Displaying publications 21 - 40 of 75 in total

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  1. Fulltext Investigating the Correlation between Electrolyte Concentration and Electrochemical Properties of Ionogels
    Suen JW, Elumalai NK, Debnath S, Mubarak NM, Lim CI, Reddy Moola M, et al.
    Molecules, 2023 Jul 04;28(13).
    PMID: 37446854 DOI: 10.3390/molecules28135192
    Ionogels are hybrid materials comprising an ionic liquid confined within a polymer matrix. They have garnered significant interest due to their unique properties, such as high ionic conductivity, mechanical stability, and wide electrochemical stability. These properties make ionogels suitable for various applications, including energy storage devices, sensors, and solar cells. However, optimizing the electrochemical performance of ionogels remains a challenge, as the relationship between specific capacitance, ionic conductivity, and electrolyte solution concentration is yet to be fully understood. In this study, we investigate the impact of electrolyte solution concentration on the electrochemical properties of ionogels to identify the correlation for enhanced performance. Our findings demonstrate a clear relationship between the specific capacitance and ionic conductivity of ionogels, which depends on the availability of mobile ions. The reduced number of ions at low electrolyte solution concentrations leads to decreased ionic conductivity and specific capacitance due to the scarcity of a double layer, constraining charge storage capacity. However, at a 31 vol% electrolyte solution concentration, an ample quantity of ions becomes accessible, resulting in increased ionic conductivity and specific capacitance, reaching maximum values of 58 ± 1.48 μS/cm and 45.74 F/g, respectively. Furthermore, the synthesized ionogel demonstrates a wide electrochemical stability of 3.5 V, enabling diverse practical applications. This study provides valuable insights into determining the optimal electrolyte solution concentration for enhancing ionogel electrochemical performance for energy applications. It highlights the impact of ion pairs and aggregates on ion mobility within ionogels, subsequently affecting their resultant electrochemical properties.
    Matched MeSH terms: Electric Capacitance
  2. Fulltext Biomass-Derived Porous Carbons Derived from Soybean Residues for High Performance Solid State Supercapacitors
    Chung HY, Pan GT, Hong ZY, Hsu CT, Chong S, Yang TC, et al.
    Molecules, 2020 Sep 04;25(18).
    PMID: 32899765 DOI: 10.3390/molecules25184050
    A series of heteroatom-containing porous carbons with high surface area and hierarchical porosity were successfully prepared by hydrothermal, chemical activation, and carbonization processes from soybean residues. The initial concentration of soybean residues has a significant impact on the textural and surface functional properties of the obtained biomass-derived porous carbons (BDPCs). SRAC5 sample with a BET surface area of 1945 m2 g-1 and a wide micro/mesopore size distribution, nitrogen content of 3.8 at %, and oxygen content of 15.8 at % presents the best electrochemical performance, reaching 489 F g-1 at 1 A g-1 in 6 M LiNO3 aqueous solution. A solid-state symmetric supercapacitor (SSC) device delivers a specific capacitance of 123 F g-1 at 1 A g-1 and a high energy density of 68.2 Wh kg-1 at a power density of 1 kW kg-1 with a wide voltage window of 2.0 V and maintains good cycling stability of 89.9% capacitance retention at 2A g-1 (over 5000 cycles). The outstanding electrochemical performances are ascribed to the synergistic effects of the high specific surface area, appropriate pore distribution, favorable heteroatom functional groups, and suitable electrolyte, which facilitates electrical double-layer and pseudocapacitive mechanisms for power and energy storage, respectively.
    Matched MeSH terms: Electric Capacitance*
  3. Electronic Transport and Possible Superconductivity at Van Hove Singularities in Carbon Nanotubes
    Yang Y, Fedorov G, Shafranjuk SE, Klapwijk TM, Cooper BK, Lewis RM, et al.
    Nano Lett., 2015 Dec 09;15(12):7859-66.
    PMID: 26506109 DOI: 10.1021/acs.nanolett.5b02564
    Van Hove singularities (VHSs) are a hallmark of reduced dimensionality, leading to a divergent density of states in one and two dimensions and predictions of new electronic properties when the Fermi energy is close to these divergences. In carbon nanotubes, VHSs mark the onset of new subbands. They are elusive in standard electronic transport characterization measurements because they do not typically appear as notable features and therefore their effect on the nanotube conductance is largely unexplored. Here we report conductance measurements of carbon nanotubes where VHSs are clearly revealed by interference patterns of the electronic wave functions, showing both a sharp increase of quantum capacitance, and a sharp reduction of energy level spacing, consistent with an upsurge of density of states. At VHSs, we also measure an anomalous increase of conductance below a temperature of about 30 K. We argue that this transport feature is consistent with the formation of Cooper pairs in the nanotube.
    Matched MeSH terms: Electric Capacitance
  4. Fulltext Solid-phase electrochemical reduction of graphene oxide films in alkaline solution
    Basirun WJ, Sookhakian M, Baradaran S, Mahmoudian MR, Ebadi M
    Nanoscale Res Lett, 2013;8(1):397.
    PMID: 24059434 DOI: 10.1186/1556-276X-8-397
    Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO.
    Matched MeSH terms: Electric Capacitance
  5. Normalized bioimpedance indices are better predictors of outcome in peritoneal dialysis patients
    Koh KH, Wong HS, Go KW, Morad Z
    Perit Dial Int, 2010 06 30;31(5):574-82.
    PMID: 20592100 DOI: 10.3747/pdi.2009.00140
    BACKGROUND: While phase angle of bioimpedance analysis (BIA) has great survival-predicting value in dialysis populations, it is known to be higher in male than in female subjects. In this study, we aimed to explore the factors influencing the predictive value of phase angle and to identify the appropriate physics terms for normalizing capacitance (C) and resistance (R).

    METHODS: We formulated body capacitive index (BCI), C(BMI) (capacitance × height(2)/weight), body resistive index (BRI), R(BMI) (resistance × weight/height(2)), and CH(2) (capacitance × height(2)). We also studied H(2)/R, R/H, and reactance of a capacitor/height (X(C) /H). There are 3 components in this study design: (1) establishment of normal values in a control Malaysian population, (2) comparison of these with a CAPD population, and (3) prediction of survival within a CAPD population. We initially performed a BIA study in 206 female and 116 male healthy volunteers, followed by a prospective study in a cohort of 128 CAPD patients [47 with diabetes mellitus (DM), 81 non-DM; 59 males, 69 females] for at least 2 years. All the parameters during enrolment, including BIA, serum albumin, peritoneal equilibrium test, age, and DM status, were analyzed. Outcome measurement was survival.

    RESULTS: In healthy volunteers, both genders had the same BCI (2.0 nF kg/m(2)). On the contrary, female normal subjects had higher BRI than male normal subjects (median 15 642 vs 13242 Ω kg/m(2), p < 0.001) due to higher fat percentage (35.4% ± 0.4% vs 28.0% ± 0.6%, p < 0.001), resulting in a lower phase angle (mean 5.82 ± 0.04 vs 6.86 ± 0.07 degrees, p < 0.001). Logistic regression showed that BCI was the best risk indicator in 128 CAPD patients versus 322 normal subjects. In age- and body mass index (BMI)-matched head-to-head comparison, BCI had the highest χ(2) value (χ(2) = 102.63), followed by CH(2) (or H(2)/X(C); χ(2) = 81.00), BRI (χ(2) = 20.54), and X(C)/H (χ(2) = 20.48), with p value < 0.001 for these parameters. In comparison, phase angle (χ(2) = 11.42), R/H (χ(2) = 7.19), and H(2)/R (χ(2) = 5.69) had lower χ(2) values. 35 (27.3%) patients died during the study period. Univariate analysis adjusted for DM status and serum albumin level demonstrated that non-surviving patients had significantly higher CH(2) (245 vs 169 nF m(2), p < 0.001) and BCI (4.0 vs 2.9 nF m(2)/kg, p = 0.005) than patients that survived. CH(2) was the best predictor for all-cause mortality in Cox regression analysis, followed by BCI, phase angle, and X(C)/H.

    CONCLUSION: Measures that normalize, such as BCI and CH(2), have higher risk discrimination and survival prediction ability than measures that do not normalize, such as phase angle. Unlike phase angle, measurement of BCI overcomes the gender effect. In this study, the best risk indicator for CAPD patients versus the general population is BCI, reflecting deficit in nutritional concentration, while CH(2) reflects total nutritional deficit and thus is the major risk indicator for survival of CAPD patients.

    Matched MeSH terms: Electric Capacitance
  6. Fulltext Symmetrical supercapacitor using coconut shell-based activated carbon
    Ajina, Ahmida, Isa, Dino
    Pertanika Journal of Science & Technology, 2010;18(2):-.
    MyJurnal
    Two different supercapacitor configurations were fabricated using coconut shell-based activated
    carbon. Results for cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge-discharge measurements are presented and discussed for both configurations. The results show that coconut shell-based activated carbon is viable economical alternative electrode material to expensive activated carbon (AC) and carbon nano tubes (CNT). Meanwhile, the calculations from the charge-discharge characteristics show that the disk-shape supercapacitor, with 10% polyvinylidene fluoride binder (PVdF), has the highest specific capacitance (70F/g). Thus, the testing shows that the flat-laminated super-capacitor with 10% binder (PVdF) has the lowest (10.1ohms). Sources of high equivalent series resistance (ESR) are proposed and methods of reducing it are also discussed in this paper.
    Matched MeSH terms: Electric Capacitance
  7. Fulltext Analysis of absorber and buffer layer band gap grading on cigs thin film solar cell performance using SCAPS
    Nima Khoshsirat, Nurul Amziah Md Yunus, Mohd Nizar Hamidon, Suhaidi Shafie, Nowshad Amin
    Pertanika Journal of Science & Technology, 2015;23(2):241-250.
    MyJurnal
    A numerical simulation and analysis was performed to investigate the effect of absorber and buffer layer band gap grading and on a Copper-Indium-Gallium-Diselenide (CIGS) solar cell. The software used is the Solar Cell Capacitance Simulator (SCAPS). The absorber and buffer layer energy band structures’ effect on the cell’s output parameters such as open circuit voltage, short circuit current density, fill factor and efficiency were extensively simulated. Two structures of the energy band gap were simulated and studied for each of the absorber and buffer layer. The simulation was done on the uniform structure in which the energy band gap is constant throughout the layer. It was then continued on the cell with graded band structure, where the energy band gap of the material is varied throughout the layer. It was found that the cell with graded band structure in absorber and buffer layer had demonstrated higher efficiency and better performance in comparison with the cell with uniform band gap structure.
    Matched MeSH terms: Electric Capacitance
  8. Fulltext Top-oil temperature model for transformers based on nonlinear thermal resistance, lumped capacitance and thermal-electrical analogy
    Roslan, M.H., Azis, N., Jasni, J., Ibrahim, Z.
    Pertanika Journal of Science & Technology, 2017;25(102):151-160.
    MyJurnal
    Top-Oil Temperature (TOT) is one of the basic components to estimate the Hot-Spot temperature (HST) of the transformers. This paper presents an alternative TOT model based on the heat transfer theory that utilises Nonlinear Thermal Resistance (NTR) and Lumped Capacitance (LC) approaches. It is applied in a thermal-electrical analogy and the heat transfer equivalent equation is determined. This model is tested on a measured TOT of 250 MVA ONAF and 400 MVA ONAF transformers obtained from IEC 60076-7 and previous research. A comparison of TOT is carried out with the existing models IEC 60076-7 exponential and IEEE Loading Guide clause 7 methods. It is found that the thermal model based on the NTR and LC approach could determine the measured TOT closer than the existing methods available in the standards.
    Matched MeSH terms: Electric Capacitance
  9. Mechanistic insights into carbon dioxide utilization by superoxide ion generated electrochemically in ionic liquid electrolyte
    Halilu A, Hayyan M, Aroua MK, Yusoff R, Hizaddin HF
    Phys Chem Chem Phys, 2021 Jan 21;23(2):1114-1126.
    PMID: 33346756 DOI: 10.1039/d0cp04903d
    Understanding the reaction mechanism that controls the one-electron electrochemical reduction of oxygen is essential for sustainable use of the superoxide ion (O2˙-) during CO2 conversion. Here, stable generation of O2˙- in butyltrimethylammonium bis(trifluoromethylsulfonyl)imide [BMAmm+][TFSI-] ionic liquid (IL) was first detected at -0.823 V vs. Ag/AgCl using cyclic voltammetry (CV). The charge transfer coefficient associated with the process was ∼0.503. It was determined that [BMAmm+][TFSI-] is a task-specific IL with a large negative isovalue surface density accrued from the [BMAmm+] cation with negatively charged C(sp2) and C(sp3). Consequently, [BMAmm+][TFSI-] is less susceptible to the nucleophilic effect of O2˙- because only 8.4% O2˙- decay was recorded from 3 h long-term stability analysis. The CV analysis also detected that O2˙- mediated CO2 conversion in [BMAmm+][TFSI-] at -0.806 V vs. Ag/AgCl as seen by the disappearance of the oxidative faradaic current of O2˙-. Electrochemical impedance spectroscopy (EIS) detected the mechanism of O2˙- generation and CO2 conversion in [BMAmm+][TFSI-] for the first time. The EIS parameters in O2 saturated [BMAmm+][TFSI-] were different from those detected in O2/CO2 saturated [BMAmm+][TFSI-] or CO2 saturated [BMAmm+][TFSI-]. This was rationalized to be due to the formation of a [BMAmm+][TFSI-] film on the GC electrode, creating a 2.031 × 10-9 μF cm-2 double-layer capacitance (CDL). Therefore, during the O2˙- generation and CO2 utilization in [BMAmm+][TFSI-], the CDL increased to 5.897 μF cm-2 and 7.763 μF cm-2, respectively. The CO2 in [BMAmm+][TFSI-] was found to be highly unlikely to be electrochemically converted due to the high charge transfer resistance of 6.86 × 1018 kΩ. Subsequently, O2˙- directly mediated the CO2 conversion through a nucleophilic addition reaction pathway. These results offer new and sustainable opportunities for utilizing CO2 by reactive oxygen species in ionic liquid media.
    Matched MeSH terms: Electric Capacitance
  10. Fulltext Effects of Electrodeposition Mode and Deposition Cycle on the Electrochemical Performance of MnO2-NiO Composite Electrodes for High-Energy-Density Supercapacitors
    Rusi, Majid SR
    PLoS One, 2016;11(5):e0154566.
    PMID: 27182595 DOI: 10.1371/journal.pone.0154566
    Nanostructured network-like MnO2-NiO composite electrodes were electrodeposited onto stainless steel substrates via different electrodeposition modes, such as chronopotentiometry, chronoamperometry, and cyclic voltammetry, and then subjected to heat treatment at 300°C for metal oxide conversion. X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy were used to study the crystalline natures and morphologies of the deposited films. The electrochemical properties were investigated using cyclic voltammetry and charge/discharge tests. The results revealed that the electrochemical performance of the as-obtained composite electrodes depended on the electrodeposition mode. The electrochemical properties of MnO2-NiO composite electrodes prepared using cyclic voltammetry exhibited the highest capacitance values and were most influenced by the deposition cycle number. The optimum specific capacitance was 3509 Fg-1 with energy and power densities of 1322 Wh kg-1 and 110.5 kW kg-1, respectively, at a current density of 20 Ag-1 in a mixed KOH/K3Fe(CN)6 electrolyte.
    Matched MeSH terms: Electric Capacitance*
  11. Fulltext Layer by Layer Ex-Situ Deposited Cobalt-Manganese Oxide as Composite Electrode Material for Electrochemical Capacitor
    Rusi, Chan PY, Majid SR
    PLoS One, 2015;10(7):e0129780.
    PMID: 26158447 DOI: 10.1371/journal.pone.0129780
    The composite metal oxide electrode films were fabricated using ex situ electrodeposition method with further heating treatment at 300°C. The obtained composite metal oxide film had a spherical structure with mass loading from 0.13 to 0.21 mg cm(-2). The structure and elements of the composite was investigated using X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The electrochemical performance of different composite metal oxides was studied by cyclic voltammetry (CV) and galvanostatic charge-discharge (CD). As an active electrode material for a supercapacitor, the Co-Mn composite electrode exhibits a specific capacitance of 285 Fg(-1) at current density of 1.85 Ag(-1) in 0.5 M Na2SO4 electrolyte. The best composite electrode, Co-Mn electrode was then further studied in various electrolytes (i.e., 0.5 M KOH and 0.5 M KOH/0.04 M K3Fe(CN) 6 electrolytes). The pseudocapacitive nature of the material of Co-Mn lead to a high specific capacitance of 2.2 x 10(3) Fg(-1) and an energy density of 309 Whkg(-1) in a 0.5 M KOH/0.04 M K3Fe(CN) 6 electrolyte at a current density of 10 Ag(-1). The specific capacitance retention obtained 67% of its initial value after 750 cycles. The results indicate that the ex situ deposited composite metal oxide nanoparticles have promising potential in future practical applications.
    Matched MeSH terms: Electric Capacitance
  12. Fulltext Effect of shield placement for transient voltage mitigation due to switching surges in a 33/11 kV transformer windings
    Srikanta Murthy A, Azis N, Jasni J, Othman ML, Mohd Yousof MF, Talib MA
    PLoS One, 2020;15(10):e0240368.
    PMID: 33035254 DOI: 10.1371/journal.pone.0240368
    This study presents an investigation on the effect of shield placement for mitigation of transient voltage in a 33/11 kV, 30 MVA transformer due to Standard Switching Impulse (SSI) and Oscillating Switching Impulse (OSI) surges. Generally, the winding and insulation in transformers could experience severe voltage stress due to the external impulses i.e. switching events. Hence, it is important to examine the voltage stress and identify the mitigation action i.e. shield placements in order to reduce the adverse effect to the transformer windings. First, the resistances, inductances, and capacitances (RLC) were calculated for disc type transformer in order to develop the winding RLC equivalent circuit. The SSI and OSI transient voltage waveforms were applied to the High Voltage (HV) winding whereby the transient voltages were simulated for each disc. The resulting voltage stresses were mitigated through different configurations of electrostatic shield placements. The resonant oscillations generated due to switching surges were analysed through initial voltage distribution. The analyses on the transient voltages of the transformer winding and standard error of the slope (SEb) reveal that the location of shield placement has a significant effect on the resonant switching voltages. The increment of the shield number in the windings does not guarantee optimize mitigation of the resonant switching transient voltages. It is found that the voltage stress along the windings is linear once a floating shield is placed between the HV and Low Voltage (LV) windings of the disc-type transformer under the SSI and OSI waveforms. These findings could assist the manufacturers with appropriate technical basis for mitigation of the transformer winding against the external transient switching overvoltage surges.
    Matched MeSH terms: Electric Capacitance
  13. Fulltext High voltage-gain full-bridge cascaded dc-dc converter for photovoltaic application
    Hossain MZ, Selvaraj JA, Rahim NA
    PLoS One, 2018;13(11):e0206691.
    PMID: 30500857 DOI: 10.1371/journal.pone.0206691
    Over the past few years, high step-up dc-dc converters have been drawn substantial attention because of their wide-ranging application not only in the renewable energy sector but also in many other applications. To acquire a high voltage gain in photovoltaic (PV) and other renewable energy applications, a high step-up dc-dc converter is proposed in this paper. The proposed converter structure consists of a full-bridge (FB) module along with an input boost inductor and a voltage multiplier based on the Cockcroft-Walton (CW) principle with a parallel inductor. The key features of the proposed converter are: 1) high voltage gain with lower voltage stress on the switches, diodes and other passive elements without affecting the number of cascaded stages, 2) a minimum size of boost inductance and cascaded stage capacitance that ensures its compactness and low cost, and 3) a minimal number of major components. Circuit operation, steady-state analysis and various design parameters of the proposed converter are explained in details. In order to prove the performance of the theoretical analysis, a laboratory prototype is also implemented. The peak voltage gain and the maximum efficiency obtained are 11.9 and 94.6% respectively with very low input current ripple and output voltage ripple generated.
    Matched MeSH terms: Electric Capacitance
  14. Fulltext Extraction of winding parameters for 33/11 kV, 30 MVA transformer based on finite element method for frequency response modelling
    Srikanta Murthy A, Azis N, Jasni J, Othman ML, Mohd Yousof MF, Talib MA
    PLoS One, 2020;15(8):e0236409.
    PMID: 32853253 DOI: 10.1371/journal.pone.0236409
    This paper proposes an alternative approach to extract transformer's winding parameters of resistance (R), inductance (L), capacitance (C) and conductance (G) based on Finite Element Method (FEM). The capacitance and conductance were computed based on Fast Multiple Method (FMM) and Method of Moment (MoM) through quasi-electrostatics approach. The AC resistances and inductances were computed based on MoM through quasi-magnetostatics approach. Maxwell's equations were used to compute the DC resistances and inductances. Based on the FEM computed parameters, the frequency response of the winding was obtained through the Bode plot function. The simulated frequency response by FEM model was compared with the simulated frequency response based on the Multi-conductor Transmission Line (MTL) model and the measured frequency response of a 33/11 kV, 30 MVA transformer. The statistical indices such as Root Mean Square Error (RMSE) and Absolute Sum of Logarithmic Error (ASLE) were used to analyze the performance of the proposed FEM model. It is found that the simulated frequency response by FEM model is quite close to measured frequency response at low and mid frequency regions as compared to simulated frequency response by MTL model based on RMSE and ASLE analysis.
    Matched MeSH terms: Electric Capacitance*
  15. Fulltext Semi-analytical modelling and evaluation of uniformly doped silicene nanotransistors for digital logic gates
    Chuan MW, Wong KL, Riyadi MA, Hamzah A, Rusli S, Alias NE, et al.
    PLoS One, 2021;16(6):e0253289.
    PMID: 34125874 DOI: 10.1371/journal.pone.0253289
    Silicene has attracted remarkable attention in the semiconductor research community due to its silicon (Si) nature. It is predicted as one of the most promising candidates for the next generation nanoelectronic devices. In this paper, an efficient non-iterative technique is employed to create the SPICE models for p-type and n-type uniformly doped silicene field-effect transistors (FETs). The current-voltage characteristics show that the proposed silicene FET models exhibit high on-to-off current ratio under ballistic transport. In order to obtain practical digital logic timing diagrams, a parasitic load capacitance, which is dependent on the interconnect length, is attached at the output terminal of the logic circuits. Furthermore, the key circuit performance metrics, including the propagation delay, average power, power-delay product and energy-delay product of the proposed silicene-based logic gates are extracted and benchmarked with published results. The effects of the interconnect length to the propagation delay and average power are also investigated. The results of this work further envisage the uniformly doped silicene as a promising candidate for future nanoelectronic applications.
    Matched MeSH terms: Electric Capacitance*
  16. Fulltext Characterization of Aloe Barbadensis Miller leaves as a potential electrical energy source with optimum experimental setup conditions
    Chong PL, Singh AK, Kok SL
    PLoS One, 2019;14(6):e0218758.
    PMID: 31237903 DOI: 10.1371/journal.pone.0218758
    Electrical energy can be harvested from the living plants as a new potential renewable energy source. Characterization of the electrical signal is needed to enable an optimum energy harvesting setup condition. In the present paper, an investigation is conducted to analyze the characteristic of Aloe Barbadensis Miller (Aloe Vera) leaves in terms of electrical energy generation under specific experimental setups. The experimental results show that 1111.55uW electrical power can be harvested from the Aloe Vera with 24 pairs of electrodes and this energy is capable to be stored in a capacitor. This energy has a high potential to be used to power up a low power consumption device.
    Matched MeSH terms: Electric Capacitance
  17. Fulltext Enhancing capacitive performance of magnetite-reduced graphene oxide nanocomposites through magnetic field-assisted ion migration
    Abdul Jalil NAS, Aboelazm E, Khe CS, Ali GAM, Chong KF, Lai CW, et al.
    PLoS One, 2024;19(2):e0292737.
    PMID: 38324619 DOI: 10.1371/journal.pone.0292737
    The transition towards renewable energy sources necessitates efficient energy storage systems to meet growing demands. Electrochemical capacitors, particularly electric double-layer capacitors (EDLCs), show promising performance due to their superior properties. However, the presence of resistance limits their performance. This study explores using an external magnetic field to mitigate ion transfer resistance and enhance capacitance in magnetite-reduced graphene oxide (M-rGO) nanocomposites. M-rGO nanocomposites with varying weight ratios of magnetite were synthesized and comprehensively characterized. Characterization highlighted the difference in certain parameters such as C/O ratio, the Id/Ig ratio, surface area and particle size that contribute towards alteration of M-rGO's capacitive behaviour. Electrochemical studies demonstrated that applying a magnetic field increased specific capacitance by approximately 20% and reduced resistance by 33%. Notably, a maximum specific capacitance of 16.36 F/g (at a scan rate of 0.1 V/s) and 27.24 F/g (at a current density of 0.25 A/g) was achieved. These improvements were attributed to enhanced ion transportation and migration at the electrode/electrolyte interface, lowering overall resistance. However, it was also observed that the aforementioned parameters can also limit the M-rGO's performance, resulting in saturated capacitive state despite a reduced resistance. The integration of magnetic fields enhances energy storage in nanocomposite systems, necessitating further investigation into underlying mechanisms and practical applications.
    Matched MeSH terms: Electric Capacitance
  18. Fulltext Blending and Characteristics of Electrochemical Double-Layer Capacitor Device Assembled from Plasticized Proton Ion Conducting Chitosan:Dextran:NH4PF6 Polymer Electrolytes
    B Aziz S, Brza MA, Brevik I, Hafiz MH, Asnawi ASFM, Yusof YM, et al.
    Polymers (Basel), 2020 Sep 16;12(9).
    PMID: 32947829 DOI: 10.3390/polym12092103
    This research paper investigates the electrochemical performance of chitosan (CS): dextran (DX) polymer-blend electrolytes (PBEs), which have been developed successfully with the incorporation of ammonium hexafluorophosphate (NH4PF6). X-ray diffraction (XRD) analysis indicates that the plasticized electrolyte system with the highest value of direct current (DC) ionic conductivity is the most amorphous system. The glycerol addition increased the amorphous phase and improved the ionic dissociation, which contributed to the enhancement of the fabricated device's performance. Transference number analysis (TNM) has shown that the charge transport process is mainly by ions rather than electrons, as tion = 0.957. The CS:DX:NH4PF6 system was found to decompose as the voltage goes beyond 1.5 V. Linear sweep voltammetry (LSV) revealed that the potential window for the most plasticized system is 1.5 V. The fabricated electrochemical double-layer capacitor (EDLC) was analyzed with cyclic voltammetry (CV) and charge-discharge analysis. The results from CV verify that the EDLC in this work holds the characteristics of a capacitor. The imperative parameters of the fabricated EDLC such as specific capacitance and internal resistance were found to be 102.9 F/g and 30 Ω, respectively. The energy stored and power delivered by the EDLC were 11.6 Wh/kg and 2741.2 W/kg, respectively.
    Matched MeSH terms: Electric Capacitance
  19. Fulltext The Study of Plasticized Solid Polymer Blend Electrolytes Based on Natural Polymers and Their Application for Energy Storage EDLC Devices
    Dannoun EMA, Aziz SB, Brza MA, M Nofal M, Asnawi ASFM, Yusof YM, et al.
    Polymers (Basel), 2020 Oct 29;12(11).
    PMID: 33138114 DOI: 10.3390/polym12112531
    In this work, plasticized magnesium ion-conducting polymer blend electrolytes based on chitosan:methylcellulose (CS:MC) were prepared using a solution cast technique. Magnesium acetate [Mg(CH3COO)2] was used as a source of the ions. Nickel metal-complex [Ni(II)-complex)] was employed to expand the amorphous phase. For the ions dissociation enhancement, glycerol plasticizer was also engaged. Incorporating 42 wt% of the glycerol into the electrolyte system has been shown to improve the conductivity to 1.02 × 10-4 S cm-1. X-ray diffraction (XRD) analysis showed that the electrolyte with the highest conductivity has a minimum crystallinity degree. The ionic transference number was estimated to be more than the electronic transference number. It is concluded that in CS:MC:Mg(CH3COO)2:Ni(II)-complex:glycerol, ions are the primary charge carriers. Results from linear sweep voltammetry (LSV) showed electrochemical stability to be 2.48 V. An electric double-layer capacitor (EDLC) based on activated carbon electrode and a prepared solid polymer electrolyte was constructed. The EDLC cell was then analyzed by cyclic voltammetry (CV) and galvanostatic charge-discharge methods. The CV test disclosed rectangular shapes with slight distortion, and there was no appearance of any redox currents on both anodic and cathodic parts, signifying a typical behavior of EDLC. The EDLC cell indicated a good cyclability of about (95%) for throughout of 200 cycles with a specific capacitance of 47.4 F/g.
    Matched MeSH terms: Electric Capacitance
  20. Fulltext Characteristics of Glycerolized Chitosan: NH4NO3-Based Polymer Electrolyte for Energy Storage Devices with Extremely High Specific Capacitance and Energy Density Over 1000 Cycles
    Aziz SB, Brza MA, Brevik I, Hamsan MH, Abdulwahid RT, Majid SR, et al.
    Polymers (Basel), 2020 Nov 17;12(11).
    PMID: 33212879 DOI: 10.3390/polym12112718
    In this work, plasticized polymer electrolyte films consisting of chitosan, ammonium nitrate (NH4NO3) and glycerol for utilization in energy storage devices was presented. Various microscopic, spectroscopic and electrochemical techniques were used to characterize the concerned electrolyte and the electrical double-layer capacitor (EDLC) assembly. The nature of complexation between the polymer electrolyte components was examined via X-ray diffraction analysis. In the morphological study, field emission scanning electron microscopy (FESEM) was used to investigate the impact of glycerol as a plasticizer on the morphology of films. The polymer electrolyte (conducting membrane) was found to have a conductivity of 3.21 × 10-3 S/cm. It is indicated that the number density (n), mobility (μ) and diffusion coefficient (D) of ions are increased with the glycerol amount. The mechanism of charge storing was clarified, which implies a non-Faradaic process. The voltage window of the polymer electrolyte is 2.32 V. It was proved that the ion is responsible for charge-carrying via measuring the transference number (TNM). It was also determined that the internal resistance of the EDLC assembly lay between 39 and 50 Ω. The parameters associated with the EDLC assembly are of great importance and the specific capacitance (Cspe) was determined to be almost constant over 1 to 1000 cycles with an average of 124 F/g. Other decisive parameters were found: energy density (18 Wh/kg) and power density (2700 W/kg).
    Matched MeSH terms: Electric Capacitance
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