In situ FTIR spectroscopic studies of the electrooxidation of C-4 alcohol on a platinum electrode in acid solutions Part I. Reaction mechanism of 1-butanol oxidation
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The electrooxidation of 1-butanol (1-BL) on Pt electrodes was studied using cyclic voltammetry and in situ FTIR spectroscopy. The results demonstrated that 1-BL can undergo dehydration to form CH3CH2CH=CH2 in acid solutions. The IR absorption of the C=C bond yielded a broad band around 1600 cm(-1), which has been determined in solutions prepared using both Milli-Q water and deuterated water. Evidence for dissociative adsorption of 1-BL on a Pt surface was given by the appearance of an IR band near 2060 cm(-1), which was assigned to IR absorption of linearly bonded CO species. At potentials below 0.30 V(SCE), the dissociative adsorbates accumulated and absorbed stably on the Pt surface to inhibit the oxidation of 1-BL. When the adsorbed CO species started to be removed by oxidation at potentials 2 0.30 V(SCE), two strong IR bands near 2345 and 1712 cm(-1) appeared in the spectra. The band near 2345 cm(-1) was attributed to the asymmetrical stretch of the CO2 molecule which is the product species. The IR band near 1712 cm(-1) was ascribed to IR absorption of the carbonyl group, which, together with the IR bands appearing in the fingerprint region, suggested the production of butyric acid in the oxidation of 1-BL. In considering the large intensity of the carbonyl band in spectra obtained at potentials above 0.30 V(SCE), the butyric acid was assigned as one of the product species. Butyric acid has been considered also as an intermediate species involved in 1-BL oxidation, since, at higher potentials (> 0.40 V), butyric acid can be oxidised to CO2, although the complete oxidation of butyric acid to CO2 is rather difficult. The present study demonstrated, at the molecular level, that the oxidation of 1-BL obeys the dual-path reaction mechanism. (C) 1997 Elsevier Science S.A.