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.

Highlights• Sustainable carbon materials from pine cone biomass.• Hydrothermal treatment of the pine cone to produce hydrochar.• KOH activation and carbonization of the hydrochar to produce porous carbons.• Symmetric supercapacitor based on the porous carbon exhibit good electrochemical performance. Graphical abstract ABSTRACTLow-cost biomass-derived activated porous carbon from natural pine cones is synthesized using hydrothermal approach followed by KOH activation and carbonization. The produced carbon materials have a high surface area of 1515 m 2 g -1 with a well-developed 2 meso/micropores structure which is advantageous and favorable for mass transfer and ion accommodation for fast rate performance by providing pathways for electrolyte permeation and contact probability. Symmetric device fabricated using the obtained carbon material as electrode, exhibited good electrochemical performance with no degradation of capacitance after voltage holding at 1 V for about 60 h demonstrating good rate capability of the fabricated device. The results demonstrate the exciting potential of the pine cone derived carbons as a promising candidate for high-performance electrode materials for supercapacitors if fully explored.

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