Oxygen vacancy-enriched CoPi/TiO₂ nanotubes/WO₃ electrode for enhanced photoelectrochemical water oxidation

TiO₂ has been widely used in photocatalytic water splitting, but its wide band gap and easy recombination carrier limit its further application. In this work, highly ordered TiO₂ nanotube arrays (TiO₂ NBs) were prepared by anodic oxidation, and more oxygen vacancies were provided by local amorphous. The increase of oxygen vacancy improves the carrier separation efficiency, and the array structure achieves faster electron transport. In addition, WO₃ semiconductor was coupled with TiO₂ to construct heterojunction, expand the range of light absorption, and enhance the electron–hole pair separation efficiency. In addition, by introducing co-catalyst CoPi, the active site of the reaction was increased, and the catalytic reaction efficiency was improved kinetically. The results show that the photocurrent of CoPi/WO₃/TiO₂ NBs is 10.2 μA/cm², which is 1.68 times that of TiO₂ NBs.