Effect of experimental parameters on the formation of hydrated sodium titanate nanocrystals

Obtaining high-performance hydrated sodium titanates is crucial for widespread applications in photocatalysis, sodium batteries, hydrogen production, storage and solar cells. Herein, hydrated sodium titanate nanocrystals were prepared using industrially produced H₂TiO₃ nanopowders as the main raw material by a hydrothermal method. The effects of NaOH concentration, reaction temperature and reaction time on the phase and morphology of the final products were studied. Results showed that when the amount of H₂TiO₃ raw material, reaction temperature and reaction time were kept constant, with the gradual increase of NaOH concentration, the products would change from H₂TiO₃ → Na₂Ti₂O₄(OH)₂/Ti₃O₅ → Na₂Ti₂O₄(OH)₂ → NaTi₃O₆(OH)·2H₂O. The morphology gradually changes from irregular nanoparticles to nanoplates, nanowires and nanoribbons. The concentration of NaOH has the greatest effect on the phase and morphology. NaOH acts as a reactant during the reaction and also as a morphological controllable agent. However, the reaction temperature and time have little effect on the phase of the final product at a given concentration of NaOH (10 M), but have a greater effect on the morphology of the as-prepared product. The Na₂Ti₂O₄(OH)₂ nanowire is obtained when the temperature is lower and the reaction time is shorter. In contrast, the NaTi₃O₆(OH)·2H₂O nanoribbon is obtained at an elevated reaction temperature or with a longer reaction time. Based on the above experimental results, a useful formation mechanism of the hydrated sodium titanate nanocrystals with controllable phase and morphology was proposed, which can be expected to facilitate materials researchers in the preparation and widespread application of hydrated sodium titanate nanomaterials.