Hydrogen Hydrate Promoters for Gas Storage—A Review

Clathrate and semi-clathrate hydrates have recently been gaining major interest as hydrogen storage material. The benefits of hydrates, such as reversible formation and dissociation, their environmentally friendly nature, economical costs, and lower fire risk, make them one of the most promising hydrogen storage materials. One of the major challenges when storing hydrogen in hydrate crystals is the extreme pressure and temperature conditions required for the formation of hydrogen hydrates. Solving the problems of extreme pressure and temperature through the use of promoter molecules would make these materials a promising storage medium with high potential. Through the use of efficient, economical, and green promoter molecules, hydrogen hydrate can be used to store large amounts of hydrogen economically and safely. This review aims to present a comprehensive summary of the different hydrate promoters that have been tested specifically in terms of hydrogen storage. The hydrate promoters are classed according to the structure of the hydrate crystals they form, i.e., sI, sII, sH, and semi-clathrate hydrate. This review article provides summarized information for readers about the different promoters tested and their benefits and shortcomings.