The Electrochemical Oxidation of Ethylene: An Experimental Study

Abstract

Both steady state and time dependent current-voltage curves of the anodic oxidation of ethylene were studied at the electrode Pt(Pt)I1M NaOH, C2H4 (diss.), conditions for obtaining the Tafel slope, found to be approximately 2RT/F, were established. Ethylene partial pressure had no measurable effect on the steady state current-voltage curve in the Tafel region. The Pt electrode was found to become "passivated" at about 0v (NHE). Time dependent studies showed that the electrode became continuously less active. Experiments were carried out in a closed cell arrangement, where ethylene consumed at the anode and coulombs passed could be measured simultaneously. Within experimental error, one mole of ethylene was found to involve the passage of twelve Faradays, showing that ethylene is totally oxidized. An analysis of the experimental data in terms of single electron transfer steps, limiting surface coverage and Tafel transfer coefficients of ~1/2 leads to the conclusion that the OH-discharge most likely plays the dominant role in the rate determining step.

The Mechanism of Electrochemical Oxidation of Organic Fuels

“…For example, in a study of the anodic oxidation of ethylene in alkaline solution, the dependence of the Tafel slope on the degree of approach to steady state was determined. 69 The current-potential curves determined potentiostatically at 5 min intervals for approach to steady state gave Tafel slopes of about 300 m V. These slopes decreased with increasing length of time for steady-state current to be established, and for 60 min and times greater than 60 min, up to several hours, a slope of about 150 m V was obtained. Since a slope of 150mV, i.e., 2RTjF, is a rational slope which is significant for interpretation in electrode kinetics, and 300 m V is not a rational slope, the use of longer times for the establishment of steady-state conditions is justified.…”

“…The functionf(O) represents the rate of change of the apparent standard free energy of adsorption ~G~ with total coverage 0/ 19 (69) …”

“…39 Steady states required 30-60 min for oxalic acid oxidation 226 and for acetylene oxidation,193 and several hours were required for ethylene oxidation in alkaline solution. 69 The results obtained by Bockris, Wroblowa, Gileadi, and Piersma show that times varying from a few minutes to several hours, depending on the potential region, are required to attain steady-state behavior for the anodic oxidation of unsaturated hydrocarbons. 32 .…”

Anodic Oxidation of Ethylenediaminetetraacetic Acid on Platinum Electrode in Alkaline Medium

“…The concentration dependence (reaction order) of the EDTA electroactive species was obtained from the slope of the plot in Fig. 14 to be Reaction order for EDTA = = log i = 0.54 [21] log CEDTA )T,P,E,PH…”

ELECTROCHEMICAL OXIDATION OF ETHYLENE AT PANI/Pt AND Ag/PANI/Pt MODIFIED ELECTRODES

“…Traditionally in the sixties, the electrochemical oxidation of ethylene on noble metals was studied at high temperature (80 °C) and pH. [1][2][3] Under these conditions, ethylene can only be anodically oxidized to CO 2 :…”