In situ fabrication of CdSe/TiO2 nanotube arrays with enhanced photoelectrical and catalytic activity

TiO2 nanotube arrays (TiO2 NTs) films were successfully derived from Ti substrate through a twice electrochemical anodization method. CdSe nanoparticles were then uniformly deposited on the TiO2 NTs (CdSe/TiO2 NTs) via in situ deposition method. CdSe/TiO2 NTs possess a better visible light harvesting ability compared to pure TiO2 NTs. Importantly, the generation, accumulation and transportation of free electrons of the CdSe/TiO2 hetero-junctions were systematically investigated by photoelectrochemical experiments. The open-circuit potential of 7-CdSe/TiO2 NTs (-0.31 V) is higher than that of TiO2 NTs (-0.18 V), suggesting increased electron generation and accumulation. Meanwhile, the flat band potential of 7-CdSe/TiO2 NTs (1.88 V) shows a positive shift compared with that of TiO2 NTs (-0.05 V), implying a significant chemical potential gradient from the electrolyte to the surface of CdSe/TiO2 NTs. Additionally, the 7-CdSe/TiO2 NTs exhibit the highest photoelectrocatalytic activity for methylene blue degradation. Those enhanced photoactivities are assigned to the synergistic effect of the one-dimensional nanotubular structure and the efficient separation of charge carriers.