Abstract
Liquid organic hydrogen carriers (LOHCs) are a promising class of hydrogen storage media in which hydrogen is reversibly bound to organic molecules. In this work, we focus explicitly on cyclic LOHCs (both homocyclic and heterocyclic organic compounds) and their catalytic dehydrogenation. We clarify that other carriers (e.g., alcohols like methanol or carboxylic acids like formic acid) exist but are not the focus here; these alternatives are discussed only in comparative context. Cyclic LOHCs typically enable safe, ambient-temperature hydrogen storage with hydrogen contents around 6–8 wt%. Key challenges include the high dehydrogenation temperatures (often 200–350 °C), catalyst costs, and catalyst deactivation via coke formation. We introduce a comparative analysis table contrasting cyclic LOHCs with alternative carriers in terms of hydrogen density, operating conditions, catalyst types, toxicity, and cost. We also expand the catalyst discussion to highlight coke formation mechanisms, and the use of mesoporous metal-oxide supports to mitigate deactivation. Finally, a techno-economic analysis is provided to address system costs of LOHC storage and regeneration. Finally, we underscore the viability and limitations of cyclic LOHCs, including practical storage capacities, catalyst life, and projected costs.