Effect of heating temperature on photocatalytic reduction of CO2 by N–TiO2 nanotube catalyst

Nitrogen-doped TiO2 nanotubes (N-TNTs) have been synthesized via a hydrothermal method using hexamethylene tetramine (HMT) and TiCl3 as precursors. Photocatalytic activity was characterized by XRD, SEM, TEM, BET and UV–vis DRS. N was doped into the TiO2 lattice, it extended the absorption region of TiO2 to visible light. Post-heating TNTs at 300–500 °C showed a maximum red-shifted at 500 °C with a band gap energy of 3.09 eV. The visible light activity of N-TNTs was evaluated using CO2 reduction. The total organic carbon (TOC) yield of N-TNT500 was 14530.0 μmol/g-catal. following 12 h of illumination. The yield is much higher than those of N–TiO2 and TNTs.

► Hexamethylene tetramine (HMT) and TiCl3 as nitrogen nanotubes (N-TNTs) precursors. ► N-TNTs and TNTs for visible light reduction of CO2. ► N-TNTs and TNTs at high temperature enable maintain stability. ► Nitrogen was doped into the TiO2 lattice, it extended the absorption region of TiO2 to visible light.