2D nano materials and their hybrids as supercapacitor electrodes for energy storage applications

Abstract

Two dimensional (2-D) nanomaterials have drawn considerable attention to the evolution of supercapacitor electrodes for high performance flexible energy storage device applications due to their high electro-active sites, high specific surface area, macro mechanical flexibility, wellbehaved electrical properties etc. The thesis entitled “2-D Nano Materials and their Hybrids as Supercapacitor Electrodes for Energy Storage Applications” encompasses a detail report on the development of some 2-D nanomaterials through different synthesis routes and their applications in supercapacitor energy storage. More precisely, this dissertation highlights the successful synthesis of some 2-D transition metal oxides (TMOs) like MoO3, MnO2, RuO2, metal dichalcogenides (MoS2), BiOCl nanoplates, vanadyl phosphate (VOPO4) and their composites with graphene, single and multi-wall carbon nanotubes (SWCNT, MWCNT) etc. and their applications as supercapacitor energy storage devices. The prepared samples have been thoroughly characterized by FESEM, TEM, XRD, XPS, AFM BET, Raman and etc. In this work, a facile large scale production of TMOs nanosheets by exfoliation in ethanol-water mixed solvent instead of using highly toxic organic solvents has been demonstrated. After optimization, this method gives high concentration (0.42 mg/ml, 0.47 mg/ml and 0.40 mg/ml for MoO3, MnO2 and RuO2 respectively) stable dispersion of TMOs nanosheets. Thin flexible solid state supercapacitors based on SWCNT /TMOs nanosheets composites showing a large specific capacitance and high energy density. In addition, a planner supercapacitor based on SWCNT/MnO2 shows an improved electrochemical performance with excellent stability under different bending condition. Thin flexible films of BiOCl/MWCNT composites have been prepared with varying the weight percentage. Among various compositions, 60% BiOCl loaded electrodes delivers superior electrochemical performance. Instead of gold we have used SWCNT network as a current collector which will be helpful to make transparent flexible supercapacitor with high energy density for future application BiVO4/rGO hybrid nanostructure based symmetric supercapacitor exhibits better performance in solid electrolyte. MoS2/rGO hybrids thin film supercapacitor and MWCNT/VOPO4 hybrid supercapacitor are also deliver improved energy storage performance.