Characteristic dual-domain composite structure of reduced graphene oxide and its application to higher specific capacitance

In this article, characteristic dual-domain structures of rGO layers, to be applied to fascinating electrode materials for energy storage systems, such as supercapacitors, are reported. Conductive atomic force microscopy (C-AFM) technique reveals that the rGO surface consists of a dual-domain structure of graphene and GO components, which provide simultaneous electric-electrolyte pathways to the electrode, and that the amount, configuration, and connectivity of both domains are depend on the reduction level of rGO. The rGO sheet having a finely connected and well-balanced dual-domain composite structure provided higher specific capacitance compared to others. Using a concept of triple-phase boundary (TPB) where three phases, i.e., pseudo-type ceramic particle and the dual-domains coincide, hybrid composite sheets of Fe₂O₃@rGO and MnO₂@rGO were also fabricated and examined for further enhancing specific capacitance. Besides, the reduction mechanism of the rGO layer by hydrazine to develop such dual-domain structures and the formation behavior of freestanding rGO sheets from rGO suspension were discussed in this study.