|Calculated structure for|
[Rh6(PH3)6H14]+. Click to enlarge.
Different mechanisms for storing hydrogen using metal lattices are under development, but metal hydrides only work at temperatures above 300° C and metal organic framework materials only work at liquid nitrogen temperatures (-198°C).
Scientists at the University of Bath (UK) have developed a material which stores and releases hydrogen at room temperature, at the flick of a switch. Although its gravimetric hydrogen storage density is insufficient to make an entire hydrogen tank from it, the material could be used in combination with metal hydride sources to store and release energy instantaneously while the main tank reaches sufficient temperature, 300°C, to work.
They hope to have the fully-working prototype ready within two to three years.
Our new material works at room temperature and at atmospheric pressure at the flick of a switch. Because it is made from a heavy metal (Rhodium), its weight to fuel ratio is low, 0.1 per cent, but it could certainly fill the time lag between a driver putting their foot on the accelerator and a metal hydride fuel tank getting up to temperature.
The new material absorbs the hydrogen into its structure and literally bristles with molecules of the gas. At the flick of a switch it rejects the hydrogen, allowing us to turn the supply of the gas on and off as we wish.
The fact that we discovered the material by chance is a fantastic advertisement for the benefits of curiosity driven research.—Dr Andrew Weller, from the Department of Chemistry at the University of Bath
The University of Bath researchers made the discovery while investigating the effect that hydrogen has on metals. Having constructed an organo-metallic compound containing six rhodium atoms and 12 hydrogen atoms, they began studying the chemical properties of the complex with researchers in Oxford (UK) and Victoria (Canada).
The material absorbs two molecules of hydrogen at room temperature and atmospheric pressure and releases the molecules when a small electric current is applied to the material.
The researchers are now looking at ways of printing the material onto sheets that could be stacked together and encased to form a storage tank.
Potentially this tank could sit alongside a metal hydride tank and would kick into action as soon as the driver put his or her foot on the accelerator, giving the metal hydride store the time to heat up to 300°C.
The research was initially funded by the Engineering & Physical Sciences Research Council.
The researchers are now working on the first stages of the prototype, which involves printing the material onto a glass substrate. A further £500,000 grant to the Department of Chemistry has enabled Weller along with other researchers in the Department to buy two mass spectrometers which allows them to examine the molecular structure of the material.
“Storing and Releasing Hydrogen with a Redox Switch”; Simon K. Brayshaw, Dr., Jennifer C. Green, Prof., Nilay Hazari, J. Scott McIndoe, Prof., Frank Marken, Dr., Paul R. Raithby, Prof. , Andrew S. Weller, Dr.; Angewandte Chemie International Edition, Volume 45, Issue 36 , Pages 6005 - 6008