Study of interactions with phonons, electrons and hydrogen in proton quantum diffusion

2022 Fiscal Year Final Research Report

• Project/Area Number: 21K20349
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0202:Condensed matter physics, plasma science, nuclear engineering, earth resources engineering, energy engineering, and related fields
• Research Institution: The University of Tokyo
• Principal Investigator: Ozawa Takahiro 東京大学, 生産技術研究所, 助教 (20910144)
• Project Period (FY): 2021-08-30 – 2023-03-31
• Keywords: 金属水素化物 / 拡散 / 量子効果

Outline of Final Research Achievements

Hydrogen (H) reveals quantum diffusion at low temperature due to its light mass. However, the mechanism of the H quantum diffusion has not been elucidated in detail because it is difficult to detect H and measure the slow diffusion at low temperature. In this study, we performed electrical conductivity measurements to observe the H diffusion in materials. The hydrogen hopping rates at low temperature were successfully obtained in Pd and Pt hydrides. The structures of these hydrides were analyzed to determine the H hopping path by the nuclear reaction analysis combined with the ion channeling technique. The concentration dependence and isotope effects on the temperature dependence of the hydrogen hopping rate were experimentally investigated to elucidate the influences of phonons and electrons on quantum diffusion of H.

Free Research Field

水素化物

Academic Significance and Societal Importance of the Research Achievements

水素貯蔵材料への水素吸蔵・脱離，触媒表面での水素化反応，燃料電池の固体電解質におけるプロトン移動など，水素の拡散は様々な場面で重要である．水素は質量が小さいため，特に低温においては量子的な性質が露わとなる．しかし水素を直接観測することは難しく，これまで低温における固体中の水素拡散はほとんど観測されてこなかった．今回，電気伝導測定およびイオンビームを用いた構造解析を駆使し，低温における水素の拡散頻度の計測と拡散径路の同定に成功した．低温の水素拡散の計測方法を確立した本研究は，水素の量子拡散の本質的理解に向けて重要な意義を持ち，効率的な水素吸蔵など応用面への貢献も期待できる成果である．