DOI: 10.1002/elan.201300536 Electrocatalytic Oxidation of Ethylene Glycol at Pt/ Nanosized MO x /GC Composite Electrodes: SnO 2 in Comparison to CeO 2 and WO 3 A. A. El-Shafei,* [a, b] A. A. Ibrahim, [b] and A. M. A. Ouf [b, c] This Paper is Dedicated to Professor Wolf Vielstich on the Occasion of his 90 th Birthday. 1 Introduction Ever-growing deleterious effects resulting from chemical reactions used for energy production on the polluted planet is the major concern to the mankind. There is a need for the development of environmentally friendly technology to counteract such effects. The use of the direct oxidation alcohol fuel cell (DAFC) is a promising future energy technology alternative to conventional energy-generating devices, because of its high-energy con- version efficiency, low-to-zero pollutant emission, alco- hols availability, ease in distribution, and a high energy density. Improvement in alcohol oxidation is still an important task in fuel cell technology. Ethylene glycol (EG) is much less volatile and less toxic than methanol. It is electro- chemically oxidizable [1–3] and its complete oxidation in acidic medium produce 10e  per EG molecule compared to 6e  for methanol. EG has superior energy density (7.56 kWh dm 3 ) and higher boiling point (471 K) than some typical alcohol fuels such as methanol and ethanol [4]. Pt is at present the best-known catalyst for the adsorp- tion and dissociation of small organic molecules. Howev- er, it is generally accepted that Pt alone is not sufficient to oxidize alcohol at a reasonable rate, mainly because of surface poisoning. In addition to that, Ethylene glycol is aC 2 molecule having a C C bond in its structure. C  C bond is a stumbling block for electro-organic chemists since thus C C bond is comparatively strong and cannot chemists be easily cleaved [5]. Ordinal Pt catalyst cannot achieve the complete oxidation of ethylene. To achieve this, it is necessary to modify the composi- tion and the structure of the anode catalyst [6–10]. In ad- dition to that complete oxidation as well as oxidation of poisoning intermediate requires an additional oxygen atom. It was reported that some metal oxides can act as oxygen storage component [11–13]. Recently, the synergistic effect of CeO 2 modified Pt/C towards EG oxidation in alkaline medium has been estab- lished [14]. Due to the interest on direct alcohol fuel cells using an acidic polymer electrolyte membrane, increasing effort is being dedicated to study EG in acidic media [15, 16]. The usage of MO x catalysts in acidic fuel cell technology is limited due to their solubility in acidic media. In the present study, three different MO x non-soluble in acidic media have been prepared and used to modify the Pt/GC electrode. The use of electrodeposition for electrode modification avoids the undesired effect of the adhesive agent [17] as well as reduces the cost of elec- trode preparation. The stability and activity of Pt/MO x / GC electrodes towards EG oxidation in acidic media have been examined using cyclic voltammetric and chro- noamperometric techniques. [a] A. A. El-Shafei Chemistry department, College of Science, King Faisal University Al-Hassa, Saudi Arabia *e-mail: aelshafei@kfu.edu.sa ashafei@mans.edu.eg [b] A. A. El-Shafei, A. A. Ibrahim, A. M. A. Ouf Chemistry Department, Faculty of Science, Mansoura University 35516 Mansoura, Egypt [c] A. M. A. Ouf Chemistry Department, College of Science, Taibah University Al-Olla, Saudi Arabia Abstract : Stable metal oxides insoluble in acidic medium have been prepared and characterized. The influence of the type of metal oxide (MO x ) on the activity of Pt to- wards ethylene glycol oxidation in acidic medium has been examined. All modified Pt/MO x /glassy carbon (GC) electrodes exhibited a better activity compared to Pt/GC. While Pt/SnO 2 /GC electrode exhibited the highest activi- ty, Pt/CeO 2 /GC revealed the best tolerance against poi- soning process. Keywords: Ethylene glycol oxidation · Nanosized MO x · Pt · Composite electrode www.electroanalysis.wiley-vch.de  2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Electroanalysis 2014, 26, 632 – 638 632 Full Paper