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.
