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The GCD curves under different current densities of 1, 1.5, 2, 3, 5, and 8 A g −1 of samples a CMO-1, b CMO-4, c CMO-8, d CMO-12, and e CMO-24 in the potential window ranged from − 0.2 to + 0.58 V. f The specific capacitance of samples calculated by GCD results
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The single-phase CoMoO4 was prepared via a facile hydrothermal method coupled with calcination treatment at 400 °C. The structures, morphologies, and electrochemical properties of samples with different hydrothermal reaction times were investigated. The microsphere structure, which consisted of nanoflakes, was observed in samples. The specific capa...
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... time is 12 h) shows an excellent spe- cific capacitance. [45]. Such an improved electrochemical property can be confirmed by the following galvanostatic charge- discharge tests. The GCD tests of samples were per- formed at different current densities of 1, 1.5, 2, 3, 5, and 8 A g −1 in 2 M KOH electrolyte, and the results are shown in Fig. 6a-e. The nonlinear GCD curves could be attributed by the redox reaction [46], and this is consistent with the CV curves. As shown in these curves, the discharge time of CMO-12 is significantly longer than other samples, indicating a much higher specific capacitance in CMO-12. This could be con- firmed furtherly by the following ...
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... C (F g −1 ) is the specific capacitance, I (A) is the discharge current, Δt (s) is refer to discharge times, m (g) is the mass of active material loading on the electrode surface, and ΔV (V) is the applied potential window [6,8,26]. Figure 6f shows the calculated specific capacitance of samples at different current densities. ...
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... high current density, there is only part of the total available reaction sites be- cause the electrolyte ions suffer from low diffusion, which lead to an incomplete insertion reaction and a low specific capacitance [19,45]. From Fig. 6f, we can see that the CMO-12 has the highest specific capaci- tance, which are 384, 337, 307, 269, 229, and 172 F g −1 at the current density of 1, 1.5, 2, 3, 5, and 8 A g −1 , respectively. The specific capacitance of CMO-12 shows a good rate capability. ...
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Citations
... The observed redox peak is caused by the charge transfer kinetics of Co 2+/ Co 3+ associated with OH − ions. The redox reaction of is listed as follows [26]: ...
Flexible solid-state supercapacitors offer intrinsic fast charging–discharging properties, facilitating the fulfillment of requirements for lightweight and multifunctional wearable electronics. In the present study, PVP/PVA/X wt% of CoMoO4 polymer nanocomposites (PNCs) have been prepared by a solution casting technique. The PNCs were characterized by different analytical tools such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Scanning electron microscopy (SEM). A solid-state asymmetric supercapacitor device (ASC) is fabricated by using PVP/PVA/X wt% CoMoO4 PNCs as the positive electrode and activated carbon as the negative electrode. Electrochemical characterization of the prepared ASCs devices was performed by cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance spectral (EIS) analyses. The ASCs device attains a window potential of 1.5 V at chronoamperometry. At 1 A g⁻¹ current density, PVP/PVA/1 wt% CoMoO4 ASCs device achieved specific capacitances of 11.35 F g⁻¹. The ASCs device exhibited an outstanding cycle life with a capacitance retention of 74% after 10,000 charge/discharge cycles, a maximum energy density of 3.54 Wh kg⁻¹, and a power density of 734 W kg⁻¹. The EIS shows a small semicircle before and after GCD 10,000 cycles, which indicates the electrolyte has high conductivity and low internal resistance in the ASC device. It also indicates that the PVP/PVA/1 wt% CoMoO4 PNCs have potential applications as cathodic electrode for energy storage devices.
... Also, a few macropores were noted in the samples. The large specific surface area and abundant mesoporous structure could boost the contact area between the electrode and electrolyte, leading to creating enough active sites for redox reactions as well as great transport of electrons/ions [51,52]. Therefore, the superior BET surface area and mesopore structure of CM-N might reveal better electrochemical performance than other samples. ...
... The electrochemical measurements were conducted to analyze the pseudocapacitive properties of CoMoO 4 electrodes (Fig. 8) The CV graphs of the various morphologies of CoMoO 4 electrodes under the different scan rates (20 mV/s, 40 mV/s, 60 mV/s, 80 mV/s, and 100 mV/ s) in 3 M KOH electrolyte with potential ranges from 0 to 0.6 V (vs. Ag/ AgCl) are presented in Fig. 8a- [51]. ...
... It also suggests the enhancement of the irreversible degree and the quasi-reversible reaction with the increment of scan rate. These may be associated with the internal resistance of the CoMoO 4 electrodes and the polarization in a high scan rate [51]. The integral area of CM-N was evidently higher than CM-B, CM-R, and CM-U (CM-N > CM-R > CM-B > CM-U), suggesting larger specific capacitance and better electrochemical performance (Fig. 8a-d and S8). ...
... Binary transition metal oxides (M x-M 2x O 4x , BTMOs) show high electric conductivity, mobility of ions, ultrahigh energy density, wider potential window and exhibit excellent electrochemical performance than conventional M x O x [16,17]. Nowadays, BTMOs such as Ni x Co 2x O 4x [18], Mn x-Co 2x O 4x [19], Zn x Co 2x O 4x [20] , Co x Mo x O 4x [21] and Mg x Co 2x O 4x [22] make special place in the electrochemical sector due to their unique properties such as high theoretical Csp, inexpensiveness, non-polluting nature and stable structure [23][24][25][26][27]. Thus, BTMOs are considered strong candidates for SCs. ...
Supercapacitors and many other high-performance energy storage technologies have been the subject of intense research due to the rapidly growing interest in wearable electronics and electric cars. Self-assembled porous networks like nano-micro clusters of zinc cobaltite (ZnCo2O4, ZCO) have been synthesized using a simple, one-step and inexpensive reflux method for supercapacitor application. The effect of ionic surfactant (trisodium citrate, TSC) on the growth of the ZCO nanoparticles was studied. The structural, morphological, and electrochemical performance of the TSC-assisted ZCO electrodes were thoroughly tested. XRD studies reveal the spinel simple cubic (Fd3m) structure of ZCO clusters. RAMAN shows five active phonon (F2g, F2g, F2g, Eg, A1g) modes present in synthesized samples. BET provides a maximum 49.49 m²/g specific surface area for an optimistic sample. The porous structured TSC-assisted ZCO electrode enables electrochemical specific capacitance of 629 F/g (61.2 mAh/g) at a current density of 1 mA/cm² with a specific energy of 38.55 Wh/kg and power delivery of 450 W/kg. Furthermore, to check the practical suitability of the electrode, cyclic stability was studied, showing retention of 84.20% specific capacitance after 5000 consecutive CV cycles at 50 mV/s. Hence, the results indicated that the cost-effective and eco-friendly method of preparing nano-micro clusters like binary transition metal oxides provides a new direction for future research.
... The W-CoMoO 4 shows enhanced electrocatalytic OER performance due to the enhancement of the active site and the creation of oxygen vacancies after introducing foreign metal ions. Li et al. (2018), designed a manganese-doped nickel molybdate-based electrode for supercapacitor application. Due to the different charges of the metal ions, a synergistic is created, which facilitates ion transport and exhibits higher specific capacitance with good cyclic stability. ...
Ronidazole is a veterinary antibiotic drug that was used in animal husbandry as a feed promoter. Meanwhile, improper disposals and illegal usage of pharmaceutical drugs were heavily contaminating the water resources. Metal ion doping/substitution is an effective strategy to modify the crystal phase, morphology, and electrocatalytic activity of the material. Herein, Ni2+ doped cobalt molybdate micro rods (NCMO MRs) were prepared for the electrochemical sensor application of ronidazole. The catalyst was prepared by the reflux method followed by calcination at 500 °C. The prepared catalyst was confirmed by various spectroscopic and microscopic analyses. XRD and Raman spectroscopy demonstrated that the phase transition was achieved from β-CoMoO4 to α-CoMoO4 by the Ni2+ doping. SEM analysis showed micro rods of cobalt molybdate (CMO) were self-assembled and form an urchin-like structure during Ni2+ doping and the average diameter of micro rods is ±50 nm. The electrocatalytic activity of catalysts was analyzed by the CV technique. The NCMO MRs/GCE exhibits the highest current response than the undoped CMO. The electron transfer coefficient (α = 0.56) and heterogeneous rate constant (ks = 0.32 s-1) at NCMO MRs/GCE were evaluated from kinetic studies. Furtherly, the diffusion coefficient of RDZ was found to be 2.32 × 10-6 cm2/s. In addition, NCMO MRs/GCE exhibits a low detection limit of RDZ (15 nM) along with better sensitivity (0.628 μA μM-1 cm-2). The fabricated RDZ sensor was successfully applied to real sample analysis in lake and tap water samples. Based on the results, we believe that the as-prepared NCMO MRs/GCE is a portable electrode material for RDZ sensors in environmental monitoring.
... Molybdate metals (NiMoO 4 , CoMoO 4 , FeMoO 4 , MnMoO 4 , etc.) have been used as anode materials for further research due to the synergistic effect of various chemical components, which makes them have good electrochemical activity and high lithium storage capacity [19][20][21][22][23][24][25]. However, due to the large change in specific volume during cycling and the slow kinetics of electron and lithium ion transmission, metal molybdate has poor cycling performance and low rate capability. ...
Lanthanum molybdate (La2(MoO4)3) is widely used in luminescence, sensors, ion exchange, and other fields due to its unique 4f electronic structure. But its research on energy storage applications is rarely reported. Herein, the La2(MoO4)3@C nanosheets are prepared by facile co-precipitation and hydrothermal method. The La2(MoO4)3@C nanosheets exhibit excellent electrochemical performance as an anode for LIBs. The as-prepared La2(MoO4)3@C nanosheets have high reversible capacity (726.6 mAh g⁻¹ at 0.2 A g⁻¹ after 100 cycles), superior rate capacity (347.68 mAh g⁻¹ at 3.0 A g⁻¹), and good cycle stability (419.3 mAh g⁻¹ after 600 cycles at 1.0 A g⁻¹). The carbon-coated nanosheet structure not only shortens the diffusion path and accelerates Li⁺ diffusion efficiency, but also greatly alleviates the volume changes of the molybdate, and improves the cycle stability.
... Such a structure enhances the surface area of the composites providing more number of electro-active sites for Faradaic reactions [30]. Apart from that, this CoMoO 4 as a defect interphase in MoO 3 @Co 3 O 4 nanocomposite is reported to demonstrate excellent electrochemical properties envisaging enhanced charge storage performance of the investigated material [34,35]. Further, it is found that the average crystallite size of the nanocomposite (calculated using Debye-Scherrer formula) is ∼23 nm which is more than pristine Co 3 O 4 nanoparticles i.e. ∼19 nm. ...
Constructing a novel nanocomposite structure based on Co 3 O 4 is of the current interest to design and develop efficient electrochemical capacitors. The capacitive performance of MoO 3 @Co 3 O 4 nanocomposite is compared with pristine Co 3 O 4 nanoparticles, both of them being synthesized by hydrothermal technique. A BET surface area of ~41 m ² g ⁻¹ (almost twice that of Co 3 O 4 )and average pore size of 3.6 nm is found to be suitable for promoting Faradaic reactions in the nanocomposite. Electrochemical measurements conducted on both samples predict capacitive behavior with quasi-reversible redox reactions. MoO 3 @Co 3 O 4 nanocomposite is capable of delivering a superior specific capacitance of 1248 Fg ⁻¹ at 0.5 Ag ⁻¹ along with notable stability of 92% even after 2000 cycles of charge-discharge and Coulombic efficiency approaching 100% at 10 Ag ⁻¹ . The outstanding results obtained in this work assure functional adequacy of MoO 3 @Co 3 O 4 nanocomposite in fabricating high-performance electrochemical capacitors.
... They confirmed from experimental results that these materials are the best candidates as electrode materials for supercapacitors due to their high specific capacitance, and best electrochemical performance. Similarly, CoS/NF, CuS/NF, FeS/NF, and NiS/NF [135], CoMoO4 [136]. NiMnO3 [137], Co@NiSe2 [138], C@Ni0.9Cu0.1-S ...
Supercapacitors (SCs) have received much interest due to their enhanced electrochemical performance, superior cycling life, excellent specific power, and fast charging–discharging rate. The energy density of SCs is comparable to batteries; however, their power density and cyclability are higher by several orders of magnitude relative to batteries, making them a flexible and compromising energy storage alternative, provided a proper design and efficient materials are used. This review emphasizes various types of SCs, such as electrochemical double-layer capacitors, hybrid supercapacitors, and pseudo-supercapacitors. Furthermore, various synthesis strategies, including sol-gel, electro-polymerization, hydrothermal, co-precipitation, chemical vapor deposition, direct coating, vacuum filtration, de-alloying, microwave auxiliary, in situ polymerization, electro-spinning, silar, carbonization, dipping, and drying methods, are discussed. Furthermore, various functionalizations of SC electrode materials are summarized. In addition to their potential applications, brief insights into the recent advances and associated problems are provided, along with conclusions. This review is a noteworthy addition because of its simplicity and conciseness with regard to SCs, which can be helpful for researchers who are not directly involved in electrochemical energy storage.
... Wang et al. [17] reported that the highest diffraction peak of α-MoO 3 appears at 2θ = 27.36 • ; meanwhile, Sen et al. [18] reported that it appears at 2θ = 27.32 • . Moreover, new peaks appear at 2θ = 26.5, 27.3, 28.2, 32.2, and 33.8 • in the Co-Mo/ZSM-5 catalyst, corresponding to β-CoMoO 4 (JCPDS-21-0868) [20][21][22][23]. Based on this analysis, it can be deduced that the metals have been impregnated with the ZSM-5 catalyst due to the appearance of the peaks corresponding to the impregnated metals. ...
... meanwhile, Sen et al. [18] reported that it appears at 2θ = 27.32°. Moreover, new peaks appear at 2θ = 26.5, 27.3, 28.2, 32.2, and 33.8° in the Co-Mo/ZSM-5 catalyst, corresponding to β-CoMoO4 (JCPDS-21-0868) [20][21][22][23]. Based on this analysis, it can be deduced that the metals have been impregnated with the ZSM-5 catalyst due to the appearance of the peaks corresponding to the impregnated metals. ...
The purposes of this study are to investigate the effect of metal (Co and Mo) impregnation to ZSM-5 catalysts on the Brønsted to Lewis (B/L) ratio as the active sites of cracking reaction, and the catalysts’ performance testing for palm oil cracking to produce hydrocarbon-rich biofuels. Both metals were impregnated on the ZSM-5 catalyst using a wet-impregnation method. The catalysts were characterized using X-ray diffraction (XRD), X-ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET), and Pyridine-probed Fourier-Transform Infrared (Py-FTIR) spectroscopy methods. The catalysts were tested on the cracking process of palm oil to biofuels in a continuous fixed-bed catalytic reactor. In order to determine the composition of the organic liquid product (OLP, biofuels), the product was analyzed using a gas chromatography-mass spectrometry (GC-MS) method. The results showed that the co-impregnation of Co and Mo to ZSM-5 highly increased the Brønsted to Lewis acid site (B/L) ratio, although the total number of acid sites decreased. However, the impregnation of Co and Mo on the ZSM-5 decreased the surface area of catalysts due to pore blocking by metals, while the B/L ratio of the catalysts increased. It was obtained that by utilizing Co- and Mo-impregnated ZSM-5 catalysts, the hydrocarbons product selectivity increased from 84.32% to 95.26%; however, the yield of biofuels decreased from 67.57% to 41.35%. The increase in hydrocarbons product selectivity was caused by the improvement of the Brønsted to Lewis (B/L) acid sites ratio.
... The charge transfer kinetics of Co 2+ /Co 3+ with the OHions in the KOH electrolyte results in the redox peaks of both the samples. The redox reaction process of Co 2+ /Co 3+ can be expressed as follows [28]. ...
... A linear relationship is observed for both the samples, represents the reaction kinetics of the electrode material during the redox process is probably controlled by the diffusion process. It is also evidenced by the increment of integral area enclosed by the cv curves as the scan rate increases [28,43]. ...
... The internal resistance (R b ) obtained from the Nyquist plots (0.82 Ω for R-CMO and 0.79 Ω for P-CMO) are in consistent with the values obtained from the equivalent circuit. The low R b , R ct and Z W estimations represent good electronic conductivity and typical electrochemical behavior of P-CMO than R-CMO electrode material [28,55,56]. ...
Effectively electrode materials with optimized morphologies have exposed promising potential in continuous development of supercapacitor electrochemical performance over the past few years. Here, we prepared a novel design of CoMoO4 (CMO) microstructures through hydrothermal/solvothermal method and obtained two different morphologies: rod-like and pebbles-like, respectively. The phase purity, structural characteristics and chemical bonding of the samples were analysed by x-ray diffraction (XRD), Fourier Transform - Infrared (FT-IR) analyses. The morphological characteristics and composition of the samples were examined using Field emission-scanning electron microscopy (FE-SEM) and Energy dispersive x-ray spectroscopy (EDS) analyses respectively. The elemental composition and chemical states of the materials was further evaluated using XPS analysis. Electrochemical behaviour of the two different CMO microstructures was evaluated using Cyclic voltammetry (CV), Galvanostatic charge discharge (GCD), and Electrochemical impedance spectroscopy (EIS) analyses. A high areal capacitance of 1.57 F cm⁻² for R-CMO and 2.27 F cm⁻² for P-CMO at 1.5 A cm⁻² and superior cycling stability of 90.49% for R- CMO, 85.95% for P-CMO was retained after 2,000 cycles. The unique hierarchical architectures with good structural and electrochemical properties of the materials creates new directions in the emerging field of energy storage applications.
... Figure 8c represents the GCD curves of ZnO/Co 3 O 4 calcined at different temperatures measured at a current density of 0.75 A g −1 . The GCD curves of these materials were not ideally linear, which could be attributed to redox reactions, 66 as shown in the CV curves. The specific capacitance values (C sg ) of ZnO/Co 3 O 4 @250, ZnO/ Co 3 O 4 @350, ZnO/Co 3 O 4 @450, and ZnO/Co 3 O 4 @550 were calculated to be 430, 610, 740, and 510 F g −1 , respectively, which were consistent with those of the CV measurement results, although the C sg values were smaller than the corresponding C sc values because of differences in the current density and scan ratio. ...
... The kinetics was also analyzed from the GCD curves ( Figure 10a,b). The nonlinear GCD curves suggested that the redox reactions of Co ions 66 were consistent with the CV curves. The discharging time of ZnO/Co 3 O 4 @450 was longer than that of Co 3 O 4 @450, indicating that ZnO/Co 3 O 4 @450 had a higher specific capacitance. ...
We developed a two-step chemical bath deposition method followed by calcination for the production of ZnO/Co3O4 nanocomposites. In aqueous reactions, ZnO nanotubes were first densely grown on Ni foam, and then flat nanosheets of Co3O4 developed and formed a porous film. The aspect ratio and conductivity of the Co3O4 nanosheets were improved by the existence of the ZnO nanotubes, while the bath deposition from a mixture of Zn/Co precursors (one-step method) resulted in a wrinkled plate of Zn/Co oxides. As a supercapacitor electrode, the ZnO/Co3O4 nanosheets formed by the two-step method exhibited a high capacitance, and after being calcined at 450 °C, these nanosheets attained the highest specific capacitance (940 F g–1) at a scan rate of 5 mV s–1 in the cyclic voltammetry analysis. This value was significantly higher than those of single-component electrodes, Co3O4 (785 F g–1) and ZnO (200 F g–1); therefore, the presence of a synergistic effect was suggested. From the charge/discharge curves, the specific capacitance of ZnO/Co3O4 calcined at 450 °C was calculated to be 740 F g–1 at a current density of 0.75 A g–1, and 85.7% of the initial capacitance was retained after 1000 cycles. A symmetrical configuration exhibited a good cycling stability (Coulombic efficiency of 99.6% over 1000 cycles) and satisfied both the energy density (36.6 Wh kg–1) and the power density (356 W kg–1). Thus, the ZnO/Co3O4 nanocomposite prepared by this simple two-step chemical bath deposition and subsequent calcination at 450 °C is a promising material for pseudocapacitors. Furthermore, this approach can be applied to other metal oxide nanocomposites with intricate structures to extend the design possibility of active materials for electrochemical devices.
