Cobalt-doped rutile/anatase TiO2 photoanode with oriented energy band offset for photoelectrochemical water splitting

The separation and transfer efficiency of photogenerated electron-hole pairs in TiO 2 nanorod is crucial for its photoelectrochemical (PEC) water-splitting performance. A band-matched TiO 2 homojunction photoanode was synthesized through a two-step hydrothermal method, where the anatase TiO 2 shell was controllably grown over Co-doping rutile TiO 2 nanorod arrays. Oxygen vacancies of the rutile TiO 2 nanorods were prominently generated with the doping of Cobalt, regarding the positive shift of the energy bands. The conduction/valence band offsets between rutile and anatase TiO 2 were increased to 0.43 and 0.25 eV, increasing the driving force for the separation of photogenerated electron-hole pairs, effectively suppressing the recombination of carriers. The cobalt doped TiO 2 homojunction photoanode with the anatase shell thickness of 42 nm demonstrated an outstanding PEC performance, with a photocurrent density of 1.45 mA cm −2 at 1.23 V vs. RHE and a hydrogen production rate of 26.17 μmol cm −2 h −1 . The results provided an effective strategy for the development of TiO 2 homojunction with high PEC water splitting performance.