Understanding Hydrothermal Titanate Nanoribbon Formation

Titanate nanoribbons were prepared by hydrothermal treatment of neat TiO2 P25 with 10 M NaOH at 200 degrees C. Hydrothermal aging times were varied to assist with understanding the transformation process while the impact of postsynthesis acid washing on nanoribbon formation kinetics was assessed. Nanoribbon evolution was observed to occur via the formation of intermediate amorphous titanate particles. The final nanoribbon product was found to comprise a layered titanate framework with sodium cations interspersed between the sheets. Acid washing served to exchange the Na+ with H+ to give H2Ti3O7. Moreover, acid washing accelerated nanoribbon formation, providing a well-defined (i.e., no amorphous particles) nanoribbon sample after 15 h compared to 40 h when acid washing was not used. The difference in formation rates was attributed to interlayer formation of the intermediates in the hydrogen bond array (i.e., Ti-O-H) during H2Ti3O7 being faster than intermediate formation in the sodium bond array (i.e., Ti-O-Na). Acid washing of the nanoribbon samples after extended hydrothermal synthesis times (>24 h) led to fragmenting of the structure.