Highly scalable and environment-friendly conversion of low-grade coal to activated carbon for use as electrode material in symmetric supercapacitor

Blending of Activated Low-Grade Coal Powder with Coconut Shell Waste for Supercapacitor Applications

“…Thus, the single ACs are amorphous according to the qualitative XRD analysis and have low inorganic impurities as found by their chemical analysis. On the other hand, the mixed-blend AC has a graphite-like structure, indicating the conducting character of the electrode material according to XRD analysis, which is suitable for supercapacitor cell performance. ,,, …”

“…The XRD result is also verified further by the Raman spectroscopic analysis of both single and mixed-blend ACs (Figure b). While there is no detectable D band in coconut shell-based AC because of its amorphous structure, there is a weak G band at about 1636 cm –1 , indicating the existence of numerous oxygen-containing surface functional groups. , On the other hand, coal-derived AC and mixed-blend AC have two discrete peaks at approximately 1342 and 1350 cm –1 (D band) and 1612 and 1620 cm –1 (G band), respectively. The G band is typically connected to a graphite crystal lattice (sp 2 C/CC), while the D band is generally networked to a turbostratic framework (sp 3 C/C–C). ,, …”

“…The absorption peaks at 1378 cm –1 (JCA), 1368 cm –1 (CSA), and 1380 cm –1 (CJA15) are attributed to CH 3 bending mode. Also, the peaks at 1120 cm –1 (JCA), 1127 cm –1 (CSA), and 1103 cm –1 (CJA15) are assigned to carboxylic (C–OH) stretching vibration. ,,− The absorption peaks at 731 cm –1 (JCA), 732 cm –1 (CSA), and 729 cm –1 (CJA15) are attributed to C–H bending mode. In general, alkali activation has the ability to form functional groups with oxygen (−OH and −C–OH).…”

“…Ultrasonication-aided H 2 O 2 oxidation followed by subsequent thermochemical activation with the KOH method was used to synthesize the ACs from subbituminous coal samples. The detailed synthesis technique of ACs from low-grade coal was reported in our previous study . Because of the low-sulfur content in the coconut shell, the oxidation step was avoided during the synthesis of ACs from coconut shell waste.…”

“…The calculation of specific capacitance ( C Sp ) of the AC electrode from GCD is given below (eq ): ,− C = 4 × I × normald t m × normald v where I is the discharging current (amperes), d v is the potential window (volts) between the two points on the discharging curve, and d t is the time difference between the two points on the discharging curve (seconds). The ESR value of the supercapacitor cell was calculated using the Nyquist plot from PEIS analysis.…”