Quantitative DEMS study of ethanol oxidation: effect of surface structure and Sn surface modification

Abstract

Using the dual thin layer flow through cell, a semi-quantitative analysis of the volatile products during the electrooxidation of adsorbed and bulk solution of 0.01 M ethanol at polycrystalline platinum, smooth, roughened and Sn modified Pt(11,1,1), Pt(311) electrodes has been done by on-line differential electrochemical mass spectroscopy (DEMS). In addition to the current efficiency of CO(2), that of acetaldehyde was determined as a function of the flow rate. At polycrystalline platinum, ethanol oxidation produces only acetaldehyde; the amount of acetaldehyde further oxidized to acetic acid is negligible due to convection conditions. For comparison and for calibration purposes, i-propanol oxidation was examined for which acetone is the only oxidation product. At Pt(11,1,1), the main oxidation product is acetaldehyde. At Pt(311), in addition to acetaldehyde, acetic acid was also formed. Surface modification with Sn did not increase the reactivity of Pt(11,1,1) instead it led to inhibition of the ethanol oxidation. In the case of Pt(311), the onset potential of oxidation was shifted negatively by 0.2 V in the presence of Sn. The results of the potentiostatic measurements showed that this shift is not associated with the production of CO(2); rather acetic acid and acetaldehyde are the main oxidation products.

Effect of Mass Transport on the Electrochemical Oxidation of Alcohols Over Electrodeposited Film and Carbon-Supported Pt Electrodes

“…Mostafa et al [22] observed a CO 2 product yield of 1% in comparison to CH 3 CHO (55%) and CH 3 COOH (44%) during EOR on Pt/C. Ethane 1,1 diol [11] was also detected as a product of EOR which forms as result of hydrolysis of CH 3 CHO.…”

“…(1) (2) A DEMS study for the ethanol oxidation reaction (EOR) on Pt has shown that EOR mainly forms CO 2 , CH 3 CHO and CH 3 COOH [18,22,39,40]. Mostafa et al [22] observed a CO 2 product yield of 1% in comparison to CH 3 CHO (55%) and CH 3 COOH (44%) during EOR on Pt/C.…”

“…Pt is known as the most active single metal catalyst for alcohol oxidation reaction in acidic media and has been studied extensively for methanol [6][7][8][9][10], ethanol [11][12][13] and butanol isomers [4,5,[14][15][16]. The intermediates formed during the oxidation of the alcohol molecules on the Pt surfaces have been identified using various electrochemical and spectroscopic techniques such as in-situ FT-IR [17,18] and online differential electrochemical mass spectroscopy (DEMS) [18][19][20][21][22][23]. Based on these studies, a dual path reaction mechanism (Scheme 1) has been proposed and well documented for small chain alcohol molecules [24].…”

Ethanol oxidation on shape-controlled platinum nanoparticles at different pHs: A combined in situ IR spectroscopy and online mass spectrometry study

“…The decrease at E<0.6 V is a consequence of the COads re-poisoning of the surface and the diminution of oxidation rates as the electrode potential diminishes [38,39]. However, this process depends on the surface structure and on the pH of the electrolyte.…”

“…In this experiment, an ethanol solution is flown through the cell at 0.4 V for two minutes, to allow the cleavage of ethanol molecules and adsorption of fragments. After that, the solution is changed to a solution containing only the supporting electrolyte at the same pH and then the electrode is cycled between 0.04 and 0.95 V vs RHE at v=5 mVs -1 , registering simultaneously the Faradic and mass spectrometric ion currents [39,43]. to CH4 at low potentials [36,44] whereas I44 in this particular case only gives information about CO2 formed, since ethanol has been removed from the solution.…”