CoSe₂/WSe₂/rGO anode for high-performance energy storage device applications†

Divya Singh , Ashwani Maurya and Animesh K. Ojha *
Department of Physics, Motilal Nehru National Institute of Technology Allahabad, Prayagraj, 211004, India. E-mail: animesh@mnnit.ac.in

First published on 10th July 2025

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1. Introduction

The global energy requirements have necessitated the development of alternative energy generation technologies beyond traditional fossil fuel-based systems. However, the energy produced from non-conventional sources requires efficient devices for its storage. In this context, battery and supercapacitors play an important role in storing the energy produced by non-conventional sources. Thus, supercapacitors have emerged as a promising research area for scientists. Supercapacitors fill the void left by traditional capacitors and batteries by providing enhanced energy density and power density for a range of uses, such as portable devices, electric cars, and renewable energy systems.¹ This is attributed to the advancement of materials that offer high power density, enhanced charge–discharge cycle, and exceptional durability, in contrast to traditional energy storage devices.² Therefore, identifying suitable electrode materials for better charge storage is crucial for designing high-performance and durable supercapacitors.

Energy storage devices are often made of 2D nanomaterials owing to their high porous structural morphology.³ Transition metal chalcogenides (TMCs), including transition metal oxides, sulphides, and selenides are considered as favourable candidates for anode materials owing to their layered structures, variable oxidation states, favourable cyclic stability and electrical conductivity.^4–9 In TMCs, the layered structures are held together by van der Waals interactions.¹⁰ These layers provide a large surface area for effective charge storage.¹⁰ Sulphur and selenium, belonging to the same group in the periodic table, show comparable physical and chemical properties. However, metal selenides have better electrical conductivity than metal sulphides, and therefore, they are used as electrode materials for energy storage application.¹¹ Furthermore, transition metal selenides (TMSes) possess slightly large and weak metal–selenium bonds, which facilitate efficient insertion and extraction of ions at the electrode surface.¹² TMSes are appealing materials with a wide range of applications.¹³ TMSes such as MoSe₂, CoSe₂, WSe₂, and NiSe₂ have been used as electrode materials for supercapacitor applications.^14,15 WSe₂ provides quick electrolytic ion intercalation and de-intercalation that lead to maximal charge storage at the electrode surface.¹⁶ WSe₂ with a large surface area and interlayer spacing allow efficient ion intercalation. While its intrinsic conductivity is moderate, it provides structural stability and contributes additional pseudocapacitive storage through W⁴⁺/W⁶⁺ redox transitions.¹⁴ However, the low conductivity of WSe₂ makes it extremely hard to realize it as a better electrode material for energy storage device applications.¹⁷ Therefore, one of the objectives of this work is to enhance the conductivity of WSe₂ by developing its nanocomposite with relatively high conducting materials. In this context, we chose CoSe₂ and rGO, as these are reported to have better electrical conductivity,¹⁸ to fabricate CoSe₂/WSe₂/rGO nanocomposite. CoSe₂ has a cubic pyrite-type or orthorhombic marcasite-type crystal structure that has gained significant interest as an anode material for energy storage applications.⁷ CoSe₂ is a TMSe known for its excellent pseudocapacitive behaviour due to its rich redox activity involving Co²⁺/Co³⁺/Co⁴⁺ transitions.¹⁹ Previous studies have shown that the distinctive structure of CoSe₂ enhances ion diffusion at the electrode surface during the charge and discharge cycles.²⁰ Recently, it has been reported that the bi-metallic selenide performs relatively well than that of the monometallic selenide due to its better electrical conductivity.^12,21 The rGO is a two-dimensional material with high electrical conductivity, and is used to enhance the charge storage ability.²² Thus, it is expected that the addition of CoSe₂ and rGO in WSe₂ nanostructures may further improve its charge storage performance.²³

Considering the prior research on TMSe-based electrodes for energy storage applications,^24–28 we, herein, report the synthesis of a new ternary nanocomposite (CoSe₂/WSe₂/rGO) using a solvothermal method, and studied its electrochemical performance. A combination of materials such as CoSe₂, known for exceptional pseudocapacitive behaviour,²⁹ and rGO,³⁰ having high electrical conductivity, with WSe₂, having a layered structure with better electrochemical stability,^24,30 is expected to provide an electrode material with better energy storage performance and good cyclic durability. The synthesized CoSe₂/WSe₂/rGO nanocomposite was characterized by different experimental techniques. It is used as an electrode material for energy storage device applications.

2. Synthesis and characterization of CoSe₂/WSe₂/rGO

For the synthesis of CoSe₂/WSe₂/rGO nanocomposite, 0.32 g of Se powder, 20 mg of graphene oxide (GO), 0.1 g of NaBH₄ and sodium tungstate (Na₂WO₄) were mixed in 15 ml of N,N-dimethyl formamide (DMF). The prepared solution was stirred for 4–5 hours. Further, cobalt chloride (CoCl₂·6H₂O) and ethylenediaminetetraacetic acid (EDTA) were dissolved in 15 ml of DMF and hydrazine hydrate was added dropwise into it. The prepared solution was kept under stirring for 7–8 hours. After mixing both the solutions, the mixture was maintained under vigorous stirring for 1 hour. Thereafter, the final solution was poured into an autoclave lined with Teflon. The sealed autoclave was thermally processed in a furnace at 200 °C for 46 hours. The final product was separated, washed to eliminate unreacted precursors, and dried overnight at 60 °C in a controlled oven environment. Fig. 1 represents the schematic steps used to synthesize CoSe₂/WSe₂/rGO nanocomposite.

The XRD patterns of the material were recorded using a Rigaku smart lab diffractometer (CuKα, λ = 1.5406). A Renishaw Raman spectrometer was used to perform the Raman spectroscopy measurements. The Raman measurements were carried out using 514.5 nm as the excitation wavelength. The morphological studies of the synthesized materials were carried out by analyzing the results of scanning electron microscopy (ZEISS SEM) and transmission electron microscopy (TEM) (TECHNAI G2 20 TWIN) measurements. Thermogravimetric analysis (TGA) of the samples was performed under ambient conditions using a LINSEIS Thermobalance instrument. The surface area of the prepared samples was evaluated by Brunauer–Emmett–Teller (BET) analysis using nitrogen adsorption–desorption isotherms measured using a BELSORP-maxII instrument.

2.1. Electrochemical analysis of electrodes and the assembled ASC device

For the electrochemical analysis of the electrodes, we followed a similar procedure as reported in our earlier study.²³ For the three-electrode system, the mass loading of CoSe₂/WSe₂/rGO nanocomposite on the nickel foam substrate was found to be ∼2.1 mg cm⁻². Cyclic voltammetry (CV) measurements were carried out at various scan rates. The specific capacitance (SC) of an electrode was determined using the following formula:^29,31

	(1)

where SC, m, , S, and ΔV are the specific capacitance (F g⁻¹), mass loading on the Ni foam, area under the CV curve, sweep rate, and voltage window, respectively.

An asymmetric device (CoSe₂/WSe₂/rGO//AC) was assembled using CoSe₂/WSe₂/rGO as the anode and activated carbon (AC) as the cathode. The following expression was used to calculate the SC of the fabricated device:²⁴

	(2)

where I is the current, ΔT is the discharging time, ΔV is the voltage window, and M stands for the sum of the masses loaded on the cathode and anode. The energy density (E) and power density (P) of the device were calculated using the following equations:²³

	(3)

	(4)

where E and ΔT are the energy density and discharge time, respectively.

3. Results and discussion

3.1. XRD, Raman spectroscopy, TEM, TGA and BET measurements

Fig. 2(a) shows the XRD pattern of WSe₂, CoSe₂, rGO, and CoSe₂/WSe₂/rGO. The (002), (100), (102), (006), (105), (008) and (106) planes correspond to the 2H phase of WSe₂ (JCPDF no. 38-1388). The (110), (011), (101), (111), (120), (121), (211), (002), and (131) planes correspond to crystal phase of the CoSe₂ (JCPDF no. 53-0449). These peaks authenticate the formation of CoSe₂/WSe₂/rGO nanocomposite. We could not see any signature of rGO in the XRD pattern due to its low content and amorphous nature.²³ The presence of rGO in CoSe₂/WSe₂/rGO is confirmed by the D (∼1338 cm^{− 1}) and G (∼1580 cm^{− 1}) bands present in the Raman spectra given in the ESI† as Fig. S1. A higher I_D/I_G value for rGO (0.91) than that of GO (0.87) shows a successful reduction of GO into rGO.²³ The Raman spectra of WSe₂, CoSe₂, and CoSe₂/WSe₂/rGO are depicted in Fig. 2(b). The Raman peaks at ∼227 cm⁻¹ (E¹_2g) and ∼255 cm⁻¹ (A_1g) are ascribed to WSe₂. The peaks at ∼200 cm⁻¹ (A_g) and ∼675 cm⁻¹ (A_1g) are assigned to the CoSe₂.^12,23 The structural morphology of the synthesized materials was examined using the TEM images. The TEM image of the pure WSe₂ presented in Fig. 3(a) shows a layered sheet-type structure. The TEM image of CoSe₂ (see Fig. 3(b)) shows nanoplate-type structures with an average size of 25 nm. Fig. 3(c) shows the TEM image of the rGO sheets. Fig. 3(d) shows the TEM image of the CoSe₂/WSe₂/rGO nanocomposite. The image clearly reveals that the CoSe₂ nanoplates are anchored on the surfaces of WSe₂ and rGO sheets. This type of architecture provides better electron transport and ion diffusion, leading to enhanced energy storage performance of the electrode material.³² The thermal stability of the synthesized samples is assessed through TGA measurements and the corresponding data are presented in Fig. 4(a). For the TGA measurements, the CoSe₂/WSe₂/rGO nanocomposite, WSe₂ and CoSe₂ are subjected to a heating process from 25 to 900 °C at a rate of 5 °C per minute. The weight loss below ∼150 °C is due to the surface-adsorbed moisture and residual solvents present in the sample.³³ The increase in the weight of WSe₂ and CoSe₂ in the temperature range (200–400 °C) may be due to the formation of WO₃, CoO and SeO₂ oxides.³⁴ The weight of the CoSe₂/WSe₂/rGO nanocomposite does not increase in the temperature range of 200–400 °C. It may be due to the decomposition of oxygen-containing functional groups present in the rGO.³⁵ The weight loss of the CoSe₂/WSe₂/rGO nanocomposite in the temperature range of 400 °C to 650 °C is due to the formation of Co₃O₄ along with the complete combustion of the rGO.¹⁸ We noticed a weight loss of 46.3% for WSe₂, 59.5% for CoSe₂ and 48.6% for the CoSe₂/WSe₂/rGO. The surface area of WSe₂, CoSe₂, and CoSe₂/WSe₂/rGO was determined through N₂ adsorption–desorption curves (see Fig. 4(b)–(d)). Here, it is worth to mention that the surface area of CoSe₂/WSe₂/rGO (37 m² g⁻¹) is found to be relatively greater than that of the WSe₂ (21 m² g⁻¹) and CoSe₂, (19 m² g⁻¹). The enhanced surface area of CoSe₂/WSe₂/rGO facilitates increased active sites for electrochemical reactions and pathways for the adsorption and desorption of electrolyte ions at the electrode surface.³⁶ From Fig. 4(b)–(d), the pore diameter of the synthesized samples was calculated to be in the range of 3 to 25 nm. It shows that the electrode materials possess a mesoporous structure, which is favourable for their enhanced electrochemical performance.³⁶

3.2. Capacitive performance of the CoSe₂/WSe₂/rGO electrode

Cyclic voltammetry (CV) measurements were carried out to study the charge storage behaviour of WSe₂, CoSe₂, and CoSe₂/WSe₂/rGO electrodes in the voltage range of 0–0.6 V. Fig. 5(a) presents the CV curves of pure WSe₂, CoSe₂, rGO and CoSe₂/WSe₂/rGO at a sweep rate of 30 mV s⁻¹. The CV curves of WSe₂, and CoSe₂ electrodes revealed the Faradaic nature of the electrode. The enclosed area within the CV curve of CoSe₂/WSe₂/rGO is higher than that of the WSe₂ and CoSe₂ electrodes. Fig. 5(b) represents the CV curve of the CoSe₂/WSe₂/rGO electrode at different scan rates of 5–100 mV s⁻¹. The redox peaks shown in the CV curves of the CoSe₂/WSe₂/rGO electrode suggest the occurrence of Faradaic reactions, mainly associated with the transition metal present in CoSe₂ and WSe₂. In a 3 M KOH electrolyte solution, the following redox processes are likely to be accountable for the observed electrochemical activity:

In an alkaline electrolyte, CoSe₂ undergoes electrochemical oxidation–reduction transitions involving cobalt, as follows:^37,38

CoSe2 + OH− ↔ CoOOH + Se + e−

CoOOH + OH− ↔ CoO2 + H2O + e−

These reactions correspond to Co²⁺ ⇌ Co³⁺ ⇌ Co⁴⁺ transitions and contribute significantly to pseudo capacitance to the electrode.

WSe₂ contributes via surface redox reactions and intercalation/deintercalation processes involving tungsten oxidation as follows:

W4+ ↔ W6+ + 2e−

Although these reactions are typically more subtle than Co-based transitions, they assist in improving the overall charge storage behaviour through reversible redox activity. The CoSe₂/WSe₂/rGO electrode demonstrates a hybrid charge-storage mechanism, combining pseudocapacitive redox reactions with EDLC as confirmed by electrochemical kinetics analysis.²³ The increased area under the CV curves indicates that the electrons and ions are participating efficiently in the electrochemical process with less polarization impact.³⁹ It is evident that with the increase in sweep rates, the magnitude of cathodic and anodic current also increases. The anodic peak current and cathodic peak current slopes were determined to be 0.983 and 0.990, respectively. It indicates that the current is increased on both the sides and follow a linear pattern (see Fig. 5(c)). At a low sweep rate, the electrode surface is covered by a dense diffusion layer due to the movements of ions, which, in turn, reduces the value of peak current. In contrast, at a high sweep rate, the diffusion layer could not form on the electrode surface, which results in an increase in the peak current.⁴⁰ The pattern of the CV curves is found to be consistent. It indicates that the electrode material has a high electrochemical reversibility with a minimal polarization impact.⁴¹ The surface coverage (Γ) of the WSe₂, CoSe₂, and CoSe₂/WSe₂/rGO electrodes was determined using the following equation:⁴²

where, I_P stands for the peak current, R for the gas constant, s for the sweep rate, n for the total electron count, T for the temperature, and ‘a’ for the computed area of the working electrode. The value of I_p is higher for CoSe₂/WSe₂/rGO compared to WSe₂ and CoSe₂. It may be due to the high electrical conductivity of rGO.⁴³ It results in a higher value of Γ for CoSe₂/WSe₂/rGO. The power law is applied to quantify the capacitive and diffusive nature of the CoSe₂/WSe₂/rGO electrode.⁴⁴

IP = Asb

where s stands for the sweep rates, A and b are constants, and I_P stands for the peak current. Using the log(s) vs. log(I_P) graph, the ‘b’ value of the CoSe₂/WSe₂/rGO electrode was computed to be 0.69 for the sweep rate range, 5 to 100 mV s⁻¹ (see Fig. 5(d)). The calculated ‘b’ value indicates a mixed charge storage behaviour, with contributions from both, surface capacitive effects and diffusion-controlled processes at the electrode surface.

The galvanostatic charge–discharge (GCD) is the standard method for studying the electrochemical measurements of electrode materials at different currents. GCD curves of WSe₂, CoSe₂, rGO and CoSe₂/WSe₂/rGO electrodes are presented in Fig. 6(a) at 5 A g⁻¹. The GCD curve of pure WSe₂ and CoSe₂ shows Faradaic behaviour, whereas CoSe₂/WSe₂/rGO shows partial Faradaic behaviour with increased surface contribution. It was also observed that the CoSe₂/WSe₂/rGO electrode has the maximum discharge time. Fig. 6(b) shows the GCD curve of the CoSe₂/WSe₂/rGO electrode recorded at 2.6, 3.2, 4.0, 4.6, 5.0, 6.0, and 7.0 A g⁻¹. Using these curves, the SC of the CoSe₂/WSe₂/rGO electrode was determined to be 1756, 1486, 1476, 1359, 1333, 1213, and 1135 F g⁻¹ at 2.6, 3.2, 4.0, 4.6, 5.0, 6.0, and 7.0 A g⁻¹, respectively. The higher value of SC of CoSe₂/WSe₂/rGO (1756 F g⁻¹ at 2.6 A g⁻¹) compared to that of pure WSe₂ (752 F g⁻¹ at 2.6 A g⁻¹) and CoSe₂ (698 F g⁻¹ at 2.6 A g⁻¹) may be due to the synergistic interaction of WSe₂ and CoSe₂ with rGO, in which the rGO sheet facilitates efficient intercalation/deintercalation of electrolyte ions along with the rapid electron transport.³⁰ The rate capability of the CoSe₂/WSe₂/rGO electrode turns out to be significantly high in comparison to CoSe₂ and WSe₂ (see Fig. 6(c)). The SC of the CoSe₂/WSe₂/rGO electrode turns out to be far better than those reported in the literature for other WSe₂- and CoSe₂-based composites (see Table 1).^{17,23,25,45–50}

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The cyclic stability of WSe₂, CoSe₂ and CoSe₂/WSe₂/rGO electrodes was measured at 7 A g⁻¹ for 3000 cycles (see Fig. 6(d)). The SC of CoSe₂/WSe₂/rGO electrode drops by 7% compared to its initial value after 3000 cycles, whereas the SC of the WSe₂ and CoSe₂ electrode drops by 15% and 20%, respectively. WSe₂ is a stable electrode material,⁵¹ but the inclusion of rGO provides further stability to CoSe₂/WSe₂/rGO.⁵² We extended the cyclic stability test of the CoSe₂/WSe₂/rGO electrode from 3000 to 10000 cycles at a current density of 7.0 A g⁻¹. A drop of 19% in the value of its SC was observed after 10000 cycles (see the inset of Fig. 6(d)). Additionally, rGO also prevents the degradation of WSe₂ and CoSe₂ materials by decreasing its sensitivity to structural alterations during charge and discharge cycles.⁵³

The EIS measurements of the electrode materials are carried out to study their reaction kinetics and mechanism in the frequency range of 0.01 Hz–1.00 MHz at 10 mV. The Nyquist plot of WSe₂, CoSe₂, rGO, and CoSe₂/WSe₂/rGO is illustrated in Fig. 7(a). The higher rate of ion conduction in the electrolyte and quick redox reaction in CoSe₂/WSe₂/rGO are supported by the steeper and nearly vertical line in the low-frequency region (see Fig. 7(a)). The fitted curve along with the measured Nyquist plot of the CoSe₂/WSe₂/rGO electrode are shown in Fig. 7(b). The equivalent circuit thus obtained by fitting the Nyquist plot has R_s (600 mΩ), C (2.20 mF), R_ct (1.43 μΩ) and W (2.0 mMho).

To investigate the structural stability of the CoSe₂/WSe₂/rGO electrode before and after the electrochemical measurements, we also performed XRD, Raman spectroscopy, and SEM measurements. Fig. 8(a) shows the XRD patterns of the CoSe₂/WSe₂/rGO electrode before and after the electrochemical measurements. The (100), (006), and (008) planes correspond to the 2H phase of WSe₂ (JCPDF no. 38-1388) and the (110), (011), (111), (120), (211), (002), and (131) planes are assigned to CoSe₂ (JCPDF no. 53-0449). The XRD peaks that appeared at ∼44.5° and ∼51.7° correspond to the Ni-foam.⁵⁴ No appreciable shift or phase transformation in the XRD pattern was observed in the electrode material after the electrochemical measurement. It indicates that the crystalline structure of the CoSe₂/WSe₂/rGO electrode is structurally stable.⁵⁵ In contrast, a noticeable reduction in the intensity of characteristic Raman peaks of both WSe₂ and CoSe₂ nanostructured materials was observed after the electrochemical measurements (see Fig. 8(b)). This decrease in intensity can be attributed to the some structural degradation caused by repeated Faradaic redox processes.⁵⁶ Raman spectroscopy, a more sensitive tool for monitoring the structural changes at the molecular level, provides valuable insights regarding the structural modifications.^55,57 The SEM images of the CoSe₂/WSe₂/rGO electrode before and after the electrochemical measurements are shown in Fig. 8(c) and (d), respectively. Before cycling measurement, CoSe₂/WSe₂/rGO exhibits a well-integrated and uniform coating over the Ni foam, with a porous and interconnected structural morphology. After a long-term electrochemical measurement, the overall structural morphology of the CoSe₂/WSe₂/rGO electrode remains almost unchanged. It indicates good structural stability of the electrode material, which contributes to its superior cycling stability and long-term energy storage performance.

3.3. Capacitive performance of the ASC CoSe₂/WSe₂/rGO//AC device

An ASC device was fabricated utilizing AC as the counter electrode and CoSe₂/WSe₂/rGO as the anode. The electrochemical behaviour of the AC electrode is discussed in the ESI,† and the CV and GCD curves are presented in Fig. S2(a) and (b) (ESI†), respectively. To achieve efficient performance of the ASC device, we used standard charge balance theory, Q⁺ = Q⁻ (Q⁺ = M⁺C⁺ΔV⁺ and Q⁻ = M⁻C⁻ΔV⁻). Thus, the mass ratio of the materials was optimized using the following expression:²⁴

ΔV⁺ and M⁺ stand for the voltage window and mass loading on the anode. Similarly, for a counter electrode, potential window and mass loading are represented by ΔV⁻ and M⁻, respectively. The calculated weight ratio for the assembly of ASC device was determined to be 0.49. For the fabrication of the ASC device, the sum of mass loading on the positive and negative electrodes was found to be ∼3.0 mg cm⁻². The CoSe₂/WSe₂/rGO and AC electrodes have a voltage window of 0–0.6 V and −1.0 to 0 V, respectively. To confirm the electrochemical stability of the ASC device, we conducted linear sweep voltammetry (LSV) measurements of the assembled device with a two-electrode configuration. The scan was extended beyond the operating voltage (up to 2.2 V). The results (see Fig. S3, ESI†) showed that the current remains stable up to 1.6 V, with no signs of electrolyte decomposition or side reactions during the electrochemical measurements of the device. It confirms that the selected voltage window is appropriate for our ASC device. The CV curves of CoSe₂/WSe₂/rGO and AC also show that the fabricated ASC device can be operated in the potential window of 1.6 V (see Fig. 9(a)). Thus, the working voltage window of the ASC device turns out to be 1.6 V. Fig. 9(b) represents the CV curves of the ASC device at various sweep rates (5–50) mV s⁻¹. The low-intensity redox peaks in the voltammetric profile indicate that the device has a pseudocapacitive nature. The GCD curves of the CoSe₂/WSe₂/rGO//AC device recorded across multiple current densities are presented in Fig. 9(c). The SC of the CoSe₂/WSe₂/rGO//AC device was calculated by employing eqn (2), and its value was determined to be 213, 168, 155, 148, 135, 121 and 117 F g⁻¹ at current densities of 3, 4, 5, 6, 7, 8, and 9 A g⁻¹, respectively. The lack of a significant iR drop demonstrates efficient charge transfer with minimal resistance of CoSe₂/WSe₂/rGO//AC. Fig. 9(d) shows the experimental and fitted Nyquist plot of the ASC device towards a higher frequency region. The fitted Nyquist plot corresponds to an equivalent circuit containing a charge transfer resistance (R_ct = 273 mΩ), capacitance of double layer (C = 1.76 mF), solution resistance (R_s = 292 mΩ), and a Warburg impedance (Y₀ = 163 mMho). The low values of R_s, R_ct and Y₀ for the ASC device indicate the presence of better ionic conductivity during the electrochemical processes.

After 3000 GCD cycles at 8.0 A g⁻¹, the CoSe₂/WSe₂/rGO//AC device demonstrated a robust durability with 90% capacitance retention (see Fig. 9(e)). At a power density of 2234 W kg⁻¹, the device exhibits an energy density of 64 W h kg⁻¹. The Ragone plot of the device is depicted in Fig. 9(f). Compared to earlier studies, the CoSe₂/WSe₂/rGO//AC device exhibits enhanced electrochemical performance.^{23,48–50,58,59} The fabricated ASC devices were connected in series to meet the voltage/current requirements. The assembled device was charged using a DC power supply at a constant voltage of 5 V and with a charging current of 10 mA. After charging the device (CoSe₂/WSe₂/rGO//AC) for 30 s, it was used to power a yellow light-emitting diode (LED) (forward voltage ∼2.0 V). The LED remained continuously illuminated for ∼20 min. It demonstrate its practical energy storage capability for energy storage device applications.

4. Conclusions

In this study, we have used CoSe₂/WSe₂/rGO as an anode material for the fabrication of an ASC energy storage device. The CoSe₂/WSe₂/rGO electrode showed better energy storage (1756 F g⁻¹ at 2.6 A g⁻¹) performance with good rate capability compared to pure WSe₂ (752 F g⁻¹ at 2.6 A g⁻¹) and CoSe₂ (698 F g⁻¹ at 2.6 A g⁻¹). The fabricated ASC device (CoSe₂/WSe₂/rGO//AC) showed an energy density of 64 W h kg⁻¹ at a power density of 2234 W kg⁻¹ with long-term cycling stability. These results demonstrated the potential of CoSe₂/WSe₂/rGO electrode material for real-world supercapacitor applications, where both high energy and power densities are essential. The improved electrochemical performance and durability of the device suggest its suitability for applications in wearable electronics, backup power systems, and hybrid energy storage platforms.

Conflicts of interest

There are no conflicts to declare.

Data availability

The authors declare that the data related to the present study will be made available to the researchers upon request.

Acknowledgements

The authors gratefully acknowledge the financial support from MNNIT Allahabad (Prayagraj) and the instrumental resources provided by the Centre for Interdisciplinary Research (CIR).

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Footnote

† Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d5nj01871d

This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2025