Electrodeposition and electrochemical charging of hybrid organic/inorganic films composed of the poly(3,4-ethylenedioxythiophene), PEDOT, conducting polymer matrix, and Keggin type polyoxometallate, phosphododecamolybdate <mml:math display="inline"><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mi mathvariant="normal">PMo</mml:mi><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:msub><mml:msubsup><mml:mo>O</mml:mo><mml:mrow><mml:mn>40</mml:mn></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>−</mml:mo></mml:mrow></mml:msubsup><mml:mo stretchy="false">)</mml:mo></mml:math>(PMo12O403−) or phosphododecatungstate <mml:math display="inline"><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mo>PW</mml:mo><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:msub><mml:msubsup><mml:mo>O</mml:mo><mml:mrow><mml:mn>40</mml:mn></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>−</mml:mo></mml:mrow></mml:msubsup><mml:mo stretchy="false">)</mml:mo><mml:mo>,</mml:mo></mml:math>(PW12O403−), redox centers, are described under conditions of aqueous solutions. The systems are electropolymerized through potential cycling as thin and moderately thick (μm level) films on electrode surfaces. They are capable of fast charge propagation during redox reactions in strong acid medium (0.5 mol dm⁻³ <mml:math display="inline"><mml:msub><mml:mo>H</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mo>SO</mml:mo><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub><mml:mo stretchy="false">)</mml:mo><mml:mo>.</mml:mo></mml:math>H2SO4). The high overall physicochemical stability of PEDOT is explored to produce a robust, conductive, matrix for such polynuclear mixed-valence inorganic nanostructures as <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">PMo</mml:mi><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:msub><mml:msubsup><mml:mo>O</mml:mo><mml:mrow><mml:mn>40</mml:mn></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>−</mml:mo></mml:mrow></mml:msubsup></mml:math>PMo12O403− and <mml:math display="inline"><mml:msub><mml:mo>PW</mml:mo><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:msub><mml:msubsup><mml:mo>O</mml:mo><mml:mrow><mml:mn>40</mml:mn></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>−</mml:mo></mml:mrow></mml:msubsup><mml:mo>.</mml:mo></mml:math>PW12O403−. The composite (hybrid) materials are stabilized due to the existence of electrostatic attraction between anionic phosphomolybdate or phosphotungstate units and positively charged conducting polymer (oxidized). Charge transport is facilitated by the fact that the reversible and fast redox reactions of polyoxometallate appear in the potential range where PEDOT is conductive. The effective diffusion coefficients are on the level <mml:math display="inline"><mml:mn>4</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mrow><mml:mn>10</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>8</mml:mn></mml:mrow></mml:msup></mml:math>4×10−8 cm² s⁻¹. The whole concept may lead to the fabrication of composite (hybrid) films that are capable of effective accumulation and propagation of charge in redox capacitors. © 2005 The Electrochemical Society. All rights reserved.

Robust, polyaniline-based, multilayer composite films containing Prussian blue and hexacyanoferrate anions are considered here for the protection of stainless steel (SS) against pitting corrosion in strongly acid media. Polyaniline serves as a stable host matrix for large inorganic anions. At the interface formed by a composite film with SS, the interaction of <mml:math display="inline"><mml:mi mathvariant="normal">hexacyanoferrate</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mo>II</mml:mo><mml:mo>,</mml:mo><mml:mo>III</mml:mo><mml:msup><mml:mo stretchy="false">)</mml:mo><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup></mml:math>hexacyanoferrate(II,III)− with iron(II,III), and some chromium(III), results in the formation of a thin insoluble metal hexacyanoferrate (mostly Prussian blue) layer. This phenomenon leads to improved passivation of the steel, and it strongly inhibits metal dissolution even in the chloride acid media. Because the metal hexacyanoferrate deposits are electronically conducting, further electropolymerization of dense and adherent composite polyaniline layers with hexacyanoferrate has been readily achieved. Due to the existence of electrostatic repulsion between negatively charged hexacyanoferrate sites and pitting-causing chloride anions, their transport through the composite film and access to the surface of SS are largely blocked. © 2003 The Electrochemical Society. All rights reserved.