Jurnal Dinamika Vokasional Teknik Mesin Vol.
No.
October 2024, pp.
109 - 120
https://journal.
id/index.
php/dynamika/issue/view/77816 ISSN: 2548-7590.
DOI: 10.
21831/dinamika.
Electrochemical Performances of Nitrogen-doped Carbon/MnO2 Composite Supercapacitor Electrode in KI-added Na2SO4 Electrolyte Sutarsis1.
Demas Muhammad Abyan2.
Fahrul Ardian Firmanda Kussuma3.
Yusuf Pradesar4.
Agung Purniawan5 1,2,3,4,5Department of Material and Metallurgical Engineering.
Faculty of Industrial Technology and System Engineering.
Institut Teknologi Sepuluh Nopember.
Surabaya.
Indonesia
Article Info
ABSTRACT
Article history:
In this study.
Nitrogen-doped Activated Carbons (NAC) with different Nitrogen concentrations (NAC1.
NAC2.
NAC.
and Manganese Dioxide (MnO.
were composited to make the hybrid active material for supercapacitor electrodes to improve the energy density of NAC by adding the pseudo-redox capacitive properties of NAC/MnO2 composite electrode.
NAC active material was made from the pyrolyzing biomass carbon and Polyaniline mixture at 800 AC in a nitrogen atmosphere for 2 hours.
NAC/MnO2 hybrid material was synthesized by heating NAC: MnO2 with a ratio of 5:1 at 400 AC for 2 Peaks analysis of X-ray diffraction of NAC/MnO2 powder shows that the MnO2 phase was formed as a composite with NAC.
The electrochemical performance of the NAC3/MnO 2 electrode exhibited the highest capacitance of 168 Fg-1 at a scan rate of 5 mVs-1 in Potassium Iodide (KI)-added Na2SO4 electrolyte.
According to the Cycle Voltammetry (CV) measurement, the NAC3/MNO2 composite electrode shows hybrid capacitive behavior consisting of pseudoredox and double-layer electrostatic energy storage mechanisms in KI-added Na2SO4 electrolyte.
NAC3/MnO2 composite electrode demonstrates a high energy density of 22 Whkg -1 at 5 mVs-1.
Received Sep 22, 2024 Revised Oct 01, 2024 Accepted Oct 07, 2024 Published Oct 08, 2024 Keywords:
Aqueous Electrolyte.
Activated Carbon.
Nitrogen Doping.
Supercapacitor.
Corresponding Author:
Sutarsis Department of Material and Metallurgical Engineering.
Faculty of Industrial Technology and System Engineering Institut Teknologi Sepuluh Nopember Surabaya 60111.
East Jawa.
Indonesia Email: sutarsis@its.
INTRODUCTION
The most popular of the world's concerns today is the need for a green energy transition associated with renewable energy usage.
Renewable energy supports global commitments to reduce greenhouse gas emissions.
To realize the greenhouse gas reduction program, the Indonesia Ministry of Industry has launched a green electrification program in the transportation sector for 38,491 electric vehicles by 2024 in Indonesia (Dewan Energi Nasional, 2.
Conversely, renewable energy-based green electricity has unstable and intermittent characteristics that lead to big problems in mobile applications, so energy storage is needed to overcome the drawbacks.
Jurnal Dinamika Vokasional Teknik Mesin.
Volume.
09 No.
October 2024 | 110 The primary energy storage of electric vehicles is batteries.
However, the battery has high energy density but low power density.
It affects the speed of charging and discharging the battery, causing acceleration in electric cars to be slow and problematic in uphill conditions (A.
Nurohmah, 2.
The supercapacitor, as one of the promising energy storages, offers high power density behavior over the batteries.
In addition, supercapacitors have other advantages, such as long cycle life and high efficiency, and are considered more environmentally friendly (K.
Wang et al.
, 2.
The high-power density of supercapacitors can be used effectively by utilizing the kinetic energy generated during braking, which also positively impacts the mileage of electric vehicles.
However, supercapacitors' relatively low energy density remains an obstacle, so they cannot be used as the primary energy storage (F.
Naseri et al.
, 2.
Supercapacitors can also be complementary and used with batteries in many applications, such as aerospace, military, and home electronics.
To widen the role of supercapacitors as primary energy storage, enhancing energy density without reducing the power density of the supercapacitor is necessary by increasing the capacity of active material and enhancing the voltage window of electrolytes, including applying hybrid technology.
According to the energy formula.
E = A CV2, the energy density of the supercapacitor could be improved through increased capacity and an electrochemical stability Potential window (Y.
He et al.
First, increasing the surface area increases the capacitance of the active material of electrodes.
Second, the voltage window can be enlarged by choosing the electrochemically stable electrode material and electrolyte.
Lastly, both capacitance and operational potential can be improved by making a hybrid supercapacitor (E.
Redondo et al.
, 2.
Improving the energy storage performance of active materials has been widely studied.
The most common strategies are increased surface area by reducing particle size and porous engineering (N.
Saeidi et al.
, 2.
(D.
Salinas-Tores et al.
, 2.
(F.
Taufani et al.
, 2.
Both methods have greatly affected energy density improvement, but they still do not meet the requirements for automotive applications.
another way, hybrid system supercapacitors have offered significant enhancement of energy storage mechanism in the electrode material.
The hybrid active material forms dual energy storage behavior in the aqueous and organic electrolyte system to increase its capacitance (N.
Vangapally et al.
, 2.
Dopant heteroatoms and metal oxide on carbon-based active material have become effective methods to improve the capacitive properties by introducing pseudo-redox reactions on double-layerbased capacitor material (Abbas et al.
, 2.
(J.
Choi et al.
, 2.
We also call it a hybrid material.
As reported in the previous study, nitrogen heteroatom has improved activated carbon's energy density by increasing electric and electronic conductivity and pseudo-redox formation (M.
Jing et al.
, 2.
a nitrogen precursor.
Polyaniline (PANI) is a conducting polymer with high electronic conductivity used to synthesize nitrogen-rich carbon in many applications.
MnO2 metal oxide introduces redox reactions by transferring electrons from the adsorbed charge carriers (P.
Konnerth et al.
, 2.
Jurnal Dinamika Vokasional Teknik Mesin.
Volume.
09 No.
October 2024 | 111 Unfortunately, metal oxides have the disadvantage of low electrical conductivity.
Therefore, incorporating nitrogen-rich carbon (NC) with MnO2 has improved the kinetic, cycle life, stability, and electrical conductivity of pseudo-capacitive-based electrodes (P.
Konnerth et al.
, 2.
In another work, the MnO2/NC electrode exhibited better specific capacitance of 1.
5iA1.
9 times greater than activated carbon, which is 245 Fg-1 (T.
Huang et al.
, 2.
Moreover, the 1 M Na2SO4 electrolyte has been used to avoid the destruction of MnO2 in acidic electrolytes.
The optimum energy density of the MnO2/NC electrode is 39.
9 Whkg-1 with a power density of 642 Wkg-1 (J.
Choi et al.
, 2.
In this work, the NAC/MnO2 composite electrode was studied for the first time in a KI-added Na2SO4 electrolyte system.
KI as a pseudo-redox additive is expected to enhance pseudo-redox reaction on the carbon surface in the aqueous electrolyte, as reported by Metilde et al, 2022.
Furthermore, the composite electrode's material structure and electrochemical behavior were also examined to analyze their correlation.
METHOD
1 Synthesis of nitrogen-doped Activated Carbon (NAC) Biomass carbon.
Polyaniline as nitrogen precursor, and Potassium Hydroxide (KOH) as activation agent were mixed with a ratio of 1:0:3, 0.
9:0.
1:3, 0.
7:0.
3:3, 0,4:0.
6:3 to make nitrogen-doped activated carbon (NAC).
The sample was put into a ceramic crucible and heated at 800 AC in a nitrogen gas atmosphere for 2 hours.
The obtained activated carbon with nitrogen content was washed using 1 M HCl solution to remove potassium compounds and impurities on the surface, then dried at 85 AC for 12 To reduce the particle size of activated carbon, a Ball milling process was carried out at 300 rpm for 12 hours.
Finally.
Pristine activated carbon (AC) and Nitrogen-doped activated Carbon (NAC1.
NAC2, and NAC.
were obtained for each mixture composition ratio.
2 Doping process of MnO2 metal oxide The MnO2 doping process was carried out by mixing NAC with MnO2 powder in a ratio of 5:1.
The mixture was stirred in 50 ml of deionized water and then dried in the autoclave for each sample.
The dried sample was heated at 120 AC in an electric oven for 4 hours.
The sample was then washed to a neutral pH with deionized water and dried at 80 AC in a vacuum for 8 hours.
Nitrogen-doped activated carbon/MnO2 composite is formed by heating the NAC and MnO2 mixture at 400 AC in a nitrogen gas 3 Material characterization The formed phase and crystal change of the obtained NAC/MnO2 composite was analyzed using a Philips X'Pert Pro.
Materials Powder Diffractometer with two thetas scanning from 20 to 90 .
A scanning electron microscope (SEM) FEI INSPECT S50 was used to observe the morphology of NAC/MnO2 composite.
Jurnal Dinamika Vokasional Teknik Mesin.
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09 No.
October 2024 | 112 4 Electrochemical measurement The supercapacitor electrodes were made from a mixture of NAC/MnO2 active material.
Super-P (Carbon Blac.
, and Polyvinylidene Fluoride (PVDF) with a ratio of 8:1:1.
The N-Methyl Pyrrolidone solution was added to form a slurry while stirring for 4 hours.
The slurry was coated on nickel foam, the coin cell size for the anode and cathode, and then dried in a vacuum oven at 50 AC for 24 hours.
The electrochemical performance of the cell supercapacitor was measured using Biologic SP-300 in 1 M Na2SO4 electrolyte with or without 0.
05 M Potassium Iodide (KI) additional for 5 to 200 mVs-1 scan Cyclic Voltammetry (CV) testing was done using the CorrTest tool with the three-electrode The reference electrode used the Saturated Calomel Electrode (SCE) with a graphite counter RESULTS AND DISCUSSION .
The effect of nitrogen heteroatom and MnO2 metal oxide on the phase and structure crystal changes of the NAC/MnO2 composite have been examined using X-ray diffraction.
The diffraction peaks of AC.
NAC1.
NAC2, and NAC3 samples show a similar spectrum of the corresponding carbon peaks with 2 of 24 and 43, as depicted in Figure 1.
The broad carbon peak indicates that the carbon has an amorphous structure.
As shown in Figure 1, the diffraction peaks of carbon shift to a higher diffraction angle with the nitrogen doping concentration.
This peak shift is caused by lattice distortion caused by nitrogen dopant, which causes a defect (R.
Kumari et al.
, 2.
Table 1.
FWHM and Crystal Size differences of AC.
NAC1.
NAC2 and NAC3.
Pos.
FWHM
Average Crystal Size .
Th.
Th.
NAC1
NAC2
NAC3
Sample From 2 theta of the peak position, it can be seen that the peak shift occurs more to the right when the polyaniline concentration ratio is added, namely at an angle of 23.
75 on activated carbon without doping and progressively to the right sequentially up to an angle of 25.
The Full Width Half Maximum (FWHM) shows nitrogen doping also causes a change in crystallinity, whereas the broader addition of NAC3 FWHM indicates that the carbon loses its crystallinity.
This is due to the involvement of nitrogen, which is formed as a substitute for carbon atoms, which causes a lack of crystallinity (L.
Hlekelele et , 2.
The obtained NAC samples exhibited a different crystal size, as listed in Table 1.
The crystalline size was determined by using the Scherrer equation.
The crystal size of the carbon decreases as the Jurnal Dinamika Vokasional Teknik Mesin.
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09 No.
October 2024 | 113 nitrogen concentration ratio increases, which is 1.
358 nm, 1.
365 nm, and 1.
160 nm for NAC1.
NAC2, and NAC3, respectively.
The crystallite size is inversely proportional to the FWHM (Scherrer's therefore, the smaller the FWHM .
eans sharper pea.
, the more crystallite dimension.
analyze the effect of Mangane oxide, the NAC1/MnO2, and NAC3/MnO2 composite were examined to identify the phase formation of the composite, as shown in Figure 2.
The most pyrolusite (-MnO.
phase is formed as x-ray diffraction examination.
The phase formation is obtained through a hydrothermal process followed by annealing treatment (R.
Yang et al.
, 2.
Figure 1.
Peak diffraction of AC.
NAC1.
NAC2, and NAC3 powders measured using an X-ray diffractometer.
NAC3/MnO2 NAC1/MnO2 Figure 2.
Peak diffraction analysis of NAC/MnO2 Composite shows -MnO2 and Mn3O4 phases Table 2.
FWHM and Crystal Size differences of various NAC/MnO2 composite.
Pos.
FWHM
Average Crystal Size .
Th.
Th.
NAC1/-MnO2 NAC3/-MnO2 NAC1/Mn3O4 NAC3/Mn3O4 Sample Jurnal Dinamika Vokasional Teknik Mesin.
Volume.
09 No.
October 2024 | 114 According to the diffraction peaks of the composite, the two highest peaks were identified at 2=28 and 2=35.
9 for -MnO2 and Mn3O4, respectively.
NAC1/MnO2 and NAC3/MnO3 also show different crystal sizes as indicated by different FWHM.
The NAC3/MnO2 exhibited the lowest crystal The ionic and electronic conductivity of materials depends on their crystal structure.
Materials with low crystallinity behave with high ionic conductivity.
conversely, electrical conductivity properties come from high crystallinity materials (L.
Yang et al.
, 2.
Figure 3.
Morphology of Carbon and MnO2 was observed by Scanning Electron Microscope (SEM) of .
NAC1/MnO2, .
NAC2/MnO2, .
NAC3/MnO2, .
NAC1/MnO2 with higher magnification.
Table 3.
The capacitance of NAC/MnO2 composite electrodes was measured using CV measurement at 5 mVs-1.
Electrolyte Na2SO4 KI-added Na2SO4 Sample Specific Capacitance (Fg-.
NAC1/MnO2 NAC2/MnO2 NAC3/MnO2 NAC1/MnO2 NAC2/MnO2 NAC3/MnO2 A scanning electron microscope (SEM) was applied to observe the morphological difference between NAC1/MnO2 and NAC3/MnO2 samples.
As seen in Figure 3, the morphology of MnO2 shows nanorod-like incorporation with NAC1.
NAC2, and NAC3 to form an NAC/MnO2 composite, which has a MnO2 nanorod size of 600-800 nm.
This structure is formed due to a reaction in the hydrothermal treatment and the number of ClOe ions in the synthesis process (L.
Yang et al.
, 2.
As presented in Figure 2, the fractional of the MnO2 phase formed in NAC1 is higher than in NAC3 according to the amount of the phase peak diffraction.
To analyze the charge storage mechanisms on the NAC/MnO2 composite electrode.
Cyclic Voltammetry (CV) measurement was carried out with scan rate parameters of 5 to 200 mVs -1 in 1 M Jurnal Dinamika Vokasional Teknik Mesin.
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09 No.
October 2024 | 115 Na2SO4 electrolyte with or without 0.
05 M KI additional.
Table 3 shows the NAC/MnO2 electrode capacitance with a scan rate of 5 mVs-1.
The NAC3/MnO2 electrode shows higher capacitance than another NAC/MnO2 composite in Na2SO4 electrolyte with or without additional KI.
The CV curve of NAC3/MnO2 behaves in a rectangular shape near the charge-discharge curve of the ideal double-layer electrical supercapacitor, as depicted in Figure 4.
All NAC/MnO2 composite electrodes exhibited electrostatic double-layer charge storage in Na2SO4 electrolyte with a potential window of 0.
8 V.
Compared to the previous study, the capacitance of NAC/MnO2 electrode tends to be lower than the pristine MnO2 electrode due to the significant difference in particle size of the two metal oxides (Chen Ye et al.
, 2.
Meanwhile, the capacitance of all NAC/MnO2 composite electrodes in the KI-added Na2SO4 electrolyte tends to be higher than the same composite electrodes in the Na2SO4 electrolyte.
The charge storage mechanism of the NAC/MnO2 composite electrode exhibited a hybrid energy storage mechanism of pseudo-redox over double-layer electrostatic in KI-added Na2SO4 electrolyte.
As listed in Table 3, the increased MnO2 ratio significantly improves the capacitance of the NAC/MnO2 composite MnO2 reacts with KI additives to build a pseudo-redox reaction on the NAC/MnO2 composite electrolyte, as shown in Figure 7.
The NAC3/MnO2 composite electrode exhibited the highest capacitance of 168 F/g, as evaluated by CV measurement at 5 mV/s in KI-added Na2SO4 electrolyte.
Pseudo-faradic reactions between the electrode surface and the electrolyte occur through adsorption and reduction-oxidation .
The capacitance of the NAC/MnO2 composite electrode is increased due to the insertion of Na ions from the electrolyte into the MnO2 lattice.
Potassium Iodine (KI) additive added to pseudo-capacitance properties caused Na2SO4 electrolyte to synergize in a redox reaction (E.
Taer et al.
, 2.
As reported in a previous study, the KI additive has increased the capacitance by providing an extra pseudo-redox reaction of carbon-based electrodes in the aqueous electrolyte (D.
Xu et al.
, 2.
Figure 4.
Charge-discharge curve profile of various NAC/MnO2 composite electrodes examined using CV measurement at scan rate 5 mVs-1 in Na2SO4 electrolyte.
Jurnal Dinamika Vokasional Teknik Mesin.
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09 No.
October 2024 | 116 Table 4.
The capacitance of the NAC3/MnO2 electrode was calculated using CV measurement at various scan rates.
Sample NAC3/MnO2 Scan Rate Specific Capacitance .
V/.
(Fg-.
Table 4 shows that the capacitance of all NAC3/MnO2 tends to reduce with an increased scan rate of CV measurement in Na2SO4 electrolyte.
The greater the scan rate, the greater the voltage change rate, which causes the charge to be unable to stick to the surface (M.
Sarno et al.
, 2.
It indicates that the electrostatic charge storage of NAC/MnO2 electrodes is complex to form at a high rate of chargingdischarging.
Figure 5.
Charge-discharge curve profile of NAC3/MnO2 composite electrode examined using CV measurement at various scan rates in Na2SO4 electrolyte.
The CV measurement with various scanning rates was conducted in Na2SO4 electrolyte for the NAC3/MnO2 composite electrode.
The NAC3/MnO2 electrode was found to behave like an ideal EDLC with a rectangular shape of the charge-discharge curve at a low scan rate (P.
Charoen-amornkitt et al.
, as presented in Figure 5.
Meanwhile, the higher scan rate of the NAC3/MnO2 electrode shows a higher gradient of the CV curve, indicating increasing resistance during the charging-discharging process (H.
Gul et al.
, 2.
Jurnal Dinamika Vokasional Teknik Mesin.
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09 No.
October 2024 | 117 NAC1/MnO2 NAC2/MnO2 NAC3/MnO2 Figure 6.
The charge-discharge profile of the obtained NAC/MnO2 composite electrode was measured by Cycle Voltammetry at 5 mVs-1 in KI-added Na2SO4 electrolyte.
The higher charge-discharge rate of the supercapacitor electrode forms the charge storage structure with a disordered charge-pair arrangement and is more unstable, leading to lower capacitance.
When the scan rate is increased, the ion sluggishly diffuses into the tortuous pores of the material and increases the resistance of the electrode (K.
Fic et al.
, 2.
Figure 7.
Electrochemical stable potential window of NAC3/MnO2 composite electrode was measured by Cycle Voltammetry in KI-added Na2SO4 electrolyte at 5 mVs-1 for various potential windows.
The NAC3/MnO2 composite electrode has improved the capacitive properties compared to other NAC composites, as indicated by the broadening of the CV curve in the KI-added Na2SO4 electrolyte, as shown in Figure 6.
The NAC3 composite electrode reached capacitance of 168 Fg-1, while 109 Fg-1 dan 120 Fg-1 for NAC1/MnO2 dan NAC2/MnO2 electrode, respectively.
Furthermore, the composite electrode has a stable electrochemical potential window at 0.
8 V.
Jurnal Dinamika Vokasional Teknik Mesin.
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09 No.
October 2024 | 118 Figure 7 shows the CV measurement of the NAC3/MnO2 composite electrode with a scan rate of up to 1.
2 V in KI-add Na2SO4 electrolyte.
The NAC3/MnO2 composite electrode exhibited a stable potential window reaching 1.
0 V.
According to the profile of the CV curve, the water reduction happened at 1.
2 V, as indicated by the raising of the cathodic current.
Theoretically, an aqueous electrolyte has a low voltage window due to water decomposition at 1.
23 V (S.
Pappu et al.
, 2.
The previous study reported that metal oxide-based pseudo-capacitors could enlarge the electrochemical potential window of aqueous electrolytes beyond 1.
0 V (P.
Haldar et al.
, 2.
CONCLUSION
In summary, the electrochemical properties of NAC/MnO2 composite electrodes have been studied in KI-added Na2SO4 electrolytes.
NAC3/MnO2 with the higher nitrogen content ratio exhibited the highest capacitance in Na2SO4 with or without KI additive.
Meanwhile, the KI has also enhanced the capacitance of NAC/MnO2 composite electrodes through pseudo-redox formation beyond the storage of the electrical double-layer capacitor.
The MnO2 effectively works as the host of pseudo-redox reactions when the KI additive is present in the Na2SO4 electrolyte.
The NAC3/MnO2 shows the highest capacitance of 168 Fg-1 at 5 mVs-1 in KIadded Na2SO4 electrolyte.
The additive also has improved energy and power densities of MnO2-modified electrodes, which are 22 Whkg-1 and 10 Wkg-1, respectively.
ACKNOWLEDGMENT