Solidified Hydrogen Storage (Solid-HyStore) via Clathrate Hydrates

• A comprehensive review on hydrate based hydrogen (H 2 ) storage is presented. • State of the art for various H 2 -containing hydrate systems are evaluated. • Multiple cage occupancy by H 2 and the tuning effect are discussed systematically. • Challenges, limitations, and future directions for the technology are outlined. • Solid-HyStore technology is recommended for stationary storage of hydrogen. With non-renewable fossil fuels depleting rapidly, hydrogen as a clean energy source producing no pollutants or greenhouse gas emissions upon combustion is bound to play a leading role in the future energy landscape. Among the pertinent challenges in establishing a hydrogen-based economy is developing an energy dense hydrogen storage technology with easy recovery of the stored gas. Clathrate hydrates enabling the innovative solidified storage of hydrogen molecules at moderate temperature and pressure conditions carve a niche for safe, long-term, stationary hydrogen storage. This review focuses on the current state of the art for solidified hydrogen storage (Solid-HyStore) via clathrate hydrates. The properties and performances of various H 2 -containing hydrate systems are evaluated and summarized comprehensively. Multiple cage occupancy by H 2 molecules and the tuning effect as the controversial issues in hydrogen hydrate research are elucidated. Finally, the challenges, limitations, and future opportunities for hydrate-based hydrogen storage are identified.