Seite - 72 - in Advanced Chemical Kinetics

Rightmire et al. [36] studied the ethanol oxidation reactiononPt in acidicmedia andshowed the determining step of the reaction is formaldehyde formation.Moreover, Hitmi et al. [37] showed that the rate of formation of acetaldehyde is larger than acetic acid formation from ethanol oxidation reaction. The formation of acetic acid from acetaldehyde depends on the adsorptionofacetaldehydeonelectrodesurface, asproposedbyPodlovchenkoetal. [38]. ð16Þ The main problem of the catalysts is the poisoning effect by carbonaceous products from ethanol oxidation reaction strongly adsorbed on Pt. Nowadays, research is focused on the developmentofnewcatalyticspresentinghigherchemical stabilityandelectrochemicalkinetic rates. Thereare severalworks reportingSn-modifiedPt electrocatalyst as amoreactivemate- rial for ethanol oxidation reaction [39]. There aremany other interestingmaterials, such as PtRh [40], PtMo [41] and PtPd [42], but better performances of DEFC were observed employingPtSnat theanode,whicheffects thekineticof ethanoloxidation [43, 44]. Figure 9 shows the linear sweep voltammetry obtained for the ethanol oxidation on Pt electrocatalysts. FTIRwere collected in situwith electrodepolarization in ethanol solution. Pt Figure9. LinearsweepvoltammetryandFTIRregisteredonPtcatalystsin0.5molL�1H2SO4and0.5molL �1CH3CH2OH, at room temperature, v(lsv) = 1 mV�1 and FTIR measurements carried out in a mixture of 0.1 HClO4 (mol L �1) and CH3CH2OH(0.1molL �1). Advanced Chemical Kinetics72