Photothermally-Activated Suspended Biphase Reaction System Towards High-Efficiency and Additive-Free Hydrogen Generation at Ultrahigh Storage Density

Abstract

The need for a sustainable hydrogen supply has sparked significant efforts to develop effective liquid hydrogen carriers with high hydrogen content, safe storage, low-cost transportation, and controlled hydrogen release. However, a major challenge lies in the ultralow hydrogen evolution rate caused by the direct dehydrogenation of liquid hydrogen carriers. Conventionally, additives or solvents as the accelerant are employed to improve the dehydrogenation rate, but this strategy inevitably sacrifices its hydrogen storage density. Therefore, achieving both high-efficiency hydrogen release and high storage density remains a daunting task. Herein, we developed an innovative photothermally-activated suspended biphase system based on a porous Pd/rGO aerogel, which absorbs solar radiation and re-radiates infrared photons to induce the photothermal evaporation and in-situ gaseous dehydrogenation of liquid hydrogen carriers, fundamentally circumventing the employment of additives and solvents. Furthermore, by leveraging this phase transition-induced biphase reaction design, the system significantly improves photothermal reaction temperature and drastically lowers the hydrogen transport resistance by nearly two orders of magnitude. As a result, an impressive hydrogen evolution rate of 386 mmol/g/h has been achieved from pure formic acid with the ultrahigh hydrogen storage density of 44 g/L, representing a threefold improvement compared to state-of-the-art systems. Our approach introduces a fresh perspective for the dehydrogenation of liquid hydrogen carriers, encompassing formic acid, hydrazine hydrate, sodium borohydride, and so on, concurrently guaranteeing exceptional hydrogen release capabilities and superior hydrogen storage density.

Keywords: liquid hydrogen carriers, suspended biphase system, hydrogen storage density, hydrogen evolution rate