A unique energy-storage system has been developed at NASA's Lewis Research Center called REDOX. This NASA-REDOX system is an electrochemical storage device that utilized the oxidation and reduction of two fully soluble redox couples for charging and discharging. The redox couples now being investigated are acidified chloride solutions of chromium (Cr(+2)/Cr(+3)) and iron (Fe(+2)/Fe(+3))

Terman, D. K.

English

NASA Technical Reports Server

ORIWAL PAGE IS 
OF POOR QUALITY 
. 
THE CHEMICAL BEHAVIOR 
OF ACXDIFIED CIiFMIUH (111) SOLUTIONS 
(NASA-Ck-172997) I r i E  ChEf l ICAL U E i i A V I O R  CF 183-32d71 
AC1i)IPIED CYPOUIULL (3) SuLUTIGlrS B. S. 
T h e s i s  /Spr-iny Arbor C O L A . ,  fYicn.) 29 F 
fiC AO3/HE A01 CSCL 070 rJ n c l a  s 
G3/25 15007 
Thesis 
submitted i n  Partial Fulfillment 
for Hanors i n  Chu11~ist.ry 
to the 
Faculty o f  Spring Arbor College 
bY 
Darlene X; Tennan 
May 1981 
https://ntrs.nasa.gov/search.jsp?R=19830024600 2020-03-21T03:01:22+00:00Z
APPROVAL OF EXAKININC ODXMITRU 
TABLE OF CONTENTS 
--
PAGE 
-
. . . . . . . . . . . . . . . .  Acknowledgements i 
Introduction . . . . . . . . . . . . . . . . .  1 
C o n c l u s i o n . . . . . . . . . . . . . . . . . .  22 
Bibliography . . . . . . . . . . . . . . .  25 
C?:?!?!p.: PI',GZ IS 
GF POOR QUALITY 
The author  wishes to express h e r  s incere  g r a t i t u d e  to Dr .  David 
A. Johnson f o r  h i s  guidance, encowagemen t, and for h9s unending pat ience 
throughout the  length of t h i s  research. 
The author a l s o  wants- t o  express appreciat ion to the  Natiocal 
Aeronautics and Space Administration at Leuis Feseivch Center who provided 
fundin& f o r  t h i s  research through the Energy Directorate ,  S o l a r  and 
Electmchernistxy Division. 
The author a l s o  wishes to express a spec i a l  thank-you to Jeffrey 
9. Cingrich f o r  h i s  un t i r i ng  dedication to the  research, his much-needed 
help, &.d f o r  h i s  spec ia l  f r iendship  and pat ience ?itring t he  course o f  
t he  research. 
Last ly ,  the author  wishes to express her appreciat ion to Leland 
M. Coffnan for h i s  support md understanuing througiiout tha research and 
espec ia l ly  i n  t h s  preparation of  t h i s  paper. 
ORIGfNAL PAGE IS 
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THE CHEMICAL BEHVIOH UP ACIDIFIED CHRDMIUM (I 11 ) SOLUTIONS 
INTrn WCTION 
A unique energy-storage system has beer. developed at NASA's 
Lewis Research Center ca l led  REWX. This NASA-FEI);)X system is an 
e l  C t r o c h e ~ i ~ a l  storrye device t h a t  u t i l i z e s  the oxidation and reduction 
of two f u l l y  m l u b l a  redox couples fo r  ch.1rgi.w and discharging. The 
redox couples now being invest igated am a c i d i f i e d  ch lor ide  so lu t ions  of 
chmmiun (c="/c=+~) and iron ( ~ e + ' / ~ e + ~ ) .  Figure 1 shows the system i n  
its s i r n ~ l e s t  form. 9 
The basic flow c e l l  cons i s t s  o f  two porous carbon-felt  e lec t rodes  
separated by a sheet  of membrane nn te r i a l .  The membrane is a highly 
se l ec t ive  ion exchange membrane. I t is er~~:ineorctii to almost completely 
p m h i b i t  tho passage of i ron  and chr~mium ions but allow easy passage 
of  chloride and hydrogen ions (fig. 2) .' I:, the development of the 
electrodes,  it was found that the r a t e s  of  oxidation and reduction of 
ferrous and ferric ions were rapid enout:h t.hat a c a t a l y s t  was not  needed. 
However, the chromium s i d e  d id  requi re  :A 6xlt+%ly~ta. Therefore, gold 
and lead were added to the chromium o l c c t r ~ t f e .  The lead has long 
+3 been known as 'an e f f e c t i v e  c a t a l y s t  f o r  retli~Ction of  C r  . The presence 
o f  small 3~nounts o f  gold an? needed to p~*ovidc 3 surface on which the 
lcwd p l a t e s  during charging. 7 
The REIXIX so lu t ions  a r e  pumped through the porous elect.rodes.' 
As the system is being charged, the  chromium solu t ion  is mostly chmmic 

PR
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ORIUNAL PAGE IS 
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ion,  and the i ron  so lu t ion  is mostly ferrous ion. During discharge, 
ch lor ide  ions  move from the cathode compartment to the anode compartment 
while hydrogen ions move i n  the opposi te  d i rec t ion .  The discharge process 
is srnmmarieed as followsr 
~t anode: crt2 - cr" + e- 
A t  cathode: + e-  + 2 Fe . 
As discharge continues, there  comes a point  as i n  any ba t t e ry  
where recharging is necessary. Therefore, to rechargo, a awer supply 
is connected to the terminals,  and the reverse electmchcrnical reac t ions  
occur. 9 
This  REDOX energy storage system has some s i g n i f i c a n t  po ten t i a l  
uses. For u t i l i t i e s ,  i t  could provide e l e c t r i c  power companies w i t h  an 
e f f i c i e n t  means o f  load l eve l l i ng ;  that i ~ ,  the storing o f  thousands of  
kilou-?tt-hours of energy during low dern:~nd periods f o r  use l a t e r  during 
periods of maximum power consumption. A l s o ,  REDOX systems could help 
to speed up  the gmwth of solar e l e c t r i c  (Iihotovoltaic) and wind-energy 
systems where the c o s t  of e l c c t r i ~ a l  storrr:c h a s  importar,t considerations.  
Storage is necessary when the sun is not  shining o r  the wind not  blowing. 5 
The fully funct ioning system has had some minor problems. One 
is t h a t  i n  the chromium s i d e  small amoun ta  of hydrogen gas arc evolved. 
This can reduce the efficiency of the'system by one to two percent each 
discharge cycle  i f  uncorrected. However, t h i s  gas has  been f6un.l to  
be e a s i l y  captured a ~ i d  recombined with the iron r c a c * a t  i n  a special 
rebalancing c e l l  b u i l t  into the systerc. 
The second protlcm icvolves difi'crcnces i n  the open c i r c u i t  . 
vcltage and r a t e s  of charge and discharce, Lt it.-:; been noticsd t h a t  
c o l o r  changes occur  d u r i n g  t h e  charco and discharge cycles .  I t  is also 
evidenced by open c i r c u i t  voltage versus  dcpth of d i scharge  p l o t s .  
D i s t i n c t i v e  d i f f e r e n c e s  i n  the colors of t h e  chromium s o l u t i o n s ,  t h e  open 
circuit vo l tages  and rates o f  charge o r  dir;char&e are observed at t h e  
same state-of-charge depending on whether tho c e l l  is i n  t h e  charge 
mode o r  t h e  d i scharge  mode (fig. 4) .  I t  therefore appears t h a t  the 
chmeium s o l u t i o n  invo lves  sever31 con~l)lcx ion specias. Rasearch was 
carried on to d e t r ? n i n e  trie idor~t i  Ly 01' t111::;c ch,romi~;n s~lecias ,and to 
i n v e s t i g a t e  t h e  nuct~anisin:; uf' t h e  oxid;rtion anci reduc t ion  r e n c t i c n  at 
t h e  chromium electmdes. 3 
I n  a prsvious  s tudy,  the rescticns a t  t h e  chmnium e l e c t r o d e  
vere followed spectropho tometr, 2311~. A s i n g l e  c e l l  H a s  taken through 
two charge-discharge cycles, and s one mi l l imete r  f low-cell  was connected 
to the REmX cell  and placed i n  a spectmphotometer.  The spectrum was 
~ u c c ~ r d w  a t  s e l e c t e d  st;~tcs o f  charge from ]p nm to 1000 nm. A look 
a t  t h e  spectra showed two broad bands w J  t i 1  ' uima a t  410-430 nm and 
95-610 nm. 
A l i t e r a t u r e  sea rch  ind ica ted  t h e  f'ollowing complex i o n r  could 
e x i s t  in a c i d i f i e d  c h m i u m  chloride s o l u t i o n s .  
Complex Maxima 
+1 Cr(H20)qC12 450 nm 635 nm 
The s p e c t r a l  peaks were tr111:: :*esolvl-.d j n t o  c,r:c:mporic?nt pe&.s using 3 
DuYant 310 Curve Resolver ( f i g .  5 ) .  
TIlc d.aL3 c1e;lrly :;howcll t . h ~ t  ox i t l , ~  t i  cn u d  reduct ion 'm t t l  
ORIGINAL PAGE IS 
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ORIGINAL PAGE :'!3 
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i 
I 
Z involved c ~ ( H ~ o ) ~ c ~ * ~ .  The charging pn,ct!: ;:i i n  which ~ r + ~  is reduced 
involves red ic t ion  o f  C ~ ( H  0) ~1" i n d i m t c d  by a marked decrease i n  2 5 
the concentration of ~ r ( l l ~ ) d ~ .  Tbo disdmrge  pmccas illno involvcn 
! 
1 c ~ ( H ~ o ) ~ c ~ + '  i n  which c=+* i n  oxidized to crt3. This reac t ion#  
1 c ~ ( H , o ) ~ c ~ + ~  L * e-  C r i H  0 )  ~1" I 2 5 1 is revers ib le  and OCCUAFS through a c:.loridc-bfidged, i nne r  sphere pathway 
'r 
I as denonstrated by Anson. 4 + 
! Because the spectropho tome t r i c  :; tudies  involved resolving the 
i composite peaks into the component peaks it seemed judicious to  see if 
I 
I ' the complex ions  present  i n  c e l l  so lu t ions  could be separated and 
! I 
i 
t identified. 
i A l i t e r a t u r e  search indicated that throe complex i ons  could 
i 
! be expczted to be i n  aqueous so lu t ions  o f  a c i d i f i e d  chmmicehloride. 
The threo complex ions  a m  hcxaquochmmium (III), chloropentaaquochronium 
(I1 I ) , imd terms-df chloro tetraaquochromium (111). Figures s i x  and 
seven show t h e i r  s t ruc tures .  
Robert J, Angelici h a s  prepared ,and separated the complexes 
using ion-exchange chromtogmphy. The column used w a s  prepared w i t h  a 
+ bwcx SOW-XS, cation exctmigc resin, W .  100 mcsh, H form (fic. 8). 
. T. 
A buret approximately s i x t y  centimeters long imd one centimeter i n  diameter 
was plugged with g l a s s  roo1 a i d  ~ J ~ I I  f i l l c ~ l  t,o f i f ty  centlmotor:; wittl 
I I.. a s l u r r y  of t h e  Dowex resin. 
A 1 M CrC13* 6H20 ::al:~tion Mati I W L ~ C  by disso lv ing  26,64Y+ grams 
i n  100 milliliters of 0.00% M HCICII,. The first complex t o  be prepared 
and xe )unt t :d  was the tr~n~;-tlicl~lomt~rtm.1.r~1toct1mmil1m (111). Five  
- .- -.- 
O R I M A t "  PAGE TS 
OF POOR O?I:ICITY 

0R:CfNAL PtGF iS 
OF POOH QllALiTY 
6 -7.t. . 
:t It. 
: ,, * 
Y 
ir ORlGfNAL FAG," :S -1 3- 
OF POOR QUALITY 
m i l l i l i t e r s  of the 1 I CrCl ' 6H20 solution was transferred direct ly  3 
to the res in  ca luu~.  The solution w a s  rh~rined to resin level and then 
0.1 II HCLOI, was added continuously us ire  ;L syphon. 'he elutvlt w a s  
allowed to flow about one drop per second. The progress of the green- 
colored solction was fc'low~d down the  column and was collgcted at its 
rost  intensely colored portion ( t ~ b l e  1).  Th9 visible spectra was run 
and naximua absorption peaks w e r e  obtairlcd a t  450 M and 635 rn (f ig.  9). 
The chlompcn~quochmciium ( I 1  I )  ~ 3 s  p m p r e d  by warming ten 
a i l l i l i t e r s  of the 1 H C r C l  ' 6H20 solution i n  a water bath at f if ty- 3 
f ive degrees celsius f o r  a minute and a half. I t  was then diluted with 
ten milliliters of d i s t i l l ed  water and transferred direct ly  to a h s h  
resin column. The solution w a s  drain& to resin level  and 0.1 I4 HCW4 
H a s  syphoned onto the .coluun to e lu te  out the unreacted C ~ ( H ~ O ) ~ C ~ ~ ~ '  . 
This w a s  fallowed down t h e  column and collected. Then 1.0 H H C U 4  
I .- 
t. w a s  pahsed through the column to clutc  the C ~ ( H  0 )  ~l+*. This solution 2 5 L 
i was also green, and its pxmgress war; crrsily followed down the colum 
and collected a t  its most intensely colnmd portion ( table  2). The 
spectra of t h i s  solution showed nrutimum absorption peiiks a t  430 nm and 
t 605 tlm ( f ig .  10). 
The last complex, hex~~~ci~ochmm i l ~ m  (111 ) , was prepared also 
usiw the s u e  1 M C r C l  Ui2G i n  0.002 M IiCIQa. Ten n i l l i i i t e r s  Mas 3 
diluted u i t h  ten milliliter:: of di:;til lctl  u;it.r!r and lhcn boiltxl f ~ r  five 
minutes. Tcn more millili tc-rs of d i s t i l l e d  water w a s  added and the  
resulting solution transferred to a f r e sh  rrrsin column. Again the sol-  
ution was driined to resir1 level .  The 1.0 M H C U 4  was added f i r s t  to 
e l ~ t e  off NIY unmacted Cr(H. 0 )  CI *' or Cr(ii 0) C1"2b Finally 3.0 2 4 2  2 5 
.. 
mA.L PAGE rS 
OF QUALW 
TRANS - CRCL-, L  OH^ 14+ 
! ; C R E L ~  61120 DISSOLVED I N  O.O@f! IICLO,~ 
OR!GINAL PAGE IS 
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ORIGINAL PAGE IS 
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HCID4 wrs added to e lu  1,s the c~(H.,o)~+'. nris solu t ion  was n d i s t i n c t  
L. 
blue c o l o r  i n  con t r a s t  to t he  othcr species which were green. This, 
too, w a s  co l lec ted  at its most intennaly cmlored portion and tho spec t r a  
obtainad ( t a b l e  3). The maximum absorption peaks were obtained at 407 na 
(Ud 575 ru (fie. 1 l ) . l  
I t  should ba noted t h a t  the & h a r p t i o n  peaks obtained uere 
8 i den t i ca l  to those found by Thomas U. Swaddle, award L. K i n g ,  and 
Ph i l i p  J. Elving i n  t h e i r  prepamtion imd i d e n t i f i c a t i o n  o f  these com- 
plexes. 2 
The ac id i f i ed  CrC1 so lu t ion  used i n  t he  NASA-REDDX cell was 3 
analyzed to determine the  iden t i t y  of  the comple; sons present.  The 
Cell so lu t ion  *as p r e ~ r e d  by d i s s o l v i r i ~  26.5896 gr?.as of CrCl ' 6H20 3 
i n  100 m i l l i l i t e r s  o f  1 M HCL. To:; milliliters w a s  pipe t tcd  d i r e c t l y  
in to  a fresh r e s i n  column. Thc sr~ml)lc u:ts f i r s t  eluted with 0.1 M 
HCID4. The green-color~cd s o l u t i o n  Ha:; t:ol.locted u n t i l  t he  f r ac t ion  
was c l ea r .  Twen ty-f i v e  inillili terr; xerc col l c c  ted. 'The next  e lu t ion  was 
with 1.0 M HCI.04. Again, ;r ~.rr?cn-colort!d ::olntion w a s  co l lec ted  un ti1 
the column f r ac t ion  was c l a u .  Th i s  time 195 m i l l i l i t e r s  w a s  col lected.  
Lastly,  3.0 M HCUI4 eluted o f f  172 m i l l i l i t e r s  of a blue-colored solu- 
t ion. The spectra of f r ac t ions  were oblaitictl using the Bausch and Lomb 
Spectmnic  20. The s p e c t r ~  of the first f r ac t ion  showed maximum ab- 
sorption peaks .:t 430 nm and 605 nm. The second f r ac t ion  had absorpt ion 
1~ie;Jts a l s o  i t  430 nm and 605 nm. Tho l a s t  f r ac t ion  had maximum ab- 
sorption peaks at 407 nn and 575 nm, c h s r x c t c r i s t i c  o f  t he  Cr(H 0) +3 2 6 '  
Fmn these spec t ra  it be concluded that no c ~ ( H ~ o ) ~ c ~ ~ ~  was present  
i n  the c e l l  so lu t ion ,  and only Cr(ll  0 )  ~l* '  and ~r ( f$0 )~+ '  existed ( t a b l e  4). 2 5 
TABLE 3 

CELL UWQN 
. - 
., . 
.i 4. ORIGINAL PAGE IS -22- 
i 
OF POOR QUALITY 
Ncx t, the c u l l  :;oluLion wliich 1i.d leetl r u n  through two ctl;~r(;e- 
k 
! discharge cycles  was ancrlyzcd to idttntit'y tho ions present. 
grams in 9 0  m i l l i l i t e r s  of 1 M HCL. T h i s  colut ion was then placed i n  
the battety and run through two charge-discharge cycle; a t  .32 amps. 
Immediately upon the second disch;rq:c, Lcn m i i l i l i t e r s  was p3.n' 'ed 
out  and trilnsferred d i r e c t l y  to a f r e s h  re:;in column. .leain . ?- 
began with 0.1 M HCW4 followed by 1 .O M IICWI+ and 3.0 M HCLOb. Thir ty  
m i l l i l i t e r s ,  287 m i l l i l i  t e r s ,  a i d  380 m i l l i l i t e r s  respec t ive ly  were 
col lected.  Three so lu t ions  were collectud and the  spec t ra  obtained 
using the S p c t r o n i c  20. The f i r s t  tho s o l l ~ t i o n s  q p i n  had the same 
maximum absorption peaks st 430 nm and 605 rim c h a r a c t e r i s t i c  of  the 
0rilt 0) ~1'~. Thc las t  f-raction a.cain tmi m;uimum absorption peaks at  
2 5 
407 nn and 575 nm shoui ng t h e  prLscnce of  C ~ ( H ~ O ) ~ + ~  ( table 5). This 
proccdux.c using the so lu t ion  from t h e  two charge-discharge cycles  was 
performed twice. DaLi obtained coi ncidccl a:: fir as the spec ies  present 
was concerned. The rntio of  the two complcxcs differed s l i e h t l y  ( t a b l e  5). 
Another d l f f e r e t ~ c e  between the two trials is t h a t  the  first procedure re- 
sul ted i n  some dimers formed rem:rir~inr: i n  the column, No dimcrs were 
prczser~ t thc second time. 
'33NCLUSION 
The data c lear ly  :;hous t h a t  the three complex ions, trans- 
~l i ch lo ro te  truquochromiurn ( I I I ), chloropcn t,;r.uluochromium (If  I), and 
hexai~~r~ochrorni~~rn (111) have  beer1 prepared,  :;oparatod using 
ion c!xchange chromatol;rlijjhy, xnd idc l i t i f  icd :jl)t? t~ 'c '~hotonetr ic?. l l  y . :n 
+ 2 + 3  hnvo hnen tlic orir:in;il aoll soh: t , i u n ,  Cr( l l . ,O)  , C1 : ~ r 1 1 i  fir(!120)c, 
6.  .) 
CELL 
ORIGfNAL PAGE IS 
OF POOR QI.IAi!TY 
SOLUTlOfl AFTER 2 CllARGE-Dl SCI IARG CYCLES 
(132 AMPS) 
SPECTRA MAXIMA 430 NP! , GO5 NM 
ORIQWAL PAGE IS 
OF POCR 'c '.-1'TV 
+2 identtfied as the principle chromium species with cr(h20) C 1  p n -  5 
dominating ( t a b l e  4). In  the cell solct-d.22 ;die= t w ~  chargedischarge 
cyc:es. tlia principle spcies ware C ~ ( H  0) 1+2 and C ~ H ~ O ) ~ + '  with 
2 P 
C~(H~O):~ the predomimtin6 species (table 5). This data correlates 
with the resolved peziks collected earlier. 
The experi~ae~t w i t h  the cell solution ifter two charge-discharge 
cyclcs was perforvied twice. The f i k t  time a dimer was forned i n  the 
colunn; however, the second tine no dimer was found. W h y  the dimer was 
forned the first tile and not the second is not knom and should be the 
subject of furtbr study. 
ORIGINAL PAGE IS 
OF POOR QijALlTY 
;ingelici, Robert J. Sytlihesi:; :~nd  'rc!cl!niil~le i n  1 r io r~ : ;~n ic  Chemistry. 
Phi ladelpnia :  W. 0. Scrtinder. C:)mpny, 1969. 
Elvirq:, P h i l i p  J . a id  Zt:mel, Bcntatr i .  "Abhor;!tion i t 1  t h e  Ul ha- 
v i o l e t  arid V i s i b l e  Region:; ~f ~;t~lir-.~aquochrolliumi (111) 
I o n s  i n  Acid Hedia," Journa l  of t h e  American chemical 
Soc ie ty .  Vol 79, M~mtl 20, l y p .  
Gahn, Handall F., Clx~r les ton ,  JoAnr~, Lint:, J e r r y  S. , and Reid, 
Wgaret A. I 'c r fornrmce of A u v ~ c e d  Chromium Elec t rodes  
f o r  the NASA-REDOX Energy Stor;se System," Nat ional  
A c m n u t i c s  and Spzcc A d m i n i s t n t i c n ,  Lewis Research 
Center,  Clevelruld, r):lio, F a l l ,  1980. 
Johnson, David A. "Chemical and Electrochemica'L Aspects o f  the 
C h m a i c / ~ h r o a o u s  E lec t rode  Reaction i n  t h e  ?USA-RZmX 
Energy S t o m g e  System," Report to NASA, Awst 1, 1980. 
Kationrrl Aeronautics and S p c e  Adninic t r a t i o n ,  "new F l u i d  B a t t e r y  
Pmmises  tr, Store E l e c t r i c i t y  More Cheaply and Benef i t  
Both S o l a r  and Conventional Power Generation System," 
Rele.se 79-1 5, Dis t r ib l l ted  Flarch 28, 1979. 
Reid, Margaret A . ,  !;ahn, Randall F., Liric, Je? . , S., and Charles ton,  
J o h n .  "Prcpration and Ctx~r;rc:tcrization o f  E l e c t m d e s  f o r  
t h e  NASA-REDOX S t o w e  Systcm, " ij7't.h Meeti. o f  the 
E l e c t m c h e l i s t r y  Soc ie ty ,  S L. Inui:i, i s ,  IX)&ASA//j l'H to 
be pu bl i shcd  . ) 
Reid, Margaret A. and rn~ller, Lrwrcr~ce H. "Improvement and Sca le -  
up o f  the  NASA-RSmX S t ~ r i e  Sy:;tem, " National Aaranaut ics  and 
Space Adminis t ra t ion,  Lewis Rcl.::c!srch Center,  C lcve lmd,  Ohio. 
Swaddle, Thoinas W.,  and King, Ednard L. "The Rate o f  Aquation 
o f  H a l o p e n ~ u o c h r o m i u m  ( 11 I )  Ion i n  Acidic  Aqueous Soh- 
tion." ~ o u r n a l  of ~ n o r c a n i c  Chenistzy,  Vol. 4; No. 4, 
Apr i l  1965. 
T h a l l e r ,  Lawrence H. "Redox Flow Energy Storage Systems," T e r r e s t r i a l  
Energy Systems Conference, A I A A ,  Orlando, FL, June 4-4, 1979, 
~ E / N A S A / ~  302/79/3, TM-79143. 


The chemical behavior of acidified chromium (3) solutions

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