Gram-scale Production of Holey Vertically Aligned Graphene Nanosheet Arrays Derived from Renewable Biomass Precursor by Facile Hydrothermal/Salt-assisted Pyrolysis Method for Aqueous High-performance Redox supercapacitors

Abstract

Herein, we developed a facile gram-scale production of high-quality aligned graphene nanosheet arrays (VAGNAs) method named as hydrothermal/salt-assisted pyrolysis (HSP) method for constructing high-performance redox supercapacitors. VAGNAs were fabricated on a large scale by this HSP method from low-cost, green and renewable biomass instead of fossil gas precursors, no expensive instrument or extra substrate is required. The key fabrication process parameters were screened and optimized, such as the pretreatment method, selected salts and pyrolysis temperature. The as-fabricated VAGNAs exhibit outstanding properties, including high graphitization degree, thin nanosheet and good hydrophilicity as well as developed hierarchically porous structure. The as-fabricated VAGNA was employed as electrodes to construct redox supercapacitors. The VAGNA electrodes possess an ultrahigh specific capacitance of 3184 F g-1 in the 1.0 M KOH electrolyte with the addition of 0.10 M K3Fe(CN)6. The assembled symmetrical redox supercapacitor based on VAGNA-L-1000 delivers high specific capacitance of 92.8 F g-1 at 1 A g-1 under wide operation potential window of 2.0 V, and high energy density of 52 Wh kg-1 at the power density of 999.5 W kg-1. The present study highlights the large-scale synthesis of high-value added nanocarbons derived from renewable biomass for developing high-performance supercapacitors with high energy density in an economical way. Key Words: Vertically Aligned Graphene Nanosheet Arrays; Hydrothermal/Salt-assisted Pyrolysis method; Renewable Biomass; Supercapacitor.