Commercial Dry Batteries: Graphite Recycling and Its Application as Counter Electrodes in a Photovoltaic System.

Dye-sensitized solar cells (DSSCs) 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 was to develop a counter electrode for a DSSC using graphite extracted from exhausted dry batteries. TiO₂ was used as the system anode, with natural dye extracted from Beta vulgaris var. esculenta (beetroot) and an electrolyte containing a redox pair of I₃⁻/3I⁻. The graphite used as counter electrodes was extracted from three different dry batteries. The cells were assembled in sandwich format with an active area of 0.2 cm². The characterization techniques used included UV–visible spectroscopy, scanning electron microscopy, x-ray fluorescence, open-circuit potential photo-chronoamperometry curves, and electrochemical impedance spectroscopy measurement. The results showed that the counter electrodes had an undefined morphology and contained small amounts of metals Mn, Fe, Ni, Zn, Pb, Ti, and Zr. The electrochemical measurements showed that the devices were photosensitive and that among the counter electrodes applied, the one that showed the most significant results in terms of photoconversion efficiency (PCE) was produced with graphite extracted from Sample 2, with J (mA cm⁻²) = 0.078 ± 0.010 and PCE = 0.016 ± 0.001%. Sample 2, using cellulose acetate (CLA) to provide better uniformity of counter electrodes, improved the dye solar efficiency, with current density (J) of 0.16 mA cm⁻² ± 0.02. [ABSTRACT FROM AUTHOR]