Promoting effect and mechanism of neodymium on low-temperature selective catalytic reduction with NH3 over Mn/TiO2 catalysts

Series of Mn/TiO2 catalysts modified with various contents of Nd for low-temperature SCR were synthesized.It can be found that the appropriate amount of Nd can markedly reduce the take-off temperature of Mn/TiO2 catalyst to 80℃and NOx conversion is stabilized over 90%in the wide temperature range of 100-2600 C.0.1 Nd-Mn/Ti shows higher N2 selectivity and better SO2 resistance than Mn/Ti catalyst.The results reveal that Nd-doped Mn/TiO2 catalyst exhibits larger BET surface area and better dispersion of active component Mn2O3.XPS results indicate that the optimal 0.1 Nd-Mn/Ti sample possesses higher concentration of Mn4+and larger amount of adsorbed oxygen at the surface compared with the unmodified counterpart.In situ DRIFTS show that the surface acidity is evidently increased after adding Nd,especially,the Lewis acid sites,and the intermediate(-NH2)is more stable.The reaction mechanism over Mn/Ti and 0.1 Nd-Mn/Ti catalysts obey the Eley-Rideal(E-R)mechanisms under low temperature reaction conditions.H2-TPR results show that Nd-Mn/TiO2 catalyst exhibits better lowtemperature redox properties.

Synthesis and optical characterization of Eu^(2+),Tb^(3+)-codoped Sr_3Y(PO_4)_3 green phosphors

A series of Eu^2＋,Tb^3＋-codoped Sr3 Y（PO4）3（SYP） green phosphors were synthesized by hightemperature solid-state reaction. Several techniques, such as X-ray diffraction, UV-vis spectrum,and photoluminescence spectrum, were used to investigate the obtained phosphors. The present study investigates in detail photoluminescence excitation and emission properties, energy transfer between the two dopants, and effects of doping ions on optical band gap. SYP：0.05 Eu2＋ phosphor shows an intense and broad excitation band ranging from 220 to 400 nm and exhibits a bright green emission band with CIE chromaticity coordinates（0.189, 0.359） under 350 nm excitation. Green emission of SYP：0.03 Tb3＋ is intensified by codoping with Eu^2＋, and energy transfer mechanism between them is demonstrated to be a dipole-dipole interaction. Upon 350 nm excitation, SYP：Eu^2＋,Tb^3＋ phosphors exhibits two dominating bands peaking at 466 and 545 nm, which are assigned to 4 f^65 d^1→4 f^7 transition of Eu^2＋ ions and ~5 D4→~7 F5 transition of Tb^3＋ ions, respectively. Optimal doping concentrations of Eu^2＋ and Tb^3＋ in the SYP host are 5 mol% and 15 mol%, respectively. Results indicate that SYP：Eu^2＋,Tb^3＋ phosphors are potentially used as green-emitting phosphors for white light-emitting diodes.