Imaging Consecutive Steps of O2 Reaction with Hydroxylated TiO₂(110): Identification of HO₂ and Terminal OH Intermediates

Journal Article · Thu Jan 15 04:00:00 EST 2009 · Journal of Physical Chemistry C, 113(2):666-671

DOI:https://doi.org/10.1021/jp807030n· OSTI ID:949066

Du, Yingge; Deskins, N Aaron; Zhang, Zhenrong; Dohnalek, Zdenek; Dupuis, Michel; Lyubinetsky, Igor

We report results of the combined experimental and theoretical investigation of the molecular oxygen reaction with a partially hydroxylated TiO₂(110) surface. The consecutive steps of both primary and secondary site-specific reactions have been tracked with high-resolution scanning tunneling microscopy (STM). For the first time, we have directly imaged stable, adsorbed hydroperoxyl (HO₂) species, which is believed to be a key intermediate in many heterogeneous photochemical processes but generally metastable and “elusive” until now. We also found terminal hydroxyl groups, another critical but never directly observed intermediates. A conclusive evidence that O₂ reacts spontaneously with a single bridging OH group as an initial reaction step is provided. The experimental results are supported by density functional theory (DFT) calculations that have determined species energies and configurations. Reported observations provide a basis for a consistent description of the elementary reaction steps and offer molecular-level insight into the underlying reaction mechanisms. In a broader perspective, the results are expected to have far reaching implications for various catalytic systems involving the interconversion of O₂ and H₂O.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 949066
• Report Number(s): PNNL-SA-61064; 19811; 25619; KC0301010
• Journal Information: Journal of Physical Chemistry C, 113(2):666-671, Journal Name: Journal of Physical Chemistry C, 113(2):666-671 Journal Issue: 2 Vol. 113; ISSN 1932-7447
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CHEMICAL REACTION KINETICS
DENSITY FUNCTIONAL METHOD
DFT
Environmental Molecular Sciences Laboratory
HYDROPEROXY RADICALS
H₂O
OXYGEN
O₂
REACTION INTERMEDIATES
STM
TITANIUM OXIDES
TiO₂