CORRELATION OF THE SURFACE STRUCTURE OF THE RuO2/Ti AND TiO2 /Ti FILMS WITH ELECTROCHEMICAL IMPEDANCE DATA
The surface structure and nature of the capacitance formation of RuO2/Ti and TiO2 /Ti films are discussed. The factors affecting the reversibility of the adsorption-desorption processes of oxygen on the surface of RuO2/Ti and TiO2 /Ti films are described. The influence of the geometry of the pore, r...
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| Дата: | 2022 |
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| Автори: | , |
| Формат: | Стаття |
| Мова: | Англійська |
| Опубліковано: |
V.I.Vernadsky Institute of General and Inorganic Chemistry
2022
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Ukrainian Chemistry Journal| _version_ | 1871465863809335296 |
|---|---|
| author | Linyucheva, Olga Pershina, Katherine |
| author_facet | Linyucheva, Olga Pershina, Katherine |
| author_institution_txt_mv | [
{
"author": "Olga Linyucheva",
"institution": "Хіміко-технологічного факультету КПІ ім.Ігоря Сікорського"
},
{
"author": "Katherine Pershina",
"institution": "Vernadsky Institute of General and Inorganic Chemistry N.A.S of Ukraine, Kiev, Palladin av., 32\/34,03142 Ukraine"
}
] |
| author_sort | Linyucheva, Olga |
| baseUrl_str | https://ucj.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-07-22T08:23:50Z |
| description | The surface structure and nature of the capacitance formation of RuO2/Ti and TiO2 /Ti films are discussed. The factors affecting the reversibility of the adsorption-desorption processes of oxygen on the surface of RuO2/Ti and TiO2 /Ti films are described. The influence of the geometry of the pore, ruthenium content, thickness of the films, and the capacitance value of oxide films was studied using electron microscopy and electrochemical impedance spectroscopy. The changes in pore content and their geometry depending on Ru concentration are fixed by electron microscopy. The changing capacitance and capacitance dispersion in a wide frequency range was used to obtain 3D images of the film's surface. A scheme of the adsorption-absorption ratio changing in relation to the pore’s structure of the films was proposed. The study of the composition, morphological structure and electrochemical behaviour of RuO2/Ti and TiO2 /Ti films determined the impact of the pore shape of surface films on the adsorption-absorption ratio of oxygen, which regulated technical data of sensors. By changing the capacitance and capacitance dispersion in a wide frequency range, it was proposed to obtain 3D images of the surface. It was found that decrease of DEL capacitance has following relationships: large V-shaped pores on the boundary of titanium base and oxide film and on the surface of film > small V-shaped pores on the boundary of titanium base and oxide film, and large pores on the surface of film > rectangular-shaped pores on the boundary of titanium base and oxide film and small V-shaped pores on the surface of film. The formation of the pore geometry and surface structure is dependent on the ration of ruthenium and the thickness of films. So, it is possible to change the morphological and electrochemical properties of sensors by the regulation of ruthenium content. |
| doi_str_mv | 10.33609/2708-129X.88.08.2022.97-105 |
| first_indexed | 2025-09-24T17:43:46Z |
| format | Article |
| fulltext |
97
UDK 544.6.018+544.6.076 doi: 10.33609/2708-129X.88.08.2022.97-105
CORRELATION OF THE SURFACE STRUCTURE OF THE RuO2/Ti AND
TiO2 /Ti FILMS WITH ELECTROCHEMICAL IMPEDANCE DATA
O. Linucheva1, K. Pershina2
1National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”,
37 Peremogy avе., build. 4, Kyiv 03056, Ukraine
2Vernadskiy Institute of General and Inorganic Chemistry N.A.S of Ukraine,
32/34 Acad. Palladin ave., Kyiv 03142, Ukraine
Е-mail: katherinepersh@gmail.com
The surface structure and nature of the capacitance formation of RuO2/Ti and TiO2/Ti
films are discussed. The factors affecting the reversibility of the adsorption-desorption pro-
cesses of oxygen on the surface of RuO2/Ti and TiO2 /Ti films are described. The influence of
the geometry of the pore, ruthenium content, thickness of the films, and the capacitance value
of oxide films was studied using electron microscopy and electrochemical impedance spect
roscopy. The changes in pore content and their geometry depending on Ru concentration are
fixed by electron microscopy. The changing capacitance and capacitance dispersion in a wide
frequency range was used to obtain 3D images of the film's surface. A scheme of the adsorp-
tion-absorption ratio changing in relation to the pore’s structure of the films was proposed.
Keywords: ruthenium, titanium, surface film, pore geometry, capacitance, sensitivity.
INTRODUCTION. The increasing concern
in the detection of combustion gases calls for
the development of highly sensitive sensor de-
vices as well as for the understanding and de-
termination of simplified models of such sen-
sor operation mechanisms. For many years the
main interest has been focused on wide band-
gap semiconducting metal oxides such as SnO2,
ZnO, and TiO2, which suffer changes in con-
ductance when oxidizing or reducing species
in the air, which have the ability to chemisorb-
ing onto the oxide particle or film surface [1, 2].
However, sensors based on TiO2 systems re-
quire more effort in order to improve the se-
lectivity, stability, and response times at high
temperatures (300 °C–600 °C) [3, ]. One of the
suggested methods for improving the perfor-
mance of such sensors is doping TiO2-based
systems with variable valence elements such as
Pt, Ru, Cr, etc. [5–7] or semi-conductive oxi
des [8−10]. The simplicity and high sensitivity
of these devices are based on the high surface
area, high porosity, and effective surface modu
lation of the oxides [11]. In the presence of the
stoichiometric RuO2 (110) surface is terminat-
ed by bridge-coordinated oxygen atoms (Oβ)
and by coordinatively unsaturated Ru (Rucus)
atoms. The exposure to gaseous O2 leads to the
98 ISSN 2708-129X. Укр. хім. журн., 2022
CORRELATION OF THE SURFACE STRUCTURE OF THE RuO2/Ti AND TiO2 /Ti FILMS WITH ELECTROCHEMICAL IMPEDANCE DATAPHISICAL CHEMISTRY
formation of two additional surface species: a
molecularly chemisorbed state (Oσ) bridging
two neighboring Rucus atoms and weakly held
O atoms (Oγ) in a terminal position above the
Rucus atoms [12−14]. Based on such properties
a new thick film oxygen potentiometric sensors
have been developed. Moreover, TiO2-coated
RuO2 electrodes showed a linear response as
a function of the logarithm of the dissolved
oxygen concentration in the 0.5–8 ppm range
(log [O2], −4.82 to −3.60; concentration of O2
in mol dm−3). The electrode displays a Nern-
stian slope of 59.4 mV per decade at 25 °C.
The value of this slope suggests the presence
of a reaction involving one electron per oxygen
molecule which was tentatively attributed to
the formation of super-oxide ions at the elec-
trode surface [15]. So, it has many questions
about the formation of sensitive properties of
TiO2/ RuO2 films. But there is no systematic
study of the correlation between surface pore
configuration and electrochemical behavior of
the films. The present study focuses on under-
standing the role of the thickness and compo-
nent composition of TiO2/ RuO2 films in the
electrochemical behavior of sensors.
EXPERIMENT AND DISCUSSIONS OF
THE RESULTS. Synthesis of Undoped and
Doped TiO2 films was realized by three various
methods: pyrolysis, spray - pyrolysis and sol-
gel precipitation.
Pyrolysis. Catalytically active titanium
based coatings were obtained by thermal de-
composition of the corresponding metal salts.
To do this, a calculated amount of metal salt
was dissolved in water, added to the titanium
powder and dried under a lamp reflector in a
porcelain bowl, after which the composition
was subject to calcination in a muffle furnace
in a titanium crucible at a certain temperature.
In order to avoid catalyst losses, decomposi-
tion was carried out in a muffle furnace in the
presence of porous ceramic soaked in water.
All powders were stored in closed containers.
The reaction of the pyrolysis in the presence
of water ends with the formation of oxide:
RuOHCl3 + H2O = RuO2 +3HCl ↑
TiCl4 + 2 H2O → TiO2 +4HCl ↑.
Spray- pyrolysis: the production of TiO2
films is based on the thermal decomposition of
aerosol salt solutions on hot substrates. Aerosol
phase was obtained by pneumatic method. The
experimental setup consisted of elements such
as a compressor, an atomizer, a substrate hold-
er, a reaction chamber, an oven, a measuring
tank for spray. The furnace used for pyrolysis
was of a cylindrical type: 0.1 m in diameter and
0.2 meter in length. The sprayer had an outlet
with a diameter of ~ 2.5x10-4 m. The gas was
purified air under a pressure of 1.3−2.5 atm.
A water-alcohol solution of titanium chloride
was used as a precursor. The initial concentra-
tion of the solution was 0.2 M. This concentra-
tion is optimal for the deposition time of the
film, which affects the cooling of the substrate
during the deposition process and the ability
to control the thickness and growth rate of the
TiO2 film. The solution was sprayed onto heat-
ed titanium substrates. The substrate tempera-
ture was in the range of T = 400−450 ° C (the
optimum temperature range for the manufac-
ture of gas sensors). Films deposited at the in-
dicated temperatures have maximum porosity.
The flow rate of the solution during deposition
was ~ 0.1 ml / s.
Sol-Gel: The method included several main
technological phases. Initially, water or orga
nic solutions of the initial substances were ob-
tained. To obtain a sol we used hydrolysis of
99https://ucj.org.ua
O. Linucheva, K. Pershina UCJ № 8 / Vol. 88
salts of weak bases or alcohols. After that the
sol was transformed into a gel by removing a
part of water from it using heating and subse-
quent extraction with the appropriate solvent.
Obtained gel was used directly for the manu-
facturing of films and monolithic products.
Aerogels or xerogels (fragile microporous
powder) were obtained after drying of the gel.
Such powders were used for catalytically ac-
tive indicator electrode formation. Samples of
TiO2, RuO2 were made by the sol-gel method
with drying at T = 320 °C for 50−60 minutes
and further temperature processing at T = 400-
450 °C during 20 minutes.
The surface morphology of TiO2 and TiO2/
RuO2 films was analyzed by SEM (JEOL JSM-
6060 LA) operated at 30 kV. A scanning elec-
tron microscope (SEM) (Ultra 55 from ZEISS)
equipped with an Energy Dispersive X-ray
(EDX) analyzer was employed for the investi-
gation of the obtained morphology including
the diameter and length of the nano-tubular
layer and changes in morphology, which may
occur in the case of doping and/or heat treat-
ment. A detailed investigation of the morpho
logy and composition of the doped layers was
carried out by transmission electron micros-
copy (TEM). In addition, TEM investigations
by means of bright/dark field were employed
to determine the phase conditions of Ru doped
TiO2.
Impedance spectra were recorded from
0.001 to 1 MHz with no bias and limited volt-
age (10 mV) as air was contacting with sensor
samples. The impedance spectra were taken in
a two-electrode cell using an Autolab30 elec-
trochemical modular block (PGSTAT302N
Metrohm Autolab) equipped with a FRA
(Frequency Response Analyzer) assembly
unit within the range from 10–2 to 106 Hz.
The modular block was controlled by Autolab
4.9 according to the standard procedure. The
spectral analysis, the equivalent circuit (EC)
and the simulation of the EC were done with
the software ZView 2,0 of Scribner Assoc.
According to elemental analyses of samples,
the growth of the thickness of RuO2 surface
films increased the Ru amount in the coating
by linear law (tab.1). So, it could be assumed
that Ru plays the main role in the formation of
the surface properties of obtained films. And
the subsequent electrochemical studies of such
systems showed the impact of film thickness
on their electrochemical properties.
Table 1. Elemental composition and thickness of the surface films.
№ Ti, mass % Ru, mass % Thickness of films, nm
1 100 0 –
2 99,97 0,017 0,5
3 99,89 0,098 5
4 99,15 0,836 95
The simulation of the film’s EIS spectrum
determined that pure TiO2 had another equi
valent circuit than TiO2/RuO2 systems. Such
circuits are typical of the systems with sepa-
rate bulk layers present between Ti/TiO2. In
such case a double electrical layer (DEL) on
the TiO2 surface is formed by the adsorption
of oxygen, and the presence of oxygen created
100 ISSN 2708-129X. Укр. хім. журн., 2022
CORRELATION OF THE SURFACE STRUCTURE OF THE RuO2/Ti AND TiO2 /Ti FILMS WITH ELECTROCHEMICAL IMPEDANCE DATAPHISICAL CHEMISTRY
an additional inductance element in the equi
valent circuit [16, 17]. So, the presence of pa
ramagnetic properties of adsorbed oxygen mo
lecules formed an image of spectra (all spectra
occurred in the positive part of the Nyquist
plot) (fig. 1).
Calculation of capacitance demonstrated
linear dependence between the capacitance
and thickness of RuO2 coatings. The maximum
value of capacitance is exhibited by the sample
with minimal thickness of the RuO2 film. Dur-
ing growth of thickness, capacitance decreas-
es. Minimum value was demonstrated by pure
TiO2 film (table 2).
Fig. 1 EIS spectra in Nyquist plots and equivalent circuits of the electrode samples: 1 – TiO2, 2−4 -
TiO2/RuO2 with different thickness of coatings: 2 − 0,5 nm, 3 − 5 nm, 4 − 95 nm.
Table 2 Relationship between the capacitance and thickness of RuO2 coatings
№ Thickness of films, nm Capacitance (C ), F
1 – 1,21
2 0,5 6,58
3 5 4,65
4 95 3,89
It is well known that equivalent circuit for
the adsorption control of hydrogen in solu-
tions [18] consists of CD- double-layer capaci
tance RadH, CadH- resistance and capacitance
of hydrogen adsorption Re-solution resistance
(Fig. 2).
Fig. 2. Equivalent circuit for adsorption control [18].
101https://ucj.org.ua
O. Linucheva, K. Pershina UCJ № 8 / Vol. 88
The same equivalent circuit was obtained
for Ti/TiO2 sample. But for Ti/TiO2 and TiO2/
RuO2, samples in the presence of oxygen
equivalent circuit transformed into another
circuit with inductance and without second
capacitance (fig1). The appearance of in-
ductance in the equivalent circuits could be
connected with adsorption of paramagnetic
species, such as O2. So, the large frequency
range of inductance indicates a big amount of
adsorbed oxygen and large area of the elec-
trode surface, which takes part in adsorption.
Such behavior could be realized only in the
presence of sufficient quantity of pores on the
electrode surface. Moreover, the images of
impedance spectrum according to [19] like
images of porous electrodes with V-shaped
pores (fig. 3).
Fig. 3. Modes of porous electrode impedance spectrum with various forms of porous after Kaiser et
al. [19].
It is well known that porous electrode is not
ideal polarized electrode and has a tendency to
dispersion of capacitance [20].
Fig. 3. Modes of porous electrode impedance spectrum with various forms of porous after Kaiser
et al. [19].
It is well known that porous electrode is not ideal polarized electrode and has a
tendency to dispersion of capacitance [20].
𝐶𝐶(𝜔𝜔) = ([(𝑍𝑍𝑍𝑍) − 𝑍𝑍(𝜔𝜔 → ∞)]𝜔𝜔) (1)
Such dispersion is the main characteristic of the surface morphology of an electrode.
On the another hand, capacitance according to Kirchhoff’s circuit laws [19, 21] is the function of
the currents in the electrical circuit nodes:
𝑑𝑑𝑢𝑢𝐶𝐶
𝑑𝑑𝑑𝑑 = 1
𝐶𝐶 (−𝑖𝑖2 + 𝑖𝑖1 + 𝐽𝐽) = 1
𝐶𝐶 (−
𝑢𝑢𝐶𝐶
𝑅𝑅2
+ 𝑖𝑖1 + 𝐽𝐽) (2)
So, the capacitance at fixed frequency could be used as second parameter for recognizing pore
image.
Moreover, by changing the frequency of alternating electric current it would be possible to
obtain 3D fiber form of surface films (fig. 4−7).
a b
Fig. 4. SEM and EIS images for Ti/TiO2: a − SEM images; b – EIS images.
a b
Fig. 5. SEM and EIS images for TiO2/RuO2 (0,5 nм): a − SEM images; b – EIS images.
a b
Fig. 6. SEM and EIS images for TiO2/RuO2 (5 nм): a − SEM images; b – EIS images.
(1)
Such dispersion is the main characteristic
of the surface morphology of an electrode. On
the another hand, capacitance according to
Kirchhoff ’s circuit laws [19, 21] is the function
of the currents in the electrical circuit nodes:
Fig. 3. Modes of porous electrode impedance spectrum with various forms of porous after Kaiser
et al. [19].
It is well known that porous electrode is not ideal polarized electrode and has a
tendency to dispersion of capacitance [20].
𝐶𝐶(𝜔𝜔) = ([(𝑍𝑍𝑍𝑍) − 𝑍𝑍(𝜔𝜔 → ∞)]𝜔𝜔) (1)
Such dispersion is the main characteristic of the surface morphology of an electrode.
On the another hand, capacitance according to Kirchhoff’s circuit laws [19, 21] is the function of
the currents in the electrical circuit nodes:
𝑑𝑑𝑢𝑢𝐶𝐶
𝑑𝑑𝑑𝑑 = 1
𝐶𝐶 (−𝑖𝑖2 + 𝑖𝑖1 + 𝐽𝐽) = 1
𝐶𝐶 (−
𝑢𝑢𝐶𝐶
𝑅𝑅2
+ 𝑖𝑖1 + 𝐽𝐽) (2)
So, the capacitance at fixed frequency could be used as second parameter for recognizing pore
image.
Moreover, by changing the frequency of alternating electric current it would be possible to
obtain 3D fiber form of surface films (fig. 4−7).
a b
Fig. 4. SEM and EIS images for Ti/TiO2: a − SEM images; b – EIS images.
a b
Fig. 5. SEM and EIS images for TiO2/RuO2 (0,5 nм): a − SEM images; b – EIS images.
a b
Fig. 6. SEM and EIS images for TiO2/RuO2 (5 nм): a − SEM images; b – EIS images.
(2)
So, the capacitance at fixed frequency could
be used as second parameter for recognizing
pore image.
Moreover, by changing the frequency of
alternating electric current it would be pos-
sible to obtain 3D fiber form of surface films
(fig. 4−7).
102 ISSN 2708-129X. Укр. хім. журн., 2022
CORRELATION OF THE SURFACE STRUCTURE OF THE RuO2/Ti AND TiO2 /Ti FILMS WITH ELECTROCHEMICAL IMPEDANCE DATAPHISICAL CHEMISTRY
a b
Fig. 4. SEM and EIS images for Ti/TiO2: a − SEM images; b – EIS images.
a b
Fig. 5. SEM and EIS images for TiO2/RuO2 (0,5 nм): a − SEM images; b – EIS images.
a b
Fig. 6. SEM and EIS images for TiO2/RuO2 (5 nм): a − SEM images; b – EIS images.
a b
Fig. 7. SEM and EIS images for TiO2/RuO2 (95 nм): a − SEM images; b – EIS images.
Fig. 3. Modes of porous electrode impedance spectrum with various forms of porous after Kaiser
et al. [19].
It is well known that porous electrode is not ideal polarized electrode and has a
tendency to dispersion of capacitance [20].
𝐶𝐶(𝜔𝜔) = ([(𝑍𝑍𝑍𝑍) − 𝑍𝑍(𝜔𝜔 → ∞)]𝜔𝜔) (1)
Such dispersion is the main characteristic of the surface morphology of an electrode.
On the another hand, capacitance according to Kirchhoff’s circuit laws [19, 21] is the function of
the currents in the electrical circuit nodes:
𝑑𝑑𝑢𝑢𝐶𝐶
𝑑𝑑𝑑𝑑 = 1
𝐶𝐶 (−𝑖𝑖2 + 𝑖𝑖1 + 𝐽𝐽) = 1
𝐶𝐶 (−
𝑢𝑢𝐶𝐶
𝑅𝑅2
+ 𝑖𝑖1 + 𝐽𝐽) (2)
So, the capacitance at fixed frequency could be used as second parameter for recognizing pore
image.
Moreover, by changing the frequency of alternating electric current it would be possible to
obtain 3D fiber form of surface films (fig. 4−7).
a b
Fig. 4. SEM and EIS images for Ti/TiO2: a − SEM images; b – EIS images.
a b
Fig. 5. SEM and EIS images for TiO2/RuO2 (0,5 nм): a − SEM images; b – EIS images.
a b
Fig. 6. SEM and EIS images for TiO2/RuO2 (5 nм): a − SEM images; b – EIS images.
Fig. 3. Modes of porous electrode impedance spectrum with various forms of porous after Kaiser
et al. [19].
It is well known that porous electrode is not ideal polarized electrode and has a
tendency to dispersion of capacitance [20].
𝐶𝐶(𝜔𝜔) = ([(𝑍𝑍𝑍𝑍) − 𝑍𝑍(𝜔𝜔 → ∞)]𝜔𝜔) (1)
Such dispersion is the main characteristic of the surface morphology of an electrode.
On the another hand, capacitance according to Kirchhoff’s circuit laws [19, 21] is the function of
the currents in the electrical circuit nodes:
𝑑𝑑𝑢𝑢𝐶𝐶
𝑑𝑑𝑑𝑑 = 1
𝐶𝐶 (−𝑖𝑖2 + 𝑖𝑖1 + 𝐽𝐽) = 1
𝐶𝐶 (−
𝑢𝑢𝐶𝐶
𝑅𝑅2
+ 𝑖𝑖1 + 𝐽𝐽) (2)
So, the capacitance at fixed frequency could be used as second parameter for recognizing pore
image.
Moreover, by changing the frequency of alternating electric current it would be possible to
obtain 3D fiber form of surface films (fig. 4−7).
a b
Fig. 4. SEM and EIS images for Ti/TiO2: a − SEM images; b – EIS images.
a b
Fig. 5. SEM and EIS images for TiO2/RuO2 (0,5 nм): a − SEM images; b – EIS images.
a b
Fig. 6. SEM and EIS images for TiO2/RuO2 (5 nм): a − SEM images; b – EIS images.
Fig. 3. Modes of porous electrode impedance spectrum with various forms of porous after Kaiser
et al. [19].
It is well known that porous electrode is not ideal polarized electrode and has a
tendency to dispersion of capacitance [20].
𝐶𝐶(𝜔𝜔) = ([(𝑍𝑍𝑍𝑍) − 𝑍𝑍(𝜔𝜔 → ∞)]𝜔𝜔) (1)
Such dispersion is the main characteristic of the surface morphology of an electrode.
On the another hand, capacitance according to Kirchhoff’s circuit laws [19, 21] is the function of
the currents in the electrical circuit nodes:
𝑑𝑑𝑢𝑢𝐶𝐶
𝑑𝑑𝑑𝑑 = 1
𝐶𝐶 (−𝑖𝑖2 + 𝑖𝑖1 + 𝐽𝐽) = 1
𝐶𝐶 (−
𝑢𝑢𝐶𝐶
𝑅𝑅2
+ 𝑖𝑖1 + 𝐽𝐽) (2)
So, the capacitance at fixed frequency could be used as second parameter for recognizing pore
image.
Moreover, by changing the frequency of alternating electric current it would be possible to
obtain 3D fiber form of surface films (fig. 4−7).
a b
Fig. 4. SEM and EIS images for Ti/TiO2: a − SEM images; b – EIS images.
a b
Fig. 5. SEM and EIS images for TiO2/RuO2 (0,5 nм): a − SEM images; b – EIS images.
a b
Fig. 6. SEM and EIS images for TiO2/RuO2 (5 nм): a − SEM images; b – EIS images.
Fig. 3. Modes of porous electrode impedance spectrum with various forms of porous after Kaiser
et al. [19].
It is well known that porous electrode is not ideal polarized electrode and has a
tendency to dispersion of capacitance [20].
𝐶𝐶(𝜔𝜔) = ([(𝑍𝑍𝑍𝑍) − 𝑍𝑍(𝜔𝜔 → ∞)]𝜔𝜔) (1)
Such dispersion is the main characteristic of the surface morphology of an electrode.
On the another hand, capacitance according to Kirchhoff’s circuit laws [19, 21] is the function of
the currents in the electrical circuit nodes:
𝑑𝑑𝑢𝑢𝐶𝐶
𝑑𝑑𝑑𝑑 = 1
𝐶𝐶 (−𝑖𝑖2 + 𝑖𝑖1 + 𝐽𝐽) = 1
𝐶𝐶 (−
𝑢𝑢𝐶𝐶
𝑅𝑅2
+ 𝑖𝑖1 + 𝐽𝐽) (2)
So, the capacitance at fixed frequency could be used as second parameter for recognizing pore
image.
Moreover, by changing the frequency of alternating electric current it would be possible to
obtain 3D fiber form of surface films (fig. 4−7).
a b
Fig. 4. SEM and EIS images for Ti/TiO2: a − SEM images; b – EIS images.
a b
Fig. 5. SEM and EIS images for TiO2/RuO2 (0,5 nм): a − SEM images; b – EIS images.
a b
Fig. 6. SEM and EIS images for TiO2/RuO2 (5 nм): a − SEM images; b – EIS images.
Fig. 3. Modes of porous electrode impedance spectrum with various forms of porous after Kaiser
et al. [19].
It is well known that porous electrode is not ideal polarized electrode and has a
tendency to dispersion of capacitance [20].
𝐶𝐶(𝜔𝜔) = ([(𝑍𝑍𝑍𝑍) − 𝑍𝑍(𝜔𝜔 → ∞)]𝜔𝜔) (1)
Such dispersion is the main characteristic of the surface morphology of an electrode.
On the another hand, capacitance according to Kirchhoff’s circuit laws [19, 21] is the function of
the currents in the electrical circuit nodes:
𝑑𝑑𝑢𝑢𝐶𝐶
𝑑𝑑𝑑𝑑 = 1
𝐶𝐶 (−𝑖𝑖2 + 𝑖𝑖1 + 𝐽𝐽) = 1
𝐶𝐶 (−
𝑢𝑢𝐶𝐶
𝑅𝑅2
+ 𝑖𝑖1 + 𝐽𝐽) (2)
So, the capacitance at fixed frequency could be used as second parameter for recognizing pore
image.
Moreover, by changing the frequency of alternating electric current it would be possible to
obtain 3D fiber form of surface films (fig. 4−7).
a b
Fig. 4. SEM and EIS images for Ti/TiO2: a − SEM images; b – EIS images.
a b
Fig. 5. SEM and EIS images for TiO2/RuO2 (0,5 nм): a − SEM images; b – EIS images.
a b
Fig. 6. SEM and EIS images for TiO2/RuO2 (5 nм): a − SEM images; b – EIS images.
Fig. 3. Modes of porous electrode impedance spectrum with various forms of porous after Kaiser
et al. [19].
It is well known that porous electrode is not ideal polarized electrode and has a
tendency to dispersion of capacitance [20].
𝐶𝐶(𝜔𝜔) = ([(𝑍𝑍𝑍𝑍) − 𝑍𝑍(𝜔𝜔 → ∞)]𝜔𝜔) (1)
Such dispersion is the main characteristic of the surface morphology of an electrode.
On the another hand, capacitance according to Kirchhoff’s circuit laws [19, 21] is the function of
the currents in the electrical circuit nodes:
𝑑𝑑𝑢𝑢𝐶𝐶
𝑑𝑑𝑑𝑑 = 1
𝐶𝐶 (−𝑖𝑖2 + 𝑖𝑖1 + 𝐽𝐽) = 1
𝐶𝐶 (−
𝑢𝑢𝐶𝐶
𝑅𝑅2
+ 𝑖𝑖1 + 𝐽𝐽) (2)
So, the capacitance at fixed frequency could be used as second parameter for recognizing pore
image.
Moreover, by changing the frequency of alternating electric current it would be possible to
obtain 3D fiber form of surface films (fig. 4−7).
a b
Fig. 4. SEM and EIS images for Ti/TiO2: a − SEM images; b – EIS images.
a b
Fig. 5. SEM and EIS images for TiO2/RuO2 (0,5 nм): a − SEM images; b – EIS images.
a b
Fig. 6. SEM and EIS images for TiO2/RuO2 (5 nм): a − SEM images; b – EIS images.
The obtained images (fig. 4−7) showed that Ti/TiO2 sample has rectangular-shaped pores
with small amount of V-shaped pores on the top piece of surface (fig. 4 b). On the another hand,
all the TiO2/RuO2 samples have the different levels of surface volume (fig. 5−7, b). The number
of V-shaped pores on the top piece of surface increases during growth of RuO2 film thickness
and has a maximum at maximum thickness and Ru concentration (fig 7.b).
Matching the value of capacitance and the presence of rectangular-shaped and V-shaped
pores on the boundary of titanium base and oxide film the following dependence of capacitance
decrease was shown: large V-shaped pores on the boundary of titanium base and oxide film and
on the surface of film > small V-shaped pores on the boundary of titanium base and oxide film,
and large pores on the surface of film > rectangular-shaped pores on the boundary of titanium
base and oxide film and small V-shaped pores on the surface of film. So, the decrease in of
capacitance would be connected with increase in the absorption of oxygen due to the presence of
various types of pores and their organization and a decrease in adsorption (fig. 8). In this case,
reversible adsorption-absorption processes on the surface are retarded the electrode could lose
sensitivity and considerably increase the time of sensor relaxation. Thus by selection of the
film’s content, it could be possible to regulate the technical data of sensors by changing
properties of the adsorption component (properly sensor) [1] and absorption component
(microgenerator) [22].
a b
Fig. 7. SEM and EIS images for TiO2/RuO2 (95 nм): a − SEM images; b – EIS images.
The obtained images (fig. 4−7) showed that Ti/TiO2 sample has rectangular-shaped pores
with small amount of V-shaped pores on the top piece of surface (fig. 4 b). On the another hand,
all the TiO2/RuO2 samples have the different levels of surface volume (fig. 5−7, b). The number
of V-shaped pores on the top piece of surface increases during growth of RuO2 film thickness
and has a maximum at maximum thickness and Ru concentration (fig 7.b).
Matching the value of capacitance and the presence of rectangular-shaped and V-shaped
pores on the boundary of titanium base and oxide film the following dependence of capacitance
decrease was shown: large V-shaped pores on the boundary of titanium base and oxide film and
on the surface of film > small V-shaped pores on the boundary of titanium base and oxide film,
and large pores on the surface of film > rectangular-shaped pores on the boundary of titanium
base and oxide film and small V-shaped pores on the surface of film. So, the decrease in of
capacitance would be connected with increase in the absorption of oxygen due to the presence of
various types of pores and their organization and a decrease in adsorption (fig. 8). In this case,
reversible adsorption-absorption processes on the surface are retarded the electrode could lose
sensitivity and considerably increase the time of sensor relaxation. Thus by selection of the
film’s content, it could be possible to regulate the technical data of sensors by changing
properties of the adsorption component (properly sensor) [1] and absorption component
(microgenerator) [22].
a b
Fig. 7. SEM and EIS images for TiO2/RuO2 (95 nм): a − SEM images; b – EIS images.
103https://ucj.org.ua
O. Linucheva, K. Pershina UCJ № 8 / Vol. 88
The obtained images (fig. 4−7) showed that
Ti/TiO2 sample has rectangular-shaped pores
with small amount of V-shaped pores on the
top piece of surface (fig. 4 b). On the another
hand, all the TiO2/RuO2 samples have the dif-
ferent levels of surface volume (fig. 5−7, b). The
number of V-shaped pores on the top piece of
surface increases during growth of RuO2 film
thickness and has a maximum at maximum
thickness and Ru concentration (fig 7.b).
Matching the value of capacitance and the
presence of rectangular-shaped and V-shaped
pores on the boundary of titanium base and
oxide film the following dependence of ca-
pacitance decrease was shown: large V-shaped
pores on the boundary of titanium base and
oxide film and on the surface of film > small
V-shaped pores on the boundary of titanium
base and oxide film, and large pores on the sur-
face of film > rectangular-shaped pores on the
boundary of titanium base and oxide film and
small V-shaped pores on the surface of film.
So, the decrease in of capacitance would be
connected with increase in the absorption of
oxygen due to the presence of various types of
pores and their organization and a decrease in
adsorption (fig. 8). In this case, reversible ad-
sorption-absorption processes on the surface
are retarded the electrode could lose sensitivity
and considerably increase the time of sensor
relaxation. Thus by selection of the film’s con-
tent, it could be possible to regulate the tech-
nical data of sensors by changing properties of
the adsorption component (properly sensor)
[1] and absorption component (microgenera-
tor) [22].
Fig. 8. Scheme of the adsorption - absorption ratio changing in relation to the film pore’s structure.
104 ISSN 2708-129X. Укр. хім. журн., 2022
CORRELATION OF THE SURFACE STRUCTURE OF THE RuO2/Ti AND TiO2 /Ti FILMS WITH ELECTROCHEMICAL IMPEDANCE DATAPHISICAL CHEMISTRY
CONCLUSIONS. The study of the compo-
sition, morphological structure and electro-
chemical behaviour of RuO2/Ti and TiO2 /Ti
films determined the impact of the pore shape
of surface films on the adsorption-absorption
ratio of oxygen, which regulated technical data
of sensors. By changing the capacitance and
capacitance dispersion in a wide frequency
range, it was proposed to obtain 3D images of
the surface. It was found that decrease of DEL
capacitance has following relationships: large
V-shaped pores on the boundary of titanium
base and oxide film and on the surface of film
> small V-shaped pores on the boundary of ti-
tanium base and oxide film, and large pores on
the surface of film > rectangular-shaped pores
on the boundary of titanium base and oxide
film and small V-shaped pores on the surface
of film. The formation of the pore geometry
and surface structure is dependent on the ra-
tion of ruthenium and the thickness of films.
So, it is possible to change the morphological
and electrochemical properties of sensors by
the regulation of ruthenium content.
ACKNOWLEDGMENT.
This work was supported by the Na-
tional Technical University of Ukraine
“Igor Sikorsky Kyiv Polytechnic Insti-
tute”, and National Academy of Sci-
ence of Ukraine.
КОРЕЛЯЦІЯ МІЖ ПОВЕРХНЕВОЮ СТРУКТУ-
РОЮ ПЛІВОК RuO2/Ti І TiO2/Ti З ДАНИМИ
ЕЛЕКТРОХІМІЧНОГО ІМПЕДАНСУ
О. В. Лінючева1, К. Д. Першина2
1Національний технічний університет Ук
раїни «Київський політехнічний інститут
імені Ігоря Сікорського»,
пр. Перемоги, 37, корп. 4, Київ 03056, Ук
раїна;
2Інститут загальної та неорганічної хімії
ім. В. І. Вернадського НАН України,
пр. Акад. Палладіна, 32/34, Київ 03142,
Україна
Обговорено структуру поверхні та ха-
рактер формування ємності плівок RuO2/Ti
та TiO2/Ti. Описано фактори, що вплива-
ють на оборотність процесів адсорбції-аб-
сорбції кисню на поверхні плівок RuO2/Ti
та TiO2/Ti. Вплив геометрії пор, вмісту
рутенію, товщини плівок і величини ємно-
сті оксидних плівок досліджували за допо-
могою електронної мікроскопії та спектро
скопії електрохімічного імпедансу. За допо
могою електронної мікроскопії фіксували
зміни вмісту пор та їхні геометрії залеж-
но від концентрації Ru. Зміну ємності та
дисперсію ємності в широкому діапазоні
частот було використано для отримання
3D-зображень поверхні плівки. Запропоно-
вано схему зміни співвідношення адсорб
ції-абсорбції кисню залежно від структури
пор плівок.
Ключові слова: рутеній, титан, поверх-
нева плівка, геометрія пор, ємність, чутли-
вість.
105https://ucj.org.ua
O. Linucheva, K. Pershina UCJ № 8 / Vol. 88
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Стаття надійшла 15.06.2022.
|
| id | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-475 |
| institution | Ukrainian Chemistry Journal |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-07-23T01:08:48Z |
| publishDate | 2022 |
| publisher | V.I.Vernadsky Institute of General and Inorganic Chemistry |
| record_format | ojs |
| resource_txt_mv | ucjorgua/6a/39b358b6753aa00f4a643ab7ba32086a.pdf |
| spelling | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-4752026-07-22T08:23:50Z CORRELATION OF THE SURFACE STRUCTURE OF THE RuO2/Ti AND TiO2 /Ti FILMS WITH ELECTROCHEMICAL IMPEDANCE DATA Linyucheva, Olga Pershina, Katherine ruthenium, titanium, surface film, pore geometry, capacitance, sensitivity. The surface structure and nature of the capacitance formation of RuO2/Ti and TiO2 /Ti films are discussed. The factors affecting the reversibility of the adsorption-desorption processes of oxygen on the surface of RuO2/Ti and TiO2 /Ti films are described. The influence of the geometry of the pore, ruthenium content, thickness of the films, and the capacitance value of oxide films was studied using electron microscopy and electrochemical impedance spectroscopy. The changes in pore content and their geometry depending on Ru concentration are fixed by electron microscopy. The changing capacitance and capacitance dispersion in a wide frequency range was used to obtain 3D images of the film's surface. A scheme of the adsorption-absorption ratio changing in relation to the pore’s structure of the films was proposed. The study of the composition, morphological structure and electrochemical behaviour of RuO2/Ti and TiO2 /Ti films determined the impact of the pore shape of surface films on the adsorption-absorption ratio of oxygen, which regulated technical data of sensors. By changing the capacitance and capacitance dispersion in a wide frequency range, it was proposed to obtain 3D images of the surface. It was found that decrease of DEL capacitance has following relationships: large V-shaped pores on the boundary of titanium base and oxide film and on the surface of film > small V-shaped pores on the boundary of titanium base and oxide film, and large pores on the surface of film > rectangular-shaped pores on the boundary of titanium base and oxide film and small V-shaped pores on the surface of film. The formation of the pore geometry and surface structure is dependent on the ration of ruthenium and the thickness of films. So, it is possible to change the morphological and electrochemical properties of sensors by the regulation of ruthenium content. V.I.Vernadsky Institute of General and Inorganic Chemistry 2022-09-26 Article Article Physical chemistry Физическая xимия Фізична xімія application/pdf https://ucj.org.ua/index.php/journal/article/view/475 10.33609/2708-129X.88.08.2022.97-105 Ukrainian Chemistry Journal; Vol. 88 No. 8 (2022): Ukrainian Chemistry Journal; 97-105 Украинский химический журнал; ##issue.vol## 88 ##issue.no## 8 (2022): Ukrainian Chemistry Journal; 97-105 Український хімічний журнал; Том 88 № 8 (2022): Український хімічний журнал; 97-105 2708-129X 2708-1281 en https://ucj.org.ua/index.php/journal/article/view/475/244 Copyright (c) 2022 Olga Linyucheva, Katherine Pershina https://creativecommons.org/licenses/by-nc/4.0 |
| spellingShingle | Linyucheva, Olga Pershina, Katherine CORRELATION OF THE SURFACE STRUCTURE OF THE RuO2/Ti AND TiO2 /Ti FILMS WITH ELECTROCHEMICAL IMPEDANCE DATA |
| title | CORRELATION OF THE SURFACE STRUCTURE OF THE RuO2/Ti AND TiO2 /Ti FILMS WITH ELECTROCHEMICAL IMPEDANCE DATA |
| title_full | CORRELATION OF THE SURFACE STRUCTURE OF THE RuO2/Ti AND TiO2 /Ti FILMS WITH ELECTROCHEMICAL IMPEDANCE DATA |
| title_fullStr | CORRELATION OF THE SURFACE STRUCTURE OF THE RuO2/Ti AND TiO2 /Ti FILMS WITH ELECTROCHEMICAL IMPEDANCE DATA |
| title_full_unstemmed | CORRELATION OF THE SURFACE STRUCTURE OF THE RuO2/Ti AND TiO2 /Ti FILMS WITH ELECTROCHEMICAL IMPEDANCE DATA |
| title_short | CORRELATION OF THE SURFACE STRUCTURE OF THE RuO2/Ti AND TiO2 /Ti FILMS WITH ELECTROCHEMICAL IMPEDANCE DATA |
| title_sort | correlation of the surface structure of the ruo2/ti and tio2 /ti films with electrochemical impedance data |
| topic_facet | ruthenium titanium surface film pore geometry capacitance sensitivity. |
| url | https://ucj.org.ua/index.php/journal/article/view/475 |
| work_keys_str_mv | AT linyuchevaolga correlationofthesurfacestructureoftheruo2tiandtio2tifilmswithelectrochemicalimpedancedata AT pershinakatherine correlationofthesurfacestructureoftheruo2tiandtio2tifilmswithelectrochemicalimpedancedata |