Specific capacitance of graphene oxide–metal interfaces at different deoxygenation levels

Abstract

The experimental data available on the electrical features of graphene oxide/metal (GO/M) interfaces appear sporadic and inconsistent. Here, we fuse the findings from nanostructural and electrical characterization studies on various M/GO/M structures at different GO deoxygenation levels and conclude for the first time that the impedance of an M/GO/M structure is mainly determined by the GO/M interface and strongly depends on the nature of M. Based on our results, GO/M interfaces are categorized into two distinct types: A-types, including GO/Au and GO/Pt, depict a specific capacitance of 0.1 mF cm⁻², while B-types, including GO/Cu, GO/Al, and GO/Zn, present SCs in the 10 nF cm⁻² range. It is established for the first time that capacitances of the A-types are intrinsically related to the interface, while the growth of nanostructured metal oxides/hydroxides at the B-type interfaces controls their capacitances. The oxygen content of the interface-grown mass is considerably more than the total oxygen on the deposited GO. Hence, the growth mechanism is linked to the dissociation of water in the nano-reactors formed at these interfaces. A case study experimentally designates 10 μF cm⁻² to GO/Ti interfaces, regardless of its electrochemical similarities to the B-types. This observation is described based on the unique properties of interface-grown Ti-rich oxide layers. Understanding the redox reactions taking place in the nano-reactors formed at GO/M interfaces can lead to novel electronic and electrochemical applications. Our findings are anticipated to initiate research on the electrical properties of GO interfaces with other metals.