Releasing H2 from LiBH4-NH3 system

Abstract

Releasing ca. 17.8 wt % of hydrogen was observed from the Co-catalyzed lithium borohydride ammoniate, Li(NH3)4/3BH4 (with equivalent protic and hydridic hydrogen atoms), in the temperature range of 135 to 250 °C in a closed vessel. The low NH3 equilibrium vapor pressure of the ammoniate in the vessel results in the retention of the majority of NH3 in the vicinity of LiBH4, and thus, creates an environment favorable for the direct dehydrogenation rather than deammoniation. The dehydrogenation is a two-step process forming the intermediates Li4BN3H10 and LiBH4. The final solid residue is a mixture of BN and Li3BN2. The presence of Co catalyst effectively reduces the kinetic barrier from 118.9 to 60.0 kJ mol-1.Releasing ca. 17.8 wt % of hydrogen was observed from the Co-catalyzed lithium borohydride ammoniate, Li(NH3)4/3BH4 (with equivalent protic and hydridic hydrogen atoms), in the temperature range of 135 to 250 °C in a closed vessel. The low NH3 equilibrium vapor pressure of the ammoniate in the vessel results in the retention of the majority of NH3 in the vicinity of LiBH4, and thus, creates an environment favorable for the direct dehydrogenation rather than deammoniation. The dehydrogenation is a two-step process forming the intermediates Li4BN3H10 and LiBH4. The final solid residue is a mixture of BN and Li3BN2. The presence of Co catalyst effectively reduces the kinetic barrier from 118.9 to 60.0 kJ mol-1