Abstract
The present paper reports cyclic voltammetric and a.c. impedance spectroscopy investigations on the influence of the acetonitrile concentration on the kinetics (and individual product’s efficiency) of the ethanol oxidation reaction (EOR), performed on a polycrystalline Pt electrode surface in 0.5 M H2SO4 and 0.1 M NaOH supporting solutions. The kinetics of the EOR were examined at room temperature over the voltammetric potential range, which covers the electrooxidation of surface-adsorbed COAds species, as well as the formation of acetaldehyde molecules. In addition, the time-dependent efficiency of acetate and acetaldehyde formation in relation to the initial acetonitrile content for both acidic and alkaline electrolytes was evaluated by means of spectrophotometric Ultraviolet/ Visible Spectroscopy (UV-VIS) instrumental analysis.
Highlights
The process of the electrochemical oxidation of alcohols has a direct application in the so-calledDirect Alcohol Fuel Cells (DAFCs)
When the Cyclic Voltammetry (CV) sweep is reversed towards the hydrogen reversible potential, a single anodic peak, centered at about 0.60 V, appears in the CV profile
The lowest potential oxidation peak (0.60 V) is typically assigned in the literature to the process of the oxidation of surface-adsorbed COAds species, while that observed at 0.80 V is assigned to the formation of acetaldehyde [3,13,14,16]
Summary
The process of the electrochemical oxidation of alcohols has a direct application in the so-calledDirect Alcohol Fuel Cells (DAFCs). Methanol and ethanol are the most frequently investigated alcohols for PEM fuel cell applications, where C2 H5 OH is regarded as a promising substitute for CH3 OH, due to its considerably higher (8.0 vs 6.1 kWh kg−1 ) energy-density and the relatively low toxic properties of ethanol oxidation by-products (acetaldehyde and acetic acid). The process of ethanol electrooxidation on platinum-based catalyst surfaces (the most important catalyst known in electrochemistry) is a complex anodic reaction, involving the formation of various, surface-adsorbed intermediates. It is commonly accepted [2,11,12,13] that following the surface electrosorption step, the C2 H5 OH molecule can either dissociate to surface-adsorbed COAds species, or become electrooxidized to form acetaldehyde. Afterwards, in the presence of adsorbed hydroxyl groups, successive oxidation steps lead to the formation of carbon dioxide or acetic acid molecules, Catalysts 2020, 10, 1286; doi:10.3390/catal10111286 www.mdpi.com/journal/catalysts
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