Synthesis of spherical mesoporous titania modified iron-niobate nanoclusters for photocatalytic reduction of 4-nitrophenol

Spherical mesoporous titania modified iron-niobate nanoclusters FNT1 [FexNbxTi1−2xO2−x/2 (x = 0.01)], with relatively small particle size 10 ± 2 nm and SBET 145 m2 g−1 were prepared using a sol–gel method, from the reaction of titanium and niobium tartrate with triethanol amine and ferric nitrate solution. HRTEM of FNT1 shows coexistence of porous mesostructure and high symmetric order of crystallinity in the nanoparticles. The mesopore size is in the range of 4–5 nm and the lattice fringes of 0.37 nm is observed in the mesopore walls which correspond to the d-spacing between adjacent (101) crystallographic planes of FNT1 phase. This is supported by XRD studies. In the presence of UV light, FNT1 (0.1 g/50 mL) reduces the 4-nitrophenol (4-NP) (0.0139 g L−1) to 4-aminophenol by using NaBH4 (0.054 g L−1) in contrast to pure TiO2 and other composites of FexNbxTi1−2xO2−x/2 photocatalysts. The 4-NP is reduced to 4-aminophenol within 10 min in the presence of FNT1 and UV light, but in the absence of the catalysts, it takes approximately 82 min. The catalytic activity of FNT1 is enhanced significantly in the presence of UV light compared to the absence of UV light. We observed that the catalytic activity of the prepared catalyst also depends on crystal size, particle morphology and particle porosity, and dopant concentrations.