Preparation and photo-electrochemical performance of TiO2 nanotube arrays for water splitting modified with CuO via a simple method

A CuO/TiO2/Ti heterojunction photo-electrode was fabricated based on TiO2 nanotube arrays, prepared with anodic oxidation. A facile and economical wet impregnation followed by annealing was employed to fabricate CuO-modified TiO2 nanotube arrays. The structural and optical properties were characterized with SEM, EDX, XRD and UV-Vis spectrometry. The photo-electrochemical properties were measured with CHI 660E under a 150WXe lamp and in the dark. Moderate amounts of the CuO-modified TiO2 nanotube arrays (TiO2-CuO (I)) exhibited photocurrents of 4.633 x 10(-5)A/cm(2) and 2.29 x 10(-5)A/cm(2) at -0.35 V (vs. SCE) in a 0.2 M Na2SO4 electrolyte under the light and in the dark, respectively. The current density of TiO2-CuO (I) was higher than that of the pure-TiO(2)electrode in the light, but the current density of TiO2-CuO (I) was lower than that of pure TiO2 in the dark. Therefore, the CuO on the TiO2 surface increased the electrical resistance. Significantly, the CuO films of TiO2-CuO (II) were too thick to decrease the photo-electrochemical activity, which was confirmed with electrochemical impedance spectroscopy.