Visible Light Hydrogen Evolution over α-MoO3 and α-MoO3/ZnO Hetero-Junction

MoO3 and 5% MoO3/ZnO were prepared by impregnation method using (NH4)6Mo7O24, 4H2O as precursor and ZnO as support. The prepared samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), infra red (FTIR) and UV-Vis diffuse reflectance (DRS) spectroscopies and photo-electrochemistry. The XRD pattern showed that the MoO3 powder treated at 700°C is a single-phase crystallizing in an orthorhombic structure with a direct optical transition (2.70 eV). The hetero-junction 5% MoO3/ZnO was photo-electrochemically characterized to assess its feasibility for H2 production under visible light. The capacitance potential (C-2 f(E)) characteristic of MoO3 plotted in Na2SO4, (0.1 M) electrolyte indicates n-type conduction with a flat band potential of -0.54 VSCE. The photocatalytic activity was performed for the photoreduction of water to hydrogen under visible light illumination. The best performance occurs at pH ~ 7 with an evolved volume of 5.9 mL.