Electrochemical preparation of the Ti/Ni-Sb-SnO2 for removal of phenol, in situ generated ozone

Article abstract of DOI:10.13005/ojc/340219

This present study aims to reveal the performance of Ti/Ni-Sb-SnO₂ in limiting oxygen evolution and increasing electrochemical O3 production (EOP) and phenol removal. First, the effect of important variables such as current density (CD), charge

Full text of DOI:10.13005/ojc/340219

ISSN: 0970-020 X
CODEN: OJCHEG
2018, Vol. 34, No.(2):
Pg. 757-763
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
www.orientjchem.org
Electrochemical Preparation of the Ti /Ni-Sb-SnO2
for Removal of Phenol, In situ Generated Ozone
ALI REZA RAHMANI1,DAVOOD NEMATOLLAHI2, MOHAMADTAGHI SAMADI1,
MOHAMAD REZA SAMARGHANDI1 and GHASEMAZARIAN1*
1Department of Environmental Health Engineering, Faculty of Health and Research Center
for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran.
2Faculty of Chemistry, Bu-Ali-Sina University, Hamadan, Zip Code 65174, Iran.
*Corresponding author E-mail: gh_azarian@yahoo.com
http://dx.doi.org/10.13005/ojc/340219
(Received: December 14, 2017; Accepted: January 20, 2018)
ABSTRACT
This present study aims to reveal the performance of Ti/Ni-Sb-SnO2 in limiting oxygen
evolution and increasing electrochemical O3 production (EOP) and phenol removal. First, the
effect of important variables such as current density (CD), charge passed and electrolyte type on
the modified electrodes was investigated. Then, phenol removal by Ti/Ni-Sb-SnO2 was studied
using the effect of CD, retention time and phenol concentration. The results revealed that for
building the electrodes of Ti/Ni-Sb-SnO2, CD of 3.9 mA/cm2 and passed charge of 180 mC were
obtained. The performance of ozone generation in HClO4 is by far more than that of H3PO4, H2SO4
and HCl. At the initial concentration of 1, 3, 6 and 10 mM, phenol was decomposed by 99.9%
approximately in current densities of 61.5, 76.9, 92.3 and 123.1 mA/cm2 and contact time of 150,
250, 350, and 400 minutes. respectively.
Keywords: Phenolic Wastewater, Electrochemical treatment, Modified electrode,
Constant electrolysis.
INTRODUCTION
entered into sewages and as a result into the water
resources2-4. Advanced oxidation processes (AOPs)
have widely and effectively been applied for the
treatment of these types of sewages especially for
non-biodegradable sewages5,6. Among AOPs,
advanced electrochemical oxidation processes
using dimensionally stable anode electrodes have
been of much interest 7-9. They have been widely
These days, a large amount of sewage
containing toxic hard decomposable materials are
discharged into the environment and water
resources and are considered a serious threat to
living organisms and human health1,2. Among the
toxic materials, phenolic compounds are widely
This is an
Open Access article licensed under a Creative Commons Attribution-NonCommercial-ShareAlike
4.0 International License (https://creativecommons.org/licenses/by-nc-sa/4.0/ ), which permits unrestricted
NonCommercial use, distribution and reproduction in any medium, provided the original work is properly cited.

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AZARIAN et al., Orient. J. Chem., Vol. 34(2), 757-763 (2018)
used due to their simplicity, easy operation, low dimensionally stable anode, Ni-Sb-SnO2, etc, have
initial investment cost and high efficiency. These been used9,11,15. BDD and Ni-Sb-SnO2 have been
electrodes have effectively been used in the removal introduced as the only electrodes with high
and mineralization of organic materials because of
the production of oxidizing agents like hydroxyl
performance for ozone generation in some new
studies9,11,15,17-18; it should be noted that BDD is an
expensive electrode that is considered a
disadvantage in terms of commercial and industrial
uses. Also, Ni-Sb-SnO2 is well coated thermally
on different electrodes like titanium15. The
electrochemical production is highly dependent on
the contact between O2 molecules and O•, which
requires active surface. Thus, in comparison with
the thermal deposition method, in electrochemical
process the surface is entirely and smoothly
deposited.
radicals, ozone, etc10-12
.
The use of ozone in water and industrial
and urban wastewater treatment has lately been
growing due to its green oxidizing function, and it is
ultimately converted into O2. It also does not leave
any Harmful byproducts13-15. Ozone is mainly
generated by four ways as follows: electric
discharge, photochemistry, cold plasma, and
electrochemistry, the most important of which is the
electric discharge method15,16 (reaction 1).
Hence, in present study, the electrochemical
method was applied to coat the Ti electrode with
Ni-Sb-SnO2. Furthermore, the effects of some
variables like CD, charge passed, and electrolyte
type (H2SO4, HClO4, HCl and H3PO4) on Ti/Ni-Sb-SnO2
perpetration were studied. The surface specifications
of the Ti/Ni-Sb-SnO2 electrode were carried out
using below measures, X-ray diffraction (XRD) and
scanning electron microscopy (SEM). In the
following, the Ti/Ni-Sb-SnO2 electrode was used for
removal of phenol at different contact time, CD and
concentrations of phenol.
2/3O2 → O3 (ΔHo298 = 34.1 Kcal)
(1)
Ozone should be generated in-situ as it is
highly activated in natural circumstances. As plenty
of variables such as oxygen source (air or pure oxygen),
ambient temperature and presence of impurities in
air steam affect ozone production by this process,
the efficiency is not more than 1-2% and 2-3% (wt%),
respectively, for dry air and net oxygen15,17. In spite
of production of O2 and O3 at the same time, the
efficiency of ozone production by means of
electrochemical ozone production (EOP) is a lot,
reported by 50% in various studies under different
conditions9. A number of great advantages of EOP
are as following: ozone generation at high
concentrations in gaseous or liquid phase with high
energy efficiency, no demand to a gas to be injected
or any other substances, simple design, direct
application of O3 in water stream and delete of mass
transfer difficulties from gaseous phase to liquid
phase, little applied potential and Ability to convert
consumed ozone residual into O2 and H2O9,11,15. In
EOP, the generation of oxygen is prohibited through
the careful control of the gender and morphology of
anode, anode potential, CD, temperature and type
of electrolyte. The following reaction shows the
mechanism of ozone generation on the surface of
the electrode.
MATERIALS AND METHOD
Chemicals
Phenol (>99% purity) was prepared from
Merck & Co. It was applied without additional
treatment and a stock solution with a definite
concentration was achieved and the working
solutions (1-10 mM) were studied (Fig. 1). All other
chemicals, including HCl, H2SO4, HClO4, H3PO4,
SbCl3, NiCl2.6H2O, SnCl4.5H2O, NaOH, C2H5OH,
CH3COCH3 and Na2SO4 were of analytical grade
and were obtained from Merck Co. & Sigma-Aldrich
Co.The volume of the catalyst coating solution used
for studying the behavior of the produced electrodes
and degradation of phenol were 30 and 50 cm3,
respectively.The catalyst coating solution containing
O2 + O• → O3
(2)
Different alloys and electrodes have been NiCl2.6H2O, SbCl3 and SnCl4.5H2O were dissolved
applied to produce ozone. To produce ozone, some in 50 cm3 ethanol with the ratio of 0.0238, 0.183
electrodes like Pt, Au, Pd, glassy carbon, PbO2, BDD, and 17.5 g, respectively.

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AZARIAN et al., Orient. J. Chem., Vol. 34(2), 757-763 (2018)
times in a container containing distillation water in
ultrasonic bath for 20 minutes.Then, the electrodes
were dried in an oven at 55 °C. Construction of Ti/
Ni-Sb-SnO2 and all phenol destruction experiments
were performed in an 80 cm3 cell.Two electrodes of
cathode and one anode made of stainless steel
and Ti/Ni-Sb-SnO2, respectively, with dimensions
of 10 cm × 2.2 cm were applied. The effective surface
of the anode was 48.5 cm2. All of the electrodes were
connected to a DC power supply (Aram Tronik Co, Iran).
Removal efficiency of the phenol (REP (%)) was
calculated by measuring the concentration before
and after the process by means of cyclic volt
ammeter (CV) techniques (Eq. 3)19.
Fig. 1. Calibration curve of phenol in different
concentrations
X i − X t
REP (%) =
× 100
(3)
X i
Preparation and coating of the electrodes and
Apparatus
where, Xi and Xt are, respectively, initial
and final concentrations of phenol. And, the
morphology and the crystallinity of the scratched
electro-deposited films of the Ti/Ni-Sb-SnO2 surface
were done by the following analyses: SEM, using a
Philips XL-30 and XRD, by using Thermo ARL
SCINTAG X’TRA, 45 kV.
To study the most important parameters
affecting the making of the Ti/Ni-Sb-SnO2 electrode,
the electrodes of Ti (2 mm in diameter) were initially
polished using sandpaper and then they were
washed by distilled water so as to remove impurities
and metals fully from the Ti surface. Then, in order
to clean and remove fat and residual materials in
the surface, the electrodes were cleaned using
alumina powder and then washed by using distilled
water. In the end, they were washed using acetone
and distilled water in order to prepare them for
coating. The double- step Charon-potentiometer
method was applied to build Ti/Ni-Sb-SnO2; here,
Ti, platinized titanium, and commercial saturated
Ag/AgCl were applied as the working, counter and
reference electrodes. To coat the electrodes and
study the efficiency of the coated electrodes, an
auto-lab device (Potentiostat /Galvanostat Auto-lab
PG STAT 20 model) was used. The effects of
important parameters on the modified electrodes
such as charge passed and CD were studied.
Moreover, to investigate the efficiency of Ti/Ni-Sb-
SnO2 linear sweeping volt-ammeter (LSV) method
was used in the presence of different contents of
various electrolytes (HCl, H2SO4, HClO4 and
H3PO4)11,15. To build large electrodes and remove
Phenol, at first, the electrodes of Ti (10 cm ×2 cm)
were polished with sandpaper and then they were
washed. Then, the electrodes were submerged in
acetone many times and then were washed by
distilled water. Then, they were boiled in 10% oxalic
acid for 25 min. Next, the electrodes were well
washed via distilled water and were placed four
RESULTS AND DISCUSSION
First, different variables of coating the
electrode: Ti with the catalyst of Ni-Sb-SnO2 and its
effect on ozone production were studied via the
LSV technique. Then, so as to find the best
condition for phenol removal, the effect of different
operating parameters such as CD, retention time
and phenol concentration were studied.
Preparation of theTi/Ni-Sb-SnO2
Effect of current density
In order to study the effect of CD on the
constant of 180 mC in the presence of 1M HClO4,
current densities ranging from 3.9 to 15.7 mA/cm2
were applied and the optimum amount of CD was
obtained. Fig. 2 shows the LSV of the uncoated
electrodes and Ti/Ni-Sb-SnO2 in 50 mV/S. As it is
observed, the onset potential reached from 1.02 V
vs Ag/Ag Cl for the unmodified electrode to 2.1 V vs
Ag/AgCl for the modified electrodes, which is by far
higher than the potential of O2 production (Eq. 4-6).
Therefore, in this case, the production of O2 is
restricted. Despite the fact that deposition leads to
higher potentials (from the onset potential), at
different current densities, as can be observed, at

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AZARIAN et al., Orient. J. Chem., Vol. 34(2), 757-763 (2018)
the constant charge passed of 180 mC, the results achieved in the stage of either CD or charge
modifying of the electrode is carried out better at passed, revealed that a layer with a better efficiency
low current densities and longer contact time and, is formed on the electrode via using low current
in turn, the built electrode has a suitable densities at constant passed charge.
performance. In high current densities for electrode
modification, the surface of the electrode is not
successfully modified; thus, the active surface
required for ozone generation is not formed
effectively. As a result, the modified electrode does
not have a good performance. Findings revealed
that the optimum amount of 3.9 mA/cm2 was
obtained. Although this CD demonstrated a steep
slope reflecting that oxygen evolution has been
restricted and more ozone is produces9 (Eq. 4-6).
→
←
2H2O
3H2O
O2 + 4H+ + 4e- Eo=1.23V vs.RHE (4)
O3 + 6H+ + 6e- Eo=1.51V vs.RHE (5)
→
←
+
-
o
→
H2O + O2
O3 + 2H + 2e E =2.07V vs.RHE
(6)
←
Fig. 3. Anodic polarization curves of Ti/Ni-Sb-SnO2
at different charge passed: in 3.9 mA/cm2 CD, at 1M
HClO4 and Scan rate 50mV/s in room temperature
Effect of electrolyte type
In this research, four types of acid: H2SO4,
HCl, H3PO4 and HClO4 were studied at CD of 3.9
mA/cm2 and charge passed of 180 mC. As is seen
in Fig.4, the LSV ofTi/Ni-Sb-SnO2 electrode at scan
rate of 50 mV/S in 1 molar solution of H2SO4, H3PO4,
HClO4 and HCl shows that in HClO4 the onset
potential shifts to higher potentials. Also, LSV steep
of Ti/Ni-Sb-SnO2 electrode is sharper compared to
other electrolyte. It can be attributed to the creation
of O3, as the main product of the reaction. This
product reacts with hydroxyl radical, which results
from water electrolyze, and produces HO3o playing
a basic role in ozone production9. According to our
literature review, the amount of electrochemical
Fig. 2. Anodic polarization curves of Ti/Ni-Sb-SnO2
at different CD: in 180mC charge passed, at 1M
HClO4 and Scan rate 50mV/s in room temperature
Effect of charge passed
To study the impact of charge passed for generation of ozone is not equal in various acidic
coating of the electrode, charge passed = 108-216 contents and environments and the nature of acid
mC was tested at CD of 3.9 mA/cm2. The LSV of the anions influences the selective adsorption of water
unmodified electrode and Ti/Ni-Sb-SnO2 in the on electrodes’ surface and, in turn, the performance
presence of 1M HClO4 have been demonstrated in of ozone production9,20. In a novel study where
Fig. 3. As it is observed, the onset potential for Ti various acids have been suggested for the
reached from 1.02 V vs Ag/AgCl to about 2.1 V vs electrochemical generation of ozone with various
Ag/AgCl whereas it shifted to above the O2 electrodes, it was revealed that percholeric Acid
production potential for Ti/Ni-Sb-SnO2. As it is had the highest efficiency with a performance higher
observed in Fig. 3, the use of charge passed above than 20%9. The results of present study are closely
180 mC for coating electrode results in decline in consistent with those of the mentioned study. Hence,
electrode efficiency in terms of limiting O2 to investigate other parameters, 1M of HClO4
production and ozone production. Overall, the solution was considered. In acidic environments,

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AZARIAN et al., Orient. J. Chem., Vol. 34(2), 757-763 (2018)
there is molecular ozone, but in basic conditions
ozone is converted to hydroxyl radical. Considering
that the nature of the electrolyte increases the
solution conductivity, as a result, more levels of
ozone are produced.
Fig. 4. Anodic polarization curves of Ti/Ni-Sb-SnO2
at different type of electrolyte: in 3.9 mA/cm2 CD,
180 mC charge passed, at 1M HClO4 and Scan rate
50mV/s in room temperature
Electrode surface studies
Fig. 5. (a and b) SEM images and (c) XRD pattern
of Ti/Ni-Sb-SnO2 (Modified in: 3.9 mA/cm2 CD,
180mC charge passed)
In order to generate more ozone in acidic
conditions, electrodes’ surface should be smooth
and stable. Fig. 5a and b demonstrates the image
of the modified Ti/Ni-Sb-SnO2 electrode, under the
optimal conditions obtained in previous sections:
CD of 3.9 mA/cm2, charge passed 180 mC.
Apparently, at high magnification the morphology
of the coated films on the Ti electrode consisting of
Sb, Sn and Ni were spherical. Considering that the
size of particles is described as a key parameter in
increasing surface active sites. The SEM results
show that the sized of deposited particles was
between 50.8 and 64.6 nm, indicative of the fact
that very small particles, at the level of nanometer,
cover all surface of the electrode, which is highly
effective in ozone generation. The elemental
analysis of the scratched electro-deposited films
was tested using XRD (Fig. 5c). The well-defined
crystallinity of the deposited films on the Ti electrode
was approved using the wide-angle PXRD pattern
compared to simulated patterns. As is seen, there
are at least 6 crystalline structures Sb, Sn, SnO2, Ti,
TiO2 and Ni. The dominant and sharp observed
Phenol removal
The modified electrode of Ti/Ni-Sb-SnO2
was used in the presence of 1 M perchloric acid for
phenol removal. Hence, the solution comprised of
phenol with the concentration between 1 and 10
mM was prepared and different current densities
and contact times were applied.
Effect of current density
It should be pointed that an increase in
CD is accompanied with more ozone generation
and consequently more phenol is removed. With
increasing ozone concentration in solution, mass
transfer from gases phase to liquid phase
containing the contaminant will enhance and
consequently the removal efficiency will improve.
Fig. 6 demonstrates the results of the effect of CD
(in the range of 15.38 – 123.1 mA/cm2) on the
efficiency of phenol removal in varying
cocentrations (1-10 mM). Findings revealed that
complete removal of phenol was achieved at current
densities of 61.5, 76.9, 92.3 and 123.1 mA/cm2 for
cocentrations of 1, 3, 6 and 10 mM respectively, in
the presence of 1M HClO4 at contact times of 150,
diffraction peak belonged Sb and SnO2 211, being
21,22
reported in previous study as well
.

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AZARIAN et al., Orient. J. Chem., Vol. 34(2), 757-763 (2018)
300, 350 and 400 minutes. As can be observed,
there is a reverse relationship between phenol
removal and pollutant content. At high current
densities, ohmic loses increase on the surface of
electrode because of the formation of gases
microbubbles. Thus, it is expected to see a decrease in
the removal efficiency at lower electro-conductivity.
and 1 mM of initial concenteration, respectively
(Table 1). Because an increase in contact time is
accompanied with more ozone generation and
consequently more phenol is removed, as there was
a high content of the phenol on the surface of the
electrode in the beginning of the reaction, so, the
rate of decomposition continued in the first 6.66,
5.8, 4.1 and 2.5 h min. In contrast, by proceeding
the reaction, the rate decreased because the
number of the phenol molecules reduced. The other
very important point to note here is that using high
current densities resulted in the destruction of the
Ni-Sb-SnO2 layer, but low current densities in longer
detention times led to higher durability of the layer14.
Moreover, the use of high current densities not only
destructs the anode on the account of adverse
reactions like oxygen production (reaction 4) but
also decreases the efficiency of ozone generation.
Fig. 6. Effect of CD on phenol removal by the
Ti/Ni-Sb-SnO2 anode: at retention times of 150, 300,
350 and 400 min for cocentrations of 1, 3, 6 and 10
mM of phenol respectively, in the presence of
1M HClO4
Effect of contact time
The optimal amounts of CD were applied
to attain the best contact time. Thus, for
concentreations of 1, 3, 6 and 10 mM of phenol,
respectively, the optimized values of CD achieved
from the last stage were used. Findings
demonstrated that the grow in contact time led to
raising removal efficiency (Fig. 7). In general, the
highest degradation performances were obtained
at contact time of 6.66, 5.8, 4.1 and 2.5 h at 10, 6, 3
Fig. 7. Effect of retention time on phenol removal
by the Ti/Ni-Sb-SnO2 anode: at CD of 61.5, 76.9,
92.3 and 123.1 mA/cm2 for cocentrations of 1, 3, 6
and 10 mM of phenol respectively, in the presence
of 1M HClO4
Table 1:The values of the optimum CD and the retention time for
complete removal of phenol with different concentrations using
Ti/Ni-Sb-SnO2 anode
Phenol concentration
(mM)
Optimum CD
(mA/cm2)
Optimum retention
time (min)
Removal
efficiency (%)
10
60
3
123.1
92.3
76.9
61.5
400
350
300
150
99.9
99.9
99.9
99.9
1

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AZARIAN et al., Orient. J. Chem., Vol. 34(2), 757-763 (2018)
CONCLUSION
a
suitable measure to be considered as an effective
process for phenol containing wastewaters.
In this research, the electrode ofTi/Ni-Sb-SnO2
was built electrochemically and the key parameters
affective in construction of this electrode for better
production of ozone were investigated. The built
electrode was applied for phenol removal at
different contents, current densities and contact
times. The findings showed that the electrode could
degrade the contaminant effectively, but, for the
stability of the deposited layer on the electrode’s
surface, low current densities and longer contact
times are suggested to be applied. All this makes
ACKNOWLEDGEMENT
This work was supported by the Vice
Chancellorship for Research Affairs of UMSHA
(No. 9406243361). We are grateful to Hamadan
University of Medical Sciences and the Bu-Ali Sina
University for providing research materials,
equipments and fund.The authors declare that they
have no conflicts of interest.
REFERENCES
1.
Samadi, M. T.; Shokoohi, R.; Poormohammadi,
A.; Azarian, G.; Harati, M.; Shanesaz, S.
Orient. J. Chem., 2016, 32, 1015-1024.
Prakash, D.; Singh, S.; Kumar, S. Orient. J.
Chem., 2017, 33, 462-469.
Frascari, D.; Bacca, A. E. M.; Zama, F.; Bertin,
L.; Fava, F.; Pinelli, D. Chem. Eng. J., 2016,
283, 293-303.
Xu, D. Y.; Yang, Z. Chemosphere, 2013, 92,
391-398.
Olya, M. E.; Akhi, Y.; Marandi, R. Orient. J.
Chem., 2016, 32, 1295-1303.
Acta., 2014, 135, 11-18.
12.
Godini, K.; Azarian, G.; Rahmani, A. R.;
Zolghadrnasab, H. J. Res. Health Sci., 2013,
13, 188-193.
2.
3.
13.
14.
Ghasemian, S.; Asadishad, B.; Omanovic,
S.; Tufenkji, N. Water Res., 2017, 126, 299-307.
Rahmani, A. R.; Nematollahi, D.; Samarghandi,
M. R.; Samadi, M. T.; Azarian, G. J.
Electroanal. Chem., 2018, 808, 82-89.
Christensen, P.A.; Yonar, T.; Zakaria, K.
Ozone-Sci. Eng., 2013, 35, 149-167.
VijayanT.;Patil J.G.;Int.J.Sci.Technol.Educ.
Res., 2010, 1, 132-142.
4.
5.
6.
15.
16.
17.
Rahmani, H.; Gholami, M.; Mahvi, A. H.;
Alimohammadi, M.; Azarian, G.; Esrafili, A.;
Rahmani K.; Farzadkia, M. B. Environ.
Contam. Tox., 2014, 92, 341-346.
Da Silva, L.M.; Franco, D.b.V.; Sousa, L.G.;
Gonçalves, I.C. J. Appl. Electrochem., 2010,
40, 855-864.
7.
8.
Curteanu, S.; Godini, K.; Piuleac, C. G.;
Azarian, G.; Rahmani, A. R.; Butnariu, C. Ind.
Eng. Chem. Res., 2014, 53, 4902-4912.
Rahmani, A. R.; Godini, K.; Nematollahi, D.;
Azarian, G. Desalin. Water Treat., 2015, 56,
2234-2245.
Basiriparsa, J.; Abbasi, M. J. Solid. State.
Electr., 2012, 16, 1011-1018.
Rahmani, A. R.; Nematollahi, D.; Azarian,
G.; Godini, K.; Berizi, Z. Korean J. Chem.
Eng., 2015, 32, 1570-1577.
18.
19.
Yang, S. Y.; Kim D.; Park, H. Environ. Sci.
Technol., 2014, 48, 2877-2884.
Azarian, G.; Miri, M.; Nematollahi, D. Environ.
Prog. Sustain., 2017, In Press https://doi.org/
10.1002/ep.12711.
Christensen, P. A.; Lin, W. F.; Christensen,
H.; Imkum, A.; Jin, J. M.; Li, G.; Dyson, C. M.
Ozone-Sci. Eng., 2009, 31, 287-293.
Shao, D.; Li, X.; Xu H.; Yan, W. RSC Adv.,
2014, 4, 21230- 21237.
20.
9.
10.
21.
22.
Kong, J. T.; Shi, S. y.; Zhu X. P.; Ni, J. R.
J. Environ. Sci., 2007, 19, 1380-1386.
11.
Zakaria, K.; Christensen, P. A. Electrochim.