To supply the high power and energy demand many efforts have been made to develop efficient energy storage devices. The material and structure of the electrode are key to the supercapacitor performance including power density, energy density, rate capability, charge time and cyclic capability. Carbonaceous materials, such as graphite, graphene and amorphous carbon, have been used as supercapacitor electrode due to their unique properties. In particular, reduced graphene oxide and biomass derivatives have attracted great attention as they present high ion storage capacity, chemical stability, conductivities and large interlayer distance. Yet, carbon material-only based supercapacitor typically present low energy density and limited ionic accessibility. Instead, metal oxide supercapacitors present high specific capacitance and high power and energy density. However, the specific capacitance of those metal oxide-based supercapacitors drops considerably with an increase in the scan rate due to their poor electronic conductivity. Hence, the synthesis of composites based on oxides and carbonaceous materials is a good strategy to overcome the drawbacks of each material, combining the merits of both components. In this work we have synthesized composites with different carbon sources: biomass:TiO2 and rGO:TiO2, and their properties as supercapacitors have been investigated. We have used sugar cane biomass graphitized by hydrothermal and chemical process. The carbon structure derived from biomass has presented high surface area and porosity. The reduced graphene oxide was obtained by the modified Hummers method and functionalized with OH moieties, by reduction with LiAlH4. The composites were synthesized by the hydrothermal technique, using titanium isopropoxide in acidic and basic medium, in order to evaluate the effects accordingly with the morphology and crystalline phase of the oxides. In the composite biomass:TiO2 was observed an homogenous particle-like morphology in the acidic medium and rod-like for the basic medium. In the composite rGO:TiO2 was oberved a graphene-oriented lamellar structure. In addition, the amount of the carbon derivative in the initial synthesis was investigated in the final performance of the material. It has been observed that the oxide morphology is tuned accordingly the carbon source used. The final performance in supercapacitors have been analyzed by CV, EIS and charge and discharge curves, and the carbon:oxide ratio optimized.

Synthesis and comparison of new composites based on sugar cane biomass:TiO2 and rGO:TiO2 and performance as supercapacitors

ACS Spring Meeting 2021

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