Complex doping chemistry owing to Mn incorporation in nanocrystalline anatase TiO2 powders

Synthesis and Characterization of Manganese-Modified Black TiO2 Nanoparticles and Their Performance Evaluation for the Photodegradation of Phenolic Compounds from Wastewater

The release of phenolic-contaminated treated palm oil mill effluent (TPOME) poses a severe threat to human and environmental health. In this work, manganese-modified black TiO₂ (Mn-B-TiO₂) was produced for the photodegradation of high concentrations of total phenolic compounds from TPOME. A modified glycerol-assisted technique was used to synthesize visible-light-sensitive black TiO₂ nanoparticles (NPs), which were then calcined at 300 °C for 60 min for conversion to anatase crystalline phase. The black TiO₂ was further modified with manganese by utilizing a wet impregnation technique. Visible light absorption, charge carrier separation, and electron–hole pair recombination suppression were all improved when the band structure of TiO₂ was tuned by producing Ti³⁺ defect states. As a result of the enhanced optical and electrical characteristics of black TiO₂ NPs, phenolic compounds were removed from TPOME at a rate of 48.17%, which is 2.6 times higher than P25 (18%). When Mn was added to black TiO₂ NPs, the Ti ion in the TiO₂ lattice was replaced by Mn, causing a large redshift of the optical absorption edges and enhanced photodegradation of phenolic compounds from TPOME. The photodegradation efficiency of phenolic compounds by Mn-B-TiO₂ improved to 60.12% from 48.17% at 0.3 wt% Mn doping concentration. The removal efficiency of phenolic compounds from TPOME diminished when Mn doping exceeded the optimum threshold (0.3 wt%). According to the findings, Mn-modified black TiO₂ NPs are the most effective, as they combine the advantages of both black TiO₂ and Mn doping.

Enhanced Photoelectrochemical Properties from Mo-Doped TiO2 Nanotube Arrays Film

Mo-doped TiO2 nanotube arrays are prepared successfully by a combined method of direct current (DC) magnetron sputtering and anodic oxidation. The doping amount of Mo can be modified by changing the number of molybdenum blocks on the Ti target while a Ti–Mo alloy film is prepared by magnetron sputtering on a metal Ti substrate, following a Mo-doped TiO2 nanotube array grown by anodization. Morphology test shows that the doping of Mo could inhibit the phase transition and growth of crystal of TiO2. X-ray photoelectron spectroscopy (XPS) results show that Mo has successfully been embedded in the TiO2 crystal lattice and mainly exists in the valence states of Mo6+. Mo-doping samples show slightly increased visible light absorption as the red shift of TiO2 absorption edge with the band gap dropping from 3.24 to 3.16 eV with 0.5 at.% Mo doping. The enhanced photocurrent is demonstrated for a 0.5 at.% Mo-doped TiO2 electrode. Through photoelectric performance testing under UV-visible light irradiation, the nanotube array film with a Mo-doped content of 0.5% produced the maximum photocurrent density, which is about four times the undoped TiO2 nanotube array film, exhibiting a considerable photoelectric effect gain. The controllable Mo doping TiO2 nanotube array film prepared by this combining technique is expected as a promising material for efficient applications in photoelectric conversion.

Unraveling doping induced anatase–rutile phase transition in TiO2 using electron, X-ray and gamma-ray as spectroscopic probes

The present work reports the microscopic details of anatase (A) to rutile (R) phase transformation in a Mn-doped TiO₂ system.