Photocatalytic degradation of Rhodamine B by microwave-assisted hydrothermal synthesized N-doped titanate nanotubes

Microwave-induced nitrogen-doped titanate nanotubes (NTNTs) were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Zeta potential analysis, specific surface area (SBET), and UV-Visible spectroscopy. TEM results indicate that NTNTs retain a tubular structure with a crystalline multiwall and have a length of several hundred nanometers after nitrogen doping. XRD findings demonstrate that the crystalline structure of NTNTs was dominated by anatase, which is favored for photocatalytic application. The Ti-O-N linkage observed in the XPS N 1s spectrum is mainly responsible for narrowing the band gap and eventually enhancing the visible light photoactivity. FT-IR results demonstrated the existence of H₃O⁺, which could be excited by photo-generated holes to form hydroxyl radicals and degrade environmental pollutants. After sintering at 350°C, the UV-Vis absorbance edges of NTNTs significantly shift to the visible-light region, which indicates N atom doping into the nanotubes. Photocatalytic degradation of Rhodamine B (RhB) via NTNTs show good efficiency, with pseudo first-order kinetic model rate constants of 3.7 × 10⁻³, 2.4 × 10⁻³ and 8.0 × 10⁻⁴ sec⁻¹ at pH3, 7, and 11, respectively.