Site Sensitivity of Interfacial Charge Transfer and Photocatalytic Efficiency in Photocatalysis: Methanol Oxidation on Anatase TiO₂ Nanocrystals

Abstract

Photocatalytic oxidation of methanol on various anatase TiO2 nanocrystals was studied by in situ and time‐resolved characterizations and DFT calculations. Surface site and resulting surface adsorbates affect the surface band bending/bulk‐to‐surface charge migration processes and interfacial electronic structure/interfacial charge transfer processes. TiO2 nanocrystals predominantly enclosed by the {001} facets expose a high density of reactive fourfold‐coordinated Ti sites (Ti4c) at which CH3OH molecules dissociate to form the CH3O adsorbate (CH3O(a)Ti4c). CH3O(a)Ti4c localized density of states are almost at the valence band maximum of TiO2 surface, facilitating the interfacial hole transfer process; CH3O(a)Ti4c with a high coverage promotes upward surface band bending, facilitating bulk‐to‐surface hole migration. CH3O(a)Ti4c exhibits the highest photocatalytic oxidation rate constant. TiO2 nanocrystals enclosed by the {001} facets are most active in photocatalytic methanol oxidation.

Photocatalytic Production of Methyl Formate by Methanol Self-Coupling: From Oxidative Dehydrogenation to Direct Dehydrogenation

“…On the other hand, the Pd 0 /Pd 2+ ratio (0.5 wt % Pd/TiO 2 ) decreased to 1.11 after the reaction in argon (Figure S8, Table S3), while the methanol dehydrogenation activity reached a maximum (Table ), indicating that Pd 0 is the active site during the reaction. The presence of Pd 0 leads to the migration of the photogenerated electrons from TiO 2 to Pd 0 and promotes the combination of H* with e – to form H 2 , …”

One-Pot Synthesis of Hexamethylenetetramine Coupled with H2 Evolution from Methanol and Ammonia by a Pt/TiO2 Nanophotocatalyst

“…TiO 2 samples with the (101) and (001) facets were prepared according to the literature. 18 For TiO 2 (101), 6.6 mL of TiCl 4 was added dropwise into 20.0 mL of HCl aqueous solution (0.4 M) at 0 °C. After stirring for 0.5 h, the solution was added dropwise into 50.0 mL of NH 3 aqueous solution (5.5 wt %) under stirring at room temperature.…”

Conversion of Alcohols on Stoichiometric and Reduced Rutile TiO2 (110): Point Defects Meet Bifunctionality in Oxide (Photo-)Chemistry

“…5a, step (4)), which appears as a combination of several effects ranging from an improved light absorption due to populated in-band-gap states to a higher conductivity and other electronic effects enabling longer exciton lifetimes [56,129]. E.g., the higher coverage of methoxy-species on defective titania can alter the surface band bending of the semiconductor in favor of the oxidative pathway (upward band bending drives holes to the surface), while high coverages of molecular methanol may induce the reverse effect [130,131]. Other theoretical studies suggest that the hole is more localized on methoxy-species than on molecularly adsorbed methanol, and therefore is more reactive in the first case [121].…”