Electropolymerization of Polypyrrole by Bipolar Electrochemistry in an Ionic Liquid

Bipolar electrochemistry has been recently explored for the modification of conducting micro- and nanoobjects with various surface layers. So far, it has been assumed that such processes should be carried out in low-conductivity electrolytes in order to be efficient. We report here the first bipolar electrochemistry experiment carried out in an ionic liquid, which by definition shows a relatively high conductivity. Pyrrole has been electropolymerized on a bipolar electrode, either in ionic liquid or in acetonitrile. The resulting polymer films were characterized by scanning electron microscopy and by contact profilometry. We demonstrate that the films obtained in an ionic liquid are thinner and smoother than the films synthesized in acetonitrile. Furthermore, a well-defined band of polypyrrole can be obtained in ionic liquid, in contrast to acetonitrile for which the polypyrrole film is present on the whole anodic part of the bipolar electrode

Aprotic Li–O₂ Battery: Influence of Complexing Agents on Oxygen Reduction in an Aprotic Solvent

Several problems arise at the O₂ (positive) electrode in the Li-air battery, including solvent/electrode decomposition and electrode passivation by insulating Li₂O₂. Progress partially depends on exploring the basic electrochemistry of O₂ reduction. Here we describe the effect of complexing-cations on the electrochemical reduction of O₂ in DMSO in the presence and absence of a Li salt. The solubility of alkaline peroxides in DMSO is enhanced by the complexing-cations, consistent with their strong interaction with reduced O₂. The complexing-cations also increase the rate of the 1-electron O₂ reduction to O₂^•– by up to six-fold (<i>k</i>° = 2.4 ×10^–3 to 1.5 × 10^–2 cm s^–1) whether or not Li⁺ ions are present. In the absence of Li⁺, the complexing-cations also promote the reduction of O₂^•– to O₂^2–. In the presence of Li⁺ and complexing-cations, and despite the interaction of the reduced O₂ with the latter, SERS confirms that the product is still Li₂O₂