TAP CHI HOA HOC T. 49(4) 397-400 THANG 8 NAM 2011
NGHIEN CLfU DI^U CHE MANG M 6 N G Ni(0H)2 B A N G PHU'aNG PHAP DIEN HOA VA MOT S6 Y^U T 6 A N H HU'6'NG D ^ N C A U TRUC VA
TINH C H A T DIEN H O A C U A CHUNG
Nguyen Xuan Viet, Trinh Xuan Sen, Nguyen Thj Cam Ha Khoa Hda hgc, Tru&ng Dgi hgc KHTNH, Dgi hgc QGHN
Den Toa soan 22-5-2008
Abstract
The aim of this work was to study the influence of the concentration Ni(N03)2 precursor, current density and deposited time on the structure and the electrochemical properties corresponding with nickel hydroxide thin films preparing by the electrochemically deposited method. The results indicated that these films were the a-Ni(0H)2 form and the film was electrodeposited at 3 mA/cm^ 300 seconds in 0.001 M NiCN03)2 solution shows the best electrochemical properties.
Keywords: Nickel hydroxides, thin film, electrodeposition.
1. GIOI THIEU
Tinh chat dien hoa cua niken hydroxit a dang mang mong da dugc nghien cuu rgng rai [1, 5, 7], do CO nhiJng urng dung quan trgng nhu: che tao vat lieu hap thu quang trong thiet bj dien sac, che tao dien cue xuc tac cho cac qua trinh tong hgp dien hoa.
Trong ITnh vuc nay mang niken hidroxit co kich thuac hat nano cho thay co nhirng tinh nang vugt trgi so vai niken kim loai va niken hydroxit dang hot nha kich thuac tinh the nho, dien tich be mat lan.
Do do viec nghien cihi che tao va khao sat tinh chat ciia mang mong Ni(OH)2 tra thanh mgt van de thu hut sir quan tam lan cua cac nha khoa hgc [4].
Mang niken hydroxit dugc dieu che theo mgt so phuang phap nhu: ket tiia boa hgc, sol-gel, dien ket tua... trong do dien ket tiia la phuang phap che tao mang mong niken hydroxit dan gian, re tien nhung cho hieu qua cao. Mang niken hydroxit thu dugc the hien nhiing tfnh chat dien boa han ban so vai mang mong diSu chS bang phuang phap sol-gel cung nhu nhCrng phuang phap khac [2, 6].
De gop phin vao ITnh vuc nghien cuu nay, chung toi giai thieu mgt s6 k^t qua nghien cuu che tao mang mong niken hidroxit bSng phuang phap ket tiia dien boa va sa bg danh gia chat lugng cua san phSm thu dugc.
2. THl/C NGHIEM VA KET QUA 2.1. Thurc nghiem
+ Mang mong Ni(0H)2: Dugc dieu che bang phuang phap kgt tua dien boa tir dung djch Ni(N03)2
tren nen Ni kim loai tai catot. Mang niken hidroxit sau dien phan dugc rira sach bang nuac cat va de kho a nhiet do phong. Anh huang cua cac dieu kien dien phan tai kha nang tao mang, cau true va tfnh chat dien hoa cua Ni(0H)2 nhu: nong do Ni(N03)2, mat do dong dien va thai gian dien phan se dugc khao sat tirng yeu to cac yeu to khac giir co djnh.
+ Gian do nhieu xa tia X dugc do tren thiet bj D8 Advance Brucker ciia Due, su dung hue xa ke Cu Ka {X = 1,542 A). T6c do quet 0,5° (29) tren phut, goc quet tir 5° din 70° (20).
+ Anh SEM cua mau dugc chup tren thiet bj SEM-JEOL-JSM 5410LV (Nhit Ban). Ch6 do chup:
OPa, lOkV, khoang each lam viec 8 -^ 19 mm, do phong dai toi da x 200.000 lan.
+ Cac duang phan cue vong dugc do tren thiet bj PGS-HH8 do Phong Ung dung may tfnh Vien Hoa hgc, Vien Khoa hgc va Cong nghe Viet Nam ch8 tao. He do di|n hoa gom dien cue so sanh clorua bac va dien cue doi Pt. Toe do quet the 50 mV/s trong moi truang KOH 1 M.
2.2. Ket qua va thao luan
2.2.7. Cdu true cua mdng niken hydroxit tdng hgp bdng phucmg phdp di?n ket tua
San phSm Ni(0H)2 dugc tao thanh tir dung djch Ni(N03)2 tai khu vuc catot theo phan urng sau [1, 2, 4,6]:
NO3" + 7 H2O + Se Ni^^ + 2 OH- -
NHt^+lOOH- (1) Ni(0H)2^ (2) 397
TCHH, T. 49(4), 2011
Phuang trinh (1) la phan ung dien hoa, phuang trinh (2) la phan ung boa hgc, vi ngay sat be m^t catot khoang the tich dii nho va tich so tan cua Ni(0H)2 bang T = 5,47x10"'* nen lugng Jon OH"
sinh ra se lam tang pH de phan irng (2) dien ra kha nhanh.
Ket qua phan tich gian do nhilu x? tia X cho
Nguyen Thf Cam tia va cgng sir thay tat ca cac mang niken hydroxit thu dugc deu co cau true ciia d^ng a-Ni(0H)2, dugc t\\h hien a cac pic d?c trung t^i 10°, 34° va 60° Theo [I, 2, 5] dang a-Ni(0H)2 dugc hinh thanh trong moi truemg co pH thap (trong khoing tir 6,4 den 9) ngay a sat be mat di?n eye do phin urng (1) t^o ra. Trong dung djch gia trj pH vin gitj- khong doi.
M uNI(OH)a
\ 4 : a-Ni(0H)2
^ V _ j L . J Aw 1
yj
•
ll
I /
K
Ket mat cua
^in nut
a) b) Hinh 1: a - Gian do nhilu xa tia X cua mang Ni(0H)2
b - Anh SEM cua mang Ni(0H)2 v6i dg phong dai den 1 ^m
qua chup anh SEM tren hinh lb cho thay be hydroxit khong cao, c6 the la do sue cang bl mat cua mang niken hydroxit kha dong deu nhung bj mang lan. Anh SEM cung cho thay kich thuoc hat nh? chumg to dg dan hoi cua mang niken niken hydroxit nim trong khoang tir 100 nm-5-400 nm.
..
~
5 ;
• •
I::::--.
UauNlfOH):
• :a-Ni(0H)2 A; p-Ni(0H)2
\ l • A
- . : - . ; . • ; , • . • . • • , - . • . • . .
^-"11 1
] TliaU • ( • ! •
I
1 •
v,-.,.V|Yv_
Hinh 2: Gian do nhieu xa tia X cua mang Ni(0H)2 sau khi ngam 7 ngay trong KOH 1 M Mang niken hydroxit dilu che bang phuang
phap difn kit tua co cau true dang a-Ni(0H)2 [3]
kha ben trong moi truang kiem khong qua dam d^c.
Ket qua dugc the hien khi ta quet phan c\rc nhilu vong va ngam dien cue niken hydroxit trong moi truang KOH 1M trong 7 ngay ma cau triic cua d?ing a-Ni(0H)2 gan nhu khong thay doi. Tren gian do nhieu xa cua difn eyre niken hydroxit sau khi ngam van CO nhirng pic dac trung cua dang a-Ni(0H)2, trong khi do nhUng pic dac trung ctia d^ng
P-Ni(0H)2 xuat hien it va khong ro rang.
Chiing toi da khao sat do bin ciia dang a-Ni(0H)2 trong moi truang KOH 1 M bai vi day la moi truang ma dien cue dang mang mong niken hidroxit co nhilu ung dung quan trgng nhu lam xiic tac cho qua trinh oxi hoa nhom -OH ciia cac hgp chat huxi ca thanh
nh6m -CHO trong cong nghf dugc, lam pin mat troi va mgt so ITnh v\rc khac [4, 5].
2.2.2. Tinh chdt di^n hod cua dien cue mdng mdng niken hydroxd trong moi trudmg KOH I M
Tinh chat difn hoa cua mang niken hidroxit, dugc thi hifn tren duong phan cue vong trong moi truong KOH 1 M voi phan ixng difn hoa dugc bilu diln theo phuong trinh 3 [4, 5]:
Ni(0H)2 + OH-1; NiOOH + H2O + e (3)
Vat lifu CO kha nang boat dgng difn boa cang t6t khi mat dg dong pic anot (Ip,a) va mat dg dong catot (Ip,c) cang cao voi hifu the giiia pic anot va pic catot (AE) cang nho.
398
TCHH, T. 49(4), 2011
+ Anh huong Clia nong dg muoi Ni(N03)2
Ket qua o phan tren cho thay nong dg muoi Ni(N03)2 khong anh huong toi cau true cua Ni(0H)2 nhung CO the anh huong tori tinh chat difn hoa cua Ni(0H)2 trong moi truong KOH 1 M. Cac difn eye
mang mong dugc ehe tao trong dilu kifn i = 3 mA/cm^, thoi gian 300 s voi nong dg Ni(N03)2 tir 0,005 M -^ 0,1 M dugc thi hifn tren hinh 3 va bang 1 cho thay.
Difn cue mang mong niken hidroxit eo ho^t tfnh difn boa trong moi truong KOH 1 M khong khic nhau nhieu, chung to nong dg Ni(N03)2 ciing khong anh huong nhieu den kha nang tao mang cua niken hidroxit. Vol difn lugng (It) giong nhau di qua dung djch thi cung chi co mgt lugng xap xi nhau cua ion NO3- bj khir thanh OH" do do co thi noi chieu day cua lop mang niken hidroxit tao dugc trong cac dung djch nay la khong chenh Ifch nhau qua nhieu. Dg day cua mang niken hidroxit la mgt yeu to quan
Nghien cuu dieu che mdng mdng...
trgng tac dgng t6i bo^t tinh difn boa cua no [2, 4].
Trong qua trinh khao sat nay cho ket qua dung djch Ni(N03)2 c6 nong dg 0,01 M cho mang co kha nang ho^t dgng difn hoa tot nhat.
<N S
-10 1 2 3
4
5
o:o(5ivi 0.01 M 0.02 M 0.05 M 0.1 M
2- 1 -
A
• " • ^
5PY' "^
0.05 0.1 015 02 025 03 035 04 046 05
..• 5
U(v)
Hinh 3: Duong phan eye vong ciia cac mang Ni(0H)2 trong moi truong KOH 1 M, toe dg quet
50 mV/s
Bdng 1: Gia trj mat dg dong anot (Ip,a), m^t dg done catot (Ipc), the dinh pic anot (Epa) va the dinh pic catot (Epc) cua cac difn eye niken hidroxit dieu che voi nong dg Ni(N03)2 khae nhau trong KOH 1 M
Ten mau 0,005M
0,01M 0,02M 0,05M 0,1M
Ip,a, mA 13,03 15,97 15,88 14,81 10,92
Ipc, mA -9,39 -12,71 -10,81 -11,22 -8,89
|tp,a'Ap,c|
1,39 1,26 1,47 1,32 1,23
Ep,a, mV 377,2 391,0 423,6 421,8 437,6
Ep.c, mV 203,3 198,4 199,0 191,7 175,2
AE,mV 173,9 192,6 224,6 230,1 262,4
+ Anh huong cua mat do dong difn
Bang 2 bieu dien cac thong so thu dugc tir duong cong phan eye cua difn eye niken hidroxit dugc che tao 6 cac mat do dong dien khac nhau trong dung djch KOH IM ( n6ng do Ni(N03)2 la 0,01 M, thoi gian difn phan la 300 s).
Bdng 2: Gia trj mat do dong anot (Ip_a), m$t dg dong catot (Ip^), the dinh pic anot (Ep^) va thi dinh pic catot (Epc) ciia cac difn eye niken hidroxit dieu che voi m$t dg dong khac nhau trong KOH 1 M Ten mau
l(mA/cm^) 2(mA/cm ) 3(mA/cm^) 4(mA/cm^) 5(mA/cm^)
Ipa, mA 10,1 14,33 15,97 11,16 9,39
Ipc, mA -8,02 -10,83 -12,71 -8,72 -8,13
|Ap,a'tp,c|
1,26 1,32 1,26 1,28 1,15
Ep.a, mV 413,2 405,9 391 404,5
437
Ep,c, mV 195,3 200,2 198,4 194,1 183,1
AE,mV 217,9 205,7 192,6 210,4 253,9
S6 lieu thu dugc cho thSy, tinh chit difn hoa cua din toi dg day cua cac mang thu dugc khac nhau cac difn eye mang mong niken hidroxit thu dijrgc hi nhilu hon. Ket qua trong bang ciing cho thiy voi anh huang dang kl do trong qua trinh tao mang da mat do dong difn 3 mA/cm^ mang niken hidroxit thu CO su khac nhau thyc sy vl lugng ion N03- bj khir, dugc co kha nang boat dgng difn hoa t6t nhat trong
399
TCHH, T. 49(4), 2011 moi truofng KOH 1 M.
-i-Anh huong ciia thofi gian difn phan
Voi dilu kien: nong dg Ni(N03)2 la 0,01 M, m^t do dong la 3 mA/cm^ thoi gian difn phan tir 120 s -^600 s cung anh huong toi dg day cua mang Ni(0H)2 (hinh 4), tuc la anh huong tryc tilp toi boat tinh difn hoa cua mang. Thoi gian difn phan 300s thu dugc mang mong co kha nang hoat dgng difn hoa tot nhat.
Nguyen Thi Cam Hd vd cgng su
3. KET L U A N
10-
<
e 1 0
§
--
1 - 120 s 2-180 s 3 - 240 s 4 - 300 s
I' - JOU s
1 6 - 6 0 0 s . _
^.LAJnjz^
~^
2i ^
T
, i
bi y
0.05 01 015 0 2 0 26 03 0 35 04 0 45 05 0 55 0.6 U(v)
Hinh 4: Duong phan eye vong cua cac mang Ni(0H)2 trong moi truang KOH 1 M, toe dg quet
50 mV/s
Nhirng kit qua thu dugc o nhimg muc tren cho tliay tai dieu kien dien phan vai nong do mu6i Ni(N03)2 0,01 M; mat do dong dien 3 mA/cm^ va thoi gian difn phan 300s cho mang niken hidroxit co tfnh chat difn hoa tot nhat trong moi truong KOH 1 M.
Mang niken hydroxit dilu che bSng phuong phap difn ket tiia tir dung djch Ni(N03)2 co cau true cua d^ng a-Ni(0H)2, kha ben trong moi trudng kilm loang (KOH 1 M), va chuyen rat cham sang dang p-Ni(0H)2. Dilu kifn toi uu dilu che difn eye mane mong niken hydroxit c6 tfnh chat difn hoa tot nhat trong KOH 1 M tir dung djch niken nitrat bSng phuang phdp difn kit tiia dugc xac djnh la Ni(N03)2 0,01M; i = 3 mA/cm^ \k thoi gian difn phan 300 s.
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Lien he: Nguyin CSm Ha
Khoa Hoa hgc, Truong DHKHTN, DHQG Ha Ngi 19 Le Thanh Tong, Hoan Kiem, Ha Ngi
Email: [email protected]
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