Estudos físico-químicos e desenvolvimento de baterias de inserção de prótons

Abstract

In this work it was prepared two different Prussian Blue analog materials – the copper hexacyanoferrate(II) - CuHCF - and the vanadyl hexacyanoferrate(II) - VOHCF. These materials were characterized by physical-chemical techniques and by electrochemical methods in order to evaluate its the energy storage capability from aqueous proton insertion reactions. The obtained results indicate that both compounds can operate on proton insertion/deinsertion reactions with good energy capacities. The CuHCF, by using H2SO4 4 mol.L-1 electrolyte yields a reversible specific capacity of 70 mA.h.g-1 at C/2 rate and 40 mA.h.g-1 at 120C rate. In addition, the VOHCF with H2SO4 6 mol.L-1 electrolyte results an energy capacity of 120 mAh∙g-1 at C/2 rate and 40 mAh∙g-1 at 120 C. These results indicate that such compounds can operate at extremely high charge/discharge rate with good energy capacities. Cyclic voltammetry experiments where used to study the charge transfer process indicating that such events are occurring via surface-adsorbed species. Galvanostatic intermittent titration technique (GITT) was used to study kinetic and thermodynamic properties by measuring diffusion coefficients and the involved diffusion activation energies. The findings indicate that such insertion/deinsertion reactions are related to the presence of coordinated water inside the insterticials sites and that the ionic transport is directed by the vehicular mechanism, where hydronium ions (H3O+) are the diffusing species. These results confirm that such studied systems are a promising technology for the development of a new class of rechargeable batteries – the hydronium batteries – energy devices with low-cost, safe, and with good energy-density and extremely high power-density. These energy features are particularly interesting for application on energy storage of renewable power plants or energy backup systems.