Preparation And Eelectrochemical Performances Of Moringa Oleifera Based Porous Carbon Materials

Owing to the increasingly prominent global environmental problems and the consumption of limited fossil fuels,the rational use of renewable resources,the development of new energy storage and conversion devices have become a hot topic in the world.Renewable biomass has been widely used and studied because of their wide range of sources,low prices,abundant resources,easy collection,renewable and fast growth.In recent years,employing biomass as a precursor to prepare the porous carbon material has been more and more attention.Biomass-based porous materials with high specific surface area and special pore structure,is a good supercapacitor electric double layer capacitor material.The moringa oleifera,as a fast growing,widely distributed planting,possesses a special biological structure,its various products have been developed and applied to many areas.In this paper,different parts of moringa oleifera were selected as the carbon precursor to prepare the uniquely structural porous carbon material by one-step method,which revealed excellent supercapacitor performances.The concrete synthesized process as following:?1?Preparation and electrochemical properties of hierarchically interconnected egg-box-like carbon materials:the special microtubule bundle structure of Moringa oleifera was selected as carbon precursor to synthesize three-dimensional heteroatom-doped and hierarchical egg-box-like carbons?HEBLCs?by a facile one-step pyrolysis and activation process.The as-prepared HEBLCs possesses unique egg-box-like frameworks,high surface area?2312 m/g?,interconnected porosity,as well as doping of hetero-atoms?oxygen and nitrogen?,endowing excellent electrochemical performances?such as high capacitance,high rate capability,and outstanding cycling stability?.Electrochemical results show that HEBLC-2 has a high specific capacity?355 F/g?,excellent rates performance.Furthermore,the as-assembled HEBLC//HEBLC symmetric supercapacitor displays a superior energy density of 20 Wh/kg in aqueous electrolyte.?2?Preparation and electrochemical properties of hierarchically porous carbon nanosheets:Porous carbon nanosheets?PCNSs?were successfully prepared by using one-step graphitization and activation method using Moringa oleifera stems as raw material.As the electrode material for the supercapacitor,the PCNSs exhibit a maximum specific capacitance of ca.283 F/g?0.5 A/g?,excellent rate capability?ca.72%of capacitance retention even at an ultrahigh current density of 50 A/g?,and a tremendous long-term cycling stability in the three-electrode system.Moreover,the as-assembled PCNS-based symmetric supercapacitor shows a high energy density of ca.25.8 Wh/kg?in 1.0 M Na₂SO₄ electrolyte?and remarkable long-term cycling stability?almost no capacitance fade in aqueous electrolytes?,indicating the promising of the as-prepared PCNSs for electrochemical energy storage and conversion.?3?The preparation and electrochemical properties of the crumpled porous carbon:using the Moringa oleifera leaves with special biological structure and mineral composition as the carbon precursor,the crumpled porous carbon were synthesized by one-step carbonization method.The as-obtained carbon material possesses the high surface area and unique structure with surface folds.As the electrode material of the supercapacitor,the as-prepared carbon materials shows a high specific capacitance of273 F/g,a prominent structural stability?no significant attenuation?after 20 000 fast charge/discharge cycles at 6.0 M KOH electrolyte of three-electrode system.