Characteristics and properties of a novel in situ method of synthesizing mesoporous TiO2 nanopowders by a simple coprecipitation process without adding surfactant

In situ synthesis of mesoporous TiO2 nanopowders using titanium tetrachloride (TiCl4) and NH4OH as initial materials has been successfully fabricated by a coprecipitation process without the addition of surfactant. Characteristics and properties of the mesoporous TiO2 nanopowders were investigated using differential scanning calorimetry/thermogravimetry (DSC/TG), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and Barrent-Joyner-Halenda (BJH) analyses, transmission electron microscopy (TEM), selected area electron diffraction (SAED) and high resolution TEM (HRTEM). The results of TG and XRD showed that the NH4Cl decomposed between 513 and 673 K. XRD results showed that the anatase TiO2 only contained a single phase when the calcination temperature of the precursor powder was less than 673 K. Whereas phases of anatase and rutile TiO2 coexist after calcining at 773 K for 2 h. The crystalline size of the anatase and rutile TiO2 was 14.3 and 26.6 nm, respectively, when the precursor powder was calcined at 773 K for 2 h. The BET and BJH results showed a significant increase in surface area and pore volumes when the NH4Cl was completely decomposed. The maximum values of BET specific surface area and volume were 172.8 m2/g and 0.392 cm3/g, respectively. The average pore sizes when calcination was at 473 and 773 K for 2 h were 3.8 and 14.0 nm, respectively.