Hybrid layer-by-layer composites based on a conducting polyelectrolyte and Fe3O4 nanostructures grafted onto graphene for supercapacitor application

Abstract

Using the layer-by-layer process, we developed a new and original ternary hybrid material based on magnetite iron oxide raspberry nanostructures, 250–300 nm in size, synthesized directly on few layer graphene (Fe₃O₄@FLG) alternated with conducting poly(3,4-ethylenedioxy thiophene):poly(styrene sulfonate) (PEDOT:PSS) as the electrode material for supercapacitors. Magnetite based nanostructures were used as electroactive materials. Graphene and PEDOT:PSS ensured the electrical conductivity. PEDOT:PSS also plays the role of a binder conferring cohesion to the hybrid material. Using spin-coating, the step-by-step buildup leads to very regular and well controlled film properties such as the film thickness and the content of iron oxide. The electrochemical properties of the so-obtained hybrid material were investigated in 0.5 M Na₂SO₃ aqueous electrolyte by cyclic voltammetry, electrochemical impedance spectroscopy and chronopotentiometry. In contradiction with the reported poor capacitance and poor cycling stability of iron oxide based supercapacitors, hybrid Fe₃O₄@FLG/PEDOT:PSS multilayers provide a high specific capacitance (153 F g⁻¹ at 0.1 A g⁻¹) and a high structural and cycling stability (114% retention after 3500 cycles). This hybrid developed system opens the route for even higher specific capacitance using other types of metal oxides.