Vanadium Hydride as an Ammonia Synthesis Catalyst
Vanadium Hydride as an Ammonia Synthesis Catalyst
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DOI：
10.1002/cctc.202001084
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发表时间：
2020-11-17
期刊：
影响因子：
4.5
通讯作者：
Kageyama, Hiroshi
中科院分区：
文献类型：
--
作者：
Cao, Yu;Saito, Ayaka;Kageyama, Hiroshi
早期的3d过渡金属，如Ti、V或Nb，由于其强M-N键，已知对Haber-Bosch过程不活跃。然而，最近已经发现一些氢化物化合物可以有效地抵消这种影响，赋予广泛的元素催化活性。利用这些氢化物催化剂，提出了氢化物（和氮化物）的体扩散机制；如果是这样，更开放的结构应该会促进它们的活动。在这里，我们将研究扩展到其他早期过渡金属，V和Nb的氢化物。除了具有相对较低的M-N键强度外，这些金属还受益于体心立方（bcc）相关结构，这些结构增强了氢化物的扩散。氢化钒的活性很可能为VH0.44N0.16，其活性优于先前报道的BaTiO2.5H0.5，在400℃，5 MPa下与TiH2和Cs-Ru/MgO相当。这些结果表明，在不牺牲活性的情况下，开发新的单相氢化物催化剂具有更大的潜力。
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 hydride compounds have been found to effectively counteract this effect, imparting catalytic activity on a wide 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. Here, we expand the study to hydrides of other early transition metals, 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 BaTiO2.5H0.5, and comparable to TiH2 and Cs-Ru/MgO at 400 degrees 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.