Photo-generated conduction-band and shallow-trap electrons from UV irradiation on ethanol-adsorbed TiO2 and N-TiO2: an in situ infrared study

Liu, Jiawei; Zhang, Long; Yao, Xuesi; Chuang, Steven S. C.

doi:10.1007/s11164-017-3038-9

Cited by 11 publications

(12 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…10). This absorption shift is attributed to the formation of both photopromoted conduction band (CB) and shallow trapped (ST) electrons [8,[16][17][18]. In particular, CB electrons provoke a distinct exponential absorption growth of the IR baseline while ST electrons give rise to broad bands due to the optical excitation of electrons from the ST states into the CB.…”

Section: Effect Of Uv-vis Irradiation On Pre-adsorbed Methanol In Thementioning

confidence: 99%

“…Infrared spectroscopy has been widely used to study the interactions of methanol and water with the TiO2 surface [6][7][8][9][10] and to provide information on the photoreaction mechanism [10][11][12][13][14][15]. In addition to the detection of surface species formed during the photoreaction, time resolved FT-IR spectroscopy proved to be a powerful tool to distinguish between photopromoted free CB electrons and shallow trapped (ST) electrons and to evaluate their lifetime [8,[16][17][18].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

In situ attenuated total reflection infrared spectroscopy study of the photocatalytic steam reforming of methanol on Pt/TiO2

Chiarello

Ferri

Selli

2018

Applied Surface Science

View full text Add to dashboard Cite

The effect of Pt deposition on TiO2 and of Pt particle size on the photocatalytic steam reforming of methanol was studied by in-situ attenuated total reflectance infrared spectroscopy (ATR-IR). Two 0.5 wt.% Pt/TiO2 samples were investigated, one possessing Pt nanoparticles of ca. 4 nm mean size, the other Pt clusters of ca. 1.3 nm mean size showing significantly different photoactivity in terms of both hydrogen production rate and selectivity to CO, CO2 and all other by-products. The presence of Pt nanoparticles strongly affects both the adsorption/desorption and the reactivity properties of the TiO2 surface. Moreover, the variation of the IR spectrum background upon UV-vis irradiation proved that the photopromoted electrons can be trapped by the Pt particles with the consequent increasing of electron-hole separation. Reducing the Pt size from nanoparticles to clusters increases the rate of methanol and water absorption and hinders the detrimental formation of irreversibly adsorbed CO on Pt. All of these aspects contribute to increase the photocatalytic performance of Pt cluster-decorated TiO2 with respect to Pt nanoparticles containing TiO2. Finally, prolonged exposure of all samples to methanol/water vapour in the dark led to the formation of unreactive formate which persists also under UV-vis irradiation. By contrast, this spectator species does not form when the sample is exposed to methanol/water vapour under UV-vis irradiation.

show abstract

Section: Effect Of Uv-vis Irradiation On Pre-adsorbed Methanol In Thementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

In situ attenuated total reflection infrared spectroscopy study of the photocatalytic steam reforming of methanol on Pt/TiO2

Chiarello

Ferri

Selli

2018

Applied Surface Science

View full text Add to dashboard Cite

show abstract

“…As to strategy (1) doping with metal [37,38,39,40] and non-metals [41,42,43] has been attempted, as well as surface modification by anchoring dye molecules [44,45,46], quantum dots [36,47], metal nanoparticles [36,47,48,49,50] or also halides species [29].…”

Section: Heterostructures At Tio2 Surface As Organic and Inorganic Sementioning

confidence: 99%

Molecules and heterostructures at TiO2 surface: the cases of H2O, CO2, and organic and inorganic sensitizers

et al. 2019

View full text Add to dashboard Cite

TiO2-based (nano)materials are widely exploited in systems and devices of actual technological interest, because of their outstanding physical and chemical properties, including chemical stability, long durability, non-toxicity abundance and low cost. For this, they are considered ideal for many practical applications including energy-related devices, photocatalysis, but are known to have some limitations. To improve their performance and then to find more efficient materials in the energy and environmental remediation fields, at first the investigation of the surface/interface properties at the molecular scale is required. In this contribution, a critical review of advances in the field of the TiO2 surface chemistry, highlighting the role of interactions at the molecular level, grafting and assembling/fabrication of suitable heterostructures, is reported. A few case studies, from the H2O, CO2 and acetylene interactions until to the grafting of organic/inorganic systems (graphene, MoS2) at the TiO2 surface, are highlighted. The discussed case studies are argued from their principles to the technological relevance. KeywordsTiO2 photocatalysis H2O, CO2 and C2H2 adsorption Graphene and MoS2/TiO2 hybrids Surface heterostructures IR spectroscopy STM and AFM HR-TEM Electronic spectroscopy Quantum modelling Preliminary remarks: motivation and structure of this review Particles and nanoparticles resulting from the combination of titanium, the second transition element more common in Earth's crust after iron, with oxygen to form TiO2, mainly in the anatase and rutile phases, are used in a wide array of products, devices and technologies. As reported by the Titanium Dioxide Manufacturers Associations (TDMA, https://tdma.info), gathering since 1974 the major producers of this material in Europe, the commercial and research area representing the "first coordination sphere" of the authors of this review, application for TiO2 across the EU, as well as across the globe, include paints, papers, pharmaceuticals, sunscreen and food (where it is listed as colourant E171). As a photocatalyst, titanium dioxide can be added to paints, cements, windows and tiles in order to decompose environmental pollutants, and as a white pigment (in this case called titanium white, Pigment White 6 or CI 77891), TiO2 is one of the most important raw materials for paints and coatings. Moreover, the range of innovative uses for TiO2 keeps on increasing. In recent years, for example, it has been used in the manufacture of cheap and efficient solar cells and building facades that can neutralize air pollution.

show abstract

“…However, UV irradiation led to a rising structureless band in 1000−2500 cm −1 , indicating the occurrence of accumulation of photogenerated electrons under UV irradiation. 10,11 The accumulated photogenerated electrons on anatase can be attributed to the breaking of the C−H bond at 2927 cm −1 , which proceeds through the steps shown in eq 1:…”

Section: Organic Process Research and Developmentmentioning

confidence: 99%

“…The structureless band is a result of the accumulation of photogenerated electrons at shallow levels and in the conduction band. 10,11 The distribution of e − in the conduction band and shallow levels can be estimated by fitting the IR profiles to simulated models of electrons (e CB − and e ST − ). 10,11 The fitting results showed that L-Lys/P-25 produced over 80% of the photogenerated electrons in the conduction band whereas Lys/anatase produced less than 40% in the conduction band.…”

Section: Organic Process Research and Developmentmentioning

confidence: 99%

Photocatalytic Synthesis of Pipecolic Acid from Lysine on TiO₂: Effects of the Structure of Catalysts and Adsorbed Species on Chiral Selectivity

Zhai

Chuang

2018

Org. Process Res. Dev.

Self Cite

View full text Add to dashboard Cite

A one-step photocatalytic synthesis of l-pipecolic acid (l-PCA) from l-lysine (l-Lys) has been investigated by in situ infrared (IR), circular dichroism, and 1H NMR spectroscopy. Chiral selectivity toward l-Lys was found to be governed by the structure of adsorbed l-Lys and the structure of TiO2. Both anatase and rutile were not able to catalyze the reaction in a solvent-free environment. In situ IR studies revealed that l-Lys adsorbed on these TiO2 in a dicationic form of which the positive −NH3 + functional groups are not able to interact with photogenerated holes. Interestingly, P-25 TiO2, which contains 80 wt % anatase and 20 wt % rutile, adsorbs l-Lys in a zwitterionic form, allowing its hydrogen in the α-amino group to be abstracted by the photogenerated hole, producing racemic PCA. The addition of H2O as a solvent allowed l-Lys to be adsorbed on P-25 in an anionic form, producing l-PCA as a major product. This study demonstrates that the reaction environment has a direct impact on the structure of adsorbed species that controls the selectivity of a chiral synthesis.

show abstract

Photo-generated conduction-band and shallow-trap electrons from UV irradiation on ethanol-adsorbed TiO2 and N-TiO2: an in situ infrared study

Cited by 11 publications

References 26 publications

In situ attenuated total reflection infrared spectroscopy study of the photocatalytic steam reforming of methanol on Pt/TiO2

In situ attenuated total reflection infrared spectroscopy study of the photocatalytic steam reforming of methanol on Pt/TiO2

Molecules and heterostructures at TiO2 surface: the cases of H2O, CO2, and organic and inorganic sensitizers

Photocatalytic Synthesis of Pipecolic Acid from Lysine on TiO₂: Effects of the Structure of Catalysts and Adsorbed Species on Chiral Selectivity

Contact Info

Product

Resources

About

Photo-generated conduction-band and shallow-trap electrons from UV irradiation on ethanol-adsorbed TiO2 and N-TiO2: an in situ infrared study

Cited by 11 publications

References 26 publications

In situ attenuated total reflection infrared spectroscopy study of the photocatalytic steam reforming of methanol on Pt/TiO2

In situ attenuated total reflection infrared spectroscopy study of the photocatalytic steam reforming of methanol on Pt/TiO2

Molecules and heterostructures at TiO2 surface: the cases of H2O, CO2, and organic and inorganic sensitizers

Photocatalytic Synthesis of Pipecolic Acid from Lysine on TiO2: Effects of the Structure of Catalysts and Adsorbed Species on Chiral Selectivity

Contact Info

Product

Resources

About

Photocatalytic Synthesis of Pipecolic Acid from Lysine on TiO₂: Effects of the Structure of Catalysts and Adsorbed Species on Chiral Selectivity