Fuelling the future
Researchers at the University of Hong Kong have developed organic supramolecular crystals that significantly improve hydrogen storage performance, potentially enhancing the efficiency of fuel cell vehicles.
Hydrogen is considered a promising fuel for the future as a zero-emission fuel with high gravimetric energy density (meaning it can store more energy per unit of mass than many other fuels). This study addresses a critical challenge in hydrogen fuel technology: balancing high gravimetric and volumetric storage capacities. Volume is a major constraint in vehicle design, with hydrogen’s low volumetric density creating the need for bulky storage systems.
Organic supramolecular crystals are a promising option for hydrogen storage due to their recyclability (meaning they can be used many times), but designing such crystals with balanced high gravimetric and volumetric surface areas while maintaining stability remains challenging.
Led by Professor Fraser Stoddart and Dr Chun Tang and Dr Ruihua Zhang from Hong Kong University, the team employed a novel 'point-contact catenation strategy'. Catenation is the ability of an element to form bonds with itself, creating long chains or ring structures. This approach uses hydrogen bonds to guide catenation precisely, creating a well-organised framework that optimises pore size for hydrogen storage while maintaining structural stability.
The resulting supramolecular crystals achieved record-high gravimetric (3526 m² g⁻¹) and balanced volumetric (1855 m² cm⁻³) surface areas among reported supramolecular crystals. Under practical pressure and temperature conditions, the material demonstrated excellent volumetric capacity (53.7 g L⁻¹) and high gravimetric capacity (9.3 wt%) for hydrogen storage.
This development could contribute to the development of more efficient fuel cell vehicles with improved driving ranges.
The research was the result of a collaboration between Hong Kong University and Northwestern University. It was published in Nature Chemistry with Dr Tang, Dr Zhang and Dr Hilal Daglar from Northwestern University as the first-mentioned coauthors.