A COMPARISON OF ELECTROCHEMICAL AND GAS-PHASE DECOMPOSITION OF METHANOL ON PLATINUM SURFACES

By using electrochemical and ultrahigh-vacuum (UHV) techniques, combined with an isotope substitution method, it is found that the mechanism of methanol decomposition on platinum in the electrochemical environment is different than that in the UHV. In the UHV, the first step in the decomposition process is the scission of an O-H bond to yield a methoxy intermediate, whereas in the electrochemical environment, the first step is the scission of a C-H bond. The difference in the decomposition mechanism is discussed in terms of difference in the local electric field at the surface and in terms of methanol hydro-phobic/hydrophilic interactions in solution. The latter affect methanol-water near-surface conformation and predetermine the destiny of the individual methanolic bonds in the catalytic splitting.