Predosed oxygen temperature programmed desorption as a kinetic probe of dehydrogenation on Pt(111)

Based on the propensity of surface atomic oxygen O(a) to react fiercely with H(a) on Pt(111) to form water that desorbs at low temperature, we have developed a thermal reaction and desorption technique—predosed oxygen temperature programmed desorption (POTPD)—which is useful for probing the kinetics of dehydrogenation on Pt(111). The method relies on very low coverages of O(a) which react with available adsorbed atomic H to form water, which desorbs promptly. Thus, the H₂O temperature programmed desorption reflects the dehydrogenation process. We have successfully utilized POTPD to determine the dehydrogenation temperatures of methylene (CD₂), methyl (CD₃), vinyl (CHCH₂), ethylene (C₂D₄), ethyl (C₂D₅), thioethoxy (SC₂H₅), and diethyl sulfide [S(C₂H₅)₂] on Pt(111). From the data, a mechanism and kinetic parameters for vinyl to ethylidyne conversion are presented.