DRIFTS investigation and DFT calculation of the adsorption of CO on Pt/TiO2, Pt/CeO2 and FeOx/Pt/CeO2

Gao, Hongwei; Xu, Wenqing; He, Hong; Shi, Xun; Zhang, Xiuli; Tanaka, Kenichi

doi:10.1016/j.saa.2008.03.036

Cited by 29 publications

(16 citation statements)

References 21 publications

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“…13 The bands detected at 2050 cm -1 during UV irradiation have previously been assigned in the literature to CO on Pt in the "ontop" position. 14,15 Surprisingly, unlike the case of pure water, the band at 1426 cm -1 assigned to δ (CHO) was shifted to a lower frequency (1415 cm -1 ), whereas the bands at 1580 cm -1 and 1342 cm -1 , assigned to asymmetric νasy (COO−) and symmetric νsy (COO−) stretching vibrations, shifted…”

Section: Resultsmentioning

confidence: 88%

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Mechanisms of Simultaneous Hydrogen Production and Formaldehyde Oxidation in H₂O and D₂O over Platinized TiO₂

et al. 2017

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The simultaneous photocatalytic degradation of formaldehyde and hydrogen evolution on platinized TiO2 have been investigated employing different H2O/D2O mixtures under oxygen-free conditions using quadrupole mass spectrometery (QMS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The main reaction products obtained from the photocatalytic oxidation of 20% formaldehyde were hydrogen and carbon dioxide. The ratio of evolved H2 to CO2 was to 2/1. The HD gas yield was found to be dependent on the solvent and was maximized in a H2O/D2O mixture (20%/80%). The study of the solvent isotope effect on the degradation of formaldehyde indicates that the mineralization rate of formaldehyde (CO2) decreases considerably when the concentration of D2O is increased. On the basis of the ATR-FTIR data, the formaldehyde in D2O is gradually converted to deuterated formic acid during UV irradiation, which was confirmed by different band shifting. An additional FTIR band at 2050 cm–1 assigned to CO was detected and was found to increase during UV irradiation due to the adsorption of molecular CO on Pt/TiO2. The results of these investigations showed that the molecular hydrogen is mainly produced by the reduction of two protons originating from water and formaldehyde. A detailed mechanism for the simultaneous hydrogen production and formaldehyde oxidation in D2O is also presented.

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Section: Resultsmentioning

confidence: 88%

“…22 Moreover, the band observed at 2050 cm -1 during UV irradiation was assigned to the CO adsorbed on Pt in the "on-top" position. 14 Two different sources for CO gas formation can be explained by decarbonylation of formaldehyde or/and dehydration of formic acid. 26,27 Since the evolution rate of H2 (54 µmol h -1…”

Section: Discussionmentioning

confidence: 99%

Mechanisms of Simultaneous Hydrogen Production and Formaldehyde Oxidation in H₂O and D₂O over Platinized TiO₂

et al. 2017

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“…The ATR-IR spectra of adsorbed CO recorded at 30°C on the two Pt/TiO2 samples ( Fig. 4) exhibit at least four signals in the Pt-CO region (2200-1800 cm -1 ): i) a weak and broad signal at 2180 cm -1 attributed to CO adsorbed on Ti 4+ cations [27]; ii) bands at 2070 cm -1 and iii) 2054 cm -1 attributed to adsorbed CO on Pt atoms located at terrace and edge sites, respectively [28,29]; iv) a broad and weaker signal at 1820 cm -1 due to bridge adsorbed CO on the Pt-Pt and Pt-Ti sites [30]. As shown in Fig.…”

Section: Co Adsorptionmentioning

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

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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.

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“…2a was the growth of a band at $2050 cm À1 characteristic of CO adsorbed on metallic Pt nanoparticles. [66][67][68] Expanding the region of interest for clarity (Fig. 2b) shows the main band characteristic of CO adsorbed on Pt in the ''on-top'' position, initially at $2030 cm À1 but shifting progressively to higher frequency due to well-known coverage-dependent dipolar coupling effects.…”

Section: Photo-metallizationmentioning

confidence: 99%

Mechanistic investigations of photo-driven processes over TiO2 by in-situ DRIFTS-MS: Part 1. Platinization and methanol reforming

Highfield

Chen

Nguyen³

et al. 2009

Energy Environ. Sci.

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There is growing interest in the reforming of methanol and other bio-oxygenates as highdensity, CO 2 -neutral, renewable sources of H 2 . Photocatalysis is worthy of investigation as a potentially economic means to drive such endothermic processes. In this study, in-situ DRIFTS, adapted for optical pumping and coupled to on-line MS, was used to observe the surface of TiO 2 (Degussa P25) during photo-metallization from pre-sorbed hexachloroplatinate, at a nominal Pt loading of 1 wt%, and to evaluate photo-reforming of methanol over the resulting Pt/TiO 2 composite. The irreversible growth of a quasi-continuum absorption, characteristic of the surface plasmon resonance of zerovalent Pt nanoparticles, along with bands at 2050 and 1830 cm -1 typical of metal-adsorbed CO, indicated that photometallization was complete typically within 2 hours. Methanol reforming was photocatalyzed at room temperature but in low quantum efficiency, ø ≈ 0.01. However, this was raised substantially, to ø ≈ 0.07, simply by the application of mild heating (T ≤ 70 ºC). Photoreforming proceeded at a fixed rate but the H 2 /CO 2 ratio generally exceeded that of the reforming stoichiometry, suggesting some retention of CO 2 . The photo-thermal synergy was rationalized by model DRIFTS studies, starting from formalin (hydrated formaldehyde), which revealed key features of the mechanism. TiO 2 promoted the Cannizzaro disproportionation in the dark, yielding formate and methoxy species already at 40 ºC. While methoxy was effectively cycled back to the initial photo-dehydrogenation stage, the slow step was identified as formate decomposition to H 2 and CO 2 . The low value measured for the apparent activation energy (~40 kJ mol -1 ) was taken as supporting evidence for 'waterassisted destabilization' of formate, as originally reported by Shido and Iwasawa. No evidence was found for an alternative thermal or photo-reforming mechanism involving the Pt-CO ad species.

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DRIFTS investigation and DFT calculation of the adsorption of CO on Pt/TiO2, Pt/CeO2 and FeOx/Pt/CeO2

Cited by 29 publications

References 21 publications

Mechanisms of Simultaneous Hydrogen Production and Formaldehyde Oxidation in H₂O and D₂O over Platinized TiO₂

Mechanisms of Simultaneous Hydrogen Production and Formaldehyde Oxidation in H₂O and D₂O over Platinized TiO₂

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

Mechanistic investigations of photo-driven processes over TiO2 by in-situ DRIFTS-MS: Part 1. Platinization and methanol reforming

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DRIFTS investigation and DFT calculation of the adsorption of CO on Pt/TiO2, Pt/CeO2 and FeOx/Pt/CeO2

Cited by 29 publications

References 21 publications

Mechanisms of Simultaneous Hydrogen Production and Formaldehyde Oxidation in H2O and D2O over Platinized TiO2

Mechanisms of Simultaneous Hydrogen Production and Formaldehyde Oxidation in H2O and D2O over Platinized TiO2

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

Mechanistic investigations of photo-driven processes over TiO2 by in-situ DRIFTS-MS: Part 1. Platinization and methanol reforming

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Mechanisms of Simultaneous Hydrogen Production and Formaldehyde Oxidation in H₂O and D₂O over Platinized TiO₂

Mechanisms of Simultaneous Hydrogen Production and Formaldehyde Oxidation in H₂O and D₂O over Platinized TiO₂