Tuning Electrochemical Performance of Graphenated Carbon Nanotubes Through Atomic Layer Deposition of TiO ₂

In this work, nanocomposites of graphenated carbon nanotubes (g‐CNTs) conformally coated with TiO 2 by atomic layer deposition (ALD) were produced. g‐CNT forests were grown on silicon substrates by microwave plasma–enhanced chemical vapor deposition (915 MHz), and the density of graphene foliates was tuned by adjusting the growth time at 1050°C. TiO 2 thickness was controlled via the number of ALD cycles. The resulting electrodes comprise aligned, high‐aspect‐ratio nanotube arrays whose average diameter varies with the foliate thickness and the TiO 2 cycle number. Electrochemical impedance spectroscopy and cyclic voltammetry show that the TiO 2 coating improves cyclic stability and increases specific capacitance relative to pristine g‐CNTs. This enhancement arises from the synergy between the high conductivity and electric double‐layer capacitance of g‐CNTs and the Faradaic pseudocapacitance of TiO 2 . Finally, we identify a trade‐off between foliate density and TiO 2 thickness that defines a tunable parameter space for optimizing g‐CNT/TiO 2 electrodes.