Building of CoFe2/CoFe2O4/MgO architectures: Structure, magnetism and surface functionalized by TiO2

Zhang

Beilstein J. Nanotechnol.

et al. 2019

In this work, sulfur-doped (S-doped) TiO2 with the (001) face exposed was synthesized by thermal chemical vapor deposition at 180 or 250 °C using S/Ti molar ratios R S/Ti of 0, 0.5, 1, 2, 3, 4 and 5. The S-doped samples synthesized at 250 °C exhibit a significantly improved photocatalytic performance. More precisely, S-doping has the following effects on the material: (1) S can adopt different chemical states in the samples. Specifically, it exists in the form of S2− replacing O2− at a ratio of R S/Ti = 1 and also in the form of S6+ replacing Ti4+ at R S/Ti ≥ 2. As a result, S-doping causes a lattice distortion, because the ionic radii of S2− and S6+ differ from that of the O2− and Ti4+ ions. (2) S-doping increases the adsorption coefficient A e for methylene blue (MB) from 0.9% to 68.5% due to the synergistic effects of the oxygen vacancies, increased number of surface chemical adsorption centers as a result of SO4 2− adsorption on the TiO2 surface and the larger pore size. (3) S-doping increases the MB degradation rate from 6.9 × 10−2 min−1 to 18.2 × 10−2 min−1 due to an increase in the amount of •OH and •O2− radicals.

Section: Resultsmentioning

confidence: 99%

Improved adsorption and degradation performance by S-doping of (001)-TiO₂

Zhang

Beilstein J. Nanotechnol.

et al. 2019

“…Therefore, more photogenerated holes (h + ) can transfer to the surface of particles and react with water or hydroxyl (─OH) to form hydroxyl radicals, i.e. h + + H 2 O → •OH + H + , as shown in Figure .…”

Section: Resultsmentioning

confidence: 99%

Improved photocatalytic performance of anatase TiO₂ synthesized through ethanol supercritical drying technique

Xian

Liu

Wang

et al. 2019

Applied Organom Chemis

Anatase titania (TiO 2 ) nanoparticles were synthesized via a self-developed ethanol vapor-thermal method at 240°C (T240) and 250°C (T250), i.e. at temperatures lower and higher, respectively, than the supercritical temperature (243.5°C, 7.0 MPa) of ethanol. Compared to T240, T250 exhibited a higher ratio of exposed (001) facets, oxygen vacancies, and concomitant TiO x . The specific surface area of T250 was 119.0 m 2 g −1 , smaller than that of T240 (144.2 m 2 g −1 ). During the degradation of methylene blue, T250 exhibited a high apparent rate constant (K app ) of 14.5 × 10 −2 min −1 , which was 6.3 times larger than that for T240. Furthermore, compared to T240, T250 exhibited better performance toward degradation of phenol. Results of electron spin resonance spectroscopy and photoluminescence indicated that the photogenerated electron-hole pairs possessed higher separation efficiency for T250 than for T240. In summary, the excellent photocatalytic performance of T250 originates from the higher ratios of exposed (001) facets, oxygen vacancies or TiO x , C═O groups adsorbed at the surface of particles, and higher separation efficiency of photogenerated electron-hole pairs. By employing this selfdeveloped vapor-thermal method, a variety of catalysts and their composites can be synthesized, which may exhibit novel morphological characteristics and properties as well as excellent photocatalytic performance.

“…The XPS spectrum of O 1s can be fitted by three peaks and the CSs correspond to TiO2, -OH, and Ov. [46] As the RS/Ti increases, the ratio of Ov increases from 4.3%…”

Section: Resultsmentioning

confidence: 98%

“…The holes react with water or hydroxyl groups to form hydroxyl radicals, i.e., h + + H2O →•OH + H + . [46] For the superoxide radical (•O2 − ), the peak height (h) in the 2-S0 sample is 2.2 ×10 5 . As RS/Ti increases, the peak height varies between 1.9 ×10 5 -2.5 ×10 5 .…”

Section: Resultsmentioning

confidence: 99%

Greatly improved adsorption and degradation by S-doped (001)-TiO₂ via the vapour-thermal method

Sun¹,

Zhang²,

Sun³

et al. 2019

Preprint

In this work, sulfur (S) doped (001)-face exposed TiO2 was synthesized via the vapor-thermal method at 180 °C or 250 °C, with an S/Ti molar ratio R S/Ti of 0, 0.5, 1, 2, 3, 4, and 5. The S-doped samples at 250 °C exhibited significantly improved photocatalytic performance. The effects of S doping were as follows: (1) The S element exhibits different chemical states in the samples with different R S/Ti. Specifically, it exists in the form of S2− replacing O2− at R S/Ti = 1, and S6+ replacing Ti4+ at R S/Ti ≥ 2. As a result, S doping causes a lattice distortion because the ionic radii of S2− and S6+ differ from that of the O2− and Ti4+. (2) S-doping increases the adsorption coefficient A e for methylene blue (MB) from 0.9% to 68.5% due to the synergistic effects of the oxygen vacancies, the SO4 2− adsorbed on the TiO2 surface, and the pore size. (3) S-doping increases the MB degradation rate from 6.9 × 10−2 min−1 to 18.2 × 10−2 min−1 due to an increase in the amount of •OH and •O2− radicals.