Hydrogenation of Ru(1,5-cyclooctadiene)(η3-C3H5)2 over black platinum. A low-temperature reactive deposition of submonolayer quantities of ruthenium atoms on platinum with real time control over surface stoichiometry

Article abstract of DOI:10.1021/ja963163p

Black Pt effected the hydrogenation of Ru(COD)(η³-C₃H₅)₂ (1; COD is 1,5-cyclooctadiene) by dihydrogen gas (pressure ~ 1 atm) at -10 °C in hexanes. The hydrogenation resulted in adsorption of Ru adatoms by the surface of Pt with concomitant formation of propane, cyclooctane, and small amounts of cis-bicyclo[3.3.0]octane and n-octane. Compound 1 did not react with dihydrogen gas under these conditions in the absence of Pt. The total amount of cyclooctane, bicyclo[3.3.0]octane, and n-octane in solution was equal to the amount of 1 consumed at all stages of the hydrogenation. The lifetimes of the organic fragments on the surface were short on the time scale of the hydrogenation. It was therefore possible to observe in real time both the stoichiometry and the activity of the evolving Ru-Pt surface by monitoring the concentrations of either 1 or the C₈ product hydrocarbons in solution. There was a kinetic burst during the initial stages of the hydrogenation that ended after deposition of 0.2-0.5 equiv of Ru versus Pt(surface) (Pt(surface) is an active site on black Pt). The rate decreased after the burst and then increased as more Ru was deposited on Pt to reach a maximum, constant rate after deposition of 1.5-1.8 equiv of Ru. Cyclic voltammograms recorded in 1.0 M H₂SO₄ of the bare surface, of the surface after adsorption of a monolayer of carbon monoxide, and of the surface in the presence of methanol showed that coverage of Pt by Ru was essentially complete after the maximum, constant rate was achieved during hydrogenation of 1. The surface area of a Ru surface resulting from hydrogenation of 2.7 equiv of 1 was 67% that of the original Pt surface according to the charge associated with oxidation of an adsorbed monolayer of carbon monoxide. Anodic stripping of Ru showed that the total of C₈ hydrocarbon products in solution after hydrogenation of 1 equaled the amount of Ru deposited on Pt. A catalyst surface resulting from hydrogenation of 0.11 equiv of 1 was up to ~ 14 times more active than bare Pt for the potentiodynamic oxidation of methanol ([MeOH] = 1.0 M, [H₂SO₄] = 0.5 M, 40 °C, sweep rate 5 mV/s). A catalyst surface resulting from hydrogenation of 0.33 equiv of 1 oxidized methanol potentiostatically at 0.158 V (vs SCE, [MeOH] = 0.5 M, [H₂SO₄] = 0.5 M, 25 °C) for 45 min with ~ 13 times the activity of Pt under the same conditions. A catalyst surface resulting from deposition of 0.8 equiv of Ru oxidized methanol potentiostatically at 0.256 V (vs SCE) under the above conditions for a total of 1.5 h with negligible dissolution of Ru into the electrolyte.

Full text of DOI:10.1021/ja963163p

J. Am. Chem. Soc. 1997, 119, 3543-3549
3543
Hydrogenation of Ru(1,5-cyclooctadiene)(η3-C3H5)2 over Black
Platinum. A Low-Temperature Reactive Deposition of
Submonolayer Quantities of Ruthenium Atoms on Platinum
with Real Time Control over Surface Stoichiometry
Christopher E. Lee, Paul B. Tiege, Yue Xing, Jayan Nagendran, and
Steven H. Bergens*
Contribution from the Department of Chemistry, UniVersity of Alberta,
Edmonton, Alberta T6G 2G2, Canada
ReceiVed September 9, 1996. ReVised Manuscript ReceiVed January 2, 1997X
Abstract: Black Pt effected the hydrogenation of Ru(COD)(η3-C3H5)2 (1; COD is 1,5-cyclooctadiene) by dihydrogen
gas (pressure ∼1 atm) at -10 °C in hexanes. The hydrogenation resulted in adsorption of Ru adatoms by the
surface of Pt with concomitant formation of propane, cyclooctane, and small amounts of cis-bicyclo[3.3.0]octane
and n-octane. Compound 1 did not react with dihydrogen gas under these conditions in the absence of Pt. The total
amount of cyclooctane, bicyclo[3.3.0]octane, and n-octane in solution was equal to the amount of 1 consumed at all
stages of the hydrogenation. The lifetimes of the organic fragments on the surface were short on the time scale of
the hydrogenation. It was therefore possible to observe in real time both the stoichiometry and the activity of the
evolving Ru-Pt surface by monitoring the concentrations of either 1 or the C8 product hydrocarbons in solution.
There was a kinetic burst during the initial stages of the hydrogenation that ended after deposition of 0.2-0.5 equiv
of Ru versus Ptsurface (Ptsurface is an active site on black Pt). The rate decreased after the burst and then increased as
more Ru was deposited on Pt to reach a maximum, constant rate after deposition of 1.5-1.8 equiv of Ru. Cyclic
voltammograms recorded in 1.0 M H2SO4 of the bare surface, of the surface after adsorption of a monolayer of
carbon monoxide, and of the surface in the presence of methanol showed that coverage of Pt by Ru was essentially
complete after the maximum, constant rate was achieved during hydrogenation of 1. The surface area of a Ru
surface resulting from hydrogenation of 2.7 equiv of 1 was 67% that of the original Pt surface according to the
charge associated with oxidation of an adsorbed monolayer of carbon monoxide. Anodic stripping of Ru showed
that the total of C8 hydrocarbon products in solution after hydrogenation of 1 equaled the amount of Ru deposited
on Pt. A catalyst surface resulting from hydrogenation of 0.11 equiv of 1 was up to ∼14 times more active than
bare Pt for the potentiodynamic oxidation of methanol ([MeOH] ) 1.0 M, [H2SO4] ) 0.5 M, 40 °C, sweep rate 5
mV/s). A catalyst surface resulting from hydrogenation of 0.33 equiv of 1 oxidized methanol potentiostatically at
0.158 V (vs SCE, [MeOH] ) 0.5 M, [H2SO4] ) 0.5 M, 25 °C) for 45 min with ∼13 times the activity of Pt under
the same conditions. A catalyst surface resulting from deposition of 0.8 equiv of Ru oxidized methanol
potentiostatically at 0.256 V (vs SCE) under the above conditions for a total of 1.5 h with negligible dissolution of
Ru into the electrolyte.
Introduction
growth, surface segregation during high-temperature stages of
the synthesis (e.g., during reductions of precursors and during
This paper describes the hydrogenation of (COD)Ru(η3-
C3H5)2 (1; COD is 1,5-cyclooctadiene) by dihydrogen gas in
hexanes solution over black Pt. The major objective of this
work was to deposit controlled submonolayer or multilayer
quantities of Ru adatoms on Pt metal using a chemical reaction
between a dissolved ruthenium hydrocarbonyl compound and
the Pt surface. Bimetallic clusters of Ru and Pt have been used
to catalyze the hydrogenation of arenes,1 the hydrogenolysis of
propane,1 the hydrogenation of carbon monoxide,2 and the
electrochemical oxidation of methanol in fuel cells.3 Ru-Pt
metallic clusters are typically prepared by chemical or electro-
chemical reduction of Ru and Pt compounds (e.g., chlorides,
oxides, hydroxides, and amines) in the presence of a support.3q-x,4
As is the case with most preparations of bimetallic clusters, the
surface compositions and oxidation states of the resulting
clusters are often ambiguous. Sources of ambiguity include
variations in the rates of mass transport to the sites of cluster
(3) (a) Radmilovic, V.; Gasteiger, H. A.; Ross, P. N., Jr. J. Catal. 1995,
154, 98. (b) Frelink, T.; Visscher, W.; van Veen, J. A. R. Surf. Sci. 1995,
335, 353. (c) Frelink, T.; Visscher, W.; Cox, A. P.; van Veen, J. A. R.
Electrochim. Acta 1995, 40, 1537. (d) Rauhe, B. R., Jr.; McLarnon, F. R.;
Cairns, E. J. J. Electrochem. Soc. 1995, 142, 1073. (e) Laborde, H.; Leger,
J-M.; Lamy, C. J. Appl. Electrochem. 1994, 24, 1019. (f) Gasteiger, H. A.;
Markovic, N.; Ross, P. N., Jr.; Cairns, E. J. J. Electrochem. Soc. 1994,
141, 1795. (g) Gasteiger, H. A.; Markovic, N.; Ross, P. N., Jr.; Cairns, E.
J. J. Phys. Chem. 1993, 97, 12020. (h) Herrero, E.; Franaszczuk, K.;
Wiecskowski, A. J. Electroanal. Chem. 1993, 361, 269. (i) Hable, C. T.;
Wrighton, M. S. Langmuir 1993, 9, 3284. (j) Meli, G.; Leger, J-M.; Lamy,
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Electroanal. Chem. 1990, 283, 271. (m) Goodenough, J. B.; Hamnett, A.,
Kennedy, B. J.; Manoharan, R.; Weeks, S. A. J. Electroanal. Chem. 1988,
240, 133. (n) Hughes, V. B.; Miles, R. J. Electroanal. Chem. 1983, 145,
87. (o) Beden, B.; Kadirigan, F; Lamy, C.; Leger, J. M. J. Electroanal.
Chem. 1981, 127, 75. (p) Janssen, M. M. P.; Moolhuysen, J. Electrochim.
Acta 1976, 21, 869. (q) Surampudi, S.; Narayanan, S. R.; Vamos, E.; Frank,
H.; Halpert, G.; LaConti, A.; Kosek, J.; Surya Prakash, G. K.; Olah, G. A.
J. Power Sources 1994, 47, 377. (r) Hogarth, M. P.; Munk, J.; Shukula, A.
K.; Hamnett, A. J. Appl. Electrochem. 1994, 24, 85. (s) Wasmus, S.;
Vielstich, W. J. Appl. Electrochem. 1993, 23, 120. (t) Swathirajan, S.; Mik-
hail, Y. M. J. Electrochem. Soc. 1991, 138, 1321. (u) Aramata, A.; Masuda,
M. J. Electrochem. Soc. 1991, 138, 1949. (v) Iwasita, T.; Nart, F. C.;
Vielstich, W. Ber. Bunsen-Ges. Phys. Chem. 1990, 94, 1030. (w) McNicol,
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* To whom correspondence should be addressed. Voicemail: (403)-492-
9703. Fax: (403)-492-8231. E-mail: Steve.Bergens@UAlberta.CA.
X Abstract published in AdVance ACS Abstracts, March 15, 1997.
(1) Miura, H.; Taguchi, H.; Sugiyama, K.; Matsuda, T.; Gonzalez, R.
D. J. Catal. 1990, 124, 194.
(2) Miura, H.; Gonzalez, R. D. J. Catal. 1982, 74, 216.
S0002-7863(96)03163-0 CCC: $14.00 © 1997 American Chemical Society

3544 J. Am. Chem. Soc., Vol. 119, No. 15, 1997
Lee et al.
electrode pressing), interactions with the support, and dissolution
of Ru during pretreatment by potential cycling.3a,4a,f,h,p,5 The
method now used to synthesize bimetallic clusters that provides
the most control over surface composition involves a two-step
process in which a hydrocarbonyl compound of one of the
metals is deposited on a support containing metal clusters of
the other metal.6 The hydrocarbonyl compound is then reduced
by dihydrogen gas at elevated temperatures.1,7 Control over
the surface composition of several types of bimetallic clusters
has been achieved by adjusting the ratio of the amount of
hydrocarbonyl originally introduced to the system to the number
of active sites on the clusters of the other metal (limiting-reagent
control). In contrast with limiting-reagent control, our approach
was to develop a clean deposition reaction that allowed for
monitoring the extent of deposition in situ, and that could be
interrupted when the desired surface stoichiometry was achieved
(reaction-rate control).
Results and Discussion
General Methods. Compound 1 was prepared as described
in the literature9 and sublimed immediately before use. This
compound has the attractive features that it can be prepared in
pure form and that it contains no components (halide ions,
phosphines, carbonyls, heteroatoms) that might act as catalyst
poisons. We used a blacked Pt gauze as substrate.10 The
surface area of the black Pt was determined from the Coulombic
charge in the cathodic hydride region of cyclic voltammograms
recorded in a 1.0 M aqueous solution of H2SO4 under argon.11
We then used the following procedure to transfer the gauze from
the aqueous acid electrolyte to the vessel in which the
hydrogenation was carried out. First, the surface of the gauze
was protected as oxides by holding the potential at 1.2 V (all
potentials in this paper are reported relative to the saturated
calomel electrode (SCE)) for 2 min. Second, the gauze was
raised above the electrolyte and rinsed with purified water under
argon. Third, while protected by drops of purified water,12 the
gauze was quickly transferred through air to the hydrogenation
vessel. Fourth, the gauze was dried under a stream of argon
and then placed under an atmosphere of dihydrogen gas to
reduce the surface oxides to hydrides. The gauze was then
immersed in dihydrogen-saturated hexanes at the desired
reaction temperature. The reaction mixture was rapidly stirred
(800 rpm), and a continuous stream of dihydrogen gas (∼10
mL/min) was bubbled through the solution during the hydro-
genation to ensure that mass transfer of dihydrogen to the surface
of the gauze was not rate limiting (reaction-rate-limiting
conditions rather than mass-transport-limiting conditions).8 To
determine if significant changes in surface area occurred during
these manipulations, a control experiment was performed in
which the above procedure was repeated in the absence of 1.
After being immersed in a blank hexanes solution under
dihydrogen gas for a typical time of reaction, the Pt gauze was
lifted above the hexanes under dihydrogen gas in the hydroge-
nation vessel, the hexanes were removed by cannula from the
vessel, and the gauze was dried under a stream of dihydrogen
gas. Protected under several drops of purified water, the gauze
was quickly transferred through air to an electrochemical cell
containing a 1.0 M solution of H2SO4 in water under argon,
and the surface area was determined again using cyclic
voltammetry. Little change (a decrease by ∼6%) in the surface
area of the black Pt had occurred during these manipulations.
Hydrogenation of 1. To begin a hydrogenation, a solution
of 1 and a decane internal standard dissolved in hexanes were
quickly and quantitatively transferred to the reactor under
dihydrogen. Aliquots were removed at timed intervals. The
aliquots were analyzed by gas chromatography (GC) and the
concentrations of product hydrocarbons were determined, and
by the UV-vis absorbance of the solution and the decrease in
concentration of 1 was determined. Since the products of the
hydrogenation were alkanes and Ru(0) adsorbed on the surface
of Pt, the only component of the hydrogenation mixture with a
significant UV-vis absorbance was 1. Control experiments13
showed that reaction between 1 and dihydrogen gas did not
occur under these conditions in the absence of Pt.
In 1988, Whitesides et al. reported that (diolefin)dialkylplati-
num(II) complexes were reduced by dihydrogen gas over Pt
black to generate the corresponding alkanes and Pt(0) that was
incorporated onto the surface of Pt black.8 We now disclose
that hydrogenation of 1 in hexanes by dihydrogen gas was also
effected by black Pt, and that the hydrogenation resulted in
adsorption of Ru adatoms by the surface of Pt (eq 1).
(4) (a) Shibli, S. M. A.; Noel, M. J. Power Sources 1993, 45, 139. (b)
Zou, W.; Gonzalez, R. D. J. Catal. 1992, 133, 202. (c) Wang, S.; Fedkiw,
P. S. J. Electrochem. Soc. 1992, 139, 2519. (d) Machida, K.; Fukuoka, A.;
Ichikawa, M.; Enyo, M. J. Electrochem. Soc. 1991, 138, 1958. (e) Hamnett,
A.; Weeks, A. A.; Kennedy, B. J.; Troughton, G.; Christensen, P. A. Ber.
Bunsen-Ges. Phys. Chem. 1990, 94, 1014. (f) Alerasool, S.; Gonzalez, R.
D. J. Catal. 1990, 124, 204. (g) Kunimatsu, K. Ber. Bunsen-Ges. Phys.
Chem. 1990, 94, 1025. (h) Alerasool, S.; Boecker, D.; Rejai, B.; Gonzalez,
R. D.; Del Angel, G.; Azomosa, M.; Gomez, R. Langmuir 1988, 4, 1083.
(i) Watanabe, M.; Uchida, M.; Motoo, S. J. Electroanal. Chem. 1987, 229,
395. (j) Furuya, N.; Motoo, S. J. Electroanal. Chem. 1984, 179, 303. (k)
Miura, H.; Gonzalez, R. D. J. Catal. 1982, 74, 216. (l) McNicol B. D. J.
Electroanal. Chem. 1981, 118, 71. (m) Ross, P. N.; Kinoshita, K.;
Scarpellino, A. J.; Stonehart, P. J. Electroanal. Chem. 1975, 63, 97. (n)
Harubumi, E. Jpn. Kokai Tokkyo Koho JP 04,118,860 [92,118,860]; Chem.
Abstr. 117:115219. (o) Del Angel, G.; Alerasool, S.; Dominguez, J. M.;
Gonzalez, R. D.; Gomez, R. Surf. Sci. 1989, 224, 407. (p) Miura, H.; Suzuki,
T.; Ushikubo, Y; Sugiyama, K.; Matsuda, T.; Gonzalez, R. D. J. Catal.
1984, 85, 331.
(5) (a) Hadzi-Jordanov, S.; Angerstein-Kozlowska, H.; Vukovic, M.;
Conway, J. J. Electrochem. Soc. 1978, 125, 1471. (b) Kotz, R.; Stucki, S.
J. Electrochem. Soc. 1984, 172, 211. (c) Vukovic, M. J. Chem. Soc.,
Faraday Trans. 1990, 86, 3743. (d) Entine, V. S.; Petrii, O. A. Elek-
trokhimiya 1968, 4, 678. (e) Beden, B.; Kadirgan, F.; Lamy, C.; Leger, J.
M. J. Electroanal. Chem. 1981, 127, 75.
(6) Either the hydrocarbonyl compound of the second metal is phys-
isorbed on the support and migrates to the metal clusters of the first metal
during the reduction by dihydrogen,1 or the hydrocarbonyl is grafted onto
the surface of the first metal before reduction by dihydrogen. The latter
process is called surface organometallic chemistry.7
(7) (a) Lesage, P.; Clause, O.; Moral, P.; Didillon, B.; Candy, J. P.;
Basset, J.M. J. Catal. 1995, 155, 238. (b) Candy, J. P.; Didillon, B.; Smith,
E. L.; Shay, T. B.; Basset, J. M. J. Mol. Catal. 1994, 86, 179. (c) Didillon,
B.; Houtman, C.; Shay, T.; Candy, J. P.; Basset, J. M. J. Am. Chem. Soc.
1993, 115, 9381. (d) Basset, J. M.; Candy, J. P.; Choplin, A.; Santini, C.;
Theolier, A. Catal. Today 1989, 6, 1. (e) Agnelli, M.; Louessard, P.; El
Mansour, A.; Candy, J. P.; Bournonville, J. P.; Basset, J. M. Catal. Today
1989, 6, 63.
(8) Miller, T. M.; Izumi, A. N.; Shih, Y. S.; Whitesides, G. M. J. Am.
Chem. Soc. 1988, 110, 3146. Miller, T. M.; McCarthy, T. J. Whitesides,
G. M. J. Am. Chem. Soc. 1988, 110, 3156. Miller, T. M.; Whitesides, G.
M. J. Am. Chem. Soc. 1988, 110, 3164.
(9) Albert, M. O.; Singleton, E.; Yates, J. E. Inorg. Synth. 1989, 26,
249.
(10) A shiny 52 mesh platinum gauze was connected to a platinum wire
that was sealed to a uranium glass tube. The gauze was blacked as described
in DiCosimo, R.; Whitesides, G. M. J. Phys. Chem. 1989, 93, 768.
(11) Woods, R. Electroanal. Chem. Interfacial. Electrochem. 1974, 49,
217.
(12) Use of prepurified water to protect platinum surfaces during transfer
in air is an established technique often used in electrochemistry with
platinum electrodes. See: Clavilier, J.; Faure, R.; Guinet, G. Durand, R. J.
Electroanal. Chem. 1980, 107, 205.
1
(13) Monitored by GC and by H NMR spectroscopy.

Hydrogenation of Ru(1,5-cyclooctadiene)(η3-C3H5)2
J. Am. Chem. Soc., Vol. 119, No. 15, 1997 3545
Figure 1. Number of equivalents of Ru adatoms deposited on Pt by
hydrogenation of 1 versus time for reactions carried out at 20 and -10
°C. The number of equivalents of Ru was determined from the total
amount of C8 product hydrocarbons in solution.
Figure 2. Number of equivalents of 1 consumed and total number of
equivalents C8 hydrocarbon products produced in solution versus time
for a hydrogenation of 1 carried out at -10 °C.
adsorbed by the Pt surface by monitoring either the concentration
of 1 or the total concentration of C8 hydrocarbon products in
solution.
The nature of the hydrocarbon products (as determined by
gas chromatography-mass spectrometry) from the hydrogena-
tion of 1 depended on the reaction temperature. Propane,14
cyclooctane (89% of C8 products), cis-bicyclo[3.3.0]octane (8%
of C8 products), and n-octane (3% of C8 products) were
produced at room temperature. Free COD in solution was not
detected. Propane, cyclooctane (95% of C8 products), and cis-
bicyclo[3.3.0]octane (5% of C8 products) were produced at -10
°C. The ratio of C8 products did not change within experimental
error over the course of the hydrogenation. The absence of
n-octane at -10 °C indicated that its formation proceeded via
a higher energy pathway than hydrogenation of 1.
Figure 1 shows plots of the number of equivalents of Ru
adatoms (based on hydrocarbon products in solution) adsorbed
by Pt versus time for hydrogenations carried out at 20 °C and
-10 °C. The number of equivalents of Ru is relative to the
initial number of sites on black Pt, and it was assumed to equal
the total number of equivalents of cyclooctane, cis-bicyclo[3.3.0]-
octane, and n-octane in each aliquot as determined by GC.
There was a kinetic burst during the initial stages of the
hydrogenations carried out at -10 °C that ended after deposition
of 0.2-0.5 equiv of Ru. The size of the burst varied among Pt
samples. The rate of hydrogenation slowed after the burst, and
then increased as more Ru was deposited on Pt to reach a
maximum, constant rate after deposition of 1.5-1.8 equiv of
Ru. This rate remained constant until 1 was depleted from
solution.
Figure 2 shows a plot of consumption of 1 and total
production of all C8 product hydrocarbons (cyclooctane and cis-
bicyclo[3.3.0]octane) in solution between hydrogenation of 0
and ∼1.8 equiv 1 at -10 °C, when submonolayer quantities of
Ru adatoms were adsorbed by the surface of Pt. The rates of
consumption of 1 and of formation of C8 hydrocarbons were
the same within experimental certainty. The decrease in 1 and
the increase in C8 hydrocarbons in solution were also the same
within experimental certainty at all stages of the hydrogenation.
Since there was no observable time lag between consumption
of 1 and the formation of C8 hydrocarbons in solution, we
conclude that the lifetimes of the surface hydrocarbonyls were
short on the time scale of the hydrogenation. It was therefore
possible to observe in real time the number of Ru adatoms
As the lifetimes of the surface hydrocarbonyls appear short
on the time scale of the hydrogenation, the curves in Figures 1
and 2 show the actual evolution of the surface’s activity toward
hydrogenation of 1 as the coverage of Pt by Ru increased.
Kinetic bursts similar to those observed during low-temperature
hydrogenations of 1 (Figures 1 and 2) were also observed by
Whitesides et al. during low-temperature hydrogenations of
(COD)Pt(Me)2 over Pt black carried out under reaction-rate-
limiting conditions.8 We believe the bursts during hydrogena-
tion of 1 resulted from a proportion of the active sites on Pt
being substantially more active than the others, and that these
highly active sites reacted quickly during the initial stages of
the hydrogenation. An alternative interpretation is that the initial
burst was caused by the surface being saturated with dihydrogen
at the beginning of the hydrogenation, and that the decrease in
rate after the burst resulted from limitations in mass transport
of dihydrogen to the surface. We do not feel that mass transport
of dihydrogen limited the rate of hydrogenation after the initial
burst because the rate of reaction increased as more Ru was
deposited on Pt.
The increase in rate after the burst indicated that Ru was more
active than Pt toward hydrogenation of 1. We believe that the
rate increased until all the active sites on Pt were covered by
Ru. To investigate this possibility, we interrupted hydrogena-
tions after the maximum, constant rate was achieved and
analyzed the resulting surfaces using cyclic voltammetry.
Characterization of the Ru Surface. We interrupted
hydrogenations after the desired number of equivalents of Ru
was deposited on Pt (as determined by GC or by UV-vis
absorbance) by quickly lifting the gauze above the reaction
mixture, rinsing the gauze in the reactor with cooled (-10 °C)
dihydrogen-saturated hexanes, removing the hexanes from the
reactor, and drying the gauze under a stream of dihydrogen gas.
The reactor was transferred to a glovebox, and the gauze,
protected by surface hydrides, was transferred through the
atmosphere of argon in the glovebox to an electrochemical cell.
An argon-saturated 1.0 M aqueous solution of H2SO4 was
transferred to the cell while the gauze was held above the level
of the solution, and according to procedures developed by
(14) Identified using GC but not quantified.

3546 J. Am. Chem. Soc., Vol. 119, No. 15, 1997
Lee et al.
behavior is identical to that observed by Gasteiger et al. using
a pure Ru surface.3g
We believe that, first, the nearly identical electrochemical
behaviors of the control black Ru surface and of the surfaces
resulting from hydrogenation of 2.7 and 3.5 equiv 1 and that,
second, the maximum, constant activity of the surface toward
hydrogenation of 1 indicated that the coverage of Pt by Ru was
essentially complete after adsorption of 1.5-1.8 equiv of Ru
by the surface of Pt. That more than 1 equiv of Ru was required
to cover the active sites on Pt was likely due to a combination
of factors. These factors include uncertainties in the measured
surface area of black Pt, hydrogenation occurring on the
adsorbed Ru as well as on Pt, the mobility of the Ru atoms on
the surface, the relative affinities of Ru adatoms for Ru and for
Pt, and the fact that more than 1 equiv of Ru adatoms was likely
required to cover the rough atomic morphology of black Pt.
We also note that the radius of Ru is ∼96% that of Pt.16 We
therefore use the number of equivalents of Ru in Figures 1 and
2 as an approximate measure of surface composition.
We estimated the surface area of the catalyst surface after
hydrogenation of 2.7 equiv of 1 using the charge associated
with oxidation of a monolayer of adsorbed carbon monoxide.
The measured surface area was 67% that of the black Pt before
hydrogenation of 1. Oxidation of carbon monoxide can only
be used to approximate the surface area of Ru.15,17 We therefore
propose only that major changes in surface area did not occur
during hydrogenation of 1.
Figure 3. (a) Cyclic voltammograms (sweep rate 5 mV‚s-1 in 1.0 M
H2SO4) of a catalyst surface resulting from hydrogenation of 2.7 equiv
of 1 recorded before and after adsorption of a monolayer of carbon
monoxide at -0.19 V. (b) Cyclic voltammograms of a black Ru
electrode recorded under conditions identical with those in (a). The
voltammograms in (a) and (b) are not normalized for surface area.
Composition of the Ru Deposit. We determined the amount
of Ru deposited on Pt after several hydrogenations by anodic
stripping of Ru from the resulting surfaces. Anodic stripping
was carried out in 1.0 M aqueous solution of NaOH at room
temperature using a 9 V battery as power source.18 UV-vis
spectroscopy showed that Ru in the resulting electrolyte was
mainly in the form of sodium ruthenate. The amount of Ru in
solution was determined by inductively coupled plasma spec-
trophotometry (ICP) and was found to equal the total of
cyclooctane, cis-bicyclo[3.3.0]octane, and n-octane in the
hydrogenation mixture as determined by GC. All the Ru atoms
generated by hydrogenation of 1 were therefore adsorbed by
the surface of Pt. These results, taken together with the results
of the GC-UV-vis studies shown in Figure 2 indicate that
little, if any, carbon from COD was trapped by the Ru deposit.
The chemical composition of the Ru deposit was further
investigated by hydrogenating at room temperature ∼30 equiv
of 1 over Pt black powder with an approximate dispersion of
8%.19 The molar ratio of Ru to Pt in the resulting particles
was 2.9:1 according to neutron activation analysis.
Oxidation of Methanol by Ru-Pt Surfaces. Figure 5
shows the potentiodynamic activity for oxidation of methanol
by black Pt and by a black Ru-Pt catalyst resulting from
interrupting a hydrogenation of 1 after deposition of 0.11 equiv
of Ru. The onset of oxidation was ∼100 mV lower for Ru-Pt
than for Pt, and the current remained higher (by up to a factor
of ∼14) until the potential reached ∼0.65 V. This behavior is
similar to those of the bulk alloys of Ru-Pt studied by Gasteiger
et al. for which the surface compositions were precisely
known.3g The activity of the Ru-Pt surface noticeably de-
Figure 4. Cyclic voltammograms (sweep rate 5 mV‚s-1, [H2SO4] )
0.5 M, [MeOH] ) 0.5 M, 25 °C) of a catalyst surface generated by
hydrogenation of 3.5 equiv of 1.
Gasteiger et al.,3g the potential of the gauze was set to -0.19
V concurrent with immersion of the gauze into the electrolyte.
We analyzed a surface resulting from hydrogenation of 2.7
equiv of 1 by recording voltammograms before and after
adsorption of a monolayer of carbon monoxide. The voltam-
mograms were compared to those of a control black Ru surface
prepared by electrochemical deposition of excess Ru on a black
Pt gauze. As described by other workers, the carbon monoxide
was adsorbed at -0.19 V before initiating the potential sweeps.15
These workers showed using bulk Ru-Pt alloys that the
potential of the anodic wave for oxidation of adsorbed carbon
monoxide depended on the ratio of Ru and Pt atoms at the
surface.15 Figure 3 shows the cyclic voltammograms. The
voltammograms of the control black Ru surface and the surface
resulting from hydrogenation of 2.7 equiv of 1 were quite similar
both in shape and in peak positions before and after adsorption
of the carbon monoxide. To further characterize the surface
after the maximum, constant rate was achieved during hydro-
genation of 1, voltammograms were recorded in an aqueous
solution of H2SO4 and MeOH of a surface resulting from
hydrogenation of 3.5 equiv of 1. Figure 4 shows the resulting
voltammograms. Neither was there adsorption of methanol, nor
were there appreciable oxidation currents below 0.46 V. This
(16) The metallic radii of platium and ruthenium are 139 and 134 pm,
respectively. See: Tables of Physical and Chemical Constants, 15th ed.;
Kaye, G. W. C., Laby, T. H., Eds.; Longman Inc: New York, 1986.
(17) (a) Kinoshita, K.; Ross, P. N. J. Electroanal. Chem. 1977, 78, 313.
(b) Bett, J.; Kinoshita, K.; Routis, K.; Stonehart, P. J. Catal. 1973, 29,
160.
(18) For a related procedure see: Connick, R. E.; Hurley, R. J. Am. Chem.
Soc. 1952, 74, 5012.
(15) (a) Gasteiger, H. A.; Markovic, N.; Ross, P. N., Jr.; Cairns, E. J. J.
Phys. Chem. 1994, 98, 617. (b) Richarz, F.; Wohlmann, B.; Vogel, U.;
Hoffschulz, Wandelt, K. Surf. Sci. 1995, 335, 361.
(19) We used Johnson Matthey, fuel-cell grade Pt black as substrate for
these experiments. The surface area is reported to be 25 m2/g.

Hydrogenation of Ru(1,5-cyclooctadiene)(η3-C3H5)2
J. Am. Chem. Soc., Vol. 119, No. 15, 1997 3547
from poisoning of the catalyst surface by carbon monoxide or
COH.3g,20-22 For both the Ru-Pt and the Pt catalysts, the
current generated by the poisoned surfaces decreased slightly
over the course of the oxidations. The current generated by
the poisoned Ru-Pt surface remained higher than that of the
Pt surface by a factor of ∼13, indicating that surfaces resulting
from deposition of submonolayer quantities of Ru on Pt by
hydrogenation of 1 are appreciably durable under these condi-
tions.
To determine if dissolution of Ru into the electrolyte occurred
under these conditions, we carried out a potentiostatic oxidation
of methanol at 0.256 V (a higher potential than the previous
potentiostatic oxidation) first for 0.5 h, and then for an additional
1 h using a Ru-Pt catalyst surface generated by hydrogenation
of 0.8 equiv of 1. Analysis using ICP showed only traces of
Ru ions in the electrolyte after the first 0.5 h. The signal was
too small to accurately quantify, but roughly corresponded to
0.06% of the Ru originally on the surface. ICP analysis of the
same electrolyte after oxidation of methanol for a further 1 h
showed no change in the amount of Ru ions in solution.
Conclusions. Hydrogenation of 1 by dihydrogen gas over
Pt at -10 °C is among the lowest energy processes we are aware
of for deposition of adatoms of a foreign metal on the surface
of another metal.23 It appears to allow for the first time
generation of a prototypic kinetic bimetallic surface with real
time control over the stoichiometry and activity of the evolving
surface. We believe this system offers certain advantages over
conventional methods of deposition of metal adatoms (e.g., metal
atom evaporation and chemical vapor deposition), namely,
providing uniform coverage over all exposed sides of a rough,
blacked metal surface after adsorption of less than 2 equiv of
adatoms, allowing for deposition of submonolayer equivalents
of adatoms under reaction-rate control at low temperatures,
allowing for use of simple, bench-top equipment and techniques,
and use of a Ru precursor (1) containing no components that
may poison the resulting catalyst surface. Further, the resulting
Ru-Pt surfaces had appreciable activities and durability toward
both the potentiodynamic and the potentiostatic oxidation of
methanol under conditions that are typical for an operating fuel
cell. Since this deposition proceeded via a reaction with a metal
surface, it will in principle allow for self-directed depositions
on Pt clusters dispersed on an inert support. Finally, we propose
that the combination of Pt and Ru is not unique, and that this
methodology can be applied to a number of metal systems
provided the appropriate precursors are employed.
Figure 5. Potentiodynamic oxidation of methanol ([MeOH] ) 1.0 M,
[H2SO4] ) 0.5 M, 40 °C, sweep rate 5 mV‚s-1) by black Pt and by a
Ru-Pt catalyst surface resulting from hydrogenation of 0.11 equiv of
1. The currents are normalized to 4.1 µmol of surface atoms.
Figure 6. Potentiostatic oxidation of methanol ([MeOH] ) 0.5 M,
[H2SO4] ) 0.5 M, 25 °C) by black Pt and by a Ru-Pt catalyst surface
resulting from hydrogenation of 0.33 equiv of 1. The currents are
normalized to 4.1 µmol of surface atoms.
creased after four sweeps up to 1.0 V. Ru dissolves in sulfuric
acid solutions at potentials above ∼0.65 V,5a-c and we believe
that this decrease in activity was caused by dissolution of Ru
above this potential. Analysis (ICP) of the electrolyte for Ru
ions after six sweeps showed that ∼54% of the Ru originally
on the surface had dissolved.
Experimental Section
General Procedures. Argon (Linde, prepurified) was passed
through molecular sieves (Anachemia, activated type 4 Å) prior to use.
Dihydrogen (Linde, prepurified) and carbon monoxide (Matheson,
ultrahigh purity) were used as received. Water was deionized, distilled
from alkaline permanganate under nitrogen, and purged with argon for
To study the stability of these surfaces near the upper
operating potentials of an anode in a methanol fuel cell, we
carried out a potentiostatic oxidation of methanol at 0.158 V
for 45 min using a Ru-Pt catalyst surface resulting from
interrupting a hydrogenation of 1 after deposition of 0.33 equiv
of Ru. Figure 6 shows the variation of current with time for
the potentiostatic oxidation of methanol using both the Ru-Pt
catalyst and black Pt in aqueous solutions of H2SO4 and MeOH.
A high initial current followed by a rapid decrease to a lower,
more steady value is typical behavior for the electrochemical
oxidation of methanol using catalysts that contain Pt. It is
believed that the high initial current results from the rapid
dehydrogenation of methanol and oxidation of the resulting
surface hydrides. The loss in initial current is proposed to result
(20) Watanabe, M.; Motoo, S. Electroanal. Chem. Interfacial Electro-
chem. 1975, 60, 267.
(21) Franaszczuk, K.; Sobkowski, J. J. Electroanal. Chem. 1992, 327,
235. Wang, S.; Fedkiw, P. S. J. Electrochem. Soc. 1992, 139, 2519.
(22) Iwasita, T.; Nart, F. C.; Vielstich Ber. Bunsen-Ges. Phys. Chem.
1990, 94, 1030. Kunimatsu, K. Ber. Bunsen-Ges. Phys. Chem. 1990, 94,
1025. Wasmus, S.; Vielstich, W. J. Appl. Electrochem. 1993, 23, 120.
(23) A low-energy deposition related to hydrogenation of 1 is electroless
deposition. For examples, see: Lamouche, D.; Clechet, P.; Martin, J. R.;
Haroutiounian, E.; Sandino, J. P. I. J. Electrochem. Soc.: Solid-State Sci.
Technol. 1987, 134, 692. Baum, T. H. J. Electrochem. Soc. 1990, 137, 252.
Stremsdoerfer, G.; Martin, J. R.; Clechet, P.; Nguyen-Du. J. Electrochem.
Soc. 1990, 137, 256. Murphy, M. M.; Van herle, J.; McEvoy, A. J.; Thampi,
K. R. J. Electrochem. Soc. 1994, 141, L94. Wang, Y. F.; Pollard, R. J.
Electrochem. Soc. 1995, 142, 1712 and references cited therein. As far as
we are aware, control over submonolayer quantities of adatoms has not
been achieved with electroless deposition.

3548 J. Am. Chem. Soc., Vol. 119, No. 15, 1997
Lee et al.
30 min prior to use. Hexanes (BDH, HPLC grade) were stirred over
concentrated H2SO4 for 24 h, passed through aluminum oxide (grade
1), hydrogenated (pressure of dihydrogen 1 atm) over platinum black
for 24 h, and distilled under argon. Heptane and decane were purified
similarly. Methanol (BDH, HPLC grade) was distilled from Mg-
(OCH3)2 under argon. Diethyl ether (Calendon) was distilled from
potassium/benzophenone under argon. Cyclohexane-d12 was flash
distilled from potassium/benzophenone under argon and degassed by
three freeze-pump-thaw cycles. H2SO4 (ACS grade, BDH) was used
as received. Rubber septa were extracted for 24 h with HPLC grade
hexane in a Soxhlet extractor, and dried under vacuum. All glassware
was rinsed with a 1:5 mixture of 30% aqueous hydrogen peroxide/
concentrated H2SO4, water, a 5% mixture of ammonium hydroxide in
absolute ethanol, and ethanol and dried in an oven. (η4-1, 5-Cyclooc-
tadiene)Ru(η3-C3H5)2 (1) was prepared by a literature method9 and twice
sublimed under vacuum.
coverage, the platinum was raised above the solution, and the solution
was cannulated out of the reactor. The catalyst surface and the reactor
walls were rinsed with four 5 mL portions of hexanes, and the catalyst
was dried under a stream of dihydrogen gas for 30 min.
Control Experiments. The entire hydrogenation procedure was
repeated in the absence of 1. The surface area of the platinum as
determined using cyclic voltammetry had decreased by 6% during the
treatment by dihydrogen.
Dihydrogen (pressure ∼1 atm) was bubbled through a hexane (40
mL) solution of 1 (25 mg) for 30 min at room temperature. Analysis
of the solution by GC showed no reaction occurred. This experiment
was repeated in cyclohexane-d12 at a higher concentration (39.6 mg of
1 in 2.5 mL of solvent). Analysis by 1H NMR spectroscopy also
showed that no reaction occurred after 30 min.
Anodic Stripping of Ruthenium. The ruthenium-platinum surface
obtained by hydrogenation of 1 was transferred in air to an electro-
chemical cell that contained a Teflon-coated stirbar and a 1.0 M solution
of NaOH in argon-purged water (80 mL). The black platinum counter
electrode was fitted behind a D-porosity glass frit. The cathode (“+”
terminal) of a 9 V battery was connected to the ruthenium-platinum
electrode, and the anode (“-” terminal) was connected to the counter
electrode. The solution was stirred under argon for 10-30 min as the
color of the solution turned orange. The solution was quantitatively
transferred to a 100 mL volumetric flask and diluted to volume with
1.0 M NaOH. The amount of ruthenium in solution was determined
using ICP analysis. UV-vis spectra of the solutions indicated that
the product of the anodic stripping was sodium ruthenate.25 Further
anodic stripping in fresh electrolyte showed that all the ruthenium was
stripped from the electrode by this treatment.
Hydrogenation of 1 Over Platinum Black. In air, platinum black
(10-11 mg, Johnson Matthey, fuel cell grade) was weighed into a 3
dram, 21 × 50 mm vial containing a 4 × 14 mm Teflon-coated
magnetic stir bar and capped with a rubber septum pierced with two
steel needles used as a gas inlet and outlet. The reactor was flushed
with argon for 10 min and then placed under an atmosphere of
dihydrogen gas. Hexanes (∼3 mL) were added via cannula to a 3 dram
vial that was capped with a rubber septum and that contained freshly
sublimed 1 (42-48 mg, weighed in a drybox). The solution of 1 in
hexanes was flushed with a stream of dihydrogen gas (∼20 mL/min)
for 2 min. Hexanes (∼1 mL) were added via cannula to the reactor
containing the hydrogen-saturated platinum black, and a stream of
dihydrogen gas (∼20 mL/min) was passed through the hexanes for 1
min while the mixture was stirred at ∼400 rpm. The solution of 1 in
hexanes was transferred to the reactor with a cannula using an additional
∼2 mL of hexanes for rinses. The total volume of the solution in the
reactor was brought up 6 mL. A stream of dihydrogen (∼10 mL/min)
was passed through the reaction for the duration of the reaction. After
24 h at room temperature, the solution was drained using a cannula
and the contents of the reactor were rinsed with hexanes (three ∼5 mL
portions). The contents of the reactor were then dried at room
temperature under vacuum (∼0.01 Torr) for 2 h.
The reactor used for the hydrogenations was a 2.3 × 10.3 cm Pyrex
tube containing a 4 × 14 mm Teflon-coated magnetic stir bar and fitted
with a rubber septum pierced with a disposable pipet (used as a
dihydrogen gas inlet) and a glass tube supporting the blacked platinum
gauze.
Electrochemical experiments were performed using a Pine Bipoten-
tiostat Model AFCBP1 controlled with Pinechem 2.00 software or using
a homemade potentiostat equipped with a Hewlett-Packard 7004 chart
recorder. Inductively coupled plasma spectroscopy (ICP) was per-
formed using a Perkin-Elmer Optima equipped with an atomic emission
detector. Gas chromatography-mass spectrometry was performed
using a VG-7070E with a Varian 6000 GC fitted with a 30 m J&B
DB5 column using a MSS data system. Electrolytes were purged with
argon for at least 10 min prior to use, and electrochemical experiments
were performed under argon unless stated otherwise. The reference
electrode was an anodized silver wire behind a D-porosity glass frit,
but potentials are referred to a standard calomel electrode in the same
electrolyte. The counter electrode was a blacked platinum wire behind
a D-porosity glass frit. Gas chromatography (GC) was performed on
a Hewlett-Packard series 530 µm × 10 m methyl silicone column,
model no. 19057-121, fitted to a Hewlett-Packard 5980A gas chro-
matograph with a Hewlett-Packard 3392A integrator. 1H NMR spectra
were measured on a Bruker AM-400 NMR spectrometer operating at
400.13 MHz.
Blacked Platinum. Platinum gauze (52 mesh, 99.9%, 25 × 25 mm,
Aldrich) was threaded with platinum wire (∼200 mm in length, 0.127
mm in diameter, 99.9%, Aldrich) and supported by flame sealing the
wire leads through 3 mm uranium glass tubing. The gauze was
blacked10 and its surface area determined from the coulometric charge
of the hydrogen adsorption region in cyclic voltammograms recorded
in 1.0 M H2SO4 according to literature procedures.11 The blacked
platinum was then held at 1.2 V for 2 min, rinsed with four 2 mL
portions of purified water under argon, and quickly transferred wet
through air to the hydrogenation reactor. The blacked platinum was
dried with a stream of argon for 3 h, and exposed to a stream of
dihydrogen gas for a further 1 h to reduce the surface oxides and to
remove the resulting water.
Hydrogenation of 1 over Blacked Platinum. Dihydrogen-purged
hexanes (15 mL) were transferred via cannula to the reactor containing
the hydrogen-saturated blacked platinum, and the reactor was immersed
into the cooling bath. The blacked Pt was kept above the hexanes
until the hydrogenation was begun. A slow stream (∼10 mL/min) of
dihydrogen was passed through the solution throughout the reaction.
Freshly sublimed 1 (10-12 mg) was weighed into a small vial in a
drybox, and the vial was capped with a rubber septum. A weighed
amount of decane was added to the vial containing 1 using a 5 µL
syringe to act as an internal standard for GC analysis. The contents of
the vial were dissolved in hexanes and then quantitatively transferred
to the reactor with a cannula and with several rinses with hexanes, and
the volume of solution in the reactor was brought up to 20 mL. The
stir rate was set at 800 rpm,24 the platinum was immersed into the
reaction mixture, and timed aliquots (100-300 µL) were cannulated
from the reaction mixture. The aliquots were analyzed using GC and
UV spectrophotometry. To interrupt the hydrogenation at a desired
Neutron Activation Analysis. Samples and standards, packed in
HNO3-washed polyethylene 100 mL tubes, were individually irradiated
for 300 s at a neutron flux of 1 × 1011 n cm-2 s-1 in an inner site of
the University of Alberta SLOWPOKE II Nuclear Reactor. Following
a decay period of 18 min, each sample was counted for 300 s at a
sample-to-detector distance of 3 cm using a 34% hyperpure Ge detector
attached to an 8k channel PC-based multichannel analyzer. Analysis
was performed by the comparator method of INAA using RuCl3‚3H2O
and K2PtCl6 (98%) as standards. Platinum was quantified using the
542.96 and 185.76 keV γ-ray emissions of 199Pt (T1/2 ) 30.8 min)
produced Via the reaction 198Pt(n, g) f 199Pt while Ru was determined
using the 724.27 keV γ-ray emission of 105Ru (T1/2 ) 4.44 h) produced
Via the thermal neutron reaction 104Ru(n, g) f 105Ru.
Adsorption and Oxidation of Carbon Monoxide. A ruthenium-
platinum surface was prepared by hydrogenation of 2.7 equiv of 1.
The reaction vessel containing the rinsed and dried electrode was
transferred to a glovebox, and the electrode was transferred to the
electrochemical cell under argon. The cell was removed from the
glovebox, flushed with argon, and fitted with two disposable pipets
(24) With the aid of a calibrated strobe light.-
(25) Connick, R. E.; Hurley, C. R. J. Am. Chem. Soc. 1952, 74, 5012.

Hydrogenation of Ru(1,5-cyclooctadiene)(η3-C3H5)2
J. Am. Chem. Soc., Vol. 119, No. 15, 1997 3549
(to be used as gas inlets), with a reference electrode, and with a counter
electrode. An argon-purged solution of H2SO4 (1.0 M in water) was
transferred to the cell via a polyethylene cannula. The potential of the
ruthenium-platinum working electrode was set to -0.19 V concurrent
with immersion into the electrolyte. With stirring (700 rpm) at room
temperature, carbon monoxide was bubbled through the solution for
30 min followed by bubbling argon through the solution for 2 min.
The stirring was stopped, and the potential of the working electrode
was swept at 5 mV/s up to 0.723 V and then down to -0.262 V.
A control black ruthenium electrode was prepared by potentiostatic
deposition of ruthenium on a black platinum electrode at -0.267 V
for 15 min from a stirred solution of RuCl3‚3H2O (0.005 M) and H2-
SO4 (1.0 M) in water. Using the Coulombic charge passed during the
deposition, we calculate that 15 equiv of Ru was deposited on the
electrode surface. The electrode was rinsed with H2SO4 and transferred
quickly in air to the electrochemical cell, and the oxidation of adsorbed
carbon monoxide was repeated as described above.
was set to -0.200 V concurrent with immersion into the electrolyte
and then swept to 1.0 V at 5 mV/s while the temperature of the
electrolyte was maintained at 40 °C using a heated oil bath.
The potentiostatic oxidations of methanol were carried out similarly
at 25 °C, [H2SO4] ) 0.5 M, and [MeOH] ) 0.5 M. The potentials of
the catalyst surfaces were set to -0.17 V concurrent with immersion
into the electrolyte, and then set to the desired potential to begin the
oxidation.
Acknowledgment. This work was supported by the Natural
Sciences and Engineering Research Council of Canada and by
the University of Alberta. We also acknowledge use of the
University of Alberta SLOWPOKE II Nuclear Reactor Facility
and Dr. John Duke for the INAA determinations of the Pt and
Ru contents of the analysis. The expert assistance of Dianne
Formanski, Youbin Shao, and Professor Gary Horlick with
inductively coupled plasma spectrophotometry is sincerely
appreciated. Dr. Richard E. Russo (Advanced Laser Technolo-
gies, Berkeley) provided extremely helpful discussions and
information.
Oxidations of Methanol. A hydrogenation of 1 was interrupted as
described above after deposition of 0.11 equiv of ruthenium. The rinsed
and dried catalyst surface was transferred in a glovebox to an
electrochemical cell. An argon-purged aqueous solution (90 mL) of
H2SO4 (0.5 M) and methanol (1.0 M) at 40 °C was transferred via
cannula to the cell. The potential of the ruthenium-platinum surface
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