What as perovskite. Perovskite was found to be

What kind of Chemist am I?

Perovskite is a calcium
titanium oxide (CaTiO3) mineral and the compounds which have the
same type of crystal structure as CaTiO3 (A2+B4+O2-3),
known as perovskite. Perovskite was found to be able to absorb sunlight
and generate electricity which made the researchers effectively use perovskite
in solar cells, for color displays and for catalytic converters.

Cerium
incorporated perovskite:-

1Yue’s
group studied the effects of cerium incorporation on the catalytic oxidation of
benzene over ?ame made perovskite La1?xCexMnO3
catalysts. It was found out that the incorporation of cerium improves the
benzene oxidation activity and the perovskite in which x was 0.1 exhibited
highest activity. Incorporating cerium and manganese was essential as the oxygen
storage capacity (OSC) is a characteristic property of Ce3+/Ce4+
ions and the synergistic effect between Ce3+/Ce4+ and Mn3+/Mn4+has
been known to enhance catalytic activity. The incorporation of cerium had a
negligible effect on the speci?c surface area of the perovskite and hence this
factor has little impact on the catalytic activity of perovskite. The
substitution of La3+ by Ce4+ resulted in an increase in
the surface Mn4+/Mn3+ ratio and a decrease in the surface
Oads/Olatt ratio due to charge neutralization. These
trends in the Mn4+/Mn3+ and Oads/Olatt
ratios exhibit good correlation with the catalytic activity during benzene
oxidation, indicating that the Ce4+ induced modi?cation of the Mn4+/Mn3+
ratio and the oxygen species was accompanied by enhanced catalytic activity.

Yang’s group
investigated photocatalytic decomposition of water to produce hydrogen under UV
radiation over layered perovskite KBi3PbTi5O16
photocatalyst synthesized by polymerized complex (PC) method. The perovskite
KBi3PbTi5O16 was synthesized by the PC
method at a lower calcination temperature (1073K, 2hrs) rather than the
conventional solid state (SS) reaction method which include higher calcination
temperature for a longer time (1273K, 6hrs). The photocatalyst was characterized by
X-ray diffraction, ultraviolet-visible spectra, Brunauer-Emmett-Teller specific
surface area, and FT-IR. The perovskite KBi3PbTi5O16
synthesized by PC method showed unique photocatalytic properties in the aqueous
solution containing cerium species. The drawbacks of the sample prepared by the
SS method which were a severe loss of alkaline-metal components and large grain
growth (surface area shrinkage by heat treatment at high temperature), which
may lead to low photcatalytic activities can be overcome by the preparation of
perovskite using the PC method. It
was found that the rate of hydrogen evolution was greatly improved and affected
over the perovskite by the addition of Ce(SO4)2 in an
aqueous suspension, which showed a volcano plot as a function of the
concentration of Ce(SO4)2 passing through the maximum
hydrogen evolution at Ce(SO4)2=2.4mM. This suggested
that perovskite essential promoters for hydrogen production in the cerium-containing
aqueous solution were the cerium(IV) cations adsorbed on the perovskite surface
as well as Ceaq3+ in the aqueous phase, which were
transformed from the Ceaq4+ species in the aqueous
solution of cerium(IV) sulfate during the induction period. Those cerium cation
promoters seem to be effectively recombining with the inhibitors of the
photoexcited electron and hole resulting in more efficient way of hydrogen
evolution by photocatalytic decomposition of water.

Song’s group
synthesized cerium and ytterbium codoped halide perovskite CsPbCl1.5Br1.5
quantum dots (QDs) to try to improve the photoelectric conversion efficiency
(PCE) of silicon solar cells (SSCs). They tried to overcome the limitation of
PCE for SSCs which can be attributed to the low spectral response at
ultraviolet (UV) and blue wavelengths (300–450 nm). So the incident photons of
higher energy within UV-blue wavelengths are absorbed within a short distance
from the surface, which results in high recombination loss. Considering the
downconversion or quantum cutting of rare earth (RE) ions approach, they tried
to improve the PCE where
by virtue of energy transfer processes between different RE centers, such as Ce3+
and Yb3+, quantum cutting can realize the emission of two or
multiple near-infrared photons for each ultraviolet/visible photon absorbed and
has potential to largely improve the PCE of SSCs as well as the other types of
solar cells. So it is expected that the introduction of some rare earth (RE)
ions with near-infrared emissions into lattices of the halide perovskite can
exhibit the excellent optical properties of both RE ions (long lifetime and
large Strokes shift) and the perovskite QDs (large absorption crosssection,
weak electron–phonon coupling and high luminescence quantum yield) expand their
optical properties. They synthesized various Yb3+doped, Yb3+,
Er3+, and Yb3+, Ce3+ codoped CsPbClxBr3?x
QDs, and their films was successfully self assembled by liquid-phase depositing
method in front of SSCs resulting in an extraordinary enhancement of PCE from
18.1 % to 21.5 %. The larger absorption cross-section, weaker electron–phonon
coupling and higher inner luminescent quantum yield contributed to successfully
explore the doped perovskite nanocrystals as a downconverter of commercial SSCs.

4Christou
and coworkers synthesize 3-D perovskite Ce3Mn8O8(O2CPh)18(HO2CPh)2
(CeIII2CeIVMnIII8) at
high temperature in the solid state. The structure was determined by
single-crystal X-ray diffractometry and consists of a {CeIVMnIII8(?3-O)8}12+
unit comprising a Mn8 distorted cube with a CeIV at its
center held together by four ?3-O2? and four ?4-O2?
ions, with the latter connecting to two external CeIII ions attached
on opposite faces of the cube. The organic ligation consists of two ?4-,
four ?3-, and twelve ?2- benzoate groups, as well as two
terminal benzoic acid groups on the CeIII ions. All MnIII atoms
are six-coordinate with distorted octahedral geometries and exhibit Jahn–Teller
(JT) distortion axes. The CeIII and CeIV ions are
nine-coordinate and eight-coordinate, respectively. The
magnetic studies showed that Ce3Mn8 exhibits both in pair
MnIII2 ferromagnetic and antiferromagnetic exchange
interactions and the resultant spin vector alignments were within the 3-D
C-type antiferromagnetic perovskite. Also from first-principles theoretical
calculations, it was revealed that the expected nearest-neighbor MnIII2
exchange couplings via superexchange pathways through bridging ligands and an
unusual, direct MnIII–CeIV–MnIII
metal-to-metal channel involving the CeIV f orbitals.

I would like to carry
out research mainly on the synthesis of perovskites involving cerium atom and
find their application in various fields. The various oxidation state of cerium
helps to use cerium as a catalyst. Also they exhibit colossal magnetoresistance
and multiferroicity, therefore these materials have potential applications in
many technological ?elds such as spintronics and information storage.

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Refrences:

1.      Gang
Liu, Jiaqi Li, Kun Yang, Wenxiang Tang, Haidi Liu, Jun Yang, Renliang Yue??, Yunf Chen?
Particuology 2015, 19, 60–68

2.      Chong-Heng He†, O-Bong Yang* Ind. Eng. Chem. Res. 2003, 42, 419-425

3.      Donglei Zhou, Dali Liu, Gencai Pan, Xu
Chen, Dongyu Li, Wen Xu,* Xue Bai, Hongwei Song* Adv. Mater. 2017, 29, 1704149

4.      Annaliese E. Thuijs1, Xiang-Guo
Li2, Yun-Peng Wang2, Khalil A. Abboud1, X.-G.
Zhang2, Hai-Ping Cheng2, George Christou1 Nat. Commun. 2017, 8, 500