Efficient aqueous processing and utilization of high-quality graphene for high performance supercapacitor electrode

High quality graphene (HQG) offers unconventional properties and is desirable for a variety of applications. However, facile solution processing (especially in water) and chemical bonding of functional components with the aim of achieving high-yield, green, and controllable synthesis of advanced graphene materials are of great concern. Herein, the surface chemistry of HQG is effectively tailored using a hydrophobic-driven assembly of cellulose macromolecules (CM) with various functionalities. In contrast to bulk or nanocellulose modifiers, surface engineering of HQG with densely carboxyl grafted CM renders stable aqueous graphene colloids via electrostatic repulsion. It also enables the use of efficient, low-cost, aqueous-phase synthetic techniques to create new HQG-based materials and devices. Highly exposed and reactive carboxyl and hydroxyl groups lead to in situ formation of evenly distributed Co₃O₄ nanoparticles on HQG sheets (HQG-COOH-Co₃O₄). We further demonstrate the potential application of two-dimensional HQG-COOH-Co₃O₄ heterostructures as supercapacitor electrodes with high power and energy density.