Facile synthesis of thermally stable anatase titania with a high-surface area and tailored pore sizes

Both affordability and stability are important for commercial-scale production and industrial applications of TiO2. In addition, the ability to tailor nanostructure and physicochemical properties can provide advantages for future applications. Herein a facile sol‒gel process was investigated by using titanyl sulfate as an inexpensive feedstock reacting with water in the media of acetic acid and isopropanol. An anatase phase was readily produced at 65 °C, followed by drying at 80 °C. The anatase was stable up to 800 °C due to the residual sulfate and nitrogen, where sulfate and ammonium slowly decomposed when heating beyond 400 °C. The monolithic TiO2 xerogels were composed of agglomerated TiO2 spherical particles with diameters of ca. 50 or 100 nm. The TiO2 spherical particles were built by anatase crystallites with a diameter of ca. 5 nm. As a result, the TiO2 exhibited both bimodal mesopores and macropores: Large mesopores (10‒30 nm) were present due to the void spaces between the TiO2 spherical particles, while the smaller mesopores (ca. 3 nm) were due to the void spaces between the anatase crystallites within each TiO2 particle. There were also larger macropores (a few micrometers), which were caused by gas bubbles generated during the sol‒gel reactions. From a mass transfer viewpoint, these large pores within TiO2 xerogels could have advantages in their potential applications for catalysis and/or filtration processes. Graphical Abstract