TAP CHI HOA HOC T. 49(6) 743-747 THANG 12 NAM 2011
NGHIEN CLTU DONG HOC QUA TRJNH
POLYME HOA DIEN HOA ANILIN TRONG H2SO4 CO MAT FeS04
Dirong Quang Huan' ^ Lc Xuan Qu£'", Hoang Van ^ o a n ^ Ngd Thj Dung^
Nguyen Huy A n h \ Mai Thanh Nga\ Tran Van An''^
' Vien Ky thugt Nhiet ddi. Vien Khoa hpc vd Cdng nghi Vi^t Nam ' Tnrdng Dgi hpc Suphgm Hd Npi 2
' Vien Hod hpc Cdng nghi('p Vi^l Nam
^Trudng Bai hpc Suphgm Hd Ngi 'Dgi hpc Sirphgm Thdi Nguyen
Den Tda so9n 26-7-2011 Abstract
Polyaniline (PANi) films have been electrochemically synthesized on stainless steel 3 I6L in HjSO,, solution using cyclic voltammetry. There are three oxidation regions on the CV curve FeS04 salt, added in the solution, affected strongly the synthesis process. Kinetics of the synthesis was studied basing on variation of the total anodic polarisation charges, redox peaks parameters, and derivation dJ/dE for the entire CV potential ranges, in regard to the FeS04 salt concentration. It was found that the concentration ratio [Fe^"']/[ANi] and number of CV cycles modified strongly kinetics of the polymerization.
I.GIOI THIEU
Polyanilin (PANi) dugc H. Letheby tdng hgp diu tien vio nim 1862 bang phuang phip dien hda.
Den nam 1910, lin diu tien PANi dugc tong hgp bing phuang phip hda hgc. Nhung chi gin day PANi mdi dugc cic nhi khoa hpc quan tam sau khi phit hien ra khi ning din dien cao cua nd. Rat nhieu cdng trinh nghien cuu tdng hgp PANi vi compozit cua PANi vdi cic oxit kim loai nhu TiO:, Fe203, lim ting khi ning irng dung thuc te, dac biet la khi nang chdng in mdn kim loai va xu ly mdi trudng [1-3].
FeS04 dugc sir dung trong nghien ciru che tao ming PANi bien tinh, vi cd nhiJng hieu irng di?n hda nhat dinh ddi vdi tinh chit dien hda ciia ming polyme din dien [4-6]. Qui trinh oxi hoa khu cua cap redox Fe^VFe'* dugc ghi nhin ngay trong qua trinh tong hgp PANi [4, 5, 7].
Co che ciia qua trinh polyme hda dien hda anilin (ANj) dugc quan tam nghien ciru tir nhirng nim 90 cua the ki trudc vi dugc xic dinh la co che cation - gdc [8-12]. Tuy nhien, ddng hgc ciia qui trinh polyme hda dien hda anilin hien chua dugc nghien cuu chi tiet. Bai viSt niy gidi thieu phuang phap xic djnh dpng hgc qui trinh polyme hda dien hoi anilin dua vio phd phan cue tuan hoin da chu ky (cyclic voltammetry - CV) v i inh hudng ciia FeS04 d^n ddng hgc qui trinh niy.
2. THUC NGHIEM
Cic hoi chat dugc sir dung li: monome anilin (Guangzhou Jinhuada Chemical > 99,5%), H2SO4 98% vi FeS04.7H20 d6u cd do tinh khilt PA.
Dien cue lim viec (working electrode - WE) li thep khdng gi dien tich 1 cm^. Dien cue dugc dinh bdng bang giiy nhim vi rira sach bang nudc cat, cdn ky thuat nhim tao be mat dien cue cd do bdng cao vi khi ning bim dinh tdt. Phii vecni tren dien cue, chi de lai dien tich tiep xiic vdi mdi trudng (1 cm^).
Thiet bi dien hoi li miy AUTOLAB PG.STAT 30 (Eco Chemie B V. Utrecht, the Netherlands) vdi chuang trinh ghi vi xu ly sd lieu tu dpng GPES 4.9 for Windows gii sin trong miy tinh.
Phuang phip CV dugc ip dung de nghien cuu tdng hgp ming PANi, dien the phin cue dugc quet trong khoang -0,2 V den 0,8 V vdi tdc dp quet 20 -
100 mV/s. Sd chu ky quet phu thypc vio yeu cau ciia phep do, cd the tir mpt vai den hing tram chu ky.
Chi tiet ve phuang phip thi nghiem da dugc gidi thieu d mgt sd bii dang trudc day [3,4].
PANi dugc tdng hgp bang phuang phip CV trong mdi trudng H2SO4 1 M vdi ndng do ANi khdng ddi 5 ml/100 ml va dung dich FeS04 d cac ndng dp khic nhau (bing 1). Sau khi hda tan ANi vio dung djch axit mdi cho FeS04 vdi ti 1? ndng dp djnh trudc vao he do. Dung dich dugc do trong ngiy, khdng de qui 24 gid.
TCHH, T. 49(6), 2011 Le Xudn Qui vd cdng su Bang 1: T i lp nong cig FcSO.|/ANi t
Mau do 1 Mil 0,00
M l 0,10
•ong dung djch polyme h6a A N i M j
0,20 M j 0,30
M , 0,50
3. KET QUA VA THAO LUAN 3.L Pho CV cua qua (rinli tdng ligp I 'ANi
Phd CV ciia qui trinh tdng hgp PANi ciia cic miu tir Md - Mi dugc gidi ihicu trong hinh 1-5. Vdi sg tham gia ciia FcSOj trong qua trinh tong hgp pic oxi hda PANi djch chuyen din vc phia di^n tich
, 100- E 3 50 E
-50 -100
= : : ^ ^
^ ^ ^ - S
-0.2 0,0 0,2 0.4 0.6 0,8 E, V/SCE
Hmh 1: Phd CV t6ng hop PANi, mill M„
40 20- 0 20
==,0'
-0.2 0.0 0,2 0,4 0.6 0.8 E, V/SCE
Hmh 3: Ph6 CV t6ng hop PANi, mlu M;
80 40 20 0 -20 -40-
cj
B K ^
- ^ c „
— •=»
-0,2 0.0 0.2 0,4 E, V/SCE
Hmh 3: Phd CV tdng hgp PANi, mlu M4
3.2. Dong hoc qua trinh tdng hgp PANi 3.2. J. Cdc thdng so dpng hpc tdng hgp PANi di^n hoa
dtrgng hgn vi pic oxi hda ciia sit cung xuit hi?n phi thupc vao nong dp ciia FeSOj [4, 5, 7]. Tren cic hinh pho CV (hinh 2-5) deu cho thay, khi cd mit FeS04thi d anot deu thay dugc thir tg pic oxi hoi PANi xiyra trudc, roi den pic oxi hoa Fe ' vi cuoi cimg li pic oxi hoi ANi theo chieu ting ciia di?n the phan circ(E);o calot xuat hipn pic khu Fc ', rdi den pic khu PANi theo chieu giam cua di?n the phan cgc (E).
60
" E 40
3
E 20 -> 0
-20 -40
^:o| A -
^ ^ — = »
• ^ i — %
E, V/SCE Hinh 2 Ph6 C V tdng hi^rp P A N i , m l u M,
60
20
n
20 40
1
c,J1 Q ' /
t-^:: /•
^-^^—
1
J cJ
-0,2 0,0 0,2 0,4 0,6 0,8 E. V/SCE Hmh 4. Phd CV tdng hgp PANi, miu M,
Trong dgng hgc dipn hda, toe do phin ung c6 lien quan ch$t che vdi cudng dp ddng dien I diroc xic djnh bing bien ddi dipn lugng trong mot dan vj thdi gian:
dt zFv
Hay: (1)
zF zF dt Trong dd:
dq - bien thien ciia dien lugng; dt - bien thien ciia thdi gian; v - toe dg phan img dien hda; F- hing sd Faraday (96500C); z - sd electron trao doi trong phin urng di^n hda.
Gi&a cudng dp ddng dien 1 (mA), mat dp d6ng dien J (mA/cm ) vi dien tich di§n cue S (cm^) Heii he vdi nhau bing bieu thuc:
744
TCHH, T. 49(6), 2011 Nghien cuu dpng hpc qud trinh...
I = JS (2) PANi dugc xic dinh bing phan mem GPES tren mdi Theo Arhenius, dOng hpc ciia phin dng don dudng cong phan cgc CV. Mdi gia trj Q cd tinh phin tu xay ra tren bS mat phan chia giQa cic chat
= kCexp (3)
dan dien tuin theo phucmg trinh:
RTJ IRTJ
Trong do:
K - hang so toe do phan ung; C - nong dp chSt tham gia phan urng; E dien the.
Xet phan irng sau xay ra tren be m§t dien circ:
J, 1
Ox Re
(4) Goi jc la mat dp dong dien doi vai phan irng catot;ja la mat dp dong dien anot
Doi vai qua trinh dien hoa (4) phuang trinh dong hpc CO d^ing:
fzFE,
J, = zFk,Co,exp RT
= zFk.C„exp - ^ (5) Trong dd:
Cox - ndng do chit oxi hda , CRC - ndng do chat khu; Ec vi Ea la dien the ciia qui trinh khu va qui trinh oxi hoi.
Tir mat dg ddng dien cd th8 tinh dugc ndng dp chat phin img:
J = aC (6) Trong dd:
J - mat dp ddng (mA/cm^), a - he sd ti le, C -ndngdp (mol/l).
Tir (1), (3) vi (5) cd th6 thay ring, tdc dp phan img tuc thdi (v) tai mdi chu ky phin cue ti le vdi bifin thien mat do ddng dien (AJ):
V. = k - ^ (7) AJ,
Ac, Trong dd:
V - tdc dg tuc thdi tai mdi chu ky phan cue;
k - hS sd tdc dp phin irng; J - mat dp ddng phin ung dien hda; c - sd chu ky quet the.
Day li phugng trinh xac djnh tdc dp phin ung Co the giii thich cdng thirc Qp^,,^j= Qp^f.^.,, li theo bien thien mat do ddng pic theo so chu ky phin JQ toan bd lugng PANi b; khir tren catot trong chu ky Cn-i se bj oxi hoi hoin toan d chu ky ke tiSp Cn 32.2. Thiit Igp bieu thuc dong hpc tinh theo lugng
ANi bi oxi hoa
thong ke, li tong ciia dien lugng oxi hda toan bg ming PANi. Tuy nhien, neu lay Q ciia chu ky thti n, trir di Qp cua chu ky thir (n-1) ta dugc dien lugng oxi hda phan PANi dugc hinh thinh d chu ky thir (n- 1). Vi v^y, cung tinh chinh xic dugc lugng ANi bi oxi hda tao thanh PANi bam tren di?n cgc.
So thir tg chu ky ki hi?u li c,. Gpi dien lugng anot toin phan va catot toin phan d chu ky thir i (c,) tuong lirng li Q^j^jVi Qj,,.), dien lugng pic anot (so 1, oxi hda PANi) va pic catot d chu ky c, tuang irng li Q ^^ jvi Q ^^,^, dipn lugng oxi hda ANi d chu ky c, Ii QOX(ANI)(C ) > *^'?" lugng oxi hda PANi mdi sinh do polyme hda ANi (tuong ung vdi Qov(AN,)(c,))cfchukyC,IiQo,(pAN,)(c,)-
X6t tai cic chu ky, ta cd:
Bdi vdi chu ky CQ- Qa (C > ~ ^
Ddi vdi chu ky a: Qa(c,)" %.Wd "*" QOX(ANO(C,)
"*" XOx(PAN0(C|)
^^° Qc(c,)= Qp,(c„) "*" Qox(PAN,)(c,) hon nOa vdi hai chu ky Co va Ci ta cd Qp_ ,^^j=
tir d o ta CO QO,(PANI)(=,)= Qafcil" Qc(.,) (8)
Tuang tu. doi vdi chu ky C2:
Qa<c,)~ Qp,(c,) '*' Qox(ANi)(cj) "*" Vo» (PAN>)(c,) Qc(cj)~ Qp,(c,) •*" Qox(PAN.)(c,)
matl<hac:Qp_,.j,= Qp_,.,,
nen QoxCPANOfe)'Q.fo)" Q=(t,)
( " .
Tong qudt, ddi vai chu ky c„:
Qa(c„)~ Qp,(c.) "*" Qox(ANi)(c„) "*" Qox(PANi)(c„) Q c ( c J ^ Qp,(c„.,) "^ Qox(PANi)(c„) '>° Qp.(=.)=Qp.(=..,)
nentac6;Qo,,pj„,)(,j= Q.(c.)- Q.(c.) ('")
Di6n lupng pic anot Q^^ trong qua trinh oxi hoa
tren anot. Tai anot, 6 chu ky c„, ngoai lupng PANi bj oxi hoa a pic oxi hoa 1 (oxi hoa PANi) thi con co mpt lupng PANi dupe sinh ra tir ANi va bj oxi hoa ngay trong chu ky c„ Vi vay, lam cho Qp,(c.)tang va keo theo Q ,, ,tang,... Ket qua la Qp_ tang theo
TCHH, T. 49(6), 2011
sd chu ky den khi ket thiic giai do^n phit trien m^ch va bude vio giai do?m tit m^ch thi Q,,^ giim dan va dn dmh.
3.3. Kc( qui thuc nghiem
3.3.1. Bien thien dli-n lugng o\i hda - polyme hoa ANi
Tir so lieu dien lugng oxi hda ANi (0O,(AN.)) t^io thinh PANi l^i mdi chu ky phin cgc c, (da chuan hda ve ciing cn [13]), vc dugc do thj bien Ihicn ciia Qo-itANi) phy thupc vao chu ky c,, hinh 6.
Le Xudn Que vd cpngsif Sau khoing 5-10 chu ky CV tons hgp PANi gia trj OoxiANi) di giim m^nh do ting nong dg ion sit, phft hgp vdi ket qui nghien cuu tic dpng ciia FeS04 d^m qui trinh tong hgp dipn hda PANi [4]. Tuy nhien, trong giai dogn dau polyme hda, gii trj QOX(ANI) ciia cic miu cd ti lp nong dp FeS04/ANi khic nhau bien thien ngugc vdi ket qui nhin xet tren diy (hinh 7).
Nhu v^y, Qox(ANi) ting cimg vdi nong dp FeS04, Irong dd m§u M4 cd Qo% (ANI) cao nhat (tir CQ d6n Cj).
Duirng nlur ion Fe^' tic dpng lim ting lugng ANi bj oxi hda. Mit khac. Ion Fc^* cting cd the tham gia vao qui trinh oxi hda Fe^* -> Fe'*. Tuy nhien, vdi qua oxi hda khir i'c^VFc^* li thugn nghjch thi hi^u ung ting Qo, (AND ciia ion sit se bing khdng.
~. t—M, ,— — M . ^ - . I
i ^ ^
0 5 10 15 20 25 30 Chu ky Hmh 6: Bien thien dien lugng oxi hda ANi (QoMAN,)), mC.lO, theo chu ky CV vdi ti le
[Fe-*]/[ANi] = 0,l;0,2;0,3;0,5
Chu ky
Hmh 7: Bien thien dipn lugng oxi hda ANi (QO(ANO)>
mC.lO, theo chu ky CV giai doan khoi mao polyme hda, ti lp [Fe-]/[ANi] = 0,1; 0,2; 0,3; 0,5 3.3 2. Biin thien tdc dp polyme hda dien hoa ANi
Tdc do polyme hda v, tai mdi chu ky CV thir i dugc tinh theo cdng thuc:
" ^ 0 \ ( A N i ) ( c , ) , , , 1 , .^
V, = —-^^^ (mol/chu ky) dc,
Bien thien ciia tdc dp oxi hda ANi (v,) trong giai doan polyme hda theo sd chu ky deu giim dan theo
thdi gian phan cgc va cd dgng gin nhu tuyen tinh trong khoing chu k; c,o den c:o. hinh 8
Trong giai dogn khoi mio polyme hda vdi co che cation - gdc, toe dg v, ting din theo c, vi dat gia tri cue dgi, hinh 9. Dgng hgc phin img polyme hoa ANi phy thupc mpt phin vio ca ch£ ciia qui trinh polyme hoi. Co che polyme hda thdng qua phan ihig oxi hda ANi cd tinh chat ngiu nhien [12], do dd
15 20
Chuky
Hmh 8. Bien thien ciia v, theo chu ky c, giai doan phit trien mach (C|o - C20) va ti le
[Fe^7[ANi] = 0,l;0,2;0,3;0,5
Hmh 9: Bien thien ciia v, theo chu ky c, giai doan khai mio (co - C15) v i ti Ip
[Fe^7[ANi] = 0,l;0,2
TCHH, I. 49(6), 2011
ddng hpc ciJa phin ung nay rit phirc tgp, nhit la giai dogn khoi mao. Nhd thi§t bi cd dp chinh xac cao kigm soit dugc dien thg phan cgc oxi hda ANi, do do ning lugng khoi mao oxi hda dugc cd djnh vdi dp dn djnh lap lai cao. Muc do thong ke phy thupc vio trgng thii be mat cua dien cgc va sg lien ket thinh dien cue bi6n tinh (modified electrodes) c6 kha nang oxi hda ti6p ANi. Tinh ngiu nhien cdn phu thupc vao tuong tic - pha tap cua FeSO^ doi vdi bk mgt dipn cue vi bin than mang PANi. lim cham mgt so qua trinh vi lam biln dgng pic oxi hda [4, 5].
Vipe xuit hien tdc dp oxi hda max, dien hinh d ndng dp FeSO^ANi li 0,1 vi 0,2 (M, vi M2, hinh 9), phii hgp vdi ly thuyet polyme hda theo ca chg gdc tu do, vdi ba giai doan: khoi mio (initiation - birth), phit trien mgch (propagation - growth) va tit mach (temination - death) [12], trong dd bat dau vao giai dogn phit trien mgch thi tdc dg phin liiig tang nhanh; sau dd den giai doan tit mach thi toe dp phin u-ng giam din.
4. KET LUAN
Phuong phip nghien ciru dpng hgc polyme hda ANi sir dung dien lugng oxi hda ANi (Qo^ (ANI)) cho thay ion sat tic dpng trii ngugc nhau len dpng hoc phin img oxi hda ANi d hai giai dogn. Cy the, d giai doan khai mao polyme hda ANi ion sit kich thich lim ting lugng ANi dugc oxi hda do dd lam ting lugng sin phim PANi boat hda. Nhung trong giai dogn phit trien ciia polyme hda ANi, ion sit lim chim qui trinh, do tic ddng pha tgp vi hap phu.
Tuang tic giQa Fe^* v i PANi, ngay c i trong qui trinh polyme hda ANi, xiy ra trong he dien hda phuc tgp vdi nhiSu cap redox (Fe'VFe""^, PANi cd tir 1-3 cap phan limg redox, oxi hda ANi), cd vai trd lim bien ddi ciu true vi tinh chit vit lieu, cin dugc
Nghiin cim dpng hgc qua trinh. . nghien ciru cd he thdng hudng tdi hieu thiu dio ban CO che va ddng hpc ciia qui trinh niy.
TAI LIEU THAM K H A O
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Lien hi: L e X u a n Q u e Vien Ky thugt N h i e t ddi
Vien K h o a h p c va C d n g n g h e Vipt N a m 18 H o a n g Q u d c Viet, C i u G i a y , H a N d i .
