Thermodynamic guidelines for the prediction of hydrogen storage reactions and their application to destabilized hydride mixtures

Abstract

We propose a set of thermodynamic guidelines aimed at facilitating more robust screening of hydrogen-storage reactions. The utility of the guidelines is illustrated by reassessing the validity of reactions recently proposed in the literature and through vetting a list of more than 20 candidate reactions based on destabilized $\mathrm{Li}\mathrm{B}{\mathrm{H}}_{4}$ and $\mathrm{Ca}{(\mathrm{B}{\mathrm{H}}_{4})}_{2}$ borohydrides. Our analysis reveals several reactions having both favorable thermodynamics and relatively high hydrogen densities (ranging from $5\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}9\phantom{\rule{0.3em}{0ex}}\mathrm{wt}\phantom{\rule{0.2em}{0ex}}%$ ${\mathrm{H}}_{2}$ and $85\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}100\phantom{\rule{0.3em}{0ex}}\mathrm{g}$ ${\mathrm{H}}_{2}∕\mathrm{l}$), and it demonstrates that chemical intuition alone is not sufficient to identify valid reaction pathways.