UV-induced desorption of CH3X (X=I and Br)/TiO2(110)

Kim, Seong Han; Stair, Peter C.; Weitz, Eric

doi:10.1063/1.475914

Cited by 24 publications

(44 citation statements)

References 64 publications

(78 reference statements)

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“…An example of this is seen in the photochemistry of alkyl halides on R TiO 2 (110). Stair, Weitz and coworkers [680][681][682][683] have shown that bandgap excitation of TiO 2 leads to electron attachment to these adsorbed molecules, but does not result appreciable photodecomposition (as seen in the gas phase). Instead, rapid back-electron transfer to the surface occurs followed by photodesorption of the alkyl halide via the so-called Antoniewicz mechanism [684].…”

Section: Tio 2 Conduction Band To Electron Acceptormentioning

confidence: 94%

“…Although discussed in detail below, O 2 photodesorption is believed to result from the interaction of a VB hole with an adsorbed O δ− 2 species, resulting in a neutral O 2 molecule that readily desorbs from the surface. Other examples of molecular photodesorption from TiO 2 surfaces include alkyl halides [680][681][682]754,755,757], CO [783], N 2 O [705] and triethylamine [784]. The details of these events differ, but in each case the photodesorption event involves a charge carrier causing a charge change in the adsorbate-surface relationship that results in the adsorbate transitioning to a different potential energy surface (e.g., ion to neutral) that is more amenable to desorption.…”

Section: Photoadsorption and Photodesorptionmentioning

confidence: 96%

“…The most extensive work involving photochemical processes of brominated or iodinated hydrocarbons on a single crystal TiO 2 surface was done by the Stair, Weitz and coworkers [680][681][682][683]754,755]. These authors examined the photochemistry of methyl iodide and methyl bromide on R TiO 2 (110) using 257 and 320 nm laser light.…”

Section: Fluoro- Bromo-and Iodo-hydrocarbonsmentioning

confidence: 98%

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A surface science perspective on TiO2 photocatalysis

Henderson

2011

Surface Science Reports

1,838

1,634

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a b s t r a c tThe field of surface science provides a unique approach to understanding bulk, surface and interfacial phenomena occurring during TiO 2 photocatalysis. This review highlights, from a surface science perspective, recent literature that provides molecular-level insights into photon-initiated events occurring at TiO 2 surfaces. Seven key scientific issues are identified in the organization of this review. These are: (1) photon absorption, (2) charge transport and trapping, (3) electron transfer dynamics, (4) the adsorbed state, (5) mechanisms, (6) poisons and promoters, and (7) phase and form. This review ends with a brief examination of several chemical processes (such as water splitting) in which TiO 2 photocatalysis has made significant contributions in the literature.

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Section: Tio 2 Conduction Band To Electron Acceptormentioning

confidence: 94%

Section: Photoadsorption and Photodesorptionmentioning

confidence: 96%

Section: Fluoro- Bromo-and Iodo-hydrocarbonsmentioning

confidence: 98%

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A surface science perspective on TiO2 photocatalysis

Henderson

2011

Surface Science Reports

1,838

1,634

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“…24 A 266 nm photon has an energy of 4.67 eV, and the work function of a CH 3 OH-covered TiO 2 (110) surface is only about 4 eV. 34 Free electrons could thus be produced during irradiation, and these free electrons could induce DEA of CH 3 OH.…”

Section: ■ Discussionmentioning

confidence: 99%

Strong Photon Energy Dependence of the Photocatalytic Dissociation Rate of Methanol on TiO₂(110)

Yang

Ren

et al. 2013

J. Am. Chem. Soc.

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Photocatalytic dissociation of methanol (CH 3 OH) on a TiO 2 (110) surface has been studied by temperature programmed desorption (TPD) at 355 and 266 nm. Primary dissociation products, CH 2 O and H atoms, have been detected. The dependence of the reactant and product TPD signals on irradiation time has been measured, allowing the photocatalytic reaction rate of CH 3 OH at both wavelengths to be directly determined. The initial dissociation rate of CH 3 OH at 266 nm is nearly 2 orders of magnitude faster than that at 355 nm, suggesting that CH 3 OH photocatalysis is strongly dependent on photon energy. This experimental result raises doubt about the widely accepted photocatalysis model on TiO 2 , which assumes that the excess potential energy of charge carriers is lost to the lattice via strong coupling with phonon modes by very fast thermalization and the reaction of the adsorbate is thus only dependent on the number of electron−hole pairs created by photoexcitation. ■ INTRODUCTIONSince the discovery of the photocatalytic splitting of water (H 2 O) on TiO 2 electrodes by Fujishima and Honda in 1972, 1 tremendous research efforts have gone into understanding the fundamental processes and in enhancing the photocatalytic efficiency of TiO 2 . 2 These efforts have been driven by the potential benefits to renewable energy, energy storage, and environmental cleanup. 3,4 In particular, TiO 2 has attracted much attention because of its applications in heterogeneous catalysis, photocatalysis, solar energy devices, etc. 5−14In an ideal photocatalyst, all photon energy invested in the generation of charge carriers would be available for redox chemistry. The higher the potential energy of the electron (or hole) the more reductive (or oxidative) capacity there is.15 But charge carrier thermalization is rapid. For example, Gundlach and co-workers used two photon photoemission (2PPE) to track thermalization following electron injection from two dyes adsorbed on rutile TiO 2 (110). 16,17 Fast initial decay of the 2PPE signal resulting from thermalization of the injected electron occurred on the 10 fs time scale. This result suggests that excess potential energy is lost to the lattice via strong coupling with phonon modes, thus reducing the potential advantage gained by the specificity in the absorption event. Additional evidence for the rapid thermalization of electrons comes from photoemission spectra of Ag clusters on rutile TiO 2 (110) 18 as a function of injection electron energy and from photoluminescence spectra of rutile TiO 2 (110) 19,20 with 3.35 eV photon irradiation. In both these studies, a constant energy of the emitted photons was observed (at and below the band gap energy3.05 eV), independent of the energy of the exciting electron or photon. Furthermore, experimental investigations indicate that the photodesorption yield and translational energy of O 2 from an O 2 -adsorbed TiO 2 (110) surface are independent of the excitation photon energy above 3.4 eV, but instead depend on the photon flux. 21...

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“…14 There have been extensive experimental and theoretical studies on the photodissociation of CH 3 I in the gas phase [15][16][17][18][19][20][21][22][23][24] or adsorbed on different solid substrates. [25][26][27][28][29][30][31][32][33][34][35] Along with this wealth of information, the recent discovery of iodinecontaining organic compounds as potential sources of reactive halogen species during ozone depletion processes 36 has a) Author to whom correspondence should be addressed. Electronic mail:…”

Section: Introductionmentioning

confidence: 99%

Photodissociation of methyl iodide adsorbed on low-temperature amorphous ice surfaces

DeSimone

Olanrewaju

Grieves

et al. 2013

The Journal of Chemical Physics

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Photodissociation dynamics of methyl iodide (CH3I) adsorbed on both amorphous solid water (ASW) and porous amorphous solid water (PASW) has been investigated. The ejected ground-state I((2)P3∕2) and excited-state I((2)P1∕2) photofragments produced by 260- and 290-nm photons were detected using laser resonance-enhanced multiphoton ionization. In contrast to gas-phase photodissociation, (i) the I((2)P3∕2) photofragment is favored compared to I((2)P1∕2) at both wavelengths, (ii) I((2)P3∕2) and I((2)P1∕2) have velocity distributions that depend upon ice morphology, and (iii) I2 is produced on ASW. The total iodine [I((2)P3∕2)+I((2)P1∕2)+I2] yield varies with substrate morphology, with greater yield from ASW than PASW using both 260- and 290-nm photons. Temperature-programmed desorption studies demonstrate that ice porosity enhances the trapping of adsorbed CH3I, while pore-free ice likely allows monomer adsorption and the formation of two-dimensional CH3I clusters. Reactions or collisions involving these clusters, I atomic fragments, or I-containing molecular fragments at the vacuum-surface interface can result in I2 formation.

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UV-induced desorption of CH3X (X=I and Br)/TiO2(110)

Abstract: Articles you may be interested inDissociation mechanisms of excited CH3X (X = Cl, Br, and I) formed via high-energy electron transfer using alkali metal targets

Cited by 24 publications

References 64 publications

A surface science perspective on TiO2 photocatalysis

A surface science perspective on TiO2 photocatalysis

Strong Photon Energy Dependence of the Photocatalytic Dissociation Rate of Methanol on TiO₂(110)

Photodissociation of methyl iodide adsorbed on low-temperature amorphous ice surfaces

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UV-induced desorption of CH3X (X=I and Br)/TiO2(110)

Abstract: Articles you may be interested inDissociation mechanisms of excited CH3X (X = Cl, Br, and I) formed via high-energy electron transfer using alkali metal targets

Cited by 24 publications

References 64 publications

A surface science perspective on TiO2 photocatalysis

A surface science perspective on TiO2 photocatalysis

Strong Photon Energy Dependence of the Photocatalytic Dissociation Rate of Methanol on TiO2(110)

Photodissociation of methyl iodide adsorbed on low-temperature amorphous ice surfaces

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Product

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Strong Photon Energy Dependence of the Photocatalytic Dissociation Rate of Methanol on TiO₂(110)