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

Abstract

This study\ndeals with hierarchical porous carbons from bacterial cellulose (BC),\nhaving a layered structure for high-performance application, such\nas supercapacitor electrodes, fabricated from a composite monolith\nwith unique microscopic/macroscopic morphology. A poly­(methyl methacrylate)\n(PMMA)/BC composite monolith was first synthesized by thermally induced\nphase separation using ethanol and deionized water as solvents, where\nBC acts as the main carbon source as well as matrix and PMMA acts\nas the activator source producing the necessary activation material.\nScanning electron microscopy analysis showed that a monolithic skeleton\nof PMMA was loaded uniformly on the nanofibers of BC to form a three-dimensional\nentangled structure of the PMMA skeleton and BC nanofibers, as observed\nin the microscopic view. Furthermore, the macroscopic two-dimensional\nlayered structure of BC remained in the as-obtained composite. The\nspecific surface area, structural features, and thermal stability\nwere investigated by Brunauer–Emmett–Teller, X-ray diffraction,\nand thermogravimetric analysis studies. The resulting PMMA/BC composite\nwas carbonized and activated by KOH at 850 °C. The electrochemical\nproperties were characterized by cyclic voltammetry, galvanostatic\ncharge–discharge, and electrochemical impedance spectroscopy\nshowing that the carbonization product of the composite displayed\na high specific capacitance of 266 F g^–1 at a current\ndensity of 0.50 A g^–1 and the energy density reached\na maximum of 23.6 W h kg^–1 at a power density of\n200 W kg^–1. Moreover, 95% of the capacitance was\nretained after 10,000 charge–discharge cycles, which implies\nexceptionally high cyclic stability. This compatible and excellent\nelectrochemical performance of the composite, in terms of the energy\ndensity and capacitance retention, can be contributed to the characteristic\nporous structure of the precursor composite monolith. The present\nresearch delineates a new approach to fabricate high-performance supercapacitor\nmaterials and low-cost energy storage devices from inexpensive bioresources.