New insight into the structure of dispersed titania by combining normal-mode analysis with experiment

Nitsche, David; Heß, Christian

doi:10.1016/j.cplett.2014.10.042

Cited by 5 publications

(4 citation statements)

References 33 publications

(53 reference statements)

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“…By combining theory and experiment (see Figure ), the Raman feature at 945 cm –1 can be assigned to an interphase Ti–O–Si vibration and the feature at 1085 cm –1 to either an in-phase or out-of-phase Ti–O–Si vibration. As pointed out previously, it is not possible to discriminate between the in-phase and out-of-phase Ti–O–Si modes due to their spectral proximity. Just like the 1085 cm –1 feature, we attribute the 1150 cm –1 feature to a Ti–O–Si mode.…”

Section: Discussionmentioning

confidence: 96%

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Structure of Isolated Vanadia and Titania: A Deep UV Raman, UV–Vis, and IR Spectroscopic Study

Nitsche

Heß

2016

J. Phys. Chem. C

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Dispersed vanadia and titania are of great interest due to their (photo)catalytic properties. The structure of isolated (highly dispersed) vanadia and titania has been studied using a combination of deep UV Raman, UV–vis, and IR spectroscopy. Highly dispersed vanadia and titania were prepared by incipient wetness impregnation of the corresponding isopropoxide precursors onto silica SBA-15. Using resonance Raman spectroscopy, a wide range of vanadium (0.00001–0.7 V/nm2) and titanium (0.001–0.7 Ti/nm2) loadings can be analyzed. At very low loadings (<0.05 M/nm2) the structure of both highly dispersed vanadia and titania is characterized by tetrahedral coordination of the central atom and anchoring to the support by one or more M–O–S linkages. At higher loadings, titania partly forms oligomeric surface structures according to UV–vis results. In the case of highly dispersed vanadia samples (<0.1 V/nm2), Raman spectroscopy reveals distinct differences in the vanadia surface structures under ambient and dehydrated conditions. Corresponding UV–vis spectra indicate the formation of isolated and oligomeric vanadia surface structures. A smaller dependence of the titania surface structure on the environmental conditions (ambient/dehydrated) was observed. For the 0.7 M/nm2 samples, the presence of hydroxylated vanadia and titania structures in the dehydrated state was verified by IR spectroscopy. The assignment of the vibrational bands was facilitated by the results of a normal-mode analysis using models based on polyhedral oligomeric silsesquioxane (POSS). Our study clearly demonstrates the potential of resonance Raman spectroscopy using 217.5 nm deep UV excitation to study the surface structure of transition metal oxide species even in isolated conditions.

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Section: Discussionmentioning

confidence: 96%

“…Article vibration. As pointed out previously, 59 it is not possible to discriminate between the in-phase and out-of-phase Ti−O−Si modes due to their spectral proximity. Just like the 1085 cm −1 feature, we attribute the 1150 cm −1 feature to a Ti−O−Si mode.…”

Section: ■ Experimental Sectionmentioning

confidence: 96%

Structure of Isolated Vanadia and Titania: A Deep UV Raman, UV–Vis, and IR Spectroscopic Study

Nitsche

Heß

2016

J. Phys. Chem. C

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“…The Raman spectra displayed in Figure show high peaks at 443 and 610 cm –1 for E g and A 1g modes of rutile TiO 2 , respectively, thereby confirming that the predominant TiO 2 crystal structure is rutile. Nevertheless, the peak located between 806 and 836 cm –1 is associated with Ti–OH stretching vibrations, which emerged only after PEC measurements in alkaline electrolytes.…”

Section: Resultsmentioning

confidence: 98%

“…The Raman spectra displayed in Figure 3 show high peaks at 443 and 610 cm −1 for E g and A 1g modes of rutile TiO 2 , 25 respectively, thereby confirming that the predominant TiO 2 crystal structure is rutile. Nevertheless, the peak located between 806 and 836 cm −1 is associated with Ti−OH stretching vibrations, 26 which emerged only after PEC measurements in alkaline electrolytes. Figure 4 depicts the photocurrent density of the TiO 2 nanorod at 1.23 V vs RHE under different electrolyte pH with and without a hole scavenger (0.1 M H 2 O 2 ), which was derived from linear sweep voltammetry under chopped light, shown in Figure S3.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Analysis of an Electrolyte’s pH-Dependent Performance during Solar Water Splitting

Wang,

Yang,

Zhang

et al. 2023

Ind. Eng. Chem. Res.

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The redox reaction is related to the pH of the electrolyte owing to protonation/deprotonation during photoelectrochemical (PEC) water splitting. However, the influence of electrolyte pH on water splitting is not clear, especially the mechanism of the solid–liquid interface mass transfer and carrier transport process under strong acid and alkaline conditions. Herein, a comprehensive series of PEC characterization methods including the linear sweep voltammetry, electrochemical impedance spectroscopy (EIS), Mott–Schottky, and intensity-modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) were deployed to reveal the effect of pH on the carrier transport at the solid–liquid interface layer using TiO2 and Sb2Se3 as the photoanode and photocathode, respectively. Our results indicated that the photocurrent density under alkaline conditions can be as much as six times greater than that under acidic conditions for Sb2Se3, while for the TiO2 photoanode, the photocurrent under strong alkaline conditions was approximately four times greater compared to that under acidic conditions. The relationship between the photocurrent density and electrolyte pH was investigated by injecting acidic and alkaline electrolytes through the electrode surface using a multichannel syringe pump. According to the EIS results, a rise in the pH reduces the impedance of the electrolyte/electrode interface and improves the carrier separation efficiency. Interestingly, the carrier collection efficiency, which is defined by the carrier lifetime and transport time, was enhanced with a rise in electrolyte pH. Our work provides a general approach to identify the relationship between electrolyte pH and carrier dynamics at the electrolyte/electrode interface by electrolyte regulation using a microchannel reactor.

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Ultraviolet (UV) Raman Spectroscopy

Stair

2023

Springer Handbook of Advanced Catalyst Characterization

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New insight into the structure of dispersed titania by combining normal-mode analysis with experiment

Cited by 5 publications

References 33 publications

Structure of Isolated Vanadia and Titania: A Deep UV Raman, UV–Vis, and IR Spectroscopic Study

Structure of Isolated Vanadia and Titania: A Deep UV Raman, UV–Vis, and IR Spectroscopic Study

Analysis of an Electrolyte’s pH-Dependent Performance during Solar Water Splitting

Ultraviolet (UV) Raman Spectroscopy

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