Enhanced hydrogen storage properties of NaAlH4 with the addition of CoTiO3 synthesised via a solid-state method.

Abstract

CoTiO3 that was synthesised via the solid-state method was effective in ameliorating the desorption behaviour of NaAlH4. The initial desorption temperature of NaAlH4 catalysed by different weight percentage of CoTiO3 (5 wt%, 10 wt%, 15 wt% and 20 wt%) was dramatically decreased to around 130–160 °C for the first desorption stage and decreased to around 182–198 °C for the second desorption stage, which is lower than milled NaAlH4. The composite sample also exhibits 15–18 times faster desorption kinetics at 150 °C where the NaAlH4-CoTiO3 composite could release 3.0–3.7 wt% of H2 in 60 min but milled NaAlH4 only could release 0.2 wt% H2 in the same time duration. The activation energies for the two-desorption stage of NaAlH4 was downshifted to 85.5 and 91.6 kJ/mol, lowered by 30.7 and 35.5 kJ/mol than milled NaAlH4, respectively. The beneficial catalytic effect of CoTiO3 can be attributed to the in-situ formation of Al-Co and Al-Ti alloys after the desorption process of the NaAlH4-CoTiO3 system. These findings pave the way for the development of highly effective catalysts for NaAlH4 as a favourable material for hydrogen storage.