Synthesis and characterization of polyaniline/nickel oxide composites for fuel additive and dyes reduction

Article abstract of DOI:10.1016/j.cplett.2021.138713

Polyaniline (PANI) and Polyaniline/Nickel oxide (PANI/NiO) composites are prepared to use as a potential catalyst, by Chemical oxidation method using ammonium persulfate (NH₄)₂S₂O₈)) as an oxidant. Nickel oxide (NiO) nanopartiles are prepared by Sol-gel method. The synthesized products were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction technique (XRD). The prepared PANI/NiO composites are used as additive with different concentrations in diesel to investigate their efficiency as fuel additive. The catalytic properties are studied by using the synthesized products as catalyst for reduction of dyes in aqueous media. Sodium borohydride (NaBH₄) is used as reducing agent. Linear relationships are obtained between time and ln(A₀/A_t) for Methyl orange and Methylene blue. K_app values were obtained for three catalysts showed the increasing trend of reduction for both dyes as, PANI < NiO < PANI/NiO composites. Experimental data analysis proved PANI/NiO composites to be efficient catalysts and fuel additive as compared to PANI and NiO.

Full text of DOI:10.1016/j.cplett.2021.138713

Chemical Physics Letters 776 (2021) 138713
Contents lists available at ScienceDirect
Chemical Physics Letters
journal homepage: www.elsevier.com/locate/cplett
Research paper
Synthesis and characterization of polyaniline/nickel oxide composites for
fuel additive and dyes reduction
a
,
b
b
c
b
d
Saba Jamil , Zunaira Ahmad , Muhammad Ali , Shanza Rauf Khan , Sarmed Ali ,
a
e
e
Mohamed Amen Hammami , Muhammad Haroon , Tawfik A. Saleh ,
Muhammad Ramzan Saeed Ashraf Janjua Associate Professor, PhD
e,*
a
Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853, USA
b
Super Light Materials and Nanotechnology Laboratory, Department of Chemistry, University of Agriculture, Faisalabad 38000, Pakistan
Department of Chemistry, University of Sargodha, Sargodha 40100, Pakistan
c
d
e
Department of Engineering, Ostfold University College, Fredrikstad, Norway
Department of Chemistry, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia
A R T I C L E I N F O
A B S T R A C T
Keywords:
Polyaniline (PANI) and Polyaniline/Nickel oxide (PANI/NiO) composites are prepared to use as a potential
Polyaniline
Nickel oxide
Fuel additive
Dye reduction
catalyst, by Chemical oxidation method using ammonium persulfate (NH
NiO) nanopartiles are prepared by Sol-gel method. The synthesized products were characterized by Scanning
Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX), Fourier Transform Infrared Spectroscopy
FTIR) and X-ray Diffraction technique (XRD). The prepared PANI/NiO composites are used as additive with
4 2 2 8
) S O )) as an oxidant. Nickel oxide
(
(
different concentrations in diesel to investigate their efficiency as fuel additive. The catalytic properties are
studied by using the synthesized products as catalyst for reduction of dyes in aqueous media. Sodium borohy-
4 0 t
dride (NaBH ) is used as reducing agent. Linear relationships are obtained between time and ln(A /A ) for Methyl
orange and Methylene blue. Kapp values were obtained for three catalysts showed the increasing trend of
reduction for both dyes as, PANI < NiO < PANI/NiO composites. Experimental data analysis proved PANI/NiO
composites to be efficient catalysts and fuel additive as compared to PANI and NiO.
1
. Introduction
2 2 3 4 2
PANI/ZrO , PANI/TiO , PANI/Fe O and PANI/MnO , have been
extensively used for various purposes due to their high redox properties,
surface area, high conductivity and porous nature which could not be
attained by polymer alone [28]. Composites of various shapes have been
The products Polyaniline has grabbed much attention in recent years
for its potential applications in fuel cells, chemical sensors, solar cells,
diodes, electronic devices and other novel applications due to their
novel properties, such as easy processability, doping mechanism, envi-
ronmental stability and cost effectiveness [32]. Polyaniline (PANI) has
low infusibility and conductivity (in comparison with metal) which pose
a hinderance in its various applications. To overcome this difficulty,
composites of PANI with inorganic particles have been prepared
obtained such as PANI/V
method [21] while PANI/TiO
fabricated by self –assembly method [37].
2
O
5
sheets have prepared through intercalation
2
and PANI/Fe nanotubes have been
3 4
O
Metals such as iron, nickel, cobalt and many others has been used in
composition with organic matrix that has proved good catalyst [5].
Metal’s addition can generates synergistic effect, that increases catalytic
activity due to availability of more oxidation sites [26]. Nickel is being
[
22,23]. Polyaniline (PANI) has been used in composite formation with
inorganic nanoparticles that significantly enhances its functionality as a
versatile material [35]. Among various inorganic materials, metal oxide
nanoparticles has proven to be most thermally stable composites with
PANI that has enhanced its functional applications [1]. PANI-based
2 4
used with various combination e.g. with binary oxides (NiFe O ), gra-
phene oxide and polymers that produce synergistic relationship between
them and thus beneficial in electrode and supercapacitor application
[2,3]. Nickel being transition metal is widely used in chalcogenides to
enhance electrocatalytic activity [4]. Electrocatalytic activity is electro-
2 2 2
metal oxide composites such as, PANI/SnO , PANI/RuO , PANI/SiO ,
*
Corresponding author.
E-mail addresses: Janjua@kfupm.edu.sa, Dr_Janjua2010@yahoo.com (M. Ramzan Saeed Ashraf Janjua).
https://doi.org/10.1016/j.cplett.2021.138713
Received 22 February 2021; Received in revised form 13 April 2021; Accepted 30 April 2021
Available online 5 May 2021
0
009-2614/© 2021 Elsevier B.V. All rights reserved.

S. Jamil et al.
Chemical Physics Letters 776 (2021) 138713
kinetic property of catalyst that decides the performance of catalyst.
Therefore, it is necessary to improve the electron transport at surface of
catalyst to increase its catalytic activity [4]. Nickel oxide is a p-type
semiconductor with band gap 3.51 eV that is being used as a catalyst in
hydrocracking reactions, reforming of hydrocarbons and electrochromic
devices [17]. It is also utilized as an anode in fuel cells and as an ad-
hesive in paints and enamels [7]. PANI and its various composites has
been widely used as catalyst for dye degredation. Present study includes
the dye reduction of PANI/NiO composite as catalyst and fuel additive
which has not been reported. Pure PANI and Nickel oxide has also been
employed as catalyst in dyes reduction and their result are compared
with PANI/NiO composites. This shows that PANI/NiO composites re-
duces dyes faster as compared to components alone.
2.4. Catalytic application of polyaniline/nickel oxide as catalyst
The λmax of methyl orange and methylene blue were found at 464 nm
and 664 nm respectively. Dye solution of 0.0001 M was taken in a
beaker and pH was maintained at 9. Small amount of catalyst and NaBH
4
were added to dye solution taken in a cuvette. Change in absorbance of
solution was monitored by spectrophotometer. Catalytic reduction of
MO and MB were studied for three synthesized catalysts viz. Polyaniline,
Nickel oxide and Polyaniline/Nickel oxide composites.
2
.5. Catalytic application of polyaniline/nickel oxide as fuel additive
2
0, 40, 60 and 80 ppm solution of diesel were prepared by adding
The present study emphasizes on PANI/NiO composite that has been
synthesized and investigated as catalyst for dyes reduction. These
composites have also been investigated as fuel additive which has not
been used earlier. Composite has been prepared by chemical oxidation
method using ammonium persulfate as oxidant. NiO nanoparticles are
synthesized by Sol-gel method using nickel nitrate hexahydrate (Ni
0
.002, 0.004, 0.006 and 0.008 g of Polyaniline/Nickel oxide composites
in 80 ml of diesel. Various parameters of diesel were studied such as
flash point, fire point, cloud and pour point.
2.6. Characterization
(
NO
3
)
2
⋅6H
2
O) salt. Different characterization techniques such as Scan-
ning Electron Microscopy, Fourier Transfer Infrared Microscopy, Energy
Dispersive X-ray technique and X-ray Diffraction are used for charac-
terization of synthesized.
Scanning Electron Microscopy (SEM) and Energy dispersion (EDX)
with Nova NanoSEM 450 scanning electron microscope and Fourier
transform infrared spectroscopy of Polyaniline, Nickel oxide and Poly-
aniline/Nickel oxide composites were performed. X-ray diffraction
(XRD) spectrum of Polyaniline/Nickel oxide composites were obtained
2
. Experimental
(
see Fig. 1).
2
.1. Materials
3
. Results and discussion
4 2 2 8
Aniline, ammonium persulfate ((NH ) S O ) (APS), Nickel nitrate
hexahydrate (Ni(NO
3
)
2
⋅6H
2
O), sodium hydroxide (NaOH), Distilled
3.1. Scanning electron microscopy
water, Ethanol and Hydrochloric acid were used . All chemical were
used as received without any purification at Laboratory of Superlight
Materials and Nano technology, University of Agriculture, Faisalabad.
Micrographs of Polyaniline can be seen in Fig. 2. SEM images taken
at various resolutions. Fine thread like morphology is formed which
quite dense and entangled. Fibers of various lengths and diameters are
present. Diameter of threads ranges from 34 nm to 51 nm. Fig. 2 (a,b)
shows the highly dense network of polyaniline fibers at resolution
25,000X and 50,000 X (c,d) shows the long and short fibers of various
lengths intertwisted in one another.
2
.2. Synthesis of Nickel oxide
Nickel oxide nanoparticles were prepared by Sol-gel method. 0.3 M
3 2 2
of Ni(NO ) .6(H O) salt was dissolved in 100 ml of distilled water and
stirred for 30 min. 100 ml solution of 1.3 M of NaOH was added slowly
into above solution and stirred at 70℃ for 2 h. The process resulted
Greenish gel that was kept aside to attain room temperature. Gel was
washed with water and ethanol for multiple times to remove soluble
impurities. After that it was dried in oven at 80℃. Product was calci-
nated in muffle furnace at 400℃ for 2 h and black nickel oxide powder
was obtained. Measured quantity of nickel oxide was used in synthesis of
composites.
Micrographs of Nickel oxide nanoparticles are given below in Fig. 3.
Nickel oxide synthesized by Sol-gel method shows cluster of minute
nanopartcles. They are highly agglomerated and overlapped onto one
another. Nanoparticles of various sizes are present. Overall morphology
2
.3. Synthesis of polyaniline/nickel oxide composites
PANI/NiO composites were obtained by chemical oxidation poly-
merization method. 5 ml of aniline was dissolved into 100 ml of distilled
water containing 5.2 ml of HCL. Mixture was stirred for 30 min to
produce aniline hydrochloride. 1 g of Nickel oxide nanoparticles were
added to above mixture and sonicated for 30 min for homogenized
mixing. After that, mixture was kept in ice bath with stirring to attain
low temperature approximately 5℃. 0.5 M solution of APS was added
drop wise in mixture for polymerization. Colour of solution was turned
from brown to dark green at the end that was left for polymerization for
4
h under constant stirring. Mixture was kept overnight for complete
polymerization. Obtained product was washed with 0.1 M HCL, water
and ethanol to get rid of excess monomers and impurities. Product was
dried at 60-70℃. Polyaniline was also prepared through this method.
Schematic presentation of process is given as below.
Fig. 1. Schematic presentation of Polyaniline/Nickel oxide composites.
2

S. Jamil et al.
Chemical Physics Letters 776 (2021) 138713
Fig. 2. SEM micrographs of Polyaniline (a) Overall view of Polyaniline threads (b) Entangled threads of Polyaniline (c-d) magnified images of polymer threads can be
seen (d) micrograph taken at 200 nm shows clear strands.
Fig. 3. (a) Nickel oxide nanoparticles shows agglomerated morphology at 300,000 X resolution (b) Micrograph taken at 200,000 X resolution.
of nanoparticles is spherical having averge diameter of 18 nm. Size
distribution gtaph of randomly dirtributed nanoparticles is shown in
Fig. 4.
into PANI leds to increase the surface area of composites which ulti-
mately increases its adsorption and catalytic properties [30]. Expansion
in matrix also depends upon on concentration of NiO nanoparticles. Size
and morpholgy of composites changes with increase in nanopaticles
concentration [32].
Presence of Nickel oxide nanoparticles in polymer matrix dramati-
cally alter the morpholgy of PANI. The average diameter of composites
is 95 nm. This could be due to coordinating bonds present between the N
atoms of aniline and Ni of nickel oxide nanoparticles which develops
network and expands the polymer matrix [11]. NiO forms bridges be-
tween polymer chains that results in electron transport in polymer
chains and thus improves effective carrier translation length [27].
Expansion in polymer matirx creates porosity which improves its cata-
lytic properties of composites. Smaller size of NiO nanopartcles seeps
3
.2. X-ray diffraction (XRD) techique
X-ray Diffraction (XRD) shows the crystalline nature of synthesized
nanoparticles. The crystalline peaks at 2θ = 37◦ and 43 have been
identified as peaks of single phase cubic structure of NiO with diffracting
planes (111) and (200) respectively of the cubic phase of NiO [25].
◦
3

S. Jamil et al.
Chemical Physics Letters 776 (2021) 138713
Fig. 4. (a) Micrograph of PANI/NiO taen at 50,000 X magnification (b) Shows the image at 100,000 X magnification (c) shows magnified image of composites at
00,000 X (d) shows the expanded polymer matrix at 300,000 X magnification.
2
Peaks of PANI and Nickel oxide exist in composite. The small peak
◦
around 20 is for polyaniline which is due to amorphous nature of the
polymer.
3
.3. Energy dispersive X-ray analysis
EDX analysis of Polyaniline and Nickel oxide was done to determine
the elemental analysis. Composition of synthesized products can be
vitness in the form of peaks. Percentage composition is shown in Table 1.
Polyaniline EXD pattern shows eight peaks viz. 0.52, 0.42, 0.08, 0.07,
0
.04, 0.12, 0.11 and 0.07 keV. Two peaks, one at 0.52 and 0.42 keV
belongs to carbon and oxygen are property of Kβ1 trasitions. These
transitions happen to K shell from M shell i.e. from n = 3 to n = 1.
Electron jump from “p” subshell to “s” subshell. Many other peaks can
also be seen in graph which emerges bacause of adhesive or tape content
sticked to sample during analysis process. EDX pattern of Polyaniline is
shown in Fig. 5 (see Table 2).
EXD pattern of Nickel oxide is shown in Fig. 6 showing its compo-
sition. Graph shows six peaks 1.5, 0.87, 0.25, 0.19, 0.56 and 0.84 keV.
Oxygen and Nickel peak at 0.87 and 0.84 keV shows K transition from K
shell to M shell. EDX pattern is given below in Fig. 7.
Fig. 5. XRD pattern of PANI/NiO composites.
EDX pattern of PANI/NiO composites is shown in Fig. 8 including
main peaks of nickel, oxygen and carbon. All elements show K
Table 2
Percentage composition of elements in nickel oxide nanoparticles.
Element
Weight %
Atomic Weight %
Table 1
C (K)
O (K)
S (K)
Ni (K)
1.5
4.7
Percentage composition of elements in polyaniline particles.
0.87
0.19
0.84
37.13
4.36
Element
Weight %
Atomic weight %
26.81
C (K)
O (K)
S (K)
0.52
0.42
0.12
63.69
19.24
6.22
Ni
Atomic ratio = O
1
1
=
= NiO
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S. Jamil et al.
Chemical Physics Letters 776 (2021) 138713
transition.
Element
Weight %
Atomic %
C (K)
Ni (K)
O (K)
0.9
36.57
21.87
28.99
0.52
0.54
Fig. 6. EDX pattern of Polyaniline.
Fig. 9. FTIR spectrum of NiO.
3
.4. Fourier transform infrared microscopy
FTIR is used to locate the functional group of a compound. Spectrum
ꢀ 1
was recorded from 4000 to 500 cm . Metal oxide usually shows ab-
ꢀ 1
sorption under 800 cm because of interatomic vibrations. Nickel oxide
prepared from sol-gel method showed various peaks at 739, 2993, 3280,
ꢀ ꢀ 1
1
3
554 and 3664 cm . Peak 739 cm corresponds to Ni-O existence at
nanoscale and its stretching vibration. Physically adsorbed water on
sample surface also gives peaks in spectrum. Peaks at 3554 3554 and
Fig. 7. EDX pattern of NiO.
ꢀ 1
3
280 cm are associated with O-H stretching vibrations. A weaker peak
ꢀ 1
at 3664 cm corresponds to water evaporation from precursor. Results
Fig. 8. EDX pattern of PANI/NiO.
Fig. 10. FTIR spectrum of PANI.
5

S. Jamil et al.
Chemical Physics Letters 776 (2021) 138713
are in accordance with earlier reported articles [29]. FTIR spectrum of
NiO in given in Fig. 8.
During this process, cation radical sites are generated in monomer
(polymer) molecule, thus initiating polymer growth. Oxidized nitrogen-
containing structure attacks phenyl ring of another aniline molecule and
substitutes one proton of the ring. Both the ring and nitrogen-containing
structure lose one proton; after that, monomer units bind with each
other, and the chain becomes longer. Acidic medium (pH < 3) is
required to produce emeraldine salt of polyaniline [8].
FTIR spectrum of thread like Polyaniline is given in Fig. 9 depicting
ꢀ 1
various peaks at 2211, 2486, 2623, 3034, 3146 and 3458 cm . Poly-
aniline structure has nitrogen atom which C = N stretching vibration of
ꢀ 1
benzenoid ring coreesponding the peak at 2211 cm . Peak at 2486
ꢀ
1
cm shows diozonium salt. N-H and O-H region are usually present
ꢀ
1
ꢀ 1
above 3000 cm [19]. Peaks 3046 and 3146 cm shows the stretching
vibration of O-H and N-H groups respectively. –NH stretching is shown
2
ꢀ 1
by the peak at 3458 cm
.
Polyaniline/Nickel oxide composites are also prepared through
chemical oxidation method. Nickel oxide composites were added to
Polyaniline/Nickel oxide composite spectrum is given in Fig. 10
showing peaks at 739, 1485, 2547, 3225, 3458, 3584, 3787 cm 1. Peak
ꢀ
aniline and HCL solution and sonicated for 30 min before the addition of
APS for uniform dispersion. Polymerization completed through oxida-
tion. Spherical nickel oxide nanoparticles adjusted between the spaces of
polymer. Nickel oxides generates crosslinking between PANI chains
which causes expansion of chains and hence increases its surface area.
Nickel oxide make more orderly arrangement in polymer chains that
enhances its charge carrier mobility and free paths for electron transfer
[27].
ꢀ 1
at 739 cm corresponds to Nickel oxide. C-N of benzenoid ring shows
ꢀ 1
non-sysmmetric vibration at 1485 cm . Peaks at 3034, 3146, 3458
ꢀ
1
cm shows the stretching vibrations of O-H, N-H and –NH
2
functional
groups respectively.
Formation mechanism
Nickel nitrate hexahydrate was dissolved in distilled water and
+
2
stirred for half an hour where it disociates into its ions imparting Ni
and nitrate ions. Then the flask containing solution was kept into hot
bath at 70 ℃ and sodium hydroxide was poured slowly into it. This
mixing immediately form precipitates of nickel hydroxide giving
greenish colour to the mixture. Reaction continues until a gel like con-
4. Applications
+
sistency formed. Nickel hyroxide gel was washed to remove Na and
–
NO
3
ions. Gel was heated in oven and then calcinated at 400 ℃ to form
4.1. As fuel additive
NiO nanoparticles.
PANI/NiO composite proved as good fuel additive due to its crys-
talline nature. Metal oxide present in polymer imparts metallic charac-
teristics to it. As the organic molecule hits the crystalline surface of
additive the process of bubble formation starts which increase the
vapour pressure. More the interaction of organic molecules with addi-
tive, more bubbles are formed, and the result is increased vapour pres-
sure which ultimately reduces boiling point of fuel. Upon decreasing the
temperature of fuel, composites interferes in the crystallization process
of fuel and settles down into small spaces and hence decrease the
freezing point of fuel [16,15].
Polyaniline was prepared through chemical oxidation polymeriza-
tion method which involves the mixing of Aniline with HCL solution.
This step forms aniline hydrochloride. Low pH is required to produce
conductive emeraldine salt of polyaniline which is achieved by HCL.
Solution was then kept in ice bath to reach temperature about 5℃.
Addition of APS to solution is an exothermic process, so low temperature
helps in maintainace of polymer structure and complete polymerization.
Ammonium persulfate (APS) reacts with Aniline hydrochloride and give
rise to chain reaction through oxidation by creating anilinium radical.
Physiochemical properties of diesel have been studied such as pour
point, cloud point, flash point and fire point. Different concentrations of
PANI/NiO composites were added to diesel and effect of additive was
analyzed. To increase the efficiency of petrolleum products, various
additives are added to it. PANI/NiO composites have shown improved
efficeincy of deisel.
6

S. Jamil et al.
Chemical Physics Letters 776 (2021) 138713
Fig. 11. FTIR spectrum of PANI/NiO.
Fig. 13. Effect of Polyaniline-Nickel oxide composites on cloud and pour points
of diesel.
4
.1.1. Flash point and fire point
Flash point is lowest point at which vapours of fuel catches fire and a
additive’s concentration was increased. Cloud and pour point show the
decreasing trend which is because of interference in crystallization
process of fuel. As temperature of fuel decreases, nanoscale particles
started to fill in the spaces of fuel which eventually causes the depression
in freezing points. This application is particularly important in colder
areas where fuel can be avoided to freeze by adding fuel additives [14].
flash is produce where as fire point is that when fuel catches fire. Various
concentration of PANI/NiO composites ranges from 0 to 80 ppm were
added to diesel and subjected to open cup tester to determine flash point
◦
and fire points of diesel. Flash point were 71, 69, 68, 64 and 62 C for 0,
2
6
0, 40, 60 and 80 ppm of fuel additive where fire points were 76, 74, 71,
◦
9 and 67 C for 0, 20, 40, 60 and 80 ppm of fuel additive concentration
respectively. Fig. 11 shows the flash and fire point trends of fuel addi-
tive. Trend showed a decrease in flash and fire points. Fuel and petrol-
leum products are volatile in nature. Their volatility increases as the
concentration of additive is increased. This shows that PANI/NiO com-
posites have improved the ignition and combustion of diesel hereby
increasing its efficiency.
4.2. Catalytic reduction of dyes
Polyaniline, Nickel oxide and PANI/NiO composites are used as
catalyst for reduction of methyl orange (MO) and methylene blue (MB)
in the presence of sodium borohydride (NaBH ). Experiments were
4
monitored by using UV–vis spectrophotometer in presence of catalysts
dose and NaBH . 0.01 g of each catalyst was used. Maximum absorbance
4
4
.1.2. Pour point and cloud point
of methyl orange and methylene blue were 464 nm and 660 nm which
decreases with the addition of catalyst and NaBH4 as the time passed.
Cloud point is that point at which the fuel has waxy clouds in it and
pour point is the lowest temperature below which the fuel ceases to flow.
Fig. 12 shows the cloud point and pour points of diesel having PANI/NiO
composites as additive from 0 to 80 ppm. Cloud point depressed from
Catalytic reduction follows pseudo first order reaction as NaBH used in
4
excess. Fig. 13 shows the discoloration of dyes. Catalysts act as charge
transfer carriers to NaBH4 which causes the reduction dyes [10].
Reduction becomes kinetically feasible when dye is adsorbed on catalyst
4
℃ to 0℃ while pour point decreases from ꢀ 1℃ to ꢀ 4℃ as the
Fig. 12. Flash and fire point values of Polyaniline-Nickel oxide composites as fuel additive.
7

S. Jamil et al.
Chemical Physics Letters 776 (2021) 138713
Fig. 14. (a) Methyl orange reduction to colourless amines (b) Methylene blue reduction to solution.
Fig. 15. Mechanism of Reduction of Methyl orange and Methylene blue by using PANI/NiO composite.
surface. -N = N group is present in methyl orange which is degraded into
simple amines on reduction causing in discoloration of dye. BH4- dis-
rupts the azo bond of methyl orange [16,15]. Similarly in methylene
blue –N = N bond becomes –N-N which makes it colorless. Methyl
orange reduce slower as compared to methylene blue because of more
complex structure (see Fig. 14).
Reduction of Methyl orange and Methylene blue follows the pseudo
first order reaction as the NaBH-
1
4
present in large amount. Langmuir-
8

S. Jamil et al.
Chemical Physics Letters 776 (2021) 138713
Fig. 16. (a) Shows the ln(A
t
/A
0
) verses time for Methyl orange for 3 catalyts (b) shows ln(A
/A
t 0
t
) verses time of Methylene blue (c,d) shows the linear plot of ln(A /
0
A ) verses time for Kapp estimation of MO and MB for different catalysts.
Table 3
A comparative study of related reported products.
Composite
Applications
References
PANI/NiO
Thermal stability, decomposition and glass transition temperature (T
The thermal stability and conductivity of samples
Asymmetric supercapacitors (ASCs)
g
) of the composites
[23]
[32]
[9]
Binder free electrode for super-capacitor
Photocatalytic degradation of methylene blue
Visible Light Photocatalyst for Wastewater Treatment
Multicolored electrochromic thin films
Humidity Sensors
[24]
[34]
[33]
[31]
[30]
[12]
Anode for lithium ion batteries
Transport parameters such as electrical conductivity (
energy (w)
σ), charge localization length (α-1), most probable hopping distance (R) and charge hopping
[20]
Non-enzymatic glucose biosensor
Temperature dependent DC conductivity
[6]
[36]
Hinshelwood mechanism could define the catalytic reaction of PANI/
• PANI being a polymer is a good host, stabilizer or capping agent for
trapping Nickel oxide nanoparticles and hence enhances the dis-
persity and stability of Nickel oxide nanoparticles.
BH-
1
ions produce upon
NiO and dyes in presence of NaBH
ionization of NaBH Methyl orange and methylene blue dye
molecules along with BH
catalyst. Surface hydrogen transferred from BH
to dye molecules. Dye molecules reduces to colourless amines and BH
4
.
4
4
.
-
1
4
ions adsorb on surface of PANI/NiO
• PANI/NiO composites have large surface area as compared to pure
PANI which helps in better adsorption on dyes that results into faster
and increased reduction of dyes molecules.
-
1
4
to PANI/NiO catalyst
-
4
1
-1
2
oxidizes into BO [18].
9

S. Jamil et al.
Chemical Physics Letters 776 (2021) 138713
•
PANI is electrically conductive polymer that helps in charge transfer
products are used for catalytic reduction of MO and MB in presence of
from NiO to dye molecule. Composite promotes and channelize the
charge transfer due to its large surface area and hence results in
improved reduction rate.
4
NaBH . An increasing trend can be observed in Kapp values of catalysts
used for methyl orange i.e. 0.03 > 0.04 > 0.06 for PANI, NiO and PANI/
NiO. As prepared product is multi-functional, working efficiently as
catalyst as well as a fuel additive, making it versatile material for further
investigations and applications.
PANI/NiO composite proved as good fuel additive due to its crys-
talline nature. Metal oxide present in polymer imparts metallic charac-
teristics to it. As the organic molecule hits the crystalline surface of
additive the process of bubble formation starts which increase the vapor
pressure. More the interaction of organic molecules with additive, more
bubbles are formed, and the result is increased vapor pressure which
ultimately reduces boiling point of fuel as shown in Fig. 15. Upon
decreasing the temperature of fuel, composites interfere in the crystal-
lization process of fuel and settles down into small spaces and hence
decrease the freezing point of fuel. PANI and its various composites has
been widely used as catalyst for dye degradation.
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
References
[
[
1] A.N. Aleshin, Polymer nanofibers and nanotubes: charge transport and device
applications, Adv. Mater. 18 (2006) 17–27.
2] M.B. Askari, P. Salarizadeh, Binary nickel ferrite oxide (nife2o4) nanoparticles
coated on reduced graphene oxide as stable and high-performance asymmetric
supercapacitor electrode material, Int. J. Hydrogen Energy 45 (2020)
4
.2.1. Effect of different catalysts on Kapp value
Graph plotted between Ln(A /A ) and time for MO and MB in given
t
0
2
7482–27491.
in Fig. 16. These linear trends were used to estimate Kapp values for MO
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