Catalytic Advances in Naphthalene-Decalin Liquid Organic Hydrogen Carriers: A Comprehensive Review

Liquid organic hydrogen carriers (LOHCs) provide an established framework for the safe, high-density storage, and transportation of hydrogen. Among current LOHC candidates, the naphthalene-decalin system distinguishes itself with a theoretical hydrogen storage capacity of 7.3 wt.%. However, the practical deployment of this cycle is fundamentally restricted by sluggish kinetics during deep hydrogenation, the high endothermicity of dehydrogenation, and phase transition challenges under ambient conditions. This review critically assesses the current state of catalyst and engineering development for the naphthalene and decalin platform. Specifically, it systematically synthesizes four core mechanistic pathways governing catalytic performance, including H₂ activation and dissociation, PAH adsorption and activation, H₂ spillover and subsurface hydrogen transport, alongside comprehensive evaluations of both hydrogenation and dehydrogenation catalysts. The core discussion links empirical catalytic performance to physical and chemical descriptors, examining how active site dispersion, electronic structure regulation, support microenvironment engineering, and bimetallic synergy dictate the activity, selectivity, and stability of noble and low-cost base metal systems. Furthermore, the review addresses the physical handling of reaction intermediates through current engineering strategies. By synthesizing these catalytic mechanisms, engineering strategies, and future perspectives, this review establishes a concrete, data-driven baseline for scaling up the naphthalene-decalin system toward practical industrial implementation.