Asymmetric Supercapacitors Based on ZnCo2O4 Nanohexagons and Orange Peel Derived Activated Carbon Electrodes.

Herein, the performance of asymmetric supercapacitors (ASC) fabricated using ZnCo2O4 (ZCO) nano-hexagons and orange peel-derived activated carbon (OPAC) as electrodes was studied. ZCO was prepared by a double hydroxide method and OPAC was prepared from orange peel followed by KOH activation. For ZCO, the calcination temperature was determined using TGA analysis. The XRD showed the presence of a cubic spinel structure. The chemical structure was analyzed using XPS, FTIR, and Raman spectroscopy respectively. For OPAC, the presence of an amorphous nature was inferred; FTIR and Raman studies indicate the presence of functional groups and defect structure in the material. The presence of ZCO nano-hexagons was observed from SEM and TEM respectively. For OPAC, an interconnected pore structure was observed from the SEM image. The specific capacitance for ZCO and OPAC was found to be 194 F.g-1 and 159 F.g-1 at a current density of 0.25 A.g-1. Further, an ASC was fabricated using ZCO as a positive and OPAC as a negative electrode in 2M KOH-soaked separator. A cell voltage of 1.2 V was achieved and the specific capacitance was calculated to be 64 F.g-1 at 0.25 A.g-1. Further, the cyclic stability and the changes at the electrode/electrolyte interface were studied.

A Binary Salt Mixture LiCl-LiOH for Thermal Energy Storage.

For thermal energy storage, the most promising method that has been considered is latent heat storage associated with molten salt mixtures as phase-change material (PCM). The binary salt mixture lithium chloride-lithium hydroxide (LiCl-LiOH) with a specific composition can store thermal energy. However, to the best of our knowledge, there is no information on their thermal stability in previous literature. The key objectives of this article were to investigate the thermophysical properties, thermal repeatability, and thermal decomposition behavior of the chosen binary salt mixture. FactSage software was used to determine the composition of the binary salt mixture. Thermophysical properties were investigated with a simultaneous thermal analyzer (STA). The thermal results show that the binary salt 32 mol% LiCl-68 mol% LiOH melts within the range of 269 °C to 292 °C and its heat of fusion is 379 J/g. Thermal repeatability was tested with a thermogravimetric analyzer (TGA) for 30 heating and cooling cycles, which resulted in little change to the melting temperature and heat of fusion. Thermal decomposition analysis indicated negligible weight loss until 500 °C and showed good thermal stability. Chemical and structural instability was verified by X-ray diffraction (XRD) by analysing the binary salt system before and after thermal treatment. A minor peak corresponding to lithium oxide was observed in the sample decomposed at 700 °C which resulted from the decomposition of LiOH at high temperature. The morphology and elemental distribution examinations of the binary salt mixture were carried out via scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). X-ray photoelectron spectroscopy was conducted for surface analysis, and their elemental composition verified the chemical stability of the binary salt mixture. Overall, the results confirmed that the binary salt mixture is a potential candidate to be used as thermal energy storage material in energy storage applications of up to 500 °C.

Repurposing N-Doped Grape Marc for the Fabrication of Supercapacitors with Theoretical and Machine Learning Models.

Porous carbon derived from grape marc (GM) was synthesized via carbonization and chemical activation processes. Extrinsic nitrogen (N)-dopant in GM, activated by KOH, could render its potential use in supercapacitors effective. The effects of chemical activators such as potassium hydroxide (KOH) and zinc chloride (ZnCl2) were studied to compare their activating power toward the development of pore-forming mechanisms in a carbon electrode, making them beneficial for energy storage. GM carbon impregnated with KOH for activation (KAC), along with urea as the N-dopant (KACurea), exhibited better morphology, hierarchical pore structure, and larger surface area (1356 m2 g-1) than the GM carbon activated by ZnCl2 (ZnAC). Moreover, density functional theory (DFT) investigations showed that the presence of N-dopant on a graphite surface enhances the chemisorption of O adsorbates due to the enhanced charge-transfer mechanism. KACurea was tested in three aqueous electrolytes with different ions (LiOH, NaOH, and NaClO4), which delivered higher specific capacitance, with the NaOH electrolyte exhibiting 139 F g-1 at a 2 mA current rate. The NaOH with the alkaline cation Na+ offered the best capacitance among the electrolytes studied. A multilayer perceptron (MLP) model was employed to describe the effects of synthesis conditions and physicochemical and electrochemical parameters to predict the capacitance and power outputs. The proposed MLP showed higher accuracy, with an R2 of 0.98 for capacitance prediction.

Activation-Induced Surface Modulation of Biowaste-Derived Hierarchical Porous Carbon for Supercapacitors.

Wheat straw-derived carbon from the Wheatbelt region in Western Australia was subjected to chemical activation in an electrolyte containing either acid or base treatment. The findings showed an increase in electron/hole mobility towards the interfaces due to the presence of different surface functional groups such as C-SOx -C and S=C in the carbon framework for acid activation. Likewise, the galvanostatic capacitance measured at a current density of 2 mA cm-2 in a three-electrode configuration for acid-activated wheat straw exhibited 162 F g-1 , while that for base-activated wheat straw exhibited 106 F g-1 . An increase of 34.5 % more capacitance was achieved for acid-treated wheat straw. This improvement is attributed to the synergistic effects between surface functional groups and electrolyte ions, as well as the electronic structure of the porous electrode.

Effect of the Anionic Counterpart: Molybdate vs. Tungstate in Energy Storage for Pseudo-Capacitor Applications.

Nickel-based bimetallic oxides (BMOs) have shown significant potential in battery-type electrodes for pseudo-capacitors given their ability to facilitate redox reactions. In this work, two bimetallic oxides, NiMoO4 and NiWO4, were synthesized using a wet chemical route. The structure and electrochemical properties of the pseudo-capacitor cathode materials were characterized. NiMoO4 showed superior charge storage performance in comparison to NiWO4, exhibiting a discharge capacitance of 124 and 77 F.g-1, respectively. NiMoO4, moreover, demonstrates better capacity retention after 1000 cycles with 87.14% compared to 82.22% for NiWO4. The lower electrochemical performance of the latter was identified to result from the redox behavior during cycling. NiWO4 reacts in the alkaline solution and forms a passivation layer composed of WO3 on the electrode, while in contrast, the redox behavior of NiMoO4 is fully reversible.

Perspectives on Nickel Hydroxide Electrodes Suitable for Rechargeable Batteries: Electrolytic vs. Chemical Synthesis Routes.

A significant amount of work on electrochemical energy storage focuses mainly on current lithium-ion systems with the key markets being portable and transportation applications. There is a great demand for storing higher capacity (mAh/g) and energy density (Wh/kg) of the electrode material for electronic and vehicle applications. However, for stationary applications, where weight is not as critical, nickel-metal hydride (Mi-MH) technologies can be considered with tolerance to deep discharge conditions. Nickel hydroxide has gained importance as it is used as the positive electrode in nickel-metal hydride and other rechargeable batteries such as Ni-Fe and Ni-Cd systems. Nickel hydroxide is manufactured industrially by chemical methods under controlled conditions. However, the electrochemical route is relatively better than the chemical counterpart. In the electrochemical route, a well-regulated OH- is generated at the cathode forming nickel hydroxide (Ni(OH)2) through controlling and optimizing the current density. It produces nickel hydroxide of better purity with an appropriate particle size, well-oriented morphology, structure, et cetera, and this approach is found to be environmentally friendly. The structures of the nickel hydroxide and its production technologies are presented. The mechanisms of product formation in both chemical and electrochemical preparation of nickel hydroxide have been presented along with the feasibility of producing pure nickel hydroxide in this review. An advanced Ni(OH)2-polymer embedded electrode has been reported in the literature but may not be suitable for scalable electrochemical methods. To the best of our knowledge, no such insights on the Ni(OH)2 synthesis route for battery applications has been presented in the literature.

Calcined chicken eggshell electrode for battery and supercapacitor applications.

Biowaste eggshell can be used as a cathode while in its calcined form and it is found to be suitable as an anode in an electrochemical cell. This not only enables energy to be stored reversibly but also achieves waste management and sustainability goals by redirecting material away from landfill. Biowaste eggshell comprises 94% calcium carbonate (CaCO3; calcite), an attractive divalent ion source as a viable option for energy storage. X-ray diffraction and electron microscopy coupled with energy dispersive analyses of the calcined (thermally decomposed) biowaste eggshell show that CaO has been formed and the reaction is topotactic. Field emission scanning electron microscopy (FESEM) images of the textural relationship show that the thermal decomposition of calcite resulted in a change in morphology. High-resolution XPS spectra of the C 1s core level from the CaCO3 and CaO shows that there is a chemical difference in the carbon environments and the total atomic fraction of Ca for each sample with that of carbonate and oxygen varies. In a three-electrode configuration, a working electrode of CaCO3 is found to be electrochemically active in the positive region, whereas a CaO electrode is active in the negative region. This indicates the potential use of eggshell-derived materials for both cathode and anode. Both the electrodes exhibited a quasi-box-shaped potentiostatic curve implying a capacitor-type behaviour. The CaCO3 cathode possesses a modest discharge capacitance of 10 F g-1 but the CaO anode showed excellent capacitance value of 47.5 F g-1. The CaO electrode in both positive and negative regions, at a current density of 0.15 A g-1 exhibited 55 F g-1 with a retention of nearly 100% after 1000 cycles. At a very low sweep rate of 0.5 mV s-1, the CaO electrode showed typical redox-type behaviour with well-defined peaks illustrating battery-type behaviour. The outcome of the calcite/CaO transformation, exhibiting technological importance for energy storage applications, may help to re-evaluate biowaste before throwing it away. The current work explores the viability of eggshell derived materials as a cathode/anode for use in batteries and capacitors.

Phase evolution in calcium molybdate nanoparticles as a function of synthesis temperature and its electrochemical effect on energy storage.

The design of a suitable electrode is an essential and fundamental research challenge in the field of electrochemical energy storage because the electronic structures and morphologies determine the surface redox reactions. Calcium molybdate (CaMoO4) was synthesized by a combustion route at 300 °C and 500 °C. We describe new findings on the behaviour of CaMoO4 and evaluate the influence of crystallinity on energy storage performance. A wide range of characterization techniques was used to obtain detailed information about the physical and morphological characteristics of CaMoO4. The characterization results enable the phase evolution as a function of the electrode synthesis temperature to be understood. The crystallinity of the materials was found to increase with increasing temperature but with no second phases observed. Molecular dynamics simulation of electronic structures correlated well with the experimental findings. These results show that to enable faster energy storage and release for a given surface area, amorphous CaMoO4 is required, while larger energy storage can be obtained by using crystalline CaMoO4. CaMoO4 has been evaluated as a cathode material in classical lithium-ion batteries recently. However, determining the surface properties in a sodium-ion system experimentally, combined with computational modelling to understand the results has not been reported. The superior electrochemical properties of crystalline CaMoO4 are attributed to its morphology providing enhanced Na+ ion diffusivity and electron transport. However, the presence of carbon in amorphous CaMoO4 resulted in excellent rate capability, suitable for supercapacitor applications.

Facile synthesis of a nanoporous sea sponge architecture in a binary metal oxide.

A novel galvanostatic electrochemical technique has been employed to synthesize a cobalt-nickel mixed oxide, a binary metal oxide, via a two-step route involving electrodeposition followed by calcination. A diaphragm cell was used for the electro-deposition of the binary hydroxide at room temperature in which the electrolyte comprises a nitrate and/or sulphate bath of the corresponding metal ions at pH 4. The electrodeposited product was calcined at 300 °C to obtain the desired oxide material. The formation of the binary metal oxide has been confirmed by X-ray diffraction analysis. The scanning electron microscopy images associated with energy dispersive analysis (EDS) suggest the formation of a nanoporous sea sponge architecture consisting of an interconnected array of nanosheets aligned perpendicular to each other. The elemental mapping analysis of the binary oxide illustrated the uniformity in the distribution of Co and Ni in the composite material. The TEM image shows that binary oxides are nanocrystalline materials. A nitrogen adsorption-desorption study supports the pore size distribution behaviour of the synthesized material. The hybrid capacitor based on the binary metal oxide cathode and activated carbon anode displayed a capacitive behaviour with a capacitance of 76 F g-1 at a current rate of 2 mA with 98% efficiency after 1000 cycles. Due to the unique interconnected porous network and the role of binary cations, Co-Ni oxide exhibits superior electrochemical behaviour. The synthesis of binary oxides forming various morphologies, such as hexagonal, flower-shape, and sea sponge has been discussed.

Bio-waste chicken eggshells to store energy.

Bio-waste in the form of chicken eggshells, which contain high amounts of calcium carbonate (CaCO3), is used to store energy. The fine eggshell powders are used as an electrode against a metallic lithium anode in a non-aqueous electrolyte. The initial discharge capacitance of the eggshell system was found to be 232 F g-1, while the reversible capacitance was 120 F g-1. Thereon, the cell maintained an excellent capacitance retention of 92% over 1000 cycles. The electrochemical performance obtained is comparable to that of commercially available classical activated carbon (AC) material. CaCO3 showed a non-faradaic behaviour and the shape of the electrochemical curves resembles that of the AC electrode. The preliminary findings suggest that CaCO3 from eggshells can be used as the electrode in Li-ion capacitors to store and release charges effectively over a wide electrochemical stability window of 4 V. Using chicken eggshells in this manner not only reduces the amount of bio-waste, but also adds considerable value. A detailed understanding of the electrochemical and physical behaviour of the material is needed in order to improve its performance and to enable its widespread use.

New insights into the electrochemistry of magnesium molybdate hierarchical architectures for high performance sodium devices.

Magnesium molybdate (MgMoO4), which possesses synergistic features combining both hierarchical plate-like nanomaterials and porous architectures, has been successfully synthesized through a facile combustion synthesis at a low temperature. The hierarchical architecture is characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), scanning transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analyses. The as-obtained MgMoO4 nanoplates showed a porous structure with a pore-size distribution ranging from 50 to 70 nm. This porosity provides an electron transport pathway and enhanced surface reaction kinetics. The binding energies measured for Mg 2p, Mo 3d, 3p and O 1s are consistent with the literature, and with the metal ions being present as M(ii) and M(vi) states, respectively. This indicates that the oxidation states of the metal cations are as expected. The electrochemical behaviour of MgMoO4 was investigated using aqueous (NaOH) and non-aqueous solvents (NaClO4 in EC : DMC : FEC) for supercapacitor and battery applications. The sodium-ion capacitor involves ion absorption and insertion into the MgMoO4 electrodes resulting in superior power and energy densities. However, the cycling stability was found to be stable only for an aqueous system. The formation of a solid electrolyte surface layer restricted the reversible capacity of the MgMoO4 in the sodium-battery. Nevertheless, it does offer some promise as an anode material for storing energy with high rate performance and excellent capacity retention. Detailed comparative analyses of various electrolytes in storage devices such as hybrid sodium-ion capacitors and sodium-ion batteries are vital for the integration of hierarchical structured materials into practical applications. The reaction mechanisms are postulated.

Influence of Synthesis Temperature on the Growth and Surface Morphology of Co3O4 Nanocubes for Supercapacitor Applications.

A facile hydrothermal route to control the crystal growth on the synthesis of Co3O4 nanostructures with cube-like morphologies has been reported and tested its suitability for supercapacitor applications. The chemical composition and morphologies of the as-prepared Co3O4 nanoparticles were extensively characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Varying the temperature caused considerable changes in the morphology, the electrochemical performance increased with rising temperature, and the redox reactions become more reversible. The results showed that the Co3O4 synthesized at a higher temperature (180 °C) demonstrated a high specific capacitance of 833 F/g. This is attributed to the optimal temperature and the controlled growth of nanocubes.

Rescaling metal molybdate nanostructures with biopolymer for energy storage having high capacitance with robust cycle stability.

Hybrid capacitors can replace or complement batteries, while storing energy through ion adsorption and fast surface redox reactions. There is a growing demand in developing nanostructured materials as electrodes for hybrid systems that can enhance the specific capacitance by ion desolvation in the nanopores. Here, we demonstrate that rescaling the pore diameter with the aid of biopolymer at an optimal level during the synthesis of metal molybdate leads to high capacitance 124 F g-1 giving robust capacitance retention of 80% over 2000 cycles for a constructed device (activated carbon vs. metal molybdate). The presence of biopolymer (l-glutamic acid) in the metal molybdate acts as a complexing agent of the metal ion while enhancing the mass transport and hence it's improved electrochemical performance. However, XPS and other elemental analyses illustrated no evidence for N doping but traces of other surface functional groups (i.e. C and O) could be present on the molybdate surface. The biopolymer synthetic approach has the advantage of yielding nanostructured material with a relatively narrow pore size distribution controlled by l-glutamic acid. This study will provide a generic route to rescale other metal molybdate, phosphate or oxide counterparts and be an added value to the database.

Synthesis, structural and electrochemical properties of sodium nickel phosphate for energy storage devices.

Electrochemical energy production and storage at large scale and low cost, is a critical bottleneck in renewable energy systems. Oxides and lithium transition metal phosphates have been researched for over two decades and many technologies based on them exist. Much less work has been done investigating the use of sodium phosphates for energy storage. In this work, the synthesis of sodium nickel phosphate at different temperatures is performed and its performance evaluated for supercapacitor applications. The electronic properties of polycrystalline NaNiPO4 polymorphs, triphylite and maricite, t- and m-NaNiPO4 are calculated by means of first-principle calculations based on spin-polarized Density Functional Theory (DFT). The structure and morphology of the polymorphs were characterized and validated experimentally and it is shown that the sodium nickel phosphate (NaNiPO4) exists in two different forms (triphylite and maricite), depending on the synthetic temperature (300-550 °C). The as-prepared and triphylite forms of NaNiPO4vs. activated carbon in 2 M NaOH exhibit the maximum specific capacitance of 125 F g(-1) and 85 F g(-1) respectively, at 1 A g(-1); both having excellent cycling stability with retention of 99% capacity up to 2000 cycles. The maricite form showed 70 F g(-1) with a significant drop in capacity after just 50 cycles. These results reveal that the synthesized triphylite showed a high performance energy density of 44 Wh kg(-1) which is attributed to the hierarchical structure of the porous NaNiPO4 nanosheets. At a higher temperature (>400 °C) the maricite form of NaNiPO4 possesses a nanoplate-like (coarse and blocky) structure with a large skewing at the intermediate frequency that is not tolerant of cycling. Computed results for the sodium nickel phosphate polymorphs and the electrochemical experimental results are in good agreement.

Probing the electrochemical properties of biopolymer modified EMD nanoflakes through electrodeposition for high performance alkaline batteries.

In the present work, a novel biopolymer approach has been made to electrodeposit manganese dioxide from manganese sulphate in a sulphuric acid bath containing chitosan in the absence and presence of glutaraldehyde as a cross-linking agent. Galvanostatically synthesised electrolytic manganese dioxide (EMD) nanoflakes were used as electrode materials and their electrochemical properties with the influence of biopolymer chitosan were systematically characterized. The structural determination, surface morphology and porosity of nanostructured EMD were evaluated using X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy and nitrogen adsorption-desorption techniques. The results obtained were compared with that of blank EMD (polymer free). The results indicated that the EMD having chitosan cross-linked with glutaraldehyde possesses a reduced particle size and more porous structure than the blank and EMDs synthesized in the presence of chitosan but without glutaraldehyde. The results revealed that chitosan was unable to play any significant role on its own but chitosan in the presence of glutaraldehyde forms a cross-linking structure, which in turn influences the nucleation and growth of the EMDs during electrodeposition. EMDs obtained in the presence of chitosan (1 g dm(-3)) and glutaraldehyde (1% glutaraldehyde) exhibited a reversible and better discharge capacity upon cycling than the blank which showed its typical capacity fading behaviour with cycling. In addition, EMD synthesized in the presence of 1 g dm(-3) chitosan and 2% glutaraldehyde exhibited a superior electrochemical performance than the blank and lower amounts (1%; 1.5%) of glutaraldehyde, showing a stable discharge capacity of 60 mA h g(-1) recorded up to 40 cycles in alkaline KOH electrolyte for a Zn-MnO2 system. Our results demonstrate the potential of using polymer modified EMDs as a new generation of alkaline battery materials. The XPS data show that a surface functional moiety arising from the cross-linked chitosan enhances the electrochemical properties of the Zn-MnO2 system.

Tuning the Redox Properties of the Nanostructured CoMoO4 Electrode: Effects of Surfactant Content and Synthesis Temperature.

A systematic study was performed to examine the effects of surfactant content and synthesis temperature on the morphologies and the redox properties of cobalt molybdate (CoMoO4 ). The results revealed that varying the concentration of surfactant (F127) varies the morphology from nanorods to nanospheres and nanoneedles. A concentration of metal-to-surfactant ratio of 1:1 outperformed that of 1:0.5 and 1:2 ratios in specific capacitance, energy density and cycling stability. The surfactant at the optimised ratio significantly influenced the morphology and particle size of the CoMoO4 material and acted as a template, whereas increasing the synthetic temperature did not contribute much to the energy storage. An asymmetric supercapacitor was fabricated based on CoMoO4 as the positive electrode and activated carbon as the negative electrode in 2 m NaOH electrolyte. The CoMoO4 material synthesised at 300 °C in the presence of F127 (1:1) showed a specific capacitance of 79 F g-1 and an energy density of 21 W h kg-1 when tested as a hybrid device. This suggests that the redox activity and its storage capability depend on the surfactant content as well as its self-assembly behaviour. CoMoO4 showed excellent cycling stability retaining over 75 % of its initial capacitance after 2000 cycles, which makes it a very promising candidate for large-scale energy-storage applications.

Co/Mo bimetallic addition to electrolytic manganese dioxide for oxygen generation in acid medium.

An efficient electrocatalyst comprising inexpensive and earth-abundant materials for the oxygen evolution reaction (OER) is crucial for the development of water electrolysis. In this work, in-situ addition of cobalt/molybdenum ions to the electrolytic manganese dioxide has been shown to be beneficial for the OER in acid solution as its overpotential performed better (305 mV) than that of the commercial DSA(®) (341 mV) at 100 mA cm(-2). The OER was investigated at ambient temperature in 2 M H2SO4 solution on the modified EMD (MnMoCoO) electrodes. The energy efficiency of the MnMoCoO electrodes improved significantly with the amount of Co in the plating solution. For the electrodeposited catalysts, physico-chemical and electrochemical measurements were conducted including static overpotentials. The better performance of the modified EMD was attributed to an improved charge transfer resistance (Rct; 0.290 Ω cm(2)), average roughness factor (rf; 429) and decrease in water content in the electrodeposited catalysts. The kinetic parameters obtained on MnMoCoO catalysts were compared and discussed according to the cobalt concentration.

Electrodeposition of Pluronic F127 assisted rod-like EMD/carbon arrays for efficient energy storage.

In the traditional Duracell battery, the results obtained to date remain marginal in terms of cyclability. The development of the existing Zn-MnO2 with superior electrochemical performance for use in alkaline rechargeable batteries is reported. Electrolytic manganese dioxide (EMD) was synthesized from a conventional manganese sulphate bath but having a unique non-ionic surfactant (Pluronic F127), and activated carbon, in an electrolytic cell. The surface areas and morphologies of the as-prepared EMDs were influenced by the presence of these novel additives in the solution while the X-ray data revealed that there was no noticeable change in the crystal orientations thus all the EMDs were structurally similar. The synergistic effect of the optimal ratio of surfactant to carbon powder produced rod-like arrays exhibiting a larger surface area, which facilitates ion transport for better energy storage. It is interesting to note that EMD deposited in the presence of F127 showed better cyclability whereas in the presence of carbon, although it showed better storage capability, it was endowed with poor efficiency when compared with the surfactant added sample, nevertheless the results are better than the existing Zn-MnO2 technology (additive free EMD). Therefore, both the surfactant (50 mg dm(-3)) and the activated carbon (5 g dm(-3)) have been added together in the bath and the resultant EMD exhibits a high specific capacity and an excellent cycling stability. Moreover, the presence of surfactant and activated carbon improved the discharge capacity and its retention thus making this alkaline technology feasible for storing renewable energy for future use. The synergistic effect and the mechanism involved have been discussed.

Fabrication of ultrathin CoMoO4 nanosheets modified with chitosan and their improved performance in energy storage device.

Ultrathin nanosheet-assembled cobalt molybdate (CoMoO4) with a mesoporous morphology was synthesized by a urea-assisted solution combustion route at a temperature of 400 °C. The as-prepared CoMoO4 was modified using chitosan cross-linked with glutaraldehyde (glu) and employed as a cathode material in an aqueous hybrid capacitor. The physical and electrochemical behaviour of CoMoO4 modified with chitosan and the as-prepared (chitosan free) CoMoO4 has been compared and discussed. The modified CoMoO4 exhibited excellent electrochemical performance with a specific capacitance of 135 F g(-1) at 0.6 A g(-1) and an energy density of 31 W h kg(-1). It also exhibited good cycling stability with high coulombic efficiency over 2000 cycles retaining a specific capacitance of 81 F g(-1) at 3 A g(-1), comparatively much better than that of nanostructured chitosan free CoMoO4 which yielded 17 F g(-1). The results indicated that chitosan gel strongly adheres to the molybdate moiety of CoMoO4 and increases the capacitance four-fold compared to a chitosan free material. The modified CoMoO4 electrode shows potential for high performance, and is an environmentally friendly and low-cost energy storage device.