(NH4)3TiOF5 mesocrystals grown by electric-field-assisted oriented-particle aggregation and their conversion to a TiO2 superstructure

This work reports an electrochemical synthesis of (NH4)(3)TiOF5 mesocrystals consisting of nanocrystalline building units, via oriented particle attachment driven by an external electric field. The obtained (NH4)(3)TiOF5 mesocrystals are octahedral in shape and can be converted to porous anatase TiO2, retaining their octahedral morphology after thermal annealing treatment. A distinctive evolution process for the (NH4)(3)TiOF5 mesocrystals with octahedral morphology is revealed, which includes the nucleation and growth of primary small octahedral particles, oriented aggregation of six primary octahedral particles into one large secondary particle, formation of mesocrystalline octahedrons by crystallographic fusion, dissolution of the octahedrons into small nanoparticles, followed by oriented aggregation of the dissolved nanoparticles to form micrometer-sized octahedrons. The alignment and subsequent oriented attachment of nanoparticles driven by an external electric field enable the rapid growth of (NH4)(3)TiOF5 mesocrystals within 40 s, compared with the tens of hours usually required for the growth of NH4TiOF3 mesocrystals using a hydrothermal method.

Automated summary

This work reports an electrochemical synthesis method for (NH4)3TiOF5 mesocrystals consisting of nanocrystalline building units, and reveals the evolution process of mesocrystals with octahedral morphology.