2. Experimental
2.1. Photoelectrode fabrication
The semiconductor oxide film containing copper (II), zinc (II) and tin (IV) cations, was electrochemically deposited on a 1.51.5cm fluorine-doped tin oxide (FTO) glass (SOLARONIX, the electrical resistance: 10 Ω/sq). Therefore, an aqueous solution containing 0.01M Cu2þ (CuSO45H2O; Fluka), 0.005M Zn2þ (ZnSO47H2O; Fluka), 0.01M Sn4þ (SnCl4; Alfa Aesar) and 2.35g/lit trisodium citrate (Na3C6H5O72H2O; Fluka) was first prepared. By applying a negative potential, chosen 1.05 VSCE [25];in this potential,all cations mentioned above can be simultaneously electrodeposited, a composite film was coated on the FTO substrate for 90min. The electrode (filmþsubstrate) was thereafter annealed in air atmosphere (823K, 4h). The deposition of Ag on the electrode surface was performed photochemically [26], by immersing the fabricated electrode into a silver nitrate (0.5mM) alcoholic solution (1:4 volumetric ratio of water to ethanol) and illumination with xenon light for one hour.