Advanced electrochromic Ni(Oh)2/PVA films formed by electrochemical template synthesis

Abstract

Electrochromic nickel hydroxide film has been prepared for the first time, using electrochemical template
synthesis with polyvinyl alcohol (PVA) as template. Such advanced Ni(OH)2/PVA composite film has improved adhesion
to substrate and can be potentially used for manufacturing flexible electrochromic devices. Films obtained by template
cathodic deposition can be stored in a dry state without morphological changes which allows for optimization of
manufacturing of complete devices. The optimal concentration of polyvinyl in electrode position solution has been found
5% wt. It has been demonstrated that polyvinyl forms nanosized 3-D matrix on substrate surface which promotes formation
of X-ray amorphous nickel hydroxide and is incorporated into the film. It has been established, that at optimal current
density 0.625 mA/cm2 the deposition rate is 3.87μm/h. By simultaneously recording cyclic voltammogramms and
colorization curves high electrochemical and optical properties of films prepared using template synthesis with PVA have
been demonstrated, with coloration degree of up to 80%. Significant effect of drying temperature on electrochemical and
optical properties of Ni(OH)2/PVA composite films has been demonstrated. Low drying temperature (20° С) results in
films with high electrochemical activity and coloration degree. At 90° С a drop in colorization degree has been observed.

Full text

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3962
ADVANCED ELECTROCHROMIC Ni(OH)2/PVA FILMS FORMED BY
ELECTROCHEMICAL TEMPLATE SYNTHESIS
Kotok V. A.1, 2, Kovalenko V. L.1, 2, Kovalenko P. V.2, Solovov V. A.1, Deabate S.3, Mehdi A.4,
Bantignies J.-L.5 and Henn F.5
1Ukrainian State University of Chemical Technology, Gagarina Ave, Dnipropetrovsk, Ukraine
2Vyatka State University, Moskovskaya str, Kirov, Russian Federation
3Institut Européen des Membranes, UMR CNRS-ENSCM-UM, Université de Montpellier, rue Auguste Broussonnet Montpellier, France
4Institut Charles Gerhardt de Montpellier, UMR CNRS-UM, Université de Montpellier, rue Auguste Broussonnet Montpellier, France
5Equipe Nanomateriaux et Spectroscopie, Laboratoire Charles Coulomb, UMR CNRS-UM, Université de Montpellier, rue Auguste
Broussonnet Montpellier, France
E-Mail: Valeriy_e-ch@ukr.net
ABSTRACT
Electrochromic nickel hydroxide film has been prepared for the first time, using electrochemical template
synthesis with polyvinyl alcohol (PVA) as template. Such advanced Ni(OH)2/PVA composite film has improved adhesion
to substrate and can be potentially used for manufacturing flexible electrochromic devices. Films obtained by template
cathodic deposition can be stored in a dry state without morphological changes which allows for optimization of
manufacturing of complete devices. The optimal concentration of polyvinyl in electrode position solution has been found
5% wt. It has been demonstrated that polyvinyl forms nanosized 3-D matrix on substrate surface which promotes formation
of X-ray amorphous nickel hydroxide and is incorporated into the film. It has been established, that at optimal current
density 0.625 mA/cm2 the deposition rate is 3.87μm/h. By simultaneously recording cyclic voltammogramms and
colorization curves high electrochemical and optical properties of films prepared using template synthesis with PVA have
been demonstrated, with coloration degree of up to 80%. Significant effect of drying temperature on electrochemical and
optical properties of Ni(OH)2/PVA composite films has been demonstrated. Low drying temperature (20° С) results in
films with high electrochemical activity and coloration degree. At 90° С a drop in colorization degree has been observed.
Keywords: nickel hydroxide film, template electrochemical synthesis, polyvinyl alcohol, electrochromic properties, smart windows.
1. INTRODUCTION
Electrochromism is a reversible phenomenon
leading to materials colorization and bleaching under
polarization current. Electrochromic effects, typical of
some metal oxides or hydroxides [1-11], appear upon
either oxidation or reduction reaction. Thereby
electrochromic materials are usually divided in two main
groups: cathodic, e.g. Nb
2O3, V2O5, MoO3, WO3, and
anodic, e.g. CoO
XHY, RhO2, IrOXHY, NiOXHY. A most
common feature of these materials is the electrochemical
mechanism involving coupled insertion/extraction of
electrons and ionic species. Polymers like polyaniline, can
be also used as electrochromic materials.
The key issues for the development of effective
electrochromic devices are good handling, high
colorization ability (high contrast between the colored and
transparent states), reversibility of the
colorization/bleaching electrochemical process and
effective color maintenance, i.e. high coloration
efficiency. A further drawback hindering the development
of this technology is the need to develop materials which
can be easily deposited as homogeneous films conductive
substrate.
A typical electrochromic cell correspond to a
layered structure consisted of stacked glasses, transparent
conductive substrates, electroactive materials, electrolyte
and ion-conductive layers enhancing ion exchange
between them. Usually, both electrodes exhibit
electrochromic features though one electrochromic
electrode is sometimes replaced by a transparent ion-
storage layer. All elements of the electrochromic cell must
exhibit high optical transparency. In the specific case of
“Smart” mirrors with variable reflective ability, one glass
is replaced by a mirror.
For many years, nickel (oxy) hydroxide [12-15]
has been considered as a perspective electrochromic
electrode material. The electrochemical process with
colorization is assumed to follow:
Ni(OH)2↔ NiOOH + H+ + e- (1)
Transparent state Colored state
The electroactive material is usually synthesized
in the reduced form. Different methods can be used for
obtaining nickel hydroxide thin films: electrochemical
deposition from Ni salts solution, dip-coating, vacuum
evaporation, pulsed laser or chemical vapor deposition,
spray pyrolysis, sol–gel process and chemical bath
deposition [16-18]. However the electrochemical
deposition appears to be more efficient, since the thickness
and structure of the films can be controlled by the current
density and electrolyte composition.
Both anodic and cathodic electrochemical
deposition of nickel hydroxide have been previously
reported [19-30]. Anodic-deposition is based on the
preliminary decomposition of nickel ammonia complexes
by anode acidifying the electrolyte [29, 30]. Cathode
deposition consists in the precipitation of nickel hydroxide
from solutions of nickel salts with high solubility e.g.
sulfate, chloride and nitrate. Different initial pH has been

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3963
used, depending on the electrolysis condition.
Independently on the electrochemical condition, these
previous studies highlight the main drawback of poor
adhesion and mechanical properties of the deposited film.
Thus, in [19] mentioned “The precipitate formed in the
cathode chamber was filtered…. It is clear, that
cathodically formed Ni(OH)2 peels off due to weak
adhesion. Also “The mechanical rigidity was poor, and the
films easily flaked off the substrate” [24]. “In the light
micrograph an electrochemically precipitated α-Ni(OH)2
film are shown. The surface visibly cracked when the film
was dried.” [31]. Surface cracking is a result of high
internal mechanical stress of the film [32]. Especially, low
adhesion and high internal mechanical stress of the film
lead to visible cracks in thick films of nickel hydroxide
[19, 24, 31, 32]. These facts do not allow depositing
flexible electrochromic films. It is clear that without any
suitable post-electrodeposition treatment or additives, the
electrodeposited films of pure Ni(OH)2 do not exhibit the
proper features for electrochromic application. First, to
solve this issue, several authors increased the temperature
of the thermal treatment in order to convert the pristine
Ni(OH)2 into NiXOY oxide, thus expecting to improve the
hardness and adhesion of the film. But such high
treatments are expensive at the industrial scale and, most
important, resulted in the degradation of the
electrochromic properties [22, 26]. Others have chosen to
skip the drying steps at all [27].
This way is quite irrational because it is
impossible to set up the final electrochromic device
without electrode drying. In other words, the process of
deposition and drying of Ni(OH)2 film cannot be
considered as separate stages of the device production,
they are strictly tied to the previous and next operations
e.g. preliminary treatment of conducting substrate,
washing, assembling with the counter-electrode, current
lead pasting, etc. In such case, inability to dry electrode
will be a great inconvenience for real production, not only
because of the technical issues related to the storage in
aqueous media but also of the stability of electrochromic
properties [33].
One of the potentially effective ways for solving
this issue is to use electrochemical template synthesis.
Template synthesis is widely used for synthesis of
different type of solids with controlled porosity and
morphology. For instance Tan et al. [41] reported a
micelle-templated mesoporous nickel hydroxide film
obtained from diluted surfactant solution. Needless to say
that in such a case, the extraction of the liquid template
after deposition yields a porous film which is not suitable
for electrochromic application. Since our goal is to
increase the film mechanical and adhesive properties, our
assumption is to use a template that would form a
composite film made of a polymeric network embedding
the Ni(OH)2 crystallites and that would remain in the film
after drying and temperature treatment. For template
synthesis from aqueous solutions, water soluble high
molecular compound must be used. The most interesting
substance for this purpose is likely the polyvinyl alcohol
(PVA) which is widely used as a porosity controlling
agent template for synthesis of mesoporous alumina [36],
hydroxyapatite crystallites (with sodium dodecyl sulfate)
[37], mesoporous MFI zeolite (as a secondary template)
[38], nanosized MgO [39], 3D-structured macroporous
oxides and hierarchical zeolite for catalysis purposes [40],
polypyrrole (PP) network (for ammonia gas sensor) [42].
In the later, a composite matrix PVA film was formed. It
also has been shown by Gu et al. [43] that the addition of
PVA improves the adhesion of anodized aluminum oxide
onto indium-tin oxide surface.
In the present work, we aim to investigate the
electrochemical template synthesis of Ni(OH)2/PVA
composite films with improved mechanical and adhesion
features while maintaining good electrochromic
characteristics. The influence of the electrolyte
composition, the electrochemical deposition conditions
and drying temperature on the structure, electrochemical
and electrochromic properties of the so-obtained nickel
hydroxide/PVA film is reported [44. 45].
2. EXPERIMENTAL
2.1 Formation of nickel hydroxide films.
Polished nickel foils were used as substrate for all
the deposited nickel hydroxide/PVA film, as reported in
[27]. The interest of using such a substrate is dual. First,
nickel foils have higher conductivity, i.e. compared for
instance to ITO substrates. This property is expected to
yield a more homogeneous distribution of the current
density at the substrate surface and, thus, a more
homogeneous nickel hydroxide deposit. Second, polished
nickel substrate allows higher sensibility when recording
the optical parameters of the electrochromic film, thanks
to its higher light absorption due to the double ray
crossing the Ni(OH)2 layer (light source → Ni(OH)2 film
→ mirror-like Ni substrate→ Ni(OH)2 film → light
detector).
Electrochemically polished nickel foil substrates
have been prepared under the following conditions:
electrolyte with 520 g/l H3PO4, 40 g/l CrO3, and 550 g/l
H2SO4; current density of 50 A/dm2; temperature 80 °C,
treatment time up to 10 min.
All films of nickel hydroxide were
electrochemically deposited at 20°C during 80 min in a
diaphragm cell with 1M Ni(NO3)2 and 1 M KNO3 in the
cathode and anode space respectively. Pure Ni(OH)2 and
composite Ni(OH)2/PVA films were deposited at different
current densities: 0.313, 0.625, 1.25, 2.5 and 5, mA/cm2. A
nickel foil was used as anode. Polyvinyl alcohol (PVA)
was used as non-extractable template. Investigated PVA
concentrations were 1, 3, 5, 7 and 10 wt %. After
deposition, the samples were rinsed by distillated water
during 1 hour by immersion and then dried at 20°C or 90
°C during 24 hours.
2.2 Characterization
The preliminary testing of the films obtained with
templates was carried out by optical observation, in order
to assess the transparency and homogeneity, i.e. the
absence of cracks. The optical observation was carried out

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3964
in transmitted light mode with a Bresser digital
microscope (Germany) with a magnification up to 350.
The film morphology was also investigated by SEM and
ASM, using a РЕММА 120-02 scanning electron
microscope (Russian Federation) and atomic-force
microscope NT-MTD «NTegra» (Russian Federation). For
recording SEM images, each sample was covered with a
thin film of platinum few nm thick. The crystallographic
structure was analyzed as a function of the deposition
current density by XRD with a DRON-3 diffractometer
(Russian Federation) (Co-Kα radiation, range 10-90° 2,
step resolution 0.1°2, acquisition time per step 1 s).
Chemical composition was studied by EDX analysis with
a Hitachi S4500 microscope (Japan).
Electrochemical and optical properties were
investigated under cyclic voltammetry conditions by in
situ colorization-bleaching measurements. A schematic
representation of the experimental set-up is reported in
Figure-1. A “Elins” P-8 potentiostat (Russian Federation)
was used for the electrode potential control. Optical
measurements were carried out with an analog-to-digital
E-154 device. The reference electrode was Ag/AgCl (KCl
sat.). The cycling potential range was [+200 mV; +750
mV] vs. NHE. The light source was a non-monochromatic
white light emitted diode powered by a constant voltage.
The brightness of the reflected beam was recorded by
means of a light detector connected to the analog-to-digital
device. A light resistor with optical system was used as
light detector.
3. RESULTS AND DISCUSSIONS
3.1 Optical and structural characterization of the
reference materials obtained without template
For formation of advanced composite
Ni(OH)2/PVA film, optimization of the conditions of the
nickel hydroxide deposition has been carried out. For this,
influence of the deposition current density on structure,
surface morphology and transparency of pure Ni(OH)2
film has been investigated.
All the samples which were synthesized from
Ni(NO3)2 solution without template are observed to flake
off during drying. Figure-2 compares optical images from
the same sample (deposited at 0.625 mA/cm2) before and
after drying at 20° C. A network of cracks can be clearly
observed after drying. Light refraction at the edges is a
further evidence of the presence of Ni(OH)2 flakes that
lost contact with substrate. The experimental conditions
used here are similar to those used by others [24, 31, 32]
and confirm that pure nickel hydroxide films do not stick
well onto the substrate and exhibit high internal
mechanical stress.
XRD patterns reported in Figure-3 for the films
obtained at different deposition currents, are characteristic
of badly crystallized materials. All patterns correspond to
poorly ordered -phase and can be indexed according to
the rhombohedral system with the P3 structural type (see
[34]). The structure can be depicted with a hexagonal cell
[31], where the d(001) distance leads to the value of the
interlayer distance which is observed to increase with the
deposition current, from 5.5 ± 0.5 to 8.5 ± 0.5 Å. This
behavior can be explained by the local concentration of
OH- at the electrode surface during the synthesis, which
depends both on the current density and on the thickness
of the hydroxide film already deposited. The complex
interplay between these two parameters leads to better
defined -phases containing water, nitrate and carbonate
anions in the interlayer space when the current density is
higher. At the lower current density, even less crystallized
materials are obtained, whose structural disorder results
from a predominantly -type framework interstratified
with a lower percentage of -type motifs. According to the
work of Rajamathi et al. [35], the -like motifs percentage
could approach 50 % for the deposit obtained at the lower
current, 0.3125 mA/cm2. It should also be noted that low
crystallinity could arise from the turbostratic disorder
often affecting lamellar materials i.e. the random rotation
and/or translation of the individual -O-Ni- layers relative
to each other which leads to the selective broadening of
the non-hk0 peaks.
Optical images of these pure Ni(OH)2 film
deposited without template that peeled off from the
substrate, are reported in Figure-4. It can then be clearly
observed that the increase of current density leads to the
decrease of the film transparency because of the
appearance of particles agglomerates (see Figure-4e and
4f). Such a phenomenon is presumably due to the local
OH- concentration during deposition which increases with
the current density. At high currents, the early stages of
the nickel hydroxide deposition process are faster,
resulting in heterogeneous films (i.e. high surface
roughness). Once the hydroxide deposit attains a certain
thickness, the electrode surface becomes less conductive
and the OH- formation rate is slower. The precipitation
process then results in a more homogeneous films.
Proof of this mechanism could be found in the
fact that roughness always appears at the film side in
contact with the Ni substrate. Therefore, the deposition
process carried out at 0.625 mA/cm2 corresponds to the
best compromise between good transparency and
relatively short deposition time and hence will be used in
the following experiments. For comparison, it should be
pointed out that 0.625 mA/cm2 in our experimental
conditions corresponds to experiments at 0.3 mA reported
in [20].
It should be noted that weak adhesion to the
substrate and cracks emergence after film drying in all the
above experiments has been observed, thus confirming the
previous studies reported in the literature.
3.2 Studying template concentration
Different concentrations of PVA have been
studied. Addition of 1 and 3% wt PVA to Ni(NO3)2
solution allowed to obtain homogeneous and transparent
films but they still not adhere enough on the Ni substrate.
5 % wt PVA addition is found to be the optimum for both
optical and adhesion properties. At higher concentration of
PVA, solution’s viscosity becomes too high and affects

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3965
film homogeneity.
3.3 Investigation of the nickel hydroxide/PVA
composite film samples with 5 % wt template addition
For understanding the influence of PVA addition
as a template in electrolyte on structure, the XRD patterns
of Ni(OH)2/PVA films on substrate were obtained. All
earlier XRD patterns was obtained for flakes Ni(OH)
2
precipitated without template, since it was easily separated
from substrate. However, in case of precipitation in the
presence of 5% PVA, adhesion of films was extremely
high and internal mechanic stress was low, so the film
could not be peeled off easily. Therefore, XRD
experiments were carried out while the films were
remained attached to the substrate (Figure-5a). For
comparison, XRD pattern of the substrate was also
recorded and showed two high peaks at 52 and 62°
characteristic of the Ni metal (Figure-5b). It can be seen
from Figures 3 & 5a that films deposited with and without
PVA exhibit very different behaviors since it is clear that
the template formation yields amorphous material (Figure-
5a). This result is based on the mechanism of the template
synthesis: when substrate immerse to electrolyte, template
forms the 3D network on the substrate surface. During
electrolysis Ni(OH)2 nanoparticles are growing in the cell
of this 3D network, as described in [40] and visualized in
Figure-6. Figure-7 compares the surface morphology of
two films, both deposited from 1 M Ni(NO3)2 solution
with 5% PVA but at different current densities and
different deposition time, i.e. 0.625 mA/cm2 during 80
minutes (Figure-7a) and 1.25 mA/cm2 during 40 minutes
(Figure-7b). The film surface is flat though showing
cracks. It can be assumed that this morphology is caused
by local mechanical stress occurring during the drying
step.
Assuming that crack depth corresponds to film
thickness, the thickens of film deposited at 0.625 mA/cm2
can be calculated from SEM image, based on
representation in Figure-8 using following equation:
t
tgbv 60
)( 

(2)
where b is the shadow length, β the beam angle and t the
electrode position time. Providing that b=3 μm, β=60 °and
t=80 min, equation (2) leads to v=3.87 µm∙h-1.
The deposition rate calculated using equation (3)
from [21], under our experimental conditions, is 3.16
µm∙h-1. As a result we can ascertain good corresponds
under both values. The minor difference can be explained
by the presence of PVA inside the composite film, as
attested by EDX analysis reported in Table-1 (see the
carbon % weight).
The AFM images of Ni(OH)2 film deposited at
0.625 mA/cm2 during 80 minutes are shown in figures 9a
and 9b. It can be seen that the surface of our nickel
hydroxide film is rather rough. The maximal roughness
height is about 110 micrometers.
It is well known that nickel foil surfaces are
covered by a thin oxide layer (10-30 nm). In alkaline
media, it forms nickel (oxy) hydroxides which can
contribute to the electrochromic behavior of the electrode.
In order to verify the contribution of the nickel substrate to
the electrochemical and colorization ability of the
electrode, optical measurements coupled to cyclic
voltammetry have been carried out on the pristine
substrate (Figure-10a). The electrochemical and optical
activities of the hydroxide surface layer are very low. Only
a weak, gradual darkening can be observed (see Figure-
10b). It can then be concluded that the contribution of the
substrate is negligible when studying the electrode with
the electrochemically deposited hydroxide/PVA film.
Electrochemical & electrochromic properties of
the nickel hydroxide/PVA films, electrodeposited by
template synthesis and dried under different temperatures,
are reported in Figures 11 and 12. Both figures show the
behavior of the samples obtained from 1 M Ni(NO)3
solution with 5% weight PVA and deposited under 0.625
mA/cm2. Figure-11 corresponds to the sample dried at 90
°C during 24 h and Figure-12 to the sample dried at 20°C
during 24 h.
Both films exhibit higher electrochemical activity
than that of the substrate alone (compare Figures 11a and
12a to Figure 10a). Most important, the sample dried at 20
°C exhibits a higher electrochemical activity, i.e. current
of the charge and discharge peaks is 4.2 mA and 3.9 mA
respectively (Figure-12a), than the samples dried at 90°C,
i.e. the charge and discharge peaks equal 2.9 mA and 2.75
mA respectively (Figure-11a). It should be noted that the
charge-discharge curves of the sample dried at 90°C
shows no clearly defined charge peaks as compared with
the sample dried at 20°C. Thus, it should be concluded the
Ni(OH)2/PVA film dried at 20°C shows a better optical
response during electrochemical cycling, i.e. larger
colorization depth (compare Figures 11b and 12b).
However the sample dried at 90°C exhibits a larger
colorization/bleaching reversibility. The sharp difference
between the transparency plots of the samples dried at 90
and 20°C can be readily seen on Figures 11 and 12. For
the sample dried at 90 °C, the shape of the optical change
is almost perfectly rectangular. As for the sample dried at
20°C, despite the higher degree of colorization-bleaching
change, the optical response shows dips after colorization
and before bleaching (see Figure-12b). This effect is very
interesting and requires a deeper investigation.
The different optical behaviors of the films dried
at 20° and 90° C could be related to the influence of PVA
on the morphology of the film. The EDX analysis attests
the presence of PVA in the deposited film. It is therefore
likely that the presence of PVA which is an insulating
material significantly modifies the conductivity
homogeneity of the film. The drying process at 90 °C may
induce a (partial) sub-melting of the PVA sub-network
which affects/reduces the open-cellular structure induced
by the polymer template grid and, consequently, leads to a
tighter encapsulation of the nickel hydroxide particles
resulting in degradation of the film's conductivity. The
other reason could be the partial dehydration of the

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3966
Ni(OH)2 particles also leading to an overall decrease of
conductivity.
Figure-1. Scheme of the experimental cell for coupled electrochemical and optical measurements. 1 - the non-conducting
coating with black color deposited on the working electrode; 2 - transparent cell case; 3 - the surface of the working
electrode with electrochromic film; 4 - the counter electrode; 5- focused light source; 6 - photoresistor (I- input from
stabilized power source; II - output to analog-to-digital device connected to PC). The reference electrode is not shown.

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3967
Figure-2. Optical images of Ni(OH)2 films deposited from Ni(NO3)2: (a) after deposition; (b) after drying.
Figure-3. XRD patterns of non-doped nickel hydroxide films electroplated under different
current densities (as indicated in the figure).


VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3968
Figure-4. Optical images of Ni(OH)2 films deposited under different current densities and
separated from electrode: (a, b) at 0.313 mA/cm2, (c, d) 2.5 mA/cm2, (e,f) 5 mA/cm2.
Figure-5. XRD patterns of nickel hydroxide film with substrate electroplated at 0.625 mA/cm2
from electrolyte with 5% PVA and electrochemically polished nickel substrate.

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3969
Figure-6. Visualization of the mechanism of electrochemical template synthesis of Ni(OH)2/PVA film:
a - 3D network of PVA (as a template) on the substrate surface; b - composite film, consists of PVA
matrix and nickel hydroxide particles as electrochromic. (gray fibers - PVA, green crystals - Ni(OH)2)

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3970
Figure-7. SEM Images of Ni(OH)2 films deposited at 1.25 (a) and 0.625 (b) mA/cm2 onto
the nickel substrate by template synthesis.
Figure-8. Dropping shadow scheme of the nickel substrate.

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3971
Figure-9. AFM images of Ni(OH)2 film deposited at and 0.625 mA/cm2 onto the nickel
substrate by template synthesis.

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3972
Figure-10. (a) Cyclic voltammetry and (b) colorization curve of the nickel substrate without electrochromic deposited
film. The blue line is just to guide the eyes and to indicate the potential at which the color change occurs, i.e. xxx mV.

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3973
Figure-11. (a). cyclic voltammetry and (b) colorization curve of electrode with electrochromic
film, deposited by template synthesis and dried at 90°C.

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3974
Figure-12. (a). cyclic voltammetry curve and (b) colorization curve of electrode with
electrochromic film deposited by template synthesis and dried at 20°C.
Table-1. Elementary analysis according to EDX for nickel hydroxide film with substrate electroplated
at 0.625 mA/cm2 from electrolyte with 5% PVA
Element Weight % Weight % Error Atom % Atom % Error
C 9.57 +/- 0.43 31.55 +/- 1.43
O 4.14 +/- 0.19 10.25 +/- 0.48
Co 0.14 +/- 0.22 0.09 +/- 0.15
Ni 86.15 +/- 1.23 58.11 +/- 0.83
Total 100.00 100.00

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3975
4. CONCLUSIONS
It has been shown that the pure Ni(OH)2 films
obtained by electrochemical deposition after drying
exhibits , cracks and demonstrating very weak adhesion to
the substrate. This outcome confirms all the data
previously reported in the literature. On the contrary, it is
demonstrated the use of PVA template electrochemical
synthesis yields nickel hydroxide/PVA composite films
having high plasticity, effective adhesion to substrate and
good optical and electrochemical properties. The
optimization of advanced Ni(OH)2/PVA composite films
deposition, has been carried out. The influence of the
deposition current density on structure, surface
morphology and transparency of pure Ni(OH)2 film has
been investigated first. It has been established that optimal
current density of 0.625 mA/cm2 was the best compromise
for obtaining a film with good transparency while
maintaining the deposition time short enough, i.e. 80 min.
for a 5.16 µm thick film. Overall, the films deposited with
PVA template method exhibit an amorphous X-ray
structure which can be assumed to arise from the Ni(OH)2
particle constrained growth in the nano-size cells of the 3D
network of the template. The optimal concentration of
PVA was determined to be 5% wt. in the deposition
solution. The rate of electrode position by template
synthesis in the presence of PVA was estimated to be
about 3.87 μm/h at the current density of the 0.625
mA/cm2 in accordance with the data reported elsewhere. It
was also observed by EDX analysis, that PVA is well
incorporated inside the nickel hydroxide film. By means of
a electrochemical/optical coupled experiment it has been
established that the presence of PVA had no negative
effect on electrochemical (charge/discharge) activity and
optical (coloring/bleaching) reversibility. The
electrochromic properties of the composite PVA/Ni(OH)2
films, deposited by electrochemical template synthesis and
dried at 20 °C and 90 °C were also investigated. It has
been shown that both temperature treatments yield films
with good properties (charge/discharge and colorization-
bleaching processes). However, it can be noted that films,
dried at 20°C, exhibit the better electrochemical properties
and higher colorization degree, while the reversibility of
the colorization/bleaching process is better for the sample
dried at 90 °C.
ACKNOWLEDGEMENTS
This study was carried out in frame of an
international collaboration agreement between University
Montpellier (Montpellier, France), Ukrainian State
University of Chemical Technology (Dnipropetrovsk,
Ukraine), and Vyatka State University(Kirov, Russian
Federation) no. 130585 from July 7, 2013. V.A. Kotok is
grateful to the French Embassy in Kiev for its financial
support.
REFERENCES
[1] Niklasson G.A., Granqvist C.G. 2007.
Electrochromics for smart windows: thin films of
tungsten oxide and nickel oxide, and devices based on
these. J. Mater. Chem. 17: 127-156.
[2] Wang J., Sun X.W., Jiao Z. 2010. Application of
Nanostructures in Electrochromic Materials and
Devices: Recent Progress. Materials. 3: 5029-5053.
[3] Gillaspie D.T., Tenent R.C., Dillon A.C. 2010. Metal-
oxide films for electrochromic applications: present
technology and future directions. J. Mater. Chem.
209585-9592.
[4] Tajima K., Hotta H., Yamada Y., Okada M.,
Yoshimura K. 2011. Surface Analysis of
Electrochromic Switchable Mirror Glass Based on
Magnesium-Nickel Thin Film in Accelerated
Degradation Test. Materials Transactions. 52: 464-
468.
[5] Pawlicka A. 2009. Development of Electrochromic
Devices. Recent Pat. Nanotechnol. 3: 177-181.
[6] Masaya C., Ishikawa M. 1994. Enhanced
Electrochromic Property of Nickel Hydroxide Thin
Films Prepared by Anodic Deposition. J.
Electrochem. Soc. 141: 3439-3443.
[7] Monk P.M.S., Ayub S. 1997. Solid-state properties of
thin film electrochromic cobalt–nickel oxide, Solid
State Ionics. 99: 115 -124.
[8] Monk P.M.S., Mortimer R.J., Rosseinsky D.R. 1984.
Electrochromism: Fundamentals and Applications,
VCH, Weinheim, New York, Basel, Cambridge,
Tokyo.
[9] Monk P.M.S., Mortimer R.J., Rosseinsky D.R. 2007.
Electrochromism and electrochromic devices,
Cambridge University Press, The Edinburgh Building,
Cambridge, UK.
[10] Gomathi H., Jayalakshmi M., Joseph J., Vittal R.
2003. Electrochemistry in electrochromism-
manifestation by transition metal oxides. Bull.
Electrochem. 19: 09-16.
[11] Kadam L.D., Pawar S.H., Patil P.S. 2001. Studies on
ionic intercalation properties of cobalt oxide thin
films prepared by spray pyrolysis technique. Mater.
Chem. Phys. 68: 280-282.
[12] Sharma P.K., Fantini M.C.A., Gorenstein A. 1998.
Synthesis, characterization and electrochromic
properties of NixOHy thin film prepared by a sol-gel
method. Solid State Ionics. 113-115: 457-463.

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3976
[13] Svensson J.S.E.M., Granqvist C.G. 1987.
Electrochromism of nickel-based sputtered coatings.
Sol. Energy Mater. 16: 19-26.
[14] Svensson J.S.E.M., Granqvist C.G. 1986.
Electrochromic hydrated nickel oxide coatings for
energy efficient windows: Optical properties and
coloration mechanism. Appl. Phys. Lett. 49: 1566-
1568.
[15] Ahn K.S., Nah Y.C., Sung Y.E. 2002. Surface
morphological, microstructural, and electrochromic
properties of short-range ordered and crystalline
nickel oxide thin films. Appl. Surf. Sci. 199: 259-269.
[16] Vidotti M., Cуrdoba de Torresi S.I. 2009.
Electrostatic layer-by-layer and electrophoretic
depositions as methods for electrochromic
nanoparticle immobilization. Electrochim. Acta. 54:
2800-2804.
[17] Alkahlout A. 2006. Electrochromic properties and
coloration mechanisms of sol-gel NiO-TiO2 layers
and devices built with them, Dissertation,
Saarbrücken.
[18] Vaezi M.R., Sadrnezhaad S.K. 2008. Two-stage
chemical deposition of oxide films. Int. J. Eng., Trans.
B. 21: 65.
[19] Jayashree R.S., Vishnu Kamath P. 1999. Factors
governing the electrochemical synthesis of a-nickel
(II) hydroxide. J. Appl. Electrochem. 29: 449-454.
[20] Fomanyuk S.S., Krasnov Y.S., Kolbasov G.Y. 2013.
Kinetics of electrochromic process in thin films of
cathodically deposited nickel hydroxide. J. Solid State
Electrochem. 17: 2643-2649.
[21] Streinz C.C., Hartman A.P., Motupally S., Weidner
J.W. 1995. The Effect of Current and Nickel Nitrate
Concentration on the Deposition of Nickel Hydroxide
Films. J. Electrochem. Soc. 1424: 1084-1089.
[22] Umeokwonna N.S., Ekpunobi A.J., Ekwo P.I. 2015.
Effect of cobalt doping on the optical properties of
nickel cobalt oxide nanofilms deposited by
electrodeposition method. International Journal of
Technical Research and Applications. 3(4): 347-351.
[23] Sonavane A.C., Inamdar A.I., Shinde P.S., Deshmukh
H.P., Patil R.S., Patil P.S. 2010. Efficient
electrochromic nickel oxide thin films by
electrodeposition. J. Alloys Compd. 489: 667-673.
[24] Ragan D.D., Svedlindh P., Granqvist C.G. 1998.
Electrochromic Ni oxide films studied by magnetic
measurements. Sol. Energy Mater. Sol. Cells. 54: 247-
254.
[25] Fantini M., Gorenstein A. 1987. Electrochromic
nickel hydroxide films on transparent/conducting
substrates. Sol. Energy Mater. 16: 487-500.
[26] Chia-Ching L. 2012. Lithium-driven electrochromic
properties of electrodeposited nickel hydroxide
electrodes. Sol. Energy Mater. Sol. Cells. 99: 26-30.
[27] Carpenter M.K., Corrigan D.A. 1989.
Photoelectrochemistry of nickel hydroxide thin films.
J. Electrochem. Soc. 136(4): 1022-1026
[28] Provazi K., Giz M.J., Dall’Antonia L.H., Cordoba de
Torresi S.I. 2001. The effect of Cd, Co, and Zn as
additives on nickel hydroxide opto-electrochemical
behavior. J. Power Sources. 102: 224-232.
[29] Chigane M., Ishikawa M. 1994. Enhanced
electrochromic property of nickel hydroxide thin films
prepared by anodic deposition. J. Electrochem. Soc.
141(12): 3439-3443.
[30] Natarajan C., Ohkubo S., Nogami G. 1996. Influence
of film processing temperature on the electrochromic
properties of electrodeposited nickel hydroxide. Solid
State Ionics. 86-88: 949-953.
[31] Hall D. S., Lockwood D. J., Bock C., MacDougall B.
R. 2015. Nickel hydroxides and related materials: a
review of their structures, synthesis and properties.
Proc. R. Soc. A. 471(2174): 20140792.
[32] Hall D.S., Lockwood D.J., Poirier S., Bock C.,
MacDougall B.R. 2012. Raman and Infrared
spectroscopy of α and β phases of thin nickel
hydroxide films electrochemically formed on nickel.
J. Phys. Chem. A. 116: 6771-6784.
[33] . Kotok V.A, Koshel N.D., Kovalenko V.L., Malishev
V.V. 2007. Nickel hydroxide ageing in different
medias and its influence on electrochemical behavior
in composition nickel electrode. 8th Advance
Batteries and Accumulators, Brno.
[34] Guerlou-Demourgues L., Denage C., Delmas C. 1994.
New manganese-substituted nickel hydroxides: Part 1.
Crystal chemistry and physical characterization. J.
Power Sources. 52: 269-274.

VOL. 12, NO. 13, JULY 2017 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
3977
[35] Rajamathi M., Kamath P. V., Seshadri R. 2000.
Polymorphism in nickel hydroxide: role of
interstratifications. J. Mater. Chem. 10: 503-506.
[36] Ecsedi Z., Lazău I. and Păcurariu C. 2007. Synthesis
of mesoporous alumina using polyvinyl alcohol
template as porosity control additive. Process. Appl.
Ceram. 1(1-2): 5-9.
[37] Pon-On W., Meejoo S., Tang I.-M. 2008. Formation
of hydroxyapatite crystallites using organic template
of polyvinyl alcohol (PVA) and sodium dodecyl
sulfate (SDS). Mater. Chem. Phys. 112(2): 453-460.
[38] Miyake K., Hirota Y., Uchida Y. et al. 2016.
Synthesis of mesoporous MFI zeolite using PVA as a
secondary template. J. Porous Mater. 23(5): 1395-
1399.
[39] Wanchanthuek R., Thapol A. 2011. The Kinetic Study
of Methylene Blue Adsorption over MgO from PVA
Template Preparation. Journal of Environmental
Science and Technology. 4: 552-559.
[40] Parkhomchuk E. V., Sashkina K. A., Rudina N. A.,
Kulikovskaya N. A., Parmon V. N. 2013. Template
synthesis of 3D-structured macroporous oxides and
hierarchical zeolites. Catal. Ind. 5(1): 80-89.
[41] Tan Y., Srinivasan S., and Choi K.-S. 2005.
Electrochemical Deposition of Mesoporous Nickel
Hydroxide Films from Dilute Surfactant Solutions. J.
Am. Chem. Soc. 127: 3596-3604.
[42] Kabita B., Mausumi D., Deepali S. 2015. Polypyrrole
Nanonetwork Embedded in Polyvinyl Alcohol as
Ammonia Gas Sensor. Res. J. Chem. Sci. 5(5): 61-68.
[43] Gu W., Liao L.S., Cai S.D., Zhou D.Y., Jin Z.M., Shi
X.B., Lei Y.L. 2012. Adhesive modification of
indium–tin-oxide surface for template attachment for
deposition of highly ordered nanostructure arrays.
Appl. Surf. Sci. 258: 8139-8145.
[44] Kotok V.A., Kovalenko V.L., Ananchenko B.А.,
Levko E.N. 2014. The deposition of electrochromic
film based on nickel hydroxide by electrochemical
method. XV International scientific conference «New
Technologies and achievements in metallurgy,
materials engineering and production engineering»,
Materials Engineering, Czestochowa, Poland,
Collective Monografie.
[45] Kotok V.A., Malahova E.V., Kovalenko V.L.,
Baramzin M.N., Kovalenko P.V. 2016. Smart
windows: cation internal and anion external activation
for electrochromic films of nickel hydroxide.
Promising Materials and Processes in Technical
Electrochemistry, Monograph, KNUTD, Kyiv.