Nb‐Doped TiO₂ Photocatalysts Used to Reduction of CO₂ to Methanol

Abstract

In pursuit of higher photoactivity, Nb‐doped TiO 2 powders were evaluated in the reduction of CO 2 . The replacement of Ti by Nb in the crystalline structure of TiO 2 promoted methanol formation. Nb‐doped TiO 2 powders were successfully synthesized in Nb concentrations of 0.0, 0.5, 1.0, and 2.5% (w/w = weight/weight) using the Pechini method. The materials were calcined at 500°C for two hours to promote the formation of the anatase crystalline phase. After characterization, the powders were modified through an Nb 0 magnetron sputtering deposition using a metallic target in vacuum conditions of 2 × 10 −3 torr, with a deposition time of 10 minutes, and calcination again at 500°C for two hours. The resulting powders showed a surface area up to 30 m 2 /g. The Pechini method promoted the substitution of Ti 4+ for Nb 4+ as observed using XRD and XPS techniques at the crystalline structure and at the surface of the powder. Furthermore, the presence of Nb 0 was also observed at the powder’s surface. The presence of Nb in the crystalline structure increased the photoactivity of powders when compared to nonmodified TiO 2 powders, while the Nb 0 deposition at the powder’s surface decreased the photoactivity for all the investigated compositions.