Composite g-C3N4/NiCo2O4 with Excellent Electrochemical Impedance as an Electrode for Supercapacitors

Cui, Danfeng; Fan, Zheng; Fan, Yanyun; Chen, Hongmei; Li, Penglu; Duan, Xiaoya; Yan, Shubin; Xu, Hongyan; Xue, Chenyang

doi:https://doi.org/10.1155/2022/1023109

Journal of Nanomaterials

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Abstract Introduction Experimental Results and Discussion Conclusions Data Availability Conflicts of Interest References Copyright Related Articles

Research Article | Open Access

Volume 2022 | Article ID 1023109 | https://doi.org/10.1155/2022/1023109

Composite g-C₃N₄/NiCo₂O₄ with Excellent Electrochemical Impedance as an Electrode for Supercapacitors

Danfeng Cui,¹Zheng Fan,¹Yanyun Fan,¹Hongmei Chen,¹Penglu Li,¹Xiaoya Duan,¹Shubin Yan,^2,3Hongyan Xu,⁴and Chenyang Xue¹

Academic Editor: Vidya Nand Singh

Received17 Jun 2022

Revised17 Oct 2022

Accepted19 Oct 2022

Published05 Dec 2022

Abstract

For the development of supercapacitors, electrode materials with the advantages of simple synthesis and high specific capacitance are one of the very important factors. Herein, we synthesized g-C₃N₄ and NiCo₂O₄ by thermal polymerization method and hydrothermal method, respectively, and finally synthesized NiCo₂O₄/g-C₃N₄ nanomaterials by mixing, grinding, and calcining g-C₃N₄ and NiCo₂O₄. NiCo₂O₄/g-C₃N₄ nanomaterials are characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The microscopic morphology, lattice structure, and element distribution of NiCo₂O₄/g-C₃N₄ nanomaterials were characterized by scanning electron microscopy (SEM), transmission electron microscopy, high resoultion transmission electron microscopy, and mapping methods. The electrochemical performance and cycle stability of NiCo₂O₄/g-C₃N₄ were tested in a 6 M KOH aqueous solution as electrolyte under a three-electrode system. Due to the physical mixing structure of g-C₃N₄ and NiCo₂O₄ nanomaterials, the electrochemical energy storage performance of NiCo₂O₄/g-C₃N₄ supercapacitor electrodes is better than that of NiCo₂O₄ supercapacitor electrodes. At a current density of 1 A/g, the capacitances of NiCo₂O₄ and NiCo₂O₄/g-C₃N₄ are 98.86 and 1,127.71 F/g, respectively. At a current density of 10 A/g, the capacitance of NiCo₂O₄/g-C₃N₄ supercapacitor electrode maintains 70.5% after 3,000 cycles. NiCo₂O₄/g-C₃N₄ electrode has excellent electrochemical performance, which may be due to the formation of physical mixing between NiCo₂O₄ and g-C₃N₄, which has broad application prospects. This research is of great importance for the development of materials in high-performance energy storage devices, catalysis, sensors, and other applications.

1. Introduction

Supercapacitor is an energy storage device, which is different from battery and capacitor [1, 2]. It has the advantages of fast charging speed [3], long service life [4], high electricity conversion efficiency [5], high power density [6], high safety factor, and green friendliness. Supercapacitors are used in many fields such as wind power generation systems, heavy-duty machinery, and hybrid vehicles. According to different principles, supercapacitors are classified as double-layer capacitors and pseudo-capacitors. Pseudo-capacitors [2], as a kind of supercapacitors, have been studied due to their advantages of higher discharge time and larger stored power. The supercapacitor electrode is the most crucial part of the storage capacity of the supercapacitor. In previous studies, pseudo-capacitance electrodes are mainly composed of oxides of elements such as Co [7–9], Fe [10, 11], Ru [12–14], Mn [15, 16], Ni [17, 18], W [19, 20], and Zn [21, 22]. These metal oxides have relatively high theoretical capacitance values [23, 24], and the synthesis method is simple. In recent years, multimetal oxides [25–27] have gradually attracted attention because of their excellent theoretical capacitance, high-power density, and outstanding cycling characteristics. Among them, the theoretical capacitance value of NiCo₂O₄ is 890 mAh/g [28], and it has good electrical conductivity due to the presence of bimetallic elements. These advantages provide support for NiCo₂O₄ to become a promising electrode material for supercapacitors [29]. Li et al. [30] facilely synthesized and electrochemically tested NiCo₂O₄ with different crystal structures. By controlling the ratio of CO(NH₂)₂ and NH₄F composition, the crystal growth structure of NiCo₂O₄ was controlled. Among them, the NiCo₂O₄ with the best mass-specific capacitance is 1,710.9 F/g. However, a noncomposite bimetal oxide as a supercapacitor electrode usually has a large electrochemical impedance. By using suitable materials to compound with bimetallic oxides, it will usually help the electrode to have good electrochemical impedance.

Graphite carbon nitride (g-C₃N₄) [31–33] is a widely used carbon-based material. g-C₃N₄ is a flexible layered structural material with good chemical stability, nontoxic, nonpolluting, and low cost [34–36]. Due to the presence of pyrrole nitrogen hole defects in the crystal lattice and the reduced distance between the edge covalent nitrogen atoms, the material exhibits a higher rate capability. Moreover, the porous heptazine and sp2 hybrid nitrogen also provide coordination sites [37]. With the synthesis of bimetallic transition metal element oxides dispersed on the g-C₃N₄ grid (with improved redox sites), its conductivity, electrochemical performance, hydrophilicity, and surface polarity have been enhanced. This allows supercapacitor electrodes to obtain excellent cycle performance and high-rate performance [38, 39]. Rabani et al. [37] studied the compound-prepared method and electrochemical performance of Co₃O₄@g-C₃N₄. The experimental results show that the capacitance of the Co₃O₄@g-C₃N₄ supercapacitor reaches 457.2 F/g, and it maintains 92% of the capacitance after 5,000 cycles. Thiagarajan et al. [40] synthesized NiMoO₄/g-C₃N₄ by hydrothermal method and tested its electrochemical energy storage performance. The supercapacitor electrode NiMoO₄/g-C₃N₄ reached 510 F/g, and maintained 91.8% capacity after 2,000 cycles.

In this study, g-C₃N₄ is synthesized by thermal polymerization, NiCo₂O₄ is synthesized by hydrothermal method and thermal oxidation method. g-C₃N₄/NiCo₂O₄ nanomaterial is synthesized by fully grinding and calcining g-C₃N₄ and NiCo₂O₄. It can be observed that physical mixing structures of g-C₃N₄ and NiCo₂O₄ are formed in the g-C₃N₄/NiCo₂O₄ nanomaterial using TEM. Due to the existence of the physical mixing, the g-C₃N₄/NiCo₂O₄ nanomaterial has a higher mass-specific capacitance compared with NiCo₂O₄ when used as a supercapacitor electrode. By studying the electrochemical impedance spectroscopy (EIS) of the materials, the g-C₃N₄/NiCo₂O₄ nanomaterial has very low electrochemical impedance in the low-frequency response, showing good electrochemical energy storage performance.

2. Experimental

2.1. Preparation of the NiCo₂O₄/g-C₃N₄ Nanomaterial

At first, 20 g of urea was placed in a corundum crucible and placed in a tube furnace. Then set the heating rate of the tube furnace to 10°C/min. The tube furnace temperature was maintained at 550°C for 180 min. After waiting for the complete natural cooling to room temperature, the sample was taken out and fully ground to obtain g-C₃N₄ powder. Then, the NiCo₂O₄ was prepared by combining with hydrothermal method and annealing. To get the solution for the preparation of NiCo₂O₄ nanoparticles, the reagent with the precise molar ratio of NiCl₂·6H₂O : CoCl₂·6H₂O : CO(NH₂)₂ : NH₄F = 1 : 2 : 6 : 15 was dissolved in 30 mL of deionized water (DI water). After magnetic stirring for 15 min, the evenly mixed aqueous solution was moved into the polytetrafluoroethylene lining of the high-pressure reactor, heated at 150°C for 8 hr, and then cooled and centrifuged to get the NiCo₂O₄ precursor. And NiCo₂O₄ precursors were annealed in a tubular furnace at 400°C for 2 hr to get NiCo₂O₄ crystals. Finally, 2% g-C₃N₄ and NiCo₂O₄ were mixed and fully pulverized, then calcined in a tubular furnace at 550°C for 180 min to get 2% g-C₃N₄/NiCo₂O₄ powder.

2.2. Preparation of the Electrodes

First, nickel foam was cleaned with ultrasonic DI water and dried at 60°C for 6 hr. After that, NiCo₂O₄/g-C₃N₄ trituration was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 0.8 : 0.15 : 0.05. A few drops of alcohol and 5% polytetrafluoroethylene were added and stirred. The foam was coated with nickel foam and the electrodes were dried for 24 hr for electrochemical test.

2.3. Characterization of the NiCo₂O₄/g-C₃N₄ Nanomaterial

The micromorphology of the nanomaterial surface was investigated by SEM (FEI Quanta FEG 250). The lattice structure of the NiCo₂O₄/g-C₃N₄ nanomaterial was investigated by a transmission electron microscope (Tecnai G2 F20). The NiCo₂O₄/g-C₃N₄ nanomaterial was confirmed by X-ray diffraction (XRD) (Rigaku Ultimate IV). The chemical composition was analyzed by X-ray photoelectron spectroscopy (XPS) (Thermo ESCALAB 250Xi).

2.4. Electrode Performance Test Method

The electrode performance test was carried out under the three-electrode system of working electrode (foamed nickel with NiCo₂O₄/g-C₃N₄ nanomaterial), counter electrode (platinum electrode), and reference electrode (saturated calomel electrode). Cyclic voltammetry (CV), galvanostatic current charging–discharging (GCD), EIS, and cycling ability were tested in a 6 M KOH aqueous solution through an electrochemical workstation (Metrohm Multi Autolab M204).

3. Results and Discussion

Figure 1 shows the XRD spectrum of g-C₃N₄, NiCo₂O₄, and NiCo₂O₄/g-C₃N₄ composite nanomaterials. The blue line of g-C₃N₄ in Figure 1 has an obvious (002) peak. The green line in the figure represents the XRD line of NiCo₂O₄ nanoparticles. All the peaks in the line can correspond to the cubic crystal orientation of NiCo₂O₄ PDF#20-0781 (111) (220) (311) (222) (400) (511) (440), and there are no other obvious peaks [30, 41]. Therefore, the green line in the XRD spectrum proves that we have prepared NiCo₂O₄ nanoparticles with higher purity. The red line in Figure 1 represents the XRD spectrum of the NiCo₂O₄/g-C₃N₄ composite nanomaterial. In the red line, the (220) (311) (222) (511) (440) peaks correspond to the NiCo₂O₄ in the NiCo₂O₄/g-C₃N₄ composite nanomaterial. The XRD spectrum shows that the (111) lattice peak of nickel cobalt oxide is shifted. And the appearance of the (002) peak [40] represents the successful composite of NiCo₂O₄ nanoparticles and g-C₃N₄ nanomaterials, and the NiCo₂O₄/g-C₃N₄ nanomaterials were successfully prepared.

Figure 2 shows the SEM images of g-C₃N₄, NiCo₂O₄, and NiCo₂O₄/g-C₃N₄. Figures 2(a) and 2(b) are SEM images of g-C₃N₄. It could be observed from Figure 2(a) that there are 200–300 nm pores between the g-C₃N₄ nanoparticles. It can be observed from Figure 2(b) that the micron morphology of the g-C₃N₄ nanoparticles is porous floc. Such a structure significantly increases the effective boundary area between the nanomaterial and the electrolyte. Furthermore, the porous floc can improve the electrochemical energy storage contact interface to improve electrochemical energy storage performance. Figures 2(c) and 2(d) are SEM pictures of NiCo₂O₄ nanoparticles. It can be observed from Figure 2(c) that the dimension of NiCo₂O₄ nanoparticles is 50–100 nm. The particle size of NiCo₂O₄ matches the size of the nanopores of g-C₃N₄, which can better complete the composite between nanomaterials. Figures 2(e) and 2(f) are SEM images of NiCo₂O₄/g-C₃N₄ composite material. It can be seen in Figure 2(e) that NiCo₂O₄ nanoparticles are partially embedded in the nanopores of g-C₃N₄. NiCo₂O₄ nanoparticles and g-C₃N₄ nanomaterials are effectively combined through the method shown in Figure 2(e) to improve the electrochemical performance of NiCo₂O₄/g-C₃N₄ composite nanomaterials.

Figures 3(a)–3(d) is TEM images of g-C₃N₄, NiCo₂O₄, and NiCo₂O₄/g-C₃N₄ composite nanomaterials, respectively. We can observe from Figure 3(d) that NiCo₂O₄ and g-C₃N₄ are in close contact to form a NiCo₂O₄/g-C₃N₄ composite nanomaterial. As shown in Figures 3(a) and 3(b), NiCo₂O₄ has smaller particles and structures than g-C₃N₄. The g-C₃N₄/NiCo₂O₄ nanomaterials are synthesized by grinding and calcining g-C₃N₄ and NiCo₂O₄. As shown in Figure 3(c), the larger area of g-C₃N₄ forms a physical mixing structure with smaller particles of NiCo₂O₄. Figure 3(d) is a larger magnification TEM image of g-C₃N₄/NiCo₂O₄ nanomaterials, which clearly shows the physical mixing structure formed by NiCo₂O₄ nanoparticles on the larger structure of g-C₃N₄. And comparing with the size of NiCo₂O₄ particles in Figure 3(b), the black particles in Figure 3(d) are NiCo₂O₄ particles after forming a composite with g-C₃N₄. Figure 3(e) is the high resoultion transmission electron microscopy (HRTEM) image of NiCo₂O₄/g-C₃N₄. In the figure, the distance between the crystal orientations of NiCo₂O₄ (220) and (311) is marked, which matches the XRD analysis result. Figure 3(f) shows the element mapping of NiCo₂O₄/g-C₃N₄ composite nanomaterials. In Figure 3(f), it can be clearly seen that C, N, O, Co, and Ni are uniformly distributed in the NiCo₂O₄/g-C₃N₄ composite nanomaterial, which proves the successful composite of NiCo₂O₄/g-C₃N₄ material.

Figure 4 shows the XPS spectrum of the g-C₃N₄/NiCo₂O₄ composite nanomaterial. It can be clearly observed in Figure 4(a) that composite nanomaterials have elements such as C, N, O, Co, and C. In Figure 4(b), the peak splitting and fitting of Ni 2p can be clearly observed. Due to the existence of the spin orbits of Ni³⁺ and Ni²⁺, the two main peaks are 873.6 and 856.4 eV, respectively. Among them, the two weaker peaks are due to the weaker accompanying peaks produced by Ni³⁺ and Ni²⁺, which are also related to Ni³⁺ and Ni²⁺. The O 1s spectrum in Figure 4(d) shows three oxygen peaks, concentrated at 531.12, 532.57, and 529.66 eV. This is due to the formation of oxides by the OH⁻ and O²⁻ of Ni and Co, which correspond to these three peaks. The C 1s spectrum in Figure 4(e) has three carbon peaks at ∼284.8, 286.03, and 288.16 eV, which are related to the formation of carbon–carbon bonds and carbon–nitrogen bonds [35]. The N 1s spectrum in Figure 4(f) shows three nitrogen peaks, concentrated at 399.27, 400.19, 401.32, and 403.31 eV [39].

(a)

(b)

(c)

(d)

(e)

(f)

First, we tested NiCo₂O₄ and g-C₃N₄/NiCo₂O₄ supercapacitor electrodes by CV. Figures 5(a) and 5(b) are the CV test curves of NiCo₂O₄ and g-C₃N₄/NiCo₂O₄ supercapacitor electrodes. NiCo₂O₄ and g-C₃N₄/NiCo₂O₄ supercapacitor electrodes were tested with different scan rates (5–100 mV/s) under the voltage of 0–0.45 V. Figure 5(a) clearly shows the redox peak of NiCo₂O₄ nanomaterials, indicating that NiCo₂O₄ supercapacitor electrodes have pseudo-capacitance characteristics. When the scan rate increases, the redox peak of the NiCo₂O₄ supercapacitor electrode shifts to a higher or lower voltage value, which is caused by the internal resistance of the electrode and the tortuous diffusion path of H⁺ ions in the supercapacitor electrode material. It can be clearly observed in Figure 5(b) that, compared with the NiCo₂O₄ supercapacitor electrode, the redox peak of the g-C₃N₄/NiCo₂O₄ supercapacitor electrode has a higher peak value. This shows that the g-C₃N₄/NiCo₂O₄ supercapacitor electrode has a higher working voltage window for electrochemical energy storage and is more suitable for high-voltage energy storage applications. It can be clearly observed in Figure 5(b) that the g-C₃N₄/NiCo₂O₄ supercapacitor electrode has a larger integration area compared to the NiCo₂O₄ supercapacitor electrode. This means that the g-C₃N₄/NiCo₂O₄ supercapacitor electrode has a higher electrochemical energy storage capacity. And the CV curve in Figure 5(b) is more symmetrical, indicating that the electrode of the g-C₃N₄/NiCo₂O₄ supercapacitor can undergo a more complete reversible reaction. In addition, the reaction equation represented by the redox peaks in Figures 5(a) and 5(b) should be

(a)

(b)

(c)

(d)

(e)

(f)

Figures 5(c) and 5(d) are the GCD test diagrams of NiCo₂O₄ supercapacitor electrode and g-C₃N₄/NiCo₂O₄ supercapacitor electrode. The GCD test is to characterize the electrochemical energy storage capacity of the electrode more conveniently by using a constant current to charge and discharge the electrode. Mass-specific capacitance and area-specific capacitance can be calculated by the following two formulae:

In Formula (3), C_s is the area-specific capacitance, I is the current during constant current discharge, t is the discharge time, V is the potential difference during discharge, s is the electrode area of the supercapacitor, and is the mass-specific capacitance, m is the material quality of the supercapacitor loaded by the electrode. The loading weights of the NiCo₂O₄ and g-C₃N₄/NiCo₂O₄ composite material on the electrode used in the electrochemical energy storage test were 14.9 and 8.9 mg, respectively. It can be clearly observed from Figures 5(c) and 5(d) that the discharge time of the g-C₃N₄/NiCo₂O₄ supercapacitor electrode is much longer than that of the NiCo₂O₄ supercapacitor electrode under the same charge and discharge current. Calculated by Formula (3), when the charge and discharge current is 1–8 A/g, the mass-specific capacitance content of NiCo₂O₄ supercapacitor electrode is 98.86, 82.86, 69.43, 50, and 32 F/g. The area-specific capacitance of NiCo₂O₄ supercapacitor electrodes is 1.4829, 1.2429, 1.04145, 0.75, and 0.48 F/cm², respectively. However, when the charge and discharge current is 1–10 A/g, the mass-specific capacitance content of the g-C₃N₄/NiCo₂O₄ supercapacitor electrode is 1,127.71, 1,031.43, 947.14, 811.43, 637.71, and 517.14 F/g. The area-specific capacitances of the g-C₃N₄/NiCo₂O₄ supercapacitor electrodes are 16.92, 15.47, 14.21, 12.17, 9.57, and 7.7571 F/cm², respectively. Compared with the mass-specific capacitance of the NiCo₂O₄ supercapacitor electrode, the mass-specific capacitance of the g-C₃N₄/NiCo₂O₄ supercapacitor electrode has been significantly improved due to the synergistic effect of the g-C₃N₄/NiCo₂O₄ composite nanomaterial. Figure 5(e) is the comparison of mass-specific capacitance between NiCo₂O₄ supercapacitor electrode and g-C₃N₄/NiCo₂O₄ supercapacitor electrode under different current charging and discharging conditions. It can be seen in Figure 5(e) that at higher operating currents, g-C₃N₄/NiCo₂O₄ supercapacitor electrodes have better rate characteristics. Figure 5(f) shows the retention of the mass-specific capacitance of the g-C₃N₄/NiCo₂O₄ supercapacitor electrode at a current of 10 A/g after 3,000 cycles. After 3,000 cycles of the g-C₃N₄/NiCo₂O₄ electrode, the mass-specific capacitance of the comparison electrode was maintained at 70.5% before the cycle test, which has an acceptable capacitance retention. The decrease in the capacitance value of the composites may be caused by the dissolution effect of the alkaline electrolyte on the nickel cobaltate combined with the minor structural instability of the physical mixing [42].

Equation (4) is the calculation formula of energy density and power density, respectively. Among them, E, C, V, P, and t in Equation (4) are energy density, capacitance, potential, power density, and discharge time, respectively. Calculated by the formula, the highest energy density of the composite material is 69.07 Wh/kg, and the power density is 603.54 W/kg.

EIS is a nondestructive parameter measurement and an effective method for determining the dynamic behavior of electrochemical energy storage devices [43, 44]. We apply a sinusoidal signal with a weak amplitude to the supercapacitor electrodes in the three-electrode supercapacitor system to obtain the change in the ratio of the excitation voltage to the response current, which is the impedance spectrum of the electrochemical system. The electrochemical impedance curve of electrodes made of NiCo₂O₄ and g-C₃N₄/NiCo₂O₄ is measured in the frequency range of 100,000–0.1 Hz. Figures 6(a) and 6(b) are the AC impedance spectrum curves of NiCo₂O₄ and g-C₃N₄/NiCo₂O₄. The intersection of the AC impedance spectrum curve and the x-axis is the solution resistance (R_s) at the interface between the electrolyte and the electrode. The partly circular AC impedance spectrum curve in the high-frequency region is mainly dominated by the charge transfer of the electrode material [45, 46]. The slope of the low-frequency region shows the diffusion coefficient of the material, which is mainly dominated by the material transfer of the electrode material. R_s in electrochemical impedance spectroscopy of NiCo₂O₄ is 0.46 Ω, R_s in electrochemical impedance spectroscopy of g-C₃N₄/NiCo₂O₄ is 0.374 Ω. This proves that the g-C₃N₄/NiCo₂O₄ composite nanomaterial has better conductivity than the single NiCo₂O₄. The argument of Q (CPE) has nothing to do with frequency and is called constant phase angle element. Generally, when the Q parameter n is between 1 and 0.5, there is a dispersion effect on the pole surface. When n = 0.5, CPE can be used to replace the Warburg element of the finite diffusion layer, and CPE can also simulate the high-frequency part of the Warburg element of infinite thickness. The linear slope of the g-C₃N₄/NiCo₂O₄ electrode in the low-frequency region is higher than that of the NiCo₂O₄ electrode. It shows that the mobility of electrolyte ions on the surface of g-C₃N₄/NiCo₂O₄ electrode is higher than that on the surface of NiCo₂O₄ electrode. In Figure 3(d), it can be clearly observed that g-C₃N₄ forms a physical mixing structure with NiCo₂O₄. From the above discussion, it can be seen that the electron mobility in the g-C₃N₄/NiCo₂O₄ composite can be improved, and the electrochemical impedance spectroscopy shows a lower electrochemical impedance.

(a)

(b)

Table 1 shows the comparison of mass-specific capacitance values of metal oxides and carbon nitride composite nanomaterials. The g-C₃N₄/NiCo₂O₄ prepared in this study exhibited high mass-specific capacitance.

4. Conclusions

In this paper, we synthesized g-C₃N₄ and NiCo₂O₄ by thermal polymerization method and hydrothermal method, respectively, and finally synthesized NiCo₂O₄/g-C₃N₄ nanomaterials by fully mixing, grinding, and calcining g-C₃N₄ and NiCo₂O₄. Due to the effective combination of g-C₃N₄ and NiCo₂O₄ nanomaterials, the electrochemical energy storage performance of NiCo₂O₄/g-C₃N₄ supercapacitor electrodes is better than that of NiCo₂O₄ supercapacitor electrodes. At a current of 1 A/g, the mass-specific capacitances of NiCo₂O₄ and NiCo₂O₄/g-C₃N₄ are 98.86 and 1,127.71 F/g, respectively. At a current of 10 A/g, the NiCo₂O₄/g-C₃N₄ supercapacitor electrode maintains 70.5% of capacitance after 3,000 cycles. Moreover, NiCo₂O₄/g-C₃N₄ electrode shows an excellent electrochemical impedance compared with single NiCo₂O₄ electrode. NiCo₂O₄/g-C₃N₄ electrode has excellent electrochemical performance, which may be due to the formation of physical mixing between NiCo₂O₄ and g-C₃N₄, which has broad application prospects. This research is of great importance for the development of materials in high-performance energy storage devices, catalysis, sensors, and other applications.

Data Availability

The data used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Funding

This work was funded by the National Key Research and Development Program of China, grant numbers 2020YFB2008804 and 2019YFB2004800, and also by the National Natural Science Foundation of China, grant number 62071432. This work was supported in part by the Zhejiang Provincial Natural Science Foundation of China under grant number LD21F050001 and Development Project of Zhejiang Province under grant number 2021C03019.

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Copyright © 2022 Danfeng Cui et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Journal of Nanomaterials

Composite g-C3N4/NiCo2O4 with Excellent Electrochemical Impedance as an Electrode for Supercapacitors

Abstract

1. Introduction

2. Experimental

2.1. Preparation of the NiCo2O4/g-C3N4 Nanomaterial

2.2. Preparation of the Electrodes

2.3. Characterization of the NiCo2O4/g-C3N4 Nanomaterial

2.4. Electrode Performance Test Method

3. Results and Discussion

4. Conclusions

Data Availability

Conflicts of Interest

Funding

References

Copyright

Composite g-C₃N₄/NiCo₂O₄ with Excellent Electrochemical Impedance as an Electrode for Supercapacitors

2.1. Preparation of the NiCo₂O₄/g-C₃N₄ Nanomaterial

2.3. Characterization of the NiCo₂O₄/g-C₃N₄ Nanomaterial