Unique Effects of Iron(III) Ions on Photocatalytic and Photoelectrochemical Properties of Titanium Dioxide

Ohno, Teruhisa; Haga, Daisuke; Fujihara, Kan; Kaizaki, Kaoru; Matsumura, Michio

doi:10.1021/jp973358z

Cited by 25 publications

(21 citation statements)

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“…In the absence of 2-propanol, the production of hydrogen peroxide was also negligible, indicating that the net reaction proceeds only slightly on photoirradiated TiO 2 in the absence of electron donors. This finding is consistent with the fact that the oxidation of water on photoirradiated TiO 2 particles is very inefficient without the use of strong electron acceptors [30,31]. It should also be noted that when the irradiation time was shorter than 3 min, the production rate of acetone on photoirradiated TiO 2 powders was only slightly affected by the addition of NBT.…”

Section: Qualitative Analysis Of the Production Of Superoxide Ionsupporting

confidence: 87%

“…Rutile powders are also important for some photocatalytic reactions in which strong electron acceptors are used in place of molecular oxygen. For example, when Fe 3+ ion is added to the reaction solution, rutile particles show very high photocatalytic activity and oxidize some compounds, which cannot be photocatalytically oxidized on anatase particles [30].…”

Section: Discussionmentioning

confidence: 99%

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Quantitative analysis of superoxide ion and hydrogen peroxide produced from molecular oxygen on photoirradiated TiO2 particles

Goto

Hanada

Ohno

et al. 2004

Journal of Catalysis

295

106

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Section: Qualitative Analysis Of the Production Of Superoxide Ionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Quantitative analysis of superoxide ion and hydrogen peroxide produced from molecular oxygen on photoirradiated TiO2 particles

Goto

Hanada

Ohno

et al. 2004

Journal of Catalysis

295

106

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“…One way to check whether the metal is required as an electron trap in photocatalysis is to eliminate it altogether from the photocatalyst and to assess if any photocatalytic activity is maintained. The H 2 production reaction cannot be used to test this directly because the metal is also needed for H atom recombination, but a different reducible ion can be used instead (26)(27)(28). Based on the current model described in Fig.…”

Section: Significancementioning

confidence: 99%

Promotion of atomic hydrogen recombination as an alternative to electron trapping for the role of metals in the photocatalytic production of H ₂

Joo

Dillon

Lee

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

116

113

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The production of hydrogen from water with semiconductor photocatalysts can be promoted by adding small amounts of metals to their surfaces. The resulting enhancement in photocatalytic activity is commonly attributed to a fast transfer of the excited electrons generated by photon absorption from the semiconductor to the metal, a step that prevents deexcitation back to the ground electronic state. Here we provide experimental evidence that suggests an alternative pathway that does not involve electron transfer to the metal but requires it to act as a catalyst for the recombination of the hydrogen atoms made via the reduction of protons on the surface of the semiconductor instead.photocatalysis | hydrogen production | gold-titania | time-resolved fluorescence | core-shell nanostructures P hotocatalysis is a promising technology to address problems in chemical synthesis (1), environmental remediation (2, 3), and energy utilization (4). The potential for harvesting solar energy and storing it as a chemical fuel using photocatalysts is particularly appealing. Specifically, H 2 may be produced via water splitting this way (5-7). In fact, many photocatalysts have been reported already capable of producing hydrogen out of water, even if none of those are yet commercially viable. Such photocatalysis rely on capturing photon energy via excitation of electrons from the valence band to the conduction band of appropriate semiconductors such as titania, which is often cited as a prototypical example (8-10), creating an excited electron-hole pair that is then used to promote redox reactions (11,12). However, for the photocatalysts to be useful, the lifetime of the electron-hole pair needs to be long enough to be accessible for chemical conversions. The search for photocatalytic systems that fulfill this and other key requirements continues, and would be greatly facilitated by a clearer understanding of the underlying chemical process.It is well known that the addition of metals such as platinum or gold to semiconductors enhances their activity as photocatalysts, in particular for water splitting to produce H 2 (13-15). This effect is currently explained by a mechanism where the excited electrons produced by absorption of light are transferred from the semiconductor to the metal before they have the opportunity to recombine with their corresponding holes and return to the ground electronic state (Fig. 1A) (16-18). In this scheme, the protons from water are reduced on the surface of the metal, in sites physically separated from those on the semiconductor, where oxygen production takes place. Here we present evidence that challenges this conventional explanation, and offer an alternative mechanism for the promotion of photocatalysis by metals. Specifically, using the Au/TiO 2 metal-semiconductor pair as a model system, we show that electron transfer to the metal may not play a significant role in photocatalysis. Instead, the data support a model where the excited electron promotes the reduction of protons on the surface of the se...

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“…The values of the initial degradation and mineralization rates in Table 1 demonstrate that in the presence of 0.5 g L −1 TiO 2 P25, TiO 2 UV-100 and TiO 2 Kronos uvlp 7500, the introduction of 1.75 mg L −1 Fe 3+ accelerates the photocatalytic process. Indeed, addition of ferric ions into the TiO 2 slurry reduces the recombination rate of the photogenerated electrons [Eqn (5)], whereas it simultaneously increases the concentration of the HO • radicals produced 45,46 . Electron trapping by Fe 3+ acts positively on this synergy because these species are easily reduced on the TiO 2 surface 47,48 .…”

Section: Effect Of Electron Scavengersmentioning

confidence: 99%

Decomposition and detoxification of the insecticide thiacloprid by TiO₂‐mediated photocatalysis: kinetics, intermediate products and transformation pathways

Berberidou

Kitsiou

Lambropoulou

et al. 2019

J of Chemical Tech & Biotech

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BACKGROUND: Pesticides are listed among the main environmental stressors directly correlated with severe impacts on ecosystems and human health. Here, the potential of TiO 2 -mediated photocatalytic oxidation of the insecticide thiacloprid, in aqueous media, is investigated thoroughly. RESULTS: Degradation was investigated under various operational conditions, including the initial concentration of the pesticide, the type and amount of catalyst, pH and the presence of electron acceptors. The prevalence of TiO 2 P25 in comparisonto the other titania employed, is obvious both in the case of decomposition and carbon mineralization. Twenty-seven transformation products generated during the photocatalytic decomposition of thiacloprid under UV-A irradiation were elucidated by high-resolution liquid chromatography mass spectrometry analysis, enabling the proposition of potential fragmentation pathways. The initial ecotoxicity of the insecticide determined by measurements of the bioluminescence of marine bacteria Vibrio fischeri was eliminated within 240 min of UV-A irradiation in the presence of TiO 2 P25. A phytotoxicity evaluation based on three eukaryotic plant species led to similar conclusions, resulting in the complete removal of phytotoxicity within 240 min of UV-A illumination in the presence of TiO 2 P25. CONCLUSIONS: These findings suggest that TiO 2 -mediated photocatalytic oxidation has the potential to efficiently detoxify water containing neonicotinoid pesticides.

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Unique Effects of Iron(III) Ions on Photocatalytic and Photoelectrochemical Properties of Titanium Dioxide

Cited by 25 publications

References 0 publications

Quantitative analysis of superoxide ion and hydrogen peroxide produced from molecular oxygen on photoirradiated TiO2 particles

Quantitative analysis of superoxide ion and hydrogen peroxide produced from molecular oxygen on photoirradiated TiO2 particles

Promotion of atomic hydrogen recombination as an alternative to electron trapping for the role of metals in the photocatalytic production of H ₂

Decomposition and detoxification of the insecticide thiacloprid by TiO₂‐mediated photocatalysis: kinetics, intermediate products and transformation pathways

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Unique Effects of Iron(III) Ions on Photocatalytic and Photoelectrochemical Properties of Titanium Dioxide

Cited by 25 publications

References 0 publications

Quantitative analysis of superoxide ion and hydrogen peroxide produced from molecular oxygen on photoirradiated TiO2 particles

Quantitative analysis of superoxide ion and hydrogen peroxide produced from molecular oxygen on photoirradiated TiO2 particles

Promotion of atomic hydrogen recombination as an alternative to electron trapping for the role of metals in the photocatalytic production of H 2

Decomposition and detoxification of the insecticide thiacloprid by TiO2‐mediated photocatalysis: kinetics, intermediate products and transformation pathways

Contact Info

Product

Resources

About

Promotion of atomic hydrogen recombination as an alternative to electron trapping for the role of metals in the photocatalytic production of H ₂

Decomposition and detoxification of the insecticide thiacloprid by TiO₂‐mediated photocatalysis: kinetics, intermediate products and transformation pathways