ADSORBATE FORMATION DURING THE ELECTROCHEMICAL REDUCTION OF CARBON-DIOXIDE AT PALLADIUM - A DEMS STUDY

Electrochemical reduction of carbon dioxide is followed via cyclic vol tammetry (cv) and on-line mass spectrometry (DEMS) at sputtered pallad ium in aqueous 0.1M KHCO3 solution. Carbon monoxide is detected as a v olatile reduction product at potentials more negative than - 1.4V vs. Ag/AgCl. During the first potential scan consumption of carbon dioxide is already observed at -1 V vs. Ag/AgCl corresponding to a cathodic s ignal in cv. Flow cell experiments show that an adsorbate is formed at - 1 V. Carbon monoxide is generated from this adsorbate between - 1.4 and - 1.9 V. Oxidation of the adsorbate forming carbon dioxide is obs erved between 0.2 and 0.6 V. At - 1 V adsorbed CO/COOH is likely to be formed from carbon dioxide, inhibiting further CO2 reduction. Reducti on of CO2 proceeds after desorption of the adsorbate at potentials bel ow - 1.4V vs. Ag/AgCl. Copyright (C) 1996 Elsevier Science Ltd