Pilhas secas comerciais: reciclagem do grafite e sua aplicação como contra eletrodo em células solares sensibilizadas por corante

Abstract

Using renewable energy resources to reduce the emission of polluting gases is a viable alternative for a sustainable future. Among the renewable energy sources discussed in this paper is solar energy. The sun is a clean source of energy and the radiation it emits can be converted into electricity. The search for efficient use of this radiation has been growing in recent decades, and one field of study is the use of the photovoltaic effect. Dye-sensitized solar cells (DSSC) belong to the third generation of solar cells and are promising photovoltaic devices for energy conversion. They are composed of a semiconductor oxide, a photosensitive dye, an electrolyte and a counter electrode, in which platinum is generally used. In order to reduce production costs, alternative materials such as graphite can be used as a counter electrode. The aim of this work is to develop a counter electrode for a DSSC, using graphite extracted from exhausted dry batteries. TiO2 was used as the system's anode, with natural dye extracted from Beta Vulgaris Esculenta (beetroot) and an electrolyte containing a redox pair of I3-/3I-. The graphite used as counter electrodes was extracted from three different brand batteries, brand 1 (P1), 2 (P2) and 3 (P3), macerated and coated on a conductive FTO substrate. The cells were assembled in an anode and cathode sandwich format with an active area of 0.2 cm2. The characterization techniques performed were: UV-Visible region Spectroscopy, Scanning Electron Microscopy, X-ray fluorescence, Open Circuit Potential, Photochronoamperometry and j-V curves. The results have showed that the counter electrodes had an undefined morphology and that they presented small amounts of metals such as Mn, Fe, Ni, Zn, Pb, Ti and Zr. The electrochemical measurements showed that the devices were photosensitive and among the counter electrodes used, the one that showed the most significant results in terms of photoconversion efficiency was produced with graphite extracted from the Brand 2 (P2) battery, with photovoltaic parameters of j (mA cm-2) =0.078±0.016; V (V)=0.558±0,032; FF=0.367±0.074; ƞ (%) = 1.616x10-2 ± 0.005.