Improved hydrogen release from magnesium borohydride by ZrCl4 additive

•ZrCl4 decreased the activation barrier for Mg(BH4)2 dehydrogenation.•The catalyst reduced the actual dehydrogenation steps.•The catalyst increased the rate of MgH2 dehydrogenation.•ZrCl4 reduced to ZrCl3 and metallic Zr which acts as a catalyst.

Thermal dehydrogenation of Mg(BH4)2 was investigated with ZrCl4 as a catalyst in vacuum and argon gas flow conditions. The results have been compared with the thermal dehydrogenation of pure-Mg(BH4)2 under similar experimental conditions. Two endothermic peaks were observed for pure Mg(BH4)2 before the actual dehydrogenation reaction whereas; in the case of catalyzed Mg(BH4)2, an exothermic followed by endothermic peaks appeared. Marginal hydrogen was evolved during these low-temperature events. The actual dehydrogenations of pure-Mg(BH4)2 were started at 235 °C and ended at 450 °C with three clear dehydrogenation steps. However; in the case of catalyzed Mg(BH4)2 dehydrogenation started very early (onset 197 °C) and completed before 400 °C with merely two visible dehydrogenation steps. The lower dehydrogenation temperature of catalyzed Mg(BH4)2 was attributed to the reduced apparent activation energy as compared to the pure Mg(BH4)2.

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