Title: Synthesis of graphene based materials for energy storage: Optimization of Tour’s method, first part

Abstract

Many attempts have been made to apply graphene in scientific areas due to its interesting properties. Graphene synthesis methods could be categorized into two basic types: bottom up or top-down. The methods for obtaining graphene materials by chemical synthesis are included in the top-down methods, which have two important advantages: low cost, nontoxic procedure that are easily to apply for a large-scale graphene production. Within these syntheses, three-dimensional graphene structures, called hydrogels, that presents some relevant properties such as: high specific surface area, low density, high pore volume and acoustic insulation, may be appropriate to be applied into energy storage purposes. Hydrothermal synthesis is a simple method to obtain hydrogels starting from graphene oxide (GO), which consists of forming a three dimensional structure of reduced graphene oxide (rGO) from an aqueous solution of GO. The complete synthetic route consists of oxidizing graphite to obtain graphite oxide which is, in turn, exfoliated to give rise to graphene oxide. The latterwill be the starting material to carry out the hydrothermal synthesis of hydrogels. These hydrogels must provide the following characteristics to be implemented in energy storage applications: a) High specific surface area (SSA), b) Large porosity made up of mesopores or micropores. c) High electric conductivity. In this study, the aim is to optimize the initial step of the synthesis, the oxidation of graphite to graphite oxide. For this purpose, Tour´s method has been employed since that this method leads to water groups intercalated between graphite sheets. This gives rise to larger specific surface areas than those obtained with Hummers´ method, the most commonly used method. The different variables influencing the process: temperature, time and H2O2 and KMNO4concentrations have been optimized by applying an experimental design and all the materials obtained have been characterized by X-ray diffraction (XRD), analysis by Brunauer Emmett-Teller (BET) method, Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and elemental analysis (EA).

Biography

Hanna Bukovska is developing her doctoral thesis at the Chemistry Area of the Research Center for Energy, Environment and Energy (CIEMAT). She studied bachelor's degree in chemistry at the Complutense University of Madrid and later did her master's degree in Materials Processing Technologies at the Rey Juan Carlos University. She is currently researching on the synthesis of graphene hydrogels for applications in water decontamination, supercapacitors and hydrogen storage.