Anodic Oxidation of Ethylene Glycol on Platinum: a Mechanistic Study

Abstract

Anodic oxidation of ethylene glycol (EG) has been examined on platinum in 1 N HZSO, by means of potentiostatic and potentiodynamic techniques. Experimental results consist of steady-state, potentialcurrent relationships, reaction order derivatives, inhibition inflections, potentiodynamic profiles, and product analysis. Reaction mechanism has been proposed by combining these results with the previous information on the adsorption of EG on platinum, and on the p H effects in the anodic oxidation of EG. An analysis of these data has been presented in terms of kinetics under both Langmuir and Temkin conditions of electrode coverage. Inhibition inflections have been interpreted in terms of the kinetic theory of passivation effects proposed by Gilroy and Conway. It has been suggested that a chemical step of the type Pt.EG + Pt.OH -> Pt.R + HzO + Pt is the likely rate-determining-step (r.d.s.). The data indicate that quasi-equilibria prior to the r.d.s. are probably different in the ascending and descending direction of potentials (on the potentialxurrent curves), owing to the presence of different extents of oxygenated (Pt.OH or Pt.0) adsorbed species and the associated effects of coverage on kinetics.

Electrocatalytic oxidation of ethylene glycol on Pt and Pt–Ru nanoparticles modified multi-walled carbon nanotubes

“…As per the earlier reports, oxidation of ethylene glycol gives formic acid as one of the major product [62,63]. A probable mechanism as suggested by Bagotsky and Vijh [64], are given as follows (Steps 1-6).…”

Infrared Spectra of Hydroxyl Groups on the Surface of Platinum

“…On the other hand, electrochemists have for a number of years postulated that surface PtOH groups play an important role in many electrochemical processes (4)(5)(6). In this communication we present the first spectroscopic evidence for the existence of hydroxyl groups on the surface of platinum.…”

The Aqueous Photolysis of Ethylene Glycol Adsorbed on Goethite

“…Those photolysis reactions of the solution system based on inner coordination sphere charge transfer, produce 'OH, which then reacts with ethylene glycol in the outer coordination sphere to yield, in acid solution, acetaldehyde and higher aldehydes, but no formaldehyde (Carey et al 1977). Other evidence that solution oxidation reactions of ethylene glycol involving 'OH form only acetaldehyde and the higher aldehydes is found in the radiolysis of neutral, oxygenated, ethylene glycol-water solutions (Ahmad etaf., 1968), the oxidation of ethylene glycol in water by Fenton's Reagent(Fe2+ + H202) at various pH values (Walling and Johnson, 1975), and anodic oxidation of ethylene glycol in acid aqueous solutions (Vijh, 1971). At higher pH, 'OH reactions favor the production of glycolaldehyde, rather than acetaldehyde.…”