Rational synthesis and lithium storage properties of hierarchical nanoporous TiO2(B) assemblies with tailored crystallites and architectures

Abstract

In comparison to the common anatase, rutile and brookite phases, the bronze phase TiO2 (TiO2(B)) is rarely prepared, and obtaining unique TiO2(B) structures, especially those with complex configurations remains a great challenge. This work presents a completely new synthetic approach for fabricating hierarchical nanoporous TiO2(B) assemblies with tailored crystallites and architectures via the reaction between tetrabutyl titanate and normal fatty acids. Three different kinds of normal fatty acids, i.e., pentanoic acid, hexanoic acid, and nonanoic acid were utilized as the sole solvent. After a simple solvothermal treatment, nanoporous TiO2(B) microspheres constructed by [001]-elongated ultrathin nanorods, randomly aggregated ultrafine nanocrystals, and crystallographically oriented nanocrystals were successfully produced separately. Further investigation revealed that the morphology of the hierarchical assemblies could be modified by using foreign substrates to adjust the growth dynamics of TiO2(B) crystals. As a good illustration, by introducing graphene nanosheets into the tetrabutyl titanate-pentanoic acid system, nanosized [001]-elongated-ultrathin-nanorod-constructed nanoporous TiO2(B) assemblies were obtained, which exhibited superior performance as an anode in Li-ion batteries. This work can not only shed new light on TiO2(B) crystallization, but also provide an effective solution for the rational design of complex TiO2(B) micro-/nanoarchitectures for desired applications.