中文摘要：

作为光电化学系统的重要组成部分之一，光电极应该具有较好的光电流响应，以及在水溶液中稳定的特性。分别以醋酸镍、钛酸四丁酯作为NiO、TiO2溶胶的前驱体，利用溶胶-凝胶法制备了单质P型NiO及p-n结型复合光阴极NiO—TiO2。复合光阴极的SEM截面形貌显示NiO层和TiO2层的厚度分别为200，130nm。光电化学表征结果表明，NiO-TiO2复合光阴极的阴极光电流优于单质NiO电极的阴极光电流，并且其平带电势与单质NiO电极相比发生正向移动，这些现象都是由p-n结的内建电场引起的。

英文摘要：

Since the photo electrochemical cell was used in the conversion of the solar energy to the electrical power or to hydrogen, more and more attention has been paid in this field. The photocathode plays an important roll in the electrochemical chain of PEC. In this paper, the p-n junction was used to improve efficiency of the photocathode because the inner electric field of the p-n junction can make the photo-generated carriers separate more easily. The NiO electrode and the NiO-TiO2 hybrid electrode were fabricated on the SnO2： F （FTO） transparent conducting glass via sol-gel method. The solution was prepared by using the nickel acetate tetra hydrate and the tetra-n-butyl tianate as precursors. The films were obtained by spin-coating method and then annealed at 450 ℃ in air for three hours, The crystal structures of the films were characterized by X-ray diffraction （XRD）. Scanning electron microscopy （SEM） was also used to investigate the microstructures of the films. The XRD results showed that all the strongest peaks were indexed to the anatase TiO2 and the bunsenite NiO, respectively. From SEM, the surface of the film was quite compact, the grains were nanometer-sized and the thicknesses of NiO and TiO2 layer were 200 nm and 130 nm, respectively. Moreover, the photoelectrochemical properties of the NiO and the NiO-TiO2 hybrid electrode were also investigated under 500 W Xe arc lamp illu- mination. It was found that the cathode photocurrent of the NiO-TiO2 hybrid electrode was larger than that of the NiO electrode and that the flat-band potential of the hybrid electrode was also more positive than that of NiO electrode. Therefore, the results indicated that the photo-generated carriers could be separated and trans- ferred more easily for the build-in electric field of the p-n junction. Besides, an energy band diagram of the p-n junction was proposed to explain the results in this paper.