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.