Sustainable Conversion of Agro-Waste into Ordered SBA-16 Mesoporous Silica for Advanced Supercapacitor Electrodes

Abstract

The use of agro-waste valorization is a way to develop functional porous materials containing silica and to mitigate the problems of disposal and commercial silica sources. In this paper, a sustainable route to synthesize ordered SBA-16 mesoporous silica using the wheat husk ash (WHA) is proposed, and it is then combined with conductive carbon phase to form porous composite electrode for aqueous supercapacitors. WHA is acid-treated, calcined and converted into soluble sodium silicate and then self-assembled into spherical shapes using surfactant-directed self-assembly process under acid conditions. The proposed hydrothermal treatment variable is the most important one, since it affects the condensation of the framework and the development of the pores as well as the structural ordering. The mesostructure and chemical purity are confirmed by low angle XRD, wide angle XRD, FTIR, Raman spectroscopy, SEM, TEM/HRTEM, EDX, TGA and N2 adsorption-desorption, and the electrode behaviour is evaluated by cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy and cycling tests. The illustrative planning data indicates that the BET area ranges from 318 to 461 m2/g while the apparent composite-electrode capacitance ranges from 58 to 96 F/g with increased hydrothermal time of 12 to 48 h. The numerical values given here are only provisional and should be replaced by measured data before submitting. The key concept of the central materials is that the SBA-16 provides a three dimensional ordered network of mesopores as well as an electrolyte-accessible surface, while the conductive carbon phase provides electronic transport.