Co/Mn co-doped TiO2 nanotube arrays for enhanced photoelectrochemical properties: experimental and DFT investigations

In this study, we used first principle calculations to investigate the electronic properties of TiO2 modified with eight different elements. Co/Mn co-doped TiO2 nanotube arrays, which had the smallest band gap, were subsequently prepared using electrochemical anodization followed by atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM) measurements. The results showed that the TiO2 nanotube arrays were highly ordered and well aligned. Finally, the photoconversion efficiency was measured using photoelectrochemical experiments and, under the same conditions, the photoconversion efficiency under visible light increased approximately three times from 9.35% for the undoped TiO2 nanotubes to 21.25% for the Co/Mn co-doped TiO2 nanotubes. These results indicate that Co/Mn co-doped TiO2 nanotube arrays can improve the efficiency of visible-light utilization and could be a promising material in such fields as photocatalysis and solar cells.