SOLUTION REDOX COUPLES FOR ELECTROCHEMICAL ENERGY STORAGE AND PHOTOELECTROCHEMICAL CELLS

Some of the properties of solution redox couples in aqueous solution were investigated to obtain guidelines for designing and selecting redox couples for electrochemical energy storage (redox flow battery) or photoelectrochemical cells. Several first row transition metal ions (Fe, Co, Cu, V, Cr) and their complexes were probed. O-phenanthroline and related ligands were employed to complex iron, cobalt, and copper ions. Macrocyclic and noncyclic pentadentate complexes of iron and copper ions were also studied.; Some aspects of solution chemistry, such as dissociation rate, complexation rate, air sensitivity, and the stoichiometry of the complex ions were investigated. Measurements of heterogeneous electron transfer rates, mass transfer rates, stability, standard potential and solubility of the complex ions were carried out.; Cobalt(III)/(II) complexes of o-phenanthroline and related ligands, some iron(III)/iron(II) complexes of macrocyclic and noncyclic pentadentate ligands, copper(II)/(I) in HCl, vanadium(III)/(II) in HCl, and iron(III)/(II) in H(,2)SO(,4) showed properties consistent with application in redox flow batteries and photoelectrochemical cells. Vanadium(III)/(II) in HCl, iron(III)/(II) in H(,2)SO(,4) or HCl, and cobalt(III)/(II) complexes of o-phenanthroline and related ligands were tested in a dual photoelectrochemical cell.