Plastic Waste as a Resource for Liquid Organic Hydrogen Carriers

Liquid organic hydrogen carriers (LOHCs) are increasingly recognized as promising platforms for large-scale hydrogen storage and transportation. However, most established LOHC systems rely on aromatic compounds derived from fossil resources, raising concerns regarding the long-term sustainability of hydrogen storage infrastructures. This review explores the potential of waste plastics as alternative carbon sources for LOHC molecules by systematically evaluating the structural compatibility of major commercial plastics, including polystyrene (PS), polyethylene terephthalate (PET), polycarbonate (PC), polyethylene (PE), and polypropylene (PP), with hydrogen carrier chemistry. Particular emphasis is placed on the relationship between polymer structural motifs and LOHC-relevant molecular architectures, as well as recent catalytic upcycling strategies such as aromatization, hydrodeoxygenation, cyclization, and tandem upgrading reactions that generate aromatic and cyclic hydrocarbons relevant to reversible hydrogen storage. We further discuss recent proof-of-concept studies demonstrating the feasibility of converting plastic waste into LOHC-relevant systems and evaluate their hydrogen storage performance. Finally, key challenges and future opportunities are highlighted from the perspectives of molecular design, catalyst development, hydrogen integration strategies, and system-level energy efficiency. By linking plastic upcycling with LOHC chemistry, this review highlights the potential of waste plastics as alternative hydrocarbon feedstocks for hydrogen storage and transportation, and aims to provide a foundation for future research.