Electrochemical Visualization of Defect-induced Density of States at Single Graphene Flake

Abstract

The density of states (DOS) at the Fermi level plays crucial role in the property and application of graphene-based material. We introduce an electrochemical approach that allows straightforwardly probing the defect-induced DOS at single flake of chemically reduced graphene oxide (r-GO). The idea is based on the earlier belief that the non-adiabatic electron transfer (ET) reaction rate at electrode/electrolyte interface increases with the Fermi-level DOS of electrode. By investigating the voltammetric responses of defect-rich and defect-lean r-GO nanoflakes using a variety of redox probes, we observe strong correlation between the ET kinetics and the defect densities on r-GO flakes, which are tuned by varying the flake sizes and preparation procedures. Our results thus validate a few general beliefs, namely, the defects can boost the Fermi-level DOS in graphene, the ET reaction on graphene-based material is non-adiabatic, and the non-adiabatic electrochemical ET kinetics indeed increases with the DOS of electrode.