An effort was made to study the effects of cation and anion additions on oxygen evolution kinetics on platinum and the inhibitive or catalytic nature of the additions. The kinetics and mechanism of oxygen evolution on planitum metal in hydrofluoric and sulfuric acids, including the effects of foreign anions, were examined. The LEED-Auger-thin layer electrochemical system was developed for the examination of electrocatalytic surfaces. Samples for electrocatalytic LEED-Auger studies were prepared and examined

Huang, J.

Ogrady, W. E.

English

NASA Technical Reports Server

General Disclaimer 
One or more of the Following Statements may affect this Document 
 
 This document has been reproduced from the best copy furnished by the 
organizational source. It is being released in the interest of making available as 
much information as possible. 
 
 This document may contain data, which exceeds the sheet parameters. It was 
furnished in this condition by the organizational source and is the best copy 
available. 
 
 This document may contain tone-on-tone or color graphs, charts and/or pictures, 
which have been reproduced in black and white. 
 
 This document is paginated as submitted by the original source. 
 
 Portions of this document are not fully legible due to the historical nature of some 
of the material. However, it is the best reproduction available from the original 
submission. 
 
 
 
 
 
 
 
Produced by the NASA Center for Aerospace Information (CASI) 
https://ntrs.nasa.gov/search.jsp?R=19750017990 2020-03-22T21:39:31+00:00Z
I
(NASA-CB-143061)	 CATALYSTS FOR	 N75-,!b062
ELECTHOCHF.MICAL GENERATION OF OXYGEN
Seaiannual Status P A port, 1 Oct. 1974 - 31
Mar. 1975 (Case western Reserve 11niv.)	 1b	 tJnclasS HC $3.25	 CSCL 07D G3/15 113052
'ROCHEM:STRY RESEARCH LABORATORY
OZPAWrKZlff OF CHZMIMY
JOHN SCHOFF MILLIS SCIENCE CENTER
CASE WESTERN RESERVE UNIVERSITY
CLEVELAND, 0410 44106
Semi-Annual Statu: Report No. 6
1 October 1974 to 31 March 1975
CATALYSTS FOR ELECTROCHEMICAL GENERATION OF OXYGEN
Report Prepared by: W. E. O'Grady and J. Huang
Project Director: Ernest Yeager I
NATIONAL Ar.RONAUTICS AND SPACE ADMINISTRATION
NASA-Ames Grant Nos. NGR 36-027-050
L	 NGR 36-027-052
ELEC'I'R0GIIE.NIIS'I'RY RESEARCH LABORATORY
DEPANTNIENT OF CIII-MISTRY
JOHN SCHOFF NIIIAAS SCIENCE: CENTER
CASE WESTERN RESERVE. UNIVERSITY
CLEVELAND, 01110 44106
Seni-Annual Status, Report No.
1 October 197 4 to 31 March 1975
CATALYSTS FOR ELECTROCIIINICAL GEIIMATION OF OXYGEN
Report Prepared by: td. E. O'Grady and J. Huang
Project Director: Ernest Yeager
NATIONAL AFRONA11TIC2 AND SF'ACF. ADMINISTRATION
rIASA-Ames Grart Nos. NOR 36-027-050
NOR 36-02T-052
References
Figures 1-9
i
TABLE OF CONTENTS
PnFe
List of figures
1. Primary objectives	 1
11. Specific objectivt• s for this reporting period	 1	 I
III. Summary of the wort, 	 1
1. Kine Lics and mechlni.nm of oxygen evolution on
platinum	 1
2. Development of the LEED-Auger-Thin Layer electro
cheriical system	 4
3. Preparation and examination of samples for electro
-catalytic LEED-Auger studies	 S
IV. Projected work	 6
V. Project Personnel	 7
Figure 7. Auger spectrum of a partially cleaned Ru
(1170) surface (heated to 600° C).
Figure 8. Auger spectra of a cleaned Ra (1120) surface
a) Argon ion sputtered and heated to 1000° C.
b) Argon ion sputtered and heated to 1200° C.
Figure 9. Schematic !XED Patterns of Ru (1120)
a) Clean surface corresponding to the Adger
spectrum shown in Fissure 8h.
b) In i t
surf,
14
15
16
II
1	 .^
LIST OF FIGUREF
Pie
Figurc 1. Cyclic voltammogram of Pt with it sweep rate	 I
of 100/mV sec. Electrolyte: 0.1'1 IIF. 	 8
Figure °. Cyclic voltammogram of Pt with a sweep rate
of 100/mV sec. Electrolyte: 0.117 IIF with 10-2
0 IiCl added.	 9
Figure 3. Cyclic voltammogram of Pt with a sweep rate
of 100/mV sec. Electrol yte: MN IIF with 10-2
N It 2 SO4 added.	 10
Figure 4. Relationship of the potential of the initia-
tion of oxide growth with the lop, of the 504.
ion concentration.	 11
Figure 5. Comparison of the cyclic voltammograms of Pt
at a sweep rate of 100/mV sec.
	
12
1) 0.14 11F
2) 0.04 112504
Figure 6. Schematic drawing of the LEER-Auger-Thin Layer
electrochemical system.	 13
Chemistry Department
Case Western Reserve university
Cleveland. Ohio 44106
CATALYSTS FOR T}IE ELECTROCHEMICAL
GE14ERATIO14 OF OXYGEN
Semi-Annual Status Report for 30 September 1974 to 1 April 1975
Sponsor: NASA-Ames
Grant Nos.: NCR 36-027-050
NGR 36-021-052
I. rRIMARY ORJErTIVES
1. To find new, more effective catalysts for the electrolytic
evolution of oxygen and to understand the mechanism and
kinetics for the electrocatalytic in relation to the surface
electronic and lattice properties of the catalyst, as well
as developing; an understanding of the structural features of
the clectrocatalysts kfiich are critical to high electrochemical
activity for the annoic generation of O2'
2. To evaluate the kinetics and mechanism of anodic generation
of 02 under well defined conditions in relation to the prop-
erties of the electrode surface.
II. SPECIFIC OBJECTIVES FOR TIII!; REPORTTNG PTRTOD
1. Kinetics and mechanism of oxygen evolution on platinum metal
in hydroflu v• rc and sulfuric acids including the effects of
foreign anions.
2. Development of the LEER-Auger-thin layer electrochemical system
for the examination of electrocatal ytic surfaces.
3. Preparation and examination of samplen for electrocatalytic
1.EED-huger studies.
III. SL"VARY OF THE WORM.
f
1. Kinetics an-6 mechanisms of oxygen evolution on platinum.
Previous work has indicated that cation and anion additions can
have significant effects on the oxygen evolution kinetics on platinum.
An effort has been made here to study these effects and their inhibitive
or catalytic nature.
We previously reported (1) an anomalous behavior of the growth of the 	
1^
-2-
oxide on Pt in the presence of CsF added to the IIF solution. Ic has
subsequently be; •n found that the CsF was contaminated with Cl which
pave rise to the reported behavior. As a result of this findinp,, we
have investigated the effect of adding Cl to the !IF solution. Figure 1
shows the cyclic voltammop,ram of Pt it: pare U. Chloride is added to the
r
IIF solution in the form of IIC1 holding the concentration of F constant.
The effect of 10-2 M Cl -
 on the growth of the Pt oxide is seen in Figure
2. A co+:na.rison e)f Figures 1 and 2 indicates that the Cl is strongly
adsorbed retarding the growth of the Pt oxide. Below 10 -5 M Cl - no
perturbation of the oxide growth can be detected in the cyclic voltam-
mogram. Ilowever, the Tafel behavior for 0 2 evolution is quite different
from that in pure IIF and this is being investigated further.
A set of experiments similar ;o those of the Cl in IIF were run
adding I1 2 so4 to the IIF. The results are quite surprising. Again the
a
concentration of F was kept constant as the SO 4 was added to the IIF
in increasing concentrations. The addition of the SO,' 5
 perturbs the
cyclic voltammogram greatly (Figure 3). In the ini
	
region of oxide
r
_	 t
growth it is seen that the SO4 is sufficiently strongly adsorbed that
•	 I
the initiation of the oxide formation is pushed to a higher potential
similar to the situation observra with Cl
	 If the potential of the
initiation of oxide growth is plotted against the log ISO:] a li,:car plot
is obtained with a slope of 15mV per decade of [SO4- 1 concentration (Figure
4). When the concentration of 11 2 SO4
 in IIF reaches 0.1 N the
behavior is identical to that of pure 0.1 14 II 2 So4 . The portion of
the cyclic voltammugram in the hydrogen adsorption region also is gte+te
interesting. Conway (2) has postulated from his cyclic voltarimetry stud-
ies of Pt in very pure 11 2 50 4
 that the four peaks observed in the hydrogen 	 `.
region are characteristic of a clean solution. In the results for IIF
we do not find four peaks in the hydrogen region (Figure 1). '.:,,on	 I^
i	 ^	 1	 !	 I	 I	 i	 1
-3-
the addition of 2 x 10 -3 N SO4 four peaks begin to energe in the
hydrogen region (Figure 3). There results indicate that there is a large
a
contribution of the SO 4  ions to the structure in the hydrogen
adsorption region. There now seems to be a question as to the
validity of the four peak structure as a criteria of solution purity.
There does seem to be a larger curren in the double layer region
for the IIF solutions containing SO 4 which might be attributed to the
Adsorption of IIF :aolecules of IIF 2 ions. In order to check this postu-
lation IIF was added to 0.1 N I1 2 SO4 . Prior to the addition of IIF the
cyclic voltamnograms for 0.1 N 11 2 SO 4 were run. This solution of 1f2s04
was prepared using Ultrapure 11 2 SO4 and pyrolyized If 20. The pyrolysis
was carried out in a system similar to the one described by Conway (3).
The voltammograms obtained in this solution exactly duplicate the work
of Conway (2). Previous experiments using triply distilled H 2 O and
reagent reagent grade 11 2 504 could not reproduce the results published
by Conwin y. Further wort: indicated this descrepency to be due to impur-
e
sties in the 11 2 50 4 . When the 11F was adL'ed in varying; concentrations up
I
to 10-1 N F- , no change was detected in the double layer regions of the
cyclic voltammograms. Thus we conclude that the SO4^ which is adsorbed
even in the hydrogen region is not affected by the addition of the Iii'.
The effects of the addition of Cl to the 11 2 s04 solution were also
studied. Again quite dramatic changes were found upon the addition of
the Cl	 }loth the hydrogen and ox ygen regions were affected indicating
that the Cl - has the ability to displace some of the adsorbed %0 4m and
hence change the cyclic voltammogram drastically. The actual effects
of the Cl on the kinetics of 0 2 evolution are now understudy.
A comparison of solutions of IIF	 and I1 2 SO4 of equal pH was made.
According to Frumkin et	 al.	 (4) a 0..L4 N 1IF	 and 0.04 N H 2 SOIf have the same
-4-
pH. These solutions were made and the cyclic voltnmmograms on Pt were
run. The results Are Shown in Figure 5. Here it is seen that the
begavlor of Pt in these two solutions is dramatically different. In
the it 2 So4 the initiation of the oxide growth is At a higher potential
than in the HF solution evidently due to the adsorption of So o . Again
the four peak pattern is found in the hydrogen region in the 112504
solution where as in the 11F solution a pattern with onl y three peaks
is found and these not being very well defined. These data again indicate
that the So4^ plays n strong part in the development in the pattern in
the hydrogen region in the cyclic voltammogram. 	 I
2. Development of the LU D-Auger-Thin-Laver Electrochemical System
The development of a rationale basis for clectrocatalvsis requires
information concerning the composition and geometric structure of the
surface. In an effort to understand the contribution the atomic strut-
ture makes to electrocatalysis we are combining an electrochemical thin
layer cell with an ultra-high vacuum system containing a LEER-Auger
spectrometer. The Auger technique identifies the elemental composition
on the surface as well as giving the relevant information on the valency
states, LLED gives the geometric ordering in the surface with will
allow its to relate the surface structure to catalysis.
•	 The progreG, in he assembly of the entire system has been held up
because the components (valves and feedthrougl,$) which have been on order
now for some six months have not been delivered. however, during this
interim we have constructed a thin layer electrochemical cell nnt'. have
begun obtaining data with it. T}-.e particular thin layer cell which we
expect to utilize in conjunction Ath the LEED-Auger system has been
designed and is in the process of being; built in the machine shcp.
The techniques involved in using a thin layer cell require sonic experience
and we are at present developing these techniques.
I	 i
I
OR16IIo AL Y 
A(7,F, "6
OF YOM QUNLf1Y
The sample transfer mechanism fur introducing the electrodes into the vacuum
system as well as in transferring them from the :ample preparation ehamber
to the I,FED- Auger chamber has been designed and built and is shown schematically
In Figure 6. Our transfer system will maintain the electrodes at temperatures
near liquid nitrogen temperature (100K) during the transfer.
The reaction chamber and the associated ion and titanium sublimation
•
pump: have been assembled in the laboratory and pumped down to a pressure of
9 x 10-9 torr. Some difficulty has been experienced in obtaining n lower 'iacuum
with this system. We believe this is due to a contamination L,d appropriate
step: hay ._ Leen taken to alleviate this problem.
?. Preparation and Examination of Sampler, for Electrocatalytic LEED-Auger Studies
Rutheniusn oxids- (RuO2 ) supported on a titanium substrate which was found
to be one of the more effective electrocatalysts in the earlier phases of this
NASA-supported research continues to be of great interest. In order to develop
techniques for sample preparation which are critical for the IEED studies and
to obtain experience in the utilization of the instrumentation, preliminary
i
LEED-Auger experiments have been undertaken on the gas phase oxidation of single
Y	 crystal ruthenium metal.
`Tlie Ru single crystal has been oriented to ± 112 degree of the 1120 dir-
ection, cut, polished and mowited in the LEED-Auger system. After some pre-
liminary cleaning (heating to 600 0C), the Auger spectrum shown in Figure 7
was obtained. Nc LEED pattern could be obtained from this surface. After
heating the sample to 1000 0 C and extensive argon ion bombardment, the Auger
spectra characteristic of the clean Ru surface as shown in Figure Bb can be
obtained. Further removal of sulfur is achieved by heating to 1200 0C and can
be seen by comparing Figure as and 3b. The LEED pattern for the clean 1120
Ru surface has been obtained and is shown sclematically in Figure 9a. If this
-6-
clean surface is than exposed to oxygen at a pressure of 8 x 10 -9
 torr, the
I.EED pattern shown schematically 	 Figure 9b develops. If the oxygen pressure
Is increased these new spots disappear and the original clean surf a ce spots
become decreased in intensity.
In order to develop reference Auger spectra for comparinor, to the RuO2
catalysts, the single crystal surface has been oxidized in 10 -5 torr 02 at
x+50°C and then observed using Auger. The 
MvNJ415N14.5 
Ru Auger line for the
oxide shows a shift of about 1 eV from the same line for R,i ma rl. Th1ss rtiop rva-
tion agrees with the data which we obtained previously using x-ray photoelectron
spectroscopy ( XI'S) (5 ) .
A second sample which is being prepared is a gold single crystal. This
material, which is much softer than Ru, cannot be mechanically polished but
must be electropo?ished. 1'he polishing of this sample has proven to be quite
dif,.'cult and only one rtcceptable sample has been prepared.
IV. PROJECTUD WORK
Research during the ip-coming six months will include the following:
1. Electrochemical characterization of catalysts.
The work on the e_'fects of cation and anion addition to the electrolyte
.^	 on the kinetics of 02 evolution will be continued and the effects in basic
solution will also be studied.
We plan to continue the work on RuO2 single crystals. This will be
possible because we have obtained access to the correct type of furnace for
growing the single crystals.
2. Structural studies of electrocatalysts.
During the up-coming period, we plan to finish the Ru oxidation experiments
including the LEM arid Auger characterization.
I
4.
-7-
The electrochemical portion of the 1.l:ED-Auger-thin laver electrochemical
system nhuulO be completed by September. I roll • lnnry experiments utilizing
thin complete Ryntem should be cinder way shortly thereafter.
V. PROJECT PLRSOT11:1,
Jerry 1lunng, Graduate Student
•	 William 1:. O'Grady, Postdoctoral Research Assoclate
Ernest Yenger, Professor of Chemistry, Project Director
•	 UFF;RYNCES
1. Scmi-Annual Status Report 1 1 5, 1 April 1974 to 30 September 1974,
Catnlyrts for Eltcfrochemical Generation of Oxygen, W. O'Grady and
E. Yeager, 1IASA-Ames Grant No. l7GR 36-027-050.
2. B. E. Conway, It. Angerstein-Kozlowsl:a, W. B. A. Sharp And E. E.
Criddle, Anal. Chem., 45. 1331 (1973).
3. 1t. Angerstcin-Yozlowska, 33. E. Conway And W. K. A. Sharp, J. 1:lectroanal.
Chem., 43, 9 (1973).
4. D. 1. Poblovchenko, N. A. Fpshtein and A. N. Fruml:in, J. Electroanal.
Chem, 53, 95 (1974).
5. Semi-Annual Status Report #4, 1 October 1973 to 31 March 1974,
•	 Catalvsts for Electrochemical Generation of Oxygen, W. O'Grady And
E. Yeager, NASA-Mies Grant No. IMR 36-027-050.
-H-
Ln
0 0 0 0 0 0
( zlzz)/wa ) Ul st:4a ,11:agmo
.-7
HE
-«•:.ter- w r'T , T--•-•-T'^
fir._. .....T. ^.._ _.__^.... -	 •- - _.__ __^. ^_. _^_.._ _.-...,_ -... _
i
CD
CD
I
I
v^
N
L ! Co2
N
roN
a
v
u .
^ w
^x
u p
♦J .J
w G
O N
r u
N
tz
^7 U
.-r
^O, 
W
u
u a
O ;^
4?
u 
ti4 U
-4 •-i
u
U O
N
♦-1
r
L -.-
•
^II
	
t
Ln
A
CD
1
a
^I
U
N
F+
Lo
n
O
N1d O
N -4
IN X
u :s
v R.
r--1
N CJ
u
a ^
44 O
O Nu
u
^W
o
u0 U
u a v
r+	 u
o > u
e; K^
^ h
u o
.14 0
.-+ r-1 c3
o z
N
0i
N
a
u
k.
-9-
CD
^f	 N	 N
O O p O O O
( zt33 /%r'l )	 rt::a Wrt^ ^tn^
-10-
-^-.-►_ - n_. -T..?^ : r-- Tom ..._, ^1_ .^^^ ^2^
;-Z-; •	 '
__. _ _
-^=^--^ -^^"r .	 ,	 . +rt ._. ice-._ -._ _^:
I 7^t
L4-i
- r-.-- t - L
-.^__. .. Yr
N
U O
41
a ^+
a	 ;^
a
N ;:
a1 O
3
a
,b u u
4! O
O N
IJ
N U
14
Y. O
w
C^ a U
N N '[1
H ^4	 'bO ;a-
>
 1 d
LIB `^
ON
-4-4 O
r- r1 rl	 NQ U	 ,..
U O f.
14
a
H
:J
•.4
W
•
1
i
I
^o
,, vs
^ u wX aN 
t0
^— W G
h X r
1^ 4
N
r..c
u u
o 's
C)
	
aj
u o s=H G
W tZ ti+
O ^+
U
(v C N o c^
O G vl0
O M+ OO O
O.^ CL u +• c
4-1
C
V
C ^
O
U
o iO
10
-11-
0	 0	 0	 O	 O	 O
N
	 ^	 ^	 r^	 ^
(H-pd'^osn n I011u010d
u
F.
44
O
N
E^
H
w0
Hh
.+ u
o N7 1
U
v/
.--1 O
u ^
u
w
U U
N 'J
	
{- 1	 1
4^ N O
	
O ► .	 (n
r. ^..^ x
o c,
N N
rJ O O
E:
C) cy .—+ N
v1
u
N
M
G+
I	 '
—12—
E _•-^--^•=_ - - -
	
-^___ -^^^
TT
 -
	
.may_ , t ^ ^ _ •--	 ^_^ .1_• _f
-- ^^ i
t=.
Til
N N
 co0 0	 0 0	 CD 0
( zulz)/Vuz )	 ^I,I ^t1:^c[
	 :Lt1^i23f1^
 -4-
rl_lty
O
II
.
-13-
cr --
U Y
H U
40	 Z
V)	 -Jv
	
U
w	 aa 'o	 ^U
	 Qo	 w
Q	 2^	 mON	
5	 O
`	 U	 C-
1	 w z
J
r
id
w ur
w ,J
J ^i
\cr
7_	 wJ	 O	 liJ LL
1-	
CL Z
w	 cr	 n
CL
^1I 
O
	
cr O
tLj
I
I
J
lil	 lit
_J t11
0.
^Q 1 O
? `^ a
O N QN
a
U \
4
2
2
CD
D z
V) O
N
}
s
, 
,
x
-c
zO
rr
U =j
w V
w
U
w
H
z ^
O 
to
a
7 2 +_
a 7
U 0.4
Y
U
OJ	 O
rr	
-W 	 Qf-	 .J
z a
N
zp N
G l7
U
O
l^	
C
7
tL
Z
Q
a w
w o}cr0
awe
J F- F--
' Z U
D W
= O J
I- U w
N
ro
,-1
G
A-
E;
N
d
GU
1A
w
t^la
a,
^ E•
o^
W
O N
C Y l^
ti-1 r-1
^ r
^a v
^a t'
u
u .sr
v-1 U
N O
^7 N
Ai
ci u
X u
^a u
v
N
7
tC
w
i^
dN(E)
d 
i
Ru+ C
r
—14-
100	 200	 300
ENERGY (r--v)
Figure 7. Auger spectrum of a partially cleaned Ru
(1170) surface (heated to 600° C).
I100	 200	 300
ENERGY (Ev)
a
d N(E)
d 
V ^•
u
u• •
w o 0N O "
" r4 r,
to 0 0
r. u u0
IN 'v v
.4 u u
u u
a x .r
cs
^v ^o
10 r.r
u M r
r.
u u u
u u u
"41
a.
U M W
N O O
N •.^
u
u c c
c 0 0
N tz L:
C)
LL
O n n
co
d
N
LC
v1
^r
(a)
1
(b)
O o O
X X X
X X X
O O O
(b)
-16-
0	 0	 0
(a)
o	 0	 0
Figure 9. Schematic I1-ET) Patterns of Ru (1120)
a) ::can surface corre::ponding to the Auger
spectrum shorn in Fissure fib.
b) Initial oxidation of the clean Ru (1120)
surface x's indicate new spots.	 E


Catalysts for electrochemical generation of oxygen

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server