Electrooxidation of ethylene glycol and glycerol by platinum-based binary and ternary nano-structured catalysts

Article abstract of DOI:10.1016/j.electacta.2012.01.096

Spray pyrolysis of metal precursors was used to synthesize binary and ternary nano-structured Pt-based catalysts. Characterization of the catalysts was performed using SEM, TEM, and EDS to determine morphology, purity and composition. The electrochemical performance of synthesized Pt ₈₄Ru₁₆, Pt₉₆Sn₄, and Pt ₈₈Ru₆Sn₆ was evaluated via cyclic voltammetry and steady state polarization for oxidation of ethylene glycol and glycerol. The binary Pt₈₄Ru₁₆ and Pt₉₆Sn₄ catalysts had higher maximum currents and better stability than a templated Pt catalyst and templated ternary Pt₈₈Ru₆Sn₆ catalyst. All binary and ternary catalysts had less adsorbed reaction products during potential cycling than the templated platinum electrocatalyst. In situ infrared reflection absorption spectroscopy (IRRAS) analysis showed complete oxidation of ethylene glycol and glycerol with the binary and ternary catalysts by CO₂ generation. This work emphasizes the benefits provided by adding Ru and Sn to Pt catalysts for oxidation of complex alcohols.

Full text of DOI:10.1016/j.electacta.2012.01.096

Electrochimica Acta 66 (2012) 295–301
Contents lists available at SciVerse ScienceDirect
Electrochimica Acta
journal homepage: www.elsevier.com/locate/electacta
Electrooxidation of ethylene glycol and glycerol by platinum-based binary and
ternary nano-structured catalysts
Akinbayowa Falase, Michelle Main, Kristen Garcia, Alexey Serov, Carolin Lau, Plamen Atanassov∗
Chemical & Nuclear Engineering Department, UNM Center for Emerging Energy Technologies, University of New Mexico, Albuquerque, NM 87131, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Spray pyrolysis of metal precursors was used to synthesize binary and ternary nano-structured Pt-based
catalysts. Characterization of the catalysts was performed using SEM, TEM, and EDS to determine mor-
phology, purity and composition. The electrochemical performance of synthesized Pt84Ru16, Pt96Sn4, and
Pt88Ru6Sn6 was evaluated via cyclic voltammetry and steady state polarization for oxidation of ethylene
glycol and glycerol. The binary Pt84Ru16 and Pt96Sn4 catalysts had higher maximum currents and better
stability than a templated Pt catalyst and templated ternary Pt88Ru6Sn6 catalyst. All binary and ternary
catalysts had less adsorbed reaction products during potential cycling than the templated platinum
electrocatalyst. In situ infrared reflection absorption spectroscopy (IRRAS) analysis showed complete
oxidation of ethylene glycol and glycerol with the binary and ternary catalysts by CO2 generation. This
work emphasizes the benefits provided by adding Ru and Sn to Pt catalysts for oxidation of complex
alcohols.
Received 20 October 2011
Received in revised form 27 January 2012
Accepted 27 January 2012
Available online 4 February 2012
Keywords:
Electrocatalytic oxidations
Ethylene glycol
Glycerol
Fuel cells
Ternary catalyst
© 2012 Elsevier Ltd. All rights reserved.
1. Introduction
and cathode, and has thus been gaining interest in the literature
[7–15].
Ethylene glycol and glycerol have attracted interest in recent
years as fuels for direct alcohol fuel cells (DAFCs). These fuels are
advantageous compared to methanol due to their low toxicity,
renewability from biomass, cost, and high energy density. Various
groups have studied the reaction kinetics and feasibility of DAFCs
based on these fuels in acid and alkaline media. Using an alco-
hol reduction catalyst synthesis process, Neto et al. showed that
electrooxidation of ethylene glycol starts at lower potentials and
current values increase with increasing ruthenium content, with
similar effects with a PtSn/C catalyst [1]. Overall they discovered
that PtSn/C electrocatalysts are better for ethylene glycol oxida-
tion than PtRu/C catalysts due to oxidation at lower potentials
and higher current values. Livshits, Peled and coworkers demon-
strated the feasibility of a direct ethylene glycol fuel cell (DEGFC)
by building a 10-cell stack with good performance in acid media
with a nanoporous proton conducting membrane [2–5]. Chetty and
Scott noted superior performance by a PtRuW ternary electrocat-
alyst compared to PtRu binary, and PtRuNi and PtRuPd ternary
alloys [6]. While many of the reports concerning the feasibility
of these fuel cells have dealt mostly with acid electrolytes, alka-
line media presents many unique advantages for electrochemical
reactions such as improvements in reaction kinetics at the anode
Oxidation of these fuels in alkaline media is advantageous not
only due to the improved kinetics of the reaction, and higher con-
versions [16,17]. The general reaction for oxidation of ethylene
glycol and glycerol can be described by Eq. (1).
Cx≥2HyOz + (2x − z)H2O → xCO + (4x + y − 2z)H+ + (4x + y − 2z)e−
(1)
The reactions required for complete oxidation of ethylene gly-
col involves the liberation of 10 electrons while that of glycerol
involve 14 electrons. Harvesting the maximum number of elec-
trons is of utmost importance to utilize the fuel fully. Unfortunately,
the complex oxidation reactions generate intermediates that can
adsorb to and block the active sites of the catalyst, decreasing
performance. Tin and ruthenium have been described in the lit-
erature as beneficial modifiers of platinum catalysts for biomass
oxidation by helping to improve catalytic activity and decrease
adsorbed oxidation intermediates [18–27]. Most reports discuss a
bifunctional mechanism where the added metal provides oxygen
species to aid in the removal of adsorbed CO and other incomplete
oxidation products in acid and alkaline media. Coupling the ben-
efits of an alkaline environment with the stability and reactivity
improvements gained by using binary and possibly ternary cata-
lysts presents a system in which the degree of fuel oxidation is
maximized and catalyst poisoning is minimized.
∗
Corresponding author. Tel.: +1 505 277 2640; fax: +1 505 277 5433.
E-mail address: plamen@unm.edu (P. Atanassov).
0013-4686/$ – see front matter © 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.electacta.2012.01.096

296
A. Falase et al. / Electrochimica Acta 66 (2012) 295–301
We have synthesized, characterized, and electrochemically
(International Center for Diffraction Data) PDF4 data-base (rev.
2009) for phase identification. Various catalyst compositions were
synthesized and screened based on reports of similar catalysts in
the literature. The best performing catalysts in each group are pre-
sented.
evaluated binary Pt84Ru16, and Pt96Sn4 catalysts, along with a
ternary Pt88Ru6Sn6 catalyst. The catalysts were synthesized using
a spray pyrolysis approach that allows us to produce a nano-
structured catalyst by etching away the monodisperse silica
template [19,28,29]. This results in an “open frame” catalyst pos-
sessing improved transport and kinetic properties. Electrochemical
characterization by cyclic voltammetry and steady state polariza-
tion revealed the performance improvements gained by alloying
platinum with ruthenium and tin. We use infrared reflection
absorption spectroscopy (IRRAS) to gain insight into the reaction
kinetics on the surface and monitor oxidation products.
2.3. Electrochemical and in situ infrared characterization
A 5 ␮L aliquot of a 3 mg/mL catalyst ink composed of 5 wt.%
Nafion, and de-ionized water with isopropyl alcohol in a 4:1 ratio
was deposited on polished glassy carbon electrodes with a 5 mm
outer diameter for a final catalyst loading of 76 ␮g/cm2. The elec-
trodes were allowed to air dry for 30 min.
Cyclic voltammetry was conducted in 1.0 M KOH at room tem-
perature. When required, glycerol and ethylene glycol were added
to the electrolyte to make 0.1 M solutions. A Pt mesh and Hg/HgO
electrode [XR-440 Radiometer Analytical SAS] were used as counter
and reference electrodes, respectively. Before each experiment, the
electrolyte solution was deoxygenated by bubbling N2 gas for at
least 15 min. Polarization curves were constructed by averaging the
last 10% of points (90 points) during each 15-min step in potentio-
static mode with step increments of 25 mV. All potentials in this
discussion are referred to the reversible hydrogen electrode (RHE)
scale.
In situ infrared reflection adsorption spectroscopy (IRRAS)
experiments were performed at room temperature with a Nicolet
6700 FT-IR spectrometer equipped with a Mercury Cadmium Tel-
luride (MCT) detector cooled with liquid nitrogen. Experimental
setup is described previously [30–32]. For each spectra, 128 inter-
ferograms were added together to each spectrum at a resolution
of 8 cm−1 with unpolarized light. Absorbance units of the spectra
are defined as A = −log(R/R0), where R and R0 represent reflected
IR intensities corresponding to the sample and reference single
beam spectrum, respectively. Thus, a positive peak in the resulting
spectrum indicates a production of species, while a negative peak
indicates consumption or decrease in concentration of a species
compared to the reference spectrum. The reference spectrum was
collected at 0.140 V (RHE) vs. an Ag/AgCl reference electrode in
1.5 mL of 0.1 M respective fuel (ethylene glycol or glycerol) and
0.1 M KOH, using linear sweep voltammetry with a scan rate of
1 mV/s from 0.140 V to 1.18 V (RHE). A thin layer of ink was pipetted
onto a polished glassy carbon electrode with a diameter of 5 mm. A
ZnSe hemisphere was used as the IR window, and the working elec-
trode was pressed against the window, creating a thin solution layer
with a thickness of a few micrometers. The incident angle of the IR
radiation passing through the ZnSe window was 36◦ [30]. Argon
was used to purge the electrolyte while dry air was used to purge
the spectrometer and chamber, reducing the spectral interference
from CO2 and water vapor.
2. Experimental
2.1. Preparation of binary and ternary electrocatalysts via spray
pyrolysis
Synthesis of templated nanostructured binary and ternary Pt
alloys and a templated nanostructured Pt catalyst was achieved
using spray pyrolysis. This procedure has been described pre-
viously, but we have performed the catalyst synthesis with
modifications to the precursor material and reduction temper-
ature [19,29]. Calculated amounts of platinum (IV) chloride,
ruthenium (III) chloride hydrate, and/or tin (II) chloride hydrate
[Sigma–Aldrich Co.], with 20 nm monodisperse Ludox® TM50 col-
loidal silica [Sigma–Aldrich Co.] were mixed as a precursor solution
in 30 mL of de-ionized water. Concentrated hydrochloric acid was
added drop-wise while stirring until the precursors dissolved. The
dissolved precursor solution was atomized and dried through a fur-
nace at 125 ◦C using N2 as the carrier gas. A standard humidifier was
modified in order to expose the ultrasonic membrane. The catalyst
precursor solution was then positioned on top of the membrane in
order to generate the aerosol. All catalysts were made as 20 wt.%
catalyst on silica template.
Pyrolyzed particles were collected on 0.2 ␮m filter paper, and
alloys were formed by reduction of the oxide powders under 5% H2
in N2 at 500 ◦C for 2 h with a ramp rate of 1 ◦C/min and at a total
gas flow rate of 100 mL/min. The silica template was then etched in
a 7 M KOH solution for 72 h. Afterwards, the solution was filtered
and washed 3× with DI water to remove the KOH. The collected
catalyst was then dried in an oven at 80 ◦C.
2.2. Physical characterization
Following reduction and etching the silica template from the
catalysts, morphology, purity, and composition of the synthesized
powders were determined using scanning electron microscopy
(SEM), transmission electron microscopy (TEM), and energy dis-
persion spectroscopy (EDS). SEM and TEM provided information on
the morphology of the bulk and individual particles of the catalysts
while EDS was used to determine the composition of the samples
and compare to the starting solution.
3. Results and discussion
3.1. Characterization of electrocatalysts
Surface areas were measured by the N2-BET method using a
Micrometrics 2360 Gemini Analyzer. Scanning electron microscopy
(SEM) was performed using a Hitachi S-5200 Nano SEM with an
accelerating voltage of 10 keV. Transmission electron microscopy
(TEM) was performed using a JEOL 2010 instrument with an
accelerating voltage of 200 keV. Powdered samples were analyzed
by X-ray diffraction (XRD) using a Scintag Pad V diffractometer
(Bragg-Brentano geometry) with DataScan 4 software (from MDI,
Inc.) for system automation and data collection. Cu KR radiation
(40 kV, 35 mA) was used with a Bicron Scintillation detector (with
a pyrolitic graphite curved crystal monochromator). Data were ana-
lyzed with Match! 1.11 Software (Crystal Impact) using the ICDD
Spray pyrolysis of templated catalysts is a powerful synthesis
tool due to the degree of control granted over the final catalyst
composition due to each individual aerosol droplet having the same
composition as the precursor solution. SEM micrographs show the
droplet and porous “sponge-like” morphology (Fig. 1A and B), as
expected from the templating procedure. The removal of the silica
nanoparticles leaves pores in the catalytic structure that increases
catalyst utilization, even though the surface area is lower than
catalysts supported on high surface area materials such as car-
bon. Catalyst compositions and BET surface area are described in
Table 1.

A. Falase et al. / Electrochimica Acta 66 (2012) 295–301
297
Fig. 1. SEM and TEM micrographs of Pt88Ru6Sn6 catalyst. Images of the unetched (A) and etched (B) catalyst show the droplet-like morphology of each individual catalyst
particle. The templated morphology extends through the interior of the particle as shown in the SEM (B) and TEM (C and D) micrographs. The high resolution image (D,
insert) shows lattice fringes from the Pt, Ru, and Sn catalyst.
TEM micrographs show the void spaces in the pores of the
catalyst as well as the individual grains of the catalytic particles
(Fig. 1C, D, D insert). Grain sizes of the particles were 5–15 nm.
Catalyst morphology, particle size and distribution are depen-
dent on synthesis procedures. The spray pyrolysis procedure can
be performed with an atomizer, producing particles with a nar-
rower size distribution than those produced here with a modified
humidifier serving as the aerosol generator [33,34].
XRD patterns of the synthesized Pt, PtRu, PtSn, and PtRuSn
catalysts are shown in Fig. 2. Phase planes of the platinum appear
at the corresponding angles from (1 1 1), (2 0 0), (2 2 0), (3 1 1), and
(2 2 2) phases. There were no diffraction peaks associated with
separated ruthenium, tin or their oxide species detected from the
XRD measurements. The peaks are shifted slightly compared to
one another possibly due to incorporation or ruthenium or tin
into the platinum crystal lattice. The nanostructured Pt catalyst is
also slightly shifted from the dashed lines, but this could be due to
the instrument itself because no impurities were detected by EDS
during SEM or TEM analysis.
Table 1
Pt based nanostructured catalyst compositions and surface areas.
Catalyst name
Expected
composition
Composition
( 2)
BET surface
area (m2/g)
Pt(nanostructured)
Pt84Ru16
Pt96Sn4
100
85:15
95:5
100
84:16
96:4
27
27
27
33
Fig. 2. XRD diffraction patterns of synthesized nanostructured Pt and Pt based cat-
alysts over the scan range of 2–90◦ (35–90◦ shown for clarity). The dashed lines
represent the typical diffraction angles of the fcc phase of Pt.
Pt88Ru6Sn6
90:5:5
88:6:6

298
A. Falase et al. / Electrochimica Acta 66 (2012) 295–301
3.2. Electrochemical studies of binary and ternary catalysts for
ethylene glycol and glycerol oxidation
The synthesized binary and ternary catalysts were tested as
electrocatalysts for the anodic oxidation of ethylene glycol and
were compared to a synthesized spray pyrolyzed nanostructured
platinum catalyst. Cyclic voltammetry was used to evaluate the per-
formance of the electrocatalysts for the oxidation of each fuel. The
catalysts were cycled through the potential range multiple times
until a steady state value was reached (cycle 4 for all catalysts pre-
sented here). The performance of each catalyst is presented in Fig. 3.
The voltammograms exhibit expected behavior previously
described regarding oxidation of these fuels in alkaline media
[35,36]. There are two oxidation peaks in the forward scan direc-
tion and one in the reverse direction. The singular anodic peak in
the negative sweep represents oxidation of incompletely oxidized
carbonaceous intermediates on the surface of the catalysts left over
from the positive sweep [37,38]. Accumulation of these adsorbed
products block active sites on the catalyst, decreasing performance.
Roquet et al. speculated that since the first oxidation wave of glyc-
erol occurs in the platinum oxidation region, glycerol oxidation
requires the presence of adsorbed hydroxyls on the surface [39].
They also speculated that because the forward and reverse sweep
oxidative curves are not aligned, there is a limiting rate of glycerol
adsorption on the reduced platinum surface. Since the profiles for
ethylene glycol and glycerol oxidation are similar, we believe that
this explanation is suitable for oxidation of both fuels.
The recorded current is normalized to the BET surface area
(Table 1) of the catalysts in order to determine metal utilization.
In terms of maximum peak current, the binary Pt84Ru16 cata-
lyst showed enhanced oxidation behavior for both ethylene glycol
oxidation and glycerol oxidation (Fig. 3), followed by the nanos-
tructured Pt. The Pt96Sn4 had higher oxidative currents than the
Pt88Ru6Sn6 catalyst, but both performed worse than the Pt84Ru16
and nanostructured Pt catalysts. When oxidizing ethylene gly-
col, the nanostructured Pt catalyst exhibits 3 distinct features.
There is a shoulder at 0.704 V, the peak at 0.747 V, and a softer
shoulder at 0.826 V. Possible shoulders for the binary and the
broad oxidative peaks that they exhibit obscure ternary catalysts.
Although glycerol has more electrons to transfer during complete
oxidation, more maximum current is achieved while oxidizing
ethylene glycol compared to glycerol due to a less complex oxida-
tive pathway.A summary of the catalyst performance is given
in Table 2. The catalysts were evaluated in terms of their onset
potential, the peak potentials, current densities, and the ratio of
forward anodic peak to reverse peak current. The trend of the onset
potential for ethylene glycol oxidation was PtRu > PtSn > Pt (nanos-
tructured) > PtRuSn (in terms of greatest performance; meaning
lowest onset potential) while for glycerol oxidation the trend was
PtRu > PtSn > PtRuSn > Pt (nanostructured). For both fuels the binary
catalysts had the lowest onset potentials.The binary PtRu catalyst
Fig. 3. Cyclic voltammograms of Pt, Pt84Ru16, Pt96Sn4, and Pt88Ru6Sn6 catalysts vs.
ethylene glycol (A) and glycerol (B). Each catalyst was cycled until a steady state
was reached at 10 mV/s in 1.0 M KOH electrolyte with 0.1 M ethylene glycol and
glycerol, respectively. The current density was calculated with respect to the BET
surface area.
had the lowest oxidative peak potential, and the highest current
for both ethylene glycol and glycerol oxidation. For both fuels,
the ternary PtRuSn electrocatalyst performed poorly compared
to the binary and nanostructured Pt catalyst. From these results
it seems that alloying platinum specifically with both ruthenium
and tin simultaneously as a ternary catalyst is not beneficial in
terms of achieving the maximum current compared to binary PtRu
and PtSn catalysts. The binary and ternary electrocatalysts have
Table 2
Comparison of catalyst performance for ethylene glycol and glycerol electrooxidation.
Catalyst
Eonset (V)
EF (V)
IF (␮A/cm2
)
ER (V)
IR (␮A/cm2
)
BET
IF/IR
BET
Ethylene glycol
Pt(nanostructured)
Pt84Ru16
Pt96Sn4
Pt88Ru6Sn6
Glycerol
0.36
0.29
0.35
0.38
0.76
0.72
0.78
0.80
1718.52
2109.55
1408.29
1260.27
0.69
0.69
0.67
0.64
1117.47
1271.58
691.21
295.05
1.54
1.66
2.04
4.27
Pt(nanostructured)
Pt84Ru16
Pt96Sn4
0.40
0.33
0.34
0.36
0.79
0.85
0.85
0.82
1245.21
1568.50
1044.91
862.79
0.68
0.65
0.67
0.64
514.86
542.41
378.80
183.30
2.42
2.89
2.76
4.71
Pt88Ru6Sn6
Eonset: onset potential (vs. RHE); EF, IF: peak potential and current density, respectively, of main oxidation peak at 10 mV/s (vs. RHE); ER, IR: peak potential and current density,
respectively, of reverse oxidation peak at 10 mV/s (vs. RHE); IF/IR: ratio of forward main and reverse oxidation peak current density.

A. Falase et al. / Electrochimica Acta 66 (2012) 295–301
299
Table 3
Infrared frequencies observed by in situ FTIR spectroscopy of oxidation products
formed during EG and Gly electrooxidation.
Wavenumber (cm−1
)
Assignment
1004
1071
Alcohol CH2-OH stretch [44]
Aldehyde stretch (glyoxal, glycolate, glyceraldehyde)
[36,42–44]
1094
Alcohol stretching [44]
1111
CH-OH stretch [44]
1236
1303
1320
1353
∼1405
1445, 1548, 1630
1574
C-O stretch of glycolate [45]
Symmetric −OOC COO−, glyceraldehyde [42,46]
Symmetric COO− stretch of glycolate, oxalate [43,45]
Adsorbed carbonylate [45]
2−
Carbonate CO3 [42,45]
Carboxylate groups [47]
Asymmetric −OOC COO− [42]
∼1589
H O H deformation of adsorbed water, asymmetric
COO− stretch of glyoxal, glycolate, glyoxylate [43]
Carbonyl and carboxyl stretches [47]
Carboxyl stretching [47]
∼1665
1723
2343
CO2 asymmetric stretch
as PtRu > PtSn> Pt (nanostructured) > PtRuSn at potentials higher
than 0.51 V.
3.3. IRRAS characterization of ethylene glycol and glycerol
oxidation
The oxidation pathway of ethylene glycol has been described
previously [41,42]. This reaction scheme consists of a complex
parallel 2-electron steps oxidation mechanism first from ethylene
glycol to glycolaldehyde. The molecule is then oxidized to either
glyoxal or glycolic acid, then to glycoxylic acid followed by oxalic
acid and then finally CO2. It is worth noting that oxalic acid is in
the [A2−] deprotonated state due to its relatively low pKa values of
1.38 and 4.28.
Infrared spectroscopy was used to elucidate the ethylene gly-
col electrooxidation reaction mechanism on the binary and ternary
catalysts. Each spectrum was recorded in 0.1 M potassium hydrox-
ide solution with 0.1 M of ethylene glycol or glycerol. Some major
band frequencies are summarized in Table 3 for ethylene glycol
and glycerol oxidation. Glycolaldehyde is not present in the table
due to dimerization in neutral media that is further complicated in
alkaline solution [43] (Fig. 5).
Fig. 4. Steady-state polarization curves of Pt84Ru16, Pt88Ru6Sn6, and Pt96Sn4 cat-
alysts vs. ethylene glycol (top) and glycerol (bottom). 1.0 M KOH electrolyte with
0.1 M ethylene glycol and glycerol, respectively. The current density was calculated
with respect to the BET surface area.
The oxidation pathway and kinetics as shown via infrared spec-
tra for ethylene glycol oxidation are very similar for the binary and
higher IF/IR ratios than the nanostructured Pt catalyst, signaling
that accumulation of oxidation residues during the catalytic pro-
cesses is less than on the pure Pt catalyst and similar catalysts
reported in acidic media [40]. The ternary catalyst had the high-
est IF/IR ratio, suggesting that the effects of the modifier tin and
ruthenium atoms help to prevent buildup of oxidation products on
the platinum active sites, even though its oxidative performance
lacked that of binary and nanostructured Pt catalysts.Steady-state
polarization curves of ethylene glycol and glycerol oxidation on
the catalyst were obtained under potentiostatic conditions (Fig. 4).
Maximum currents for the PtRu catalyst were higher than the PtRu
and PtRuSn catalysts for both ethylene glycol and glycerol oxida-
tion. For ethylene glycol electrooxidation, the maximum current
achieved by the PtRu catalyst was twice that of the PtSn, 3.2 times
that of the nanostructured platinum catalyst and 6 times that of the
ternary PtRuSn catalyst following a trend of PtRu > PtSn > Pt (nanos-
tructured) > PtRuSn. Similar performance was seen with glycerol.
The maximum current for the PtRu electrocatalyst was 1.2 times
higher than the PtSn, 1.77 times that of the platinum, and 3.7
times higher than the PtRuSn. At potentials lower than 0.51 V, the
Pt catalyst has a higher current than the binary PtSn catalyst, but
at higher potentials the PtSn catalyst outperforms the Pt catalyst.
The trend for catalyst performance during glycerol oxidation trends
ternary catalysts. The peaks for alcohol stretching at 1000 cm−1
,
aldehyde stretching at 1070 cm−1 indicative of glyoxal and gly-
colate species, symmetric COO− stretching at 1320 cm−1, and
asymmetric −OOC COO− stretching at 1574 cm−1 indicate the
presence of glyoxal and glycolate at 0.5 V for the PtRu catalyst, and
0.61 V for the PtSn and PtRuSn catalyst. Asymmetric COO− stretch-
ing along with water deformation results in a very strong peak at
1589 cm−1. Carbonate formation at 1405 cm−1 begins between 0.4
and 0.5 V, and increases up to 0.6 V where it seems to remain steady
or decrease as Demarconnay et al. observed [45]. A small peak
due to bridge bonded CO species at 1856 and 1813 cm−1 with the
much smaller corresponding linear CO peak at 2000 cm−1 appears
at 0.28 V for the PtSn and PtRuSn catalysts, and at 0.61 V for the
PtRu catalyst [48,49]. These peaks grow slightly in intensity as the
electrode becomes more polarized. As the reaction progresses, CO2
begins to form at 0.73 V for the PtRu catalyst [45], and 0.84 V for
the PtSn and PtRuSn catalysts. Production of a carboxylic acid evi-
dent by absorbance bands at 1723 cm−1 1236 cm−1 and 1095 cm−1
is enhanced on the Pt84Ru16 catalyst at high (1.18 V) potentials
compared to the PtSn and PtRuSn catalyst.
The electrooxidation pathway of glycerol has been described
recently in alkaline media. Kwon et al. used high performance liquid

300
A. Falase et al. / Electrochimica Acta 66 (2012) 295–301
Fig. 5. IRRAS spectra of ethylene glycol (A–C) and glycerol (D–F) oxidation on binary and ternary Pt-based catalysts. 1 mV/s scan rate in 0.1 M KOH and 0.1 M fuel.
Absorbance bands at 1070 cm−1 corresponding to aldehydes
appear at 0.61 V and grow in intensity as the potential increases.
As with ethylene glycol, a strong peak at 1589 cm−1 results from
the water stretching and carboxylic acids that absorb at the same
wavelength. A small peak due to bridge bonded CO species at 1856
and 1813 cm−1 with the even smaller corresponding linear CO
peak at 2000 cm−1 appears at 0.28 V and grows slightly in intensity
as the electrode becomes more polarized. CO2 formation begins at
0.84 V for all three catalysts.
chromatography coupled with online electrochemical mass spec-
troscopy to elucidate the complex oxidation reaction scheme on
gold and platinum catalysts [16]. They found high concentrations
of glyceraldehyde to be the first oxidation product at 0.4 V, followed
by glyceric acid. Dihydroxyacetone, hydroxypyruvic acid, glycolic
acid, formic acid, oxalic acid, and tartronic acid were detected at
low concentrations.
The oxidation reaction pathway of glycerol on the binary and
ternary Pt based catalysts was similar amongst the catalysts.

A. Falase et al. / Electrochimica Acta 66 (2012) 295–301
301
4. Conclusions
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and ternary templated catalysts synthesized by spray pyrolysis. The
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the composition of the as-created catalysts. The catalysts had an
open frame sponge like morphology caused by template removal
via etching of the silica catalyst. Cyclic voltammetry and steady
state polarization showed that the binary Pt84Ru16 had both higher
oxidative currents and better catalytic stability vs. nanostructured
platinum, binary PtSn, and ternary PtRuSn catalysts. The ratio of for-
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accumulation of oxidation products on the catalyst surface is not as
significant as it is for reactions using similar catalysts in acid media.
The addition of both ruthenium and tin modifiers to platinum cat-
alysts is not beneficial for maximum current generation, as seen in
the cyclic voltammetry and steady state polarization experiments,
but adsorption of reaction intermediates that can block the elec-
trode and decrease performance is lower on the ternary catalysts
than the binary PtRu, PtSn and nanostructured Pt catalyst. Both the
binary and ternary electrocatalysts are capable of complete oxida-
tion of both ethylene glycol and glycerol via the presence of CO2 as
shown by in situ IRRAS. This work demonstrates the complimentary
effect of Ru and Sn modifiers in a binary platinum based catalyst
to achieve higher catalyst performance for the electrooxidation of
ethylene glycol and glycerol.
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Acknowledgments
The authors would like to thank Dr. Andrew De La Riva for assis-
tance with the TEM images, and Dr. Barr Halevi, Eric Peterson, and
Dr. Rosalba Rincon for assistance in obtaining XRD data. Work was
supported in part by the DOE EPSCoR NM Implementation Award.
Akinbayowa Falase is thankful for support from the Louis Stokes
Alliance for Minority Participation (LSAMP) Bridge to the Doctorate
VII HRD #0832947 program.
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