ISSN 20702051, Protection of Metals and Physical Chemistry of Surfaces, 2013, Vol. 49, No. 5, pp. 559–566.

© Pleiades Publishing, Ltd., 2013.

Original Russian Text © O.I. Kasian, T.V. Luk’yanenko, A.B. Velichenko, 2013, published in Fizikokhimiya Poverkhnosti i Zashchita Materialov, 2013, Vol. 49, No. 5, pp. 517–
525.

NEW SUBSTANCES,
MATERIALS, AND COATINGS

Electrochemical Properties of HeatTreated Platinized Titanium

O. I. Kasian, T. V. Luk’yanenko, and A. B. Velichenko
Ukrainian State University of Chemical Technology, pr. Gagarina 8, Dnepropetrovsk, 49600 Ukraine
email: velichenko@ukr.net
Received October 9, 2012

Abstract—The physicochemical properties and electrochemical behavior of platinized titanium anodes pro
duced by a combined electrochemical method, which involves electrodeposition of a thin platinum layer on
a titanium substrate followed by heat treatment, are studied. The process is shown to result in the appearance
of a composite coating with a substantial content of titanium oxides. The composite obtained is an ntype
semiconductor, the flatband potentials of which and the number of charge carriers depend on the prepara
tion conditions. It is proposed to use the reduction peak of oxygencontaining platinum compounds on the
stripping voltammogram as a correlation parameter for predicting the electrocatalytic activity of heattreated
Ti/Pt composite electrodes with respect to the oxygen evolution reaction.
DOI: 10.1134/S2070205113050043

INTRODUCTION of stripping voltammetry. At the first stage, the electrode

Composite materials based on oxides of titanium was polarized at an anodic current density of
and platinum group metals are widely used as catalysts, 100 mA/cm2 for 120 s. Then, a cathodic voltammo
photo and electrocatalysts, as well as in electrochemi gram was recorded at a potential scan rate of 100 mV/s.
cal synthesis of strong oxidizers, in destruction of Semiconductor properties of the electrodes were
organic and inorganic water pollutants, and as active studied by the electrodeimpedance method at an alter
layers of dimensionally stable anodes for electroplating nating current frequency of 20 Hz. Data of stripping
and hydrometallurgy [1–12]. There are different ways voltammetry and electrodeimpedance measurements
of producing materials of this kind, such as solgel were processed with the use of builtin functions of the
method, plasmochemical method, chemical deposition Mathcad 15 package [16, 17].
from solutions in the presence of reducing agents and The surface morphology of the coatings was studied
others [11–15]. Direct or combined electrochemical with the use of scanning electron microscopy (SEM)
methods should be considered to be the most promis with a REM106I raster electron microscope. Images
ing, since, due to the simplicity of the procedure and the were obtained in secondary electrons at a beam current
possibilities of smooth changes in the technological of 120 mA. The limiting residual pressure in the micro
parameters of the processes, they enable one to control scope column did not exceed 6.7 × 10–4 Pa.
the composition and properties of the materials in XPS data were obtained with a JSPM4610 ultra
broad ranges. However, the problem of direct synthesis high vacuum scanning probe microscope with a
of the materials of this kind remains open, because the transverse resolution of 0.14 nm and a longitudinal
effects of the preparation conditions on the composi resolution of 0.01 nm. The limiting residual pres
tion, physicochemical and electrochemical properties, sure in the microscope column did not exceed 3.0 ×
and electrocatalytic activity of obtained materials has 10–8 Pa. The charging of a specimen and the related
been insufficiently studied. For the above reasons, this Fermi level energy shift were corrected based on the
work aimed at solving these problems seems topical. C 1s peak position.

EXPERIMENTAL RESULTS AND DISCUSSION

Electrochemical measurements were carried out in Preparation and Physicochemical Properties
a threeelectrode cell with an auxiliary Pt grid electrode of Platinized Titanium
with the use of a PI501.1 pulse potentiostat, PR8 In order to produce composite platinized titanium
programmer, and N307/1 biaxial potentiometer or electrodes, a combined method that involves prelimi
GAMRY Potentiostat/Galvanostat/ZRA Reference nary treatment of the titanium substrate, electrodeposi
3000. All potentials are given with respect to the silver tion of a thin platinum layer, and subsequent thermal
chloride reference electrode. treatment was proposed. Before electrodeposition of
Platinum oxides, which form in a potential range of the platinum coating, the titanium substrate was treated
the oxygen evolution reaction, were studied with the use as follows:

559
560 KASIAN et al.

100 g/L NaNO2 + 20 mL NH3 solution (ρ =

0.915 g/cm3) at a cathodic current density of
20 mA/cm2 and a temperature of 343 K. The amount of
deposited platinum was 2 mg/cm2 (at a calculated
thickness of the active layer of 1 µm). Some of the pro
(а) 10 µm (b) 5 µm duced electrodes were heat treated in air in a tube fur
nace at a temperature of 503, 583, or 683 K for an hour.
Fig. 1. SEM micrographs of Ti/Pt electrodes without heat Important to note that this method affords to vary
treatment. the surface morphology and the composition of the
electrodes and, hence, their electrochemical properties
I in a broad range.
8000 10 min Coatings with a platinum content up to 2 mg/cm2
are non uniform and look like islands of platinum on
20 min titanium (Fig. 1). According to the data of energydis
7000 persive Xray spectroscopy, the surfaces of such elec
30 min trodes are composed of titanium compounds (one
third) and platinum (twothirds).
6000 45 min To determine the chemical composition of the sur
face of platinized titanium electrodes, we selected a
sample that was not subjected to heat treatment. In our
5000 opinion, this makes it possible to estimate the original
surface state of platinum and titanium on the anode surface,
that affords to find out the possible routes of the subse
528 531 534 quent chemical transformation of the electrode during
E_b(O 1s), eV its heat treatment in air or anodic polarization in an
aqueous electrolyte. The investigation was carried out
with the use of Xray photoelectron spectroscopy (XPS)
Fig. 2. XPS data (TiOx/PtOy; 2 mg/cm2 Pt): O 1s peak
depending on the duration of ionic etching. as the most informative in particular respect. The dura
tion of ionic etching with argon characterizes the
(i) sandpapering the surface with fine paper; changes in the composition of the coating in its depth
(ii) degreasing in 5 M KOH solution for 2 h at a tem from the outer surface toward the substrate. As follows
perature of 298 K; from Figs. 2–4, three elements—platinum, titanium,
and oxygen—are present in the surface layer of the
(iii) thoroughly washing in distilled water; specimen.
(iv) etching in boiling 8M HCl solution for 30 min; In the identification of the chemical state of the ele
and ments in the coating, corrected bond energies of tita
(v) thoroughly washing in distilled water. nium (Ti 2p3/2), platinum (Pt 4f7/2, and oxygen (O 1s)
Then, a thin platinum layer was plated from an alka were used. According to the data obtained (Fig. 2), tita
line bath containing [18, 19] 25.004 g/L K2PtCl4 + nium is present in both metallic and oxidized (Ti(IV))

I
I
20000
6000
surface
15000 10 min
20 min
30 min
45 min
10000
5000 surface
20 min
30 min
5000 45 min

0 4000
68 72 76 450 455 460
E_b(Pt 4f7/2), eV E_b(Ti 2p3/2), eV

Fig. 3. XPS data (TiOx/PtOy; 2 mg/cm2 Pt): Pt 4f7/2 peak Fig. 4. XPS data (TiOx/PtOy; 2 mg/cm2 Pt): Ti 2p3/2 peak
depending on the duration of ionic etching. depending on the duration of ionic etching.

PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES Vol. 49 No. 5 2013

 ELECTROCHEMICAL PROPERTIES OF HEATTREATED PLATINIZED TITANIUM 561

forms on the surface, while platinum exists chiefly as a 0.002

metal. In the case of oxygen, at least two forms, which
correspond to the bond energies of 528–529 (bound in
oxides) and 530–532 eV (hydroxides and adsorbed 0.001
water), can be distinguished. The first form probably
corresponds to titanium oxide formed under the effect

i, А/сm2
of the oxygen from the air. The hydroxide form of oxy 0
gen and adsorbed water are present on the surfaces of
most metals and oxides that were exposed to air for a
long time. Deeper in the coating, one can see no sign of –0.001
adsorbed hydrocarbons and hydroxide oxygen forms.
The existence of an O 1s peak indicates the presence of
titanium oxides at any depth in the bulk of the coating. –0.002
Upon longer ionic etching, one can identify pro 0 0.5 1.0 1.5
nounced Ti 2p3/2 peaks in two clearly distinguishable E (AgCl/Ag), V
ranges, namely, 452–455 and 458–460 eV. The former
peak corresponds to metallic titanium, including TixPty
Fig. 5. Cyclic voltammograms (100 mV/s) on platinum in
compound at 454.4 eV. The latter peak can be assigned 1 M chloric acid.
to Ti(IV) compound, namely TiO2.
The titaniumtoplatinum ratio in the depth of
the coating calculated from the XPS data is given in although the current is higher nearly by an order, which
Table 1. As follows from the results, the coating is not confirms the above supposition about the nature of the
homogeneous; and the platinum content substantially changes observed.
decreases from the outer surface toward the substrate With an increase in the temperature of treatment of
(from 92 to 67 at %), which indicates the local character Pt/Ti electrodes, the oxygen evolution current
of the coating and is in agreement with the SEM data. It increases, but the overpotential of the process remains
is quite possible that a certain amount of TixPty interme unchanged (Figs. 6a–6d). It is likely that the heat treat
tallic compound with a low platinum content is formed ment of the electrodes results in the appearance of
during platinum deposition on a titanium substrate. defects and cracks, which leads to an increase in the true
In the coatings that did not undergo heat treatment, surface area and, hence, in the activity of Ti/Pt. On all
platinum is chiefly contained in metallic form, while the electrodes considered, metallic platinum surface
titanium is present in both metallic and oxidized states. parts are electrochemically active sites, which deter
The data obtained enable us to suppose that the heat mines the constancy of the overpotential of oxygen evo
treatment, which promotes platinum diffusion both lution.
over the surface and deep in the coating, should result in
the formation of a composite material of the following Extending the potential cycling range in the anodic
general composition: PtxTiyO(1 – x – y). direction results in the formation of more strongly
bound chemisorbed oxygen and phase platinum oxides,
which leads to the increase in the peak reduction cur
Electrochemical Behavior rent and the shift in the peak potential to the negative
of Platinized Titanium Anodes values (Fig. 7).
Figure 5 shows a cyclic voltammogram of the plati In order to clarify the difference in the nature and
num electrode in 1 M HClO4. The anodic branch of the amount of platinum oxides formed in a potential range
voltammogram involves a weakly pronounced peak of of oxygen evolution on Ti/Pt electrodes, stripping vol
hydrogen desorption; a current plateau (1.0–1.3 V), tammetry with a linear potential sweep was used. Peak
which corresponds to the formation of phase platinum potential on inverse voltammograms recorded on Ti/Pt
oxides; and an exponentially ascending segment, which electrodes with a platinum content of 2 mg/cm2 is
corresponds to oxygen evolution at Е ≥ 1.3 V. The
cathodic branch of the curve involves the reduction
peak of oxygencontaining platinum compounds of Table 1. Surface contents of titanium and platinum in the
diverse nature. sample depending on the duration of etching with argon
The shapes of cyclic voltammograms recorded on Duration, min Ti, at % Pt, at %
platinized titanium electrodes resemble a curve
obtained on platinum, since the curves involve the same 0 8.15 91.85
typical segments (Fig. 6). Note that the current values 10 7.96 92.04
observed on platinized titanium are higher than those 20 10.14 89.86
on platinum (Fig. 6a), which is obviously determined by
the extended surface of a Ti/Pt electrode. At the same 30 23.83 76.17
time, the overpotential of oxygen evolution is the same, 45 32.66 67.34

PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES Vol. 49 No. 5 2013

562 KASIAN et al.

(а) (b)
0.02 0.08

i, А/сm2
i, А/сm2
0 0.04

–0.02 0
0 0.5 1.0 1.5 0 0.5 1.0 1.5
E (AgCl/Ag), V E (AgCl/Ag), V

(c) (d)
0.08 0.10
i, А/сm2

i, А/сm2
0.04
0.05

0
0

0 0.5 1.0 1.5 0 0.5 1.0 1.5

E (AgCl/Ag), V E (AgCl/Ag), V

Fig. 6. Cyclic voltammograms (100 mV/s) on platinized titanium electrodes heat treated at (a) 298, (b) 503, (c) 583 and
(d) 683 K, in 1 M chloric acid.

shifted toward the negative values with an increase in 0

solidphase diffusivity, V is the scan rate, and cred is the
the potential scan rate (Figs. 8, 9), which is typical of oxide content.
irreversible electron transfer and confirmed by the data
shown in Figs. 8b, 8c, 9b and 9c. The dependence of the The dependence of the peak potential on the loga
peak current on the square root of the potential scan rithmic scan rate is also linear (Fig. 8c), which shows
rate is linear (Figs. 8b, 9b) and obeys Delahay’s equa that the ratedetermining stage is irreversible electron
tion [20]: transfer. The peak is characterized by a Semerano crite
rion value of 0.9 (Fig. 8d), which shows that the charge
ip = 3.00 × 105 n(α nα )1 2 ADred
12 12 0
V cred, transfer process is complicated by the adsorption. Note
that, in the case of an electrode that was heat treated at
where ip is the peak current, n is the number of elec 583 K, the logi – logV dependence (Fig. 9d) has two
trons transferred in an elementary act, α is the transfer linear segments with slopes of 0.6 and 1, which also
coefficient, A is the electrode surface area, Dred is the shows that the ratedetermining stage is complicated by
the adsorption and the change in nature of the oxides
formed.
0.005 The complication of the charge transfer with the
adsorption processes on Ti/Pt electrodes with a thin
active layer is seemingly caused (by contrast to individ
ual platinum electrodes) by the existence of surface tita
0
i, А/сm2

nium dioxide formed as a result of the anodic polariza

tion or heat treatment. Probably, the formation of the
1
2
compound is confirmed by the XPS data.
–0.005 3 Let us compare inverse voltammograms recorded
4
5 on Ti/Pt electrodes that differ in temperature of treat
ment (Fig. 10). The peak current of the platinum oxide
–0.010 reduction on a Ti/Pt sample, which was not heat
0 0.5 1.0 1.5 treated, is much higher than one observed on Pt, which
E (AgCl/Ag), V is probably caused by the developed surface of plati
nized titanium. The peak potential is shifted toward the
negative values, and the peak itself is asymmetric. This
Fig. 7. Cyclic voltammograms (100 mV/s) on platinized
titanium in 1 M chloric acid in different potential scan
means that both chemisorbed and phase oxygen forms
ranges (V): (1) –0.2–1.2, (2) –0.2–1.3, (3) –0.2–1.4, of different natures are simultaneously present on the
(4) –0.2–1.5, and (5) –0.2–1.6. electrode surface and can additionally be affected by

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 ELECTROCHEMICAL PROPERTIES OF HEATTREATED PLATINIZED TITANIUM 563

(а) (b) (а) (b)

0 0 40
20
i, А/сm2

–0.01 30

Ip, mА
15

i, А/сm2
Ip, mA
–0.01
1
1 10 –0.02 2
3
20
2 4
–0.02 3
4 –0.03
5
6 10
5 5
6
0 –0.04 0
0.2 0.4 0.6 2 4 6 8 10 12 0 0.2 0.4 2 4 6 8 10 12 14 16
E (AgCl, Ag), V V1/2, (mV/s)1/2 E (AgCl, Ag), V V1/2, (mV/s)
(c) (d) 0.42

logi, А/сm2
0.42 –1.4 (c) –1.4 (d)
lgi, А/сm2

0.38 0.38
–1.8 –1.8

Ep, V
Ep, V

0.34 0.34
–2.2
0.30 0.30 –2.2
0.26 –2.6 0.26 –2.6
0.22 –3.0 0.22
–5.5–4.5–3.5–2.5–1.5 –2.2 –1.8 –1.4 –1.0 –5 –4 –3 –2 –2.6–2.2–1.0–1.4–1.0
lnV (V/s) logV (V/s) lnV (V/s) logV (V/s)

Fig. 9. (a) Reduction peak of platinum oxides on Ti/Pt

electrode (2 mg/cm2 Pt, upon heat treatment at 583 K) at
Fig. 8. (a) Reduction peak of platinum oxides on Ti/Pt different potential scan rates (mV/s): (1) 5, (2) 10, (3) 30,
electrode (2 mg/cm2 Pt) at different potential scan rates (4) 50, (5) 100, and (6) 150. (b) Dependence of the peak
(mV/s): (1) 5, (2) 10, (3) 30, (4) 50, (5) 100, and (6) 150. current on Ti/Pt electrode (2 mg/cm2 Pt, upon heat treat
(b) Dependence of the peak current on Ti/Pt electrode (2 ment at 583 K) on the potential scan rate. (c) Dependence
mg/cm2 Pt) on the potential scan rate. (c) Dependence of of the peak potential on Ti/Pt electrode (2 mg/cm2 Pt,
the peak potential on Ti/Pt electrode (2 mg/cm2 Pt) on the upon heat treatment at 583 K) on the potential scan rate.
potential scan rate. (d) Logarithmic dependence of the (d) Logarithmic dependence of the peak current on Ti/Pt
peak current on Ti/Pt electrode (2 mg/cm2 Pt) on the electrode (2 mg/cm2 Pt, upon heat treatment at 583 K) on
potential scan rate. the potential scan rate.

titanium dioxide, which is characterized by a high bond probably determined by the formation of mixed plati
energy with oxygencontaining particles [21]. This num–titanium oxides at high temperature accompa
hypothesis is supported by the shift of the peak potential nied with phase transformation with a partial encapsu
by 20 mV to the negative values upon the heat treatment lation of the electrochemically active platinum com
of the electrode at 503 K. In this case, the peak current pounds over the electrode surface [22, 23].
is not changed, which indicates the constancy of the
amount of electrochemically active platinum involved
in oxygencontaining compounds. 0
Further increase in the temperature of treatment to
583 K seemingly results in the thermal diffusion of plat
inum and its uniform distribution over the titanium sur
face, which is confirmed by the SEM data. As a result, –0.01
i, А/сm2

the peak reduction potential of the oxygencontaining

platinum compounds on the inverse voltammogram is
shifted to higher values and becomes equal to the corre 1
sponding value observed on smooth platinum. In this –0.02 2
3
case, the peak current substantially increases, which 4
may be caused by the increase in the surface amount of 5
electrochemically active platinum compounds as a
result of the homogeneous distribution of platinum over –0.03
the substrate. 0 0.2 0.4
Increase in the temperature of treatment to 683 K E (AgCl/Ag), V
leads to a decrease in the peak current, which is seem
ingly due to the decrease in the surface amount of plat Fig. 10. The reduction peak of platinum oxides on voltam
mograms recorded at a linear potential scan rate of
inum caused by its diffusion deep into the substrate. At 100 mV/s in 1 M chloric acid on (1) Pt and (2–5) Ti/Pt
the same time, the peak potential of the cathodic reduc specimens: (2) without heat treatment and (3–5) upon
tion of platinum oxides increases. The effect observed is treatment at (3) 503, (4) 583, and (5) 683 K.

PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES Vol. 49 No. 5 2013

 564 KASIAN et al.

(а) (b) the electrochemical behavior of the residual compo

0.15 nents, e.g., lead dioxide, which is itself characterized by

E (AgCl, Ag), V
1 metallic conductivity [27]. As follows from [28–33], the
i, А/сm2

1 1.6 2
0.10
2
3
3
4
characteristics of titanium dioxide as a semiconductor
4
1.5 substantially depend on the conditions of its prepara
0.05 tion and are determined by the thickness of the oxide
1.4 film, oxide stoichiometry, and its allotropic modifica
tion.
0 1.3
1.4 1.5 1.6 1.7 1.8 1.9 2.0 –4.0–3.5–3.0–2.5–2.0 Therefore, we studied the semiconductor properties
E (AgCl/ Ag), V logi, А/сm2 of the oxide film formed on titanium as a result of its
heat treatment in a tube furnace in air at 683 K for an
hour (Fig. 12). The resulting material is an ntype semi
Fig. 11. Polarization curves (5 mV/s) in 1 M chloric acid conductor with a flat band potential (EFB) of –0.589 V
on platinized titanium electrodes produced upon heat
treatment at a temperature, K: (1) 298, (2) 503, (3) 583,
and a concentration of charge carriers of 6 × 1020 cm–3.
and (4) 683. The high concentration of charge carriers is probably
determined by the small thickness of the oxide film and
its nonstoichiometric composition, as a result of which
As was shown previously, the electrocatalytic activ the surface is not noticeably depleted of electrons that
ity of platinized titanium substantially depends on the are donated by the metallic titanium.
amount of platinum on the anode surface [24]. Heat Platinized titanium electrodes are highly doped
treatment of the electrodes promotes the thermal diffu semiconductors, because both metallic titanium and
sion of platinum and its encapsulation in titanium platinum serve as electron donors in this case. Figure 13
oxides, as a result of which the surface amount of elec shows Mott–Schottky dependences for platinized tita
trochemically active platinum changes. Therefore, the nium electrodes, which, as was to be expected, are
electrocatalytic activity of platinized titanium anodes ntype semiconductors. The flat band potential of the
obtained at different temperatures can depend on the electrode, which was not heattreated, is much higher
temperature of treatment. Figure 11 shows polarization than the corresponding values of the heattreated elec
curves recorded on platinized titanium electrodes in a 1 trodes (Table 2). This can be determined by the fact that
M chloric acid solution upon heat treatment of the titanium oxide film formed as a result of the anodic
electrodes at different temperatures. According to the polarization is thin, has less stoichiometric composi
data obtained, the overpotential of oxygen evolution tion, and substantially differs from those produced
depends on the production conditions of the electrode upon heat treatment. The concentration of charge car
material. It is worth noting also that, in all the cases riers in the electrode treated at 503 K and that in the
considered, polarization curves represented in semilog anode, which was not subjected to heat treatment,
arithmic coordinates have large slopes (Table 2). The almost coincide. This may be due to the fact that the
slopes, which substantially exceed the theoretically pos amount of metallic platinum, which acts as an electron
sible values, and the linear character of the dependences donor, does not practically change as a result of heat
unambiguously indicate the existence of the semicon treatment at low temperatures. With an increase in the
ductor component in the electrode capacitance. temperature, the flat band potential and the concentra
The semiconductor properties of platinized tita tion of charge carriers increase, that can be determined
nium electrodes are caused by the formation of titanium by the thermal diffusion of the alloying component
dioxide, which is known [25] to be ntype semiconduc (platinum) deep into the titanium substrate and the
tor. As was mentioned in [26], the presence of titanium resulting more uniform distribution of the component
dioxide in a coating, transient layer, or substrate affects at the higher temperature of treatment.

Table 2. The slopes of semilogarithmic potential–current dependences and semiconductor properties of titanium–plati
num composite electrodes
(a) Yintercept and (b) slope
Characteristics of Ti/Pt electrode Semiconductor properties
of polarization curves
Temperature
Pt content, mg/cm2 a, V b, mV EFB, V N × 10–23, cm–3
of treatment, K
298 1.94 157 0.788 6.8
503 1.88 134 0.337 5.2
2
583 1.84 140 0.412 14
683 1.85 147 0.487 16

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 ELECTROCHEMICAL PROPERTIES OF HEATTREATED PLATINIZED TITANIUM 565

14 5 × 106
1
12 2
C–2 × 10–8, сm4/F2 4 × 10 6

C–2, F2/cm4
3
4
10
3 × 106
8
7.5 × 105
6
5.0 × 105
4
2.5 × 105
2
0 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5
–0.6 –0.4 –0.2 0 0.2 E (AgCl/Ag), V
–0.5 –0.3 –0.1 0.1
E (AgCl/Ag), V
Fig. 13. The Mott–Schottky dependences on Ti/Pt elec
Fig. 12. The Mott–Schottky dependence on TiO2 trodes obtained upon heat treatment at (1) 298, (2) 503,
obtained upon heat treatment of titanium at 683 K at an (3) 583, and (4) 683 K at an alternating current frequency
alternating current frequency of 20 Hz. of 20 Hz.

The data given in Table 2 are in satisfactory agree

ment, supplement each other and clarify the nature of
the change in the slope of polarization curves repre
sented in semilogarithmic coordinates. For example, an
increase in the number of charge carriers results in the
decrease in the semiconductor component, which is
reflected in the decrease in the slope of the polarization (а) 50 µm (b) 20 µm
curves.
Fig. 14. SEM microphotos of Ti/Pt specimen without heat
Insofar as the reduction peak of oxygen on the treatment upon 60 h of the anodic polarization at
inverse voltammograms characterizes the surface 100 mA/cm2.
amount of electrochemically active platinum com
pounds on Ti/Pt electrodes, the value can be used for
predicting the electrocatalytic activity of heattreated The surface morphology of the electrodes that did
materials with the same platinum contents. As follows not undergo heat treatment also changes (Fig. 14).
from the data obtained (Table 3), the electrocatalytic Light spots on microphotos are enriched in platinum,
activity of heattreated Ti/Pt electrodes increases with while dark parts are enriched in titanium. As follows
an increase in the peak area (the charge spent). The from the data obtained, the active growth of titanium
charge spent on the reduction of platinum oxides in the oxides leads to the encapsulation of platinum, which
case of electrodes treated at 583 K is the largest. This apparently immerses in the oxide phase to form a com
can be determined by the thermal diffusion of platinum posite coating. With an increase in the duration of elec
over the surface under these conditions, whereas heat
trolysis, the semiconductor properties of the electrodes
treatment at higher temperatures results in the encapsu
lation of platinum in titanium oxides. approach those of the anodically formed titanium diox
ide films, which is accompanied by a decrease in the flat
Platinized titanium anodes are known to be charac band potential and the number of charge carriers.
terized by a long service life [3, 34]. Prolonged anodic
polarization of the heattreated Ti/Pt electrodes does
not affect their semiconductor and electrochemical Table 3. Comparison of the charge spent on the reduction
properties. Substantial changes are observed only in the of platinum oxides formed in the potential range of oxygen
case of electrodes that were not subjected to heat treat evolution to the electrocatalytic activity of the heattreated
ment. For example, upon anodic polarization for 60 h, Ti/Pt electrode
the flat band potential decreases from 0.788 to 0.385 V Ti/Pt electrode
and the concentration of charge carriers decreases from I, mA
Q, mC
6.8 × 1023 to 2.4 × 1023 cm–3. This can be determined by Pt content, Temperature (E = 1.8 V)
the oxygen consumption by nonstoichiometric tita mg/cm2 of treatment, K
nium oxides during the anodic polarization and the oxi 503 0.58 35.5
dation of platinum, which results in a drop in the num
ber of free electrons and, hence, in a decrease in the flat 2 583 2.67 162.9
band potential. 683 1.01 95.7

PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES Vol. 49 No. 5 2013

566 KASIAN et al.
ˆ ˆ
CONCLUSIONS 14. Ševc ík P., C ík G, G., Vlna, T., et al., Chem. Papers, 2009,
vol. 63, no. 2, p. 249.
When platinum is plated on a titanium substrate, a
composite coating composed of titanium oxides, 15. Telipan, G., Ignat, M., Tablet, C., et al., J. Optoelectron.
metallic titanium, platinum, and TixPty intermetallic Adv. Mater., 2008, vol. 10, no. 8, p. 2138.
compound is formed. Heat treatment of the materials 16. Korobov, V.I. and Ochkov, V.F., Chemical Kinetics with
results in substantial changes in their electrochemical Mathcad and Maple, New York: Springer, 2011.
properties, which is caused by changes in the surface
morphology and chemical composition. Platinized tita 17. Korobov, V.I. and Ochkov, V.F., Khimicheskaya kine
tika: Vvedenie v Mathcad/ Maple/MCS, (Chemical
nium electrodes are found to be ntype semiconductors, Kinetics: Introduction to Mathcad, Maple, MCS),
and an increase in the temperature of treatment results Moscow: Goryachaya LiniyaTelekom, 2009.
in the increase in the flat band potential and the number
of charge carriers due to the redistribution of platinum 18. Yakimenko, L.M., Elektrodnye materialy v prikladnoi
over the surface and deep in the bulk determined by the elektrokhimii (Electrode Materials in Applied Electro
chemistry), Moscow: Khimiya, 1977.
diffusion and sintering. It is proposed to use the reduc
tion peak of oxygencontaining platinum compounds 19. Belen’kii, M.A. and Ivanov, A.F., Elektroosazhdenie
observed on the inverse voltammogram as a correlation metallicheskikh pokrytii. Spravochnik (Electroplating
parameter for predicting the electrocatalytic activity of Metallic Coatings: Handbook), Moscow: Metallurgiya,
the heattreated Ti/Pt composite electrodes with 1985.
respect to the oxygenevolution process. The rate of 20. Galus, Z., Fundamentals of Electrochemical Analysis,
oxygen evolution is found to increase with an increase New York: Ellis Horwood, 1994.
in the reductionpeak area (the charge spent). 21. Becerik, I. and Kadirgan, F., Turk. J. Chem., 2001,
vol. 25, p. 373.

REFERENCES 22. Pesty, F., Steinriick, H.P., and Madey, T.E., Surf. Sci.,
1995, vol. 339, p. 83.
1. Wang, X.Y., Jiang, Y.S., Zhu, H., et al., Chem. Res. 23. Matsumoto, T., Batzill, M., Hsieh, S., et al., Surf. Sci.,
Chin. Univ., 2011, vol. 27, no. 3, p. 486. 2004, vol. 572, p. 146.
2. Kim, J. and Choi, W., Appl. Catal. B, 2011, vol. 106, 24. Kasian, O., Luk’yanenko, T., and Velichenko, A., Russ.
nos. 1–2, p. 39. J. Electrochem., 2012, vol. 48, no. 12, p. 1.
3. Kasian, O., Luk’yanenko, T., and Velichenko, A., Chem. 25. Gurevich, Yu.Ya. and Pleskov, Yu.V., Fotoelek
Chem. Technol., 2012, vol. 6, no. 3, p. 241. trokhimiya poluprovodnikov (Photoelectrochemistry of
Semiconductors), Moscow: Nauka, 1983.
4. Shanmugam, S. and Gedanken, A., J. Phys. Chem. C,
2009, vol. 113, no. 43, p. 18707. 26. Devilliers, D. and Mahe, E., Electrochim. Acta, 2010,
vol. 55, p. 8207.
5. Selvaganesh, S.V., Selvarani, G., Sridhar, P., et al., J.
Electrochem. Soc., 2010, vol. 157, no. 7, p. B1000. 27. Razina, N.F., Okisnye elektrody v vodnykh rastvorakh
(Oxide Electrodes in Aqueous Solutions), AlmaAta:
6. Jang, G.W. and Rajeshwar, K., J. Electrochem. Soc., Nauka, 1982.
1987, vol. 134, no. 7, p. 1830.
28. Di Quarto, F., Piazza, S., and Sunseri, C., Electrochim.
7. Tamura, T., Ishibashi, S., Terakura, K., et al., Phys. Rev. Acta, 1993, vol. 38, p. 29.
B, 2009, vol. 80, no. 19.
29. Sellers, M.C.K. and Seebauer, E.G., Thin Solid Films,
8. Selvarani, G., Maheswari, S., Sridhar, P., et al., J. Elec 2011, vol. 519, p. 2103.
trochem. Soc., 2009, vol. 156, no. 11, p. B1354.
30. Blackwood, D.J., Electrochim. Acta, 2000, vol. 46,
9. Jeong, D.S., Schroeder, H., and Waser, R., Nanotecnol p. 563.
ogy, 2009, vol. 20, no. 37. 31. Dolata, M., Kedzierzawski, P., and Augustynski, J.,
10. Kim, S. and Lee, S.K., J. Photochem. Photobiol. A, Electrochim. Acta, 1996, vol. 41, nos. 7–8, p. 1287.
2009, vol. 203, nos. 2–3, p. 145. 32. Munoz, A.G., Electrochim. Acta, 2007, vol. 52, p. 4167.
11. Fan, J.W., Liu, X.H., and Zhang, J., Environ. Tech 33. Sang, L.X., Zhang, Z.Y., and Ma, C.F., Int. J. Hydrogen
nol., 2011, no. 4, p. 427. Energy, 2011, vol. 36, p. 4732.
12. Hirakawa, K., Inoue, M., and Abe, T., Electrochim. 34. Kasatkin, E.V., Potapova, G.F., Erusalimchik, I.G.,
Acta, 2010, vol. 55, no. 20, p. 5874. et al., Prot. Met. Phys. Chem. Surf., 2010, vol. 46, no. 6,
p. 673.
13. Wen, D., Shaojun, G., Junfeng, Z., et al., J. Phys. Chem.
C, 2009, vol. 113, no. 30, p. 13023. Translated by Y. Novakovskaya

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