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

The electrooxidation of 1-butanol (1-BL) on Pt electrodes was studied using cyclic voltammetry and in situ FTIR spectroscopy. The results de monstrated that 1-BL can undergo dehydration to form CH3CH2CH=CH2 in a cid solutions. The IR absorption of the C=C bond yielded a broad band around 1600 cm(-1), which has been determined in solutions prepared us ing 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 linea rly bonded CO species. At potentials below 0.30 V(SCE), the dissociati ve adsorbates accumulated and absorbed stably on the Pt surface to inh ibit 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 ascrib ed to IR absorption of the carbonyl group, which, together with the IR bands appearing in the fingerprint region, suggested the production o f butyric acid in the oxidation of 1-BL. In considering the large inte nsity of the carbonyl band in spectra obtained at potentials above 0.3 0 V(SCE), the butyric acid was assigned as one of the product species. Butyric acid has been considered also as an intermediate species invo lved in 1-BL oxidation, since, at higher potentials (> 0.40 V), butyri c acid can be oxidised to CO2, although the complete oxidation of buty ric acid to CO2 is rather difficult. The present study demonstrated, a t the molecular level, that the oxidation of 1-BL obeys the dual-path reaction mechanism. (C) 1997 Elsevier Science S.A.