Ethanol electro-oxidation reaction using a polycrystalline nickel electrode in alkaline media: Temperature influence and reaction mechanism

• Anodic oxidation of ethanol at low temperature (−15 °C ⩽ T ⩽ 25 °C).
• Cyclic voltammetry and in situ FTIR analysis.
• Calculation of the apparent activation energy and discussion of the mechanism.

Mechanistic and kinetic details of the ethanol oxidation reaction using a nickel electrode in sodium hydroxide solution under well-controlled experimental conditions that include the variation of solution temperature and scan rate are discussed. Electrochemical analysis of ethanol oxidation is presented for the first time corresponding to the low temperature range (−15 °C ⩽ T ⩽ 25 °C) and demonstrates that the reaction proceeds even at −15 °C. Cyclic voltammetry (CV) analysis demonstrates that the ethanol oxidation reaction occurs through a mechanism that involves a chemical reaction between the ethanol molecule and the β-NiOOH species formed electrochemically on the electrode surface at potentials greater than 1.3 V. Decrease of temperature affects the kinetics of this reaction resulting in a decrease in the peak current density (j) and causes a shift in the peak potential of the ethanol oxidation toward less positive values. Arrhenius plots demonstrate that the ethanol oxidation reaction has a high apparent activation energy (Ea(app)), corroborating with the proposed mechanism that involves the reaction between the ethanol molecule and β-NiOOH in the rate-determining step. The j of ethanol oxidation at −15 °C is slightly affected by variation of the potential scan rate and rotation of the electrode. However, the potential scan rate has a considerable influence on the j of β-NiOOH formation and reduction reactions. Analysis of in situ FTIR spectroscopic data shows that this alcohol is converted selectively to the corresponding carboxylate (acetate) under the conditions of the study.