A dramatic difference between the electron-driven dissociation of alcohols and ethers and its relation to Rydberg states

Ibănescu, Bogdan C.; Allan, Michael

doi:10.1039/b806578k

Cited by 27 publications

(50 citation statements)

References 34 publications

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“…34 Free electrons could thus be produced during irradiation, and these free electrons could induce DEA of CH 3 OH. 51 However, the density of electron states near the Fermi level (E F ) of reduced TiO 2 (110) surfaces is quite small, 52,53 and the density of free electrons would be very low. Furthermore, DEA of gas-phase CH 3 OH is generally observed for electron attachment resonances that lie >6 eV.…”

Section: ■ Discussionmentioning

confidence: 99%

“…Furthermore, DEA of gas-phase CH 3 OH is generally observed for electron attachment resonances that lie >6 eV. 51 Thus, DEA by a free electron is expected to make little or no contribution to the photoinduced dissociation of CH 3 OH on TiO 2 (110).…”

Section: ■ Discussionmentioning

confidence: 99%

“…However, when molecules adsorb on a surface, the LUMO generally shifts ∼1−2 eV lower in energy. 55 Assuming a width of 1 eV (based on the observed full width at half-maximum of the low-energy resonance for electron attachment to gas-phase CH 3 OH), 51 it would be possible for a conduction-band electron to transfer to the LUMO of CH 3 OH.…”

Section: ■ Discussionmentioning

confidence: 99%

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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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Section: ■ Discussionmentioning

confidence: 99%

Section: ■ Discussionmentioning

confidence: 99%

Section: ■ Discussionmentioning

confidence: 99%

See 1 more Smart Citation

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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“…is shown at the bottom. Right: Potential curves of the ground state, the two lowest Rydberg states, and the lowest cation state of methanol [48,49].…”

Section: Formic Acidmentioning

confidence: 99%

“…Large DEA cross sections are often encountered in the 5-15 eV range and methanol will be briefly presented here as a prototype example [48,49]. The spectra for two representative fragments are shown in Fig.…”

Section: Core Excited Resonancesmentioning

confidence: 99%

Measuring and modeling absolute data for electron-induced processes

Allan

2012

J. Phys.: Conf. Ser.

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This article draws a connecting line between a number of publications scattered in the literature with the aim of making some general conclusions. Emphasis is on dissociative electron attachment (DAE), since this process leads to chemical change, essential for many applications. Four domains of phenomena involved in DEA are identified: threshold or 'nonlocal' phenomena, the 'multidimensional' phenomena, the Feshbach resonance domain, and processes where scrambling of atoms occurs. The point is made that these four groups of phenomena are linked in real world, and that a unified theory describing all of them is required.

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Low‐lying Negative Ion States Probed in Potassium – Ethanol Collisions

Lozano,

Kumar,

Pereira

et al. 2024

ChemPhysChem

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Dissociative electron transfer in collisions between neutral potassium atoms and neutral ethanol molecules yields mainly OH−, followed by C2H5O−, O−, CH3− and CH2−.The dynamics of negative ions have been investigated by recording time‐of‐flight mass spectra in a wide range of collision energies from 17.5 to 350 eV in the lab frame, where the branching ratios show a relevant energy dependence for low/intermediate collision energies.The dominant fragmentation channel in the whole energy range investigated has been assigned to the hydroxyl anion in contrast to oxygen anion from dissociative electron attachment (DEA) experiments. This result shows the relevant role of the electron donor in the vicinity of the temporary negative ion formed allowing access to reactions which are not thermodynamically attained in DEA experiments.The electronic state spectroscopy of such negative ions, was obtained from potassium cation energy loss spectra in the forward scattering direction at 205 eV impact energy, showing a prevalent Feshbach resonance at 9.36 ± 0.10 eV with character, while a less pronounced contribution assigned to a shape resonance has been obtained at 3.16 ± 0.10 eV.Quantum chemical calculations for the lowest‐lying unoccupied molecular orbitals in the presence of a potassium atom have been performed to support the experimental findings.

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A dramatic difference between the electron-driven dissociation of alcohols and ethers and its relation to Rydberg states

Cited by 27 publications

References 34 publications

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

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

Measuring and modeling absolute data for electron-induced processes

Low‐lying Negative Ion States Probed in Potassium – Ethanol Collisions

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A dramatic difference between the electron-driven dissociation of alcohols and ethers and its relation to Rydberg states

Cited by 27 publications

References 34 publications

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

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

Measuring and modeling absolute data for electron-induced processes

Low‐lying Negative Ion States Probed in Potassium – Ethanol Collisions

Contact Info

Product

Resources

About

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

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