One-step green synthesis of meso-microporous carbons by self-activation of lemon wastes for high-performance supercapacitors

Abstract

A green self-activating system is introduced for the synthesis of porous carbons. This system is introduced to overcome the environmental concerns regarding the harmful by-products of the conventional synthesis approaches. The introduced system is based on the circulating active gases, released during the carbonization treatments at T ≤ 500 °C. These active gases are stored in the system and participate in the activation process at T ≥ 700 °C. During the activation process, there is no exhaust gas and any need for a protective atmosphere. Lemon wastes were pyrolyzed in this system at several temperatures (400 to 900 °C). It is demonstrated that the introduced system is applicable for the synthesis of turbostratic carbons with relatively high graphitization levels. Pyrolyzation at T ≥ 800 °C can appropriately activate the lemon biomass. The prepared meso-microporous carbon has a large specific surface area of up to 2111 m2.g−1 and a pore volume of 1.28 cm3.g−1 can be obtained after pyrolyzation at 900 °C. Meso-microporous carbon are applied as an electrode for supercapacitors. The prepared supercapacitor performs an electric double layer with minor pseudo-capacitance behavior. The supercapacitor illustrates the capacitance of 254 F.g−1 at 10 A.g−1 and excellent stability of 92 % retention after 30,000 cycles.