Abstract
Capacitive energy storage mechanisms in nanoporous carbon supercapacitors hinge
on endohedral interactions in carbon materials with macro-, meso-, and micropores
that have negative surface curvature. In this article, we show that because of the
positive curvature found in zero-dimensional carbon onions or one-dimensional
carbon nanotube arrays, exohedral interactions cause the normalized capacitance to
increase with decreasing particle size or tube diameter, in sharp contrast to the
behavior of nanoporous carbon materials. This finding is in good agreement with the
trend of recent experimental data. Our analysis suggests that electrical energy storage
can be improved by exploiting the highly curved surfaces of carbon nanotube arrays
with diameters on the order of 1 nm.
