Influence of carboxymethyl cellulose content on structures and electrochemical behaviors of reduced graphene oxide films

Abstract

Film-like charge-storage devices have attracted considerable attention owing to the emergence of flexible, bendable and wearable devices. Reduced graphene oxide (rGO), which is similar to graphene, is a promising deformable electrode for charge storage. However, film-like rGO has a densely stacked structure and poor wettability to the electrolyte, which are challenging issues. In this study, carboxymethyl cellulose/graphene oxide (CG) films with different amounts of carboxymethyl cellulose (CMC) were prepared. CMC, which is a derivative of cellulose and a water-soluble polymer, functioned as an activation agent. The CG films were converted into reduced CG (rCG), which had enhanced electrochemical properties because of the increase in the accessible areas to the electrolyte ions and the pseudocapacitance due to the thermal reduction process. The CG films possessed bending property and were retained after reduction. However, the bending property decreased after reduction when the CMC was added in excess. The thickness of the rCG films increased as vacancies were formed between stacked rGO layers, and basic oxygen functional groups capable of electrochemically performing a Faradaic redox reaction were created by CMC activation. The areal specific capacitance of the rCG films increased by a factor of 30 compared with the rGO film before cycling. With increasing charging/discharging cycles, the specific capacitance of the rCG films drastically increased owing to synergistic effects of electro-activation and pseudocapacitance.