前期遷移金属ヒドリド化合物触媒の開拓と機構解明

早期过渡金属氢化物催化剂的开发及机理阐明

• 批准号: 21J15834
• 负责人: Cao Yu
• 金额: $ 0.96万
• 依托单位: Kyoto University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for JSPS Fellows
• 财政年份: 2021
• 资助国家: 日本
• 起止时间: 2021-04-28 至 2023-03-31
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-21J15834/
• 关键词: ammonia synthesis; hydride

Early 3d transition metals, such as Ti, V, Nb or Cr are known to be inactive for the Haber-Bosch process, due to their strong M-N bonds. 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. 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. These results show that there is more potential for developing new single-phase hydride catalysts of previously overlooked elements without sacrificing activity.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. I reported a topochemical synthesis of a new hexagonal nitride hydride, h-Ca3CrN3H, by heating an orthorhombic nitride, o-Ca3CrN3, under hydrogen at 673 K, accompanied by a rotational structural transformation. The hydrogen intercalation modifies the Ca-N rock-salt-like atomic packing in o-Ca3CrN3 to a face-sharing octahedral chain in h-Ca3CrN3H. Impressively, the h-Ca3CrN3H exhibited stable ammonia synthesis activity when used as a catalyst, even though the early transition metal Cr is not an active element for ammonia synthesis. DFT calculations reveal that nitrogen reduction could be effectively achieved through an associative mechanism.

早期的 3d 过渡金属（例如 Ti、V、Nb 或 Cr）由于其强 M-N 键而对 Haber-Bosch 过程不活跃。我将研究范围扩大到其他早期过渡金属（即 V 和 Nb）的氢化物。这些金属受益于体心立方 (bcc) 相关结构，除了具有相对较低的 M-N 键强度外，还增强了氢化物扩散。氢化钒的活性（很可能具有VH0.44N0.16的活性成分）优于先前报道的TiH2和BaTiO2.5H0.5，并且与Cs-Ru/MgO相当。这些结果表明，在不牺牲活性的情况下开发以前被忽视的元素的新型单相氢化物催化剂具有更大的潜力。拓扑化学反应在发现具有新颖化学和物理性质的新型亚稳态化合物方面取得了巨大进展，使其成为合成新型氢化物材料的有效方法。我报道了一种新的六方氮化物氢化物 h-Ca3CrN3H 的拓扑化学合成，方法是在 673 K 的氢气下加热斜方氮化物 o-Ca3CrN3，并伴随旋转结构转变。氢插层将 o-Ca3CrN3 中的 Ca-N 岩盐状原子堆积改性为 h-Ca3CrN3H 中的共面八面体链。令人印象深刻的是，尽管早期过渡金属 Cr 不是氨合成的活性元素，但 h-Ca3CrN3H 作为催化剂时表现出稳定的氨合成活性。 DFT计算表明氮的减少可以通过关联机制有效地实现。

项目成果

Topochemical Synthesis of Ca3CrN3H Involving a Rotational Structural Transformation for Catalytic Ammonia Synthesis

• DOI: 10.1002/anie.202209187
• 发表时间: 2022-08-23
• 期刊: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
• 影响因子: 16.6
• 作者: Cao, Yu;Kirsanova, Maria A.;Kageyama, Hiroshi
• 通讯作者: Kageyama, Hiroshi

Ammonia Synthesis via an Associative Mechanism on Alkali Earth Metal Sites of Ca3CrN3H

Ca3CrN3H 碱土金属位点上缔合机制合成氨

• DOI: 10.1002/cssc.202300234
• 发表时间: 2023
• 期刊: ChemSusChem
• 影响因子: 8.4
• 作者: Cao Yu;Toshcheva Ekaterina;Almaksoud Walid;Ahmad Rafia;Tsumori Tatsuya;Rai Rohit;Tang Ya;Cavallo Luigi;Kageyama Hiroshi;Kobayashi Yoji
• 通讯作者: Kobayashi Yoji

Vanadium Hydride as an Ammonia Synthesis Catalyst

• DOI: 10.1002/cctc.202001084
• 发表时间: 2020-11-17
• 期刊: CHEMCATCHEM
• 影响因子: 4.5
• 作者: Cao, Yu;Saito, Ayaka;Kageyama, Hiroshi
• 通讯作者: Kageyama, Hiroshi