Affiliation |
Engineering educational research section Department of Applied Chemistry Program |
Title |
Professor |
External Link |
OKUYAMA Yuji
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Research Areas 【 display / non-display 】
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Nanotechnology/Materials / Inorganic compounds and inorganic materials chemistry
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Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Electron device and electronic equipment
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Nanotechnology/Materials / Metals production and resources production
Papers 【 display / non-display 】
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Li K., Murakami T., Nagata Y., Mikami Y., Yamauchi K., Kuroha T., Okuyama Y., Mizutani Y., Mori M., Araki T.
Applied Energy 381 2025.3
Publishing type:Research paper (scientific journal) Publisher:Applied Energy
Protonic ceramic fuel cells (PCFCs) have garnered significant interest due to their theoretically high fuel utilization and excellent energy efficiency at intermediate temperatures (400–600 °C). While the performance of PCFCs has improved dramatically in recent years, the system electrical efficiency is often lower than the corresponding cell energy efficiency due to energy loss in a PCFC system. This study focuses on achieving >70% system electrical efficiency (lower heating value-LHV) in a H2-powered PCFC system. The required property values such as the conductivities and diffusion coefficients of proton and hole in the electrolyte, as well as the exchange current densities and reaction resistances at electrodes are revealed through a validated numerical model compared to the experimental results of a high-performance PCFC. It offers significant empirical insights for advancing high-performance PCFCs capable of achieving >70% system electrical efficiency.
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Nakamura K., Mori M., Okuyama Y.
Solid State Ionics 417 2024.12
Publishing type:Research paper (scientific journal) Publisher:Solid State Ionics
In protonic ceramic fuel cells using Ba(Zr,M)O3-δ (M: trivalent dopant elements) as the electrolyte, the precipitation of BaM2NiO5 due to Ni diffusion from the co-sintered NiO-based electrode causes degradation of protonic ceramic fuel cells. However, BaM2NiO5 itself has been little studied, and even possible stable crystal structures and compositions have not been fully characterized. In this study, we investigated the dynamic and energetic stability of BaM2NiO5 for various trivalent M elements by using first-principles calculations. First, dynamically stable crystal structures were determined for all compositions from phonon dispersion analysis. The formation energies showed negative values in the case of M = lanthanide elements, B, Ga, Tl and Y. The contribution of vibrational entropy to the formation energy of BaM2NiO5 was insignificant, and the internal energy was dominant. The chemical bonding analysis revealed that in BaM2NiO5, the covalent nature of the M-O bond and the ionic nature of the Ba[sbnd]O bond are dominant in the stability of the crystal structure. Precipitation of BaM2NiO5 in Ba(Zr,M)O3-δ was suggested to be dominated by a specific threshold value of formation energy. The validity of that assumption was discussed in terms of the relationship between the factors involved in precipitation and the ionic radius of M element. The formation energy of BaM2NiO5 in M = lanthanide elements and Y showed a downward convex tendency with M = Pm as the minimum value. The reason for this was discussed in terms of the characteristics of the crystal structure of BaM2NiO5, suggesting that the tensile strain in the M-O bonds and the compressive strain in the Ni[sbnd]O and Ba[sbnd]O bonds relax with the ionic radius of the M element.
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Mikami Y., Goto T., Asano H., Kasuga K., Yamauchi K., Kuroha T., Okuyama Y.
Journal of Power Sources 613 2024.9
Publishing type:Research paper (scientific journal) Publisher:Journal of Power Sources
To investigate the effect of Co in cathodes on the durability of protonic ceramic fuel cells (PCFC) using a BaZr0.8Yb0.2O3-δ electrolyte, new cathode materials, specifically Ba(Zr0.875-xYb0.125Cox)O3-δ (x = 0.125, 0.25, 0.375, 0.625, and 0.75), were employed. We examined several material properties of the cathodes and evaluated cell performance, showing that Ba(Zr0.375Yb0.125Co0.5)O3-δ exhibits high performance and a matching thermal expansion coefficient with the electrolyte. During the 1000 h power generation test, the segregation of Co and anode-derived Ni in the cathode progressed. Segregation of Co and Ni was also observed at the grain boundaries in the electrolyte, indicating a decrease in the mechanical strength of the electrolyte caused by the diffusion of Co from the cathode and Ni from the anode. From these results, it became clear that the suppression of Co diffusion into the electrolyte is an important issue for the practical application of PCFCs with a BaZr0.8Yb0.2O3-δ electrolyte and Co-containing cathodes.
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Development of defect structure-type proton conductors and its application to sensors and fuel cells Invited Reviewed
OKUYAMA Yuji
Oyo Buturi 93 ( 3 ) 149 - 155 2024.3
Authorship:Lead author, Corresponding author Language:Japanese Publishing type:Research paper (scientific journal) Publisher:The Japan Society of Applied Physics
Defect structure-type proton conductors are ceramics in which hydrogen ions (protons) dissolve in oxides and diffuse in the crystal. The material has attracted much attention as an electrolyte for hydrogen sensors and fuel cells. In this review, the material properties and polarization characteristics of defect structure-type proton conductors will be explained, and the application to hydrogen sensors and fuel cells will be introduced.
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Yuichi Mikami, Yuki Sekitani, Kosuke Yamauchi, Tomohiro Kuroha, Yuji Okuyama
ACS Applied Energy Materials 7 ( 3 ) 1136 - 1148 2024.2
Authorship:Corresponding author Publishing type:Research paper (scientific journal)
Protonic ceramic fuel cells (PCFCs) use a proton-conducting oxide as the electrolyte, leading to a high power density and energy conversion efficiency at intermediate temperatures. Ytterbium-doped barium zirconate has a high proton conductivity and chemical stability against carbon dioxide, making it an attractive electrolyte material for PCFCs. The durability of fuel cells is a critical issue for realizing practical applications of PCFCs, and dissolution of the transition metals from the electrodes into the electrolyte is expected to decrease the durability. In this study, we investigated the effect of dissolution of transition metals (Ni, Co, Fe, and Mn) into BaZr0.8Yb0.2O3−δ on the proton transport properties and on the cell properties. The proton conductivity and proton transport number decreased with an increasing concentration of transition-metal elements, and the Co was found to have a particularly large effect on the material properties of BaZr0.8Yb0.2O3−δ. As for cell properties, anode-supported PCFCs with different cathode firing temperatures were evaluated. The OCV and the maximum power density were low in the cell with high concentrations of Co and Fe in the BaZr0.8Yb0.2O3−δ electrolyte, suggesting the decrease of proton transport number due to dissolution of Co and Fe. Furthermore, based on the measured proton transport properties, the effects of transition-metal dissolution on the power density and energy efficiency of PCFCs were estimated, and the trends were consistent with the results of the cell test. These results indicate that the dissolution of transition metals, especially Co, has a significant effect on the performance and durability of PCFCs using the BaZr0.8Yb0.2O3−δ electrolyte.
Books 【 display / non-display 】
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カーボンニュートラルに向けた水素製造・P2Gと関連技術の最新動向
奥山勇治( Role: Contributor , 第3章 プロトン伝導性セラミックスを用いた純水素製造)
シーエムシーリサーチ 2022.12
Language:Japanese Book type:Scholarly book
MISC 【 display / non-display 】
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機械学習を用いた ペロブスカイト型 酸化物中のプロトン 伝導度予測 Invited Reviewed
奥山勇治、堂園航汰
セラミックス 58 ( 11 ) 727 - 731 2023.11
Authorship:Lead author, Corresponding author Language:Japanese Publishing type:Article, review, commentary, editorial, etc. (scientific journal)
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Phase stability of Ba(Zr,Yb)O<sub>3-δ</sub>-based perovskite electrolytes under a fabrication process
松田マリック隆磨, 小林駿, 森昌史, 島田寛之, 鷲見裕史, 水谷安伸, 奥山勇治, 見神祐一, 山内孝祐, 黒羽智宏
燃料電池シンポジウム講演予稿集(CD-ROM) 30th 2023
Publishing type:Rapid communication, short report, research note, etc. (scientific journal)
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プロトン伝導性セラミックスを用いた電気化学デバイス Invited Reviewed
奥山勇治
セラミックス 57 ( 11 ) 10 - 714 2022.11
Authorship:Lead author, Corresponding author Language:Japanese Publishing type:Article, review, commentary, editorial, etc. (scientific journal)
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コヒーレントテラヘルツパルスでみる燃料電池で用いられる固体電解質内の高速イオン伝導
永井正也、奥山勇治、可児幸宗
レーザー研究 ( 50 ) 198 - 201 2022
Publishing type:Article, review, commentary, editorial, etc. (scientific journal)
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20 ( 4 ) 80 - 91 2021
Language:Japanese Publishing type:Rapid communication, short report, research note, etc. (scientific journal)
Presentations 【 display / non-display 】
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Yb添加ジルコン酸バリウムを電解質とした燃料電池の耐久性
奥山 勇治、原田 佳明、見神 祐一、山内 孝祐、黒羽 智宏
電気化学会91回大会
Event date: 2024.3.14 - 2024.3.16
Language:Japanese Presentation type:Oral presentation (general)
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H/D同位体効果を用いたアノード支持型PCFCインピーダンスの電極素反応帰属と劣化要因の特定
奥山勇治、春日圭太、見神祐一、山内孝祐、黒羽智宏、鷲見裕史
第32回SOFC研究発表会
Event date: 2023.12.14 - 2023.12.15
Language:Japanese Presentation type:Oral presentation (general)
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機械学習を活用した次世代燃料電池材料の開発 Invited
奥山勇治
2023年度機械学習ハンズオン講習会
Event date: 2023.11.27 - 2023.11.29
Language:Japanese Presentation type:Oral presentation (invited, special)
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Y添加ジルコン酸バリウムにおけるプロトン拡散へのドーパント濃度と会合の影響
奥山勇治、設楽一希、高橋和也、桑原彰秀、山崎仁丈
第49回固体イオニクス討論会
Event date: 2023.11.15 - 2023.11.17
Language:Japanese Presentation type:Oral presentation (general)
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プロトン伝導性セラミック燃料電池における耐久性向上のための中間層構造の検証
原田佳明、奥山勇治
トークシャワー・イン九州2023
Event date: 2023.9.27 - 2023.9.28
Language:Japanese Presentation type:Poster presentation
Awards 【 display / non-display 】
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Interface Ionicss/SSI seminar Award 2023 Platinum Prize
2023.8 第17回固体イオニクスセミナー
原田佳明、奥山勇治
Award type:Award from Japanese society, conference, symposium, etc.
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第60回化学関連支部合同九州大会電気化学セッション優秀研究発表賞
2023.7 電気化学会九州支部
東雲遥香、奥山勇治
Award type:Award from Japanese society, conference, symposium, etc.
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第59回化学関連支部合同九州大会電気化学セッション優秀研究発表賞
2022.7 電気化学九州支部
藤本聖、奥山勇治
Award type:Award from Japanese society, conference, symposium, etc.
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PACRIM13 FCDICポスター賞
2019.10 宮崎大学
辻川皓太
Award type:Award from international society, conference, symposium, etc. Country:Japan
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田川記念固体化学奨励賞
2017.3 電気化学会 固体化学新しい指針を探る研究会 プロトン伝導性酸化物の欠陥構造と電気化学デバイスへの応用
奥山勇治
Award type:Award from Japanese society, conference, symposium, etc. Country:Japan
Grant-in-Aid for Scientific Research 【 display / non-display 】
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Determination of defect structure in proton-conductive ceramic-electrolyte materials by light-induced pulsed ESR
Grant number:24K06923 2024.04 - 2027.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
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プロトン伝導性酸化物中の内部ポテンシャル分布制御による機能創製
Grant number:16H06124 2016.04 - 2019.03
科学研究費補助金 若手研究(A)
Authorship:Principal investigator
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酸化物の微視的欠陥制御による高プロトン伝導性材料の設計
Grant number:25709072 2013.04 - 2016.03
科学研究費補助金 若手研究(A)
本研究では化学的安定性、高い機械的強度を備えた酸化物型プロトン伝導体のプロトン伝導性を最大限まで向上させる材料設計指針を明らかにし、発電システムとして実用に耐えうるプロトン伝導体を用いてPCFC(プロトンセラミック燃料電池)を開発することを目的とする。
これまで酸化物プロトン導電体はアクセプタードーパント(低原子価カチオン)を添加した際の負の相対電荷をプロトンで補うことから添加した低原子カチオン濃度までプロトンが溶解すると考えられていた。しかしながら申請者のこれまでの研究でプロトンの最大溶解量は低原子価カチオン濃度まで達していないことが明らかになった。また、プロトンは低原子価カチオンと会合(トラップ)しており著しく水素の拡散係数を減少させていることが確認され、プロトン伝導体には大きな2つ問題点を抱えていることが明らかとなった。本研究はこの2つの問題を材料調製の観点から解決することでプロトンが溶解しやすく動きやすい酸化物すなわち最高性能を有した酸化物プロトン伝導体を設計創製し、燃料電池への応用を目指すものである。 -
不定比複合酸化物をベースとした固体電解質の高温電気化学特性とその工学的応用
Grant number:07J11286 2007.04 - 2009.03
科学研究費補助金 特別研究員推奨費
マグネシウムアルミネートスピネルの電気化学的特性(ガス濃淡電池、電気伝導度、水素溶解量、水素拡散係数)を評価しスピネルを電解質とした溶融鋳鉄用Mgセンサーの開発を試みた。
Available Technology 【 display / non-display 】
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プロトン伝導性セラミックスを用いた次世代燃料電池開発
ガス濃淡電池型水素センサの開発
機械学習を活用した新規プロトン伝導性セラミックスの探索Related fields where technical consultation is available:材料科学分野、電気化学分野、水素エネルギー関連分野、金属生産工学分野、固体イオニクス分野
Message:セラミックス合成から機能性評価、応用研究まで研究室で実施しています。
学術的な点でお困りの場合はご相談ください。