A solid–solid reaction enhanced by an inhomogeneous catalyst in the (de)hydrogenation of a lithium–hydrogen–nitrogen system

Abstract

The reaction mechanism of the (de)hydrogenation of a LiNH₂ + LiH mixture with a nanoscale catalyst has been investigated. In this research, the position of each solid phase was examined by transmission electron microscopy (TEM). The observation showed that LiH particles, around 100 nm in size, formed around LiNH₂ in the hydrogenation process. According to in situ TEM observation of the dehydrogenation process, the LiH particles became smaller as they reacted with LiNH₂. Fine particles of Li₂NH with crystallites of size 30–40 nm formed on the surface of the LiNH₂. It indicated that H⁺ from the LiNH₂ moved to the interface and combined with H⁻ from the LiH in the dehydrogenation process, consequently H₂ was released. At the same time, Li⁺ ions diffused from the LiH to the LiNH₂ through the interface and Li₂NH formed. On the other hand, it was confirmed that the catalyst was located at the interface between the LiH and LiNH₂. It was found that the catalyst had the effect of improving the migration of Li⁺ from LiH to LiNH₂.