Polyaniline–Graphene Hydrogel Hybrids via Diffusion Controlled Surface Polymerization for High Performance Supercapacitors

The intricate design of nanomaterials through the controlled diffusion process is natural for biological bodies; however, understanding this mechanism for the development of morphology tuned nanomaterials in the practical chemical synthesis process is still lacking. Herein, we present the development of graphene hydrogel via ultrafast assembly and employed it as a diffusion controlled confined reactor for the growth of ultrafine polyaniline nanostructure directly over its hydrogel surface (PANI–GH). The significant control over the polymerization rate is achieved by slowing the diffusion of monomers through the hydrogel–organic interface and subsequent confined polymerization within the porous compartments of graphene hydrogel. In addition, the strong attractive interaction of aniline monomer with the graphene surface plays a key role in controlling the oriented nucleation process, as revealed from the molecular dynamics study. The as-developed PANI–GH with commercial scale mass loading (8.8 mg cm–2) exhibits excellent supercapacitive performance, displaying a capacitance of 503 F g–1 and superb retention (95.8%) even after 3000 charge–discharge cycles. More importantly, it showed a very high rate capability with a capacity retention of 88.6% when the current density increased from 2 to 30 A g–1. This fundamental understanding of the hydrogel mediated interfacial reaction together with outstanding performance metrics of the as-developed material could open up a versatile platform for morphology tuned graphene based functional hybrids.