Sodium-embedded carbon for better energy devices

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Sodium-embedded carbon nanowalls have been synthesised by a research team at Michigan Tech, which it claims can improve battery electrodes.

High electrical conductivity and large accessible surface area are said to be required for electrode materials in energy devices, and these are opposed to each other in current materials.

"Sodium-embedded carbon's conductivity is two orders of magnitude larger than 3D graphene," Professor Yun Hang Hu says. "The nanowall structure, with all its channels and pores, also has a large accessible surface area comparable to graphene."

This is different from metal-doped carbon, where metals are simply on the surface of carbon and are easily oxidised; embedding a metal in the carbon structure helps protect it.

To make such a material, the team had to create a new process. It used a temperature-controlled reaction between sodium metal and carbon monoxide to create a black carbon powder that trapped sodium atoms.

According to the researchers, a platinum-based solar cell reaches a standard power conversion efficiency of 7.89%, which is considered standard. In the study, the solar cell using Prof Hu's sodium-embedded carbon reached efficiencies of 11.03%.

Sodium-embedded carbon is said to have an energy density of 145Farad/g and retains a 96.4% capacity after 5000 charge/discharge cycles, which indicates electrode stability.

According to Prof Hu, sodium-embedded carbon offers improvements in solar tech, batteries, fuel cells, and supercapacitors.