The MnO(x) and CeO(x) were in situ supported on carbon nanotubes (CNTs) by a poly(sodium 4-styrenesulfonate) assisted reflux route for the low-temperature selective catalytic reduction (SCR) of NO with NH(3). X-Ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), H(2) temperature-programmed reduction (H(2)-TPR) and NH(3) temperature-programmed desorption (NH(3)-TPD) have been used to elucidate the structure and surface properties of the obtained catalysts. It was found that the in situ prepared catalyst exhibited the highest activity and the most extensive operating-temperature window, compared to the catalysts prepared by impregnation or mechanically mixed methods. The XRD and TEM results indicated that the manganese oxide and cerium oxide species had a good dispersion on the CNT surface. The XPS results demonstrated that the higher atomic concentration of Mn existed on the surface of CNTs and the more chemisorbed oxygen species exist. The H(2)-TPR results suggested that there was a strong interaction between the manganese oxide and cerium oxide on the surface of CNTs. The NH(3)-TPD results demonstrated that the catalysts presented a larger acid amount and stronger acid strength. In addition, the obtained catalysts exhibited much higher SO(2)-tolerance and improved the water-resistance as compared to that prepared by impregnation or mechanically mixed methods.
Nanoflaky MnO(x) on carbon nanotubes (nf-MnO(x)@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH₃. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N₂ adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H₂ temperature-programmed reduction (H₂-TPR) and NH₃ temperature-programmed desorption (NH₃-TPD). The SEM, TEM, XRD results and N₂ adsorption-desorption analysis indicated that the CNTs were surrounded by nanoflaky MnO(x) and the obtained catalyst exhibited a large surface area as well. Compared with the MnO(x)/CNT and MnO(x)/TiO₂ catalysts prepared by an impregnation method, the nf-MnO(x)@CNTs presented better NH₃-SCR activity at low temperature and a more extensive operating temperature window. The XPS results showed that a higher atomic concentration of Mn(4+) and more chemisorbed oxygen species existed on the surface of CNTs for nf-MnO(x)@CNTs. The H₂-TPR and NH₃-TPD results demonstrated that the nf-MnO(x)@CNTs possessed stronger reducing ability, more acid sites and stronger acid strength than the other two catalysts. Based on the above mentioned favourable properties, the nf-MnO(x)@CNT catalyst has an excellent performance in the low-temperature SCR of NO to N₂ with NH₃. In addition, the nf-MnO(x)@CNT catalyst also presented favourable stability and H₂O resistance.
In
this work, n–p heterostructure SnO2/BiOI photocatalyst
was successfully fabricated through a facile chemical bath method.
The photocatalysts was applied to minimize antibiotic oxytetracycline
hydrochloride (OTTCH) and methyl orange (MO) under visible light irradiation.
SnO2/BiOI composite exhibited excellent photocatalytic
performance for the refractory pollutant OTTCH and MO decomposition.
The sample of 30 wt % SnO2/BiOI possessed the best photocatalytic
performance in all the obtained catalysts. Several reaction parameters
affecting OTTCH degradation such as initial concentration, ion species,
and concentration were investigated systematically. The optical and
electrical properties of materials demonstrate that the transfer rate
of electron–hole pairs dramatically improve though forming
an n–p junction in SnO2/BiOI hybrid. Moreover, the
energy band alignments of SnO2/BiOI junction were confirmed
via combining DRS and XPS analysis, which provided strong support
for the proposed mechanism. This work could provide a new approach
to construct new p–n junction photocatalysts and a reference
for the study of other heterojunction catalysts.
Upgrading
corncob residues (CCR) to a high quality energy resource
is an effective utilization of an underutilized industrial lignocellulose
waste. A hydrothermal carbonization technique was therefore employed
to generate a high heating value (HHV) hydrochar. Results showed that
its HHV increased 47% after treatment at 230 °C for 1.5 h. Decreases
in H/C and O/C verified that reductions in C and O reactions were
occurring following hydrothermal carbonization. The chemical and thermal
properties of the final hydrochar as analyzed by FT-IR, TG/DTG, and
XRD analyses indicated that dehydration and decarboxylation were the
predominant pathways for the C and O reductions. The present hydrothermal
carbonization process is offered as a promising approach to upgrade
CCR to a high heating value hydrochar under mild conditions.
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