Synergetic Combination of Carbon Xerogels, Graphene Oxide and nano-ZnO for Aqueous and Organic Supercapacitors

Abstract

Three-dimensional carbon xerogels were synthesised via a facile approach that included the use of ZnO nanostructures both as a templating agent and as a catalyst for resorcinol–formaldehyde resin (R−F) polymerisation simultaneously. Graphene oxide (GO) served as a stabilising agent during the drying and pyrolysis processes, avoiding the collapse of structure and improving the area surface. The method enabled the as-obtained materials to possess optimised 3D porous structures for energy-storage devices, such as wires or spaghetti-like structures. Also, a high BET surface area was obtained (1661 m² g⁻¹) without using an additional activating agent. This great surface area improved the specific capacitance compared to materials without GO (358.1 F g⁻¹ vs 170.4 F g⁻¹). The carbon-containing devices derived from resorcinol-formaldehyde resin, GO, and Zn oxide showed better performance than the devices without GO. In particular, the sample that contained 2.5 % of GO in the synthesis showed a specific capacitance of 166.6 F g⁻¹ at 0.5 A g⁻¹ and remained at ∼120 F g⁻¹ at 5 A g⁻¹ current density. Also, it showed interesting energy density values at 0.5 A g⁻¹ (14.8 Wh kg⁻¹) and a power density of 200.7 W kg⁻¹. This reveals that the synthesis process made it possible to obtain composite materials with large surface areas without using a supercritical drying process. The materials can be used in supercapacitor-type devices with high performance in aqueous electrolytes.