Heterometal Alkoxides as Precursors for the Preparation of Porous Fe– and Mn–TiO₂ Photocatalysts with High Efficiencies

Abstract

Transition-metal-doped titanium glycolates (M-TG, with M=Fe, Mn), which are the first non-stoichiometric heterometal alkoxides, have been synthesised through a solvothermal doping approach. X-ray diffraction, UV/Vis diffuse reflectance and ESR spectroscopy revealed that the dopant ion (Fe(3+) or Mn(2+)) is substituted for Ti(4+) in the TG lattice. Fe(3+) prolongs the crystallisation time of Fe-TG, whereas Mn(2+) has a smaller effect on the crystallisation time in comparison with Fe(3+). The as-synthesised M-TG materials were used directly as single-source precursors for the preparation of metal-doped titania (M-TiO(2)) through a simple thermal treatment process. The as-prepared M-TiO(2) materials maintain the rod-like morphology of the precursors and possess a mesoporous structure with high crystallinity. It has been proved that the dopant ions are incorporated into the TiO(2) lattice at the Ti(4+) positions. The photocatalytic activities of the M-TiO(2) materials obtained were evaluated by testing the degradation of phenol under UV irradiation. From the photocatalytic results, it was concluded that high crystallinity, a large surface area and appropriate transition-metal-doping are all beneficial to the enhancement of the photocatalytic performance of the doped TiO(2) material. In addition, it was noted that in comparison with Mn-TiO(2), Fe-TiO(2) shows higher photocatalytic activity due to the better inhibition effect of Fe(3+) on recombination of photogenerated electron-hole pairs. In contrast to the conventional nanosized TiO(2) photocatalyst, the micrometre-sized M-TiO(2) particles we obtained can be easily separated and recovered after the photocatalytic reactions.

Preparation and Characterization of Mn/N Co-Doped TiO2 Loaded on Wood-Based Activated Carbon Fiber and Its Visible Light Photodegradation

“…Moreover, Mn/Ti-N-WACF samples showed stronger visible light absorptions than Ti-WACF. The relatively strong absorption at 400-600 nm was attributed to the co-doping of N and Mn elements into the lattice of TiO 2 [38], and the chemical bonds of Ti-O-C rendered a red shift in the photo responding range and facilitated a more efficient utilization of light for the photocatalysis [39,40]. With the Mn doping content was increased, the visible light absorbance of the Mn/Ti-N-WACF samples was initially increased and then decreased.…”

Experimental Validation of the Importance of Thermally Stable Bulk Reduction States in TiO2for Gas Sensor Applications

“…[7] Typically, titanium glycolate (4.0 g), which was synthesized on a large scale according to the reported procedure, [22] was dispersed in water (300 mL) and then exposed to UV-light irradiation for 1 h. After the irradiation, the color of the solid sample turned from white (titanium glycolate) to intense blue because of the presence of Ti 3＋ . [7] Finally, the blue solid product was separated from the mixture and dried in air, the O 2 molecules of which oxidize the Ti 3＋ to Ti 4＋ because the Ti 3＋ species are on the surface (internal and external) of the solid.…”

Synthesis and Characterization of New Pentacoordinate Iron‐Based Aryloxide Complexes

“…In order to avoid the oxidation reaction, we directly used FeCl 3 and reacted it with LiOPh in a ratio of 1:5 in thf to obtain brown single crystals of [{(thf) 3 Li 3 Fe(OPh) 5 Cl} 3 ] n (2), which crystallize in the triclinic space group P1. The reaction takes place as a complete chloride substitution on the iron atom; however, LiCl is integrated into the final structure, as given by the following equation.…”

“…For several decades, intensive research in the chemistry of metal alkoxides or aryloxides [1][2][3][4][5][6][7][8] has developed, because of their interesting potential to serve many different applications for precursors of oxide materials such as LiCoO 2 , [7,9] as catalysts, [10][11][12][13] or as conducting materials. [9,14,15] Metal alkoxides have also been proposed as good precursors for ceramic materials based on high-purity metal oxides, because of their high solubility, low decomposition temperatures, [16] cross linking ability, and ease of modification.…”

“…Thus, various heterobimetallic compounds based on alkoxide or aryloxide ligands have been reported [2,4,8,15,17,20] for several interesting applications like precursors for porous iron, manganese, or titanium oxides in photocatalysts. [5] The synthesis of the single-molecule-like [(thf)NaFe(OtBu) 3 ] 2 [19] has been evaluated to be a good initiator for controlled ring-opening polymerization of rac-lactide. As cited before, iron alkoxide/ aryloxide complexes have particularly been shown to be interesting for several applications such as precursors for iron oxide nanoparticles, [15,21] or as catalysts.…”