Supercapacitors based on carbon nanomaterials
are attracting much
attention because of their high capacitance enabled by large specific
surface area. The introduction of heteroatoms such as N or O enhances
the specific capacitance of these materials. However, the mechanisms
that lead to the increase in the specific capacitance are not yet
well-studied. In this Letter, we demonstrate an effective method for
modification of the surface of carbon nanowalls (CNWs) using DC plasma
in atmospheres of O2, N2, and their mixture.
Processing in the plasma leads to the incorporation of ∼4 atom
% nitrogen and ∼10 atom % oxygen atoms. Electrochemical measurements
reveal that CNWs functionalized with oxygen groups are characterized
by higher capacitance. The specific capacitance for samples with oxygen
reaches 8.9 F cm–3 at a scan rate of 20 mV s–1. In contrast, the nitrogen-doped samples demonstrate
a specific capacitance of 4.4 F cm–3 at the same
scan rate. The mechanism of heteroatom incorporation into the carbon
lattice is explained using density functional theory calculations.
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