Hierarchical Porous Carbons from Poly(methyl methacrylate)/Bacterial Cellulose Composite Monolith for High-Performance Supercapacitor Electrodes

This study deals with hierarchical porous carbons from bacterial cellulose (BC), having a layered structure for high-performance application, such as super capacitor electrodes, fabricated from a composite monolith with unique microscopic/macroscopic morphology. A poly(methyl methacrylate) (PMMA)/BC composite monolith was first synthesized by thermally induced phase separation using ethanol and deionized water as solvents, where BC acts as the main carbon source as well as matrix and PMMA acts as the activator source producing the necessary activation material. Scanning electron microscopy analysis showed that a monolithic skeleton of PMMA was loaded uniformly on the nanofibers of BC to form a three-dimensional entangled structure of the PMMA skeleton and BC nanofibers, as observed in the microscopic view. Furthermore, the macroscopic two-dimensional layered structure of BC remained in the as-obtained composite. The specific surface area, structural features, and thermal stability were investigated by Brunauer-Emmett-Teller, X-ray diffraction, and thermogravimetric analysis studies. The resulting PMMA/BC composite was carbonized and activated by KOH at 850 degrees C. The electrochemical properties were Characterized by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy showing that the carbonization product of the composite displayed a high specific capacitance of 266 F g(-1) at a current density of 0.50 A g(-1) and the energy density reached a maximum of 23.6 W h kg(-1) at a power density of 200 W kg(-1). Moreover, 95% of the capacitance was retained after 10,000 charge-discharge cycles, which implies exceptionally high cyclic stability. This compatible and excellent electrochemical performance of the composite, in terms of the energy density and capacitance retention, can be contributed to the characteristic porous structure of the precursor composite monolith. The present research delineates a new approach to fabricate high-performance supercapacitor materials and low-cost energy storage devices from inexpensive bioresources.