Multilayered bacterial cellulose/reduced graphene oxide composite films for self-standing and binder-free electrode application.

Multilayered bacterial cellulose (MBC)/reduced graphene oxide (rGO) composite films were fabricated using dyeing method. First, MBC films were constructed by the static culturing of kombucha SCOBY bacterial cellulose in a rectangular plastic mold for 15 days. The MBC formed on the air-liquid interface was collected and employed as the matrix for the preparation of MBC/rGO composite films using dyeing method. As found, the color strength increased with an increase in dyeing cycle due to MBC and GO (rGO precursor) affinity. However, the surface hydrophilicity was found in the opposite direction due to the restacking of hydrophobic rGO nanosheets onto MBC surface after reduction step. SEM images confirmed that MBC/rGO composite films obtained by the dyeing method exhibited the intact multilayer structure. The electrochemical behavior of free-standing and binder-free MBC/rGO electrodes was evaluated. It was found that MBC-1 exhibited the highest specific capacitance value of 192.23 F/g at the current density of 1 A/g (calculated from GCD plots) due to good diffusion of electrolyte arising from surface wettability with current density performance of 66 %. An increase in dyeing cycle (MBC-2, MBC-3, and MBC-4) led to a gradual decrease in the corresponding specific capacitance value due to a gradual increase in the electrolyte resistance derived from an increasing surface hydrophobicity of the composite films. Finally, in all cases, long-term cycle stability of more than 90 % up to 10000 cycles was achievable.