부산대학교 도서관

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 Na 2 SO 4 electrolyte exhibits p -type comportment with a flat band potential of −0.315 V RHE 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 V RHE); it is positioned cathodically with respect to the H 2 O/H 2 level (~-0.74 V RHE), producing a H 2 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 SO 3 2− 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 H 2 photo production. • The conduction band of ZnO (−0.92 V RHE), yields H 2 photo-evolution (−0.74 V RHE). • The photoactivity peaks at pH ~ 7 for a catalyst dose of 0.25 mg/mL in presence of SO 3 2−. [ABSTRACT FROM AUTHOR]