Boosting photoelectrochemical chlorine and hydrogen production with oxygen vacancy rich TiO2 photoanodes.

Photoelectrochemical chlorine (Cl 2) evolution as the anodic reaction of solar hydrogen production is helpful for increasing the additional value of hydrogen and reducing production cost. In this work, chemically stable TiO 2 nanotubes are used as the photoanodes for photoelectrochemical chlorine and hydrogen production. Oxygen vacancies (V O) are introduced by post-annealing in H 2 /N 2 atmosphere. By controlling the post-annealing temperature, concentration of oxygen vacancies is tuned efficiently. Systematic photoelectrochemical measurements reveal that the oxygen vacancies significantly enhance the PEC performance for Cl 2 production with respect to the pristine TiO 2. The sample post-annealed at 450 °C in H 2 /N 2 achieves the highest Cl 2 production rate of 37.12 μmol h−1 cm−2 with a Faradaic efficiency of 73.2% that resulted in fast degradation of methyl orange at a speed of 5.73 mg h−1 cm−2. Furthermore, photocurrent of the two-electrode cell constructed with the V O -rich TiO 2 is strongly increased by 250%, demonstrating that introducing oxygen vacancies is a promising way for promoting the photoelectrochemical performance for Cl 2 and H 2 production. By careful measuring the Faradaic efficiency of various photoanodes, it is revealed that the strongly boosted up Cl 2 production is owing to enhancing utilization of photogenerated holes via the oxygen vacancies. [Display omitted] • Oxygen vacancies are efficiently introduced to the TiO 2 photoanodes. • Photocurrent is strongly increased by the oxygen vacancies. • Chlorine production with an Faradaic Efficiency of 73.9% was achieved. • The boosted performance is owing to the enhanced utilization of photo-generated holes and electrons. [ABSTRACT FROM AUTHOR]