The environmental degradation and hazard to human life caused by the depletion of fossils fuels and the urgent need for sustainable energy sources to meet the rising demand in energy has led to the exploration of novel materials that are environmentally friendly, low cost and less hazardous to human life for energy storage application using the green chemistry approach.Herein, we report on the transformation of the readily abundant pine cone biomass into porous carbon via KOH activation and carbonization at 800 °C as electrode materials supercapacitor.The porous carbon material exhibited a mesoporous framework with a specific surface area of

Activated carbon from tree bark (ACB) has been synthesized by a facile and environmentally friendly activation and carbonization process at different temperatures (600, 700, and 800 °C) using potassium hydroxide (KOH) pellets as an activation agent with different mass loading. The physicochemical and microstructural characteristics of the as-obtained material revealed interconnected micro/mesoporous architecture with increasing trend in specific surface area (SSA) as carbonization temperatures rises. The SSA values of up to 1018 m 2 g -1 and a high pore volume of 0.67 cm 3 g -1 were obtained. The potential of the ACB material as suitable supercapacitor electrode was investigated in both a three and two electrode configuration in different neutral aqueous electrolytes. The electrodes exhibited EDLC behaviour in all electrolytes with the Na 2 SO 4 electrolyte working reversibly in both the negative (-0.80 V to -0.20 V) and positive (0.0 V to 0.6 V) operating potentials. A specific capacitance (C S ) of up to 191 F g -1 at a current density of 1 A g -1 was obtained for the optimized ACB electrode material in 1 M Na 2 SO 4 electrolyte. A symmetric device fabricated exhibited specific C S of 114 F g -1 at 0.3 A g -1 and excellent stability with a coulombic efficiency of a 100% after 5000 constant charge-discharge cycles at 5.0 A g -1 and a low capacitance loss for a floating time of 70 h.

The construction and design of novel porous carbons for electric double-layer capacitors (EDLCs) application to meet the increasing demand and supply of energy is eminent. This is important because the pore volume (PV)/micropore volume (MV) in the porous network architecture of the carbon is mostly responsible for the ion traps in energy storage. Three dimensional carbon materials based on graphene materials with relatively high specific surface area (SSA) represents a promising material candidate for EDLCs applications. In this work, we synthesized highly porous carbon from graphene foam (GF) and polyvinyl alcohol PVA as a sacrificial template, and investigate their performance as electrodes for EDLCs applications. The as-produced carbons present a fairly large surface area (502 m 2 g -1 ), and a highly porous interconnected framework with mesopore walls and micropore texture which are suitable as electrode for energy storage. As electrode material in a symmetric configuration the activated graphene foam (AGF) showed a specific capacitance of 65 F g -1 , energy density of 12 Wh kg -1 , power density of 0.4 kW kg -1 , good rate performance and excellent long term stability in 1 M Na 2 SO 4 aqueous with no capacitance loss after 3000cycles.

In this work, we present the synthesis of low cost carbon nanosheets derived from expanded graphite dispersed in Polyvinylpyrrolidone, subsequently activated in KOH and finally .This electrical double layer capacitor electrode also exhibits excellent stability after floating test for 120 h in 6 M KOH aqueous electrolyte. These results suggest that this activated expanded graphite (AEG) material has great potential for high performance electrode in energy storage applications.

In this study, porous activated carbons (AC) were synthesized by an environmentally friendly technique involving chemical activation and carbonization, with an in-depth experimental study carried out to understand the electrochemical behaviour in different aqueous electrolytes (KOH, LiCl, and Na 2 SO 4 ). The electrochemical performance of the AC electrode was evaluated by different techniques such as cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy. The results obtained demonstrate that the AC materials in different electrolytes exhibit unique double layer properties. In particular, the AC electrode tested in 6 M KOH showed the best electrochemical performance in terms of specific capacitance and efficiency. A specific capacitance of 129 F g À1 was obtained at 0.5 A g À1 with a corresponding solution resistance of 0.66 U in an operating voltage window of 0.8 V, with an efficiency of $100% at different current densities.