TtJySn t$p H0i nghj Khoa hgc ky ni$m 40 nam Vi$n Han lam KHCNVN - Ha N^i, ngay 07/10/2015
V A T L I £ U DIEN ClTC ANOT CHO BAO VE C A T 6 T C H O N G AN MON KIM LOAI VA CONG N G H i DIEN HOA
N g u y i n Ngoc Phong, D 5 Chi Linh, Ph?m Hong Hanh, Ngo Thi Anh Tuylt, Hoang Thi Binh
^ Vien Khoa hpc vat lieu, Vien Hdn Mm KHCNVN, 18 Hoang Quoc Viet, Cdu Gidy, Hd NQI
Email.- phongnn(a>. ims.vast.ac vn
T6m tat. Trong an mon cung nhu cong nghe dien hoa, v | t lieu anot cd mdt vai trd quan trgng. Phdng thi nghi?m Nghien cim an mon va bao ve vat lieu da nghien cim thanh cong vat lieu andt hy sinh hpp kim nhom va hgp kim kem ciing nhu andt tro MMO Ti/Ru02lr02Ti02 dimg trong cdng nghe bao ve catot bing ddng dien ngoai d l bao v# cac cdng trmh sat thep khoi an mdn do tac ddng ciia mdi trudng. Nhiing vat lieu nay c6 tinh nang ky thuSt tucmg duong nhiing vat lieu ciing loai tren thi gidi va da dupe ap dung rpng rai trong thyc te de bao ve cac cong trinh, ciu kien bing tiiep trong mdi tmong biin va trong dit. Trong cdng nghe xu ly moi midng, vat lieu Ti/Ir02(l%)Sn205Sn02 cd qua tbi oxy cao, phu hop cho oxy hoa cac chit hiru ca dpc hai khd phan buy. Vat li?u C/lrOaRuO;, xiic tac cho qua trinh giai phdng oxy da dugc nghien ciiu, iing diing lam dien cue anot trong thiet bi dien phan nuoc de san xuat hydro, la nguon nhien lieu sach trong tuang lai.
Tie khoa: an mon, phircmg phap bao ve catot, anot hy sinh, dien cue anot tra, MMO, oxy hoa dien hoa, mang trao doi proton.
1. VAT H f U ANOT CHO BAO VE C A T 6 T .
An mdn la mgt hien tugng rat phd bien cua kim loai, lien quan den b i n hit cac nganh kinh te va gay tdn that Idn ve mat kinh te. Ngudi ta da tinh dugc rang gia tien chi phi cbo ITnh vuc an mdn chiem khoang tu 3 - 5 % tdng thu nhap qudc dan ddi vdi nhihig nude cd nen cdng nghiep phat trien [1]. O My an mdn gay thiet bai khoang 300 ti dd la moi nam va khoang mdt phan ba sd dd cd the tiet kiem dugc neu lua chpn nhiing ky thuat bao ve chdng an mdn phii hgp. Cd nhieu phuong phap bao ve nham h^n che qua trinh an mdn xay ra nhu sir dung cac chat lic che hoac xir ly mdi trudng an mdn, cac ldp son phu hiju co hoac vd c o . . . va dac biet la phuong phap bao ve catdt ddi vdi cac cdng triiih trong mdi trudng tu nhien nhu trong dat va nude bien. Viec lira chpn dugc phuong phap bao ve bgp ly hoac ket hgp cac phuong phap vdi nhau nhu son phu vdi bao ve catdt ddi vdi cac cdng trinh trong nude bien la can thiet, rat cd y nghia ve mat kinh te.
l . L An mon kim loai va phirong phap bao ve.
Khi kim loai tiep xiic vdi mdi trudng dien ly nhu mdi trudng dat, mdi trudng nude b i i n . . . , tren be mat kim loai hinh thanh nhiing vimg dien the khac nhau. Nhiing kim lo^i khac nhau cd the dien cue khac nhau, tham chi trong trudng hgp cung mpt kim loai the dien cue ciing thay ddi khi nd tiep xiic vdi nhiing dung dich khac nhau va trong nhirng dieu kien khac nhau ciia dung dich. CJ cimg mdt thdi diem, su thay ddi dien t h i xay ra do su khdng ddng nhat cua thanh phan, cau true va tinh trang be mat ciia kim loai. Vi nhirng ly do nay, tbudng tdn tai nhiing viing dien the khac nhau tren b l mat kim loai, mdt sd chd cd dien the cao, mdt sd cbd cd dien the thap hon va nhu
\ ay hang lo^t vi pin se dupe hinh thanh.
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Tieu ban: Khoa hoc Vat li$u
Qua trinh ion hda kim loai d nhirng viing cd dien the thap (vimg andt) se xay ra vai kim loai hi hda tan (an mdn). Ngugc lai, d viing cd dien the cao (vung catdt) oxy kk hgp vdi nude va nhiing dien tir do kim loai hda tan cimg cap de t^o thanh nhung ion mang dien rich am. Qua trinh an mon dugc bieu diln nhu sau [1,2]:
- Qua hinh andt: Fe -> Fe'" + 2e
- Q\"i:.-::.:, ^2t6t: I/2O2 + H2O + 2e ^ 20H"
-Qua hinh an mdn: Fe + ^ 2 0 , + H2O -> Fe^* + 20H" i Ca hai qua trinh andt va catdt ddng thdi xay ra hen ciing bd mat kim loai, tao thanli ddng an mdn chay hong mach dugc tao nen bdi kim loai va dung dich va dugc goi la cac vi pin (binh la).
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U'li.
/////
Vung catot
Dong bao v ? (bl
VLtng3n6t ^ \
" ^ /////
Vung cat6t
Hinh 1. Nguyen ly dn mon (a) vd bdo ve catot (b).
Can cii vao ca che an mdn dien boa ciing nhu dieu kien boat ddng cua cac pin an mdn cd the dua ra cac bien phap sau day nham muc dich giam tdc dp an mdn kim loai den miic thap nhat:
- Lua chpn vat lieu kim loai thich hgp, - Xii li mdi trudng de bao ve kim loai, - Loai trir cac cau tu gay an mdn,
- Su dung chat lic che bao ve kim loai khdi su an mdn, - Nang cao dp ben chdng an mdn kim loai bang cac ldp son phii, - Bao ve kim loai bang phuang phap dien boa.
Cd the lua chpn mdt trong cac bien phap tren hoac ket hgp cac phuong phap de nang cao hieu qua bao ve. Khi su dung son phu, hieu qua bao ve cd the tir 50 - 99 %, phu vao thdi gian sir dung, loai son va phuong phap thi cdng. Kbi kit bgp son phu vcri he thdng bao ve catdt thi hieu qua bao ve dat dugc va duy tri d 100 %.
1.2. Phuomg phap bao ve catdt.
Nguyen tac cua phuong phap bao ve catdt la ngan can cac diim andt xay ra ben he mat kim loai bang each cung cap du dien tir din cac viing andt dl khdng cho qua trinh hda tan kim loai xay ra. Khi cd mdt ddng dien mpt chilu DC dugc ap vao tir mpt dien cue phu qua dung dich den be mat kim loai, ddng dien se uu tien chay din viing catdt, do dd dien the d vimg nay se dich chuyen vl phia am do phan cue catdt va dat den dien the ciia vimg andt (hinh lb). Khi catdt phan cue din dien thi bing dien thi anot thi nhung pm an mdn se bi loai tru. Qua trinh nay dugc gpi la bao ve catdt [2]. Cd hai dang bao ve catdt:
1. Bao ve catot bang he thong ddng ngoai, 2. Bao ve catdt bang andt hy sinh (protecto).
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Tuyin t$p HH nghj Khoa hoc kf ni$m 40 nSm Vi$n Han lam KHCNVN - Ha NQI, ngiy 07/10/2015
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; Trong he thdng bao ve bing ddng dien ngo^i (hinh 2a), cue am ciia ngudn dien nagt chieu dugc ndi vdi cdng trinh cin bao ve va cue duong ndi vdi dien cue phu dugc nhiing trong dung dich (gang silic, graphit, hgp kim chi, Pt, hdn hgp dxit dan dien...). Nhu viy, ddng dien chay Uj dien c\rc phu qua dung dich din cdng trinh.
Trong he thdng bao ve bing protecto (hinh 2b), kim loai hoac hpp kim protecto cd dien thi am ban thep cin bao vp (protecto Al, Zn,^ Mg) dupe ban tryc tiip hoac ndi day dan dien vao cdng trinh.
Nhung protecto nay dugc gpi la andt hy sinh vi nd hi tan ra va cung cap ddng di?n bao ve cho cdng trmh. Nhirng vat lieu lam protecto thuong la hpp kim Al, Zn hogc Mg.
Hinh 2. Nguyen ly bdo vf catot bdng dong dien ngoai (a) vd bdng anot hy sinh (b).
Ddi tugng ap dung phuong phap bao v | catdt rat da dang va rpng rai, ph\i thupc vao kich thudc, binh dang ciia cdng trinh ciing nhu dilu kien mdi trudng. Viec lira chpn hoac la h? protecto hay h? ddng dien ngoai dua vao dieu kien bl mat va dp Idn cua cdng trinh can bao ve, dp dan dien cua mdi trudng, miic dp an mdn thep va vl mat kmhtl.
Nhung doi tuong thw&ng duac bao ve catot:
* Nhiing cdng trinh dudi nude: Nhirng cdng trinh can cang nhu la nhiing tam cir chan sdng, coc can cang, cira cdng, phao bien, cac ddc, chan de gian khoan, dudng dng dan khi dudi bien.
* Vd tau thuy va cac trang thiet bi ciia tau tiep xuc vdi nude bien nhu he thdng trao ddi nhift, may bom...
* Nhirng can kien dudi dat nhu coc thep, dng dan chuyen tai xang dau, day cac be chiia xang dau...
* Cot thep trong be tdng.
De phuc vu cbo cdng ngh^ bao ve catdt, Phong thi nghiem Nghien cuu an mdn va bao ve vat lipu da nghien ciiu thanh cdng vk dua vao san xuat vat lieu hpp kim cho ca hai dang bao ve catdt, cu the la: (i) vat lieu dien cue andt tra MMO (mixed metal oxide) tren co sd hdn bgp dxit rutheni, uidi va titan dimg cbo bao ve catdt bing ddng di?n ngoai, va (ii) he hgp kim protecto nhdm va be hgp kim kem lam andt hy sinh. Cac vat lieu chi tao da dugc ap dyng cho nhieu co sd de chdng an mon cho cac cdng trinh
\'k thuc tl da chiing td cac he andt tren deu boat ddng tdt, dam bao cac tinh nang ki thuat mong duong vdi cac vat lieu cung loai tren tbi gidi.
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Tiiu ban: Khoa hgc V$t lieu
1.3. V a t lieu andt hy sinh.
Vat lieu andt hy sinh tren co sd hop kim kem va bgp kim nhdm da dugc nghien cihi c h i tao thanh cdng va thuong mai hda tir nam 1995. Cac thdng sd kl thugt dugc thi hien trong bang 1 [3], tuong duang vdi cac vat lieu ciing loai tren the gidi [4]. Hinh anh mdt sd loai protecto da san xuit va triin khai iing dung dupe vi du minh hpa tren hmh 3.
Bdng 1. Tinh ndng ki thuat cda anot hy sinh.
Tinh nang ki thuat
Ti trpng (g/cm') Dien the lam viec (mV/Ag/AgCl) ng lui^ng Ihuc te (A.h/kg)
Hieu suat bao ve (%)
PTN cbiing toi [3]
Anot hy sinh liem he ZnAlCd 7,1 -1030 780 - 800
95
Anot hy sinh nhom he
AlZnln 2,7 -1100 2300 - 2500
85
Tlie Anot hy smh Icem h?
ZnAlCd 7,1 -1020 + -
1035 780 - 800
95 eidi [4]
.Anol liy sitth nhom hf
AlZnli, 2,7 -1100 + -
1120 2300-2600
85
(a) (b) _
Hinh 3. Mot so chiing loai protecto (a) vd dugc gdn vdo vo tau (b).
1.4. Vat lieu anot tror M M O .
Hinh 4. Hinh SEM be mat anot tra MMO (a) vd do ben, 6n dinh theo thai gian (b).
Dien cue andt tro MMO la loai dien cue tien tiin, dupe c b l tao bang phuong phSp phan huy nhiet tren c a sd hdn bgp dxit kim loai quy va dxit tro phu tren nen titan - Ti/RuO:lrO:Ti02
Dien cue MMO Ti/Ru02fr02Ti02 vdi ham lugng RuOi 15% va Ir02 15% cd dp hao mdn rat thap, dp dan dien va hoat hoa cao, b i n trong ca mdi trudng cd dp pH thap [5.6], Dien cue cd be mat mjn, nhin bdng (hinh 4a) va dien the lam viec on dinh theo thdi gian d mat dp ddng tir 500 - 70pA/m^ la mat dp ddng thuong ap dung cho bao ve
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Tuyen t§p Hdi nghj Khoa hoc ky ni$m 40 nam Vi$n Han tSm KHCNVN - Ha NQI, ng^y 07/10/2015
atdt trong nude biin (hmh 4b). Mdt s6 tinh nang ky thuat cua anot tra
•i/RuO;Ir02Ti02 do phdng thi nghiem chiing tdi cbl tao dugc thi hien trong bang 2 a cd so sanh vdi dien cue cung loEii tren tbi gidi [7,8].
Bang 2. Tinh ndng ky thuat cua anot tra MMO.
1 PTN chung toi [7,8]
Kim loai nen Kich thudc anot Ldp phu MMO 'Chieu day ldp phii
Tdc dp bao mon max.
Mat dp ddng sir dung trong dat max.
Mat do ddng su dung trong nude biin max.
Thdi gian sii dpng
Titan Dang dng: O30 x 500 mm Dang dia; O200 x 4 mm
lOg/m^
Khoang 5fxm Khoang O.Olg/A.nam
100 A/m"' 600 A/m^
20 nam
The gidi [9,10]
Titan
6-lOg/m^
Den 5fim 0,OIg/A.nam
Vat li$u andt tro MMO cd the che tao d d?ng tam, thanh hoac dng tuy thudc vao muc dich sir dyng.
Wnh 5. (a) Bien cue anot tra MMO cho bdo ve catot cdc cong trinh bdng thep trong dat vd nuac biin vd (b) Bien cue anot tra MMO vd bg gid da de hdn vdo vo
tau bien.
Hinh 5a la mpt sd dien cue anot tro MMO da dugc sir dung bao ve chdng an mdn tuyin dudng dng dan xang diu trong dit ya trong nude bien tai Viing Tau va hinh 5b la dien eye andt tra va bd gia dd dugc thiet ke phii hgp de bao ve vo t^u bien.
2. V^T Ll£U A N 6 T iTNG DVNG TRONG M O T SO CONG NGHE DIEN HOA 2.1, V|t lifu andt ung dung trong xir ly niro^c thai chua cac chit 6qc hai kho
phan huy.
Ben each cac chit vd ca nhu kim loai nang, axit, kiem va muoi, nude thai cdng nghiep cdn chira cac chit d nhiem hiiu co ma nd can phai dugc xii ly trudc khi dugc thai ra mdi trudng xung quanh. Cd mdt vai phuang phap xir ly nude thai cdng nghiep chua cac hgp chit biiu co nhu thieu buy, hap phu, xir ly bang vi sinh va bang dxy hoa hoa hgc hoac dien boa. Viec lua chpn phuong phap xir ly nao la phu thudc vao kha nang kinh tl cung nhu de thuc bien va hieu qua xir ly. Phuong phap xii ly nude thai bing vi sinh la phuang phap don gian va re nhat. Tuy vay, nhieu chat thai hiiu co khd
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TiSu ban: Khoa hgc V$i li^u
cd the dxy hoa duoc bang vi sinh hoac hieu qua rat thap, ma chiing chi cd t h i dxy hoa b i n g phuong phap hoa hpc hoac phuang phap dien boa. Vi du phenol (C(,H50H) cbloropbenol, TNT, N G . . . la nhihig chat thai rat ddc va khd dxy hoa dupe b§ng vi sinh.
Phuong phap dien boa d l xii ly nude thai dang dugc chii y rit nhiiu do qua trinh il dieu khien va hieu qua dugc nang cao nbd sir dyng cac vat lieu andt cd dien tich be mat Idn va qua the giai phdng dxy cao.
Phan ling giai phdng dxy rat nhay ddi vdi su thay ddi thanh phin va ciu tnic bl mat dien cue va rat quan trpng trong qua trinh dien phan, nd la phan img phu trong qua trinh dxy hoa cac chat huu co va vi vay lam giam bieu suat dong. Tren cac vat lieu khac nhau, qua the giai phong dxy khac nhau, vat lieu nao cd qua the dxy cao se phii hgp cho qua trinh dxy boa cac chat huu co trong xii ly nude thai.
^ 2 0 0 0
O . ^ l O D O
(t» - • • Ir02
— * — (IrSWSna
Hinh 6. (a) Dugng cong phdn cue dong on dinh cda phdn img gidi phong oxy tren cac di^n. i cue khdc nhau trong dung dich IMH,S04 vd (b) Suphu thugc cua COD vdo diin tich tieu «
tren cdc anot khdc nhau V O mat dp ddng 0,1 mA/cm^ dien the giai phdng dxy hen dien cue
Ti/lr02(l%)Sn205Sn02 la khoang 1,7 V[SCE], cao hon so vdi h e n cac dien cue truyjn thdng RuO, (1,20 V) va IrOj (1,25 V) (hinh 6a). 6 nhimg mat do ddng cao hen, do chenh lech cua qua thd giai phdng dxy tren dien cue Ti/lrO2(l%)Sn2O5Sn02 so voi Ti/RuO, hoac Ti/lr02 cang cao. Kdt qua cho thdy COD giam rit nhanh khi Sll dung andt Ti/lr02(l%)-Sn205-Sn02 va COD chi cdn khoang 50 mg 02/dm' sau khi difn phan 40 A h / d m l Trong khi dd ndu sii d\uig andt Ti/Ru02 va Ti/IrOj Ti/Ru02lrO,TiO, COD giam rit cham (hinh 6b).
^ ^ r — ^ - -~ •
Hinh '. (a) Cdc tam andt trg MMO dugc sir dung tat Nha mai ZI2I vd (b) Be diin phan sir dung anot tra MMO trong day chuyen xuh nuac that chua stipnat chi.
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W e n tap H0i nghi Khoa hoc ky ni$m 40 n^m Vi$n Han lam KHCNVN - Ha NQI, ngay 07/10/2015
Hinh 7 la mpt so hinh anh cac tim andt tro Ti/lrO:(l%)Sn205Sn02 dugc ap dung trong day Unyen xii ly nude thai cd chiia stypnat chi tai nha may Z121 thay thi cho cac dien cue andt graphit. Andt MMO nay cd thdi gian sdng va hieu suat dxy hda cao hon nhieu dien cue graphit.
2.2. Vat lifu anot trong di§n phan nud-c san xuat hydro.
The gioi dang bi phu thudc rit nhiiu vao ngudn rjuen lieu bda thach (than da, dau md, khi dot..). Tuy nhien, ngudn nhien lieu nay dang bi khai thac can kiet va khdng the tai t^o. Theo dy doan vdi da tieu thy nhu bien nay thi ngudn nhien lieu nay se bi khai thac het vao nira sau cua thi ky 21. Mat khac sii dung nhien lieu hda thach cung tdn tai nhieu van de Ion nhu gay d nhiem mdi trudng, hieu iing nha kinh...dan den bien ddi khi hau toan cau lam trai ndng len. Vi vay nhu cau tim kiem cac ngudn nang lugng mdi dang fro thanh nhu ciu birc tbilt cua nhan loai.
Trong nhimg nam gan day, khai niem "nen kinh te hydro" da dugc de cap ngay cang nhidu trong khoa hpc ciing nhu trong ddi sdng xa hdi. "Nin kinh tl hydro" la mdt he thdng luu tru, phan phdi va sir dung nang lugng dya tren nhien lieu chinh hydro, khai niem nay dugc General Motor dua ra vao nhiing nam 1970 vdi sang kien chuyen dan nen kinh te dua vao dau md sang nen kinh te dya vao hydro (hydrogen economy) nham giam bdt sy phu thudc vao ngudn diu md bai dn va ngay cang can kiet.
Hydro la nguyen td cd nhieu nhat, cau tao nen 90% vat chat trong vii try va trai dat;
hieu suat chay cua nd cao hon dau md (60% so vdi 25°'o). Kbi dot hydro chi cd mdt san pham phy duy nhat la nude, khdng kem bat cii chat thai nao cd hai cbo mdi trudng nhu khi dot xang dau. Tdm lai hydro la ngudn nang lugng tai sinh sach nhat, hieu suat cao nhat va cd ngudn cung cap vd tan. Bdi vay kinh te hydro se la nen kinh te ben vfoig ly tudng nhat cua loai ngudi. Ve nguyen tac, tat ca cac phucmg tien chuyen chd chay bang xang dau deu cd the chuyen sang chay bang hydro. Khi ay nang lupng hda hoc cua hydro dugc chuyen thanh nang lugng co hpc bang each ddt hydro trong ddng CO ddt trong, hoac cho hydro phan iing vdi dxy trong pm nhien lieu (FC, fuel cell), qua do sinh ra dien, san pham phu ciia qua trinh chi la nude. Dimg hydro de chay xe va phat dien la hai ITnh vuc rat cd trien vpng, nbat la xe chay pin nhien Heu hydro.
Hydro dugc san xuat bang nhieu cdng nghe khac nhau nhu tu cac nhien lieu hda thach (diu md, than da, khi dot...), dien phan tir nude, biomass, quang dien boa va xiic tac... mdi cdng nghe cd nhiing uu va nhugc diem khac nhau.
Hydro san xuat tir cac nhien lieu hda thach cd gia thanh re nhat va cd the san xuat d . quy md Idn nbung lai gay d nhiem mdi trudng. Phuong phap dien phan cho san pham b?ch, khdng gay d nhiem nhimg chi phii hgp vdi quy md nhd va gia thanh cdn cao.
Cdn phuong phap quang dien hda, quang xuc tac thi hieu suat cdn thap va chua dugc ung dyng thuc te.
Phuang phap dien phan nude la gua trinh dimg ddng dien mpt chieu de tach nude thanh khi hydro va dxy. Qua trinh gdm bai phan ung xay ra d hai dien cue, hydro smh ra d dien cue am va dxy d dien cue duong:
'H2O + 237.2 KJ/mol + 48.6 kJ/mol => H2 + 1/2 O2 Dien nang Nhiet narig
Phuang phap dien phan nude cung cap mgt giai phap ben \Trng de san xuat hydro va rit thich hgp de ghep vdi cac ngudn nang lupng nhu gid va nang lugng mat trdi.. . Hien nay cd mdt sd loai be dien phan khac nhau nhu: Dien phan dung dich kiem, dien
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Tieu ban: Khoa hoc Vat li$u
phan nude ap suat cao, dien phan nude d nhiet dp cao sii dyng dung dich oxyt ran \ a dien phan nude su dyng mang trao ddi proton (PEMWE).
B I dien phan vdi mang trao ddi proton (PEMWE) dang dugc quan tam nhieu nhit PEMWE sir dyng mang hihi co (dung dich ran) thay cho dung dich kiem, chit dien phan chinh la mang polmer Nafion dan proton dya tren axit perluorosulfonic. Mang ngan cho phep ion H" dich chuyen tir andt ve phia catdt va tao thanh hydro, ngoai ra mang ngan cdn cd tac dyng phan tach cac san pham khi O2 va H2. So vdi dien phan dung dich kilm tbi dien phan PEMWE [9] cd nbieu uu diem hon nbu: hieu suit cao (ban 90%), do tinb khilt cua san pham cd the dat den 99.999% , an toan ban, tieu thu nang lugng it ban, cd the van hknh trong mat dp ddng cao ban (1-2A/cm'), khoang nhiet dp va ap suit van hanh rpng hem. Tuy nhien, sy phat trien ciia thiet bi PEMWE da bi kim bam bdi chi phi che tao cao cua cac thanh phan nhu la mang trao ddi proton, cac xiic tac kim loai qui.... Vdi he thdng phdng thi nghiem, d mat dp ddng lA/cm^, dien thi 1,57V va nhiet dp 80°C thi tieu thy 3,75kwh de san xuat Im^ hydrd d dilu kien thuong.
Tai Viet Nam, ciing vdi viec nghien ciiu phat trien pin nhien heu, cac nghien cuu xe dieu che hydrd bang phucmg phap dien phan mang trao ddi proton cung dupe quan tam chu y. Nam 2012, Phdng an mdn va bao ve Vat lieu, Vien khoa hpc vat lieu voi nhirng ca sd thiet hi va con ngudi san cd da budc dau nghien ciiu che tao vat lieu xiic tac cho cac qua trinh thoat dxy va hydrd trong bp dien phan PEMWE va dat duoc nhirng ket qua budc dau kha quan.
2.2.1. Nguyen ly lam viec ve dien phSn niroc mang trao doi proton (PEMWE) Hinh 8 md ta qua trinh xay ra trong mdt binh dien phan sir dung mang bao do!
proton, nude dugc cap d andt dugc ndi vdi mot ngudn dien mdt chieu.
Hinh 8. Mo hmh be dien phdn su dung mdng ngdn ii'ao doi proton Khi cd ddng dien chay qua, nude bi tach thanh O2 va H~, proton di qua mang ngan
\a ket hgp \'di nhdm sunfonic (cd trong mang ngan) di chuyen ve catdl, tai day chiing bi khir thanh H2 [9.10].
Andt: H2O ^ l/207 + 2H^+2e- E°(25''C) = 1.299 V Catdt: 4H^ + 4e -^ 2H2 E''(25°C) = 0 Phan img tdng cdng: 2H2O -^ 2H2 -!- O2 E^(25"C) - 1.299 V Cau tao cua mdt thiit bi dien phan PEM gom cd cac bd phan sau (hinh 9) [11,12]; d giira la mang Nation, hai ben mang dugc dan (hoac phu) ldp xiic tac catdt va andt
1'uy4n tap H^ „gni Khoa hoc ky ni$m 40 nSm Vien Han lam KHCNVN - Ha Ngi, ngay 07/10/2015
(MhA) sau dd den tim thu dien va t i m ludng cue. Nude cap duoc gia nhiet bang nhiet do latn viec ciia thidt bi khoang 80°C 6 phia andt di qua cac kenh trong cac tim lirdng cvc va khuech tin vao t i m thu dien rdi ddn ldp xuc tac, tai day cac qua trmh dien hda se dieii ra va kit qua la khi dxy thoat ra d andt, khi hydro thoat ra d catdt. T i m thu dien va bd ludng cue thuong duac c h i tao bing titan (d phia andt) va graphit (d phia catdt).
mmi
Hinh 9. Cdu tao vd cdc chi tiet cua thiet bi dien phdn nuacsu dung mdng ngdn trao doi proton (PEMWE)
2.2.2. Xiic tac dien cue cho dien p h a n nirdc P E M .
Mang ngan trao ddi proton gay ra hien tugng an mdn axit ddi hdi v£tt lieu dimg trong PEMWE phai la vat lieu dac biet. Nhiing vat Ueu nay khdng nhiing chiu an mdn khac nghiet trong mdi trudng pH thap (pH~2), ma cdn phai duy tri dugc d dien ap dau vao cao (~2V), dac biet d dieu kien mat dp ddng cao. Ben canh dd, \'at lieu xiic tac phai thda man cac yeu cau sau: phai cd boat tinb xuc tac cao cho qua trinh oxy hda dien hda ben mat andt va giam O"' sinh ra ben catot. Ben canh dd ciing ddi hdi phai cd dp ben cao va cd kba nang dan dien tdt nham giam dien trd giira cac ldp xiic tac, chi phi che tao thap \ a cd the san xuat vdi sd lugng Idn, kha nang tai tao cao. Chi cd the lya chpn dugc mdt vai vat lieu thda man cac yeu cau tren. cac vat lieu nay thuong khan hiem, dat lien thudc nhdm kim loai quy nhu Pt, Ir va Ru.
Kbi dien phan, tai andt xay ra qua trinh thoat dxy. nude bi dxy hda thanh dxy va ion H . Cd the md ta co che thoat dxy tai andt xay ra theo cac budc sau:
S + H^O ^ S-OH\d, + H ' + e"
S-OH\ds -^ S-OH,ds S-OH,ds -^ S-0,ds + H" + e- S-0«ds ^ S + (1/2)02 S la nhiing diem boat hda tren be mat andt
S-OH"ads , S-OHads - S-Oads la nhirng dang h i p phu trung gian cua S.
Mdi trudng lam viec trong qua trinh dien phan rat khac nghiet vdi pH thip, dien t h i andt cao nen cac vat lieu thdng thudng nbu Ni va Co khd cd the sii dyng dugc do su an mdn \ a i lieu Ni \ a y val lieu viic tac cho qua trinh thoat dxy thudng la cac dxit kim loai chuyin tiep. Trong sd nhirng dxit cua kim loai chuyen tiep RuO: va Ir02 cd dp din kim loai cao nhat. khoang 10 cm- Q" , cd cau tnic rutil la cau tnic x I p chat. Nbung dxit cd c i u mic rutil rat ben trong cac mdi trudng cd tmh xam thuc manh.
Tiiu ban: Khoa hoc Vat heu
Oxit IrOi la chit xiic tac dien hda ly tudng cho qua trinh thoat dxy rat ben viing cho qua trinh nay cd thdi gian su dung Idn han khoang 20 lin so vdi RUO2. Tuy nhien, IrOj c l dp boat hda th%> va dit ban ijiieu RuOs vi nd la mdt trong nhiing nguyen td hiim nhir trong ldp vd trai dit. Ngugc lai RUOT cd dp boat hda cao nbung lai bi an mdn vdi tdc dp dang k l trong qua binh thoat dxy. Viec ket hgp hai dxit RUO2 va Ir02 nham tdi uu giuad$
boat hoa cao va gia thanh thip ciia RUO2 vdi dp bin viing tdt ban cua Ir02 da dugc nghien ciru. Cac nghien ciiu ciing chimg minh dugc rang khi them Ir02 vao RUO2 da cai thi^
dang k l dp b i n ciia andt hong sudt qua tiinh Ihoat oxy. Mdt lupng nhd kOi (20%) cd mOt, anh hudng rit Idn va giam tdc dp an mdn ciia cac dxit xuong khoang 4% so vdi gia tri ban 1 dau. Hang loat hon hop dxit he hai, ba ciu tii da dugc thii nghiem. Ngoai 2 cau hi chinh lii | RUO2, Ir02, cac dxit re b i n hon nhu Ti02, Ta205, Nb205, Sb205, Sn02 dugc bd sung vao de lam tang do ben va giam gia thanh cua xiic tac.
Tu khi dugc phat minh vao nam 1967, dien cue andt tro (DSA) dugc biet den la t6 hgp xiic tac hdn hgp dxit kim loai qui Ru02lr02 cd bo sung them mgt vai dxit kim loai khac nhu Ta205, NiO ... phii len tren n I n vat lieu Ti bang phuang phap phan buy nhipt da dugc sir dyng pho bien lam dien cue andt cho nhieu qua trinh dien phan khac nhau.
Tuy nhien, cac dien cue andt tro khdng phu hgp de sir dung trong PEMWE do tiep xfic khdng tdt giiia cac ldp dien cue va mang trao ddi proton lam tang dien trd ciia h? va lam giam hieu suat qua trinh dien phan. De khac phuc hien tugng nay, cac vat lieu xiic tac dang bdt che tao bang cac phuong phap thiiy phan, qua trinh polyol, nhii tuong...
da dugc tap trung nghien cuu. Vat lieu xuc tac thu dugc cd kich thudc vai chyc nanomet vdi dien tich be mat rieng len hang chuc m"^/g. Do dd boat tinh xiic tac cua cac bdt dxit kim loai tang len rat cao va dugc phii tryc tiep len tren mang trao doi proton vdi mat dp phd bien khoang 1 -4mg/cm^ giam dang ke lugng xiic tac sir dung VEl gop phan lam giam chi phi cho cac PEMWE [13,14].
Viec tieu thy nang lugng trong be dien phan chu yeu tren dien cue thoat dxy. Vi vay tang kha nang xiic tac ciia andt la tang hieu suat ciia be dien phan. De giam gia thanh dien cue xiic tac cd the sir dyng ket hgp cac vat lieu re tien ban hoac giam lugng chit xuc tk.
2.2.3. Vat lieu xiic tac bot Ir^Rui.jO;.
E)a duge tdng hgp thanh cdng vat lieu xiic tac hot Ir;(Rui-,(02 (x= 0,7) cho phan iing thoat dxy y-en dien cue andt trong qua trinh dien phan PEMWE bing phuang phap thuy phan sir dung tiin chit RUCI3.XH2O va IrCls.xHaO [15,16].
Hinh 10. Gidn do nhiiu xa tia X ciia cdc mdu hot xuc tdc Ir^Rui-^O? vai x = 0; 0.5; 0.7; 1 vd dnh SEM ciia mau x=0,7.
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TuyS^p Hgi nghi Khoa hoc ky mem 40 nSm Vien Han lam KHCNVN - Ha Noi. ngay 07/10/2015
" ' " " • ' ^^* °t^^ ^ ^ y \'a SEM cho thay cac hat xuc tac thu dugfc tuong ddi ddng deu.
CO kich thudc nano nhd hon 50 nm va ciu true rutil. Cac hdn hpp hot xiic tac o^ "^^ * " ' ' " d c cd boat tinh tdt ban h O ; va cd dp ben hon RUO2, chi can them 30 /b rutheni theo ti le moi thi dp boat bda va dp b i n cua hdn hpp bdt xuc tac da dupe cai thien dang ke. Vat lieu ho ,Ru(, 3O2 la hon hop bdt xuc tac bdn nhit hong hpng mdi huong H2SO4 0.5M tai gia hi mat do ddng 200mA/cm^ (thdi gian sdng len d i n 24 gid) va CO dien tich be mat rieng len ddn 56 mVg
0,00000010,000001 0,00001 0.0001 0,001. 0.01 BbazOiiafA'i
(b)
Hinh 11. Dien tich be mat ning BET bot xuc tdc Iro yRuo 3O2 (a) vd duang cong phdn cue andt (b) cua cdc mdu bot xuc tdc lrjcRui-x02 trong dung dich H2SO4 0.5M; toe do quit thi SOmV/s
10 -l 9 -
H ? •
^ 6 •
3 -i
0 - - - — 0 5
RuO,
1
;
10 Thiri g
Iro.
15 an (giff)
RU(ij03
1 1
2 0 iTojRUojO-.
1
/
2 5 fO,
3 0
Hinh 12. Do thi do thi tlieo thai gian ciia hon hgp bgt xdc tdc lr:tRui-^02 trong dung dich H:S04 0 SM tai mat do dong 200mA/cm'
2.2.4. Thiet ke, che tao dien cue M E . \ va P E M \ \ ' E d o n gian.
Da nghien cuu che tao dien cue mang MEA bang phuong phap ep nhiet tai cac gia tri luc ep 400psi, SOOpsi l a 600psi. Gia tri luc ep cd anh hudng nhiiu d i n tinh chit cua MEA cung nhu PEMWE. Dien cue mang ep tai diiu kien luc ep 500psi cd tinh chit dien hda tdt ban ca khi su dung hong PEMWE.
577
Tiiu ban: Khoa hoc Val lieu
1000 rsixi
7i. Bo thi phdn cue the tinh cda bo PEMVf^E sic diing ba loai MEA che tao tgi cdc gid tri luc ip 400, 500 vd 600psi.
Da che tao thanh cdng bd dien phan PEMWE edng suit nhd vdi di^n cue ming MEA che t^o bing phuang phap ep nhiet va 2 ciu hinh ciia bp tach ddng (CHI, CH2).
Hinh 14. Cdu tao hoan chinh cua bp PEMWE
/
S.&
D O D D D D D Q O D
• D D D D
• D D D D O D D D D
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C a u h u i h l ( C H l ) _ Ciu hinh 2ICH2) Hinh 15. Cdc cdu hinh khdc nhau ciia bg tach ddng.
ta h " ? '^''^' *?''.™f PEMWE cung bi anh hudng nhiiu bdi ciu hinh cua bp phan '^^ °ig-^Cd thi thiy ring ciu hinh 1 hieu qua ban cho qua trinh tach khi hong nuoc nen ddng dien do dupe cd gia hi cap hon nhiiu so vdi ciu hinh 2.
578
I'uyin tap Hgi nghi Khoa hoc ky niem 40 nam Vien Han lam KHCNVN - Ha Ndi, ngay 07/10/2015
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C ' W * A
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ffin/i i 6 . i)d thi phdn cue the tinh ciia bg PEMWE su dung hai loai loai cdu hinh khdc nhau.
3. KET LUAN
- Trong ITnh vuc bao ve catdt chdng an mdn cac cdng trinh sat thep, Vien khoa hpc vat heu da nghien cuu che tao dupe cac Ipai anot hy sinh hpp kim kem va hpp kim nhdm cd dung lupng dien hda cao, bda tan tdt, chat lupng tuong duong vdi cac vat lidu Cling Ipai tten thi gidi va da cung cap cho tbi trudng tu nam 1995 de bao ve vd tau iapa va cac cdng trinh hong bien.
^ - Trong nhimg nam gin day dien cue anot ha MMO Ti/Ru02lr02Ti02 cd dp bin (^, tdc dp hda tan rit thip khpang 0,01 g/A.nam da dupe chi tap va ap dimg hong bao
# catdt bing ddng dien ngoai di bao vj cac cdng trinh hong mdi trudng dat va nude biin vdi thdi gian dai va bieu qua kinh te eao.
- Cac qua trinh dien hoa hong dung dich nude thudng keo theo qua hinh thoat dxy.
Qua trmh nay lam giam dp bin dien hoa cua anot hen co sd Ru02. Andt Ti/h02Sb205Sn02 vdi ham luong Ir02 thip <3% cd dp bin cao ddi vdi q^ua hinh thoat oxy va qua thi hioat dxy cao phii hpp cbo xu ly nude thai chiia cac chat hiiu ca dpc hai khd phan hiiy bing vi smb.
- Da budc diu nghien curu chi tao dupe vat lieu andt C/Ir02Ru02 cho qua trinh dien phan nude di chi tao hydro. Say ciing la huong di mdi, tiin tdi su dung nang lupng xanh vdi nhien Heu la hydro.
LM cam tm. Tran hpng cam an Vien Han lam Khoa hpc va cdng nghe Viet Nam, Chuang hinh hpng diim cip nha da tai hp cho chung toi thdng qua cac de tai KC.02.04/06-10,VAST.NDP.02/14-15.
Tai lieu tham khao
1 Pierre K.R; Handbook of corrosion engineering, 1* edition (2000).
2. Lazzari L., Pedefeiri P., Cathodic Protection, 1" Edision (2006).
3 Ket aud thu vd kiem tra tinh chdt cua protecto cua Ddng kiim Viit Nam so 256/07CN.01 ngay 23/01/2008.
4 Cathodic protection company limited product datasheets; CPCL, (2008).
579
Ti4u ban: Khoa hoc V$t lieu
5.Nguyin Ngpc Phong, Dd Chi Linh, Pham Hdng Hanh, Ngo Anh Tuylt, dxy hod diin hod cua phenol tren diin cue tra Ti/Ru02lr02Ti02 trong moi truong kiem. Tap chi Hda hpcl 11 Vol. 47, U.226 (2009).
6. Nguyen Ngpc Phong, Bao cao de tai cip Nhanudc ma so KC02/06-10: Che tao diin Ofc anot tra co do bin cao di xu ly nuac thdi cong nghiep bdng phirang phdp diin hoa.
7.Kroon D.H, Emes L.M. - MMO coated titanium anodes for cathodic protection -Parti,
Materials Performance 45(5), 26-29 (2007). ' S.Lihm X., Tingyong W. - Impressed current anode for ship hull protection. Materials |jj
Performance 47(6), 40-42 (2011). J! I 9.Maccelo Carmo ei al. A coprehensive rewiew on Pem water eletrolysis. International •
joumal of hydrogen energy 38,4901-4934 (2013). % 11 10. A.Marshall el al. Performance of a PEM water electrolysis cell using Ir^RuyTaiOi
eletrocatalysts for the oxygen evolution electrode. Intemational joumal of hydrogen energy 32, inQ-lZlA (2007).
11. Shidong Song el ai. Electrochemical investigation of electrocatalysts for the oxygen evolution reaction in PEM water electrolyzers. Intemational joumal of hydrogen energy 33, 4955^961 (2008).
12. AMarshall el al. Electrochemical characterisation of lrxSnj-x02 powders as oxygen evolution electrocatalysts. Electrochimica Acta 51, 3161-316 (2006).
13. Egil Rasten. Electrocatalysts in Water Electrolysis with Solid Polymer Electrolyte.
Norwegian University of Science and Technology. URN:NBN:no-7264. 10.2001.
14. N. Tunold, A.T. Marshal. Materials for electrocatalyis of oxygen evolution process in PEM water electrolysis cells. ECS Trans., 25,103-117 (2010).
15. Pham Hdng Hanh, Nguyen Ngpc Phong, Do Chi Linh, Ngd Anh Tuylt. Nghien cuu tdng hop v$t li$u IrOj xuc tdc cho phdn ung thoat oxy trong di^n phdn mdng trao dii proton. Tap chi Hda hpc 152 (6A) (2014).
16. Hong Hanh Pham, Ngoc Phong Nguyen, Chi Linh Do and Ba Thang Le. Namsized IrxRui-x02 electrocatalysts for oxygen evolution reaction in proton exchange membrane water electrolyzer. Advances in Natural Sciences: Nanoscience and Nanotechnok^, Nanotechnol.6, 025015 (2015).
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