Development of hydrogen membranes based on hydride ion conductors

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H02066
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 36020:Energy-related chemistry
• Research Institution: Hokkaido University
• Principal Investigator: Aoki Yoshitaka 北海道大学, 工学研究院, 准教授 (50360475)
• Co-Investigator(Kenkyū-buntansha): 小林 玄器 分子科学研究所, 物質分子科学研究領域, 准教授 (30609847)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: ヒドリドイオン伝導体 / 金属窒化物 / アンモニア合成

Outline of Final Research Achievements

The incorporation of mobile hydridic defects was demonstrated for low-crystalline Zr3N4-δ films deposited by radio frequency reactive sputtering under a flow of nitrogen-rich reactive gases. Extended X-ray adsorption fine structure analysis confirmed that the local coordination environment around the Zr atoms was very close to that of the orthorhombic Eu3O4 phase. Pristine Zr3N4-δ films exhibited n-type semiconductor behavior owing to the presence of nitrogen vacancy donors. Electrochemical analysis and spectroscopy confirmed that Zr3N4-δ was readily hydrogenated upon exposure to H2 gas at 300 degreeC to form hydridic defects via electron donation to hydrogen adatoms. Hence, the hydrogenated film exhibited H- ion/electron mixed conductor behavior in an H2 atmosphere.　In addition, ammonia synthesis was demonstrated with membrane reactors comprising of H-/e- mixed conducting MoN nanocrystalline membranes for hydrogen separation and hydride ion-containing catalysts support.

Free Research Field

エネルギー化学

Academic Significance and Societal Importance of the Research Achievements

持続可能な低炭素社会を築くには、再生可能エネルギー由来の電力を活用し、CO2やN2等を有用な物質へと転換する資源循環技術が必須である。ヒドリドイオン(H-)は、質量が小さく分極率が大きいため、固体イオン伝導に適しており、また、NHEに対して-2.3Vの高いH2 / H-標準酸化還元電位をもつ。これらの特性により、H-イオン伝導体は、CO2還元再資源化やアンモニア電解合成に有効な電極材料や水素膜リアクター材料として有効である。本研究では還元雰囲気で非常に安定な金属窒化物をベースとしたH-イオン伝導性電極の新規作成法と、それを活用したアンモニア合成膜リアクターの実証を行った。