Study on the Effect Mno

-Deposited Carbon Nanofiber Mat and

Their Electrochemical Performance

Rizka Ayu Yuniar, Widiyastuti and Heru Setyawan

Chemical Engineering Department, Institut Teknologi Sepuluh Nopember, Kampus ITS Sukolilo, Surabaya 60111,

Indonesia

Keywords: MnO

, Carbon nanofibers, Electrospinning, Relative humidity, Capacitors

Abstract: Electric energy storage technology has evolved along with the increasing of the human need for portable

electronic devices and the development of electric-powered vehicles, one of which is capacitors. Material that

is often used for capacitors is activated Carbon and requires a binder, but the binder reduces the performance

of activated carbon as an electrode. An alternative material that can be used as a substitute for activated Carbon

is carbon black. One type of carbon black is acetylene black (AB). AB has been widely used as an additive

for conductive additives in the electrode preparation process because it has a large and low-density specific

area. Poly (vinyl alcohol) (PVA) has the physical properties of hydrophilic and semi-crystalline polymers.

Some of the advantages of PVA are having good thermal stability, chemical resistance, good physical

property, and excellent biocompatibility. Based on this, PVA is very interesting to be developed as an

electroactive composite matrix containing acetylene black. PVA/AB composite carbon nanofiber is made

using electrospinning techniques. Further development of carbon nanofiber as an electrode material needs

modification with the addition of MnO

through immersion techniques. The results of the SEM and XRD test

showed that MnO

was deposited on the carbon nanofiber surface area. The effect of adding MnO

can

increase the capacitance of the PVA/AB composite CNF.

1. INTRODUCTION

Electric energy storage technology has developed a

lot with the increasing human need for portable

electronic devices and the development of electric-

powered vehicles. One of them is a capacitor, which

is an innovation in the world of energy storage

devices that have large energy and power density,

large charge storage capacity, fast charge/discharge

process (Zhang and Zhao, 2009). These advantages

have been widely used in various fields such as digital

technology, electrical machinery, additional power

units, and energy storage equipment (Pech et al.,

2010). The material often used for capacitors is

activated Carbon because it has high cost-

effectiveness and performance efficiency (Gamby et

al., 2001). Activated carbon electrodes still need

binders such as organic material/polymers to bind

particles, but the presence of binders reduces the

performance of activated carbon as an electrode.

One alternative material that can be used as a

substitute for activated Carbon is carbon black.

Because carbon black has amorphous properties and

has several advantages, such as the price is relatively

low and has availability in various types and sizes.

Based on the process, black carbon consists of

furnace black, thermal black, channel black, and

acetylene black. Acetylene black (AB), prepared by

the thermal decomposition technique of acetylene,

whose electrical conductivity is known. In addition,

AB has been widely used as an additive to conductive

additives in the electrode preparation process because

it has a large specific area and low density (Gamby et

al., 2001). Previous research has made composites of

polyurethane (PU)/CB, polyaniline (PANI)/CB, and

Polyvinyl alcohol (PVA)/CB (Xiong et al., 2015).

Poly (vinyl alcohol) (PVA) has the physical

properties of hydrophilic and semi-crystalline

polymers. Some of the advantages of PVA are having

good thermal stability, chemical resistance, good

physical property, and very good biocompatibility

(DeMerlis and Schoneker, 2003; Koski, Yim, and

Shivkumar, 2004). Based on this, PVA is very

interesting to be developed as an electroactive

composite matrix containing carbon black. PVA/CB

composites have been carried out in the form of fiber

238

Yuniar, R., Widiyastuti, . and Setyawan, H.

Study on the Effect Mno2-Deposited Carbon Nanoﬁber Mat and Their Electrochemical Performance.

DOI: 10.5220/0009445602370243

In Proceedings of the 1st International Conference on Industrial Technology (ICONIT 2019), pages 238-244

ISBN: 978-989-758-434-3

using electrospinning techniques, because they can be

applied in a variety of fields, have a wide specific area

and high porosity.

In recent years, the electrospinning technique has

been widely using to develop nanoscale diameter

fibers. Although the electrospinning easy to use, the

jet formation of the spinning dope is affected by the

electrospinning condition. There is a parameter

process that is influencing various fiber formation and

fiber properties. Moreover, to get form fiber from the

electrospinning with good characteristics, the

ambient condition surrounds the chamber has to be

controlled carefully during the electrospinning

process. Fundamental processing condition have

already reported which include applied voltage

(Demir et al., 2002; Lee et al., 2004; Zhao et al.,

2004), viscosity (Mit-uppatham, Nithitanakul and

Supaphol, 2004; Shenoy et al., 2005), surface tension

(Zheng et al., 2014) and conductivity and dielectric

constant (Choi, Xue,) (Choi et al., 2004; Xue et al.,

2014). Among the ambient parameter such as

temperature and relative humidity also the most

important influence the fiber formation. There is a

Polymer such as polystyrene fibers resulted in larger

diameter at higher humidity (Kim et al., 2004;

Fashandi and Karimi, 2012) and polyetherimide

(Ogulata and İçoğlu, 2013). Various of humidity also

generate porous fibers by electrospinning

polycaprolactone (PCL), poly L-lactic acid (PLLA)

and polyvinylpyrrolidone (PVP) (Yazgan et al.,

2017).

Manganese dioxide (MnO2) has many

applications in industrial fields, including reagents in

organic synthesis, as inorganic pigments in ceramics,

and as electrodes in batteries. The use of MnO2 as an

electrode has several advantages, including

inexpensive and environmentally friendly (Yu et al.,

2011). Recently, there are several combination

between Carbon with MnO2 including carbon

nanofiber (CNF)/MnO2 with redox reaction of

KMnO4 solution (Ma et al., 2016), CNT/MnO2 with

hydrothermal reaction of KMnO4 solution (Xia et al.,

2012) and ACNF/MnO2 (Wang et al., 2013).

Here, we reported the electrodes prepared via

electrospinning of PVA/AB into nanofiber mats,

which were heat treated. Before that, polyvinyl

alcohol (PVA) was examined at various relative

humidity conditions to obtain fiber shape, fiber

surface, and fiber diameter. MnO2 crystals were

deposited on the surface of the CNFs by the

immersing of aqueous KMnO4. The effect of MnO2

crystal on the surface morphology with a varied mass

ratio of CNFs versus KMnO4 and electrochemical

properties were investigated.

2 EXPERIMENTAL

2.1 Materials

Polyvinyl alcohol (PVA) technical grade and

acetylene black (AB) were purchased from SAP

chemicals and were used directly without further

purification. Potassium permanganate (KMnO4) was

purchased from Sigma Aldrich. All of the chemicals

or materials were used directly without further

purifications.

2.2 Synthesis of Carbon Nanofiber

The synthesis procedure for PVA/Acetylene Black

(AB) could be explained as the following. PVA

powder was mixed with distilled water under stirring

for about an hour at 80 °C. Then, Acetylene Black

was added to the PVA solution under constant stirring

for 30 min. The mixture was sonicated at 50 °C for 4

hours to achieve the solution. Then the solution was

injected into a 50 ml plastic syringe, which was fitted

in an electrospinning apparatus to start spinning the

PVA/AB solution. The spinning parameters were

high voltage 10 kV (positive) was applied to the tip

of syringe to achieve polymer jets, and negative was

applied to the rotating cylinder, nozzle inside

diameter 0.6 mm (23G), temperature in chamber 25

°C and relative humidity (RH) in chamber hold on 60

% where RH conditions were precisely regulated

using dried silica and dehumidifier. The feed rate of

the solution was controlled by means of a Cole

Parmer Scientific syringe pump at 1 mL/h. The

products were placed in a dry cabinet for 24 hours,

previously further characterization.

Samples of 50 mm  30 mm of electrospun

nanofiber mats were placed into a sealed glass jar for

iodine treatment in a muffle furnace (Themolyne) at

80 °C for 24 h. The glassed jar was contained iodine

crystal with mass ratio iodine crystal versus mats of

1:2 to vaporize the iodine. After that, the sample was

removed from the oven and naturally cooled down to

room temperature. Iodine treatments are necessary for

the preparation of carbon nanofiber with the desired

morphological and structure.

The nanofiber mats were thermostabilized and

carbonized in a Lindberg tubular furnace with heating

procedures as follows: (1) The temperature was

increased from 30 to 200 °C; (2) 200 to 400 °C; (3)

400 to 600 °C, each step the temperature was holding

for 15 minutes. (4) The temperature was increased

from 600 to 800 °C; (5) the temperature remained at

800 °C for an hour; and (6) the sample was cooled

down to room temperature. During the carbonization

Study on the Effect Mno2-Deposited Carbon Nanoﬁber Mat and Their Electrochemical Performance

239

process, constant nitrogen flow was maintained

through the tube.

2.3 MnO

deposition on surfaces

carbon nanofibers (CNFs)

MnO

was deposited on the surface of the carbon

nanofibers by the simple method degradation of

KMnO

, as represented in the literature (Ma et al.,

2016). Firstly, a certain amount of different KMnO

concentration was dissolved in 10 mL distilled water

and stirred until the KMnO

was fully dissolved.

Mass ratios for every two CNFs versus KMnO

were

1: 1 and 1: 2. The CNF was immersed in the KMnO

solution at 65 °C for 4 hours. During immersion, the

color of the solution changed from purple into brown.

The MnO

-deposited CNFs (CNFs-MnO

) were

removed from the solution, rinsed with distilled

water, and dried overnight in an oven at 80 °C. The

MnO

-CNFs obtained under this condition using the

KMnO

concentrations listed above are denoted to as

CNF-MnO

(1:1) and CNFs-MnO

(1:2). Note that

the mass ratio in here represents the mass ratio of

CNFs mat to KMnO

during preparation.

3 RESULT & DISCUSSION

3.1 The effect of relative humidity on

PVA nanofiber

Relative humidity (RH) is one of the parameters

prosses that affected morphology nanofiber.

Temperature and humidity of the environment are

very much influencing the physical characteristic due

to the effect of solvent vaporization and solution

sensitivity on the drying rate of the solution. This

includes the performance of nanofiber forming i.e.,

smooth fiber, bead or beadless, and fiber diameter.

Interaction between the solution and the surrounding

water vapor should be considered on fiber diameter.

In this study, the effect of RH on morphology

nanofiber (diameter and shape) is investigated based

on PVA polymer solutions with a concentration of 15

% w/v. As shown in Figure 1, smaller diameter PVA

fibers spun from the higher humidity was found from

the same concentration. A possible reason for this

condition is due to slower solvent evaporation that

water condensing on the surface of electrospinning

was absorbed into the solution from the environment

during the electrospinning process, and it was related

to lower viscosity. Mean fiber diameter was shown to

reduce from 300 nm at 50 % relative humidity to 250

nm at 70 % relative humidity. Nevertheless, the lower

relative humidity may also be led to rapid solvent

vaporization that may cause an increase in the

solidification rate. Thus, the larger fiber diameter has

resulted.

The chamber of electrospinning is not a vacuum,

and there are many slots on the wall. Therefore in the

next step, the relative humidity was held on at 60%,

caused it is relatively simple to control with

dehumidifier during the electrospinning process.

Figure 1 : SEM images of PVA 15 % w/v electrospun

product at RH : (a) 70 % (b) 60 % (c) 50%

3.2 Synthesis Carbon Nanofiber/MnO

MnO2 was deposited by immersing Carbon

Nanofiber (CNF) composites in the KMnO

solution.

Carbon nanofibers were formed from the mixture

between PVA and Acetylene black (AB) with AB

concentration 10 and 15 wt. % based on PVA powder.

In the previous study, AB concentration influenced

the shape and diameter fibers (Yuniar et al., 2019).

The AB concentrations listed above are denoted to as

10CNFs-MnO

(1:1), 10CNFs-MnO

(1:2) , 15CNFs-

MnO

(1:1) and 15CNFs-MnO

(1:2).

Figure 4 shows the SEM images CNFs-MnO

composites where there are particles deposited on the

surface of CNF, which indicate the presence of

MnO

. After depositing MnO

by a redox reaction

with KMnO

solution, the morphology of CNFs in

contrast to that of CNFs on the previous study that

CNFs before immersing was smooth fibers (Yuniar et

al., 2019). During the immersion of CNF in the

KMnO

solution, the color changed from purple to

dark brown that indicates MnO

had been formed

(Fuenmayor et al., 2013). For 10CNFs-MnO

(1:1)

PVA 15 % w/v

b c

ICONIT 2019 - International Conference on Industrial Technology

240

and 15CNFs-MnO

(1:1), the surface area of CNFs

became rough, and nanoparticles of MnO

can be

exposed, as shown in Figures 1a and 1c. For 10CNFs-

MnO

(1:2) and 15CNFs-MnO

(1:2), which is

prepared in a higher mass ratio of KMnO

, the large-

sized particle of MnO

are deposited on the fiber

surface. Figures 1b and 1d show that the particles of

MnO

appear uneven on the surface of the fiber and

are more likely to form agglomerates around fiber

nods. It tends to make a layer above the fiber surface

so that the fiber structure is covered by the layer

above it. The previous study reported that smaller

particles like microscale that have smooth texture on

the surface, it takes adhesion of particle initially on

the surface, and that means the particle MnO

(Chow,

2003). When the carbon fibers were immersed in a

KMnO

solution at 65 °C, CNFs was directly reduced

the KMnO

The overall reaction is described as

follows (Jin et al., 2007):

4KMnO

+ 3C + H

 4MnO

+ K

+ 2 KHCO

Carbon fibers provided not only as a reagent.

Based on the redox reaction of KMnO

carbon fibers

not only as a reagent but also as substrate and agent

collector of the current. The rough surfaces of carbon

fibers, it is becoming the new of surfaces carbon

fibers, and it causes the carbon fibers are intrinsically

less positive (Chi et al., 2014). During the process of

nucleation and MnO

nanoparticle, the more enough

nucleation area, the more area can wipe out the

essence of creating a new surface (Chi et al., 2014).

The structure of the MnO

particle on the surface

carbon nanofibers was analyzed by XRD analysis

(X’pert PRO PANalytical). As shown in Figure 3, the

XRD patterns of CNFs-MnO

shows the two broad

diffractions approximately 17.5° and 25.3°. The

spectrum of the carbon nanofibers (CNFs) can be

indexed (002), which represented the graphite carbon

structures. Broad peak diffraction revealed that the

size of graphite might be in the nanometer scale and

the degree of graphitic relative low (Zhou et al.,

2010). The diffraction peak at 36.6° associated with

the (101) crystallographic planes of ramsdellite-type

of MnO

(JCPDS 39-375)

(Ghodbane, Pascal and

Favier, 2009)

Nevertheless, the peak just appeared in

10CNFs-MnO

(1:1). Consequently, CNFs-MnO

was reheated on tubular furnance at 300 °C for 1 h

under constant nitrogen flow. It might be removed

impurities of the CNFs-MnO

Figure 2 : SEM images after immersing KMnO4 solution

and dried at 80 °C : (a) 10CNFs-MnO2 (1:1) (b) 10CNFs-

MnO2 (1:2) (c) 15CNFs-MnO2 (1:1) (d) 15CNFs-MnO2

(1:2)

Figure 3 : XRD patterns after immersing KMnO4 solution

and dried at 80 °C : (a) 10CNFs-MnO2 (1:2) (b) 10CNFs-

MnO2 (1:1) (c) 15CNFs-MnO2 (1:2) (d) 15CNFs-MnO2

(1:1)

Figure 4 shows the XRD patterns of CNFs-MnO

that reheated at 300 °C. The two broad diffractions

approximately at 36.6° and 44.4° in the spectrum can

be indexed (101) and (210), respectively, represent

the presence of ramsdellite-type MnO

at all the

samples (JCPDS 39-375) (Ghodbane, Pascal and

Favier, 2009). All of the peaks in the spectrum are

broad (poor crystallinity), and weak intensity, due to

typically adhesive MnO

nanoparticle (Ma et al.,

2016) yet the peaks from XRD analysis proved the

presence of MnO

in four samples. XRD pattern of

15CNFs-MnO

(1:2) has sharper peaks than those of

15CNFs-MnO

(1:1), 10CNFs-MnO

(1:2) and

10CNFs-MnO

(1:1), indicating that MnO

on the

surfaces of 15CNFs-MnO

(1:2) might have a higher

Study on the Effect Mno2-Deposited Carbon Nanoﬁber Mat and Their Electrochemical Performance

241

degree of crystallinity. Nevertheless, the nanofiber

structure is lost when reheated at 300 °C. As shown

in Figures 5a and 5b, the 10CNFs-MnO

(1:1) and

10CNFs-MnO

(1:1) surface fiber became rough. The

structure nanofibers were completely gone.

Figure 4 : SEM images after immersing KMnO4 solution

and dried at 300 °C : (a) 10CNFs-MnO2 (1:1), (b) 10CNFs-

MnO2 (1:2), (c) 15CNFs-MnO2 (1:1), and (d) 15CNFs-

MnO2 (1:2)

Figure 5 : SEM images of samples (a) 10CNFs-MnO

(1:1), (b) 10CNFs-MnO

(1:2), (c) 15CNFs-MnO

(1:1), and (d) 15CNFs-MnO

(1:2) after immersing

KMnO

solution and dried at 300 °C

To evaluate the electrochemical performance of

CNFs-MnO2 as electrodes in capacitors, cyclic

voltammetry (CV) measurements (Autolab PGSTAT

302N) were used on the CNFs-MnO

in a two split

electrode system while using 1 M Natrium thiosulfate

(Na

) as an electrolyte. The CV curve was

performed from -1 to 1 volt at scan rates of 100 mV.s-

1. The capacitance was estimated from the results of

CV curves using the equation   /

, where the I is the current, ʋ is applied

potential,  is the mass of the CNFs-MnO

electrode,

 is the scan rate, and  is the potential delta window

for the measurement of CV. In the two split electrode,

the aluminum band was sharped circular with

diameter 12 mm and used nanocellulose paper that

soaked in the electrolyte solution for 24 hours as the

separator for CV measurements. This measurement

was operated without a binder.

Figure 6: CV curves of the CNF-MnO

that dried at 300 °C

As shown in Figure 6, CV plots revealed the area

of 15CNFs-MnO

(1:2) is larger than others. It might

be 15CNFs-MnO

(1:2) acquired higher crystalline

then others with uniform distribution of that would

facilitate for reversible ion phenomenon, which is

proved by XRD pattern as shown in Figure 4. It is

showed that the CNF after immersing KMnO

solution that growth MnO

particle on the surfaces of

fibers able to increase the capacitance. The high

capacitance can be associated with the existence of

MnO

among porous structures that able to cut off the

electron diffusion path to provide ion and electron

exchange. That means the redox reaction can be

increased. Nevertheless, these capacitance values

were relatively low compared to other capacitors'

electrodes. It is caused the relatively poor electrical

conductivity of the MnO

decorated on the surface of

CNFs. MnO

possess with low crystalline was

resulted in low concentration KMnO

that used for

immersing carbon nanofiber. The capacitances of

CNFs-MnO

are shown in Table 1.

Table 1 : Capicatance of CNF and CNFs-MnO

Variable Capacitance (µF/g)

CNF 27

15CNFs-MnO2 (1:1) 32

15CNFs-MnO2 (1:2) 231

10CNFs-MnO2 (1:1) 36

10CNFs-MnO2 (1:2) 29

a b

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242

4. CONCLUSIONS

The study showed that during electrospinning, the

diameter of nanofibers could be arranged by relative

humidity. MnO

nanocrystals were successfully

deposited on the surfaces of CNFs by the redox

reaction of immersing the KMnO

solution. The

electrochemical performance of CNFs-MnO

designated might be capable of electrodes in a

capacitor with optimization.

ACKNOWLEDGMENTS

The authors are grateful for the financial support

provided by the Ministry of Research, Technology,

and Higher Education of the Indonesia Government

Directorate of research and public service through the

research grant under Contract No.

5/E1/KP.PTNBH/2019.

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