Activation of Peroxymonosulfate by Oxygen Vacancies-Enriched Cobalt-Doped Black TiO₂ Nanotubes for the Removal of Organic Pollutants

Abstract

Cobalt-mediated activation of peroxymonosulfate (PMS) has been widely investigated for the oxidation of organic pollutants. Herein, we employ cobalt-doped Black TiO2 nanotubes (Co-Black TNT) for the efficient, stable, and reusable activator of PMS for the degradation of organic pollutants. Co-Black TNTs induce the activation of PMS by itself and stabilized oxygen vacancies that enhance the bonding with PMS and provide catalytic active sites for PMS activation. A relatively high electronic conductivity associated with the coexistence of Ti4+ and Ti3+ in Co-Black TNT enables an efficient electron transfer between PMS and the catalyst. As a result, Co-Black TNT is an effective catalyst for PMS activation, leading to the degradation of selected organic pollutants when compared to other TNTs (TNT, Co-TNT, and Black TNT) and other Co-based materials (Co3O4, Co-TiO2, CoFe2O4, and Co3O4/rGO). The observed organic compound degradation kinetics are retarded in the presence of methanol and natural organic matter as sulfate radical scavengers. These results demonstrate that sulfate radical is the primary oxidant generated via PMS activation on Co-Black TNT. The strong interaction between Co and TiO2 through Co–O–Ti bonds and rapid redox cycle of Co2+/Co3+ in Co-Black TNT prevents cobalt leaching and enhances catalyst stability over a wide pH range and repetitive uses of the catalyst. Electrode-supported Co-Black TNT facilitates the recovery of the catalyst from the treated water.

A solar photothermocatalytic approach for the CO2 conversion: Investigation of different synergisms on CoO-CuO/brookite TiO2-CeO2 catalysts

“…Notably, the addition of the metal oxide species resulted in a further decrease of the PL bands of TiO2 and CeO2. A broad band is visible in the 480-510 nm range for the Co/TiCe3 sample probably due to the formation of oxygen vacancies induced by the cobalt oxide [40]. In fact, the presence of small amounts of metal nanoxides, and in particular of cobalt oxides, facilitated the creation of new oxygen vacancies as intrinsic defects inside the principal oxide (in this case the TiO2-CeO2 system) [41].…”

Synthesis of Ce-doped Mn3Gd7−xCex(SiO4)6O1.5 for the enhanced catalytic ozonation of tetracycline

“…The O 1s XPS spectra were deconvoluted with three major peaks, located at 529.9 eV, 531.8 eV, and 532.6 eV, which correspond to lattice oxygen species (O 2 − ) named O I and adsorbed oxygen (e.g., O 2 2− and O − ), and hydroxyl groups (OH − ), respectively 29 named O II . The atom ratio of O I to O II was 4.02 for Mn 3 Gd 5.5 Ce 1.5 (SiO 4 ) 6 O 1.5 , which is higher than that of Mn 3 Gd 7 (SiO 4 ) 6 O 1.5 to 3.17, respectively, indicating that the doping of Ce increased the oxygen defects of Mn 3 Gd 7 (SiO 4 ) 6 O 1.5, which is the most active oxygen, and has been reported to play an important role in the oxidation reaction 30 . Otherwise, the EPR comparative experiment of Mn 3 Gd 7 (SiO 4 ) 6 O 1.5 and Mn 3 Gd 5.5 Ce 1.5 (SiO 4 ) 6 O 1.5 is shown in Fig.…”

Defect Engineering of Photocatalysts for Solar Energy Conversion

“…In typical circumstances, manifold defects have been appeared in various semiconductors. For example, OVs confined in black TiO 2 were produced through hydrogen treatment, corresponding the existence of hydrogen dopants . Meanwhile, OVs confined in Bi 2 WO 6 nanosheets with the existence of Nb 5+ dopants were produced through the partial substitution of W 6+ ions in Bi 2 WO 6 nanosheets by Nb 5+ ions, improving the light absorption and charge separation .…”

“…For example, OVs confined in black TiO 2 were produced through hydrogen treatment, corresponding the existence of hydrogen dopants. [58] Meanwhile, OVs confined in Bi 2 WO 6 nanosheets with the existence of Nb 5þ dopants were produced through the partial substitution of W 6þ ions in Bi 2 WO 6 nanosheets by Nb 5þ ions, improving the light absorption and charge separation. [59] According to the locations of the defects in different photocatalysts, the defects can be divided into bulk defects, surface defects, interfacial defects, respectively.…”