Effect of Ni_xCo_(3-x)O_4 Modification for CdSe/TiO_2 Nanotube Arrays on Activity of Photoelectrochemical Oxidation of Water

CdSe/TiO2 nanotube array (TiO(2)NTA) film was modified by NixCo3-x,O-4 through the method of ammonia-evaporation induction growth. The films were characterized by X-ray diffraction, field emission scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy and UV-Vis diffuse reflectance spectroscopy. To characterize the photoanodes activity of photoelectrochemical oxidation of water, the chopped linear sweep voltammetry was performed in a three-electrode system under simulated solar irradiation. The results show that CdSe/TiO(2)NTA is covered by a thin layer of NixCo3-x,O-4 with the spinel structure in which Ni and Co are both in divalent and trivalent states. The modification of NixCo3-x,O-4 on the CdSe/TiO(2)NTA can lower the overpotential of water oxidation by about 430 mV compared with the CdSe/TiO(2)NTA. The introduction of Ni into the structure of Co3O4 leads to the surface enhancement of trivalent cations (Ni3+ and Co3+) and consequently facilitates the oxidation of water.