Cameron Kepert - Chemistry

Storing Hydrogen: the energy of the future

In theory hydrogen appears to be the ideal energy carrier. Its energy density is more than three times that of fossil fuels, its chemical energy may be converted to electrical energy in a highly efficient way, and upon combustion it produces only water. However, if the proposed hydrogen economy is ever to exist, the industry needs to find a safe and efficient way to store hydrogen.

Professor Kepert is working towards a solution based on the use of nanoporous coordination framework materials. Owing to their lowdensity molecular structure, these materials have unprecedented surface areas on which hydrogen can be stored.

Currently, the approach is limited by the weakness of the interaction between the hydrogen gas molecule and the material’s surface – though storage can be forced at very low temperatures and high pressures.

By maximising the energy of interaction, hydrogen loading can be achieved at less extreme temperatures and pressures. Kepert has discovered very high hydrogen uptakes in Prussian Blue materials and a range of highly porous metal-organic frameworks (MOFs). One advantage of MOFs is that they can be rationally designed and synthesised with specific properties.

A recent Kepert paper in the Journal of the American Chemical Society provided the first definitive evidence that H2 can bind to open metal coordination sites in nanoporous MOFs. Kepert’s team used neutron powder diffraction to determine the location of D2 (an isotope of H2) within a framework material containing bare copper sites.

The results showed that open metal sites can interact directly with an intact hydrogen molecule, favouring loading under non-extreme conditions and leading to more efficient packing of hydrogen in the pores. It was the first time this special type of interaction has been identified in a framework material.