Sol–gel silver hexatitanates as photocatalysts for the 4-chlorophenol decomposition

Sodium hexatitanate (Na2Ti6O13) and silver-supported sodium hexatitanates were prepared by the sol–gel and solid state reaction methods. Fibril structures and octagonal microbar hexatitanates were obtained. Silver nanoparticles were incorporated into the sodium hexatitanate supports by the deposition–precipitation technique. HRTEM (high resolution transmission electron microscopy) and high angle annular dark field (HAADF) digital images showed silver particles with nanometric sizes (5–7 nm). Eg band gap values around 3.3–3.2 eV were obtained in the solids. UV–vis–DRS spectra showed in the visible region, the silver plasmon surface resonance which intensity was taken as an indirect way to determine the enhanced photoactivity of the semiconductors. In the 4-chlorophenol photodecomposition, it was found that the sol–gel silver fibril solid was more active (t1/2 = 57 min) than the silver solid state microbars (t1/2 = 92 min). It is proposed that the highest photoactivity showed by the sol–gel fibril preparation is an effect due to the formation of highly dispersed silver nanoparticles on the sol–gel hexatitanate support.