Ion screening in carbon nanotubes - a Density Functional Theory study.

FERNANDA JUAREZ; LEILA MOHAMMADZADEH; ALEKSEJ GODULJAN; PAOLA QUAINO; ELIZABETH SANTOS; WOLFGANG SCHMICKLER

Sheffield

Encuentro; Carbon in Electrochemistry; 2014

Royal Society of Chemistry

Electrical double layer supercapacitors have recently attracted many attention due to their extraordinary capability for energy storage and power delivery. Since the capacity is proportional to surface area, porous carbons are good candidates for this purpose. Among the different kinds of carbon based material, carbon nanotubes (CNTs) are good choices due to their unique properties such as considerable surface area, good stability, and high mechanical properties. Recently, it has been shown that when potential between ions is screened by image force, the ion-ion interactions are reduced and the material allows a denser packing of ions. In this work we have studied alkaline atoms placed inside of finite (8,0) and (10,0) CNTs, using DFT formalism. The calculations have been done by DACAPO code. We have described the interaction between the nanotubes and the ions by means of: 1) the energetics of the insertion of the ion in the nanotubes, 2) the redistribution of the electronic charge due to the appearance of an image charge in the tube, and 3) the screened potential of the ions. The results have been compared with (6,6) gold nanotube that has almost the same diameter than (8,0) CNT, finding that gold screened better the potential than carbon. We have also concluded that the screening properties of the nanotubes depend on the nanotube diameter.