Liquid organic hydrogen carriers

Liquid organic hydrogen carriers (LOHCs) are organic molecules that can store hydrogen through a catalytic exothermic hydrogenation reaction at a certain pressure and mild temperature to produce a hydrogen-rich molecule, releasing heat. Subsequently, this hydrogen-rich molecule will be dehydrogenated in an endothermic catalytic reaction, which requires high temperature and mild pressure to produce the original organic molecule and hydrogen. Although there is some degradation during the dehydrogenation process, the original organic molecule is reused in the following hydrogenation stages. LOHCs must allow reasonably high hydrogen storage capacity (>5.5 wt%), and should be safe to handle (non-toxic, non-flammable, non-explosive), abundant and cheap. Some LOHCs are cycloalkanes, N-substituted heterocycles, 1,2-BN-heterocycles, liquid inorganic hydrides, and methanol and formic acid. Currently, however, the hydrogenation and dehydrogenation processes require energy, corresponding to around 35-40% of the energy content of the stored hydrogen, because, among other things, dehydrogenation temperatures are high. Research seeks to improve the overall efficiency of using LOHCs by looking for improved catalysts that enable dehydrogenation at lower temperatures (<150 °C) with limited use of precious metals, efficient heat management and higher hydrogen recovery rates after purification.