xúc tác perovkite

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Xúc tác Perovkite

Nguyn Tn Tài

Võ c Minh Minh

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PEROVKITE1. T ng quan

2. Gi i thiu v Perovkite

3. Ph ng pháp tng h p

4.  ng dng

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1. Tng quan

Tình hình ô nhim môi trng hin nay

Tác hi ca VOCs và CO trong khí thiCác phng pháp x lý khí thi ã c

nghiên cu và ng dng

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Phng pháp hp thPhng pháp hp phPhng pháp gia nhit (t cháy trctip)phng pháp oxy hóa trên xúc tác

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2. Gi i thiu v perovkite1. nh ngha

2. Cu trúc ² phân loi

3. Tính cht

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2.1- nh nghaVt liu Perovkite có công thc chung

A1A2B1B2O3

A1: nguyên t h Lantan (thông th ng là La,ôi khi có th là Ce, Pr, Nd)

A2: kim loi kim th (Ca, Ba, Sr..)

B1, B2: kim loi chuyn tip (Co, Mn, Fe, Cr,

Cu, V«) hoc là nhng kim loi quý A2, B2: nhng nguyn t thay th A1, A2

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Perovskite structur e. The r ed spher es ar e 

oxygen atoms,the deep blue ar e smaller metalcations and the gr een/blue ar e the larger metalcations

2.2- Cu trúc ± phân loi

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Perovskite th ng có công thc ABO3

(A có kích th c l n h n B ):

1. A: cation hóa tr 2, B: cation hóa tr

4. Ví d: CaTiO3, BaTiO3« CaTiO3

SrTiO3

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BaTiO3SrRuO3

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2. A, B: cation hóa tr 3. Ví d: LaMnO3,LaCoO3, LaAlO3«

(tn tài kim vài hình v các cht nàythêm vào)

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3. A: cation hóa tr 1, B: cation hóa tr5. Ví d: NaCrO3, NaWO3, NaNbO3«

NaTaO3

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 in tích ca các cation A, B có ththay i nhng tng in tích ca

chúng phi bng 6.

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 iu kin bn vng rA > 0.9 A0

rB > 0.51 A0

0.78 < t < 1.05 t: h s Goldschmidt

)(*2B A

 B A

r r r r t 

!

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Cu trúc lý tng caperoskite Cu trúc peroskite b

méo dng do s saikhác ca ng kínhcác ion

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Halide perovskiteHn h p hu c ² vô c 

1. Anion [MX6]4- vô c 

2. Cation hu c [ ammonuim ion v ichiu dài mch C (1-16)«]

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(2-Br PEA)2SnI4

viewed from the "side". 

Cation:phenethylammonium

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(2-Br PEA)2SnI4viewed from the "top"

Công thcchung  A2BX4

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Oxygen- deficient

peroskite Công thc REBaM2O5

RE : nguyên t t him

M : Mn, Co, Fe«

YBaMn2O5

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Crystal structur e of YBaMn2O5 in space group P4/nmm. The r ed atoms ar e oxygen, the gr eenatoms ar e barium,the blue atoms ar e yttrium, and the purple atoms ar e manganese. 

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The red,white and

gray atomsare oxygen,Mn2+ and

Mn3+

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2.3- Tính cht t tính (st t hay phn st t )

in ( siêu dn hay cách in, in tr 

siêu khng l CMR ) kh nng bn nhit

Hp ph

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3. Ph ng pháp tng h p t nhiên:Perovskite is found in contact metamorphic rocks

and associated mafic intrusives.

It is found in some silica-undersaturated igneousrocks, such as nepheline syenite and melilitite, andrare carbonatites.

Perovskite also is a common mineral in the Ca-Al-richinclusions (CAIs) found in some chondriticmeteorites

Nhân to ( lit kê ph ng pháp trong t photo : có4 ph ng pháp)

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4.  ng dng Cm bin òi hi nh y cao và di

làm vic rng do s thay i in tr 

sut l n trong quá trình t t tr ng( hiu ng CMR)

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4.  ng dng ( so sánh x lý

khí thi gia xt kim loi quývà peroskite- honda)Conventional precious metal

catalyst reaction

1.The constituent elements of the exhaust gas connect with

the precious metals

2.The activated components of 

the exhaust gas on the

precious metal meets other elements and reacts.

3.It becomes CO2, H2O and N2

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Perovskite catalystreaction

1.NO bonds in the holesin the lattice

2.Since the O in the NO

bonds with the catalyst,the bond with the Nbecomes weaker and theN becomes detached.

3.CO and HC react withthe unstable O moleculeand are oxidized4.The Omolecule becomesdetached and turns intoCO2 and H2O

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4. ng dng

While most metal halides and perovskites areinsulating, perovskite sheets can besemiconducting, depending on the B type cation.The bands are determined by the B type cation(and its relative oxidation state) and can then betuned by variations in the A type organic cation.

Organic cation effects can adjust the band up to2 eV in magnitude. [12] A thin-film transistor hasbeen made using (C6H5C2H4NH3)2SnI4perovskite [13]. Communication between themetals through the halide bonds creates arelatively high carrier mobility with Hall mobilities

of 50cm2/V*s). [13] These mobilities arecomparable to amorphous silicon. Perovskitesheets show potential for cheaper and more easilyprocessed semiconductors.

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4. ng dng So the Charge and spin ordering makes

YBaMn2O5 a ferrimagnetic material. Perovskite materials are used as catalyst

electrodes in certain types of fuel cells. The structure is very versatile having

many useful technological applications suchas ferroelectrics, catalysts, sensors,thermopower and superconductors.

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4. ng dng The capacity of these devices can be

greatly increased through the inclusion of

a solid dielectric material. Due to the factthat some ceramics are readilytransformed into extremely effectivedielectrics, it is estimated than more than

90 percent of all capacitors producedcontain ceramics, such as perovskites.

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4. ng dng This significant advance made

superconductors cheaper to cool to theircritical temperature, since liquid nitrogen

is considerably less costly than liquidhelium. The first superconducting perovskite was

discovered by IBM researchers Bednorzand Mueller, who were examining the

electrical properties of a family ofmaterials in the Ba-La-Cu-O system.

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Though research continues to be fast and furious inthe field, and while investigators are stillsynthesizing new ceramic perovskites, they are alsodirecting their attention to practical applications

for the ceramics that already exist. Indeed, inaddition to capacitors, some perovskites have begunto find wide use in piezoelectric devices, whichgenerate electricity when they are subjected tomechanical pressure and, conversely, undergo achange in dimension when exposed to an appliedvoltage. Piezoelectric perovskites obtain their

distinctive properties through processes that causetheir typically cubic structures to shift so thatthey lack a true center of symmetry, as discussedabove in regard to barium titanate. The ceramicssynthesized to be piezoelectric may be used in awide variety of products, including communicationsequipment, crystal-controlled timing devices,

transducers, pressure gauges, buzzers, andaccelerometers. Interestingly, perovskites havealso been found to show significant potential foruse as materials that may safely encapsulateradioactive waste and are being heavily investigatedby scientists in the environmental discipline forsuch purposes.