Tuning the Surface Chemical State of Graphene Oxide Sheets for the Self‐Assembly of Graphene Hydrogel for Capacitive Energy Storage

Abstract

Three-dimensional graphene materials have greatly expanded the market space of graphene, but their economical fabrication remains a challenge. Herein, we report a facile and low-cost method for the preparation of high-performance graphene hydrogels by adding ammonium-modified graphene oxide into low-dielectric constant organic solvents. By forming ammonium salts or through a re-protonation process, the graphene sheets are assembled together by electrostatic attraction or hydrogen bonding interactions, along with π-π interactions. The unique structure-aligned few-layer graphene sheets, abundant surface functional groups and multifarious pores-enables prepared hydrogels with both superior charge storage capability (207.6 F g À 1 at 1 A g À 1 ) and excellent high-rate performance (83.2 % capacitance retention when the discharge current density is increased from 0.5 to 10 A g À 1 ). In this study, we present some achievements in capacitive energy storage but, while they are encouraging, graphene-based materials prepared by this feasible and efficient route can also be applied to other advanced applications likenew-generation rechargeable batteries, sensors, biomedical engineering, and water purification.

Recent Progress in Mechanically Robust and Conductive‐Hydrogel‐Based Sensors

“…The conductive network comprises conductive fillers or polymers formed by in situ polymerization, while hydrogels act as stretchable and deformable matrices. [49,71] Common electronic conductive materials include metal (e.g., gold, silver, and copper) NPs/nanowires, [72][73][74] carbon-based materials (e.g., carbon NPs/carbon nanowires, graphene, and graphene oxide [GO]), [75,76] and conductive polymers (e.g., polyaniline [PANI], polypyrrole [PPy], poly(3,4-ethylene dioxythiophene):polystyrene sulfonate [PEDOT:PSS]). [77][78][79] Introducing electronic conductive materials provides conductivity to hydrogels and improves their tensile and mechanical properties.…”