Using a mixture of vinasse-contaminant and H₃PO₄ as an efficient electrolyte for high performance flexible carbon nanotube-based supercapacitors

The elimination of vinasse contaminant generated by the tequila industry and other alcoholic beverages is of current interest because millions of liters are produced every year and it cannot be released in the environment due to its low pH and high content of organic material. As an effort to reuse/recycle such a contaminant, we report the use of a mixture of vinasse-contaminant + H₃PO₄ as the electrolyte for flexible supercapacitors (SCs), which are made with carbon nanotube (CNT) electrodes. We obtained a high capacitance value of 679.7 F g⁻¹ in the devices made with both electrodes of CNTs. When the Ag/TiO₂ nanoparticles are added in the SC anode, the capacitance is enhanced to 1852.8 F g⁻¹, which is among the highest values reported so far for flexible CNT based SCs. We also compared the performance of the SC made with vinasse to another made with a conventional electrolyte of PVA/H₃PO₄ and found that the capacitance and energy density values of this last device were 1.2 times lower. All the devices made with CNTs, Ag/TiO₂ and vinasse + H₃PO₄ stored charge by redox reactions and the redox centers were: oxygen vacancies, carboxylic groups, Ag⁰/Ag²⁺ and Ti³⁺/Ti⁴⁺ ions. Thus, the vinasse contaminant is a feasible electrolyte for supercapacitors. (paper)