Synthesis of graphene-like porous carbon from biomass for electrochemical energy storage applications

Graphene-like porous carbon (GLC) was synthesized from walnut shell (WSh) by carbonization and thermochemical activation process. The obtained samples of graphene-like porous carbon based on walnut shell (GLC-WSh) were characterized by physicochemical analysis in order to optimize the synthesis process. The optimum condition of GLC-WSh synthesis was determined to meet the basic requirements for various applications such as an active material for supercapacitors, lithium-ion battery, as energy-intensive additives in order to increase the efficiency of high-energy rocket fuels, and as a membrane for desalination of seawater. The Raman spectra confirmed the presence of few-layer graphene in GLC-WSh with on average number of 5–7 graphene layers. The specific surface area (SSA) was determined using nitrogen adsorption/desorption analysis. The SSA is 2800 m2 g−1 according to Brunauer-Emmett-Teller method. The mass yield of GLC-WSh from the initial mass of the WSh was 21%. The synthesized GLC-WSh powder was applied as an active material for an electrochemical double layer capacitor. Electrochemical characterization showed a high specific capacitance value of 263 F/ g and columbic efficiency of 99.4% at a gravimetric current density of 1000 mA/ g.