Binary microdroplets as liquid hydrogen carriers for enhanced hydrogen production

Liquid organic hydrogen carriers (LOHCs) are promising media for hydrogen storage, transport, and generation. However, their dehydrogenation in aqueous environment is severely limited by phase immiscibility, resulting in sluggish reaction kinetics. In this study, we investigated a base-catalyzed hydrogen evolution reaction using binary LOHC-alcohol microdroplets combined with a 0.5 M NaOH solution. As efficient microscopic reacting entities, the binary microdroplets at certain mixing ratios achieved up to a 8-fold increase in hydrogen production. This enhancement is particularly pronounced for the binary mixture of polymeric LOHC and a long-chain alcohol with a maximal production rate at an equal mixing ratio where both in-drop and on-drop reactions take place. By following the hydrogen bubble evolution from a single binary droplet, we uncovered a transition in hydrogen bubble formation modes, from in-drop at low mixing ratios, to clustering at intermediate ratios, and on-drop at high ratios, each correlating with distinct hydrogen production rates. Notably, the droplet-based approach achieved a high hydrogen yield in the absence of hazardous solvents or metal catalysts. The produced hydrogen is further demonstrated to power a fuel cell, showcasing its direct application in energy generation. These findings highlight the potential of tuning the composition of reactive microdroplets to unlock highly efficient hydrogen production and utilization pathways.