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Photocatalytic hydrogen production on the hetero-junction CuO/ZnO

The co-precipitation is successfully used for the synthesis of the hetero-junction CuO/ZnO. Thermal analysis, ATR spectroscopy and diffuse reflectance were used to assess the photoactivity of the hetero-system for the hydrogen formation upon visible light. As expected, the X-ray diffraction shows mi...

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Bibliographic Details
Published in:International journal of hydrogen energy 2021-10, Vol.46 (75), p.37556-37563
Main Authors: Haddad, Meriem, Belhadi, Akila, Boudjellal, Loubna, Trari, Mohamed
Format: Article
Language:English
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Summary:The co-precipitation is successfully used for the synthesis of the hetero-junction CuO/ZnO. Thermal analysis, ATR spectroscopy and diffuse reflectance were used to assess the photoactivity of the hetero-system for the hydrogen formation upon visible light. As expected, the X-ray diffraction shows mixed phases of CuO (tenorite) and ZnO (Wurtzite). The specific surface area is around ~7 m2 g−1 with a crystallite size lying between 20 and 49 nm. The diffuse reflectance indicates an indirect transition at 3.13 eV for ZnO and a direct transition at 1.60 eV for the sensitizer CuO. The capacitance-potential (C−2 - E) characteristic of CuO plotted in Na2SO4 electrolyte exhibits p-type comportment with a flat band potential of −0.315 VRHE and a holes concentration of 8.7 × 1018cm−3. The Electrochemical Impedance Spectroscopy exhibits a semicircle characteristic of the bulk material with an impedance of 1725 Ω cm2 which decreases down to 453 Ω cm2 under irradiation, supporting the semiconducting character of CuO. ZnO mediates the electrons transport thanks to its conduction band, formed from Zn2+: 4s orbital (−0.92 VRHE); it is positioned cathodically with respect to the H2O/H2 level (~-0.74 VRHE), producing a H2 evolution under visible light illumination. The performance peaks at pH ~7 on 5% CuO/ZnO for a catalyst dose of 0.25 mg of catalyst/mL of solution in the presence of SO32− as holes scavenger. A liberation rate of 340 μmol h−1 (g of catalyst)−1 is obtained with a quantum efficiency of 0.38% under a photons flux of 2.09 × 1019 s−1. •Nano particles of 5% CuO/ZnO elaborated by co-precipitation was used for the H2 photo production.•The conduction band of ZnO (−0.92 VRHE), yields H2 photo-evolution (−0.74 VRHE).•The photoactivity peaks at pH ~ 7 for a catalyst dose of 0.25 mg/mL in presence of SO32−.
ISSN:0360-3199
1879-3487
DOI:10.1016/j.ijhydene.2020.11.053