There are many arguments for and against the use of hydrogen as a fuel for vehicles. One of the biggest obstacles that has prevented the gas from becoming commonplace is storage. As a gas, hydrogen is very energy dense but requires heavy, thick-walled tanks to contain it. Liquified, its energy density plummets to a quarter of that of petrol. Scientists think the solution lies in nano-engineered sponges.
The US Department of Energy set scientists a challenge five years ago, to develop a material that could hold 6% of its own weight in hydrogen. Researchers at the University of Crete have beaten that target, coming up with a theoretical material that can hold 6.1% of its weight in the gas.
In theory, the material would consist of atom-thick carbon sheets called graphene (see photo above). These sheets would be separated by carbon nanotube pillars just 1.2-nanometers tall. The sponge would be coated, or “doped”, with positively charged lithium ions which would enhance its hold on the gas.
The sponge would be capable of storing hydrogen at normal temperature and pressure, without the need for a heavy-duty storage tank. This is a crucial factor if we hope to use hydrogen in smaller applications such as home heating, or even to power our gadgets.