和と触媒のカーボン担体の重量比が０．８となるようにした。 These were mixed with an aqueous ethanol solution to obtain a cathode ink. At this time, the solid content weight ratio of the short side chain ionomer to the total of the ionomers (the sum of the short side chain ionomer and the long side chain ionomer) was set to 0.25. Also, the weight ratio of the total amount of ionomer to the carbon carrier of the catalyst was 0.8.
次に、アノード触媒としてＴＥＣ６１Ｅ５４（田中貴金属工業株式会社製）を、アイオノマーとして、Ｎａｆｉｏｎ ＤＥ１０２１（和光純薬工業株式会社製）を用意した。これらをエタノール水溶液に混合し、アノードインクを得た。ここで、アイオノマーと触媒のカーボン担体の重量比が０．８となるようにした。 Next, TEC 61 E 54 (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) was prepared as an anode catalyst, and Nafion DE 1021 (manufactured by Wako Pure Chemical Industries, Ltd.) was prepared as an ionomer. These were mixed with an aqueous ethanol solution to obtain an anode ink. Here, the weight ratio of ionomer to catalyst carbon carrier was made to be 0.8.
次に、電解質膜として日本ゴア株式会社製のＧＯＲＥ−ＳＥＬＥＣＴ（登録商標）を用意し、カソードインクを電解質膜に塗布した。このとき、Ｐｔの担持量を０．２ｍｇ／ｃｍ２となるようにした。 Next, GORE-SELECT (registered trademark) manufactured by Nippon Gore Co., Ltd. was prepared as an electrolyte membrane, and a cathode ink was applied to the electrolyte membrane. At this time, the loading amount of Pt was adjusted to 0.2 mg / cm 2 .
次に、電解質膜を裏返して、アノードインクを塗布した。このとき、ＰｔＲｕの担持量を０．２ｍｇ／ｃｍ２となるようにし、電解質膜−電極接合体を作製した。 Next, the electrolyte membrane was turned over and an anode ink was applied. At this time, the supported amount of PtRu was 0.2 mg / cm 2 to prepare an electrolyte membrane-electrode assembly.
次に、マイクロポーラスレイヤー（ＭＰＬ）を備えたガス拡散層を用意し、作製した電解質膜−電極接合体と共に単セルに組み込み、単セル評価装置にセットした。そして、アノードには水素、カソードには空気を供給し、セル温度は６５℃に設定した。 Next, a gas diffusion layer provided with a microporous layer (MPL) was prepared, incorporated into a single cell together with the produced electrolyte membrane-electrode assembly, and set in a single cell evaluation apparatus. Then, hydrogen was supplied to the anode, air was supplied to the cathode, and the cell temperature was set to 65 ° C.
アノードガスおよびカソードガスは、それぞれ加湿器を経由して単セルに供給され、アノード及びカソードの加湿温度は共に４０℃（３０％ＲＨ）とした。単セルは電子負荷装置に接続し、０．３Ａ／ｃｍ２で運転した。 The anode gas and the cathode gas were respectively supplied to the single cell via a humidifier, and the humidification temperatures of the anode and the cathode were both 40 ° C. (30% RH). The single cell was connected to an electronic load and operated at 0.3 A / cm 2 .
また、アノードには水素を供給し、カソードには窒素を供給し、ポテンショスタットを用い、電気化学比表面積（ＥＣＳＡ）を測定した。ＥＣＳＡは従来公知のサイクリックボルタンメトリーによって求めた。 Further, hydrogen was supplied to the anode, nitrogen was supplied to the cathode, and an electrochemical specific surface area (ECSA) was measured using a potentiostat. ECSA was determined by conventionally known cyclic voltammetry.
（実施例２）
触媒および第１のアイオノマー、第２のアイオノマーは、実施例１と同じであり、短側鎖アイオノマーと長側鎖アイオノマーの和に対する短側鎖アイオノマーの固形分重量比が０．５となるようにした以外は、実施例１と同様である。
(Example 2)
The catalyst and the first and second ionomers are the same as in Example 1 so that the weight ratio of the short side chain ionomer to the sum of the short side chain ionomer and the long side chain ionomer is 0.5. The second embodiment is the same as the first embodiment except for the above.
（実施例３）
触媒および第１のアイオノマー、第２のアイオノマーは、実施例１と同じであり、短側鎖アイオノマーと長側鎖アイオノマーの和に対する短側鎖アイオノマーの固形分重量比が０．７５となるようにした以外は、実施例１と同様である。
(Example 3)
The catalyst and the first and second ionomers are the same as in Example 1 so that the weight ratio of the short side chain ionomer to the sum of the short side chain ionomer and the long side chain ionomer is 0.75. The second embodiment is the same as the first embodiment except for the above.
（実施例４）
触媒および第１のアイオノマーは、実施例１と同じであり、第２のアイオノマーは第１のアイオノマーと同一とした。つまり、実質的に、短側鎖アイオノマーと長側鎖アイオノマーの和に対する短側鎖アイオノマーの固形分重量比が１となるようにした以外は、実施例１と同様である。
(Example 4)
The catalyst and the first ionomer were the same as in Example 1, and the second ionomer was the same as the first ionomer. That is, it is substantially the same as Example 1 except that the solid content weight ratio of the short side chain ionomer to the sum of the short side chain ionomer and the long side chain ionomer is set to 1.
（比較例）
触媒および第２のアイオノマーは、実施例１と同じであり、第１のアイオノマーは第２のアイオノマーと同一とした。つまり、実質的に、短側鎖アイオノマーと長側鎖アイオノマーの和に対する短側鎖アイオノマーの固形分重量比が０となるようにした以外は、実施例１と同様である。
(Comparative example)
The catalyst and the second ionomer were the same as in Example 1, and the first ionomer was the same as the second ionomer. That is, it is substantially the same as Example 1 except that the solid content weight ratio of the short side chain ionomer to the sum of the short side chain ionomer and the long side chain ionomer was 0.
実施例１から実施例４および比較例の短側鎖アイオノマーの比率および第１のアイオノマー（担体内部）と第２のアイオノマー（担体表面）の側鎖の炭素の数を（表１）に示した。 The proportions of the short side chain ionomers of Examples 1 to 4 and Comparative Example and the number of carbons in the side chains of the first ionomer (within the carrier) and the second ionomer (the surface of the carrier) are shown in Table 1 .
図３に０．３Ａ／ｃｍ２で発電した時の電圧と短側鎖アイオノマー比の関係を示す特性図を示した。このとき、電圧は短側鎖アイオノマー比が０である比較例の値を１とした相対値で示した。
FIG. 3 shows a characteristic diagram showing the relationship between the voltage and the short side chain ionomer ratio when power is generated at 0.3 A / cm 2 . At this time, the voltage is shown as a relative value with the value of the comparative example in which the short side chain ionomer ratio is 0 as 1.
図３より、短側鎖アイオノマー比が０の比較例以外の全ての実施例において、電圧が向上した。 From FIG. 3, the voltage was improved in all the examples except the comparative example where the short side chain ionomer ratio was 0.
、図４にＥＣＳＡと短側鎖アイオノマー比の関係を示す特性図を示した。このとき、ＥＣＳＡは短側鎖アイオノマー比が０である比較例の値を１とした相対値で示した。 FIG. 4 shows a characteristic chart showing the relationship between ECSA and short side chain ionomer ratio. At this time, ECSA was shown as a relative value with the value of the comparative example having a short side chain ionomer ratio of 0 as 1.
図４より短側鎖アイオノマーを混合した実施例全てでＥＣＳＡが１以上となり、ＥＣＳＡの向上を確認できた。 From all the examples which mixed short side chain ionomer from FIG. 4, ECSA became 1 or more, and the improvement of ECSA was able to be confirmed.
以上より、短側鎖アイオノマー比を０．２５から１とすることにより、ＥＣＳＡが向上し、電圧が高く高効率な運転ができることを確認した。 From the above, it was confirmed that by setting the short side chain ionomer ratio to 0.25 to 1, ECSA is improved and high voltage and high efficiency operation can be performed.
なお、本実施例においては短側鎖アイオノマー比を０．２５以上としたが、図３の結果より電圧が短側鎖アイオノマー比に対して直線的に増加しているので、短側鎖アイオノマー比が０．２以上でも十分高い効果が得られる。さらには短側鎖アイオノマー比が０．１以上でも高い効果を得ることができる。さらには短側鎖アイオノマー比が０．０５以上でも十分効果を得ることができる。 In the present example, the short side chain ionomer ratio was set to 0.25 or more, but according to the result in FIG. 3, since the voltage linearly increases relative to the short side chain ionomer ratio, the short side chain ionomer ratio is Even if it is 0.2 or more, a sufficiently high effect can be obtained. Furthermore, high effects can be obtained even if the short side chain ionomer ratio is 0.1 or more. Furthermore, even if the short side chain ionomer ratio is 0.05 or more, sufficient effects can be obtained.
以上のように、本発明にかかる燃料電池用触媒層は、ガス拡散性に優れ、金属触媒粒子の有効利用率が高い触媒層を実現することができるので、安定して高効率な運転が求めら
れる固体高分子形電解質を用いた燃料電池および水電解の電極等の用途にも適用できる。
As described above, the fuel cell catalyst layer according to the present invention can realize a catalyst layer that is excellent in gas diffusivity and has a high effective utilization of metal catalyst particles, so stable and highly efficient operation is required. The present invention is also applicable to applications such as fuel cells using a solid polymer electrolyte, and electrodes for water electrolysis.
１０ カソード触媒層
１１ 導電性担体
１２ Ｐｔ触媒
１３ 触媒
１４ 触媒凝集体
１５ 内部微細孔
１６ 第１のアイオノマー
１７ 第２のアイオノマー
２０ 燃料電池単セル
２１ 電解質膜
２２ アノード触媒層
２３ 電解質膜−電極接合体
２４ アノードガス拡散層
２５ カソードガス拡散層
２６ アノードガスセパレータ
２７ カソードガスセパレータ
２８ 燃料ガス流路
２９ 酸化ガス流路
DESCRIPTION OF SYMBOLS 10 cathode catalyst layer 11 conductive support 12 Pt catalyst 13 catalyst 14 catalyst aggregate 15 internal fine pore 16 1st ionomer 17 2nd ionomer 20 fuel cell single cell 21 electrolyte membrane 22 anode catalyst layer 23 electrolyte membrane electrode assembly 24 anode gas diffusion layer 25 cathode gas diffusion layer 26 anode gas separator 27 cathode gas separator 28 fuel gas flow path 29 oxidation gas flow path
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| JP2018000986A Pending JP2019121521A (en) | 2018-01-09 | 2018-01-09 | Catalyst layer for fuel cell, electrolyte membrane-electrode assembly and fuel cell |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112952122A (en) * | 2019-11-26 | 2021-06-11 | 现代自动车株式会社 | Catalyst slurry for fuel cell and method for preparing catalyst slurry |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112952122A (en) * | 2019-11-26 | 2021-06-11 | 现代自动车株式会社 | Catalyst slurry for fuel cell and method for preparing catalyst slurry |
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