Solid-State ¹³C NMR Characterization of Carbon-Modified TiO₂

Abstract

Abstract13C-modified TiO2 was prepared to facilitate study of the dopant atoms and trace their chemical fate throughout the process. In the preannealed material, NMR showed strong evidence of many Ti−O−C bonds. After annealing, surface-bound coke is a major component. NMR also showed that a washing step before annealing led to the generation of orthocarbonate (C(OR)4) centers, observed at 126 ppm, which are located deep inside the TiO2 particles. Both NMR and XPS confirmed the presence of small amounts of regular sp2-hybridized carbonate species in all briefly annealed samples, while annealing for longer times led to a reduction removal of the COn centers. Quantitative NMR also shows the degree of carbon loss that accompanies annealing. Some variation in the chemical degradation of quinoline is noted among the catalysts, but coke-containing TiO2 catalysts are not qualitatively better catalysts for use with visible light with this substrate. DisciplinesChemistry | Organic Chemistry | Other Chemistry | Polymer Chemistry CommentsReprinted (adapted) with permission from Chemistry of Materials, 21(7);

Enhanced photocatalytic activity of C–N-codoped TiO2 films prepared via an organic-free approach

“…3a and b). The C 1s spectrum shows a single strong peak at 284.6 eV and a weak shoulder at around 288.5 eV, which are attributed to the presence of adventitious elemental carbon and C-O bond, respectively [42][43][44]. Generally, the C-O band at 288.5 eV has been considered as the formation of Ti-O-C bond due to the substitution of carbon for some of the lattice titanium atoms, though this peak may come from the surface functional group of carbon black [41][42][43].…”

“…The peak at around 281.0 eV of Ti-C bond was not observed in these samples, which suggests that carbon did not substitute for oxygen atom in the lattice of TiO 2 in the current system. It has been reported that the carbon doping states and species cannot be directly confirmed by only analyzing the XPS C 1s spectra [42,44]. Further analysis of the XPS Ti 2p spectra can help to investigate the carbon doping state, because carbon-doping can lead to the formation of oxygen vacancies and Ti 3+ defects and result in a slight shift of the Ti 2p peaks toward the lower binding energy [42][43][44].…”

Synthesis of activated carbon-surrounded and carbon-doped anatase TiO2 nanocomposites

“…Generally, the C-O bond has been considered as the formation of Ti-O-C bond due to carbon doping, though this peak may come from the surface functional group of the AC. [42][43][44][45] Besides the C-C bond, there are two peaks for sample A (see Fig. S3 in the ESI †), though it is not active under visible-light irradiation.…”

“…Hence, carbon doping cannot be directly confirmed by only analyzing the XPS C 1s spectra. 45 Carbon-doping accompanies the formation of oxygen vacancies and Ti 3+ defects, resulting in slight shifts of the Ti 2p peak toward the lower binding energy. [42][43][44][45] Hence, the red shifts of the Ti 2p peak in comparison with undoped TiO 2 are used to highlight the successful carbondoping into the TiO 2 lattice.…”

Cotton fibers nano-TiO2 composites prepared by as-assembly process and the photocatalytic activities

“…The main ingredient of cotton fiber is cellulose, a linear polymer of D-glucose with 3 hydroxyl groups on C-2, C-3 and C-6 in the 6-member cycle chain. These polar groups can adsorb the nanoparticles via oxygen bonding [1]. However, the carboxylic group is more polar than the hydroxyl one, as well it has a stronger interaction with the hydroxylic group on the nanoparticle surface [2,3].…”