Anatomy of the Photochemical Reaction: Excited-State Dynamics Reveals the C–H Acidity Mechanism of Methoxy Photo-oxidation on Titania

Abstract

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.

Mechanism of photocatalytic water oxidation on small TiO2 nanoparticles

“…21,23,24 The charge-transfer (CT) reactivity seen in our simulations is indirectly supported by a TS study of Ti(OH) 4 28 and NAMD simulations of the oxidation of chemisorbed methanol on a TiO 2 surface. 38 …”

Two-dimensional forms of robust CO2 reduction photocatalysts

“…In particular, the predicted weak CO binding for SiAs, ZnSe, and ZnTe could facilitate selectivity, which would demand the presence of a co-catalyst to facilitate further reactions. Further excited-state studies could probe possible photoexcitation and reaction pathways 72 . For ZnTe and ZnSe in particular, the projected density of states indicate that the high valence bands tend to exhibit anionic (Se, Te) character and the low conduction bands have the character of the cation, Zn, similar to behavior seen in oxide systems 73 .…”

Electron-phonon coupling in d -electron solids: A temperature-dependent study of rutile TiO2 by first-principles theory and two-photon photoemission

“…Electron-phonon (e-p) interaction pervasively impacts crystalline materials, is the key physical property that defines conductivity, superconductivity [1,2], and solar energy conversion [3][4][5][6]; moreover, it determines the temperature scales for quantum phase transitions [7,8] and electron-spindependent phenomena [9], controls reactivity of catalytic chemical reactions [10,11], influences the topological properties of high-Z materials, defines the nonradiative dynamical processes of photogenerated carriers, etc. Despite importance of e-p interaction in the electronic, optical, chemical, and thermal properties of materials, a broadly applicable and simple to apply theory or physical principles that consider the atomic character of the frontier orbitals, and based on that can explain the broad spectrum of e-p interactions, does not exist.…”