Electrochemical formation of ion-conducting oxo-phosphate-molybdate polymer on aluminium

Abstract

The state of the electrochemical behaviour of the Al electrode in aqueous solutions containing Na2MoO4 + H3PO4 + chitosan was investigated by methods of currentless chronopotentiometry, chronoamperometry, optical and scanning electron microscopy. The modification of the surface polymolybdate phosphate layers was carried out in a potentiostatic mode in the potentials range from ?1 to ?3 V and polarization time (from 15 to 90 min). The elemental composition of the surface layer of the metal before and after cathodic polarization were investigated. The electrochemical formation of matrix polymeric structures from ion-conducting (H+, Na+) heteronuclear polymolybdate and polyphosphate-molybdate complexes of double salts Na6AlnMo7-nO24 and Na2yAl2(MoO4)y(PO4)3-y was established. The rate of hydrogen and sodium intercalation into the structure of the polyoxophosphate-molybdate layer increased sharply with an increase of the potential range from ?1.3 to ?3.0 V. The addition of chitosan into the solution enhances the film-forming effect of surface ion-conducting oxo-phosphate ? molybdate polymeric layer.