Solution-Based Comproportionation Reaction for Facile Synthesis of Black TiO2 Nanotubes and Nanoparticles

A convenient and efficient strategy is disclosed for blackening anodic TiO 2 nanotubes and commercial P25 powders through an easy solution-soaking treatment at mild conditions (e.g., 60 °C) in polyol (e.g., glycerol, ethylene glycol) solutions. The F – ions, acidic polyol solvents, and contact between the TiO 2 and Ti components are discovered to be the prerequisites for the water-promoted comproportionation between TiO 2 and Ti, which generate Ti(III) species that effectively blacken different TiO 2 nanomaterials, including the anodic nanotube arrays and P25 nanoparticles. The black TiO 2 thus obtained from this convenient soaking method displays improved photoelectrochemical performance.