Improved kinetic behaviour of Mg(NH2)2-2LiH doped with nanostructured K-modified-LixTiyOz for hydrogen storage
Gökhan Gizer, Julián Puszkiel, María Victoria Castro Riglos, Claudio Pistidda, J. Lopez, Martín Mizrahi, Antonio Santoru, Thomas Gemming, Jochi Tseng, Thomas Klassen, Martin Dornheim
Abstract
Abstract The system Mg(NH 2 ) 2 + 2LiH is considered as an interesting solid-state hydrogen storage material owing to its low thermodynamic stability of ca. 40 kJ/mol H 2 and high gravimetric hydrogen capacity of 5.6 wt.%. However, high kinetic barriers lead to slow absorption/desorption rates even at relatively high temperatures (>180 °C). In this work, we investigate the effects of the addition of K-modified Li x Ti y O z on the absorption/desorption behaviour of the Mg(NH 2 ) 2 + 2LiH system. In comparison with the pristine Mg(NH 2 ) 2 + 2LiH, the system containing a tiny amount of nanostructured K-modified Li x Ti y O z shows enhanced absorption/desorption behaviour. The doped material presents a sensibly reduced (∼30 °C) desorption onset temperature, notably shorter hydrogen absorption/desorption times and reversible hydrogen capacity of about 3 wt.% H 2 upon cycling. Studies on the absorption/desorption processes and micro/nanostructural characterizations of the Mg(NH 2 ) 2 + 2LiH + K-modified Li x Ti y O z system hint to the fact that the presence of in situ formed nanostructure K 2 TiO 3 is the main responsible for the observed improved kinetic behaviour.