Multifunctional core-double-shell C@MnO@TiO2 catalysts with enhanced full-light conversion for the highly efficient photothermal oxidation of toluene

Abstract

In this study, the integrated core-double-shell structures of C@MnO@TiO2 (abbreviation CMT) composites have been rationally designed and fabricated utilizing of carbon spheres as frameworks and reducing agents, which were introduced a TiO2 outer shell on MnO2 @C nanospheres by sol-gel coating and subsequent in-situ calcination reduction process. Owing to the well-defined structures, the as-prepared CMT composites can efficiently convert full-light into heat energy, achieve the rapid adsorption and enrichment of toluene and motivate the synergistic effects of photocatalysis of TiO2 and full-light driven thermalcatalysis of MnOx @C, resulting in the significantly enhanced photothermal catalytic performance of toluene oxidation upon UV-Vis-IR irradiation of Xe lamp. Furthermore, the strategy on changing the molar ratio of Mn/Ti among CMT composites can not only act as important role in the control of the coating thickness of outer layer TiO2, surface morphologies and physicochemical properties within a certain range, but also yield opportunities to adjust photothermal synergistic effects between ternary components among CMT composites. Compared with other CMT composites, CMT-3 samples with a suitable Mn/Ti molar ratio of 0.4 exhibited much higher photothermal catalytic activity including a high toluene removal efficiency and CO2 production rate (99.1 % within 90 min and 102.5 μmol.g−1.min−1, respectively), which were attributed to its optimized coating thickness of outer layer TiO2, and the optimal distribution ratio of surface oxygen species (Oads/Olatt/Owat) and electronic valence of Mn species (Mn2+/Mn3+/Mn4+). The possible mechanism for photothermal catalytic oxidation of toluene over CMT composites was also discussed in terms of the special core-double-shell structure, matching electronic band levels and photothermal synergistic effects.