Preparation, characterization and photocatalytic property of nanosized K-Ta mixed oxides via a sol-gel method

摘要

Pyrochlore-type K_2Ta_2O_6 compound cannot be obtained by a conventional solid-state reaction. Here, we report the synthesis of K_2Ta_2O_6 and tetragonal tungsten bronze (TTB)-type K_6Ta_(10.8)O_(30) nanopowders using a facile and low-cost sol-gel method at low temperature. The as-prepared samples were characterized by XRD, TC-DSC, FESEM, UV-vis diffuse reflectance spectrum and XPS. The compound K_2Ta_2O_6 was formed at 700 C and reached complete crystallization at 750 C, and decomposed into pure K_6Ta_(10.8)O_(30) with the volatilization of K_2O at 900 ℃. The transformation of K_2Ta_2O_6 to K_6Ta_(10.8)O_(30) is reported for the first time. The band gap of the pure K_2Ta_2O_6 and K_6Ta_(10.8)O_(30) samples was found to be about 4.16 and 3.63 eV, respectively. The as-prepared K_2Ta_2O_6 sample exhibited an efficient photocatalytic activity for the decomposition of azo dye acid red G (ARG) and 4-nitrophenol (4-NP, a typical persistent organic pollutant) solution under UV irradiation. According to the experimental results, the mechanism of the photocatalytic reaction over K_2Ta_2O_6 was discussed.