| 研究実績の概要 |
Early 3d transition metals, such as Ti, V, or Nb are known to be inactive for the Haber-Bosch process, due to their strong M-N bonds. However, recently some early transition metal hydride compounds have been found to effectively counteract this effect, imparting catalytic activity on a wider range of elements. With these hydride catalysts, hydride (and nitride) bulk diffusion mechanisms have been proposed; if so, more open structures should enhance their activity.I expanded the study to hydrides of other early transition metals, i.e., V and Nb. These metals benefit from body-centered cubic (bcc) related structures which enhance hydride diffusion, in addition to having relatively lower M-N bond strengths.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
The activity of vanadium hydride, most likely with an active composition of VH0.44N0.16, is superior to the previously reported TiH2 and BaTiO2.5H0.5, and comparable to Cs-Ru/MgO at 400 °C under 5 MPa. These results show that there is more potential for developing new single-phase hydride catalysts of previously overlooked elements without sacrificing activity.
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| 今後の研究の推進方策 |
Topochemical reactions have led to great progress in the discovery of new metastable compounds with novel chemical and physical properties, making it an effective method of synthesizing new hydride materials. With these reactions, the overall crystal structure of the host material is generally maintained. The further research will be focused on the topochemical synthesis of a new hexagonal nitride hydride ammonia synthesis catalyst, h-Ca3CrN3H, by heating an orthorhombic nitride, o-Ca3CrN3, under hydrogen at 673 K, accompanied by a rotational structural transformation.
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