Spectroelectrochemical investigation of the adsorption and oxidation of unsaturated C4-alcohols

The adsorption and oxidation of cis-2-butene-1,4-diol and 2-butyne-1,4-diol at gold and platinum electrodes have been investigated with in situ infrared and surface-enhanced Raman spectroscopy (SERS). SER-spectroscopic results indicate a strong interaction of the unsaturated bond with the gold surface, as evidenced by a strong shift of the stretching frequency of this bond to lower wavenumbers. In addition, an interaction of the OH groups with the electrode surface has been detected with in situ infrared spectroscopy. At platinum electrodes, the adsorbed molecules are partially decomposed, resulting in the formation of carbon monoxide and further molecular fragments. The oxidation of these molecules proceeds via aldehydes as intermediates, leading to carbon dioxide or carbonate as final products. Only in the case of oxidation of 2-butene-1,4-diol in alkaline solution is a stable anion of the unsaturated diacid (maleic acid) formed at both the gold and the platinum electrode in addition. (C) 2000 Elsevier Science B.V. All rights reserved.