A graphene-based electrical nano-device has been created which could substantially increase the energy efficiency of fossil fuel-powered cars.

The nano-device, known as a 'ballistic rectifier', is able to convert heat which would otherwise be wasted from the car exhaust and engine body into a useable electrical current.

Parts of car exhausts can reach temperatures of 600 degrees Celsius. The recovered can then be used to power additional automotive features such as air conditioning and power steering, or be stored in the car battery.

The nano-rectifier was built by a team at The University of Manchester led by Professor Aimin Song and Dr. Ernie Hill, with a team at Shandong University. The device utilises graphene's phenomenally high electron mobility, a property which determines how fast an electron can travel in a material and how fast electronic devices can operate.

The resulting device is the most sensitive room-temperature rectifier ever made. Conventional devices with similar conversion efficiencies require cryogenically low temperatures.

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