Ionic liquid–assisted hydrothermal synthesis of Nb/TiO2 nanocomposites for efficient photocatalytic hydrogen production and photodecolorization of Rhodamine B under UV-visible and visible light illuminations

Abstract

In this work, we reported synthesis of Nb/TiO2 nanoparticles (NPs) at 140°C in one day using an ionic liquid (IL)–assisted hydrothermal method using 1-butyl-2,3-dimethylimidazolium tetrafluoroborate as the IL and titanium (IV) isopropoxide and Niobium (V) Nitrate as precursors. Physicochemical properties of the obtained photocatalysts were investigated via thorough characterizations. The framework substitution of Nb in TiO2 NPs was established by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area, electron paramagnetic resonance, and energy dispersive X-ray spectroscopy techniques. XRD and transmission electron microscopy image results confirmed the anatase phase and nanocrystalline nature of Nb/TiO2. The optical properties revealed an extended tailing of the absorption edge toward the visible region upon Nb heterojunction. The concentration of Nb in the TiO2 matrix has been fine-tuned to improve the hydrogen production and photodecolorization of Rhodamine B dye. The synergy between the Nb and TiO2 has an optimum for concentration of 0.3 wt% Nb-doped TiO2. The optimized product has produced promising hydrogen evolution of 1146 μmol g−1 under illumination with a visible light source in a water/ethanol system. The optimized product that has shown promising photocatalytic detoxification ability of the material toward Rhodamine B dye was explored. Nb/TiO2 NPs was extracted after 1st use, then washed twice, and was dried at 80°C for 2 h. The dried powder was again used to reuse as a catalyst to degrade the dye and photocatalytic hydrogen generation for almost 6 cycles, and from the recycle and reusability studies, it was clear that the prepared 0.3 wt% Nb/TiO2 photocatalyst showed good photostability.