Electrochemical characterization of chemical vapor deposition grown few-layer graphene*

The intrinsic double-layer capacitance (C$_{\mathrm{dl}})$ of graphene is an important fundamental parameter that has important implications in nano-carbon based energy storage devices. We used cyclic voltammetry to measure the C$_{\mathrm{dl}}$ of few-layer graphene (FLG) samples. Considering the fact that the specific C$_{\mathrm{dl}}$ of graphitic edge planes exceeds that of basal planes by an order of magnitude, the measured specific C$_{\mathrm{dl}}$ may be used to evaluate the relative area fraction of edge planes to that of basal planes. In our case, the specific C$_{\mathrm{dl}}$ of FLG grown on Ni foils was found to be $\sim$2-4 $\mu $F/cm$^{2}$, which is typical of basal plane capacitance, and indicating predominant basal plane coverage in our CVD process. Such samples are amenable to further physical/chemical modifications to create controlled defects which are expected to further enhance C$_{\mathrm{dl}}$. Electrochemical characterization of such ideal geometry in tandem with defects engineering can provide insights into the contribution of graphitic edge planes to charge storage in high surface area carbon electrodes.