Covalently functionalized TiO₂ with ionic liquid: A high-performance catalyst for photoelectrochemical water oxidation

Ionic liquid (IL) [BsAIm][HSO₄] was covalently introduced to TiO₂ through a simple route. The synthesized IL-TiO₂ hybrid was thoroughly studied by using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The as-prepared IL-TiO₂ not only exhibits a significantly enhanced photoelectrochemical (PEC) activity, which is almost ten-fold higher than that of the bare TiO₂, but also possesses promising photo-stability under continuous working conditions. Based on the results, such as charge transfer efficiency, UV-Vis absorption spectroscopy, photoluminescence (PL) emission spectroscopy, and incident-photon-to-current-conversion efficiency (IPCE) tests, we propose a reasonable mechanism to understand the enhanced performance of the IL-TiO₂ toward PEC water oxidation. The significant enhanced PEC performance of IL-TiO₂ should be ascribed to a synergistic effect between covalently linked IL units and TiO₂ particles.