Transition-Metal-Ion (Fe, Co, Cr, Mn, Etc.) Doping of TiO₂ Nanotubes: A General Approach

Transition-metal (TM)-ion-doped TiO₂ materials are of great importance for photocatalysis- and photoelectrochemical (PEC)-related applications. We introduced a facile, low-cost, and scalable doping method of TM ions (Cr, Co, Cu, Fe, Mn, etc.) into TiO₂ nanotubes (NTs), while maintaining their high-ordered tubular structures (with ∼120 nm outside diameter). Both crystallization and doping processes were simultaneously accomplished in aqueous solution at a temperature as low as ∼90 °C, and the fastest doping process could be accomplished in 30 min for Fe doping. Besides, the surface areas of the doped TiO₂ NTs were increased to 129.0 m²/g, and their absorption ranges could be expanded from 380 to >500 nm. This study shed light on a facile method for doping TM ions that is extendable to other semiconductors in the field of PEC water splitting and could improve their efficiencies as well.