4.1 │ Materials
MCF was supplied as an aqueous colloidal suspension (2 wt%, Exilva) was acquired from Borregaard (Norway). LiCl, SnO2 (average particle size of 1 µm), dimethylformamide (DMF, >99.9%), potassium hydroxide (KOH, >99.5%), tin oxide (99%), and dimethylacetamide (DMAc,>99.9%) were obtained from Sigma Aldrich. All the chemicals were used as received without any further purification. Distilled water was utilized throughout the experiment.
│Fabrication of MFC thin films
LiCl solution with a concentration of 10 wt% was first prepared by stirring LiCl in DMAc at 80 °C. After cooling to room temperature, 1 wt% of MCF was then dispersed in DMAc for 30 min under stirring. Later, MFC suspension was mixed with 10 wt% of LiCl/DMAc for 30 minutes. This mixture was then vacuum filtrated using Whatman filter paper and MFC thin films was dried overnight in oven at 60°C.
│ Preparation of hybrid tin oxide-cellulose nanocomposites
2 wt% of MFC was diluted into 0.2 wt% of MFC suspension using DMF under stirring for 4 h at ambient temperature 16. Different SnO2 loadings (4, 8, 12 wt%) were dispersed in DMF separately and sonicated for 3 h before mixing with MFC suspension (0.2 wt%) and stirred for another 1 h at 60 °C. Then, SnO2-MFC mixtures were hydrothermally treated at 120°C. Dark brown slurries were produced after 4 h.
│ Preparation and characterization of tin oxide-cellulose thin films
MFC thin films were dip-coated with SnO2 -MFC nanocomposite slurries for 1 h. The coated thin films were dried in an oven at 80 °C overnight to form flexible supercapacitors. After drying, they were rinsed with distilled water and dried at 200 °C for 2 h. These thin films were denoted as MFC-4SnO2, MFC-8SnO2, MFC-12SnO2, respectively. The surface morphology of these thin films was study using scanning electron microscopy (SEM, TM3000 Hitachi, Japan), while their chemical properties was studied using X-ray diffraction (XRD, Bruker Advanced X-ray Solution D8, Cu Kα radiation, l = 0.154 nm) and Fourier transform infrared spectroscopy (FTIR, Nicolet iS10, Thermo Scientific, USA). The electrochemical properties such cas yclic voltammetry (CV) and cyclic stability were studied using µStat 300 BiPotentiostat electrochemical workstation with the three-electrode system using 1 M of KOH solution as the electrolyte solution. The electrochemical impedance spectroscopy (EIS) data was collected using Metrohm Autolab potentiostat electrochemical workstation.