Pseudocapacitors from crumpled graphene balls/mixed transition metal oxides composites

Restacking of graphene is one of the issues which compromises the properties of this carbon nanostrucuture and decrease their solution processability. Changing the 2D structure of graphene into a 3D structure simply crumpling it like a paper ball is a clever solution to keep this material with high accessible surface area and resistant to aggregation.[1] The charging storage properties of raw crumpled graphene and composites with metal oxides is beginning to be explored since this metals precursors present excellent pseudocapacitive response.[2] Mixed transition metal oxides is an option to enhance the pseudocapacitive properties of this class of charge storage materials since they exhibit higher electron conductivity.[3] Herein, we show a new approach to obtain composites made of crumpled graphene balls and mixed transition metal oxides in one single step. Graphene oxide was obtained by a modified Hummer’s method; and crumpled graphene balls and mixed transition metal oxides composites were synthesized nebulizing a graphene oxide/metal precursors (iron and manganese) dispersion into a tubular furnace.[1] The scanning electron microscope (SEM) micrograph in Figure 1 shows the crumpled graphene ball decorated by the metallic species. The cyclic voltammetry measurements presented a quasi-rectangular shape, which is typical for pseudocapacitive materials, but charge-discharge measurements presented low value of specific capacitance (around 30 F/g). Different graphene oxide/metal precursors ratios will be explored to enhance the capacitive properties of the composite.