Studies on the photocatalytic hydrogen production using suspended modified photocatalysts

Nada, Amr A.; Barakat, M.H.; Hamed, Hamid; Mohamed, N.R.; Везироглу, Т. Н.

doi:10.1016/j.ijhydene.2004.06.007

Cited by 191 publications

(94 citation statements)

References 20 publications

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“…The efficient interface electrons transfer inhibits the quick recombination of the photogenerated electronhole pairs on SnO 2 surface, leading to enhancement of photocatalytic activity of NiO/SnO 2 composites. There exists an optimal amount when noble metals or metal oxides are loaded on TiO 2 surface [26][27][28]. Similar dependence has been observed when the NiO is loaded on the SnO 2 surface.…”

Section: Effect Of Nio Content On Photocatalytic Oxidation Ofsupporting

confidence: 62%

Photocatalytic Oxidation of Carbon Monoxide over Nanocomposites under UV Irradiation

Mohamed

Aazam

2012

Journal of Nanotechnology

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The NiO/SnO 2 nanocomposites have been prepared by the simple coprecipitation method and further characterized by the XRD, SEM, TEM, UV-Vis, and BET. X-ray diffraction (XRD) data analyses indicate the exclusive formation of nanosized particles with rutile-type phase (tetragonal SnO 2 ) for Ni contents below 10 mol%. Only above 10 mol% Ni, the formation of a second NiOrelated phase has been determined. The particle size is in the range from 12 to 6 nm. It decreases with increasing amounts of doping NiO. The morphology of NiO-doped SnO 2 nanocrystalline powders is spherical, and the distribution of particle size is uniform, as seen from transmission electron microscopy (TEM). The photocatalytic oxidation of CO over NiO/SnO 2 photocatalyst has been investigated under UV irradiation. Effects of NiO loading on SnO 2 , photocatalyst loading, and reaction time on photocatalytic oxidation of CO have been systematically studied. Compared with pure SnO 2 , the 33.3 mol% NiO/SnO 2 composite exhibited approximately twentyfold enhancement of photocatalytic oxidation of CO. Our results provide a method for pollutants removal. Due to simple preparation, high photocatalytic oxidation of CO, and low cost, the NiO/SnO 2 photocatalyst will find wide application in the coming future of photocatalytic oxidation of CO.

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Section: Effect Of Nio Content On Photocatalytic Oxidation Ofsupporting

confidence: 62%

Photocatalytic Oxidation of Carbon Monoxide over Nanocomposites under UV Irradiation

Mohamed

Aazam

2012

Journal of Nanotechnology

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“…An alternative approach to elucidate the mechanism of watersplitting photocatalysis is to focus on the H 2 production, which can be facilitated via the addition of an easy-to-oxidize sacrificial agent such as methanol to the solution (to bypass the O 2 production half reaction) (18,32). For this, the metal may be replaced with another element capable of performing only one of the two functions being considered in this discussion, namely, electron trapping or atomic-hydrogen recombination.…”

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.

110

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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“…Similar to photo-fermentation where enzyme is used to catalyze the conversion, solar energy is again utilized to offer sufficient power to produce hydrogen from ethanol under the facilitation of inorganic catalyst. Among many catalysts documented in the literature, TiO 2 [8][9][10] is the most commonly used catalyst base due to its excellent photoreactivity which has a suitable band gap for efficient light photon absorption. Upon radiation, the electron contained in a semiconductor such as TiO 2 will be excited and transferred from valence band to conduction band, resulting in the creation of an electron-hole pair and in turn providing an active site for redox reaction.…”

Section: Photocatalytic Hydrogen Productionmentioning

confidence: 99%

Catalytic Hydrogen Production from Bioethanol

Song

2017

Hydrogen Production Technologies

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Studies on the photocatalytic hydrogen production using suspended modified photocatalysts

Cited by 191 publications

References 20 publications

Photocatalytic Oxidation of Carbon Monoxide over Nanocomposites under UV Irradiation

Photocatalytic Oxidation of Carbon Monoxide over Nanocomposites under UV Irradiation

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

Catalytic Hydrogen Production from Bioethanol

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Studies on the photocatalytic hydrogen production using suspended modified photocatalysts

Cited by 191 publications

References 20 publications

Photocatalytic Oxidation of Carbon Monoxide over Nanocomposites under UV Irradiation

Photocatalytic Oxidation of Carbon Monoxide over Nanocomposites under UV Irradiation

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

Catalytic Hydrogen Production from Bioethanol

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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