A conducting polymer, poly(o‐phenylenediamine) (PoPD), has been obtained as stable film onto an electrode surface by the electropolymerization of o‐phenylenediamine in 0.1 mol dm−3 H2SO4. The film thickness did not exceed 0.85 μm because of its low electrical con‐ductivity. The virgin “doped” polymer film was soluble in dimethylsulfoxide N, N‐dimeth‐ylformamide, acetone, and tetrahydrofuran without any pretreatment. The highest solubility obtained was 17 g dm−3 in dimethylsufoxide. A cast film of PoPD on a substrate was prepared from its dimethylsulfoxide solution. The mean molecular weight of PoPD was found to be 11,000 with the gel permeation chromatography. The STM observation exhibited that the cast film was considerably uniform compared to the electrodeposited film. The cyclic voltammogram of such film showed a reversible redox property accompanied with excellent electrochromism between transparent yellow and brown. It was suggested from the 1H‐FTNMR and FTIR spectra and the elemental analysis that the polymeric backbone has 1, 4‐substituted benezenoid‐quinoid structure. © 1995 John Wiley & Sons, Inc.

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Although the electrochemical reduction of CO 2 at a copper electrode produces hydrocarbons, the activity for the conversion of CO 2 is significantly reduced after several tens of minutes by the deposition of poisoning species on the electrode. In order to solve the poisoning species problem, the electrochemical reduction of CO 2 was carried out using a copper electrode in the pulse electrolysis mode by anodic as well as cathodic polarization. The anodic polarization intervals suppressed the deposition of the poisoning species on the electrode, and the amount of two hydrocarbons produced, CH 4 and C 2 H 6 , decreased only slightly even after one hour. By choosing the appropriate anodic potential and time duration the selectivity for C 2 H 6 formation was significantly enhanced. The enhancement was found to be due to the copper oxide formed on the copper electrode. The selectivity was further improved when the electrochemical reduction was carried out using a copper oxide electrode. The highest efficiency of about 28% was obtained at -3.15 V.

Basic behaviors and properties of polyaniline(PA) deposited anodically on platinum electrodes have been studied on the following points. 1) Effect of the mode of electrolysis and supporting electrolytes in the film forming process. 2) Characteristics of charging-discharging processes. 3) Electric conductivity and elemental composition of PA. The different modes of electrolysis do not affect the characteristics of the PA electrode obtained. The growth rate of PA film is 2.7–2.8 times faster in sulfuric acid than in perchloric, nitric or hydrochloric acid. It is indicated that there are two types of doping; one is associated with the acid-base equilibrium between amino or imino group in the film and proton in the solution and the other is associated with the excess charge in the film produced by anodic oxidation. The electric conductivity of PA markedly decreases by the immersion in alkali solutions. The release of doped anion from PA by treating with an alkali solution is confirmed by the elemental analysis. The amount of anions occluded by the electrochemical doping process is determined to be 0.25–0.29 per monomer unit.