Advanced Hydrogen‐Storage Materials Based on Sc‐, Ce‐, and Pr‐Doped NaAlH₄

Abstract

The most favorable dopants for solid‐state hydrogen‐storage materials are still considered to be compounds of titanium in spite of intensive research on other catalysts. Here, we show that NaAlH4 doped with ScCl3 is a highly efficient dopant, both with respect to storage capacity and kinetics: 2 mol % ScCl3 exhibits a nearly theoretical hydrogen‐storage capacity (4.9 wt %, see graph). Other rare‐earth metal trichlorides are also investigated.

Vacancy mediated desorption of hydrogen from a sodium alanate surface: An ab initio spin-polarized study

“…Since then, substantial progress has been made experimentally in studying the kinetics of Ti-doped sodium alanate for both the hydrogenation and dehydrogenation processes. 13,14 Currently, it is believed that the final oxidation state of the titanium is zero, 15,16 which is independent of the initial oxidation state and how Ti is added to NaAlH 4 . However, there is still a continuing experimental controversy on precisely where the Ti resides and the exact role of the catalyst.…”

Influence of the dopant during the one step mechano-chemical synthesis of sodium alanate

“…These two maxima are better resolved for the lowest amount of TiCl 3 since the reaction rates are slower. [8] have been reported to increase the kinetic performance of NaAlH 4 . We therefore performed milling of NaH and Al with TiCl 3 , ScCl 3 , CeCl 3 or Ti to study their efficiency.…”

“…In addition, diffusion of hydrogen inside particles is promoted by dislocations appearing during milling and the reduction of particle size. Further research was also focused on the screening of suitable dopants [7,8]. In this paper, the one-step mechano-chemical synthesis using reactive ball milling of NaAlH 4 doped with different additives is described.…”

Challenges in hydrogen storage

“…It was thus a major breakthrough, when Bogdanovič and Schwickardi discovered that both reactions can be strongly accelerated by doping the NaAlH 4 with transition metal compounds, most notably with titanium species [17]. This system has up to now been studied very intensively, and both improved methods of doping [18] and improved catalysts have been developed [19,20]. The method of choice for the doping reaction is ball milling, the best catalyst described so far is scandium (which, however, would probably be too expensive for large scale application).…”