Hydrothermal Reaction Mechanism and Pathway for the Formation of K 2 Ti 6 O 13 Nanowires

Calculations and detailed first principle and thermodynamic analyses have been performed to understand the formation mechanism of K 2 Ti 6 O 13 nanowires (NWs) by a hydrothermal reaction between bulk Na 2 Ti 3 O 7 crystals and a KOH solution. It is found that direct ion exchange between K + and Na + plus H + interactions with [TiO 6 ] octahedra in Na 2 Ti 3 O 7 promote the formation of an intermediate H 2 K 2 Ti 6 O 14 phase. The large lattice mismatch between this intermediate phase and the bulk Na 2 Ti 3 O 7 structure, and the large energy reduction associated with the formation of this intermediate phase, drive the splitting of the bulk crystal into H 2 K 2 Ti 6 O 14 NWs. However, these NWs are not stable because of large [TiO 6 ] octahedra distortion and are subject to a dehydration process, which results in uniform K 2 Ti 6 O 13 NWs with narrowly distributed diameters of around 10 nm.