  Due to the shorter channel length allowing faster ion/charge movement,
nanoscale molecular thin films can be attractive electronic components for
next-generation high-performing energy storage devices. However, controlling
chemical functionalization and achieving stable electrode-molecule interfaces
at the nanoscale via covalent functionalization for low-voltage operational,
ultrafast charging/discharging remains a challenge. Herein, we present a
simple, controllable, scalable, low-cost, and versatile electrochemical
grafting approach to modulate chemical and electronic properties of graphite
rods (GRs) that are extracted from low-cost EVEREADY cells (1.5 US $ for 10
cells of 1.5 V). On the ANT-modified GR (ANT/GR), the total capacitance unveils
350-fold enhancement as compared to an unmodified GR tested with 0.1 M H2SO4
electrolyte ensured by both potentiostatic and galvanostatic measurements. Such
enhancement in capacitance is attributed to the contribution from the
electrical double layer and Faradaic charge transfer. Due to higher
conductivity, anthracene molecular layers possess more azo groups (-N=N-) over
pyrene, and naphthalene molecular films during the electrochemical grafting,
which is key to capacitance improvements. The ultra-low-loading nanofilms
expose high surface area leading to extremely high energy density. The
nanoscale molecular films (~ 23 nm thickness) show exceptional galvanostatic
charge-discharge cycling stability (10,000) that operates at low potential.
Electrochemical impedance spectroscopy was performed along with the DC
measurements to unravel in-depth charge storage performances. Electrochemically
grafted molecular films on GR show excellent balance in capacitance and
electrical conductivity, high diffusion coefficient toward ferrocene, and can
easily be synthesized in good yield on rigid to flexible electrodes.
