Among hydrogen storage materials, hydrogen hydrates have received a particular attention over the last decades. The pure hydrogen hydrate is generated only at extremely high-pressure (few thousands of bars) and the formation conditions are known to be softened by co-including guest molecules such as tetrahydrofuran (THF). Since this discovery, there have been considerable efforts to optimize the storage capacities in hydrates through the variability of the formation condition, of the cage occupancy, of the chemical composition or of the hydrate structure (ranging from clathrate to semi-clathrate). In addition to this issue, the hydrogen insertion mechanism plays also a crucial role not only at a fundamental level, but also in view of potential applications. This paper aims at studying the molecular hydrogen diffusion in the THF hydrate by in-situ confocal Raman microspectroscopy and imaging, and at investigating the impact of strong acid onto this diffusive process. This study represents the first report to shed light on hydrogen diffusion in acidic THF-H₂ hydrate. Integrating the present result with those from previous experimental investigations, it is shown that the hydrogen insertion in the THF hydrate is optimum for a pressure of ca. 55 bar at 270 K. Moreover, the co-inclusion of perchloric acid (with concentration as low as 1 acidic molecules per 136 water molecules) lead to promote the molecular hydrogen insertion within the hydrate structure. The hydrogen diffusion coefficient—measured at 270 K and 200 bar—is improved by a factor of 2 thanks to the acidic additive.

在过去的几十年中，在储氢材料中，水合氢受到了特别的关注。纯水合氢仅在极高的压力（几千巴）下产生，并且已知形成条件会由于共包含客体分子（例如四氢呋喃（THF））而软化。自从这一发现以来，人们一直在努力通过形成条件，网箱占用率，化学组成或水合物结构（从包合物到半包合物）的变化来优化水合物的储存能力。除了这个问题，氢的插入机制不仅在基本层面上，而且在潜在应用方面，都起着至关重要的作用。本文旨在研究分子氢在四氢呋喃水合物中的扩散。原位共聚焦拉曼光谱学和成像，以及研究强酸对该扩散过程的影响。这项研究是首次揭示氢在酸性THF-H ₂水合物中的扩散的报告。将当前结果与之前的实验研究相结合，结果表明，在THF水合物中，氢的插入最适合于钙。在270 K时为55 bar。此外，高氯酸（每136个水分子中的浓度低至1个酸性分子）的共包含物会导致分子氢插入水合物结构中。由于使用了酸性添加剂，在270 K和200 bar下测得的氢扩散系数提高了2倍。