TAP CHI HOA HQC T. 50(3) 301-305 THANG 6 NAM 2012
T 6 N G Hgp OIEN HOA NANOCOMPOZIT PANi /TiOj TRONG AXIT HNO3
Le Xuan Que'*, Nguyen Thj Hai Van'^ Thjnh Thi Thu Trang'•^
Mai Thanh Nga''\ Ngo Thj Dung'•^ Nguyen Huy Anh'*, Ddng Dinh Bach^
' Vi^n Ky thugt nhi?l ddi, Vi^n Khoa hgc vd C6ng ngh? Vi^t Nam
^Khoa Hoa hgc, Trudng Dgi hgc Suphgm Hd Ngi
^Dgi hgc Suphgm Thdi nguyen Den Tda sogn 25-7-2011 Abstract
Nanocomposite PANi/TiOj has been synthesized in HNO3 1 N on stainless steel (SS) electrode using cyclic vollammetiy (CV) technique. The presence of nano-TiO^ modified the synthesis CV curves, especially the characteristic redox reaction of formed PANi. Peak potential Ep, peak current Jp and total electric quantity Q were strongly affected. Electrochemical impedance of the nanocomposite PANi/Ti02 film was increased in comparison with intrinsic PANi film, mostly due to an increasing of the charge transfer resistance Ret. Nano-TiOj has been incorporated into PANi chain, and affected some physicochemical properties of the PANi film.
Keywords: Nanocomposite, PANi, TiOj, cyclic voltammelry.
1. GIOI THIEU
Polyanilin (PANi) Id polyme dan dugc nghien cihi vd sir dung rdng rai nhat trong sd cdc polyme dan thuan (intrinsically conducting polymer), bdi do dan didn thuan cao, kha nang pha tgp phong phii, dd che tao, monome anilin re vd de kiem [1-3]. Mgt trong nhirng hudng nghidn ciiu vat lieu mdi, dang dugc quan tam nghien ciru che tgo va iing dung phd bien, la nanocompozit ciia PANi vdi oxit kim logi, dien hinh la oxh titan Ti02 [4, 5].
Loai vat Hdu mdi ndy vira cd tinh dan didn cua PANi, vira cd tinh ban dan cua oxit titan, do dd cd khd nang iing dung cao trong ldp phii bdo vp cd khd ndng dan didn [1], ldm vat lieu nhay quang [6], son chdng an mdn [1, 4, 7, 8], lam vat lieu cho chuydn hda nang lugng [9], senso [10]....
Oxit titan TiOa cd nhidu dac diem uu vidt, dugc sir dung rgng rai trong nhidu Imh vuc cdng nghipp ciing nhu ddi sdng. Dgc biet Id oxit titan cd kich thudc nano cd khd nang dem lgi nhieu tinh chat mdi cho compozit, nhu kha nang quang dien hod, bdo ve chdng an mdn, oxi hod etanol, ldm senso... [6-9].
Viec tdng hgp compozit PANi/Ti02 dugc thuc hidn bang nhieu phuang phdp [10-17], trong dd cd phuong phdp dien hda [17].
Tiep theo mdt sd nghidn ciru chd tao vd xac djnh tinh chdt mang PANi [3, 18-20], nanocompozit PANi va mdt sd oxit kim loai chd tao bang phuang phdp hda hgc [21] va dien hda [22], trong bdi bao nay chimg tdi gidi thjeu Vet nua nnhien ciru che tgo
mang compozit PANi/Ti02 nano bdng phuang phdp dipn hod.
2. PHUONG P H A P T H U C NGHIEM
Dien cue ndn tdng hgp PANi Id thep khdng gi (SS), dien cue so sdnh la cabmen bao hod, dien cue ddi la Pt trong hp ba dien cue truydn thdng. Dung djch tdng hgp la axit HNO3 IN + 3% anilin (ANi).
Trong dung dich tdng hgp compozit PANi/Ti02 cd them T1O2 nano (20-30 nm) vdi ndng dg I g/1.
Thidt bj didn hod Id AUTOLAB PGSTAT 30 (Eco Chemie B.V. Utrecht, the Netherlands) vdi chuang trinh ghi va xir Iy sd lieu ty dgng GPES 4.9 for Windows gdi sdn trong mdy tinh [23]. Phd CV dugc do vdi van tdc 30-50 mV/s, khoang quet thd tir -1,6 V den 1,5 V/SCE. Cdc hda chat deu cd do tinh khidt PA. Cdc thi nghidm deu dugc thyc hidn tgi nhipt dp phong.
3. KET QUA v A T H A O LUAN
3.1. TiOi tac dgng den tinh chat pho CV tong hg-p PANi
Mang PANi khdng cd Ti02 dugc tdng hgp bang phuong phdp didn hod dd lam ca sd doi chieu so sdnh, hinh I. Chi sau 2 chu ky CV (mdt chu ky phan cyc gdm quet the andt tu -1,0 ddn 1,5 V, vd ngugc Igi quet phan cyc catdt tir 1,5 V ddn -1,0 V), trdn dien cue thep khdng gi da xuat hipn mang PANi.
TCHH, T. 50(3), 2012
Sau 20 chu ky, c6 hai pic anot ra r?t, IhS hi^n sir oxi hoa mJng PANi tCr triing thdi khir kh6ng dSn di^n sang tr?ng thdi oxi hoi c6 d? dSn dien cao, l?i viing the E > 1,0 V, vA m^t pic calot khong sjc ndt trong ving the catol (dinh pic khoing -0,1 V tiki -0,2 V) the hi?n sif khir ming PANi, lim cho ming chuydn
Le Xudn Que vd cfngsfr tCi' tl«ng thii d3n di$n ve tr^ng thii khdng din di«n.
Minh diing v i vj tri ciia cic pic oxi hda khu d$c tru'ng ciia PANi trong axit HNO3 c6 bien dOng nhit djnh so v6i trong axit H1SO4 [3], nguyfin nhan c6 thi do tio d^ng cua goc (NOB)', v6i sir hlnh thinh cic nh6m NO, trong vimg di^n th^ anfit.
2.0
E " 10
.rf
^ . 0 0
->
-10
c5 ^ ^
ZZ'^.l ^ j
c20 jy^ J
^^^^"^
-0 5 00 05 10 15
'«»
E, V/SCE Wnh 1: Pho CV polyme hod ANi trong
HNO3, 50 mV/s, - I V den 1,5 V/SCE Hinh 2 gidi thipu pho CV long hgp mdng compozit PANi+Ti02 vdi 20 chu ky phan cyc. Vc co bdn dgng phd CV khdng thay doi, tuy nhidn pic oxi hoa PANi trong vimg the L > 1 V bj suy bien nhanh chdng, tu hai pic thdnh mpt pic. Thdng thudng TiOi nano cd thd hap phy len bd mdt dipn cyc hay bj cuon
)5 00 05 10 15 E, V/SCE ITinh 2: Pho CV polyme hod ANi trong
HNO3+TiOi,50mV/s,-l V den 1,5 V CO hgc vdo mdng PANi mdi hlnh thanh, vd bj Wp PANi dugc tong hgp trong chu ky CV tiep theo che phu. De so sanh pho CV tong hgp PANi va compozit PANi/TiOi dugc gidi thipu timg cdp mpt, theo chu ky c l , c5, cIO, cI5 den c20(hinh 3).
E, V/SCE E, V/SCE //(;?/7i-So sdnh dudng CV ldng hgp PANi \ii PANi/TiO:, so chu ki ghi trongdo thi Nhu vay tren pho CV cd sy khdc bipt rd rpl \c
ddc diem oxy hod mdng PANi, oxit TiOi ldm thay ddi tfnh chat ciia qua trinh oxi hod, chuydn dan tir 2 pic oxi hod thdnh 1 pic. Tinh chat didn hoa the hipn tren phd CV ciia mang compozit da cd nhirng bien ddi khdc han mang PANi thuan.
3.1 I. Dien lugng lodn phan Qa vd Q^
Bidn thien dipn lugng todn phan oxi hod Qa (CV andt tir -1,0 V den 1,5 V) va khir Q, (CV catdt tir 1,5
V den -1,0 V) doi vdi qiia trinh tdng hgp PANi va PANi/Ti02 dugc gidi thieu trong hinh 4. Ban dau hau nhu khdng cd sy khac bidt giua hai trudng hop.
Sau dd dudng nhu TiO: lam tang dien lugng Qi nghTa la tang toe dp phan ung (ca oxi hoa va khif) cao hon trudng hgp khdng cd Ti02.
Hipn tugng ndy budc dau cd thd gidi thich theo nguyen ly ciia ket tiia dien hod compozit kim Ioai + hat oxit. Mang PANi ddy Idn vdi cac hgt TiOi trong mang sd lam tdng dipn tich hoat hod hipu dyng la™
cho tdc dg phdn umg tang len.
302
TCHH, T. 50(3), 2012
u O
Tong hgp di^n hoa nanocompozit...
0 5 10 15 20 0 5 10 15 20 Sdchu kv (n) Sdchu ky (n)
Hinh 4: Bidn thidn dipn lugng andt 0„vd catdt QeCiia CV tdng hgp PANi vd PANi/Ti02, theo so chu ky CV 3.1.2. Di^n the pic cung nhu khir (pc) deu cd dg djch chuydn nhat dinh
Phan tich sdu hon ddn timg qud trinh oxi hod vj tri, miic dg chuyen dich bi tdc dpng rd rpt bdi khii cho thay. cdc pic oxi hoa (pic andt pal vd pfl2) TiO: (hinh 5).
/
„ - / - •
O — . ^ E PANi /
Hinh 5- Bien thien dipn the pic andt 1 (Epal), andt 2 (Epa2) vd catdt (Epc) ciia mdng PANi va mang composit PANi/TiO:, theo sd chu ky CV Tir dd thi cho thdy didn the pic oxi hod pal vd
qua trinh khii catdt bi tac dpng manh nhat, ddc bidt trong giai doan mang PANi da hinh thdnh vd day Idn. Qua trinh oxi hod thii hai pic pa2 hau nhu khdng bi tac ddng.
3.1.3. Ddng dien pic
Tuong ty nhu dien the pic, ddng didn pic cung bi tdc ddng bdi sy cd mat ciia TiO: trong mang PANi (hinh 6). Ddi vdi qua trinh oxi hod andt 1 (Jpal) bidn thidn cua ddng pic chi xdy ra sau khi hinh thdnh
mang PANi va tang ro ret theo sd chu ky. Ddi vdi hai qua trinh oxi hoa andt 2 (Jpa2) vd khir (Jpc), tdc dp phan ling bi tac dgng ngay tir dau, TiO: lam cham khoi mao vd giam tdc dp phdn ung (Jpa2 compozit
< Jpa2 PANi thuan), nhung lam tang dang ke qua trinh nay trong giai doan phat tridn polyme hoa PANi, dac bidt ddi vdi qua trinh khii andt Jp^^.
Hidn tugng bidn dpng Ep, Jp va Qa, Qc toan phan cho thay TiO: dudng nhu khdng chi cd tac ddng co hpc theo nguydn Iy kdt tiia compozit kim loai + hgt oxit, ma cd nhidu tdc ddng hod ly khdc nhau lam bidn ddi tinh chat ciia mang.
£ 2 0
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-J 1 PANHTtOj .^
./y
=1 t^^'
Hinh 6. Bidn thidn ddng dien pic oxi hod andt 1 va 2 (Jpgl va Jpa2) va pic khir catdt (Jpc) ciia PANi va compozit PANi/TiOj, theo sd chu ky CV 3.2. TiO: tac dgng den tinh chat tong trd dien hoa
PANi
Cac hinh 7 gidi thidu phd tdng trd cua mang P A N i l^h"^" "« <-"« " l a n o PANi-i-Tin,
Ve tdng the tdng trd PANi thuan tai didn the -200 mV, 200 mV va 700 mV deu ldn hon tdng trd ciia mang compozit. Tai didn thd phan cue kha cao, 1000 mV, tdng trd ciia compozit gdn nhu triing vdi tdng trd PANi thuan.
TCHH, T. 50(3), 2012
Phan tich t6ng tro cua PANi vi PANi/Ti02_ cho thay, di?n tro cua ming compozit ting 16n m r?l do
tic dOng cua TiO:
khdng doi.
Le Xudn Que vd CQngi0 c6n di^n dung hiiu nhir
y,
a 'i uuu 000
E'lOOOmV
0 1000 PAW
PANCTO, JOOD M
Htnh 7- Phu t6ng trd di$n hod ciia PANi vd compozit PANi/TiOi, theo thu ty tgi dipn th^ phan cyc E -200. 200, 700 vd 1000 mV/SCE
- P A N I -PANI*TlO,
0 40^
200 0 .^xi *Mf)00 iKxm
E.V/SEC
^00 0 200 400 6'X,' ec-j 1000
E,V/SEC
; Bidn thidn cua dipn trd chuydn dipn tich R^, vd dipn dung C theo dipn the phan cyc E, mdu PANi va compozit PANi/TiO:
Dien dung khdng ddi chiing td T1O2 khdng tham gia vd yeu to cdu thanh dipn dung, ngugc lgi cd tdc ddng rd ret den didn trd chuydn dipn tich Re, ldm tang dien tich nay, va do dd lam giam dp dan dipn trong qud trinh chuyen dipn tich ciia mang S^ = 1 /Rci (bang 1).
Bdng 1: Do dan S„ = 1/Rc, (O'cm"^) ciia PANi va PANi/TiO: tai E khac nhau E, mV/SCE
-200 200 700 1000
PANi 2,73x10'' 7,76x10""
2,78x10-*' 13,9x10-"
PANiATiOi 1,30x10-"
4,93x10-"
2,91x10-"
13.1x10"
4. KET LUAN
Tir ket qua nghien cihi bdng phuong phd CV va do tdng trd didn hod cho thay, mdng nanocompozit PAN1/T1O2 cd the dugc tdng hgp bang phuong phdp didn hod trong dung dich axit HNOj cd TiO; nano.
Tinh chat co ban ciia PANi vdn dugc duy tri trdn phd CV va tdng trd dipn hoa. Tuy nhien TiO: nano, sau khi tgo mang compozit vdi PANi da lam thay ddi mdt so tinh chat ciia PANi, nhu lam cham qud trinh oxi hod, lam tang didn thd va giam tdc dd oxi hoa khu ddc tnmg, dac bidt lam giam dg dan dien ciia mang.
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Lien hi: Le Xuan Que Vi^n Ky thuat nhi?t d6i
Vien Khoa hpc va Cong ngh? ViOt Nam 18 Hoang Quoc Vi?t, Cau Giay, Ha Ngi.
Email: [email protected]
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