Great step forward for capability to store gas to power cars of the future
Tuesday 2 October 2012
A major breakthrough has been made by engineers trying to ensure that hydrogen- or methane-powered cars will be able to store enough gas to make them a viable option as the future main source of transport across the world.
There has been a tremendous effort in the scientific world for developing new materials to store hydrogen or methane as onboard fuel for future’s cleaner vehicles. In the past few years a new class of crystalline and microporous materials known as "metal organic frameworks" (MOFs) have shown great promise.
If the internal surface area of one gram of one of these record breaking MOFs could be unfolded it would occupy the area of equivalent to the Emirates Stadium, where Arsenal plays its games in the Premier League.
In these materials metal atoms are connected by organic linker molecules. This results in a network of molecular cages with vast internal surface areas ideal for storing gases. The higher the surface area, the larger the amount of hydrogen or methane that can be stored, and the longer the car can go.
Until now the way the gas has been stored using metal organic frameworks (MOFs) has had a theoretical finite limit so making the idea impractical but now scientists have come up with a way to vastly improve this capacity.
Dr Ozgur Yazaydin from Department of Chemical Engineering at University of Surrey and his collaborators at Northwestern University in US have demonstrated that it is possible to achieve higher surface areas in MOF materials, about 40% higher than previous studies had suggested.
The team has produced two new MOF materials with the highest internal surface area per gram – so therefore gas storage capacity – ever recorded.
“The key is exposing more surface per available space for gas molecules to stick” says Dr Yazaydin who led the theoretical part of the study. “Benzene molecules, which are commonly used in MOFs as organic linkers, are like hexagonal rings, and gas molecules can only stick onto the ring’s outer surface, thus the inner sides of each benzene unit is essentially wasted space. If you break the ring and straighten it then both sides become available for gas adsorption. That is exactly what we did”.
He added: “The breakthrough heralds a whole new dimension to the potential for using gas to power vehicles.
The study was published in the September 12, 2012 issue of the Journal of the American Chemical Society.