Optimization of bamboo derived bio-char production as a precursor for generation of energy storage activated carbon

Abstract

The need for energy storage systems is increasing with industrialization and population growth globally. This calls for the need to explore sustainable sources of activated carbons (AC) for energy storage purposes. This research study proposed bamboo as a possible source of microporous activated carbon. The carbonization and activation process of generating activated carbon from bamboo were optimized with the aid of response surface methodology (RSM). Char yield, ash content and fixed carbon were employed as the responses during carbonization optimization with temperature, heating rate, and holding time as controls. Similarly, temperature, holding time, steam flow were employed as controls with responses of carbon content and methylene blue number during activation process optimization. Fourier transformation Infrared (FTIR), thermogravimetric analysis (TGA), scanning electronic microscopy (SEM), cyclic voltammetry (CV) and galvanostatic charging and discharging (GCD) electrochemical methods were used to characterize raw bamboo, char and derived AC. Quadratic models were found to best fit the responses of bio-char yield, ash content and fixed carbon during carbonization optimization. Optimum conditions were predicted to be; temperature (400 oC), heating rate (10 oCmin-1), and holding time (45min) with predicted responses of char yield (34.6%), ash content (8.9%) and fixed carbon content (65.9%). For the activation process, optimum conditions were predicted as temperature (840.4 oC), holding time (104.4 min), steam flow (0.25 ml/min) and responses for carbon content and methylene blue number as 80.29% and 542.04 mg/g, respectively. The optimization of the activation process resulted in conditions that yielded activated carbon with high carbon content and a significant methylene blue number of 79.95% and 541.2 mg/g, respectively. The developed AC demonstrated a highest specific capacitance of 143 F/g at a current density of 0.5 A/g, a specific energy of 19.86 Wh/kg, and a specific power of 250 W/kg with a coulombic efficiency of 98.62%. These electrochemical properties of bamboo-derived AC are comparable to those of other biomass-derived carbon electrodes with specific capacitance and specific energy typically ranging from 20 to 150 F/g and 5 to 20 Wh/kg, respectively. Therefore, bamboo can be used as a sustainable precursor for generating AC for energy storage applications.