Novel LaFeO
3
/Ag
2
CO
3
nanocomposites
are synthesized by co-precipitation method for photocatalytic degradation
of Rhodamine B (RhB) and
p
-chlorophenol under visible
light irradiation. Heterostructures between LaFeO
3
and
Ag
2
CO
3
semiconductors are formed during the
synthesis of these nanocomposites. Among the nanocomposites prepared
with different ratios of LaFeO
3
and Ag
2
CO
3
, 1% LaFeO
3
/Ag
2
CO
3
shows
the highest photocatalytic activity for the degradation of RhB. Maximum
electron–hole pair decoupling efficiency is observed in 1%
LaFeO
3
/Ag
2
CO
3
, which causes the greater
activity of the heterostructure. Degradation efficiency of 99.5% for
RhB and 59% for
p
-chlorophenol has been obtained
under natural sunlight within 45 min. Interestingly, the stability
of Ag
2
CO
3
is improved dramatically after making
nanocomposite, and no decomposition of the catalyst was observed even
after several photocatalytic cycles. Reactive oxygen species scavenging
experiments with
p
-benzoquinone, isopropyl alcohol,
and ammonium oxalate suggest that a major degradation process is caused
by holes. Degradation of RhB into small organic moieties is detected
using LC–MS technique. Further, the efficient mineralization
of the degradation products occurs during the catalytic process.
Bismuth based host materials for doping rare earth ions gained considerable interest due to the possibility of forming crystalline homogeneous solid solution phases over a wide range and their excellent luminescent properties. In the present manuscript, a facile synthesis method for preparation of nanocrystalline NaBi(MoO 4 ) 2 and their optical properties are presented. The influence of various synthetic parameters such as precursor concentration, reaction time and reaction temperature on phase formation have been investigated and revealed that these nanoparticles can be synthesized even at 5 °C within 5 min with a Bi/Mo ratio of 1:4. All the doped and undoped samples show scheelite type tetragonal structure. Formation of solid solution between NaBi(MoO 4 ) 2 and NaEu(MoO 4 ) 2 over the complete range of compositions could be achieved. A systematic decrease in the unit cell parameters is observed with increasing concentration of Eu 3+ ion in NaBi 1−x Eu x (MoO 4 ) 2 . Investigations on the luminescence properties of europium doped samples show excellent red luminescence upon excitation at 465 nm. The quantum efficiency calculated from experimental luminescence studies shows optimum photoluminescence properties in NaBi 0.9 Eu 0.1 (MoO 4 ) 2 nanoparticles with the highest quantum efficiency of 50%.
Water oxidation is an energy-consuming,
four-electron-transfer
reaction and is essential for solar fuel production from water. Catalysts
based on precious metals such as RuO2 and IrO2 show high efficiency for oxygen evolution reaction. However, these
catalysts are less abundant and expensive. To date, earth-abundant
water oxidation catalysts still exhibit less activity for water oxidation.
Herein, we report the synthesis of high surface area Mn2O3 nanomaterials for an efficient photocatalytic water
oxidation catalyst. The synthesis process involves three simple steps.
In the first step, CaMnO3 is synthesized by the citrate-gel
method. In the second step, CaMnO3 is transformed into
freestanding layers of ε-MnO2 by selective removal
of Ca2+. In the third step, these layers are converted
into irregularly shaped two-dimensional Mn2O3 flakes (AD-Mn2O3) by calcination at 550 °C.
These AD-Mn2O3 nanostructures show 4 times higher
surface area (127 m2 g–1) when compared
to the irregularly shaped Mn2O3 nanoparticles
(CG-Mn2O3) synthesized by the citrate-gel method
at the same temperature. The AD-Mn2O3 nanostructures
show super hydrophilicity with a contact angle of zero degree. This
material exhibits excellent photocatalytic water oxidation activity
with a turnover frequency of 1.53 × 10–3 s–1, which is twice the activity shown by CG-Mn2O3. This study can help in developing an earth-abundant,
cost-effective, efficient catalyst for overall water splitting.
Nanomaterials of
NaBi0.9Eu0.1(MoO4)2 were
prepared by a simple coprecipitation method in
ethylene glycol medium at room temperature. Substitution of bismuth
with lanthanum resulted a single-phase solid solution (NaBi0.9–x
La
x
Eu0.1(MoO4)2, 0.0 ≤ x ≤ 0.9)
in the complete range of compositions. The linear relationship observed
for unit cell parameters, Raman shifts, and FTIR peak positions with
lanthanum concentration confirmed the solid solution formation.
The band gap of the NaBi0.9–x
La
x
Eu0.1(MoO4)2 nanomaterials widens from 3.36 to 4.4 eV with increasing La3+ concentration in these solid solutions. These nanomaterials
show strong red emission upon excitation with UV–visible light.
The emission properties of Eu3+ are improving with increasing
the La3+ content. The band gap of the solid solution plays
a crucial role in the improvement of emission properties and is highly
dependent on the excitation wavelength. This improvement is marginal
while exciting with 464 nm light due to the reduction in the inter
Eu3+ ion energy transfer brought by the lattice expansion,
whereas drastic improvement is observed when exciting at 280 and 394
nm light due to the combined effect of band gap and lattice expansion.
The quantum efficiency estimated from emission spectra and excited
state lifetime values revealed that NaLa0.9Eu0.1(MoO4)2 nanomaterials are best in the series
with ∼70% efficiency. These materials can be a suitable red
phosphor for white light-emitting diodes (WLEDs)
Er3+, Yb3+ co-doped NaBi(MoO4)2 nanomaterials show excitation dependent photoluminescence properties in the visible and NIR regions upon excitation with UV, visible and NIR light.
Artificial photosynthesis is a promising method that directly transforms solar energy into chemical energy. To achieve artificial photosynthesis, efficient water oxidation catalysts (WOCs) are essential. In nature, the manganese-oxo-calcium cluster...
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