| Abstrakt: |
Using the methods of quantum-chemical modeling, the influence of unsaturated dibasic organic acids on the thermodynamic characteristics of the one-electron oxidation reaction of Mn2+ acidoacquacomplexes, which determine the basic level of energy efficiency of the electrochemical synthesis of MnO2, was investigated. It is shown that the monodentate anionic forms of maleic (HM-) and fumaric (HF-) acids do not have any advantages over the anions of monocarboxylic acids, in particular, acetate ions. On the contrary, the formation of hydrogen bonds with intraspherical water molecules by the second carboxyl group, which is not bound to the central atom, significantly impairs the effectiveness of the influence of HM- and HF- anions on the stage of electron extraction from the complexes [Mn2+(L)(H2O)5]. The value of the standard redox potential E0 (Mn2+/Mn3+) of ionic systems with single-charged anions of maleic and fumaric acids is 1.05 V and 0.99 V, respectively, which is much higher than E0 (Mn2+/Mn3+) of acetate complexes (0.66 V), currently recommended for practical use. The presence in the internal coordination sphere of Mn2+ acid-acid complexes of bidentate-bonded double-charged maleic acid anion reduces E0 (Mn2+/Mn3+) to 0.32 V, which is twice less than in acetate electrolyte. The prospects of maleate electrolytes are also enhanced by the ability of unsaturated anions M2- to catalyze the disproportionation stage of Mn3+ complexes. [ABSTRACT FROM AUTHOR] |
