3D-TNAs composite electrodes with enhanced visible-light photoelectrocatalytic performance and stability

Three-dimensional TiO2 nanotube arrays (3D-TNAs) formed by anodization over Ti meshes has been prepared. The TiO2 nanotube arrays were uniformly grown around each Ti wire in a radially outward direction, which have a large specific surface area and can absorb incident light from any direction. Composite electrodes, made of Gd, N or Gd–N and TiO2 co-doped 3D TiO2 nanotube arrays (Gd-TiO2/3D-TNAs, N–TiO2/3D-TNAs and Gd-N-TiO2/3D-TNAs), were successfully prepared by an evaporation-induced self-assembly (EISA) process and applied for the photoelectrocatalytic degradation of organic pollutants. The experimental results show that the multi-doped electrodes significantly enhanced visible light photoelectrocatalytic activity compared to TiO2/3D-TNAs without element-doped and unmodified 3D-TNAs. 99% of methylene blue (MB) was degraded by N–TiO2/3D-TNAs with a 0.7 V bias under 210 min simulated solar irradiation, which was approximately 1.5 and 1.8 times higher than that of TiO2/3D-TNAs and pristine 3D-TNAs, respectively. The N–TiO2/3D-TNAs has excellent stability, the degradation rate remained almost unchanged after used for 4 times. The enhanced photoelectrocatalytic performance of N–TiO2/3D-TNAs could be attributed to the large specific surface area, strong light absorption, low electron-hole recombination rate and wide light-response range as the result of the three-dimensional structure and N-doping heterojunction structure.