Herein, Cu was incorporated into ZnO lattice to reduce its band gap as well as to extend its visible radiation response. The obtained Cu-ZnO was continuously integrated with g-C3N4 to create ...Cu-ZnO/g-C3N4Z-direct scheme photocatalyst for advanced atrazine removal. Radical scavenging experiments have been also conducted to clearly figure out photocatalytic mechanism for degradation of atrazine by the synthesized photocatalyst. The synthesized Cu-ZnO only utilized the generated h+ for atrazine degradation (direct and indirect via formation hydroxyl radicals (•OH)) and the g-C3N4 only utilized the generated e− for atrazine degradation (indirect via reaction with O2 to form superoxide anion, which needed to continuously react with H2O to form •OH). Therefore, the photocatalytic atrazine degradation by synthesized Cu-ZnO material was greater than that by synthesized g-C3N4 material. Cu-ZnO/g-C3N4 utilized both generated e− and h+ for degradation of atrazine. Thus, the photocatalytic atrazine degradation by the synthesized Cu-ZnO/g-C3N4 was greater than those of single g-C3N4 or Cu-ZnO materials. Finally, the conducted recycling experiments indicated great stability of synthesized Cu-ZnO/g-C3N4 during long-term atrazine degradation process opening new era for application of the material in practical systems.
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•Cu doped into ZnO lattice to reduce its band gap and to extend its visible radiation response.•Cu-ZnO was successfully combined with g-C3N4 to establish Z direct scheme system.•Z-scheme prevented fast recombination of e− and h+ and maintained their re-dox potential.•The Cu-ZnO/g-C3N4 utilized both generated e− and h+ for degradation of atrazine.•The Cu-ZnO/g-C3N4 showed excellent activity and stability during long-term photocatalysis.
Approaches for the catalytic oxidation of biomass-based 5-hydroxymethylfurfural (HMF) into valuable chemicals are in great demand; however, their development is still challenging. Herein, we present ...nitrogen-doped manganese oxide (N-MnO
2
) catalysts that possess extraordinary catalytic performance (a >99.9% 2,5-diformylfuran selectivity, a 100% HMF conversion, and decent reusability) at room temperature without any additives. Structural changes,
i.e.
slight elongation of the Mn-O bonds and reduction of the coordination number of Mn sites, occur after doping of nitrogen into MnO
2
, as confirmed
via
characterization by extended X-ray absorption fine structure (EXAFS), H
2
-temperature programmed reduction (H
2
-TPR) and X-ray photoelectron spectroscopy (XPS). Mechanistic studies indicate that surface defect sites and coordinatively unsaturated Mn sites induced by nitrogen doping play a key role in promoting the oxidative activity.
Doping of nitrogen into MnO
2
is employed as an efficient catalyst for the catalytic oxidation of HMF to DFF under an oxygen atmosphere.
We successfully used Cu to dope into the NiWO4 crystal to prevent the fast recombination or increase the lifetime of the photo-induced h+ and e− of the material. Then, the synthesized Cu-NiWO4 was ...successfully hybridized with g-C3N4 to form Cu-NiWO4/g-C3N4 direct Z system for novel photocatalytic decomposition of n-hexane under vis-light. In the formed Cu-NiWO4/g-C3N4 Z direct system, photo-induced e− in Cu-NiWO4 CB associated with photo-induced h+ in g-C3N4 VB maintaining e− in g-C3N4 CB and h+ in Cu-NiWO4 VB, thereby synthesized photocatalysts formed abundant available e− and h+ amounts even excited by vis-light and the formed e− and h+ pairs exhibit suitable redox potentials for reactions with O2 and H2O, respectively, to produce strong oxidative radicals for advanced photocatalytic degradation of n-hexane. The highest removal efficiency and degradation degree of n-hexane photocatalyzed by Cu-NiWO4/g-C3N4 were 96.8 and 96.3%, respectively. The synthesized Cu-NiWO4/g-C3N4 material also demonstrated strongly stability during long time n-hexane removal.
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•Successfully doped Cu into NiWO4 lattice to enhance its photocatalytic activity.•Cu dopant prevented recombination of photo-excited e− and h+ of the NiWO4.•Cu-NiWO4 was successfully combined with g-C3N4 to establish Z direct scheme system.•Z-scheme prevented fast recombination of e− and h+ and remained their oxidative ability.•The Cu-NiWO4/g-C3N4 exhibited excellent photocatalytic degradation of gaseous n-hexane.
ZnO/graphene oxide (ZnO/GO) nanocomposites were synthesized by hydrothermal method using zinc acetate and graphite as precursors. Properties of synthesized materials were investigated by different ...physico-chemical techniques and their photocatalytic performance was evaluated with the aid of the photodegradation of methyl orange under UV irradiation. Impacts of reaction conditions such as pH of solutions, catalyst loading and initial concentration on photodegradation rate of synthesized photocatalysts were also investigated. TEM images showed that the average size of the synthesized ZnO was approximately 35 nm, being in good agreement with the obtained XRD results which revealed good dispersion of ZnO particles over the wrinkled GO layers. UV–Vis absorption spectra of these synthesized materials revealed that 5% ZnO/GO exhibited the highest visible light absorption. Photocatalytic experimental results showed that the highest photodegradation rates occurred in a neutral solution with an initial methyl orange (MO) concentration of 10 mg/L. After 2 h of reaction under UV irradiation, more than 95% of MO was degraded at optimal conditions. The photodegradation of MO followed the pseudo-first-order kinetics with apparent reaction rate constants in the range of 0.009–0.030 (min
−1
). ZnO/GO photocatalyst was relatively stable in neutral aqueous solutions during the photodegradation of MO, with a decrease of 6% in photocatalytic performance observed after four cycles compared with the first cycle.
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•Successfully doped V into TaON lattice to enhance its photocatalytic activity.•V dopant enhanced e−/h+ separation and prolonged the lifetime of the generated e− and h+.•The VTaON ...converted CO2 into CH4 and CO even under visible light.•The optimal V doping ratio enhancing photocatalytic activity of TaON was 1.5 wt%.
We successfully used V as dopant to enhance activity of TaON for visible light photocatalytic reduction of CO2 into valuable fuels. We investigated that the used V dopants existed in the TaON lattice and replaced several Ta elements in the lattice leading to decrease in the conduction band minimum and increase in the valence band maximum of the prepared VTaON. Hence, the band gap energy of the prepared VTaON was lower than that of prepared TaON or the prepared VTaON material could absorb significant amount of incident visible light for production of e− and h+ pairs, which participated in reactions with CO2 and H2O to generate CH4, CO, O2 and H2. We also investigated that the optimal V/Ta ratio (or optimal amount of V dopant) for maximum enhancing photocatalytic activity of TaON was 1.5 wt%. The prepared 1.5VTaON visible light photocatalytically converted CO2 with H2O to generate CH4, CO, O2 and H2 with generation rates of 673, 206, 1479 and 67 (µmol·g−1cat·h−1), respectively.
The α-Fe
2
O
3
/g-C
3
N
4
heterojunction was synthesized using a facile ultrasonic method using alpha hematite (α-Fe
2
O
3
) and graphitic carbon nitrite (g-C
3
N
4
) as precursors. These samples ...were characterized by advanced techniques such as SEM, EDX, XRD, PL and UV-Vis to investigate their morphology, elemental composition, crystalline structures and optical properties. Photocatalytic performance of these synthesized materials was investigated via degradation of tetracycline in the aqueous environment upon excitation of visible light. Obtained experimental results indicated that the synthesized α-Fe
2
O
3
/g-C
3
N
4
sample exhibited high photocatalytic activity for tetracycline degradation. The improvement in photocatalytic efficiency of the synthesized α-Fe
2
O
3
/g-C
3
N
4
was due to the Z-scheme mechanism, which effectively prevented electron-hole recombination or increased electron-hole separation efficiency for photocatalysis. The photocatalytic tetracycline degradation by the α-Fe
2
O
3
@g-C
3
N
4
followed the pseudo first-order model. The optimized pH for its photocatalysis was found to be 8. Finally, the synthesized material exhibited high stability after five recycling cycles.
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•Synthesized Ta3N5 and V–Ta3N5 successfully converted CO2 to valuable fuels.•V dopant enhanced electron–hole separation and prolonged its lifetime.•V–Ta3N5 exhibited great increases ...in light adsorption and decreases in band gap energy.•V–Ta3N5 reduced CO2 and H2O vapor to CH4, CO, O2, and H2 even under visible light.•A V/Ta ratio of 2wt.% was optimal for enhancing the photocatalytic activity of Ta3N5.
In this study, Ta3N5 and V-doped Ta3N5 (V–Ta3N5) were synthesized as catalysts for the conversion of CO2 into valuable fuels under visible light. As compared with Ta2O5, the synthesized Ta3N5 and V–Ta3N5 exhibited great increases in visible light adsorption and decreases in band gap energy. Therefore, the synthesized Ta3N5 and V–Ta3N5 photocatalytically converted CO2 into CO and CH4 even under visible light. The V dopants, which existed in the Ta3N5 lattice, could act as an intermediate band (V3d) between the valence band (N2p) and the conduction band (Ta5d) of the Ta3N5 to increase the electron–hole separation efficiency of the photocatalyst. Thus, the photocatalytic activity of V–Ta3N5 was much higher than that of Ta3N5. However, an increase in the V doping ratio led the formation of VN particles distributed on the Ta3N5 surface. The formed particles eclipsed the light reaching the photocatalyst surface, resulted in a decrease in photocatalytic activity. The optimal V doping ratio in V–Ta3N5 was found to be 2wt.%. As a result, the production rates of CH4, CO, O2, and H2 generated from the photocatalytic reduction of CO2 by 2wt.% V–Ta3N5 under visible light were 425, 236, 1003, and 56µmolg−1cath−1, respectively.
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In this study, we firstly aimed to use Nb as dopant to dope into the TiO2 lattice in order to narrow band gap energy or enhance photocatalytic activity of the Nb-TiO2. Then, the ...prepared Nb-TiO2 was combined with g-C3N4 to establish Nb-TiO2/g-C3N4 direct Z-scheme system for superior reduction of CO2 into valuable fuels even under visible light. The obtained results indicated that the band gap energy of the Nb-TiO2 (2.91 eV) was lower than that of the TiO2 (3.2 eV). In the successfully established Nb-TiO2/g-C3N4 direct Z-scheme system, the photo-excited e− in the CB of the Nb-TiO2 combined with the photo-excited h+ in the VB of the g-C3N4 preserving the existence of e− in the CB of the g-C3N4 and h+ in the VB of Nb-TiO2, and thereby, the system produced numerous amount of available e−/h+ pairs for the reduction of CO2 into various valuable fuels. In addition, the produced e− of the Nb-TiO2/g-C3N4 existing in the CB of the g-C3N4, which the potential energy is approximately −1.2 V, would be strong enough for the reduction of CO2 to generate not only CH4 and CO but also HCOOH. Among established Nb-TiO2/g-C3N4 materials, the 50Nb-TiO2/50 g-C3N4 material was the best material for the CO2 reduction.
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•Successfully doped Cu into NiWO4 crystal to improve its photocatalytic ability.•Cu dopant prevented e−/h+ recombination of the NiWO4.•The Cu-NiWO4 exhibited excellent photocatalytic ...degradation of gaseous benzene.•The optimal mole ratio of Cu/Ni in the Cu-NiWO4 for benzene removal was 3%.•The Cu-NiWO4 removed 97% benzene and mineralized 96.5% of them into CO2 and H2O.
We effectively used Cu dopant to improve photocatalytic performance of NiWO4 to remove benzene in air. The obtained experimental result indicated that photocatalytic performance of the prepared Cu-NiWO4 materials were greater than that of the pure NiWO4. This was because Cu effectively acted as novel dopant, which not only affected valence band (VB) top and conduction band (CB) bottom of NiWO4 but also formed a medium energy level between CB and VB of the NiWO4 to decrease its energy band gap and electron-hole recombination rate. Hence, the photocatalyst produced large available charge amounts (electron and hole) initiating photocatalysis for degradation of gaseous benzene. The optimized Cu/Ni mole ratio for maximum improving photocatalytic performance of NiWO4 was 3%. The maximum benzene removal efficiency and its mineralization via visible light photocatalysis of the 3Cu-NiWO4 were 93.7 and 96.5%, respectively. The synthesized Cu-NiWO4 photocatalyst also presented great stability in benzene removal processes.
There is an increasing research interest in indoor air quality at schools as children who are among the most sensitive to air pollution spend a lot of time indoors. This study aims to estimate BTEX ...levels, sources, and assess their health risk at ten preschools in Hanoi, Vietnam. Two sampling campaigns were conducted in November and December, 2017, and May and June, 2018, with a total of 80 samples collected. BTEX were sampled by mini air samplers, and the analysis was performed by using GC/MS. During class, indoor concentrations of benzene, toluene, ethylbenzene, and xylene were within the range of 1.22–6.01, 1.6–63.4, 0.94–6.34, and 0.86–3.52 μg m
−3
, while corresponding values obtained in the absence of children were 1.62–6.90, 1.20–125.3, 0.58–25.1, and 0.60–6.65 μg m
−3
, respectively. Indoor/outdoor ratios of BTEX varied from school to school, and ranged from 0.4 to 14.2, implying the presence of indoor emission sources. Insignificant indoor sources of benzene were found in all examined schools, whereas there were sources of toluene, ethylbenzene, and xylenes, probably associated with paint’s solvents, glues, and cleaning agents. Outdoor BTEX originated from the common sources, being mainly composed of automobile traffic. There was insignificant cancer and non-carcinogenic risk to children at the monitored preschools, with LCR values within the range of 0.059–6.6 × 10
−5
, and HQ values below 0.31. Monte Carlo simulation revealed that indoor and outdoor concentrations of BTEX influenced the most the results on lifetime cancer risk for indoors and outdoors, with a typical contribution of more than 90% to LCR variance.
