Photoelectrochemical properties of MOF-induced surface-modified TiO2 photoelectrode

Abstract

Heteroatom doping and surface modification with oxides are both important strategies to improve the photoelectrochemical (PEC) activities of TiO₂ photoelectrodes. However, it is difficult to combine the two strategies into a single synthesis process. Herein, a simple one-pot synthesis method was developed to modify a TiO₂ photoelectrode surface by N-doping while simultaneously modifying the surface with In₂O₃ and NiO. This method involved growing MOF onto a TiO₂ surface with N-containing organic ligands and In and Ni salts as metal precursors, followed by heat treatment at 600 °C. The roles of heteroatom doping and oxide modification are proposed as follows. (i) N-Doping extends the absorption edge of the TiO₂ to a longer wavelength region and enhances visible light absorption. (ii) N-Doping together with the passivation of TiO₂ surface trap states by oxide modification increases the donor density in TiO₂. (iii) The generated suitable interfaces on the surface of TiO₂ facilitate photogenerated charge separation and transfer. In comparison with the pristine TiO₂ photoelectrode, the metal oxide- and heteroatom-modified TiO₂ photoelectrode exhibits superior photoelectrochemical performance under both simulated sunlight and visible light illumination. Suitable substrate of the electrode, appropriate size of the as-synthesized MOF precursors, and choice of ligands and metal ions are important factors for this strategy.