Electrodeposition of Sb₂S₃ light absorbers on TiO₂ nanorod array as photocatalyst for water oxidation

Artificial photosynthesis provides a direct approach toward addressing energy and environmental issues by producing chemical fuels such as hydrogen for fuel cells. A photoanode composed of the composite of titanium dioxide (TiO₂) nanorod and antimony sulfide (Sb₂S₃) nanoparticles was proposed in this work. The TiO₂ nanorod array is made on a fluorine-doped tin oxide glass by using the hydrothermal reaction, and the Sb₂S₃ nanoparticles were deposited on the TiO₂ nanorod array by using the electrodeposition method with different depositing currents. The electrodeposition method is more time-saving as compared with the commonly used chemical bath reaction method. The Sb₂S₃ was selected as the coating material due to its broader light absorption range and suitable band-edge positions relating to those of TiO₂ for forming a type II heterojunction, aiming to improve the poor visible light absorption and low quantum efficiency of TiO₂. A higher photocurrent density of 0.33 mA cm⁻² (measured at 1.23 V vs. reversible hydrogen electrode) is obtained for the TiO₂/Sb₂S₃ photoanode in a 0.5 M Na₂SO₄ aqueous solution under the air mass 1.5 global illumination, comparing to that of 0.017 mA cm⁻² for the TiO₂ electrode measured under the same conditions. This successful combination of two n-type semiconductors as the photocatalyst for achieving efficient water oxidation provides a conceptual blueprint for designing the composite with complementary optical and electrical properties.