Obtenção de nonofolhas de grafite expandido (GNs) visando a incorporação em eletrólito polimérico sólido para potencial uso em células solares sensibilizadas por corante.

Abstract

One of the main disadvantages found by photovoltaic cells is related to the use of liquid electrolyte, as they may leak during sealing and operation, which ends up limiting the durability and stability of the electrolyte. However, these problems can be solved using solid or gel polymeric electrolytes, although a decrease in the open circuit potential (Voc) is observed. The addition of carbonaceous materials such as carbon nanotubes (NTC) and graphene derivatives in polymeric electrolytes is an interesting alternative to increase the efficiency of Dye -Sensitized Solar Cells (DSSCs). Thus, expanded graphite, later sectioned into nanosheets (GNs), can be added to polymeric electrolytes, due to its ability to promote electronic conduction, in addition to its catalytic properties. Therefore, the objective of this work is to present the synthesis and characterization of a solid polymeric electrolyte based on xanth an gum (XG), dissolved in deionized water, containing different concentrations of expanded graphite nanosheets (GNs), in addition to crosslinkers and plasticizers. For this, the graphite was expanded through a microwave oven at temperatures in the range of 300 - 900 °C for a period of 5 minutes and then subjected to the process of ultrasonic bath in an absolute alcohol solution, resulting in nanosheets of expanded graphite (GNs). With concentrations of 0.1; 0.3; 0.5 and 0.7% by mass of (GNs), in relation to the mass of the polymer xanthan gum (XG) and with additions of crosslinking agents and plasticizers, the synthesis of the material was carried out, which resulted of the a flexible solid polymeric electrolyte for application in DSSCs. All material used to manufacture the solid polymeric electrolyte was characterized using techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), spectroscopy in the ultraviolet-visible region (UV-Vis), cyclic voltammetry (VC) and electrochemical impedance spectroscopy (EIE). The results obtained show that xanthan gum (XG) with additions of (GNs) crosslinkers and plasticizers form a solid and flexible polymeric electrolyte that presents an ionic conductivity in the order of 10-3 S.cm-1 at room temperature. These conductivity values are higher when compared to other biodegradable electrolytes found in the literature, showing a good response for applications in DSSCs.