Bi_3.25Nd_0.75Ti₃O₁₂ Nanostructures: Controllable Synthesis and Visible-Light Photocatalytic Activities

Neodymium-doped bismuth titanate (Bi_3.25Nd_0.75Ti₃O₁₂, BNdT) nanostructures with different morphologies were synthesized hydrothermally without using surfactant or template. Transmission electron microscopy (TEM) results showed that different morphologies could be fabricated simply by manipulating the concentration of OH^- ions during hydrothermal synthesis. Hydroxide ions played an important role in controlling the formation of seeds and the growth rate of BNdT particles. On the basis of structural analysis of samples obtained under different conditions, a possible mechanism for the formation of these distinctive morphologies was proposed. A UV-visible diffuse reflectance spectrum (UV-Vis DRS) of an as-prepared BNdT sample revealed that its band gap energy (E_g) was about 1.984 eV. BNdT photocatalysts exhibited higher photocatalytic activities for the degradation of methyl orange (MO) under visible light irradiation than those for traditional commercial P25 TiO₂ and N-doped TiO₂ (N-TiO₂). BNdT nanowires prepared using a hydroxide concentration of 10 mol·L^-1 showed the highest photocatalytic activity among the samples. Over this catalyst, 93.0% degradation of MO (0.01 mmol·L^-1) was obtained after irradiation with visible light for 360 min. In addition, there was no significant decrease in photocatalytic activity after the catalyst was used 4 times, indicating that BNdT is a stable photocatalyst for degradation of MO under visible light irradiation.