Ultrafast Interfacial Proton-Coupled Electron Transfer

Li, Bin; Zhao, Jin; Onda, Ken; Jordan, Kenneth D.; Yang, Jinlong; Petek, Hrvoje

doi:10.1126/science.1122190

Cited by 214 publications

(325 citation statements)

References 33 publications

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“…22,23 TR-2PP has been applied to the spectroscopy and dynamics of single crystal rutile TiO 2 (110) surfaces under ultrahigh vacuum (UHV) conditions in the contexts of both photocatalysis and dye sensitized solar cells. [24][25][26][27][28][29][30][31][32][33] The well known surface preparation, properties, and chemistry make rutile TiO 2 (110) well suited for studies of elementary surface and bulk charge carrier processes triggered by photoexcitation in metal oxides. 4,6,7 Previous TR-2PP experiments on clean and protic solvent covered TiO 2 (110) surfaces with 400 nm (3.1 eV) excitation focused on the surface electronic structure.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast multiphoton pump-probe photoemission excitation pathways in rutileTiO2(110)

et al. 2015

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We investigate the spectroscopy and photoinduced electron dynamics within the conduction band of reduced rutile TiO 2 (110) surface by multiphoton photoemission (mPP) spectroscopy with wavelength tunable ultrafast (~20 fs) laser pulse excitation. Tuning the mPP photon excitation energy between 2.9 and 4.6 eV reveals a nearly degenerate pair of new unoccupied states located at 2.73±0.05 and 2.85±0.05 eV above the Fermi level, which can be analyzed through the polarization and sample azimuthal orientation dependence of the mPP spectra. Based on the calculated electronic structure and optical transition moments, as well as related spectroscopic evidence, we assign these resonances to transitions between Ti 3d-bands of nominally t 2g and e g symmetry, which are split by crystal-field. The initial states for the optical transition are the reduced Ti 3+ states of t 2g symmetry populated by formation oxygen vacancy defects, which exist within the band gap of TiO 2 . Furthermore, we studied the electron dynamics within the conduction band of TiO 2 by three-dimensional (3D) time-resolved pump-probe interferometric mPP measurements. The spectroscopic and time-resolved studies reveal competition between 2PP and 3PP processes where the t 2g -e g transitions in the 2PP process saturate, and are overtaken by the 3PP process initiated by the band gap excitation from the valence band of TiO 2 .

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Section: Introductionmentioning

confidence: 99%

Ultrafast multiphoton pump-probe photoemission excitation pathways in rutileTiO2(110)

et al. 2015

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“…13,14 A recent 2PPE study has detected an excited electronic state at about 2.4 eV above the Fermi level on the CH 3 OH/TiO 2 (110) surface. 15,16 This electronic excitation was attributed to a ''wet electronic state''.…”

Section: Introductionmentioning

confidence: 99%

Site-specific photocatalytic splitting of methanol on TiO2(110)

et al. 2010

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Clean hydrogen production is highly desirable for future energy needs, making the understanding of molecular-level phenomena underlying photocatalytic hydrogen production both fundamentally and practically important. Water splitting on pure TiO 2 is inefficient, however, adding sacrificial methanol could significantly enhance the photocatalyzed H 2 production. Therefore, understanding the photochemistry of methanol on TiO 2 at the molecular level could provide important insights to its photocatalytic activity. Here, we report the first clear evidence of photocatalyzed splitting of methanol on TiO 2 derived from time-dependent two-photon photoemission (TD-2PPE) results in combination with scanning tunneling microscopy (STM). STM tip induced molecular manipulation before and after UV light irradiation clearly reveals photocatalytic bond cleavage, which occurs only at Ti 4+ surface sites. TD-2PPE reveals that the kinetics of methanol photodissociation is clearly not of single exponential, an important characteristic of this intrinsically heterogeneous photoreaction.

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“…The simulated results are shown in Fig.5. The lifetime of the excited state on ethanol/TiO 2 (110) is 24 fs, which is close to that on the methanol/TiO 2 (110) interface with similar adsorbate coverage [26].…”

Section: B Dynamics Of the Electronic Excited Statementioning

confidence: 56%

“…Interferometric two-pulse correlation (I2PC) results on the ethanol/TiO 2 (110) interface have been analyzed by a numeric methods described previously [25]. The lifetime of the excited state is extracted to be 24 fs, which is similar to the case of methanol [26].…”

Section: Introductionmentioning

confidence: 96%

“…The phase averaged TR-2PPE results for the excited state on ethanol/o-TiO 2 (110) and polycrystalline molybdenum surface were extracted using the Fourier transformation procedure described before [25] and shown in Fig.5. The lifetime of the excited state on the 1 ML ethanol covered TiO 2 (110) surface is analyzed by a modified three-energy-level model [26,53]. This numeric method avoids solving the complicated optical Bloch equations and its validity has been demonstrated previously [25].…”

Section: B Dynamics Of the Electronic Excited Statementioning

confidence: 99%

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Kinetics and Dynamics of Photocatalyzed Dissociation of Ethanol on TiO2(110)

Zhou

Mao

et al. 2013

Chinese Journal of Chemical Physics

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The kinetics and dynamics of photocatalyzed dissociation of ethanol on TiO 2 (110) surface have been studied using the time-dependent and time-resolved femtosecond two-photon photoemission spectroscopy respectively, in order to unravel the photochemical properties of ethanol on this prototypical metal oxide surface. By monitoring the time evolution of the photoinduced excited state which is associated with the photocatalyzed dissociation of ethanol on Ti 5c sites of TiO 2 (110), the fractal-like kinetics of this surface photocatalytic reaction has been obtained. The measured photocatalytic dissociation rate on reduced TiO 2 (110) is faster than that on the oxidized surface. This is attributed to the larger defect density on the reduced surface which lowers the reaction barrier of the photocatalytic reaction at least methodologically. Possible reasons associated with the defect electrons for the acceleration have been discussed. By performing the interferometric two-pulse correlation on ethanol/TiO 2 (110) interface, the ultrafast electron dynamics of the excited state has been measured. The analyzed lifetime (24 fs) of the excited state is similar to that on methanol/TiO 2 (110). The appearance of the excited state provides a channel to mediate the electron transfer between the TiO 2 substrate and its environment. Therefore studying its ultrafast electron dynamics may lead to the understanding of the microscopic mechanism of photocatalysis and photoelectrochemical energy conversion on TiO 2 .

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Ultrafast Interfacial Proton-Coupled Electron Transfer

Cited by 214 publications

References 33 publications

Ultrafast multiphoton pump-probe photoemission excitation pathways in rutileTiO2(110)

Ultrafast multiphoton pump-probe photoemission excitation pathways in rutileTiO2(110)

Site-specific photocatalytic splitting of methanol on TiO2(110)

Kinetics and Dynamics of Photocatalyzed Dissociation of Ethanol on TiO2(110)

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