Fe substitution in urchin-like NiCo2O4 for energy storage devices

A composite of NiCo_2−xFe_xO₄ was designed to investigate the effects of Fe substitution on its energy storage performance. Urchin-like products composed of nanowires were successfully synthesized through the hydrothermal method and calcinations. Scanning electron microscopy (SEM) images revealed that Fe substitution could reduce the diameter of the nanowires and hinder the urchin-like sphere construction. X-ray diffraction (XRD), energy dispersive X-ray mapping (EDS-mapping) and X-ray photoelectron spectroscopy (XPS) revealed the successful Fe substitution for Co. More importantly, the specific capacity could be largely improved from 359 C g⁻¹ (826 F g⁻¹) for x = 0 to 523 C g⁻¹ (1188 F g⁻¹) for x = 0.3 at 1 A g⁻¹. Moreover, with x = 0.3, a specific capacity of 788 F g⁻¹ could be maintained as the current density was increased to 20 A g⁻¹. Asymmetric supercapacitors based on this compound exhibited an energy density of 26.6 W h kg⁻¹ at a power density of 370 W kg⁻¹.

A composite of NiCo_2−xFe_xO₄ was designed to investigate the effects of Fe substitution on its energy storage performance.     

Optimized NiCo2O4/rGO hybrid nanostructures on carbon fiber as an electrode for asymmetric supercapacitors

The NiCo₂O₄ nanowires and reduced graphene oxide (rGO) hybrid nanostructure has been constructed on carbon fibers (NiCo₂O₄/rGO/CF) via a hydrothermal method. The effects of graphene oxide (GO) concentration on the structure and performance of the NiCo₂O₄/rGO/CF were investigated in detail to obtain the optimized electrode. When the GO concentration was 0.4 mg ml⁻¹, the rGO/NiCo₂O₄/CF composite exhibited a maximum specific capacitance of 931.7 F g⁻¹ at 1 A g⁻¹, while that of NiCo₂O₄/CF was 704.9 F g⁻¹. Furthermore, the NiCo₂O₄/rGO/CF//AC asymmetric supercapacitor with a maximum specific capacitance of 61.2 F g⁻¹ at 1 A g⁻¹ was fabricated, which delivered a maximum energy density (24.6 W h kg⁻¹) and a maximum power density (8477.7 W kg⁻¹). Results suggested that the NiCo₂O₄/rGO/CF composite would be a desirable electrode for flexible supercapacitors.

The NiCo₂O₄ nanowires and rGO hybrid nanostructure was constructed on carbon fibers (NiCo₂O₄/rGO/CF) via a hydrothermal method.     

Facile one-pot synthesis of NiCo2Se4-rGO on Ni foam for high performance hybrid supercapacitors

A facile, innovative synthesis for the fabrication of NiCo₂Se₄-rGO on a Ni foam nanocomposite via a simple hydrothermal reaction is proposed. The as-prepared NiCo₂Se₄-rGO@Ni foam electrode was tested through pxrd, TEM, SEM, and EDS to characterize the morphology and the purity of the material. The bimetallic electrode exhibited outstanding electrochemical performance with a high specific capacitance of 2038.55 F g⁻¹ at 1 A g⁻¹. NiCo₂Se₄-rGO@Ni foam exhibits an extensive cycling stability after 1000 cycles by retaining 90% of its initial capacity. A superior energy density of 67.01 W h kg⁻¹ along with a high power density of 903.61 W kg⁻¹ further proved the high performance of this electrode towards hybrid supercapacitors. The excellent electrochemical performance of NiCo₂Se₄-rGO@Ni foam can be explained through the high electrocatalytic activity of NiCo₂Se₄ in combination with reduced graphene oxide which increases conductivity and surface area of the electrode. This study proved that NiCo₂Se₄-rGO@Ni foam can be utilized as a high energy density-high power density electrode in energy storage applications.

A hybrid supercapacitor comprising a NiCo₂Se₄-rGO composite has been fabricated on Ni foam and shows high energy and power density and superior flexibility.     

CuCo2O4 nanoneedle array with high stability for high performance asymmetric supercapacitors

Cycling performance is very important to device application. Herein, a facile and controllable approach is proposed to synthesize high stability CuCo₂O₄ nanoneedle array on a conductive substrate. The electrode presents excellent performances in a large specific capacitance up to 2.62 F cm⁻² (1747 F g⁻¹) at 1 mV s⁻¹ and remarkable electrochemical stability, retaining 164% even over 70 000 cycles. In addition, the asymmetric supercapacitor assembled with the optimized CuCo₂O₄ nanoneedle array (cathode) and active carbon (anode), which exhibits superior specific capacity (146 F g⁻¹), energy density (57 W h kg⁻¹), and cycling stability (retention of 83.9% after 10 000 cycles). These outstanding performances are mainly ascribed to the ordered binder-free nanoneedle array architecture and holds great potential for the new-generation energy storage devices.

The CuCo₂O₄ nanoneedle array with enhanced electrochemical performance especially high stability is due to the hierarchical porosity framework with the high mesoporous nanoneedle array.     

High performance asymmetric supercapacitors based on Ti3C2Tx MXene and electrodeposited spinel NiCo2S4 nanostructures

Spinel metal sulfides have been investigated for a wide range of applications mostly in electrochemical energy storage owing to their better electronic conductivity and high reversible redox activity. Herein, we report a facile fabrication approach for the binder-free supercapacitor electrodes based on spinel NiCo₂S₄ (NCS) on various substrates such as Cu-foil (CF), Ni-foam (NF), and vertical graphene nanosheets grown on carbon tape (VG) via a single step-controlled electrodeposition technique. The obtained electrodeposited NiCo₂S₄ grown on Cu-foil (denoted as CF-NCS) in symmetric assembly shows a high specific capacitance of 167.28 F g⁻¹ compared to NCS grown on Ni-foam and VG substrates, whereas, symmetric NiCo₂S₄ grown on a VG substrate device exhibits better cycling performance (81% for 3000 cycles) compared to CF-NCS and NF-NCS. Furthermore, an asymmetric supercapacitor was assembled in combination with MXene (Ti₃C₂T_x) as a negative electrode (denoted as TCX). As a result, the CF-NCS//TCX device exhibits a high areal capacitance of 48.6 mF cm⁻² at 2 mA cm⁻² of current density. We also report good specific capacitance of 54.57 F g⁻¹ at 2 A g⁻¹; in addition, the CF-NCS//TCX assembly delivers maximum areal and gravimetric energy density of 14.86 mWh cm⁻² and 14.86 Wh kg⁻¹ respectively. In contrast, the VG-NCS//TCX device showed improved cycling stability with 85% of capacitance retention over 5000 cycles owing to its highly porous structure and multiple conductive networks in the VG substrate and provides structural stability to NCS with fast ion diffusion. This experiment favors 2D MXene as a capacitive electrode that provides a replacement for carbon-based electrodes in asymmetric assembly with superior electrochemical performance. Hence, the hierarchical NCS structure grown on the various substrates in combination with MXene serve as a promising material for energy storage application.

Spinel metal sulfides have been investigated for a wide range of applications mostly in electrochemical energy storage owing to their better electronic conductivity and high reversible redox activity.     

Marigold micro-flower like NiCo2O4 grown on flexible stainless-steel mesh as an electrode for supercapacitors

Nanostructured NiCo₂O₄ is a promising material for energy storage systems. Herein, we report the binder-free deposition of porous marigold micro-flower like NiCo₂O₄ (PNCO) on the flexible stainless-steel mesh (FSSM) as (PNCO@FSSM) electrode by simple chemical bath deposition. The SEM and EDS analysis revealed the marigold micro-flowers like morphology of NiCo₂O₄ and its elemental composition. The porous nature of the electrode is supported by the BET surface area (100.47 m² g⁻¹) and BJH pore size diameter (∼1.8 nm) analysis. This PNCO@FSSM electrode demonstrated a specific capacitance of 530 F g⁻¹ at a high current density of 6 mA cm⁻² and revealed 90.5% retention of specific capacitance after 3000 cycles. The asymmetric supercapacitor device NiCo₂O₄//rGO within a voltage window of 1.4 V delivered a maximum energy density of 41.66 W h kg⁻¹ at a power density of 3000 W kg⁻¹. The cyclic stability study of this device revealed 73.33% capacitance retention after 2000 cycles. These results indicate that the porous NiCo₂O₄ micro-flowers electrode is a promising functional material for the energy storage device.

Binder-free marigold micro-flower like NiCo₂O₄ deposited on FSSM as electrode in ASC device (NiCo₂O₄//rGO) is a promising functional material for energy storage device.     

Zeolitic imidazolate framework derived ZnCo2O4 hollow tubular nanofibers for long-life supercapacitors

Uniform one-dimensional metal oxide hollow tubular nanofibers (HTNs) have been controllably prepared using a calcination strategy using electrospun polymer nanofibers as soft templates and zeolitic imidazolate framework nanoparticles as precursors. Utilizing the general synthesis method, the ZnO HTNs, Co₃O₄ HTNs and ZnCo₂O₄ HTNs have been successfully prepared. The optimal ZnCo₂O₄ HTNs, as a representative substance applied in supercapacitors as the positive electrode, delivers a high specific capacity of 181 C g⁻¹ at a current density of 0.5 A g⁻¹, an excellent rate performance of 75.14% and a superior capacity retention of 97.42% after 10 000 cycles. Furthermore, an asymmetric supercapacitor assembled from ZnCo₂O₄ HTNs and active carbon also shows a stable and ultrahigh cycling stability with 95.38% of its original capacity after 20 000 cycle tests.

Uniform metal oxides hollow tubular nanofibers have been controllably prepared by calcination strategy using electrospun polymer nanofibers as soft templates and zeolitic imidazolate framework nanoparticles as precursors for long-life supercapacitor.     

Advanced binder-free electrodes based on CoMn2O4@Co3O4 core/shell nanostructures for high-performance supercapacitors

Three-dimensional (3D) hierarchical CoMn₂O₄@Co₃O₄ core/shell nanoneedle/nanosheet arrays for high-performance supercapacitors were designed and synthesized on Ni foam by a two-step hydrothermal route. The hybrid nanostructure exhibits much more excellent capacitive behavior compared with either the pristine CoMn₂O₄ nanoneedle arrays alone or Co₃O₄ nanosheets alone. The formation of an interconnected pore hybrid system is quite beneficial for the facile electrolyte penetration and fast electron transport. The CoMn₂O₄@Co₃O₄ electrode can achieve a high specific capacitance of 1627 F g⁻¹ at 1 A g⁻¹ and 1376 F g⁻¹ at 10 A g⁻¹. In addition, an asymmetric supercapacitor (ASC) was assembled by using the CoMn₂O₄@Co₃O₄ core/shell hybrid nanostructure arrays on Ni foam as a positive electrode and activated carbon as a negative electrode in an aqueous 3 M KOH electrolyte. A specific capacitance of 125.8 F g⁻¹ at 1 A g⁻¹ (89.2% retention after 5000 charge/discharge cycles at a current density of 2 A g⁻¹) and a high energy density of 44.8 W h kg⁻¹ was obtained. The results indicate that the obtained unique integrated CoMn₂O₄@Co₃O₄ nanoarchitecture may show great promise as ASC electrodes for potential applications in energy storage.

CoMn₂O₄@Co₃O₄ core/shell arrays on Ni foam exhibit outstanding electrochemical performance for asymmetric supercapacitors with respect to high specific capacitance and high cycling stability.     

MOF-derived Bi2O3@C microrods as negative electrodes for advanced asymmetric supercapacitors

Bismuth oxide (Bi₂O₃) with high specific capacity has emerged as a promising negative electrode material for supercapacitors (SCs). Herein, we propose a facile metal–organic framework (MOF) derived strategy to prepare Bi₂O₃ microrods with a carbon coat (Bi₂O₃@C). They exhibit ultrahigh specific capacity (1378 C g⁻¹ at 0.5 A g⁻¹) and excellent cycling stability (93% retention at 4000 cycles) when acting as negative electrode material for advanced asymmetric SCs. The assembled Bi₂O₃@C//CoNi-LDH asymmetric supercapacitor device exhibits a high energy density of 49 W h kg⁻¹ at a power density of 807 W kg⁻¹. The current Bi-MOF-derived strategy would provide valuable insights to prepare Bi-based inorganic nanomaterials for high-performance energy storage technologies and beyond.

Bi₂O₃ microrods with a carbon coat (Bi₂O₃@C) exhibit ultrahigh specific capacity (1378 C g⁻¹ at 0.5 A g⁻¹) and excellent cycling stability (93% retention at 4000 cycles) as negative electrodes for supercapacitors.     

Disodium citrate-assisted hydrothermal synthesis of V2O5 nanowires for high performance supercapacitors

Orthorhombic vanadium pentoxide (V₂O₅) nanowires with uniform morphology were successfully fabricated via a facile hydrothermal process. The effect of disodium citrate dosage on the crystallinity, morphology and electrochemical properties of the products was analyzed. Experimental results indicate that orthorhombic V₂O₅ nanowires with high crystallinity and diameter of about 20 nm can be obtained at 180 °C for 24 h when the dosage of disodium citrate is 0.236 g. Furthermore, the prepared V₂O₅ nanowires demonstrate a high specific capacitance of 528.2 F g⁻¹ at 0.5 A g⁻¹ and capacitance retention of 85% after 1000 galvanostatic charge/discharge cycles at 1 A g⁻¹ when used as supercapacitors electrode in 0.5 M K₂SO₄.

Orthorhombic vanadium pentoxide (V₂O₅) nanowires with uniform morphology were successfully fabricated via a facile hydrothermal process.     

Controllable synthesis of multi-shelled NiCo2O4 hollow spheres catalytically for the thermal decomposition of ammonium perchlorate

The compatible catalytic structure of NiCo₂O₄ was modified into multi-shelled hollow spheres by one-pot synthesis, followed by heat treatment. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer–Emmet–Teller (BET) and N₂ adsorption–desorption approaches were used for the characterizations of nanoparticles and multi-shelled hollow porous structures and the morphologies and crystal structures of these hollow spheres, respectively. Differential scanning calorimetry (DSC) was adopted for comparing the thermal decomposition performances of ammonium perchlorate (AP) catalyzed by adding different contents of multi-shelled NiCo₂O₄ hollow spheres. Impressively, the experimental results showed that the NiCo₂O₄ hollow spheres exhibited more excellent catalytic activity than NiCo₂O₄ nanoparticles as a result of their large specific surface areas, good adsorption capacity and many active reduction sites. The decomposition temperature of AP with multi-shelled NiCo₂O₄ hollow spheres could be reduced up to 322.3 °C from 416.3 °C. Furthermore, a catalytic mechanism was proposed for the thermal decomposition of AP over multi-shelled NiCo₂O₄ hollow spheres based on electron transfer processes.

Double-shelled NiCo₂O₄ hollow spheres synthesized by a facile hydro-thermal method showed excellent catalytic properties for the thermal decomposition of AP.     

Simple fabrication of Co3O4 nanoparticles on N-doped laser-induced graphene for high-performance supercapacitors

This study demonstrates a simple strategy to fabricate Co₃O₄ on N-doped laser-induced graphene (Co₃O₄-NLIG) based on duplicate laser pyrolysis, enabling the in situ generation of Co₃O₄ nanoparticles and heteroatom doping in laser-induced graphene (LIG). Morphological analyses reveal the uniform distribution of Co₃O₄ nanoparticles on the surface of the LIG structure. The modification of NLIG with Co₃O₄ nanoparticles results in impressive electrochemical performance due to the contributions from electric double-layer capacitance and pseudocapacitance. The optimal Co₃O₄-NLIG is produced at 20 wt% cobalt precursor loading (Co₃O₄-NLIG-20). In a three-electrode setup, this electrode exhibits a specific areal capacitance (C_A) of 216.3 mF cm⁻² at a current density of 0.5 mA cm⁻² in a 1 M KOH electrolyte. When the optimal electrodes are assembled into a solid-state supercapacitor (Co₃O₄-NLIG-SC) using a poly(vinyl alcohol) phosphoric acid (PVA–H₃PO₄) gel electrolyte, a C_A of 17.96 mF cm⁻² is obtained with good cycling stability.

Simultaneous decoration of Co₃O₄ nanoparticles and heteroatom doping on laser-induced graphene based on a duplicate pyrolysis method for supercapacitor applications.     

La2O3-coated Li2ZnTi3O8@C as a high performance anode for lithium-ion batteries

Li₂ZnTi₃O₈C@La₂O₃ (LZTO@C@La₂O₃) coated with composite protective layers is successfully fabricated via a facile solid-state route. The co-coating strategy greatly improves the electrochemical performance of LZTO. 89.8%, 77.2% and 76.7% of the discharge specific capacities for the 2nd cycle can be retained at the 200th cycle at 1, 2 and 3 A g⁻¹, respectively. At 4 and 5 A g⁻¹, 174.3 and 166.1 are still retained for the 100th cycle, respectively. Even at a high temperature of 55 °C, LZTO@C@La₂O₃ still has good cycling performance. The excellent electrochemical performance is due to the stable surface structure between LZTO and the electrolyte, a good conductive network, small particle size, and large specific surface area as well as pore volume.

LZTO@C@La₂O₃ coated with composite protective layers with excellent electrochemical performance has been synthesized using a simple solid-state method.     

High mass loading flower-like MnO2 on NiCo2O4 deposited graphene/nickel foam as high-performance electrodes for asymmetric supercapacitors

The implementation of high mass loading MnO₂ on electrochemical electrodes of supercapacitors is currently challenging due to the poor electrical conductivity and elongated electron/ion transport distance. In this paper, a NiCo₂O₄/MnO₂ heterostructure was built on the surface of three-dimensional graphene/nickel foam (GNF) by a hydrothermal method. The petal structured NiCo₂O₄ loaded on graphene played a wonderful role as a supporting framework, which provided more space for the growth of high mass loading MnO₂ microflowers, thereby increasing the utilization rate of the active material MnO₂. The GNF@NiCo₂O₄/MnO₂ composite was used as a positive electrode and achieved a high areal capacitance of 1630.5 mF cm⁻² at 2 mA cm⁻² in the neutral Na₂SO₄ solution. The asymmetric supercapacitor assembled with the GNF@NiCo₂O₄/MnO₂ positive electrode and activated carbon negative electrode possessed a wide voltage window (2.1 V) and splendid energy density (45.9 Wh kg⁻¹), which was attributed to the satisfactory electroactive area, low resistance, quick mass diffusion and ion transport caused by high mass loading MnO₂.

A NiCo₂O₄/MnO₂ heterostructure with high mass loading MnO₂ microflowers was built on the surface of 3D graphene/nickel foam for the preparation of an asymmetric supercapacitor with splended energy density (45.9 Wh kg⁻¹).     

Synthesis of hollow core–shell ZnFe2O4@C nanospheres with excellent microwave absorption properties

The special hollow core–shell structure and excellent dielectric-magnetic loss synergy of composite materials are two crucial factors that have an important influence on the microwave absorption properties. In this study, hollow ZnFe₂O₄ nanospheres were successfully synthesized by a solvothermal precipitation method firstly; based on this, a C shell precursor phenolic resin was coated on the ZnFe₂O₄ hollow nanospheres'' surface by an in situ oxidative polymerization method, and then ZnFe₂O₄@C was obtained by high-temperature calcination. Samples were characterized by SEM, TEM, XRD, XPS, BET, VSM, VNA. The results show that the maximum reflection loss (RL_max) reaches −50.97 dB at 8.0 GHz, and the effective bandwidth (EAB) of hollow core–shell structure ZnFe₂O₄@C is 3.2 GHz (6.16–9.36 GHz) with a coating thickness of 3.5 mm. This work provides a useful method for the design of lightweight and high-efficiency microwave absorbers.

The hollow core–shell structure ZnFe₂O₄@C in this work has excellent EM absorption performance.     

Enhanced electrochemical performance of nanoplate nickel cobaltite (NiCo2O4) supercapacitor applications

Well-ordered, unique interconnected nanostructured binary metal oxides with lightweight, free-standing, and highly flexible nickel foam substrate electrodes have attracted tremendous research attention for high performance supercapacitor applications owing to the combination of the improved electrical conductivity and highly efficient electron and ion transport channels. In this study, a unique interconnected nanoplate-like nickel cobaltite (NiCo₂O₄) nanostructure was synthesized on highly conductive nickel foam and its use as a binder-free material in energy storage applications was assessed. The nanoplate-like NiCo₂O₄ nanostructure electrode was prepared by a simple chemical bath deposition method under optimized conditions. The NiCo₂O₄ electrode delivered an outstanding specific capacitance of 2791 F g⁻¹ at a current density of 5 A g⁻¹ in a KOH electrolyte in a three-electrode system as well as outstanding cycling stability with 99.1% retention after 3000 cycles at a current density of 7 A g⁻¹. The as-synthesized NiCo₂O₄ electrode had a maximum energy density of 63.8 W h kg⁻¹ and exhibited an outstanding high power density of approximately 654 W h kg⁻¹. This paper reports a simple and cost-effective process for the synthesis of flexible high performance devices that may inspire new ideas for energy storage applications.

Schematic representation of the synthesis of nanoplate-like NiCo₂O₄ structure on nickel foam (NF).     

Engineering NiCo2S4 nanoparticles anchored on carbon nanotubes as superior energy-storage materials for supercapacitors

Fabricating high-capacity electrode materials toward supercapacitors has attracted increasing attention. Here we report a three-dimensional CNTs/NiCo₂S₄ nanocomposite material synthesized successfully by a facile one-step hydrothermal technique. As expected, a CNTs/NiCo₂S₄ electrode shows remarkable capacitive properties with a high specific capacitance of 890 C g⁻¹ at 1 A g⁻¹. It also demonstrates excellent cycle stability with an 83.5% capacitance retention rate after 5000 cycles at 10 A g⁻¹. Importantly, when assembled into a asymmetric supercapacitor, it exhibits a high energy density (43.3 W h kg⁻¹) and power density (800 W kg⁻¹). The exceptional electrochemical capacity is attributed to the structural features, refined grains, and enhanced conductivity. The above results indicate that CNTs/NiCo₂S₄ composite electrode materials have great potential application in energy-storage devices.

A one-step hydrothermal method was used to successfully synthesize NiCo₂S₄ nanocomposites anchored on carbon nanotubes as excellent energy storage materials for supercapacitors.     

MnO2/ZnCo2O4 with binder-free arrays on nickel foam loaded with graphene as a high performance electrode for advanced asymmetric supercapacitors

ZnCo₂O₄ nanosheets were successfully arrayed on a Ni foam surface with graphene using a hydrothermal method followed by annealing treatment; then MnO₂ nanoparticles were electrodeposited on the ZnCo₂O₄ nanosheets to obtain a synthesized composite binder-free electrode named MnO₂/ZnCo₂O₄/graphene/Ni foam (denoted as MnO₂/ZnCo₂O₄/G/NF). After testing the binder-free composite electrode of MnO₂/ZnCo₂O₄/G/NF via cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy testing, we found that it exhibited ultrahigh electrochemical properties, with a high specific areal capacitance of 3405.21 F g⁻¹ under a current density of 2 A g⁻¹, and wonderful cycling stability, with 91.2% retention after 5000 cycles. Moreover, an asymmetric supercapacitor (ASC) based on MnO₂/ZnCo₂O₄/G/NF//G/NF was successfully designed. When tested, the as-designed ASC can achieve a maximum energy density of 46.85 W h kg⁻¹ at a power density of 166.67 W kg⁻¹. Finally, the ASC we assembled can power a commercial red LED lamp successfully for more than 5 min, which proves its practicability. All these impressive performances indicate that the MnO₂/ZnCo₂O₄/graphene composite material is an outstanding electrode material for electrochemical capacitors.

Schematic illustration of formation process of MnO₂/ZnCo₂O₄/G/NF composite electrode.     

Correction: Enhanced electrochemical performance of nanoplate nickel cobaltite (NiCo2O4) supercapacitor applications

Correction for ‘Enhanced electrochemical performance of nanoplate nickel cobaltite (NiCo₂O₄) supercapacitor applications’ by Anil Kumar Yedluri et al., RSC Adv., 2019, 9, 1115–1122.

Attribution to a funding body (BK 21 PLUS) in the published article was incorrect (arising from delays), and the corrected Acknowledgements section should be as follows:This research was supported by the Basic Research Laboratory through the National Research Foundations of Korea funded by the Ministry of Science, ICT and Future Planning (NRF-2015R1A4A1041584).The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Low temperature scalable synthetic approach enabling high bifunctional electrocatalytic performance of NiCo2S4 and CuCo2S4 thiospinels

Ternary metal sulfides are currently in the spotlight as promising electroactive materials for high-performance energy storage and/or conversion technologies. Extensive research on metal sulfides has indicated that, amongst other factors, the electrochemical properties of the materials are strongly influenced by the synthetic protocol employed. Herein, we report the electrochemical performance of uncapped NiCo₂S₄ and CuCo₂S₄ ternary systems prepared via solventless thermolysis of the respective metal ethyl xanthate precursors at 200 and 300 °C. The structural, morphological and compositional properties of the synthesized nanoparticles were examined by powder X-ray diffraction (p-XRD), transmission electron microscopy (TEM), high-resolution TEM, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) techniques. Electrochemical studies indicate that NiCo₂S₄ nanoparticles synthesized at 300 °C exhibit superior energy storage characteristics with a high specific capacitance of ca. 2650 F g⁻¹ at 1 mV s⁻¹, as compared to CuCo₂S₄ nanoparticles, which showcased a specific capacitance of ca. 1700 F g⁻¹ at the same scan rate. At a current density of 0.5 A g⁻¹, NiCo₂S₄ and CuCo₂S₄ nanoparticles displayed specific capacitances of 1201 and 475 F g⁻¹, respectively. In contrast, CuCo₂S₄ nanoparticles presented a higher electrocatalytic activity with low overpotentials of 269 mV for oxygen evolution reaction (OER), and 224 mV for the hydrogen evolution reaction (HER), at 10 mA cm⁻². The stability of the catalysts was examined for 2000 cycles in which a negligible change in both OER and HER activities was observed.

A scalable solventless approach is employed to prepare NiCo₂S₄ and CuCo₂S₄ with bare surface for enhanced supercapacitance and water splitting. The particles exhibit good energy storage and electrocatalytic activity as well as stability.