An Energy Efficient Crypto Suit for Secure Underwater Sensor Communication using Genetic Algorithm

Vol. 5, No. 1 | January – June 2022

SJET | P-ISSN: 2616-7069 |E-ISSN: 2617-3115 | Vol. 5 No. 1 January – June 2022
32

MnO2@Co3O4 nanocomposite based electrocatalyst

for effective oxygen evolution reaction

Muhammad Yameen Solangi1, Abdul Hanan Samo2, Abdul Jaleel Laghari1, Umair

Aftab1, Rehan Ali Qureshi1, Muhammad Ishaque Abro1 Muhammad Imran Irfan3

Abstract:

For large-scale energy applications, conceiving low-cost and simple earth-abundant

electrocatalysts are more difficult to develop. By using an aqueous chemical technique, MnO2

was added into Co3O4 with varying concentrations to prepare MnO2@Co3O4 nanocomposite

(CM). In an aqueous solution of 1 M KOH, the electrocatalyst with a greater concentration of

MnO2 outperforms in terms of OER. To confirm the composition, crystalline structure, and

morphology of the electrocatalyst, analytical methods such as X-ray diffraction (XRD)

techniques, Fourier transformed infrared spectroscopy (FTIR) and scanning electron

microscopy (SEM) were used. At 20 mA/cm2 current density, the electrocatalyst had a lowest

overpotential of 310 mV verses Reversible hydrogen electrode (RHE). The CM-0.4

electrocatalyst has a small Tafel slope value and charge transfer resistance of approximately 72

mV/dec and 74 Ω which confirm its high catalytic activity. The electrocatalyst reveals a double

layer capacitance (Rct) of 18 µF/cm2 and an electrochemical active surface area (ECSA) of 450

cm2, demonstrating that addition of MnO2 impurities into Co3O4 enhances the active catalyst

sites. These findings contribute to the knowledge of these kind of catalysts, that will assist in the

development of novel electrocatalysts which are feasible for prospective energy generation

technologies.

Keywords: Electrocatalyst; oxygen evolution reaction; cobalt oxide; manganese oxide;

alkaline media.

1. Introduction

Growing energy consumption and the
depletion of fossil fuels are two major
challenges which have led to the discovery of
earth abundant alternative sources and the
development of effective energy storage
systems [1-3]. For this fact, electrochemical
water electrolysis is one of the most efficient
methods to obtain hydrogen [4,5].

Herein, hydrogen evolution reaction
(HER) takes place at the cathode while oxygen
evolution reaction (OER) happens at the anode

1Dept. of Metallurgy & Materials Engineering, MUET, Jamshoro, Pakistan.
2College of Materials & Chemical Engineering, Harbin Engineering University, Harbin, China.
3Institute of Chemistry, University of Sargodha, Sargodha- 40100 Pakistan

Corresponding Author: yameen.engineer14@gmail.com

in an electrochemical water splitting
mechanism. Nevertheless, the efficient
electrocatalysts were utilized for effective
water splitting [6-8]. Currently, the
RuO2/IrO2 based noble electrocatalysts have
superiority for OER with lower low
overpotential value for higher electro-
catalytical activity [9,10].

However, they are rare in nature and
massive cost electrocatalyst that restrict the
usage in industrial applications. To achieve
cost-effective hydrogen generation, creating
an electro-catalyst for water splitting that are

mailto:yameen.engineer14@gmail.com

MnO2@Co3O4 nanocomposite based electrocatalyst for effective oxygen evolution reaction (pp. 32 - 40)

Sukkur IBA Journal of Emerging Technologies - SJET | Vol. 5 No. 1 January – June 2022

efficient, inexpensive, earth-abundant, stable,
and operate at low overpotential is critical [11-
13].

The OER mechanism contains 4 electron
charge transfer kinetics [14]. Therefore, OER
mechanism is slow process as compared to
HER and responsible for overall performance
of water splitting. In this regard, OER requires
more overpotential for water oxidation which
provide the major hindrance in water splitting
technology [15-17]. So that, researchers are
developing electrocatalysts for OER with low
overpotential, ease of synthesis and low-cost.
In this fact, various transition metal oxides,
sulfides, selenides, and phosphide based
electrocatalysts were developed to overcome
such problems [18-20].

In this work, the impurity addition strategy
was applied to create nanocomposite for
essential OER performance. Wherein, MnO2
as an impurity was added in Co3O4 to create
oxygen vacancies in the Co3O4
nanostructures which may be responsible for
increase in active sites and decrease the
overpotential of catalyst that leads to superior
OER performance. The synthesized
nanocomposite was characterized by XRD,
FTIR, SEM and Electrochemical Analysis for
the determination of crystallinity, phase purity,
morphology, and electrochemical
investigation respectively.

2. Experimental Work

2.1 Materials and Methods

Cobalt chloride hexahydrate
(CoCl2.6.H2O), urea (CH₄N₂O) and
potassium permanganate (KMnO4) were
brought from Sigma Aldrich, Karachi,
Pakistan. The synthesis of MnO2@Co3O4
nanocomposite was developed by aqueous
chemical method [21]. Herein, 0.1M solution
of CoCl2.6.H2O and CH₄N₂O was added into
100 ml deionized water. After that, KMnO4
with two different concentrations i.e., 0.2 g
and 0.4 g were added separately in different
breakers containing cobalt oxide precursor.
These samples were labeled as Co3O4
pristine, CM-0.2 and CM-0.4. The label CM
denotes the composite of MnO2@Co3O4.

These samples were mixed properly and
placed into an electric oven at 95OC for 5 h.
Once the reaction time was completed then
samples were taken out from oven and washed
multiple times with deionized (DI) water to
remove the extra impurities. After that,
nanocomposite material was collected through
sedimentation method in china dish and dried
in oven at 100OC for moisture content
removal. The dried samples were placed into
furnace for calcination to convert hydroxide
phase into oxide phase at 500OC for 5 h. When
the calcination time finished then sample were
taken from furnace and nanocomposite was
achieved for further characterization.

2.2 Physical Characterization

Powder X-ray diffraction (XRD) was
performed on a Philips PAN analytical powder
x-ray diffractometer at 45 kV and 45 mA using
Cu Kα radiation (λ = 0.15406 nm). The lattice
parameters were calculated by Bragg’s law in
cubic formula.

𝑑(ℎ𝑘𝑙) =
𝑎

√ℎ2 + 𝑘2 + 𝑙2

Whereas, “d(hkl)” is the atomic planer
spacing, “a” is lattice constant and “(h,k,l)” is
the diffracted plane.

The Crystallite size of sample was computed
by Debye’s Scherrer equation at (311) plane.

𝐷 =
𝑘𝜆

𝛽𝐶𝑜𝑠𝜃

where “D” is the crystallite size (Å), “k” is
Scherrer constant that is equal to 0.9, “λ” is the
wavelength of source CuKα, “β” is the full
width at half maximum (Radians) and “θ” is
the peak position (Radians).

Fourier transform infrared spectroscopy
(FTIR) was obtained on a Perkin Elmer FTIR
Spectrometer spectrum two. Scanning electron
microscopy (SEM) images were achieved on
JSM-6380L JEOL scanning electron
microscope.

2.3 Electrochemical Analysis

Electrochemical measurements were
carried out on a VERSASTAT 4-500
Potentiostat consisting of a three-electrode
assembly i.e., working electrode, reference

MnO2@Co3O4 nanocomposite based electrocatalyst for effective oxygen evolution reaction (pp. 32 - 40)

Sukkur IBA Journal of Emerging Technologies - SJET | Vol. 5 No. 1 January – June 2022

electrode and counter electrode made up of
glassy carbon electrode, silver-silver chloride
electrode and Pt wire respectively. Glassy
carbon electrodes were modified with the
electrocatalyst, and various experiments were
performed in 1M KOH solution. The linear
sweep voltammetry (LSV) was done to
determine the polarization curves at a scan rate
of 5 mV/s and cyclic voltammetry (CV) was
used to investigate the effective active surface
area at 10, 20 and 30 mV/s scan rates. The
chrono-potentiometric analysis was
accomplished for durability as synthesized
electrocatalyst at 20 mA/cm2 for 40 h.

3. Results and Discussion

3.1 Physical Characterization

The XRD spectrum of pristine Co3O4,
CM-0.2 and CM-0.4 can be seen in Fig.1. The
XRD spectra of pristine Co3O4 resembled
with JCPDS card no. 01-080-1536. The
diffraction pattern revealed at the planes of
(111), (220), (311), (222), (400), (331), (422),
(511), (440), (531), (442), (620), (533) and
(622) at the 2 theta angles of 18.848o, 31.017o,
36.461o, 38.231o, 44.436o, 48.669o, 55.177o,
58.842o, 64.656o, 68.011o, 69.111o, 73.437o,
76.618o and 77.668o respectively. This
JCPDS card validates that the Co3O4 has
cubic crystalline structure [22,23]. Whereas
XRD spectrum of MnO2 are matched with
JCPDS card no. 00-044-0992 that diffracted at
2θ values of 19.112o, 37.121o, 38.958o,
45.068o, 49.498o, 59.599o, 65.703o and
69.583o corresponded at the planes (111),
(311), (222), (400), (331), (511), (531) and
(440). which revealed that MnO2 is also in
cubic crystalline phase.

In addition, other structural features such
atomic planer spacing, lattice constant and
crystallite size of samples are given in the
Table 1. The lattice constant of pristine Co3O4
is higher but the addition of MnO2 reduces its
lattice constant that leads to reduction in
crystallite size. Here, the substitution of large
Co2+ atom (0.72 Å) with small Mn4+ atom
(0.67 Å) carried out that may be responsible
for shrinkage of unit cell and achieved
reduction in the lattice constant. However, the
major peak of Co3O4 at (311) diffracted plane

shifted toward right side as the concentration
of MnO2 increases as shown in Fig 1(b) which
also suggested the substitution of Co atom by
Mn atom. Therefore, crystallite size of
composite decreases as the concentration of
MnO2 increases [24,25].

Fig. 1. (a) XRD pattern of various samples (b)
Zoom in view of XRD peak shift

The FTIR spectra of various samples are
shown in Fig. 2. It represented that pristine
Co3O4, CM-0.2 and CM-0.4 involved same
peak of O-H, C-H, C=O, O-H, C-O and C=C
corresponding to 3438 cm-1, 2927cm-1,
1797cm-1, 1035 cm-1 and 878 cm-1. These
organic bonds achieved from the Potassium
bromide (KBr) that were used for the making
the pallet of KBr and sample for FTIR
measurement. Despite this, the main
difference was observed in pristine Co3O4 and
nanocomposite (CM-0.4) of metal oxide M-O
peaks which represent O-Co-O at 570 cm-1
and Co-O at 663 cm-1. However, the presence

MnO2@Co3O4 nanocomposite based electrocatalyst for effective oxygen evolution reaction (pp. 32 - 40)

Sukkur IBA Journal of Emerging Technologies - SJET | Vol. 5 No. 1 January – June 2022

of MnO2 in Co3O4 nanostructures sharpen the
metal oxide peaks due to the addition of MnO2
impurities [22,26,27].

Fig. 2. FTIR spectra of different samples

Fig. 3. SEM images of (a) Pristine Co3O4 (b)
CM-0.2 (c) CM-0.4

The morphology of prepared Co3O4
pristine and nanocomposites was examined by
scanning electron microscopy (SEM). The

SEM images of samples are shown in Fig. 3.
The morphology of pristine Co3O4 showed
nano needles like structure as shown in Fig.
3(a) while the morphology of CM-0.2 and
CM-0.4 contained nano flakes in the matrix of
nano needles like structure as shown in Fig.
3(b, c). It can be seen that CM-0.2
nanocomposite contained fewer nano flakes
than CM-0.4. which stated that as the amount
of MnO2 increase then nano flakes
concentration increases in nano needle matrix.

3.2 Electrochemical Analysis

The electrochemical analysis of various
samples was investigated in 1M KOH
environment. The LSV polarization curves can
be seen in Fig. 4(a) that shows CM-0.4 has
lowest overpotential of 310 mV as compare to
the overpotential of pristine Co3O4 and CM-
0.2 as 430 mV and 350 mV vs RHE at the
current density of 20 mA/cm2. The CM-0.4
electrocatalyst exhibits high OER
performance due to lowest overpotential as
compare to updated electrocatalyst that can be
seen in Table 3. The Tafel values were
obtained by linear fit region of polarization
curves as shown in Fig. 4(b). The Tafel values
of pristine Co3O4, CM-0.2 and CM-0.4 are
calculated as 102 mV/dec, 86 mV/dec and 72
mV/dec respectively.

The oxygen evolution reaction (OER)
takes place through four electron transfer
mechanism which is given as under.

1. M + OH− → MOH + e−

2. MOH + OH− → MO− + H2O

3. MO− → MO + e−

4. 2𝑀𝑂 → 2M + O2 +2𝑒 −

The OER kinetic and theoretical Tafel
values in alkaline media of 1, 2, 3 and 4 sub
reactions are 120 mV/dec, 60 mV/dec, 40
mV/dec and 15 mV/dec respectively [28, 29].
Therefore, the current study contains 72
mV/dec Tafel value of best composite which
suggest that step-1 is rate determining step for
effective OER performance.

MnO2@Co3O4 nanocomposite based electrocatalyst for effective oxygen evolution reaction (pp. 32 - 40)

Sukkur IBA Journal of Emerging Technologies - SJET | Vol. 5 No. 1 January – June 2022

Fig. 4. Electrochemical Analysis of various
electrocatalysts (a) Polarization curve (b)

Tafel plot (c) Stability & Durability of best

sample (d) Durability of best electrocatalyst at

different current densities.

The stability test was performed by
measuring LSV before and after
chronopotentiometry at 20 mA/cm2. The
stability of CM-0.4 illustrated in Fig. 4(c)
which represented its overpotential did not
drop after long operation. Furthermore, the
durability of CM-0.4 can be seen inside Fig.
4(c) which showed that CM-0.4 electrocatalyst
is long term durable for 40 h. In addition,
durability test was also performed at different
current densities i.e., 25 mA/cm2 and 50
mA/cm2 as shown in Fig. 4(d). It revealed that
the potential does not drop at various current
densities which give significant proof of
electrocatalyst’s stability.

The cyclic voltammetric (CV) experiment
was performed at different scan rates on
various electrocatalysts as shown in Fig. 5.
The cyclic voltammetry of CM-0.4 has highest
current density that represent its highest
catalytical active sites as seen in Fig. 5(c). In
addition, the double layer capacitance Cdl
value plots were extracted from CV curves as
illustrated in Fig. 5(d). The Cdl values of
pristine Co3O4, CM-0.2 and CM-0.2 have
been calculated as 3.6 µF/cm2, 7.8 µF/cm2
and 18 µF/cm2. The CM-0.4 electrocatalyst
has high double layer capacitance than other as
prepared electrocatalysts.

The electrochemical active surface area
ESCA was calculated by Cdl/Cs expression,
whereas specific capacitance of the electrolyte
(Cs) in 1M KOH is about 0.04 [30]. The
electrochemical active surface area (ECSA)
was calculated as 450 cm2, 195 cm2, and 90
cm2 for CM-0.4, CM-0.2 and Pristine Co3O4
respectively which are mentioned in Table 2.
This data also authenticates the catalytical
performance of CM-0.4.

The electrochemical impedance
spectroscopy data represented by Nyquist plot
and Bode (1, 2) of various samples are shown
in Fig. 6. The EIS data was fitted via Z view
software and fitted equivalent circuit is
enclosed in Fig. 6(a). The solution resistance
Rs is almost similar to all samples due to
similar electrolyte conditions. The charge
transfer resistance Rct was obtained as 74 Ω,
240 Ω and 460 Ω of CM-0.4, CM-0.2 and
pristine Co3O4 respectively. The results also

MnO2@Co3O4 nanocomposite based electrocatalyst for effective oxygen evolution reaction (pp. 32 - 40)

Sukkur IBA Journal of Emerging Technologies - SJET | Vol. 5 No. 1 January – June 2022

validate that the Rct of nanocomposite based
electrocatalyst is lower than pristine
electrocatalyst which facilitates the movement
of charge in between anode and cathode via
electrolyte.

Fig. 5. Cyclic voltammetry of various
electrocatalysts (a) Pristine Co3O4 (b) CM-0.2

plot.

The bode-1 plot gives the information about
gain parameter and phase angle in the range of
0.1Hz to 100kHz frequency at 1.45V applied
potential. The phase angles obtained as
pristine Co3O4 (50.123o), CM-0.2 (45.537o)
and CM-0.4 (31.289o) that confirm the
superior activity of CM-0.4 electrocatalyst.
Furthermore, the bode-2 plot provides the
knowledge about maximum oscillation
frequency of catalyst. It was noticed that CM-
0.4 contained least oscillation frequency as
compared to other two catalyst. Therefore,
better adsorption of reactive species on the
surface of electrocatalysts is attributed due to
greater electron recombination lifetime. From
these outcomes, it is suggested that CM-0.4
electrocatalyst can be potential candidate for
superior water oxidation reaction.

Fig. 6. Electrochemical impedance
spectroscopy data of pristine Co3O4, CM-0.2

and CM-0.4 (a) Nyquist plot (b) Bode plot-1

and (c) Bode plot-2

MnO2@Co3O4 nanocomposite based electrocatalyst for effective oxygen evolution reaction (pp. 32 - 40)

Sukkur IBA Journal of Emerging Technologies - SJET | Vol. 5 No. 1 January – June 2022

TABLE I. XRD STRUCTURAL FEATURES OF PRISTINE AND COMPOSITE SAMPLES.

Sample IDs (hkl) 2 Theta d spacing Lattice
Constant

FWHM Crystallite
Size (D)

Degree Å Å Degree Å

Co3O4 Pristine (311) 36.4617 2.4622 8.4118 0.28356 294.96

CM-0.2 (311) 36.470 2.4617 8.4051 0.30115 277.74

CM-0.4 (311) 36.658 2.4495 8.3821 0.60382 138.59

TABLE II. SUMMARY OF UNIQUE FEATURES OF PRESENTED OER CATALYSTS

Catalyst

Calculated

from LSV
Calculated from EIS Calculated from CV

Tafel Slope

Charge

Transfer

Resistance

Double Layer

Capacitance

Double

Layer

Capacitance

Electrochemically

active surface area

B Rct CPEdl Cdl ECSA

mV/dec Ω Mf (µF/cm2) cm2

Co3O4
Pristine

102 460 0.04 3.6 90

CM-0.2 86 240 0.31 7.8 195

CM-0.4 72 74 0.37 18 450

TABLE III. COMPARISON OF CM-0.4 COMPOSITE AS OER CATALYST WITH RECENTLY REPORTED
ELECTROCATALYSTS.

Electrocatalyst Electrolyte Current Density Overpotential References

MnO2@Co3O4 (CM-0.4) 1 M KOH 20 mA/cm
2 310 mV This work

Mg/Co3O4 1 M KOH 20 mA/cm
2 320 mV [31]

Fe3O4/Co3O4 1 M KOH 10 mA/cm
2 370 mV [13]

CoSe4 1 M KOH 10 mA/cm
2 320 mV [32]

Mn-Co Phosphide 1 M KOH 10 mA/cm2 330 mV [33]

NiCo2S4/RGO 1 M KOH 10 mA/cm
2 366 mV [34]

CoOx-N-C/TiO2C 1 M KOH 10 mA/cm
2 350 mV [35]

MnO2@Co3O4 nanocomposite based electrocatalyst for effective oxygen evolution reaction (pp. 32 - 40)

Sukkur IBA Journal of Emerging Technologies - SJET | Vol. 5 No. 1 January – June 2022

4. Conclusion

The summery of present work involves the
MnO2@Co3O4 nanocomposite based
electrocatalysts which have been synthesized
by aqueous chemical method. The XRD
pattern and FTIR spectrum validate the
synthesis of pristine Co3O4 and CM-
nanocomposite. The CM-0.4 catalyst having
morphology of nano flakes in the matrix of
nano needles exhibits lowest overpotential of
310 mV at current density of 20 mA/cm2. It
also contains low Tafel slope value and Rct
value as 72 mv/dec and 74 Ω respectively.
This electrocatalyst has expressed higher
ECSA of 450 cm2. In addition, it is stable and
long-term durable for 40 h that makes it
superior for OER activity.

DATA AVAILABILITY STATEMENT

It is stated that this data is soul property of
authors and not taken from any data base. The
authors also declare that this data is not
published in any other journal.

AUTHOR CONTRIBUTION

All authors equally contribute for this work

CONFLICT OF INTEREST

The authors declare no conflict of interest.

ACKNOWLEDGMENT

This research work was accomplished in
Department of Metallurgy and Materials
Engineering and Advanced Research
Laboratory, MUET, Jamshoro, Sindh,
Pakistan.

REFERENCES

[1] U. Aftab, A. Tahira, R. Mazzaro, M. I. Abro, M. M.
Baloch, M. Willander, et al., "The chemically
reduced CuO–Co3O4 composite as a highly
efficient electrocatalyst for oxygen evolution
reaction in alkaline media," Catalysis Science &
Technology, vol. 9, pp. 6274-6284, 2019.

[2] A. Mehboob, S. R. Gilani, A. Anwar, A. Sadiqa, S.
Akbar, and J. Patujo, "Nanoscale cobalt-oxide
electrocatalyst for efficient oxygen evolution
reactions in alkaline electrolyte," Journal of Applied
Electrochemistry, vol. 51, pp. 691-702, 2021.

[3] P. F. Liu, H. Yin, H. Q. Fu, M. Y. Zu, H. G. Yang,
and H. Zhao, "Activation strategies of water-
splitting electrocatalysts," Journal of Materials
Chemistry A, vol. 8, pp. 10096-10129, 2020.

[4] A. Tahira, U. Aftab, M. Y. Solangi, A. Gradone, V.
Morandi, S. S. Medany, et al., "Facile deposition of
palladium oxide (PdO) nanoparticles on CoNi2S4
microstructures towards enhanced oxygen
evolution reaction," Nanotechnology, 2022.

[5] Z. H. Ibupoto, A. Tahira, A. A. Shah, U. Aftab, M.
Y. Solangi, J. A. Leghari, et al., "NiCo2O4
nanostructures loaded onto pencil graphite rod: An
advanced composite material for oxygen evolution
reaction," International Journal of Hydrogen
Energy, vol. 47, pp. 6650-6665, 2022.

[6] A. Q. Mugheri, A. Tahira, U. Aftab, A. L. Bhatti, R.
Lal, M. A. Bhatti, et al., "Chemically Coupled
Cobalt Oxide Nanosheets Decorated onto the
Surface of Multiwall Carbon Nanotubes for
Favorable Oxygen Evolution Reaction," Journal of
Nanoscience and Nanotechnology, vol. 21, pp.
2660-2667, 2021.

[7] B. Paul, P. Bhanja, S. Sharma, Y. Yamauchi, Z. A.
Alothman, Z.-L. Wang, et al., "Morphologically
controlled cobalt oxide nanoparticles for efficient
oxygen evolution reaction," Journal of Colloid and
Interface Science, vol. 582, pp. 322-332, 2021.

[8] C. L. I. Flores and M. D. L. Balela, "Electrocatalytic
oxygen evolution reaction of hierarchical
micro/nanostructured mixed transition cobalt oxide
in alkaline medium," Journal of Solid State
Electrochemistry, vol. 24, pp. 891-904, 2020.

[9] W. H. L. P. D. Jaekyung Yia, Chang Hyuck Choi
(Ph.D.), Yuri Lee (Ph.D.), Kyung Su Park (Ph.D.),
Byoung Koun Min (Ph.D.), Yun Jeong Hwang
(Ph.D.), Hyung-Suk Oh (Ph.D., "Effect of Pt
introduced on Ru-based electrocatalyst for oxygen
evolution activity and stability," Electrochemistry
Communications, vol. 104, p. 106469, 2019.

[10] Q. Shi, C. Zhu, D. Du, and Y. Lin, "Robust noble
metal-based electrocatalysts for oxygen evolution
reaction," Chem Soc Rev, vol. 48, pp. 3181-3192,
2019.

[11] D. Zhao, Z. Zhuang, X. Cao, C. Zhang, Q. Peng, C.
Chen, et al., "Atomic site electrocatalysts for water
splitting, oxygen reduction and selective oxidation,"
Chemical Society Reviews, vol. 49, pp. 2215-2264,
2020.

[12] A. Tahira, Electrochemical water splitting based on
metal oxide composite nanostructures vol. 2066.
Linköping: Linköping University Electronic Press,
2020.

[13] A. L. Bhatti, U. Aftab, A. Tahira, M. I. Abro, R. H.
Mari, M. K. Samoon, et al., "An Efficient and
Functional Fe3O4/Co3O4 Composite for Oxygen
Evolution Reaction," Journal of Nanoscience and
Nanotechnology, vol. 21, pp. 2675-2680, 2021.

[14] A. Hanan, A. J. Laghari, M. Y. Solangi, U. Aftab,
M. I. Abro, D. Cao, et al., "CdO/Co3O4

MnO2@Co3O4 nanocomposite based electrocatalyst for effective oxygen evolution reaction (pp. 32 - 40)

Sukkur IBA Journal of Emerging Technologies - SJET | Vol. 5 No. 1 January – June 2022

Nanocomposite as an Efficient Electrocatalyst for
Oxygen Evolution Reaction in Alkaline Media,"
International Journal of Engineering Science
Technologies, vol. 6, pp. 1-10, 2022.

[15] Y. V. Kaneti, Y. Guo, N. L. W. Septiani, M. Iqbal,
X. Jiang, T. Takei, et al., "Self-templated
fabrication of hierarchical hollow manganese-
cobalt phosphide yolk-shell spheres for enhanced
oxygen evolution reaction," Chemical Engineering
Journal, vol. 405, p. 126580, 2021.

[16] I. M. Abdullahi, J. Masud, P.-C. Ioannou, E.
Ferentinos, P. Kyritsis, and M. Nath, "A Molecular
Tetrahedral Cobalt–Seleno-Based Complex as an
Efficient Electrocatalyst for Water Splitting,"
Molecules, vol. 26, p. 945, 2021.

[17] A. L. Bhatti, U. Aftab, A. Tahira, M. I. Abro, M.
Kashif samoon, M. H. Aghem, et al., "Facile doping
of nickel into Co3O4 nanostructures to make them
efficient for catalyzing the oxygen evolution
reaction," RSC Advances, vol. 10, pp. 12962-
12969, 2020.

[18] C. Linder, S. G. Rao, A. le Febvrier, G. Greczynski,
R. Sjövall, S. Munktell, et al., "Cobalt thin films as
water-recombination electrocatalysts," Surface and
Coatings Technology, vol. 404, p. 126643, 2020.

[19] A. Badreldin, A. E. Abusrafa, Abdel, and A.
Wahab, "Oxygen-Deficient Cobalt-Based Oxides
for Electrocatalytic Water Splitting,"
ChemSusChem, vol. 14, pp. 10-32, 2021.

[20] A. Badruzzaman, A. Yuda, A. Ashok, and A.
Kumar, "Recent advances in cobalt based
heterogeneous catalysts for oxygen evolution
reaction," Inorganica Chimica Acta, vol. 511, p.
119854, 2020.

[21] M. R. S. A. Janjua, "Synthesis of Co3O4 Nano
Aggregates by Co-precipitation Method and its
Catalytic and Fuel Additive Applications," Open
Chemistry, vol. 17, pp. 865-873, 2019.

[22] D. D. M. Prabaharan, K. Sadaiyandi, M.
Mahendran, and S. Sagadevan, "Precipitation
method and characterization of cobalt oxide
nanoparticles," Applied Physics A, vol. 123, 2017.

[23] M. Y. Solangi, U. Aftab, A. Tahira, M. I. Abro, R.
Mazarro, V. Morandi, et al., "An efficient palladium
oxide nanoparticles@Co3O4 nanocomposite with
low chemisorbed species for enhanced oxygen
evolution reaction," International Journal of
Hydrogen Energy, vol. 47, pp. 3834-3845, 2022.

[24] L. Abdelhak, B. Amar, B. Bedhiaf, D. Cherifa, and
B. Hadj, "Characterization of Mn-Doped Co3O4
Thin Films Prepared by Sol Gel-Based Dip-Coating
Process," High Temperature Materials and
Processes, vol. 38, pp. 237-247, 2019.

[25] N. Manjula, M. Pugalenthi, V. S. Nagarethinam, K.
Usharani, and A. R. Balu, "Effect of doping
concentration on the structural, morphological,
optical and electrical properties of Mn-doped CdO
thin films," Materials Science-Poland, vol. 33, pp.
774-781, 2015.

[26] T. Athar, A. Hakeem, N. Topnani, and A. Hashmi,
"Wet Synthesis of Monodisperse Cobalt Oxide
Nanoparticles," ISRN Materials Science, vol. 2012,
pp. 1-5, 2012.

[27] A. N. Naveen and S. Selladurai, "Investigation on
physiochemical properties of Mn substituted spinel
cobalt oxide for supercapacitor applications,"
Electrochimica Acta, vol. 125, pp. 404-414, 2014.

[28] U. Aftab, A. Tahira, R. Mazzaro, V. Morandi, M. I.
Abro, M. M. Baloch, et al., "Facile NiCo2S4/C
nanocomposite: an efficient material for water
oxidation," Tungsten, vol. 2, pp. 403-410, 2020.

[29] A. Q. Mugheri, A. Tahira, U. Aftab, M. I. Abro, A.
B. Mallah, G. Z. Memon, et al., "An advanced and
efficient Co3O4/C nanocomposite for the oxygen
evolution reaction in alkaline media," RSC
Advances, vol. 9, pp. 34136-34143, 2019.

[30] A. Tahira, Z. H. Ibupoto, M. Vagin, U. Aftab, M. I.
Abro, M. Willander, et al., "An efficient
bifunctional electrocatalyst based on a nickel iron
layered double hydroxide functionalized Co3O4
core shell structure in alkaline media," Catalysis
Science & Technology, vol. 9, pp. 2879-2887, 2019.

[31] A. H. Samo, U. Aftab, M. Yameen, A. J. Laghari,
M. Ahmed, M. N. Lakhan, et al., "MAGNESIUM
DOPED COBALT-OXIDE COMPOSITE FOR
ACTIVE OXYGEN EVOLUTION REACTION,"
Journal of Applied and Emerging Sciences, vol. 02,
pp. 210-216, 2021

[32] I. M. Abdullahi, J. Masud, P.-C. Ioannou, E.
Ferentinos, P. Kyritsis, and M. Nath, "A Molecular
Tetrahedral Cobalt–Seleno-Based Complex as an
Efficient Electrocatalyst for Water Splitting,"
Molecules, vol. 26, p. 945, 2021.

[33] Y. V. Kaneti, Y. Guo, N. L. W. Septiani, M. Iqbal,
X. Jiang, T. Takei, et al., "Self-templated
fabrication of hierarchical hollow manganese-
cobalt phosphide yolk-shell spheres for enhanced
oxygen evolution reaction," Chemical Engineering
Journal, vol. 405, p. 126580, 2021.

[34] C. Shuai, Z. Mo, X. Niu, X. Yang, G. Liu, J. Wang,
et al., "Hierarchical NiCo2S4 nanosheets grown on
graphene to catalyze the oxygen evolution
reaction," Journal of Materials Science, vol. 55, pp.
1627-1636, 2020.

[35] L. He, J. Liu, B. Hu, Y. Liu, B. Cui, D. Peng, et al.,
"Cobalt oxide doped with titanium dioxide and
embedded with carbon nanotubes and graphene-like
nanosheets for efficient trifunctional electrocatalyst
of hydrogen evolution, oxygen reduction, and
oxygen evolution reaction," Journal of Power
Sources, vol. 414, pp. 333-344, 2019.