Reinforce the dehydrogenation process of LiAlH4 by accumulating porous activated carbon

Abstract

Herein, it is reported that activated carbon (AC) alters the hydrogen storage behavior of lithium alanate (LiAlH4) prepared by the ball milling technique. Notable improvements in onset decomposition temperature and desorption kinetics are attained for LiAlH4 added 10 wt.% of AC composite compared to as-received and as-milled LiAlH4. The onset decomposition temperature of LiAlH4-10 wt.% AC dropped to 100 °C and 160 °C for the first and second steps. The composite also released 3.4 wt.% of hydrogen after 90 min compared to as-received and as-milled which is less than 0.2 wt.% of hydrogen within the same period. The XRD result discovered an additional peak of the Li3AlH6 and Al compounds appeared after the milling process, concluding that LiAlH4 becomes unstable after the addition of AC. FTIR measurement has verified the presence of the Li3AlH6 and carbon bonding in the LiAlH4-10 wt.% AC composite. The composite's activation energy (Ea) for the first and second steps is 70 kJ/mol and 85 kJ/mol, respectively. These values decrease from as-milled LiAlH4 for both steps, demonstrating the catalytic effect of AC in this system. FESEM images illustrate that after ball milling, the particle size of LiAlH4-10 wt.% AC composite decreases. The considerable improvement in the hydrogen storage characteristic of the LiAlH4-10 wt.% AC composite is thought to be the collaborative role of amorphous carbon.