Titanium Hydride Nanoplates Enable 5 wt% of Reversible Hydrogen Storage by Sodium Alanate below 80°C.

Sodium alanate (NaAlH) with 5.6 wt% of hydrogen capacity suffers seriously from the sluggish kinetics for reversible hydrogen storage. Ti-based dopants such as TiCl, TiCl, TiF, and TiO are prominent in enhancing the dehydrogenation kinetics and hence reducing the operation temperature. The tradeoff, however, is a considerable decrease of the reversible hydrogen capacity, which largely lowers the practical value of NaAlH. Here, we successfully synthesized a new Ti-dopant, i.e., TiH as nanoplates with ~50 nm in lateral size and ~15 nm in thickness by an ultrasound-driven metathesis reaction between TiCl and LiH in THF with graphene as supports (denoted as NP-TiH@G). Doping of 7 wt% NP-TiH@G enables a full dehydrogenation of NaAlH at 80°C and rehydrogenation at 30°C under 100 atm H with a reversible hydrogen capacity of 5 wt%, superior to all literature results reported so far. This indicates that nanostructured TiH is much more effective than Ti-dopants in improving the hydrogen storage performance of NaAlH. Our finding not only pushes the practical application of NaAlH forward greatly but also opens up new opportunities to tailor the kinetics with the minimal capacity loss.