Advanced hydrogen storage of the Mg–Na–Al system:A review

A solid-state storage system is the most practical option for hydrogen because it is more convenient and safer.Metal hydrides,especially MgH_(2),are the most promising materials that offer high gravimetric capacity and good reversibility.However,the practical application of MgH_(2) is restricted by slow sorption kinetics and high stability of thermodynamic properties.Hydrogen storage performance of MgH_(2) was enhanced by introducing the Mg–Na–Al system that destabilises MgH_(2) with NaAlH_(4).The Mg–Na–Al system has superior performance compared to that of unary MgH_(2) and NaAlH_(4).To boost the performance of the Mg–Na–Al system,the ball milling method and the addition of a catalyst were introduced.The Mg–Na–Al system resulted in a low onset decomposition temperature,superior cyclability and enhanced kinetics performances.The Al_(12)Mg_(17) and NaMgH_(3) that formed in situ during the dehydrogenation process modify the reaction pathway of the Mg–Na–Al system and alter the thermodynamic properties.In this paper,the overview of the recent progress in hydrogen storage of the Mg–Na–Al system is detailed.The remaining challenges and future development of Mg–Na–Al system are also discussed.This paper is the first review report on hydrogen storage properties of the Mg–Na–Al system.

铝氢化钠储氢性能及其改进方法研究进展

配位氢化物NaAlH_(4)具有较高的储氢密度且生产成本低廉,是一种典型的储氢材料;然而,较高的脱氢温度、较慢的氢吸放速率及较差的可逆性限制了其实际应用。作为一种很有前途的车载储氢介质,其储氢性能的改性研究长期备受关注。论述了NaAlH_(4)储氢性能及其改进方法,阐明了添加催化剂和结构纳米化2种基本改进方法的原理,也阐述了理论模拟在研究NaAlH4储氢性能中的重要促进作用。

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

Sodium alanate(NaAlH_(4))with 5.6 wt%of hydrogen capacity suffers seriously from the sluggish kinetics for reversible hydrogen storage.Ti-based dopants such as TiCl_(4),TiCl_(3),TiF_(3),and TiO_(2) 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_(4).Here,we successfully synthesized a new Ti-dopant,i.e.,TiH_(2) as nanoplates with~50 nm in lateral size and~15 nm in thickness by an ultrasound-driven metathesis reaction between TiCl_(4) and LiH in THF with graphene as supports(denoted as NP-TiH_(2) @G).Doping of 7 wt%NP-TiH_(2) @G enables a full dehydrogenation of NaAlH_(4) at 80℃ and rehydrogenation at 30℃ under 100 atm H_(2) with a reversible hydrogen capacity of 5 wt%,superior to all literature results reported so far.This indicates that nanostructured TiH_(2) is much more effective than Tidopants in improving the hydrogen storage performance of NaAlH_(4).Our finding not only pushes the practical application of NaAlH_(4) forward greatly but also opens up new opportunities to tailor the kinetics with the minimal capacity loss.

Single Ti atoms coupled with Ti-O clusters enable low temperature hydrogen cycling by sodium alanate

Ti-based catalysts are known to improve the hydrogen storage performance of NaAlH4by facilitating the dissociation/recombination of H-H and Al-H bonds.The catalytic activity of metallic Ti species strongly depends on its particle size and dispersity.Ti clusters and even single atoms are therefore highly desirable,but their controllable fabrication has been highly challenging.He rein,we demonstrate a novel facile sonochemical synthesis of a Ti-O clusters featuring single Ti atom catalyst at room temperature.Through reducing TiCl_(4)by MgBu_(2)with ultrasound instead of heating as driving force,numerous single Ti atoms coupled with Ti-O clusters with Ti loading on graphene(Ti_(1)/Ti-O@G)up to 22.6 wt%have been successfully obtained.The prepared Ti_(1)/Ti-O@G contributes high reactivity and superior catalytic activity,therefore enabling full dehydrogenation of NaAlH_(4)at 80℃in thermogravimetric mode and re-hydrogenation at 30℃and 10 MPa with 4.9 wt% H_(2).This fact indicates for the first time that single Ti atom catalyst with high loading is highly effective in catalyzing hydrogen cycling of NaAlH4at remarkably reduced temperatures.