Analysis of adsorbed intermediates and determination of surface potential shifts by dems

Differential electrochemical mass spectroscopy (DEMS) is used to elucidate the strongly bound intermediates of small organic molecules. The oxidation state of the adsorbates is determined by correlating the Faradaic charge of the electrodesorption peak with the amount of product formed. Isotope labelling yields information about the structure of the adsorbate. Thus, the intermediates of formic acid and methanol and also reduced CO2, all need 3 electrons to be oxidized to CO2. The adsorbates contain one C. one O, and H bound to the C. Therefore in all these cases the adsorbate is HCOad. In analogy, the intermediate of ethanol is characterized as CH3COad. Since the ion current of the product measured with the mass spectrometer is proportional to the Faradaic current only, the capacitive current can be calculated that flows while electrodesorption occurs. This allows the shift of the pzc caused by the adsorbate to be estimated. In the case of CO adsorbed on Pt a shift of 250 ± 40 mV was found.

[1]  Theodore B. Warner,et al.  Interaction of carbon dioxide with hydrogen chemisorbed on a platinum electrode. Interim report , 1966 .

[2]  V. Andreev,et al.  On the reasons for the discrepancies in the data on methanol adsorption on platinum , 1975 .

[3]  S. Raicheva,et al.  Mechanism of the electrooxidation of ethyl alcohol and acetaldehyde on a smooth platinum electrode , 1974 .

[4]  A. Wiȩckowski,et al.  Comparative study of adsorption and oxidation of formic acid and methanol on platinized electrodes in acidic solution , 1975 .

[5]  Y. Nishiyama,et al.  Surface interactions between chemisorbed species on platinum: Carbon monoxide, hydrogen, oxygen, and methanol , 1974 .

[6]  A. Kuhn,et al.  The Low Potential Oxidation of Ethanol on Bright Platinum , 1973 .

[7]  Andrzej Czerwiński,et al.  Kinetics of carbon dioxide adsorption on a platinum electrode , 1974 .

[8]  J. Giner.  The anodic oxidation of methanol and formic acid and the reductive. Adsorption of CO2 , 1964 .

[9]  J. Sobkowski,et al.  Kinetics of adsorbed “CO2” oxidation on a platinum electrode , 1975 .

[10]  V. S. Bagotzky,et al.  Generalized scheme of chemisorption, electrooxidation and electroreduction of simple organic compounds on platinum group metals , 1977 .

[11]  S. Raicheva,et al.  Mechanism of the electrooxidation of ethyl alcohol and acetaldehyde on a smooth platinum electrode: II. The effect of acetaldehyde on the processes of formation and removal of the surface oxide , 1974 .

[12]  S. Raicheva,et al.  Mechanism of the electrooxidation of ethyl alcohol and acetaldehyde on a smooth platinum electrode: III. Potential sweep investigation with varying reversal potential , 1974 .

[13]  A. Bewick,et al.  On the nature of reduced CO2: An IR spectroscopic investigation , 1982 .

[14]  J. Giner,et al.  Electrochemical reduction of CO2 on platinum electrodes in acid solutions , 1963 .

[15]  A. Bewick,et al.  A study by electrochemically modulated infrared reflectance spectroscopy of the electrosorption of formic acid at a platinum electrode , 1983 .

[16]  A. Bewick,et al.  Electrosorption of methanol on a platinum electrode. IR spectroscopic evidence for adsorbed co species , 1981 .

[17]  A. Capon,et al.  The oxidation of formic acid at noble metal electrodes: I. Review of previous work , 1973 .

[18]  E. Leiva,et al.  Multiple current components for methanol electrosorption and electro-oxidation at platinum in acidic solutions , 1983 .

[19]  Roger Parsons,et al.  The oxidation of formic acid at noble metal electrodes Part III. Intermediates and mechanism on platinum electrodes , 1973 .

[20]  M. Breiter.  Comparative oxidation of chemisorbed carbon monoxide, reduced carbon dioxide and species formed during the methanol oxidation , 1968 .

[21]  O. Wolter,et al.  Reaction Pathways of the Anodic Oxidation of Formic Acid on Pt Evidenced by 18O Labeling—A DEMS Study , 1985 .

[22]  O. Wolter,et al.  On the nature of the adsorbate during methanol oxidation at platinum: A DEMS study , 1985 .

[23]  T. Biegler,et al.  Adsorption and Oxidation of Methanol on a Platinum Electrode , 1967 .

[24]  J. Willsau,et al.  Elementary steps of ethanol oxidation on Pt in sulfuric acid as evidenced by isotope labelling , 1985 .

[25]  R. A. Rightmire,et al.  Ethyl Alcohol Oxidation at Platinum Electrodes , 1964 .

[26]  C. Lamy,et al.  Structural effects in electrocatalysis , 1983 .

[27]  H. Lal,et al.  A study of the oxidation of adsorbed films formed on platinized platinum in methanol, formic acid and carbon dioxide solutions , 1968 .

[28]  A. Kuhn,et al.  The Coverage of Platinized Platinum Electrodes with Simple Organic Species , 1965 .