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

• Ionic liquid (IL) modified TiO2 was prepared as a novel OER photocatalyst.
• The PEC activity of TiO2 was enhanced due to the modification of IL.
• The inorganic anions of IL could decrease the surface pH value of TiO2.
• Synergistic effect between IL and TiO2 attributes to the improved PEC activity.

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.

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