Tio₂/Co₃O₄ Composite as Photoanode of Photoelectrochemical Water Splitting

Titanium dioxide is one of the most investigated materials for photoelectrochemical (PEC) water splitting. However, TiO₂ has a wide band gap of approximately 3.2 eV, which limits its absorption energy to UV only, and the photoexcitation products (i.e., electron and hole) easily recombine. Developing a composite with other semiconductor materials is one of the efforts for improving the performance of TiO₂ photoelectrode. In this study, a composite of TiO₂/Co₃O₄ thin films was developed, and its performance in PEC water splitting was investigated. Co₃O₄ was synthesized using a hydrothermal method, and TiO₂ P25 was used. TiO₂ and Co₃O₄ were mixed by ball milling before coating on a clean FTO and annealing at 550 °C. Two weight variations of TiO₂:Co₃O₄ were used (95:5 and 90%:10%). XRD and FESEM analysis were used to investigate crystallinity phase and surface morphology. The optical band gap of the thin films was determined by UV-Vis spectroscopy, where the film with 90:10 weight ratio of TiO₂:Co₃O₄ obtained the smallest band gap of 2.9 eV. Co₃O₄ improved the current density and TiO₂ performance by approximately three times. (paper)