A two-anode reduction technique to monitor the defect and dope the surface of TiO2 nanotube array as photo-anode for water splitting

A two-anode reduction (TAR) technique is adopted to prepare, in one step without the existence of gaseous hydrogen, black TiO 2 nanotubes co-doped with carbon and nitrogen. A sample prepared with the TAR technique for 2 min achieved the highest photocurrent response as 2.05 mA/cm 2 , which is 3 times as high as that of the pristine TiO 2 nanotubes. A synergistic effect between black hydrogenation and C, N co-doping is observed. The light absorption in the whole ultraviolet-visible (UV–vis) range is also greatly enhanced.