Stable synthesis mechanism and photocatalytic properties of TiO nanocrystals with different morphologies derived from potassium titanate nanowires.

This study explored key factors influencing TiO morphology using potassium titanate nanowires (KTNWs) as precursors. The pH of the hydrothermal solution was identified as critical in controlling TiO morphology. Different washing methods for precursors synthesized under alkaline conditions lead to varying pH environments in the subsequent hydrothermal solutions, thereby influencing the growth direction of TiO nuclei. Even a very slight pH change could cause a huge difference in the morphology of TiO, by adjusting precursor washing methods, rod-like, cuboidal, and octahedral bipyramidal TiO nanocrystals were synthesized, the octahedral bipyramidal TiO exhibiting the smallest particle size. Acid treatment could stabilize the octahedral bipyramidal morphology of the TiO nanocrystal, and reduced particle size by nearly 86% than that of rod-like TiO-R nanocrystal. Acid treated sample TiO-R-H7 achieved the best photocatalytic activity, which was nearly 3 times than that of original TiO. Adjusting (NH)CO morphology-controlling agent concentrations further regulated {001} facet exposure ratio to improve the photocatalytic activity, the TiO-R-0.14 synthesized at 0.14 mmol per L (NH)CO showing about 2.6 times than that of original TiO. However, excessive (NH)CO concentrations would reduce the photocatalytic activity due to increased particle size and fewer oxygen vacancies. This study provides insights into the growth mechanisms of TiO morphologies and highlights acid treatment as a strategy to reduce particle size and enhance photocatalytic activity, offering guidance for designing high-performance TiO based photocatalyst.