Visible-light–responsive mesoporous N-doped TiO2 nanophotocatalyst for efficient Rhodamine B removal from water under direct sunlight

Abstract

The escalating presence of organic pollutants in water necessitates the development of advanced remediation technologies. Herein, we report the synthesis and characterization of a visible-light-active N-doped titania (N/TiO₂) photocatalyst, which was synthesized by a facile sol-gel of titanium butoxide and a benign N-dopant source. The synthesized anatase/brookite/rutile ternary phase N/TiO₂ material was characterized by XRD, XPS, EPR, SEM, TEM, BET, DRS, PL, EDS, FTIR, TGA, and Raman techniques, and its photocatalytic degradation was applied against Rhodamine B (RhB) dye from an aqueous solution. The key operating parameters, such as the amounts of N/TiO₂, initial RhB concentration, pH, and illumination duration, have been optimized to achieve the highest RhB degradation percentage. The findings demonstrated that N/TiO₂ possesses a mesoporous rutile-rich triphasic (51% anatase, 36% rutile, and 13% brookite) structure. Importantly, it displayed a higher degradation activity (99.3%) within 3h of sunlight irradiation at pH 7.0, along with a faster degradation rate (0.025 min⁻¹), which is 2.5 times faster than unoptimized N/TiO₂ and 5 times faster than undoped TiO₂ materials. Furthermore, a high reusability of the photocatalyst was observed over five cycles of photocatalytic reactions. This enhancement is attributed to the synergistic effect of optimal ternary phase, lower band gap energy, higher light absorption, well-separated charge carriers, and N-doping. Such optimized N-doped photocatalysts have practical applications for water-pollutant demineralization from water systems.