Effect of Hydrogen on O<sub>2</sub> Adsorption and Dissociation on a TiO<sub>2</sub> Anatase (001) Surface

Liu, Liangliang; Wang, Zhu; Pan, Chunxu; Xiao, Wei; Cho, Kyeongjae

doi:10.1002/cphc.201201048

Cited by 13 publications

(13 citation statements)

References 70 publications

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“…The dissociation of H 2 on the Au 7 cluster is an exothermic process (ΔE = −0.18 eV) with a barrier of 0.19 eV. Next, when a dissociated H atom reacts with O 2 , the energy is high enough to break the O−O bond without the generation of OOH, because the O−O bond is extremely activated (1.46 Å) when O 2 adsorbs at the oxygen vacancy site, and can be broken with a very low energy, which is consistent with the work of Liu et al 59 The O2 atom fills the oxygen vacancy, and the OH group formed by O1 and H adsorbs at the interface to form a stable Au−OH−Ti structure. The barrier and reaction energy of this process are 0.71 and −3.23 eV, respectively.…”

Section: Resultssupporting

confidence: 87%

Theoretical Insights into Propene Epoxidation on Au₇/Anatase TiO_2–x(001) Catalysts: Effect of the Interface and Reaction Atmosphere

Zhang¹,

Zhao²,

Yang

et al. 2019

J. Phys. Chem. C

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Interfacial synergy of metal/oxide catalysts has been extensively studied in heterogeneous catalysis but elucidating the synergy mechanism and controlling the interfacial structure remain challenging. Herein, the effect of interface and reaction atmosphere on propene epoxidation on Au 7 /anatase TiO 2−x (001) catalysts is studied using density functional theory calculations. The results indicate that propene epoxidation occurs on the topmost Au atoms on a perfect Au 7 /TiO 2 (001) catalyst. Propene epoxidation with O 2 alone has a higher barrier and reaction energy, whereas in the presence of H 2 , the hydrogenation of O 2 to OOH is a feasible pathway for propene epoxidation from both kinetic and thermodynamic viewpoints. On defective Au 7 /TiO 2−x (001)-V O catalysts, oxygen vacancy regulates the geometric/electronic structures of interfacial sites, and propene epoxidation instead occurs at the interface of Au 7 and TiO 2−x (001)-V O . Under O 2 atmosphere, O atom fills the oxygen vacancy and significantly reduces the energy of the entire catalytic system; however, this has little effect on the kinetics of epoxidation. An O 2 −H 2 mixture results in the lowest barrier owing to the activation of the O−O bond and interfacial synergy. Our results suggest that the moderate and rational regulation of oxygen vacancy on the oxide surface can provide highly active sites and better interfacial synergy for propene epoxidation and highlight the essential role of the reaction atmosphere, which can be utilized to design high-efficiency heterogeneous catalysts.

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Section: Resultssupporting

confidence: 87%

Theoretical Insights into Propene Epoxidation on Au₇/Anatase TiO_2–x(001) Catalysts: Effect of the Interface and Reaction Atmosphere

Zhang¹,

Zhao²,

Yang

et al. 2019

J. Phys. Chem. C

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“…3A in 2nd column). Theoretically, the dissociation barrier for the surface peroxides into Ti–O • pairs on the {001} facet of anatase TiO 2 is 1.0–1.4 eV, which can be overcome by the photon energy available from UV and visible light irradiation 43 : …”

Section: Resultsmentioning

confidence: 99%

Efficient and selective photocatalytic CH4 conversion to CH3OH with O2 by controlling overoxidation on TiO2

et al. 2021

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The conversion of photocatalytic methane into methanol in high yield with selectivity remains a huge challenge due to unavoidable overoxidation. Here, the photocatalytic oxidation of CH4 into CH3OH by O2 is carried out on Ag-decorated facet-dominated TiO2. The {001}-dominated TiO2 shows a durable CH3OH yield of 4.8 mmol g−1 h−1 and a selectivity of approximately 80%, which represent much higher values than those reported in recent studies and are better than those obtained for {101}-dominated TiO2. Operando Fourier transform infrared spectroscopy, electron spin resonance, and nuclear magnetic resonance techniques are used to comprehensively clarify the underlying mechanism. The straightforward generation of oxygen vacancies on {001} by photoinduced holes plays a key role in avoiding the formation of •CH3 and •OH, which are the main factors leading to overoxidation and are generally formed on the {101} facet. The generation of oxygen vacancies on {001} results in distinct intermediates and reaction pathways (oxygen vacancy → Ti–O2• → Ti–OO–Ti and Ti–(OO) → Ti–O• pairs), thus achieving high selectivity and yield for CH4 photooxidation into CH3OH.

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“…Titanium oxide (TiO 2 ) has been widely used in numerous fields, from everyday applications (paint, inks, toothpaste, makeup) to technological devices, such as dye-sensitized solar cells (DSSCs) [1,2], photoelectrochemical cells [3], photocatalysts [4], catalysis [5,6], sensors [7,8], biomedical treatments [9], lithium ion batteries [10], or photovoltaics [11,12]. The interaction of hydrogen with TiO 2 surfaces plays an important role in many reaction processes [13,14,15,16,17,18,19,20] and has been widely studied [21,22,23,24,25,26,27]. Despite the high interest generated by hydrogen-titania interfaces, the nature of the species involved is still poorly understood—protons are generally reported as being stable in hydrogenated rutile (110) [28], atomic surface hydrogen has been found to prevent electron-hole recombination on an Au-TiO 2 photocatalyst [14], and very recently hydride species have been characterized as being stable on its surface [29,30].…”

Section: Introductionmentioning

confidence: 99%

Understanding the Role of Rutile TiO2 Surface Orientation on Molecular Hydrogen Activation

2019

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Titanium oxide (TiO2) has been widely used in many fields, such as photocatalysis, photovoltaics, catalysis, and sensors, where its interaction with molecular H2 with TiO2 surface plays an important role. However, the activation of hydrogen over rutile TiO2 surfaces has not been systematically studied regarding the surface termination dependence. In this work, we use density functional theory (PBE+U) to identify the pathways for two processes: the heterolytic dissociation of H2 as a hydride–proton pair, and the subsequent H transfer from Ti to near O accompanied by reduction of the Ti sites. Four stoichiometric surface orientations were considered: (001), (100), (110), and (101). The lowest activation barriers are found for hydrogen dissociation on (001) and (110), with energies of 0.56 eV and 0.50 eV, respectively. The highest activation barriers are found on (100) and (101), with energies of 1.08 eV and 0.79 eV, respectively. For hydrogen transfer from Ti to near O, the activation barriers are higher (from 1.40 to 1.86 eV). Our results indicate that the dissociation step is kinetically more favorable than the H transfer process, although the latter is thermodynamically more favorable. We discuss the implications in the stability of the hydride–proton pair, and provide structures, electronic structure, vibrational analysis, and temperature effects to characterize the reactivity of the four TiO2 orientations.

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Effect of Hydrogen on O₂ Adsorption and Dissociation on a TiO₂ Anatase (001) Surface

Cited by 13 publications

References 70 publications

Theoretical Insights into Propene Epoxidation on Au₇/Anatase TiO_2–x(001) Catalysts: Effect of the Interface and Reaction Atmosphere

Theoretical Insights into Propene Epoxidation on Au₇/Anatase TiO_2–x(001) Catalysts: Effect of the Interface and Reaction Atmosphere

Efficient and selective photocatalytic CH4 conversion to CH3OH with O2 by controlling overoxidation on TiO2

Understanding the Role of Rutile TiO2 Surface Orientation on Molecular Hydrogen Activation

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Effect of Hydrogen on O2 Adsorption and Dissociation on a TiO2 Anatase (001) Surface

Cited by 13 publications

References 70 publications

Theoretical Insights into Propene Epoxidation on Au7/Anatase TiO2–x(001) Catalysts: Effect of the Interface and Reaction Atmosphere

Theoretical Insights into Propene Epoxidation on Au7/Anatase TiO2–x(001) Catalysts: Effect of the Interface and Reaction Atmosphere

Efficient and selective photocatalytic CH4 conversion to CH3OH with O2 by controlling overoxidation on TiO2

Understanding the Role of Rutile TiO2 Surface Orientation on Molecular Hydrogen Activation

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Effect of Hydrogen on O₂ Adsorption and Dissociation on a TiO₂ Anatase (001) Surface

Theoretical Insights into Propene Epoxidation on Au₇/Anatase TiO_2–x(001) Catalysts: Effect of the Interface and Reaction Atmosphere

Theoretical Insights into Propene Epoxidation on Au₇/Anatase TiO_2–x(001) Catalysts: Effect of the Interface and Reaction Atmosphere