ELECTROCHEMICAL REACTIVITY OF ETHANOL ON POROUS PT AND PTRU - OXIDATION REDUCTION REACTIONS IN 1 M HCLO4/

Electrochemical oxidation/reduction reactions of ethanol in 1 M HClO4 were studied on porous Pt, Pt0.92Ru0.08, Pt0.85Ru0.15, and Ru under po tentiodynamic conditions. The electrodes with defined bulk and surface compositions were made by electrodeposition on porous Au substrates. Cyclic voltammetry in combination with on-line mass spectrometry (DEMS ) was employed to correlate faradaic currents with ion currents associ ated to reaction products. The formation of both CO2 and ethanal was u nequivocally identified during ethanol oxidation on PtRu and Pt by usi ng d(3)-ethanol. On pure Ru neither faradaic currents were observed no r oxidation/reduction products could be detected by mass spectrometry. The reduction of ethanol on Pt and PtRu to methane and ethane was fou nd in the potential range of hydrogen adsorption. The yields of oxidat ion and reduction products and the corresponding onset potentials for their formation are greatly influenced by the Ru content. Alloys with high Ru content exhibit a lower reaction rate for ethanol electrooxida tion. On the other hand, the selectivity for ethanal production is sig nificantly enhanced for PtRu as compared to pure Pt.