Electroactive organically modified mesoporous silicates on graphene oxide-graphite 3D architectures operating with electron-hopping for high rate energy storage

Abstract

Pseudo-capacitive materials operating with electron-hopping as the charge transfer mechanism are elaborated by the extensive assembly of fixed redox molecules onto the surface of graphene-supported mesoporous silica film. Various physico-chemical techniques are used to characterize the resulting composites. The obtained GO@Fc-MS electrode (ferrocene functionalized silica film coated onto electro-exfoliated graphene) can deliver a specific capacity of 196 mC cm−2 (326 mF cm−2) at a current density of 2 mA cm−2 and a 69% capacity retention even at 3800 C, which is much better than the traditional faradic materials. The electrochemical analyses reveal the energy storage behavior of GO@Fc-MS is a fast surface-controlled redox process. The electrode can be assembled into an asymmetric device which exhibits excellent cycling stability (no noticeable fading after 10 000 cycles) and competitive energy densities (respectively 17.7 or 9.2 µWh cm−2 at power densities of 0.53 or 13.7 mW cm−2). These results open up new opportunities for pseudocapacitive materials based on electroactive inorganic frameworks bearing surface-tethered molecular redox sites with high energy storage capability.