Production of biomass-derived graphitic carbon and its utilization as electrode material for supercapacitor
Project no. 28457 · Status: Kapanmış (Yayın bekleniyor) · 2023
Summary
<p>While a majority of energy is derived from fossil fuels, the depletion of these resources and their contribution to environmental pollution have increased the need for renewable energy sources. Therefore, the development of low-cost and high-performance energy storage devices and systems from renewable sources has become a significant focus of interest for backup power sources, portable electronic devices, and electric vehicles.</p><p>This thesis aims to synthesize porous graphitic carbons from food waste-derived hydrochars for use as electrode materials in supercapacitors. Firstly, hydrochars were obtained from different food wastes (orange peel, aflatoxin-containing dried grapes, and dried figs) via hydrothermal carbonization (HTC) method. Mass yields of hydrochars obtained from dried grapes were found to be between 11% and 42%, which significantly varied with HTC duration and temperature. At a HTC temperature of 200°C, increasing the duration from 1 to 6 hours led to an increase in mass yield from 11.2% to 42.5% due to the formation of secondary char. Considering the mass yield, hydrochar obtained from dried grapes under HTK conditions at 200°C for 6 hours was used for graphitic porous carbons (GPC) production. Hydrochar was impregnated with different mass ratios of FeCl3, K2CO3, and FeCl3-K2CO3 mixtures to obtain graphitic porous carbon (GPC) through activation at different temperatures. In binary activator systems, higher the FeCl3 ratio resulted in a decrease in surface area, while increasing the K2CO3 ratio improved surface porosity. The highest surface area was found in GPC with hydrochar:FeCl3:K2CO3 ratio of 1:2:2 activation at 900 °C (1104,65 m2/g) whereas microporous strucure was maximized with GPC produced with K2CO3 alone activation at 800 °C. Electrochemical performance was investigated by the cyclic voltammetry method. The electrochemical capacitance performance of GPC was determined using 1M EMIMBF4 (1-ethyl-3-methylimidazolium tetrafluoroborate) ionic liquid. Voltammograms (current-voltage curves) were generated at scan speeds ranging from 50 mV/s to 200 mV/s, with a potential window spanning -1.2 V to 0 V (relative to the Ag/AgCl reference). Supercapacitor cells developed of GPC obtained at 700 ºC with a hydrochar:FeCl3:K2CO3 ratio of 1:2:2 demonstrated best performance, with a specific capacitance of 120 F/g at a scan rate of 10 mV/s in a 1M EMIMBF4 aqueous environment.</p>