%0 Journal Article %J JOURNAL OF PHYSICAL CHEMISTRY LETTERS %D 2015 %T Anatomy of the Photochemical Reaction: Excited-State Dynamics Reveals the C-H Acidity Mechanism of Methoxy Photo-oxidation on Titania %A Grigory Kolesov %A Dmitry Vinichenko %A Tritsaris, Georgios A. %A Cynthia M. Friend %A Efthimios Kaxiras %X Light-driven chemical reactions on semiconductor surfaces have potential for addressing energy and pollution needs through efficient chemical synthesis; however, little is known about the time evolution of excited states that determine reaction pathways. Here, we study the photo-oxidation of methoxy (CH3O) derived from methanol on the rutile TiO2(110) surface using ab initio simulations to create a molecular movie of the process. The movie sequence reveals a wealth of information on the reaction intermediates, time scales, and energetics. The reaction is broken in three stages, described by Lewis structures directly derived from the ``hole'' wave functions that lead to the concept of ``photoinduced C-H acidity''. The insights gained from this work can be generalized to a set of simple rules that can predict the efficiency of photo-oxidation reactions in reactant-catalyst pairs. %B JOURNAL OF PHYSICAL CHEMISTRY LETTERS %V 6 %P 1624-1627 %8 MAY 7 %G eng %N 9 %R 10.1021/acs.jpclett.5b00429