Control of Metal Oxides’Electronic Conductivity Through Visual Intercalation Chemical Reactions

Abstract Cation intercalation is an effective method to optimize the electronic structures of metal oxides, but manipulating the intercalation structure and conductivity is difficult. Here, we report a visual topochemical synthesis strategy to control the intercalation pathways, structures, and conductivity, and realize rapid synthesis of flexible conductive metal oxide films in 1 min at room-temperature. This study uses a flexible topological TiO2 nanofiber film as the prototype and designs three different charge-driven models to intercalate the preset Li+-ions into the TiO2 lattice slowly (µm/s), rapidly (mm/s) or ultrafast (cm/s). The Li+-intercalation causes real-time color changes of the TiO2 films from white to blue and then black, corresponding to the new structures of blue LixTiO2 and black TiO2-δ derived in TiO2, and the enhanced conductivity from 0 to 1 and 40 S/m. This work realizes the rapid synthesis of flexible TiO2 nanofiber films with tunable conductivity on large-scale and has been extended to synthesize other conductive metal oxide films for appealing applications in fast-charge electrodes, electrochromic pattern designs, catalysis and so on.