Photoassisted hydrogen production under visible light over NiO/ZnO hetero-system

Belhadi, Akila; Boumaza, S.; Trari, M.

doi:10.1016/j.apenergy.2011.05.044

Cited by 32 publications

(7 citation statements)

References 14 publications

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“…The filled Cu-t 2g level is the highest full valence band (VB), whereas E g forms the CB, and the gap corresponds to d-d transition. For ZnO, a value of 3.26 eV is determined, attributed to the charge transfer (O 2À : 2p → Zn 2+ : 4s) and close to that given elsewhere [18].…”

Section: Optical and Photoelectrochemistry Propertiessupporting

confidence: 83%

Hydrogen evolution under visible light over the heterojunctionp-CuO/n-ZnO prepared by impregnation method

Belhadi

Nadjem

Zaidat

et al. 2015

Int. J. Energy Res.

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The semiconducting properties of the heterojunction CuO/ZnO, synthesized by impregnation method from nitrates, are studied for the first time to assess its feasibility for the hydrogen production under visible light, an issue of energy concern. CuO exhibits a direct optical transition at 1.33 eV, due to Cu 2+ : 3d orbital splitting in octahedral site, and possesses a chemical stability in the pH range (4-14). The Mott-Schottky plot in (Na 2 SO 4 , 0.1 M) medium indicates p-type conduction with a flat band potential of 0.70 V SCE and a holes density of 1.35 × 10 17 cm À3 . As application, hydrogen evolution upon visible light is demonstrated on the heterojunction ×%CuO/ZnO (x = 5, 10 and 20 wt.%). The best performance occurs at pH~12 with an evolution rate of 4.8 cm 3 min À1 (g catalyst) À1 and a quantum yield of 0.12%. The improved activity is attributed to the potential of the conduction band of CuO (À1.34 V SCE ), more negative than that of ZnO, the latter acts as electrons bridge to water molecules. The presence of SO 3 2À reduces the recombination process, thus resulting in more H 2 evolution.

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Section: Optical and Photoelectrochemistry Propertiessupporting

confidence: 83%

Hydrogen evolution under visible light over the heterojunctionp-CuO/n-ZnO prepared by impregnation method

Belhadi

Nadjem

Zaidat

et al. 2015

Int. J. Energy Res.

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“…However, the difference between the O 2 /O 2 •-couple and WS 2 -CB is large for a direct electron exchange and a low activity is expected since the electron transfer should occur iso-energetically. Some strategies have been attempted to overcome such drawback and a growing interest has been paid to hetero-systems [22,23]. As mentioned above, coupled SCs enhance the photocatalytic efficiency by extending the spectral photoresponse toward longer wavelengths and hinder the loss of (e -/h ? )…”

Section: Photocatalysismentioning

confidence: 99%

Photocatalytic degradation of orange II on the novel hetero-system WS2/TiO2 under UV light

Bassaid

Bellal

Trari

2015

Reac Kinet Mech Cat

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The photodegradation of orange II (OII) is successfully achieved on the new hetero-system WS 2 /TiO 2 under UV illumination. The nano sized bi-functional catalyst is prepared by sol gel and calcined at *450°C. The X-ray diffraction shows noticeably broad peaks and TiO 2 is therefore less crystallized with the anatase phase. The sensitizer WS 2 presents a direct optical transition at 1.72 eV. The Mott-Schottky plot (C -2 -V) is characteristic of n type conduction from which a flat band potential of 0.17 V SCE and a donor density of 5.30 9 10 17 cm -3 are determined. An energy band diagram is established, predicting an electron transfer from WS 2 to TiO 2 ; the injection process is confirmed by the photocurrent measurements at different concentrations. Upon increasing the mass of WS 2 , the activity increases and the best performance occurs on 30 % WS 2 /TiO 2 . A conversion of 98 % is reported in aerated solution for OII concentration of 10 ppm in less than 90 min. The oxidation follows a first order kinetic with a rate constant of 4.8 9 10 -2 min -1 .

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“…On the other hand, the photocatalysis remains limited to simple materials and there have been some strategies aimed to improve the PEC performance (Mekatel et al 2012). A straightforward solution would be the utilization of heterojunctions (Belhadi et al 2011) where little systematic work with the spinels has been done because of the difficulty of adjusting the electronic bands of SCs. The hetero-junction could not only extend the spectral response of wide band gap SCs toward lower energies but also favors the charge separation by increasing the lifetime of the charge carriers.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of CdS/CuAl2O4 core–shell: application to photocatalytic eosin degradation

2014

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The advantages of the hetero-junction CdS/ CuAl 2 O 4 for the photocatalytic eosin degradation are reported. Composite semiconductors are elaborated by coprecipitation of CdS on the spinel CuAl 2 O 4 giving a coreshell structure with a uniform dispersion and intimate contact of the spinel nanoparticles inside the hexagonal CdS. The Mott-Schottky plots (C-2-V) of both materials show linear behaviors from which flat band potentials are determined. The photoactivity increases with increasing the mass of the sensitizer CdS and the best performance is achieved on CdS/CuAl 2 O 4 (85 %/15 %). The pH has a strong influence on the degradation and the photoactivity peaks at pH 7.78. The dark adsorption eosin is weak (*4 %), hence the change in the eosin concentration is attributed to the photocatalytic process. The degradation follows a zero-order kinetic with a rate constant of 5.2 9 10-8 mol L-1 mn-1 while that of the photolysis is seven times lower (0.75 9 10-8 mol L-1 mn-1).

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Photoassisted hydrogen production under visible light over NiO/ZnO hetero-system

Cited by 32 publications

References 14 publications

Hydrogen evolution under visible light over the heterojunctionp-CuO/n-ZnO prepared by impregnation method

Hydrogen evolution under visible light over the heterojunctionp-CuO/n-ZnO prepared by impregnation method

Photocatalytic degradation of orange II on the novel hetero-system WS2/TiO2 under UV light

Synthesis and characterization of CdS/CuAl2O4 core–shell: application to photocatalytic eosin degradation

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