NGHIEN CLTU CH^ TAO MANG NIKENA/ONFRAM TREN N^N DIEN CU'C THEP BANG PHU'ONG PHAP DIEN K^T TUA
•
Trjnh Xuan Sin, Pham Diic HCing, Nguy?n XuSn Hoin Khoa Hem Iwc. Trucrng Dgi hpc Khoa Iwc Tu nhicn, DHQG Hd Npi
Den Toa soan 30-3-2009
Abstract
Nickel-tungsten films on Ihe sled substrate were prepared by electrodeposition technique using citrate-containing baths at mom temperature. These films were deposited using conditions: {NiSO.. 0,()25M + Na^G.HsOT 0.025M + Na.W04 0 05M}. pH = 7 8, current densities I 5 35 mA/cm^ and the deposition time I - 60 minutes. The moiphology and the composition of nickel-tungsten films were characterizied on the scanning electron microcopy (SEM) attached an energy dispersive spectroscopy (EDS). The pha.se compositions were also identified by X rays diffraction technique. The icsuits shows that the present of tung.sten on the films in some kinds of Ni(W), Ni4W and these films have good electrochemical property in KOH medium.
\.M6DAU
Niken vd cdc hgp chat cua nd dugc quan tam nghiln ciiu nhilu trin the gidi vi cd nhilu irng dung quan trgng: chl tao vat lieu diln cyc cho acqui, vat lieu dien sdc, vat lieu xuc tdc,... [1 - 6]. Trong sd dd, dang hgp chdt niken pha tap vonfram rat dugc quan tdm trong thdi gian gdn day, ddc bilt d daiig hgp kim niken/vonfram thi hiln tinh chat co ly tdt hem nhu kha ndng chdng dn mdn cao, do ciing cao [7, 8].
Tuy nhien, tinh chdt diln hda vd khd nang img dung ciia nd lam xiic tac cho cdc qua trinh oxi hda cdc hgp chdt hiru co van chua dugc quan tam nghien ciiu.
Cdc mdng niken pha tap vonfram chii ylu dugc dieu chl theo phucmg phdp dien phan ddng kit tua vdi sy tham gia ciia mudi xitrat ddng vai trd ligan tao phiic, ngan can sy hinh thdnh hidroxit cua niken vd vonfram trong dung djch ma, ddng thdi md rdng khodng pH Idm vile cua he tir 4 din 10. Trong cdc nghiln ciiu trudc, diln cyc nin thudng dugc lua chgn trin nen cua kim loai ddng (Cu) [8 11] hay vdng (Au) [7, 12]. Gdn ddy nhat, song song vdi nhiing nghiln cim cua chiing tdi, R. Juskenas va cdng sy da cdng bd kit qud ciia nhdm trong viec nghien ciiu chl tao mdng Ni/W dang hgp kim bang phucmg phdp dien kit tua sir dyng thlp ldm diln cyc nen [13]. Cdc dung dich chat diln ly dugc sir dung trong bl ma d ndng do ldn (tir 0,1 mol/1 den 0,5 mol/1), ty 11 ion trong dung djch [W04]^"/Ni-' = 1/1 hoac 2/1, nhilt do be ma xap xi 60°C va mat do ddng diln phan tdi da 50 mA/cm^ Be mat mang niken/vonfram thu dugc vdi hinh thdi hgc thudng khdng ddng deu hoac xuat hien nhieu dudng nirt gay vdi do rgng vlt niit khodng 100 nm den 500 nm [7, 8, 11]. Chiing tdi thuc hien nghiln ciiu nay vdi muc
dich dilu che mang niken/vonfram bang phuang phdp diln phan dung djch INiSOa, Na2W04, Na,ChH<;07} d ndng do thdp ciia cdc cau tir (nhd hon 0,1 mol/1), d pH khdng ddi va nhiet do thdp (T - 30°C), sir dyng diln cyc nin b4ng thep. Khdo sat anh hudng ciia cudng do ddng diln phdn din tinh chat Idp mdng thu dugc \a tiln hdnh ddnh gid tinh chat diln hda cua cac mang niken/vonfram trong mdi trudng kilm (KOH) djnh hudng cho ling dung.
2. THUC NGHIEM
Dung djch cac chat trong be dien phan de che tao mang niken/vonfram trin nen dien cyc thlp dugc sir dung tir cdc hod chat tinh khilt: NiS04.7H20, Na2W04.2H20, Na3C(,H507.2H20 (ky hieu la NajCit) \a KOH. Dung dich NaOH dugc diing dl dilu chinh pH ciia dung djch trong khoang pH = 7 8, nhu da chi ra trong nghien cim cua O. Younes- Metzler [12]. Diln cyc thlp dugc mai bdng bang gidy giap, tay nia sach vd boat hda be mat bang dung djch HCl 1 % trudc khi tien hanh thi nghiem.
Be dien phan cd the tich 100 ml gdm hai dien cyc andt niken hda tan mac ndi tilp, dien cue catot thep dugc dat song song vdi dien cyc andt mgt khoang cdch 1cm dugc nhiing frong dung djch chat dien ly. Cac dien cue cd dien tich 1 cm^ Thi nghiem diln phan che tao mang niken/vonfram dugc tien hdnh trong dieu kiln: cudng do ddng I = 5 -^ 35 mA/cm^ nhilt do T = 30°C, thdi gian t = 60 phiit.
Cdc phuomg phap nghiln ciiu: Xac djnh pha bang nhilu xa tia X (XRD) frin thilt bj nhilu xa D8 Advance Bruker (AcuKa = 1,5418 A, 20 steps = 0,03°/step). Thanh phdn va hinh thai hgc b i mat mdng niken/vonfram dugc khdo sat trin thilt bi hiin
TCHH, T.49 (1), 2011 Trinh Xudn Sen vd cdng su vi dien tu quit SEM JMS-5410LV (Jeol) kit hgp
phan tich thdnh phdn hod hgc bdng EDS ISIS300 (Oxford). Tinh chdt diln hda ddnh gid trin thiit bj Potensio-Galvanostat PGS-HH8; sir dyng dien cyc so sdnh bac clorua, dien cyc ddi Pt vd diln cyc ldm viec la dien cyc dang mang cua niken/vonfram trin nen diln cyc thlp nhiing frong dung djch KOH.
3. KET QUA v A T H A O LUAN
3.L Che tao mang niken/vonfram tren nen di^n cue thep
Ldp mdng niken/vonfram thu dugc trong cdc nghien ciiu trudc ddy thudng xuat hien cdc dudng mit gay hoac bl mdt khdng ddng diu, gd ghi [7, 8, 11]; cd thi gidi thich do mdt trong sd cdc nguyen nhan chinh sau: (/) sy kem tuomg thich giiia ldp mdng niken/vonfram vdi dien cyc nin Au hodc Cu;
(//•) ndng do cdc cdu tir trong dung dich diln phdn ldn; (///) nhilt do bl diln phdn cao thudng xap xi 60*'C hoac mat do ddng diln phdn ldn, Idm tdng tdc dp khulch tdn cdc ion frong dung djch keo theo sy tang tdc diln kit bia kim loai trin nin diln cyc. Khi sir dung nin Id diln cyc thlp, bl mat mang sau diln phdn khdng thay cdc vlt ran, nhung xuat hiln cdc biln hat rd net dugc chi rd frong nghiln ciiu cua R.
Juskenas [13]. Nham khac phuc nhung van dl frIn, mgt loat cac mau thi nghiem khdc nhau da dugc chiing tdi tiln hanh nghiln ciiu do phdn cyc catdt diln cue thlp frong dung djch cac chat diln ly, sir dung cdc edu tir frong dung djch d ndng do thdp tir 0,01 den 0,1 mol/1 (M), dl ddnh gid khd nang phdng
diln cua cdc ion Ni^* vd [W04]^" vdi muc dich tim ra khodng ndng do tdi uu ciia cdc cdu tii trudc khi tiin hdnh diln phdn d nhiet do 30°C.
Kit qua do phdn cyc ddi vdi dung dich Na2W04 khdng thdy xudt hiln viing ion [W04]^" bi dien phdn vd chi cd sy thodt khi hidro tren bi mat diln cyc thep. Nhu vay trong dung djch nudc, ion [W04]^' khdng cd khd ndng phdng diln mdt cdch dgc lap nhu ion Ni^"^ (viing gid trj thi frr -0,6 V din -1,0 V chi cd sy phdng di|n ciia Ni^^ hinh thdnh Ni va viing gia tri thi tir -1,0 V trd vl sau iing vdi sy hinh thdnh ddng thdi cd Ni vd H2); ddng nghia vdi kit qud Id khdng dl dang thu dugc kim loai vonfram hoac cdc dang oxit, hidroxit ciia nd ddc lap thdng qua con dudng di?n kit tiia. Sy phdng diln ciia ion [W04]^' chi xdy ra ddng thdi ciing vdi sy phong diln cua ion Ni^^
trong dung djch do sy tao thdnh hgp chdt phiic kip giura Ni^^ vd [W04]^" vdi xitrat nhu da chimg minh trong cac nghiln ciiu trudc [7, 12] vd dugc khdng dinh trin hinh la (cdc dudng al den a4). Tien hdnh cdc thi nghiem khdo sdt do phan cyc catdt cua diln cyc thlp theo sy biln thiln ndng do cua cdc cdu tir, chiing tdi nhdn thdy khd nang phdng diln ciia ion Ni^"^ vd [W04]^" tdt nhdt trong dung djch xitrat khi ndng do cdc cdu tir trong dung djch diln phan Id : NiS04 0,025 M, Na2W04 0,05 M va Na3Cit 0,025 M. Sli dung dung dich dien phdn cd ndng do cdc cdu tir nlu trin, chiing tdi da thyc hiln cdc thi nghiem dien phdn de nghiln ciiu va khao sdt anh hudng cua cudng do ddng dien phdn den tinh chat mdng niken/vonfram. Gid tri mat ddng diln phan (I) dugc thay ddi tir 5 -^ 35 mA/cm^
(a) 5
^ - 5
h
E—
-25
-35'
1 ' I f * ! ' - J
: 03):
(al) / :
(a2) i / ;
;
A '•
( a 4 ) :
* ' J
\ y ;'"'
', *. \
; . . ^
; 1
'j> ; : ; : ! : ;
/ i ; : : ; ; : :
' i i 1 1 i i 1 1 i 1 1 . i 1 • 1 1 1 1 i : i i l l i l l —
-1.6 -1.4 -1.2 -1.0 -0.8 U(V)
-0.6 -0.4 -0.2 20 25 30 35 40 45 50 55
26(do)
60 65
Hinh 1: Dudng cong phdn cyc catdt cua dien cyc thep frong cdc dung djch chat diln ly (a) va gidn dd nhilu xa tia X cdc mlu mdng niken/vonfram sau dien phan (b)
Dudng (al): Dung djch NiS04 0,025M. Dudng (a2): Dung dich {NiS04 0,025M + NajCit 0,025M}.
Dudng (a3): Dung dich Na2W04 0,05M. Dudng (a4): Dung djch {NiS04 0,025M + NajCit 0,025M + Na2W04 0,05M}.
Dudng (bl,b2): Gian di XRD chuan cua Ni(W) va Ni4W tuong ung.
Dudng (b3,b4,b5): Gian di XRD cac mlu mang niken/vonfram thuc nghiem.
Hinh lb la cdc gian dd nhiiu xa tia X mdt sd mdu mdng niken pha tap vonfram thu dugc sau khi
diln phan frong 1 gid, nhiet do 30°C (dudng b3,b4,b5). So sanh cac pha vdi co sd dur heu chuan 41
ICSD (dudng bl,b2) [14] va cdc nghien cim [6, 8, 9, 13], cho thay cdc mdu dien phan thu dugc chu yeu pha d dang kim loai cua Ni hodc hgp kim Ni(W). CJ day, rat khd khdng djnh chac chdn do sy sai lech khdng nhiiu ve hang sd mang a frong cdu tnic ciia Ni (Fm-3m, a = 3,517 A), va hgp kim Ni(W) {Fm-3m, a = 3,501 A);
ling vdi mdt phdng nhieu xa {111}, vj tri pic 29 = 44,8^ Ben canh cdn xudt hi?n cac pic ddc trung cho pha Ni4W {14/m, a = 5,690 A, e - 3,430 A), irng vdi mat phang nhilu xa {121}, {200}, {321}, vi tri pic tuang img 2^ = 44,3". 45,0" va 65,0° Tuy nhien do thi nghiem dugc thyc hiln frong khi quyen khdng khi, mgt phdn niken va vonfram hinh thdnh trong qud trinh di?n phan cd the bj oxi khdng khi oxi hda vd hinh thdnh cdc dang oxit hodc hidroxit kim loai ton tai d frang thdi vd dinh hinh hodc cd dg kit tinh khdng cao [2, 11]; gdp phan gidi thich dg nhiiu ldn cua dudng nin cdc gidn dd nhiiu xa frIn hinh I b. Gid thilt trin dugc khdng djnh hodn todn thdng qua phdn tich EDS frIn cdc mdng
niken/vonfram thu dugc (hinh 2c,d) vdi su xuit hien cua pic ddc trung cho nguyin to oxi ben canh cdc pic vdi cudng dd ldn ddc tnmg cho Ni va cac pic d|c trung cho W trong mlu. Hdm lugng W cd frong mlu so vdi Ni khdng vugt qud 20% vi phdn fram khdi lugng nguyen tir [8,11].
Anh chup kinh hiin vi dien tir quit SEM (hinh 2a,b) cho biet hinh thdi be mSt mang niken/vonfram cua cdc mau thu dugc sau dien phan. Trin bi mat cdc mau khdng thdy cd sy xuat hiln cdc dudng mit gSy, bi mdt tuong doi phSng mjn chirng td cdc hat bdm trin be mat di?n cyc thep cd do ddc chac cao.
Cac rSnh nhd song song nhin thdy tren bi mat mang niken/vonfram hinh thanh do qua trinh mai bdng di?n cyc thlp tao nin hinh dnh tucmg phan cdu tnic bi mdt Idp ma sau dien phan. Kit qua thu dugc gan tucmg ty cho cac mdu diln phan d cdc gia trj mat do ddng cdn lai.
•f^):V
i. •• I - (b), ^' / • • • ' " : < >
; I'- ^
cps
z::3
100-;
8 0 - 60-;
4 0 ^ 2 0 -
0 - S
1 'i
i
Jl
Ni
Fe
jL^.^...____jy
NI
l ^ i
(c)
Energy (keV) 15
f • ^ -
cps
Energy (keV)
Hinh 2: Anh chyp SEM/EDS mdng niken/vonfram thu dugc sau diln phan d gid tri mat do ddng dien I ••
mA/cm^ (a,c) vd 1 = 25 mA/cm^ (b,d)
15
3.2. Khao sdt tinh chat dif n hda trong moi truong KOH
Mgt loat cdc mdu mdng niken va niken/vonfram dugc chiing tdi dilu chi bdng phuang phdp dien kit tua tren riin dien cyc thlp hr dung djch dien phan cd thanh phdn cac cdu tir tuomg ung: {NiS04 0,025 M + NasCit 0,025 M} vd {NiS04 0,025 M + Na3Cit 0,025 M + Na2W04 0,05 M}, trong diiu kiln nhilt do T = 30°C, thdi gian t = 60 phiit, mat do ddng diln phan I
= 5 ^ 35 mA/cm^ Cdc mlu sau khi dien phan dugc ddnh gid tinh chat dien hda qua viec do phan cyc
vdng trong mdi trudng KOH IM vdi toe do quit thi 50 mV/s. Kit qua tdm tat frong bang 1 va hinh 3.
Cd the nhan thiy, ddi vdi mang niken tmh khiit, dudng phan cyc vdng do frong mdi trudng KOH IM thu dugc vdi cac dmh pic andt va catdt rd net tuong ling vdi sy chuyin hda thuan nghjch Ni^"^ thdnh Ni^* va ngugc lai [2,4]. Gid trj cudng do ddng pic andt (Ip,a) vd catdt (Ipc) cua mang niken thu dugc iing vdi mlu dien phan dudi diiu kiln mat do ddng I = 15 mA/cm^ va 25 mA/cm^ (hinh 3a,b) hodn toan ddng nhdt vdi nghien ciiu cua J-W Kim cimg cgng sy [1].
TCHH, T.49 (1), 2011 Trinh Xudn Sen vd cdng su
25 20
^ 1 5 E 10 o
^ 5 E : r 0
-5 -10
\ \ ! ! : 1 \ : '. i
; ;
1 1
;
\
^"•
'•\i/^
• ^ ^ ^ / ^ ^
; ( b ) j ) > ^ ^
:(a)J^%
^^^if^lSSSS^^^^^
*'k^^5''
A<^) l f \ if'
• M Q P V T
, 1
1
\ I 1
»
1 \ !
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
U(V)
Hinh 3: Dudng phdn cyc vdng do trong dung djch KOH IM ciia cdc diln cyc mdng niken vd niken/vonfram thu dugc sau diln phdn
Ky hiiu: Mang niken/vonfram thu dugc khi diln phdn tai:
Mdng niken thu dugc khi diln phan tai : I = 15 1 = 5 mA/cm^ (c); 1=15 mA/cm^ (d)\ I = 20 mA/cm^
mA/cm^ (a); vd I = 25 mA/cm" (6). (e); I = 25 mA/cm^ (/); va I = 35 mA/cm^ (g).
Bdng 1: Gia tri cudng do ddng tai cdc dinh pic anot vd catot.
Ky hieu mau, hinh 3 Ip,a, mA/cm^
Ip,c, mA/cm^
Mdng niken (a)
5,40 -4,12
(b) 6,31 -5,43
Mdng niken/vonfram (c)
9,68 -6,56
(d) 17,78 -13,99
(e) 18,35 -14,59
0)
18,95 -14,94
(g) 12,88 -9,87 Tuy nhiln khi cd mat vonfram, mdng
niken/vonfram cho gid tri cudng do ddng tai dinh pic anot vd catdt cao gap khoang 3 ldn gid tri cudng do ddng pic andt vd catdt cua mang niken tuomg iing dugc dilu chl frong cimg dilu kiln diln phdn. Vi du mau khi diln phdn d mat do ddng 1 = 1 5 mA/cm^ thi kit qua do phdn cyc vdng trong mdi trudng KOH
IM cho cudng do ddng pic andt vd catdt ciia mdng niken ldn lugt bang: Ip,a= 5,40 mA/cm^, Ip,c = -4,12 mA/cm^ (hinh 3a); ddi vdi mdng niken/vonfram: Ip,a
= 17,78 mA/cm^ Ip,c = -13,99 mA/cm^ (hinh 3dj.
Khdo sdt dnh hudng cua mat do ddng diln phdn ddi vdi cdc mdng niken/vonfram cho thdy mdng niken/vonfram cd do hoat ddng diln hda tdt nhat khi diln phan kit tua mang dudi dilu kiln cudng do ddng diln phdn I = 20±5 mA/cm^ (hinli 3d,e,f). Khi mdng diln phan d mat do ddng nhd hem 15 mA/cm^
hoac ldn hem 35 mA/cm^ thi hoat tinh diln hda gidm di rd ret so vdi cdc mlu dugc diln phdn tai I = 20 ± 5 mA/cm^ (hinh 3c,g). Nhu vdy, sy cd mat cua vonfram trong thdnh phdn mang niken da cdi thien ro ret khd nang hoat ddng dien hda so vdi mdng niken tinh khiit. Co sd ly ludn di gidi thich vai trd cua vonfram cd tdc dung cdi thien rd net hoat tinh dien hda cua mang niken hiln vIn chua dugc ldm sang td, cd thi gid thiit su cd mat vonfram, vdi su sai khdc ldn vi ban kinh ion so vdi niken, lam cdu
tnic mang niken bj thay ddi do tao ra cdc khuylt tat frong cdu tnic mang ludi tinh the cua niken dudi dang Ni(W) hodc Ni4W, nhu da dugc khang djnh trin cdc gidn do nhilu xa tia X.
4. KET LUAN
Bang vile khdo sdt va do cdc dudng cong phdn cyc catdt cua diln cyc thep frong dung djch cdc chdt diln ly vdi sy thay ddi ndng do cdc chdt NiS04, Na3Cit vd Na2W04, chiing tdi da turn ra dugc ndng do tdi uu cua cdc cdu tur: {NiS04 0,025M + NajCit 0,025M + Na2W04 0,05M} dk chi tao cdc ldp mdng niken/vonfram frIn nin diln cyc thep bang phuang phdp diln kit tiia. C) ndng do loang eiia cdc cdu hi, dilu kiln diln phdn tdi uu Id: pH = 7 - 8, thdi gian 60 phut, mat do ddng I = 20±5 mA/cm^ Mdng niken/vonfram thu dugc cd bl mat tuong ddi mjn, khdng xudt hien cdc dudng mit, gay frIn bl mat vd cd boat tinh diln hda cao gap 3 ldn so vdi mdng niken tmh khilt khi do phan cyc frong mdi trudng kiim KOH 1 M. Kit qua phdn tich nhiiu xa Ranghen vd EDS mdng niken/vonfram cho thdy sy cd mat cua cac pha dang hgp kim cua niken vd vonfram nhu: Ni(W), Ni4W va cdc oxit- hidroxit ciia niken/vonfram d frang thdi khdng kit tinh. Cac kit qud nghiln ciiu thu dugc gdp phan md ra mgt hudng nghien ciiu img dung cho mdng 43
niken/vonfram trong ITnh vyc xuc tdc di?n hda oxi hda cdc hgp chat hiru co.
TAI LIEU THAM KHAO I.
5.
6.
J-W. Kim, S-M. Park. J. Korean Electrochemical Society 8 (3), 117- 124(2005).
Nguyen Thj Cam Ha. Luan an Tic-n sT H6a hgc, Trudng Dai hpc Khoa hpc Ty nhicn, DHQG I hi Npi (2007).
K.S. Kumar ct al. Surface and Coatings Technology 202,19. 1764- 1770(2008).
I. Danaee cl al. Intemational Journal of Hydrogen Energy 33,116, 4367 - 4376 (2008).
J-J. Huang, W-S. Hwang, Y-C. Wcng. Thin Solid Films516, 116, 5210-5216(2008),
M. Surender, R. Balasubramaniam. Surface & Coatings technology 187,93 - 97 (2003).
I. N. Eliaz, T.M. Sridhar, E. Gileadi. Electrochimica Acta, 50,2893 - 2904 (2005).
8. I. Mizushim, P T. Tang, H. N. Hansen.
Electrochimica Acta 51, 888 - 896 (2005).
9. I. Mizushima, P.T. Tang. Surface & Coatings Technology 202,3341 - 3345 (2008).
10. M. Ma, V. S. Donepudi, G. Sandi, Y. K. Sung.
Electrochemica Acta 49,4411-4416 (2004).
II. II Alimadadi et al. Materials and Design 30, 1356 - 1361 (2009).
12. O. Younes-Metzler, L. Zhu, E. Gileadi.
IJeclrochimica Acta 48, 2551 - 2562 (2003).
13. R. Juskenas, I. Valsiunas, V. Pakstas. Electrochimica Acta 54, 2616-2620 (2009).
14. Gmelin Institute, FIZ Karlsruhe. Ca sd diJ lieu XRD chuan ICSD (2008).
Lien he: Nguyen Xuan Hodn Khoa Hda hgc
Trudng DHKHTN, DHGQ Ha Ndi 19 Ll Thdnh Tdng, Hodn Kiim Hd Ndi Email: nguyenxuanhoan(§gmail.com