Modeling Mechanochemical Reaction Mechanisms

The mechanochemical reaction between copper and dimethyl disulfide is studied under well-controlled conditions in ultrahigh vacuum (UHV). Reaction is initiated by fast S-S bond scission to form adsorbed methyl thiolate species, and the reaction kinetics are reproduced by two subsequent elementary mechanochemical reaction steps, namely a mechanochemical decomposition of methyl thiolate to deposit sulfur on the surface and evolve small, gas-phase hydrocarbons, and sliding-induced oxidation of the copper by sulfur that regenerates vacant reaction sites. The steady-state reaction kinetics are monitored in situ from the variation in the friction force as the reaction proceeds and modeled using the elementary-step reaction rate constants found for monolayer adsorbates. The analysis yields excellent agreement between the experiment and the kinetic model, as well as correctly predicting the total amount of subsurface sulfur in the film measured using Auger spectroscopy and the sulfur depth distribution measured by angle-resolved X-ray photoelectron spectroscopy. Fil: Adams, Heather. University of Wisconsin; Estados Unidos Fil: Miller, Brendan P.. Chevron Oronite Company; Estados Unidos Fil: Furlong, Octavio Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; Argentina Fil: Fantauzzi, Marzia. INSTM; Italia Fil: Navarra, Gabriele. INSTM; Italia Fil: Rossi, Antonella. INSTM; Italia Fil: Xu, Yufu. Hefei University of Technology; China Fil: Kotvis, Peter V.. University of Wisconsin; Estados Unidos Fil: Tysoe, Wilfred T.. University of Wisconsin; Estados Unidos