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. (C) 2019 Elsevier Inc. All rights reserved.