Growth, structure and photocatalytic properties of hierarchical Cu–Ti–O nanotube arrays by anodization

Recently p-type Cu–Ti–O nanotubes have been explored in water-splitting photoelectrochemical pn-junction diodes to significantly improve the photoconversion efficiency. We reported on the growth and characterization of Cu–Ti–O nanotube arrays by anodizing directly Cu–Ti (30:70 wt%) alloy substrate. As-anodized hierarchical Cu–Ti–O nanotube arrays consist of two distinct Ti-rich and Cu-rich nanotube regions. It was found that mechanical stresses induced by copper doping resulted in the difference in the microstructure evolution of Cu-rich and Ti-rich regions. The oxygen vacancies induced by the high concentration Cu dopant into the Cu–Ti–O nanotube play a crucial role in determining the phase stabilization of anatase phase. The absorption edge of TiO2 nanotube arrays was extended into the visible region by Cu doping. In degrading Methyl orange (MO), 21.2% MO was removed using Cu–Ti–O nanotube arrays after 240 min UV illumination. This result indicates the photocatalytic activity of Cu–Ti–O nanotube arrays to MO is reasonably high.