Characterization of the Active Surface Species Responsible for UV-Induced Desorption of O<sub>2</sub> from the Rutile TiO<sub>2</sub>(110) Surface

Henderson, Michael A.; Shen, Mei; Wang, Zhitao; Lyubinetsky, Igor

doi:10.1021/jp312161y

Cited by 37 publications

(76 citation statements)

References 116 publications

(297 reference statements)

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“…The band bending induced by the adsorbed (O2) − species is determined from core-level peak shifts in X-ray photoelectron spectroscopy (XPS). We discuss our results with respect to previous work on the prototypical rutile TiO2 (110) surface (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24).…”

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confidence: 55%

“…The adsorption of O2 has been studied in detail on the prototypical rutile (110) surface (11), and it is well accepted that an electron transfer is a prerequisite for O2 chemisorption. This was first proved by integral techniques, mainly a combination of TPD, photodesorption, and electron-stimulated desorption (12,(14)(15)(16)(17)(18)(19). The excess electrons on the rutile (110) surface are mainly provided by surface oxygen vacancies (22,23,44), although subsurface Ti interstitials also play a role (21).…”

Section: Discussionmentioning

confidence: 99%

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Electron transfer between anatase TiO ₂ and an O ₂ molecule directly observed by atomic force microscopy

Setvín

Hulva

Parkinson

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Activation of molecular oxygen is a key step in converting fuels into energy, but there is precious little experimental insight into how the process proceeds at the atomic scale. Here, we show that a combined atomic force microscopy/scanning tunneling microscopy (AFM/STM) experiment can both distinguish neutral O molecules in the triplet state from negatively charged (O) radicals and charge and discharge the molecules at will. By measuring the chemical forces above the different species adsorbed on an anatase TiO surface, we show that the tip-generated (O) radicals are identical to those created when () an O molecule accepts an electron from a near-surface dopant or () when a photo-generated electron is transferred following irradiation of the anatase sample with UV light. Kelvin probe spectroscopy measurements indicate that electron transfer between the TiO and the adsorbed molecules is governed by competition between electron affinity of the physisorbed (triplet) O and band bending induced by the (O) radicals. Temperature-programmed desorption and X-ray photoelectron spectroscopy data provide information about thermal stability of the species, and confirm the chemical identification inferred from AFM/STM.

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confidence: 55%

Section: Discussionmentioning

confidence: 99%

Electron transfer between anatase TiO ₂ and an O ₂ molecule directly observed by atomic force microscopy

Setvín

Hulva

Parkinson

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…The photochemistry of O 2 on R‐TiO 2 (110) has been largely studied using photo stimulated desorption (PSD) and STM methods. Using different “markers” (electron scavenger or hole scavenger), Yates and co‐workers have studied the desorption of O 2 on R‐TiO 2 (110) using the PSD method.…”

Section: Reaction Mechanisms In Tio2 Photocatalysismentioning

confidence: 99%

Fundamentals of TiO₂ Photocatalysis: Concepts, Mechanisms, and Challenges

et al. 2019

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Photocatalysis has been widely applied in various areas, such as solar cells, water splitting, and pollutant degradation. Therefore, the photochemical mechanisms and basic principles of photocatalysis, especially TiO2 photocatalysis, have been extensively investigated by various surface science methods in the last decade, aiming to provide important information for TiO2 photocatalysis under real environmental conditions. Recent progress that provides fundamental insights into TiO2 photocatalysis at a molecular level is highlighted. Insights into the structures of TiO2 and the basic principles of TiO2 photocatalysis are discussed first, which provides the basic concepts of TiO2 photocatalysis. Following this, details of the photochemistry of three important molecules (oxygen, water, methanol) on the model TiO2 surfaces are presented, in an attempt to unravel the relationship between charge/energy transfer and bond breaking/forming in TiO2 photocatalysis. Lastly, challenges and opportunities of the mechanistic studies of TiO2 photocatalysis at the molecular level are discussed briefly, as well as possible photocatalysis models.

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“…Interestingly, O 2 dissociation has been detected as a photochemical pathway on TiO 2 (110), which resulted from molecules bound directly at oxygen vacancy sites. 26,28,30 Given the presence of O 2 photodissociation in photochemistry on both the TiO 2 (110) and the (Fe,Cr) 3 O 4 (111) surfaces, the possibility exists that this process may occur on other oxides, particularly those employed as candidate photocatalysts for water oxidation. O 2 photodissociation represents an "unproductive" photochemical channel in water splitting photocatalysis that requires additional scrutiny.…”

Section: O 4 (111) Surface Suggestive Of O 2 Photodissociationmentioning

confidence: 99%

Photochemical Outcomes of Adsorbed Oxygen: Desorption, Dissociation, and Passivation by Coadsorbed Water

Henderson

2015

J. Phys. Chem. C

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A mixed Fe + Cr oxide surface was used to explore the photochemical fate of adsorbed O 2 under ultra-high-vacuum conditions. The mixed oxide surface possessed a magnetite-like (111) structure based on low-energy electron diffraction, with its chemical behavior resembling that of Fe 3 O 4 (111). Oxygen adsorption at 40 K resulted in two chemisorption states, a strongly bound form desorbing in temperature-programmed desorption (TPD) at 230 K and a weakly bound form evolving at 100 K. The former was assigned to charge transfer adsorption at Fe 2+ sites and the latter to electrostatic binding at Fe 3+ sites. A minority state was also detected at ∼160 K and tentatively assigned to adsorption at Cr 3+ sites. The 230 K O 2 state was the focus of photochemical studies employing four wavelengths of light from the red to the UV. Irrespective of wavelength, O 2 molecules in the 230 K state preferentially photodesorbed when irradiated, with comparable rates across the visible and an order of magnitude higher in the UV. Approximately 10% of adsorbed O 2 irreversibly photodissociated, irrespective of wavelength, with the resulting fragments blocking access to both Fe 3+ and Fe 2+ sites for subsequent O 2 adsorption. Preadsorbed water also blocked O 2 adsorption, but postadsorbed water stabilized O 2 at Fe 2+ sites in TPD to 285 K. The water-stabilized O 2 molecules were insensitive to photodesorption. O 2 photodissociation and photopassivation both represent potentially adverse outcomes in the release of O 2 during the heterogeneous water photooxidation reaction.

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Characterization of the Active Surface Species Responsible for UV-Induced Desorption of O₂ from the Rutile TiO₂(110) Surface

Cited by 37 publications

References 116 publications

Electron transfer between anatase TiO ₂ and an O ₂ molecule directly observed by atomic force microscopy

Electron transfer between anatase TiO ₂ and an O ₂ molecule directly observed by atomic force microscopy

Fundamentals of TiO₂ Photocatalysis: Concepts, Mechanisms, and Challenges

Photochemical Outcomes of Adsorbed Oxygen: Desorption, Dissociation, and Passivation by Coadsorbed Water

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Characterization of the Active Surface Species Responsible for UV-Induced Desorption of O2 from the Rutile TiO2(110) Surface

Cited by 37 publications

References 116 publications

Electron transfer between anatase TiO 2 and an O 2 molecule directly observed by atomic force microscopy

Electron transfer between anatase TiO 2 and an O 2 molecule directly observed by atomic force microscopy

Fundamentals of TiO2 Photocatalysis: Concepts, Mechanisms, and Challenges

Photochemical Outcomes of Adsorbed Oxygen: Desorption, Dissociation, and Passivation by Coadsorbed Water

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Characterization of the Active Surface Species Responsible for UV-Induced Desorption of O₂ from the Rutile TiO₂(110) Surface

Electron transfer between anatase TiO ₂ and an O ₂ molecule directly observed by atomic force microscopy

Electron transfer between anatase TiO ₂ and an O ₂ molecule directly observed by atomic force microscopy

Fundamentals of TiO₂ Photocatalysis: Concepts, Mechanisms, and Challenges