A novel approach to mesoporous anatase TiO 2: Oxidation of TiC by nitric acid

Abstract

TiO 2 has been prepared by a novel, mild one-step reaction between TiC and aqueous HNO 3 at 70 °C. This material possesses an anatase crystal form and a narrow pore-size distribution of mesoporous channels. The BET surface area, average pore diameter, and total pore volume are 332.7 m 2/g, 3.28 nm, and 0.23 cm 3/g, respectively. Our method is a template-free synthesis process, distinct from sol–gel methods for mesoporous TiO 2 fabrication using structure-directing surfactants or polymers. TiO 2 is not generated from TiC reacting with other acids and oxidants, such as HCl, H 2SO 4, H 3PO 4, KMnO 4, K 2Cr 2O 7, Na 2S 2O 7, H 2O 2, and Na 2CrO 4, at a similar reaction condition. Since the average particle size of the mesoporous TiO 2 produced is much larger than that of the TiC starting material, the mechanism for the formation of the mesoporous TiO 2 is not via mesopore-etching of TiC particles and transformation of TiC pore walls into TiO 2 by HNO 3. It is likely that TiC is first transformed into Ti m X n species, followed by hydrolysis to form mesoporous TiO 2.