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May 01, 2014

Graphene nanoribbons proposed to make thermoelectric materials with efficiency better than gasoline engines to make solid state engines feasible

Researchers propose a hybrid nano-structuring scheme for tailoring thermal and thermoelectric transport properties of graphene nanoribbons. Geometrical structuring and isotope cluster engineering are the elements that constitute the proposed scheme. Using first-principles based force constants and Hamiltonians, we show that the thermal conductance of graphene nanoribbons can be reduced by 98.8% at room temperature and the thermoelectric figure of merit, ZT, can be as high as 3.25 at T = 800 K. The proposed scheme relies on a recently developed bottom-up fabrication method, which is proven to be feasible for synthesizing graphene nanoribbons with an atomic precision.

Thermoelectic materials convert heat to electricity.
Getting a thermoelectric figure of merit over 3.0 is a technological holy grail like a room temperature superconductor.


Nature Scientific Reports -A bottom-up route to enhance thermoelectric figures of merit in graphene nanoribbons

Currently the best materials (Tin Selenide) in the lab have a ZT of 2.6.




In summary, the combination of geometrical structuring and isotope engineering at the precursor level makes it possible to optimize both electronic and phononic transport properties of the considered carbon nanomaterials which have already been realized with existing fabrication technology. Noting that ZT over 3 is the goal for efficient thermoelectrics isotopically engineered c-GNRs are good candidates for technological applications, especially at elevated temperatures. The proposed hybrid nanostructuring scheme is promising for efficient TE energy conversion and thermal management of nano-devices. This scheme is not limited to carbon based systems but it is applicable to low-dimensional structures in general.

Thermoelectric efficiency

Thermoelectrics at ZT 3 or higher could replace current methods of refrigeration and automotive engines and turbines at power plants.
The actual range of replacement depends upon the price and volume of thermoelectric material that can be produced and the operating temperatures.






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