Fast hydrogen release under moderate conditions from NaBH4 destabilized by fluorographite

Abstract

A simple approach to dramatically enhance the dehydrogenation properties of sodium borohydride is achieved by ball milling NaBH₄ with fluorographite (FGi). It was found that the ball-milled NaBH₄–FGi composite starts to release hydrogen without impurity gas at a lower temperature of 125 °C, and obtains a hydrogen desorption capacity of ca. 4.8 wt% below 130 °C in seconds, which is improved markedly compared to the ball-milled pristine NaBH₄. The significant thermodynamic and kinetic improvement of the NaBH₄–FGi composite can be ascribed to the reaction between NaBH₄ and FGi as well as the formation of micro-scale NaBH₄. Moreover, since the dehydrogenation process of NaBH₄–FGi composite is exothermal, the fully reverse reaction is not feasible. In-depth investigations show that the partial rehydrogenation is due to the formation of Na₂B₁₂H₁₂ and another new borohydride.