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The prospects for the electrochemical reduction of carbon dioxide to methanol were examined by investigating the intermediate reactions. The reduction of carbon dioxide was carried out in a neutral electrolyte at a mercury electrode. The high overvoltage observed for carbon dioxide reduction to the formate anion reflects a low value for the efficiency of electric energy utilization for this process. Formic acid can be reduced to methanol in a perchloric acid electrolyte (at a lead electrode) or in a buffered formic acid electrolyte (at a tin electrode). The faradaic efficiency for methanol formation is close to 100% at the tin electrode in a narrow potential region corresponding to a low current density. The potential dependence of formic acid reduction to methanol suggests that the adsorption of formic acid on the electrode, near the pzc, may be the rate‐controlling step in the over‐all reaction. The reduction of formaldehyde to methanol occurs with a faradaic efficiency exceeding 90% in a basic solution. The Tafel slope decreases when either the formaldehyde concentration is increased (at constant pH) or when thepH of the solution is increased (at constant concentration). The polyoxymethylene glycols present as impurities in formaldehyde solutions may influence the mechanism of the electrode process through interaction with formaldehyde molecules and/or other adsorbed species resulting in small changes of the Tafel slope.

High rate anodic dissolution of iron in a sulfuric acid electrolyte causes the solution near the electrode surface to become supersaturated in ferrous sulfate. Ferrous sulfate crystals precipitate on the electrode surface when the surface concentration exceeds a critical value. This critical value is about 1.8 times greater than the saturation concentration of ferrous sulfate. Continued precipitation results in the growth of a porous ferrous sulfate film on the surface. A mathematical model describing the initial formation and subsequent growth of this salt film is developed for a rotating disk geometry. A perturbation analysis serves as the foundation of this model. The salt film thickness is nearly proportional to the square root of time shortly after the initial precipitation. The film growth rate falls off sharply in time following this initial period because of depletion of ferrous ions from the solution adjacent to the electrode surface.ABSTRACT RuO2 single-crystal electrodes have been used to study the mechanism of the chlorine evolution]reduction reactions. RuO~ (110) and (101) surfaces show the same anodic Tafel slopes equal to 40 mV/decade. Significant differences in the electrocatalytic behavior of these two surfaces were found for the chlorine reduction reactions. Two cathodic voltammetric peaks at E = 780 and E = 220 mV vs. SCE reference were observed for the RuO~ (110) electrodes. The peak at E =

A mathematical model describing sustained current oscillations observed in the iron‐sulfuric acid system, under potentiostatic conditions, is presented. This model assumes that the sustained oscillations are due to a continuous cycling of a portion of the electrode between the active and the passive states. The electrode surface is covered by a porous ferrous sulfate film. Transient changes in the potential and concentration profiles in the pores of the salt film and in the diffusion layer are responsible for the continuous cycling. A one‐dimensional model that describes these processes is presented. Results from this model are compared to the experimental current‐time curves. The calculated current‐time curve shows oscillatory behavior. The characteristics of the calculated current‐time curve differ from experimental results. The calculated ferrous sulfate film thickness is substantially thinner than expected from a steady‐state analysis and from the previously reported work of others. Due to lack of quantitative agreement between experimental and calculated results, two modifications to the present model are proposed in a qualitative manner. These modifications suggest that one may wish to: (i) remove the requirement of passivation, and assume that the current oscillations are caused by continuous cycling in the fraction of the electrode surface area that is covered by ferrous sulfate; (ii) assume that the current oscillations are caused by continuous cycling in the porosity of the salt film in combination with changes in the amount of active area. Both proposed modifications would include kinetics of salt‐film precipitation and dissolution. It is anticipated that finite precipitation and dissolution kinetics will increase the calculated salt‐film thickness. Further work would be required to incorporate either modification into the model in a quantitative way.