Oxygen vacancy mediated TiO2-x-MoS2/FTO heterostructure as an efficient photoanode for photoelectrochemical water splitting

To achieve a complete water splitting cycle, solar-assisted oxidation plays a crucial role. Discovering efficient photoanodes capable of absorbing visible light is essential to enable cost-effective solar energy conversion. This study devised an efficient hydrothermal method to synthesize a TiO₂-MoS₂ heterostructure with an oxygen vacancy on FTO (fluorine-doped tin oxide). The structure, morphology, optical properties, and photoelectrocatalytic behavior of the TiO_2-x-MoS₂ heterostructure using various techniques. The oxygen vacancy state can create a new sublevel state below the conduction band of TiO₂, which narrows the band gap to a lower level and thus extends the absorption edge into the visible region. The strategy of oxygen vacancy resulted in a photocurrent density of 0.6 mA cm^-2, which is 3 times higher than pure TiO₂. Also, the TiO_2-x-MoS₂ heterostructure exhibits a photocurrent density of 2.6 mA cm⁻² and higher O₂ evolution than pure TiO₂ in a 1.0 M KOH solution under UV–Vis irradiation. Compared to unmodified TiO₂ nanorods, TiO_2-x-MoS₂ electrodes exhibit an increase of 13 times in photoelectrochemical activity and have a low overpotential. This is due to accelerated electron transfer kinetics at the TiO_2-x-MoS₂ interface, an enhanced density of charge carriers, a reduced rate of charge recombination, and a highly wettable surface.