Mesoporous monolith designs of mixed phased titania codoped Sm3+/Er3+ composites: A super responsive visible light photocatalysts for organic pollutant clean-up

Abstract

In this work, we report on the synthesis of a new class photocatalyst material of Sm3+/Er3+ codoped TiO2 mesoporous monolithic network using a surfactant mediated microemulsion micro-phased sol-gel technique. The crack-free monoliths were characterized using, XRD, SEM-EDX, TEM-SAED, XPS, UV–Vis-DRS, PLS, TG-DTA, FT-IR, Raman, and BET analysis. The study revealed that the stoichiometric mixed dopant composite of Sm3+ and Er3+ with TiO2 exhibited excellent visible light photocatalytic activity. The XRD data showed that the Sm3+/Er3+ codoped TiO2 monolith exhibited a mixed phase ((75%) anatase - (25%) rutile) crystallinity, with well-defined mesopores. The TEM and SEM images confirmed the existence of a uniform pattern of highly ordered worm-like structure of mesoporous design, which corroborates with the absorption-desorption isotherm pattern. The XPS spectra confirmed the trivalent state of the Sm-Er composite, and their surface dispersion onto the Ti-O-Ti lattice. The UV–Vis-DRS analysis showed an energy band gap value of 3.26, 3.02, and 2.80 eV, for undoped, (3.0 mol%) Sm3+ doped, and (0.6 mol%) Er3+/(3.0 mol%) Sm3+ codoped TiO2 monoliths, respectively, which reflected on the visible light absorption characteristics of the Sm3+/Er3+ doped TiO2 composite. The photo-luminescence emission spectra showed that the (0.6 mol%) Er3+/(3.0 mol%) Sm3+ composite as the best performing visible light photocatalyst. The efficacy of the proposed class of photocatalytic materials was investigated for textile dye degradation using Acid Blue 113, as the model organic dye pollutant, which was dissipated within 30 min of visible light irradiation. For the superior performance of the photocatalyst, the operational parameters such as, solution pH, dopant/co-dopant stoichiometry, photocatalyst quantity, dye concentration, light intensity, photooxidizers, degradation kinetics, reusability, etc., were studied and optimized. The dye degradation was monitored using UV–Visible spectrophotometry, and the extent of dye mineralization was confirmed by TOC analysis.