Open access peer-reviewed chapter

Application of Iron Oxide in Supercapacitor

Written By

Rajan Lakra, Rahul Kumar, Parasanta Kumar Sahoo, Sandeep Kumar and Ankur Soam

Submitted: 16 March 2022 Reviewed: 20 April 2022 Published: 17 June 2022

DOI: 10.5772/intechopen.105001

From the Edited Volume

Iron Oxide Nanoparticles

Edited by Xiao-Lan Huang

Chapter metrics overview

270 Chapter Downloads

View Full Metrics

Abstract

Iron oxide nanostructures have been considered very promising material as electrode in electrochemical energy storage devices because of their lower cost of synthesis and high theoretical charge storage capacity. Iron oxide nanoparticles and their nanocomposites have performed excellent in supercapacitor. Iron oxide as negative electrode has extended the working voltage window of a supercapacitor. The main problems associated with iron oxide based electrodes are their poor electrical conductivity and cycle stability. Therefore, a conductive carbon matrix has been added to the iron oxide based electrodes to improve the electrochemical performance. In this chapter, recent progress on iron oxide and its composite with different materials as electrode in supercapacitor is summarized. The various synergistic effects of nanocomposites and compositional engineering to enhance the electrochemical performance of iron oxide are also discussed.

Keywords

  • iron oxide
  • composite
  • electrodes
  • supercapacitor

1. Introduction

Serious environmental and climate problems have been arisen due to the continuous consumption and depletion of fossil fuels [1, 2, 3, 4]. This problem would be worst in the coming days as the demand of energy is going increased day by day. Consequently, there is a need of clean and sustainable energy resources such as solar cells and batteries. The solar cell always needs sun light to generate continuous electricity supply. This problem can be sort out by integrating an energy storage device to the solar cell. Batteries can be used for the above work however their replacement and maintenance are major issues [1, 3, 5, 6, 7]. Supercapacitors have drawn much attention in recent years to be used in several applications such as industrial power and energy management. Moreover, they are very efficient (fast charging/discharging and long life), low-cost and environmentally friendly [8, 9, 10, 11]. They have larger power density than batteries and capability to deliver the charge quickly [12, 13, 14, 15]. A supercapacitor is fabricated with two electrodes separated by a separator, and electrolyte (Figure 1). The electrode materials have decisive role in the charge storage capacity; therefore, different materials and their combinations have been used in supercapacitor [2, 16, 17, 18, 19]. Supercapacitor can store the energy via two process (1) formation of electric double layer (EDL) at the electrode/electrolyte interface [4, 19, 20] and (2) redox reactions (pseudocapacitor) [16, 21, 22] (Figure 2). Carbon and silicon based materials are generally used for EDL capacitor whereas pseudocapacitor consists of metal oxides and conducting polymers. A hybrid supercapacitor technology has also been developed by combining the properties of EDLC and pseudocapacitor [24, 25, 26, 27].

Figure 1.

Structure of (a) dielectric capacitor and (b) supercapacitor.

Figure 2.

(a) Ragone plot for different devices. (b) Schematic representation of charge storage at high surface area electrode. (c) Different models for EDL: Helmholtz model, Gouy–Chapman model and Gouy–Chapman–Stern model. Charge storage process via redox process (pseudocapacitor); (d) bulk redox and (e) surface redox. (Reprinted with permission from Ref. [23] Copyright (2020) American Chemical Society).

Carbon based electrodes can offer high power and long cycle stability. However, low energy density is major concern with carbon electrodes [28, 29]. In the past decade, major efforts have been made developing a hybrid supercapacitor in order to meet the demands of high energy and high power density [30, 31]. Nano-sized structure of metal oxides can offer higher surface area to the electrode for good electrode/electrolyte ions interaction and short ion-diffusion length. Among metals oxides, iron oxides (FeOx) are being considered efficient electrodes as they have low cost of synthesis, high theoretical capacitance due to variable oxidation states [32, 33, 34]. Various nanostructures of Fe based materials such as nanorods, nanosheets, nanotubes and nanoparticles, nanowires, nanoflowers etc. have been employed to increase the surface area and shorten the diffusion length of ions [2, 21, 32, 35]. The above structures have shown excellent performance in supercapacitor. However, low conductivity and poor structural stability are major issues with iron oxides, which need to be addressed. Incorporating conductive materials to iron oxides can lead to improve the conductivity and stability as well. Therefore, different forms of carbon and polymers have been mixed with iron oxide to fabricate a hybrid electrode and this electrode has shown excellent performance in supercapacitor. In this chapter, the achievements and progress made towards developing iron oxides (Fe2O3 and Fe3O4) based electrodes have been reviewed.

Advertisement

2. Supercapacitor

A supercapacitor or ultracapacitor is an advanced technology which has much larger capacitance than a normal capacitor. Supercapacitors can store the energy about 10 times more than dielectric capacitors and return the energy back faster than batteries. They occupy the place between dielectric capacitors and rechargeable batteries in Ragone plot (Figure 2a). The charge storage process in supercapacitor is completely different than that of conventional capacitor. In electrostatic capacitor, two conducting electrodes are separated by a dielectric material. The charge is stored by the polarization process in the dielectric material. In case of supercapacitor, an electrolyte is filled between two electrodes of high surface area. During charging, opposite charge starts accumulating on the surface of electrodes. As the charge is stored physically with no chemical change, it is highly reversible and it shows stable behavior for a large number of cycles. Capacitance (C) is defined as the ratio of stored charge (Q) to the applied voltage (V)

C=QVE1

C is directly proportional to the surface area (A) of each electrode and inversely proportional to the distance (d) between the electrodes

C=εAdE2

Where ε is the permittivity of the insulating material, A is the area of the electrode and d is the distance between the electrodes. The energy (E) of a capacitor is calculated by the following equation;

E=12CV2E3

Power (P) is the energy delivered by a device per unit time. The maximum power is limited by equivalent series resistance (ESR) with the following relation

P=V24ESRE4

An EDLC has two electrodes which are immersed in an electrolyte and separated by a separator. Its charge storage is non faradaic in nature, there is no transfer of charge between electrode and electrolyte. Electric charge is accumulated electrostatically on electrode/electrolyte interface which is responsible for the formation of EDL (Figure 2b). The charging and discharging processes are highly reversible and there is no chemically change in the electrodes. This leads to the increased in cycle life, compared to batteries but less than conventional capacitor.

Pseudo means false so, as the name indicates this type of materials do not store charge like a conventional capacitor that is by forming EDL but work like a capacitor. The charge storage mechanism of such type of capacitor is faradaic in nature or the electrode reacts with the electrolyte to store charge (Figure 2d and e). Transition metal oxide and polymer show such kind of behavior. A reversible redox processes take place in which the valence electrons of electro active materials are transferred across the electrode/electrolyte interface, resulting in a potential-dependent capacitance (Figure 2e). The term pseudo-capacitance is used to distinguish this mechanism of charge storage from double layer. So we can say that that pseudo capacitance possess battery-like behavior with faradic reactions between electrodes and electrolyte. Table 1 shows the difference between EDLC and pseudocapacitor.

EDL capacitorPseudocapacitor
It stores charge by non-faradaic mechanism.It stores charge by faradaic mechanism.
Capacitance is low as compared to pseudo capacitance.Capacitance is 10 times higher than EDLC.
Large cycle stabilityPoor cycle stability
The charging/discharging curve is highly reversibleReversible but not as compared to EDLC

Table 1.

Comparison between EDLC and pseudocapacitor.

Advertisement

3. Fe2O3 based electrodes

Fe2O3 electrode stores the charge via reversible oxidation/reduction reactions at the electrode and electrolyte interface. Low conductivity and poor cycling stability hamper its application in supercapacitor. Shivakumara et al. [36] have used porous α-Fe2O3 as electrode in supercapacitor. Porous α-Fe2O3 synthesized by sol–gel route offered BET surface area of 386 m2 g−1. α-Fe2O3 demonstrated specific capacitance of 300 F g−1 in 0.5 M Na2SO3 at a discharge rate of 1 A g−1. However, the electrode could retain only 73% of the initial capacitance after 1000 cycles.

Flower-like α-Fe2O3 nanostructures prepared by ethylene glycol mediated self-assembly process exhibited capacitance value of 127 F g−1 in 0.5 M Na2SO3 determined at a current density of 1 A g−1 [37]. Flower-like α-Fe2O3 has retained 80% of the initial capacitance after 1000 cycles. Despite of good value of capacitance, Fe2O3 does not meet the requirement of long cycle life. Change in volume during multiple cycles causes large degradation in the capacitance. Therefore, maximum efforts have been made towards shorting the diffusion length of electrolyte ions and minimizing the volume change by combining Fe2O3 with conducting materials.

Large efforts have been made to add a conductive phase to Fe2O3 electrodes to enhance overall capacitive performance. Abad et al. [38] have synthesized rGO-Fe2O3 nanocomposites by hydrothermal process for supercapacitor application. In the composite electrode, Fe2O3 nanoparticles have average size of 25 nm and are anchored on graphene sheets making good physical contact. The Fe2O3 nanoparticles prevent the restacking of rGO sheets which results in good accessibility of electrolyte ions to the electrode. rGO-Fe2O3 exhibited a specific capacitance of 291 F g−1 at 1 A g−1 in 1 M KOH aqueous solution. The performance was observed stable in the negative potential window of −1 to 0 V with three-electrode system. Fe2O3 worked well as negative electrode in asymmetric supercapacitor. A hybrid structure of porous Fe2O3 nanosheets on carbon fabric (CF-Fe2O3) was developed in order to overcome poor electrical conductivity and poor cycling stability of Fe2O3 [39]. Fe2O3 was deposited on CF via electrodeposition process. An asymmetric supercapacitor with CF-Fe2O3 as negative electrode and CF-Co3O4 as positive electrode was fabricated, which exhibited a good value of areal capacitance to be 842 mF cm−2. The asymmetric supercapacitor demonstrated maximum volumetric energy density of 6.75 mWh cm−3 and power density of 104 mW cm−3. The device retained 93% capacitance after 4000 cycles.

Jiang et al. [40] have synthesized Fe2O3/porous carbon nanocomposites (Fe2O3/HAC) by hydrothermal method. The porous carbon prevents the agglomeration of Fe2O3 nanoparticles and minimizes the ion diffusion path on the electrode surface, providing more flow channels for the ions. Fe2O3/HAC demonstrated larger capacitance of 156 F g−1 than that of individual components of HAC (145 F g−1) and Fe2O3 (90 F g−1). Redox peaks were observed in CV of both Fe2O3 and Fe2O3/HAC. The obtained CV consisted of a pair of oxidation peaks at −0.652 and −0.641 V and reduction peaks at −0.996 and −1.038 V, respectively. Fe2O3/HAC stores the charge via following mechanism;

FeOOH+H2O+eFeOH2+OH1E5
FeOH2+OH1FeOOH+H2O+eE6

A specific capacitance of 970 F g−1 was achieved from Fe2O3/rGO composite which was prepared by in situ synthesis and mechanical agitation methods [41]. This high value of capacitance is mainly due to the synergistic effect between Fe2O3 and rGO. rGO provides high electrical conductivity to the composite electrode and makes fast channels for the movement of charges. A degradation of 25% of capacitance was observed after 2000 cycles. A carbon shell layer has been coated on porous Fe2O3 nanowire arrays by hydrothermal route to improve the electrochemical properties of the electrode [42]. Fe2O3/C was used as the anode in solid state asymmetric supercapacitor with MnO2 as the cathode. A wide voltage of 2 V was achieved with this configuration. The fabricated device could give a maximum energy density of 30.625 Wh kg−1 and a maximum power density of 5000 W kg−1. The device exhibited good stability about 82% retention of capacitance after 10,000 cycles. A α-Fe2O3/MnOx and α-Fe2O3/C core-shell nanostructures were developed to design an asymmetric supercapacitor [43]. In the hybrid electrode, fast reversible redox-reactions occur on MnOx and α-Fe2O3 NR core facilitates electron transfer between shell and the current collector. Similarly, α-Fe2O3/C core-shell works as negative electrode. The asymmetric device fabricated with α-Fe2O3/C//α-Fe2O3/MnOx core-shell exhibited specific capacitance of 1.28 F cm−3 at a scan rate of 10 mV s−1 with voltage window of 0–2 V. The supercapacitor was able to retain 78% capacitance at the scan rate of 400 mVs−1 with a maximum energy-density of ∼0.64 mWh cm−3 and a maximum power-density of 155 mW cm−3. Zhang et al. [44] have developed Fe2O3@NiO nanorods on flexible carbon cloth by hydrothermal method. A specific capacitance of 800 mF cm−2 at 10 mA cm−2 was obtained with Fe2O3@NiO/CC electrode. Remarkable long cycle stability (96.8% capacitance retention after 16,000 cycles) was demonstrated by the electrode. This outstanding performance from Fe2O3@NiO/CC is due to the good electrical contact of active material with flexible carbon.

α-Fe2O3 has shown good electrochemical performance with graphitic (g-C3N4) carbon nitride [45]. The as-prepared g-C3N4/α-Fe2O3 composites with large specific surface area exhibited specific capacitance of 580 F g−1 determined at 1.0 A g−1 in 1M KOH. The Fe2O3 nanoparticles accommodate the space between the layers of g-C3N4 avoiding restacking and increasing the probability of interaction between Fe2O3 and electrolyte. Zhong et al. [46] have fabricated a heterostructure of Fe2O3 nanospheres anchored on FeS2 nanosheets by one-step hydrothermal approach for supercapacitor. The FeS2@Fe2O3 hybrid electrode demonstrated a specific capacitance of 255 F g−1 as well as good cycle stability, 90% capacitance retention after 5000 cycles. The excellent long cycle life could be ascribed to hybrid structure which can facilitate fast transportation of the electrolyte ions. A hybrid electrode of PEDOT coated onto Ti-doped Fe2O3 showed a remarkable capacitive performance [47]. A high value of areal capacitance of 1.15 F cm−2 at 1 mA cm−2 has been achieved with this strategy. Ti-Fe2O3@PEDOT demonstrated extraordinary cyclic stability of 96% retention in capacitance after 30,000 cycles, which is better than that of Ti-Fe2O3 (80.7%) and Fe2O3 (81.8%) electrodes. Ti-doping in the electrode enhances electrical conductivity and better utilization of Fe2O3. PEDOT has two important roles here, working as protective layer for Fe2O3 and relaxing the transfer of electrons.

A high specific capacitance of 1124 F g−1 has been achieved form a ternary composite of polyaniline/Fe2O3 decorated graphene coated on carbon cloth (Figures 3 and 4) at a current of 0.25 A g−1 in 1 M H2SO4 [48]. This large value of specific capacitance is due to the synergistic effects of individual component in the electrode. Graphene contributes as EDL capacitance and Fe2O3 and polyaniline as pseudocapacitance to the overall capacitance of hybrid electrode. In-situ polymerization of polyaniline also leads to improve the surface area of electrodes. Le et al. [50] have fabricated a hybrid electrode of polypyrrole-coated Fe2O3 nanotubes (Fe2O3@PPy) for high-performance electrode for aqueous asymmetric supercapacitor. A thin layer of polypyrrole was coated on Fe2O3 nanotubes by an in situ chemical oxidative polymerization method. Fe2O3@PPy could deliver a capacitance of 530 mF cm−2 at 1 mA cm−2. There is synergistic effect between PPy and Fe2O3, the shell of conducting PPy makes an ease transportation for charge carriers and improves stability of Fe2O3 nanotubes while charging/discharging process. The fabricated asymmetric supercapacitor with Fe2O3@PPy and MnO2 nanotubes could deliver energy density of 51.2 Wh kg−1 at a power density of 285.4 W kg−1 operated at high voltage of 2.0 V. 83.5% capacitance retention was observed over 5000 cycles with the asymmetric supercapacitor.

Figure 3.

Schematic illustration of synthesis process of (a) Fe2O3 decorated graphene and (b) ternary Polyaniline/Graphene/Fe2O3 (PGF) composite on carbon cloth. (Reprinted with permission from Ref. [48]. Copyright (2020) American Chemical Society).

Figure 4.

Electrochemical behavior of the GF-CNT@Fe2O3//GF-CoMoO4 supercapacitor. (a) Full-cell structure. (b) CV curves, (c) rate capability, (d) cycling life, (e) Ragone plot of the asymmetric supercapacitor. Digital photos of the single electrode and full cell are depicted in insets of (c). (Reprinted with permission from Ref. [49]. Copyright (2015) American Chemical Society).

Guan et al. [49] have developed an ultrahigh-energy and long-life supercapacitor anode material by coating a thin layer of Fe2O3 on graphite foam-carbon nanotube framework GF-CNT@Fe2O3. GF-CNT@Fe2O3 as anode was also integrated into a full supercapacitor cell with GF-CoMoO4 as cathode. A high energy density of ∼74.7 Wh kg−1 with power density of∼1400 W kg−1 has been obtained from the full device. The device also exhibited exceptional cycle stability, retention of about 95.4% capacitance after 50,000 cycles. These values make it a promising candidate for high performance supercapacitor. Improvement in the electrochemical performance of Fe2O3 based electrode may also be possible by introducing nitrogen in the electrode. In this regard, Zhao et al. [51] have synthesized nitrogen-doped graphene and Fe2O3 composites (NGFeCs) by hydrothermal method. NGFeCs exhibited improved electrochemical performance than GFeCs. The specific capacitance of NGFeCs electrode was determined to be 260.1 F g−1 (150.4 Fg−1 for GFeCs electrode) with current density of 2 A g−1. In addition to above, 82.5% retention in capacitance was observed after 1000 cycles. The improvement in the performance is due to the good electronic conductivity and increased active sites.

Self-assembled α-Fe2O3 mesocrystals/graphene nanohybrids demonstrated a good value of specific capacitance of 306.9 F g−1 at 3 A g−1 in an aqueous electrolyte and in voltage window of 1 V [33]. Porous structure of α-Fe2O3 mesocrystals/graphene nanohybrids with high electrical conductivity can provide fast transportation for electrolyte ions even at high discharge current densities. 2D α-Fe2O3/rGO nanocomposites fabricated by one-pot solvothermal approach exhibited specific capacitance value to be 903 F g−1 calculated at a current density of 1 A g−1 [52]. This value of capacitance was observed superior than α-Fe2O3 nanoplates. In the hybrid composite, α-Fe2O3 nanoplates were encapsulated in rGO nanosheets to form a porous structure. The α-Fe2O3/rGO nanocomposites with high electrical conductivity and 2D nanostructure promote the charge transportation between electrode and electrolyte, hence enhancing the electrochemical performance of the electrode.

Advertisement

4. Fe3O4 based electrodes

Transition metal oxides (RuO2, MnO2, NiO, Fe2O3, Co3O4, etc.) have been used as electrode materials for supercapacitor application because they use rapid reversible redox reactions at the surface of active materials to offer high power density [9, 31, 53, 54, 55, 56, 57, 58]. Amongst the metal oxides, Fe3O4 is a better alternative electrode material for supercapacitor because of its low cost, natural abundance, environmental friendliness, high theoretical specific capacitance (2299 F g−1), large potential window and different valence states [59, 60, 61]. It has been seen in literature that Fe3O4 with various dimensions and morphology shows high value of specific capacitance [62].

The charge storage mechanism of Fe3O4 was investigated in various aqueous electrolytes such as sodium chloride, potassium hydroxide, sodium sulphate, sodium sulphite and sodium phosphate. Fe3O4 in the Na2SO3 electrolyte demonstrated a higher capacitance of 510 F g−1 with an operating potential of 1.2 V and this value was greater than those of other electrolytes [63]. Two pseudocapacitive mechanisms were purposed for Fe3O4 in the Na2SO3 electrolyte, which are given below

FeO+SO32FeSO4+2eE7
2FeIIO+SO32FeIIIO+SO32FeIIIO+2eE8

Eq. (7) represents the surface redox reaction of sulphur in the form of sulphate and sulphite anions while Eq. (8) represents the oxidation/reduction reaction between Fe(II) and Fe(III). It was observed that due to the addition of both the EDLC and pseudocapacitor, the capacitance of Fe3O4 in the Na2SO3 electrolyte rises and involves the reduction/oxidation of specially adsorbed sulphite anions as given by the following equations [63].

2SO32+3H2O+4eS2O32+6OHE9
S2O32+3H2O+8e2S2+6OHE10

Many methods have been used to fabricate the Fe3O4 materials for supercapacitor application such as hydrothermal method [64, 65, 66, 67], Electroplating [63], sol-gel method [68], Chemical precipitation method [69], Hydrolysis and annealing process [70], solvothermal method [71], Electrospinning [72], Aerosol method [73]. Reports on different synthesis processes of Fe3O4 based electrodes and their specific capacitance values are given in Table 2.

ElectrodeSynthesis processElectrolyteCapacitanceRef.
Fe2O3/porous carbonHydrothermal6 M KOH256 F g−1 at 1 A g−1[40]
FeS2 nanosheet@Fe2O3 nanosphereHydrothermal1 M Li2SO4255 F g−1 at 1 A g−1[46]
α-Fe2O3 nanostructuresSol–gel route0.5 M Na2SO3300 F g−1 at 1 A g−1[36]
Polyaniline/graphene/Fe2O3 composites hydrogelMicrowave irradiation and in-situ polymerization1 M H2SO41124 F g−1 at 0.25 A g−1[48]
α-Fe2O3/rGOOne-pot solvothermal approach1 M KOH903 F g−1 at 1 A g−1[52]
Polypyrrole-coated Fe2O3 nanotubesIn situ chemical oxidative polymerization method1 M Na2SO4530 mF cm−2 at 1 mA cm−2[50]
Porous-Fe2O3@C nanowireHydrothermal route1 M Na2SO4280 F g−1 at 1 Ag−1 and 241.3 mF cm−2 at 1 mA cm−2[42]
α-Fe2O3/rGO compositesIn situ synthesis and mechanical agitation methods6 M KOH970 F g−1 at 1 A g−1[41]
Porous flowerlikeα-Fe2O3Ethylene glycol mediated self-assembly process0.5 M Na2SO3127 F g−1 at 1 A g−1[37]
Core-branch Fe2O3@NiO nanorodsHydrothermal method3 M KOH800 mF cm−2 at 10 mA cm−2[44]

Table 2.

Electrochemical capacitance of some Fe2O3 based electrodes.

Fe3O4@carbon nanosheet composite synthesized using ammonium ferric citrate precursor and graphene oxide as the structure-directing agent under a hydrothermal process was used as electrode in supercapacitor [59]. Fe3O4@carbon nanosheet composite exhibited a specific capacitance of 586 F g−1 at 0.5 A g−1 in KOH/PVA gel electrolyte. This composite showed excellent energy density of 18.3 Wh kg−1 and power density of 351 W kg−1.

Wang et al. [60] developed a simple route to fabricate the hybrid electrode of Fe3O4-doped porous carbon nanorods (Fe3O4-DCN) supported by three dimensional (3D) kenaf stem-derived macroporous carbon (KSPC) for supercapacitor. The 3D-KSPC/Fe3O4-DCN showed excellent specific capacitance of 285.4 F g−1 at the current density of 1 A g−1 and excellent cyclic stability in 2.0 M KOH electrolyte (Figure 5). Kumar et al. [61] prepared a hybrid electrode of 3D rGO NSs containing Fe3O4 NPs using one-pot microwave approach. The experimental studies showed that the as-synthesized Fe3O4/rGO hybrids were made of faceted Fe3O4 NPs with interconnected network of rGO NSs. The schematic formation mechanism is shown in Figure 6. This material as electrode in supercapacitor exhibited a specific capacitance of 455 F g−1 at the scan rate of 8 mV s−1.

Figure 5.

(a) Schematic illustration of the formation process of carbon nanosheet embedded Fe3O4. (Reprinted with permission from Ref. [59]. Copyright (2016) American Chemical Society.) (b) Schematic illustration of the formation process of 3D-KSPC/Fe3O4-DCN nanocomposites. (Reprinted with permission from Ref. [60]. Copyright (2016) American Chemical Society).

Figure 6.

Schematic formation mechanism of 3D Fe3O4/rGO hybrids. (Reprinted with permission from Ref. [61]. Copyright (2017) American Chemical Society).

Chen et al. [74] fabricated a Fe3O4 film with regularly edge-affected cubic morphology on stainless foil using hydrothermal method and this film was used as electrode for supercapacitor. This film exhibited a specific capacitance of 118.2 F g−1 at the current of 6 mA in Na2SO3 electrolyte and good cycle stability about 88.75% capacitance retention after 500 cycles. Wang et al. [63] prepared the Fe3O4 film by an electroplating method to be used in supercapacitor as electrode. Fe3O4 film demonstrated a specific capacitance of 170 F g−1 in 1 M Na2SO3 electrolyte. Fe3O4 nanoparticles synthesized by sol gel method exhibited a specific capacitance of 185 F g−1 at the current of 1 mA in 3 M KOH electrolyte [68]. Brousse et al. [69] prepared Fe3O4 by chemical precipitation, which demonstrated a specific capacitance of 75 F g−1 in aqueous electrolyte of 0.1 M K2SO4. Liu et al. [64] synthesized Fe3O4 nanorods and carbon coated Fe3O4 nanorods via hydrothermal reaction and subsequent sintering procedure. Fe3O4 nanorods showed a specific capacitance of 208.6 F g−1 while carbon coated Fe3O4 nanorods exhibited a specific capacitance of 275.9 F g−1 at a current density of 0.5 A g−1 in 1 M Na2SO3 aqueous solution.

Guan et al. [65] synthesized carbon nanotube/Fe3O4 (CNT/Fe3O4) nanocomposite by an easy and efficient hydrothermal method. CNT/Fe3O4 nanocomposite showed enhanced specific capacitances of 117.2 F g−1 (which is three times than that of pure Fe3O4) at current density of 10 mA cm−2 in 6 M KOH electrolyte. It also exhibited superior cyclic stability and energy density of 16.2 Wh kg−1. Lin et al. [66] synthesized Fe3O4/GO by using hydrothermal method, which showed a specific capacitance of 661 F g−1 at current density of 1 A g−1 in 1 M KOH electrolyte. Qi et al. [70] prepared the Fe3O4/rGO composites using hydrolysis route and subsequent annealing process for supercapacitor application. The Fe3O4/rGO composite showed specific capacitance of 350.6 F g−1 at 1 mV s−1 in 6 M KOH electrolyte (Table 3).

ElectrodeMethodElectrolyteSpecific capacitanceReference
Fe3O4 thin filmElectroplating1 M Na2SO3170 F g−1[63]
Fe3O4 nanoparticlesSol–gel3 M KOH185 F g−1[68]
Fe3O4Chemical precipitation method0.1 M K2SO475 F g−1[69]
Fe3O4 nanorodsHydrothermal1 M Na2SO3208.6 F g−1[64]
Fe3O4/grapheneHydrothermal1 M KOH661 F g−1[66]
Fe3O4/reduced graphene oxideHydrolysis and annealing process6 M KOH350.6 F g−1[70]
Fe3O4/reduced graphene oxideSolvothermal process1 M KOH480 F g−1[75]
Fe3O4–carbon nanosheetsHydrothermal and heat treatment1 M Na2SO3163.4 F g−1[67]
Fe3O4 doped double-shelled hollow carbon spheresAerosol, spray and in-situ polymerization methods6 M KOH1153 F g−1[76]

Table 3.

Capacitance of Fe3O4 based electrodes synthesized by different process.

It is seen that iron oxides have demonstrated excellent performance in supercapacitor and asymmetric supercapacitor as well [71, 72, 73, 77, 78, 79]. Shi et al. [75] prepared the nanocomposites of Fe3O4 NPs connected to rGO sheets by using a solvothermal process. Fe3O4/rGO nanocomposites were utilized to prepare thin film supercapacitor electrodes by using a spray deposition technique without the addition of insulating binders. It was observed that the Fe3O4/rGO nanocomposite exhibited higher specific capacitance, 480 F g−1 at a discharge current density of 5 A g−1, which is larger than that of pure rGO or pure Fe3O4 NPs. Fe3O4/rGO nanocomposite exhibited energy density of 67 W h kg−1 and power density of 5506 W kg−1. Ultrathin nanoporous Fe3O4–carbon nanosheets synthesized by hydrothermal method demonstrated a specific capacitance of 163.4 F g−1 in 1 M Na2SO3 electrolyte [67].

Mu et al. [80] synthesized Fe3O4 nanosheets on one-dimensional (1D) carbon nanofibers (CNFs) using the electrospinning technique and solvent-thermal process. The Fe3O4/CNFs nanocomposite exhibited a specific capacitance of 135 F g−1 in 1 M Na2SO3 electrolyte. The high capacitance may be due to the improved electrical conductivity of the composite by adding the CNFs in Fe3O4. Li et al. [76] prepared the double-shelled hollow carbon spheres with conductive graphite structure and Fe3O4 species (C-C-Fe3O4) using aerosol, spray, and in-situ polymerization methods. The C-C-Fe3O4 showed remarkable value of specific capacitance to be 1153 F g−1 at current density of 2 A g−1. C-C-Fe3O4 also demonstrated good rate capability, 514 F g−1 at 100 A g−1. The electrode exhibited only 3.3% degradation in the capacitance after 8000 cycles. Energy density of 17–45 W h kg−1 and powder density of 400–8000 W kg−1 were achieved from the C-C-Fe3O4 electrode.

Advertisement

5. Conclusion

Recent progress on supercapacitor is to increase its specific capacitance, rate capability, cycle life and operating voltage by developing low cost and eco-friendly electrode materials. In this regard, iron oxide may be a suitable candidate with higher value of capacitance as negative electrode for asymmetric supercapacitor to be operated at wide voltage window. Therefore, a lot of work has been carried out on iron oxide based electrode for supercapacitor application. The electrochemical performance of iron oxide based electrodes has been reviewed and discussed in this chapter. It is observed that the synthesis process and morphology of iron oxide play important role in supercapacitor performance. Efforts have been made towards preparing a composite of iron oxide with high conductive materials in order to overcome its poor electrical conductivity. Nanostructure of iron oxide such as nanoparticles could enhance the active sites for electrochemical reactions. Iron oxide nanostructure with carbon can further increase the specific capacitance and energy density of supercapacitor. Synthesis of iron oxide nanoparticles/graphene nanocomposite seems to be more effective approach for high performance supercapacitor.

Advertisement

Conflict of interest

The authors declare no conflict of interest.

References

  1. 1. Kim T, Song W, Son DY, Ono LK, Qi Y. Lithium-ion batteries: Outlook on present, future, and hybridized technologies. Journal of Materials Chemistry A. 2019;7(7):2942-2964. DOI: 10.1039/C8TA10513H
  2. 2. Lv L et al. Progress in iron oxides based nanostructures for applications in energy storage. Nanoscale Research Letters. 2021;16(1). DOI: 10.1186/s11671-021-03594-z
  3. 3. Nitta N, Wu F, Lee JT, Yushin G. Li-ion battery materials: Present and future. Materials Today. 2015;18(5):252-264. DOI: 10.1016/j.mattod.2014.10.040
  4. 4. Lakra R, Kumar R, Sahoo PK, Thatoi D, Soam A. A mini-review: Graphene based composites for supercapacitor application. Inorganic Chemistry Communications. 2021;133. DOI: 10.1016/j.inoche.2021.108929
  5. 5. Zhao D, Wang Y, Zhang Y. High-performance Li-ion batteries and super-capacitors base on 1-D nanomaterials in prospect. 2011;3(1). DOI: 10.1007/BF03353653
  6. 6. Kim H-J, Krishna TNV, Zeb K, Rajangam V, Gopi CVV, Sambasivam S, et al. A comprehensive review of Li-ion battery materials and their recycling techniques. Electronics. 2020;9(7):1161. DOI: 10.3390/electronics9071161
  7. 7. Kuperman A, Aharon I. Battery – Ultracapacitor hybrids for pulsed current loads: A review. Renewable and Sustainable Energy Reviews. 2011;15(2):981-992. DOI: 10.1016/j.rser.2010.11.010
  8. 8. Kumar R, Soam A, Sahajwalla V. Sucrose-derived carbon-coated nickel oxide (SDCC-NiO) as an electrode material for supercapacitor applications. Materials Advances. 2020;1(4):609-616. DOI: 10.1039/d0ma00323a
  9. 9. Kumar R, Soam A, Hussain R, Mansuri I, Sahajwalla V. Carbon coated iron oxide (CC-IO) as high performance electrode material for supercapacitor applications. Journal of Energy Storage. 2020;32(August):101737. DOI: 10.1016/j.est.2020.101737
  10. 10. Kumar R, Singh M, Soam A. Study on electrochemical properties of silicon micro particles as electrode for supercapacitor application. Surfaces and Interfaces. 2020;19. DOI: 10.1016/j.surfin.2020.100524
  11. 11. Soam A, Kumar R, Thatoi D, Singh M. Electrochemical performance and working voltage optimization of nickel ferrite/graphene composite based supercapacitor. Journal of Inorganic and Organometallic Polymers and Materials. 2020;30(9):3325-3331. DOI: 10.1007/s10904-020-01540-7
  12. 12. Soam A, Kavle P, Kumbhar A, Dusane RO. Performance enhancement of micro-supercapacitor by coating of graphene on silicon nanowires at room temperature. Current Applied Physics. 2017;17(2). DOI: 10.1016/j.cap.2016.11.011
  13. 13. Kumagai S, Mukaiyachi K, Tashima D. Rate and cycle performances of supercapacitors with different electrode thickness using non-aqueous electrolyte. Journal of Energy Storage. 2015;3:10-17. DOI: 10.1016/j.est.2015.08.002
  14. 14. Zhi M, Xiang C, Li J, Li M, Wu N. Nanostructured carbon-metal oxide composite electrodes for supercapacitors: A review. Nanoscale. 2013;5(1):72-88. DOI: 10.1039/c2nr32040a
  15. 15. Soam A, Mahender C, Kumar R, Singh M. Power performance of BFO-graphene composite electrodes based supercapacitor. Materials Research Express. 2019;6(2). DOI: 10.1088/2053-1591/aaf125
  16. 16. Iro ZS, Subramani C, Dash SS. A brief review on electrode materials for supercapacitor. International Journal of Electrochemical Science. 2016;11(12):10628-10643. DOI: 10.20964/2016.12.50
  17. 17. Ke Q, Wang J. Graphene-based materials for supercapacitor electrodes – A review. Journal of Materials. 2016;2(1):37-54. DOI: 10.1016/j.jmat.2016.01.001
  18. 18. Li Y, Wang H, Mousavi F, Kaner RB. Graphene-based materials for flexible supercapacitors. Chemical Society Reviews. 2015;44:3639-3665. DOI: 10.1039/C4CS00316K
  19. 19. Soam A, Arya N, Singh A, Dusane R. Fabrication of silicon nanowires based on-chip micro-supercapacitor. Chemical Physics Letters. 2017;678. DOI: 10.1016/j.cplett.2017.04.019
  20. 20. Zhai Y, Dou Y, Zhao D, Fulvio PF, Mayes RT. Carbon Materials for Chemical Capacitive Energy Storage2011. pp. 4828-4850. DOI: 10.1002/adma.201100984
  21. 21. Nithya VD, Arul NS. Review on α-Fe2O3 based negative electrode for high performance supercapacitors. Journal of Power Sources. 2016;327:297-318. DOI: 10.1016/j.jpowsour.2016.07.033
  22. 22. Gogotsi Y, Penner RM. Energy storage in nanomaterials – Capacitive, pseudocapacitive, or battery-like? ACS Nano. 2018;12(3):2081-2083. DOI: 10.1021/acsnano.8b01914
  23. 23. Balasubramaniam S, Mohanty A, Balasingam SK, Kim SJ, Ramadoss A. Comprehensive insight into the mechanism, material selection and performance evaluation of supercapatteries. Nano-Micro Letters. 12, 2020;(1):1-46. DOI: 10.1007/s40820-020-0413-7
  24. 24. H. M. N. Graphene, et al., “High-energy MnO2 nanowire/graphene and graphene asymmetric electrochemical capacitors,” vol. 4, no. 10, pp. 5835–5842, 2010. doi: 10.1021/nn101754k
  25. 25. Sankar KV, Selvan RK. The ternary MnFe2O4/graphene/polyaniline hybrid composite as negative electrode for supercapacitors. Journal of Power Sources. 2015;275:399-407. DOI: 10.1016/j.jpowsour.2014.10.183
  26. 26. Kalpana D, Omkumar KS, Kumar SS, Renganathan NG. A novel high power symmetric ZnO/carbon aerogel composite electrode for electrochemical supercapacitor. 2006;52:1309-1315. DOI: 10.1016/j.electacta.2006.07.032
  27. 27. Mao L, Zhang K, On Chan HS, Wu J. Nanostructured MnO2/graphene composites for supercapacitor electrodes: The effect of morphology, crystallinity and composition. Journal of Materials Chemistry. 2012;22(5):1845-1851. DOI: 10.1039/c1jm14503g
  28. 28. Pu B et al. Flexible supercapacitors based on carbon nanomaterials. Journal of Materials Chemistry A. Materials for Energy and Sustainability. 2014;3(1):22507-22541. DOI: 10.1016/j.mattod.2015.01.002
  29. 29. Wang X, Dan W, Song X, Wei D, Zhao X, Zhang D. Review on carbon/polyaniline hybrids: Design and synthesis for supercapacitor. Molecules. 2019;24(12):2263. DOI: 10.3390/molecules24122263
  30. 30. Choudhary N et al. Asymmetric supercapacitor electrodes and devices. Advanced Materials. 2017;29(21). DOI: 10.1002/adma.201605336
  31. 31. Jeong GH, Baek S, Lee S, Kim SW. Metal oxide/graphene composites for supercapacitive electrode materials. Chemistry—An Asian Journal. 2016;11(7):949-964. DOI: 10.1002/asia.201501072
  32. 32. Zeng Y, Yu M, Meng Y, Fang P, Lu X, Tong Y. Iron-based supercapacitor electrodes: Advances and challenges. Advanced Energy Materials. 2016;6(24):1-17. DOI: 10.1002/aenm.201601053
  33. 33. Yang S, Song X, Zhang P, Sun J, Gao L. Self-assembled α-Fe2O3 mesocrystals/graphene nanohybrid for enhanced electrochemical capacitors. Small. 2014;10(11):2270-2279. DOI: 10.1002/smll.201303922
  34. 34. Li J, Chen D, Wu Q. α-Fe2O3 based carbon composite as pure negative electrode for application as supercapacitor. European Journal of Inorganic Chemistry. 2019;2019(10):1301-1312. DOI: 10.1002/ejic.201900015
  35. 35. Lorkit P, Panapoy M, Ksapabutr B. Iron oxide-based supercapacitor from ferratrane precursor via sol-gel-hydrothermal process. Energy Procedia. 2014;56(C):466-473. DOI: 10.1016/j.egypro.2014.07.180
  36. 36. Shivakumara S, Penki TR, Munichandraiah N. High specific surface area α-Fe2O3 nanostructures as high performance electrode material for supercapacitors. Materials Letters. 2014;131:100-103. DOI: 10.1016/j.matlet.2014.05.160
  37. 37. Shivakumara S, Penki TR, Munichandraiah N. Synthesis and characterization of porous flowerlike? Fe2O3 nanostructures for supercapacitor application. ECS Electrochemistry Letters. 2013;2(7):2013-2015. DOI: 10.1149/2.002307eel
  38. 38. Abad ZAK, Nemati A, Khachatourian AM, Golmohammad M. Synthesis and characterization of rGO/Fe2O nanocomposite as an efficient supercapacitor electrode material. Journal of Materials Science: Materials in Electronics. 2020;31(17):14998-15005. DOI: 10.1007/s10854-020-04062-7
  39. 39. Li T et al. Facile electrochemical fabrication of porous Fe2O3 nanosheets for flexible asymmetric supercapacitors. Journal of Physical Chemistry C. 2017;121(35):18982-18991. DOI: 10.1021/acs.jpcc.7b04330
  40. 40. Jiang X, Shi G, Wang G, Mishra P, Du J, Zhang Y. Fe2O3/hemp straw-based porous carbon composite for supercapacitor electrode materials. Ionics (Kiel). 2020;26(8):4039-4051. DOI: 10.1007/s11581-020-03547-z
  41. 41. Chen L, Liu D, Yang P. Preparation of α-Fe2O3/rGO composites toward supercapacitor applications. RSC Advances. 2019;9(23):12793-12800. DOI: 10.1039/c9ra01928f
  42. 42. Dong Y, Xing L, Chen K, Wu X. Porous α-Fe2O3@C nanowire arrays as flexible supercapacitors electrode materials with excellent electrochemical performances. Nanomaterials. 2018;8(7):1-10. DOI: 10.3390/nano8070487
  43. 43. Sarkar D, Pal S, Mandal S, Shukla A, Sarma DD. α-Fe2O3-based core-shell-nanorod–structured positiveand negative electrodes for a high-performance α-Fe2O3/C//α-Fe2O3/MnO x asymmetric supercapacitor. Journal of the Electrochemical Society. 2017;164(12):A2707-A2715. DOI: 10.1149/2.1711712jes
  44. 44. Zhang M, Li X, Wang X, Li D, Zhao N. Three-dimensional core-branch α-Fe2O3@NiO/carbon cloth heterostructured electrodes for flexible supercapacitors. Frontiers in Chemistry. 2020;7(January):1-10. DOI: 10.3389/fchem.2019.00887
  45. 45. Liu L, Wang J, Wang C, Wang G. Facile synthesis of graphitic carbon nitride/nanostructured α-Fe2O3 composites and their excellent electrochemical performance for supercapacitor and enzyme-free glucose detection applications. Applied Surface Science. 2016;390:303-310. DOI: 10.1016/j.apsusc.2016.08.093
  46. 46. Zhong Y, Liu J, Lu Z, Xia H. Hierarchical FeS2 nanosheet@Fe2O3 nanosphere heterostructure as promising electrode material for supercapacitors. Materials Letters. 2016;166:223-226. DOI: 10.1016/j.matlet.2015.12.092
  47. 47. Zeng YX et al. Advanced Ti-doped Fe2O3@PEDOT core/shell anode for high-energy asymmetric supercapacitors. Advanced Energy Materials. 2015;5(12):1-7. DOI: 10.1002/aenm.201402176
  48. 48. Gupta A et al. Nanostructured polyaniline/graphene/Fe2O3 composites hydrogel as a high-performance flexible supercapacitor electrode material. ACS Applied Energy Materials. 2020;3(7):6434-6446. DOI: 10.1021/acsaem.0c00684
  49. 49. Guan C et al. Iron oxide-decorated carbon for supercapacitor anodes with ultrahigh energy density and outstanding cycling stability. ACS Nano. 2015;9(5):5198-5207. DOI: 10.1021/acsnano.5b00582
  50. 50. Le K et al. Polypyrrole-coated Fe2O3 nanotubes constructed from nanoneedles as high-performance anodes for aqueous asymmetric supercapacitors. Dalton Transactions. 2020;49(28):9701-9709. DOI: 10.1039/d0dt01242d
  51. 51. Zhao P et al. Facile hydrothermal fabrication of nitrogen-doped graphene/Fe2O3 composites as high performance electrode materials for supercapacitor. Journal of Alloys and Compounds. 2014;604:87-93. DOI: 10.1016/j.jallcom.2014.03.106
  52. 52. Quan H, Cheng B, Xiao Y, Lei S. One-pot synthesis of α-Fe2O3 nanoplates-reduced graphene oxide composites for supercapacitor application. Chemical Engineering Journal. 2016;286:165-173. DOI: 10.1016/j.cej.2015.10.068
  53. 53. Raza W, Ali F, Raza N, Luo Y, Kim K, Yang J. Recent advancements in supercapacitor technology nano energy recent advancements in supercapacitor technology. Nano Energy. 2018;52(August):441-473. DOI: 10.1016/j.nanoen.2018.08.013
  54. 54. Abdel Maksoud MIA, Fahim RA, Shalan AE, Elkodous MA, Olojede SO, Osman AI, et al. Advanced materials and technologies for supercapacitors used in energy conversion and storage: A review. Environmental Chemistry Letters. 2021;19(1):375-439. DOI: 10.1007/s10311-020-01075-w
  55. 55. Zhi M, Xiang C, Li J, Li M, Wu N. Nanostructured carbon–metal oxide composite electrodes for supercapacitors: A review. 2013:72-88. DOI: 10.1039/c2nr32040a
  56. 56. Amirul M, Mohd A, Hawa N, Azman N, Kulandaivalu S, Sulaiman Y. Review of the use of transition-metal-oxide and conducting polymer-based fibres for high-performance supercapacitors. Materials and Design. 2020;186:108199. DOI: 10.1016/j.matdes.2019.108199
  57. 57. Huang M, Li F, Dong F, Zhang YX, Zhang LL. MnO2-based nanostructures for high-performance supercapacitors. Journal of Materials Chemistry A. 2015;3(43):21380-21423. DOI: 10.1039/c5ta05523g
  58. 58. Nithya VD, Sabari Arul N. Progress and development of Fe3O4 electrodes for supercapacitors. Journal of Materials Chemistry A. 2016;4(28):10767-10778. DOI: 10.1039/c6ta02582j
  59. 59. Fan H, Niu R, Duan J, Liu W, Shen W. Fe3O4@carbon nanosheets for all-solid-state supercapacitor electrodes. ACS Applied Materials & Interfaces. 2016;8(30):19475-19483. DOI: 10.1021/acsami.6b05415
  60. 60. Wang L et al. Three-dimensional macroporous carbon/Fe3O4-doped porous carbon nanorods for high-performance supercapacitor. ACS Sustainable Chemistry & Engineering. 2016;4(3):1531-1537. DOI: 10.1021/acssuschemeng.5b01474
  61. 61. Kumar R, Singh RK, Vaz AR, Savu R, Moshkalev SA. Self-assembled and one-step synthesis of interconnected 3D network of Fe3O4/reduced graphene oxide nanosheets hybrid for high-performance supercapacitor electrode. ACS Applied Materials & Interfaces. 2017;9(10):8880-8890. DOI: 10.1021/acsami.6b14704
  62. 62. Wu NL, Wang SY, Han CY, Wu DS, Shiue LR. Electrochemical capacitor of magnetite in aqueous electrolytes. Journal of Power Sources. 2003;113(1):173-178. DOI: 10.1016/S0378-7753(02)00482-2
  63. 63. Wang S-Y, Ho K-C, Kuo S-L, Wu N-L. Investigation on capacitance mechanisms of Fe3O4 electrochemical capacitors. Journal of the Electrochemical Society. 2006;153(1):A75. DOI: 10.1149/1.2131820
  64. 64. Liu J, Liu S, Zhuang S, Wang X, Tu F. Synthesis of carbon-coated Fe3O4 nanorods as electrode material for supercapacitor. Ionics (Kiel). 2013;19(9):1255-1261. DOI: 10.1007/s11581-013-0857-6
  65. 65. Guan D et al. Hydrothermal synthesis of carbon nanotube/cubic Fe3O4 nanocomposite for enhanced performance supercapacitor electrode material. Materials Science & Engineering, B: Solid-State Materials for Advanced Technology. 2013;178(10):736-743. DOI: 10.1016/j.mseb.2013.03.010
  66. 66. Lin TW, Dai CS, Hung KC. High energy density asymmetric supercapacitor based on NiOOH/Ni3S2/3D graphene and Fe3O4/graphene composite electrodes. Scientific Reports. 2014;4:1-10. DOI: 10.1038/srep07274
  67. 67. Liu D et al. Ultrathin nanoporous Fe3O4-carbon nanosheets with enhanced supercapacitor performance. Journal of Materials Chemistry A. 2013;1(6):1952-1955. DOI: 10.1039/c2ta01035f
  68. 68. Mitchell E et al. Facile synthesis and morphogenesis of superparamagnetic iron oxide nanoparticles for high-performance supercapacitor applications. New Journal of Chemistry. 2014;38(9):4344-4350. DOI: 10.1039/c4nj00741g
  69. 69. Brousse T, Bélanger D. A hybrid Fe3O4-MnO2 capacitor in mild aqueous electrolyte. Electrochemical and Solid-State Letters. 2003;6(11):4-9. DOI: 10.1149/1.1614451
  70. 70. Qi T, Jiang J, Chen H, Wan H, Miao L, Zhang L. Synergistic effect of Fe3O4/reduced graphene oxide nanocomposites for supercapacitors with good cycling life. Electrochimica Acta. 2013;114:674-680. DOI: 10.1016/j.electacta.2013.10.068
  71. 71. Du X, Wang C, Chen M, Jiao Y, Wang J. Electrochemical performances of nanoparticle Fe3O4/activated carbon supercapacitor using KOH electrolyte sol. Journal of Physical Chemistry C. 2009;113(6):2643-2646. DOI: 10.1021/jp8088269
  72. 72. Wang L, Ji H, Wang S, Kong L, Jiang X, Yang G. Preparation of Fe3O4 with high specific surface area and improved capacitance as a supercapacitor. Nanoscale. 2013;5:3793-3799. DOI: 10.1039/C3NR00256J
  73. 73. Meng W, Chen W, Zhao L, Yang H, Zhu M, Huang Y, et al. Porous Fe3O4/carbon composite electrode material prepared from metal-organic framework template and effect of temperature on its capacitance. Nano Energy. 2014;8:133-140. DOI: 10.1016/j.nanoen.2014.06.007
  74. 74. Chen J, Huang K, Liu S. Hydrothermal preparation of octadecahedron Fe3O4 thin film for use in an electrochemical supercapacitor. Electrochimica Acta. 2009;55(1):1-5. DOI: 10.1016/j.electacta.2009.04.017
  75. 75. Shi W et al. Achieving high specific charge capacitances in Fe3O4/reduced graphene oxide nanocomposites. Journal of Materials Chemistry. 2011;21(10):3422-3427. DOI: 10.1039/c0jm03175e
  76. 76. Li X, Zhang L, He G. Fe3O4 doped double-shelled hollow carbon spheres with hierarchical pore network for durable high-performance supercapacitor. Carbon N. Y. 2016;99:514-522. DOI: 10.1016/j.carbon.2015.12.076
  77. 77. Chaudhari NK, Chaudhari S, Yu J-S. Cube-like α-Fe2O3 supported on ordered multimodal porous carbon as high performance electrode material for supercapacitors. ChemSusChem. 2014;7(11):3102-3111. DOI: 10.1002/cssc.201402526
  78. 78. Li Y, Jing X, Feng T, Yao Q, Xie J, Xia H. Fe2O3 Nanoneedles on ultrafine nickel nanotube arrays as efficient anode for high-performance asymmetric supercapacitors. Advanced Functional Materials. 2017;27(14):1606728. DOI: 10.1002/adfm.201606728
  79. 79. Owusu K, Qu L, Li J, et al. Low-crystalline iron oxide hydroxide nanoparticle anode for high-performance supercapacitors. Nature Communications. 2017;8:14264. DOI: 10.1038/ncomms14264
  80. 80. Mu J et al. Highly dispersed Fe3O4 nanosheets on one-dimensional carbon nanofibers: Synthesis, formation mechanism, and electrochemical performance as supercapacitor electrode materials. Nanoscale. 2011;3(12):5034-5040. DOI: 10.1039/c1nr10972c

Written By

Rajan Lakra, Rahul Kumar, Parasanta Kumar Sahoo, Sandeep Kumar and Ankur Soam

Submitted: 16 March 2022 Reviewed: 20 April 2022 Published: 17 June 2022