Capacitive Nature Research Articles

Fabrication of cerium vanadate-embedded on carbon based graphene material (rGO) with significant performance for supercapacitor electrode

This work examined the electrochemical properties of CeVO3 nanocomposite that were enhanced with reduced graphene oxide (rGO) and CeVO3 nanoparticles. The CeVO3/rGO fabricated using a typical hydrothermal process that was further characterized via XRD revealed the monoclinic crystalline structure of the CeVO3 nanoparticles. The presence of uniformly distributed particles structured CeVO3 and layer-structured (rGO) reduced graphene oxide in the nanocomposite materials was determined using scanning electron microscopy pictures. We evaluated the electro-chemical efficiency of the nanocrystals for enhanced working electrodes and supercapacitors with cerium vanadate (CeVO3) nanoparticles and the cerium vanadate (CeVO3) embedded on reduced graphene oxide (rGO). The analysis was conducted on 2.0 M aqueous KOH (potassium hydroxide) electrolytic solution and it achieved the capacitance of 355.46 F g−1 (10 mVs−1) was concluded by cyclic voltammetry analysis of the working electrode modified with pure CeVO3 nanomaterial. The addition of rGO improved the value of Cs to 947.30 F g−1 at the same scan speed (10 mVs−1). The CeVO3 nanoparticles and CeVO3/rGO nanocomposite exhibited the capacitance values of 698.54 F g−1 and 1403.35 F g−1 at 1 A g−1 respectively, as determined by GCD analysis. The fabricated with CeVO3 nanoparticles exhibited power density values of 254.1 W kg−1 and energy values of 25.05 W h kg−1. On the other hand, the CeVO3/rGO nanocomposite showed greater energy (Ed) and power (Pd) density of 54.72 W h kg−1 and 264.95 W kg−1, individually. After undergoing 5000th cycles, the material utilizing CeVO3/rGO composite maintained its stability. The electrochemical examination of the synthesized cerium vanadate nanoparticles revealed that the inclusion of rGO resulted in a hybrid capacitive nature and the proposed nanocomposite can be employed as supercapacitors or as electrodes in batteries as well as energy storage and generating device for future use.

Ionic liquid supported chitosan-g-SPA as a biopolymer-based single ion conducting solid polymer electrolyte for energy storage devices

This article discusses the preparation of different grades of single-ion conducting quasi-solid polymer electrolytes (q-SPE) material (Chit-g-SPA-IL) based on biopolymer (chitosan), polyacrylic acid and DBU-acetate (DBUH+ AcO−) ionic liquid. Chit-SPA-60 %-IL exhibited the highest conductivity within the range of 10−4 S/cm. TGA analysis demonstrated the stability of electrolytes up to a temperature of 120 °C. SEM-EDS analysis unveiled the porous nature of the electrolyte and even distribution of ions throughout the matrix. It exhibited an electrochemical stability window (EWS) of 2.53 V with significant current density and an ionic transference number (ITN) of ~99.9 %. The temperature-dependent conductivity established an Arrhenius-type conduction mechanism with an activation energy of 0.149 eV for ion movement within the electrolyte matrix. The AC conductivity analysis emphasized the time-temperature independence of the ionic conduction mechanism. Dielectric analysis highlighted the capacitive nature of the electrolyte, underlining its substantial capacitance, while modulus studies indicated minimal influence from the electrode-electrolyte interface. Chit-SPA-60 %-IL at 30 °C included a self-diffusion coefficient of 4.57 × 10−5 m2/s, ionic mobility of 1.75 × 10−3 m2/Vs, and drift ionic velocity of 0.44 m/s. These findings makes SPE as a promising candidate for sodium-ion-based energy storage devices.

Green fuel mediated Europium doped Lanthanum ferrites Synthesis, characterisation of and their application as photocatalyst and antibacterial agents

The focus of multiapplication of the nanomaterial is the recent research. Based on that the current work describes synthesis of nano Lanthanum ferrites doped with Europium (1 mol, 3 mol, 5 mol and 7 mol%) by cost effective biofuel combustion method, using Ocimum tenuiflorum extract as fuel. The doping possibly changed the size and morphology of the host as evident from results of XRD, SEM and TEM analysis. As there is increase in band gap from 2.2 to 2.5 eV for undoped to 5 mol% doped Europium which strongly supports the photocatalytic degradation of Congo Red dye in the UV and visible light. The 5 mol% doped Eu shows 65 % and 81 % in UV-light and Visible light respectively. The electrochemical studies indicates the accepted capacitance and semiconductor nature of synthesised nano ferrites. The antibacterial activity was tested against Escherichia coli and Staphylococcus aureus showed 5 mol% Eu doped LFO was more effective than other synthesized LFO.

Surface dynamics and electrochemical examination of Co3O4 films by iron doping

This study focused on Co3O4 films, which were prepared by cost-effective chemical bath deposition on In:SnO2 (ITO) substrates with iron doping concentrations ranging from 2 to 6 mol %. Structural properties were investigated by XRD as well as nanotexture of Fe: Co3O4 films was captured via SEM and detailed fractal analysis was analyzed in each prepared film. Effective using of prepared Fe: Co3O4 electrodes for electrochemical charge storage applications has been examined by using CV and EIS. From x-ray patterns, spinel cubic structure of Co3O4 was observed in all samples, while peaks with Co2O3 and substrate indexed peaks were also shown. Pure and iron doped Co3O4 surfaces have spherical agglomerative forms while porous structures were observed in 4% Co3O4 samples. Redox peaks induced by Faradaic reactions in the CV plots present pseudo- capacitive nature for all electrodes and improves charge transfer process in 4% Co3O4 and 6% Co3O4 from EIS measurements. Additionally, using scaling theory, the coverage ratio, fractal dimensions, cluster sizes and interface critical exponent values of the superficial hetero morphology of the samples are calculated. While the coating rate decreases according to the iron concentration, fractal dimensions increase. However, as the number of clusters increases, the average cluster size decreases. The interface critical exponent value shows an irregular change.

Scalable synthesis of 2D-layered Ti3C2 MXene by HF etching method; electrochemical investigations and device fabrication to enhancing capacitive nature

The goal of the current effort is aimed to synthesise the uniform exfoliated titanium carbide (Ti3C2) MXene sheets by utilising hydrofluoric (HF) acid to remove/etch “aluminium” from the parental Ti3AlC2 MAX phase. The Ti3C2 MXene was investigated by structural analysis using X-ray diffraction (XRD), Higher Resolution Transmission Electron Microscope (HRTEM), Scanning electron microscope (SEM), and EDS with mapping for morphological and elemental analysis, Moreover, the Ti3C2 MXene was studied its electrochemical properties to electrochemical energy storage application using cyclic voltammetry (CV), Galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques. Since the GCD analysis of Ti3C2 MXene, a great specific capacitance (Csp) of 318F/g was attained with current density of 1 A/g and up to 90 % retentivity was attained after 7500 cycles. Besides, fabricated Ti3C2 MXene||Ti3C2-MXene symmetric supercapacitor device (SSD) has described the energy density (ED) of 27.78 Wh/kg at a power density (PD) of 400 W/kg and the capacitive retention existed attained 92.1 % after 7500 cycles with 5 A/g.

The impact of Ru and Gd dopants on the dielectric and conductive properties of NiO nanoparticles: A comparative study

This comparative study investigates the difference between the transition metal (Ru) and rare earth element (Gd) as dopants in NiO nanoparticles, to unveil their suitability in various applications. Pure, Ru- and Gd-doped NiO nanoparticles have been synthesized by the chemical co-precipitation method, in the presence of polyvinylpyrrolidone, as a capping agent. The EDX pattern revealed the purity, the un-stoichiometric nature of the synthesized nanoparticles, and the influence of the Ru- and Gd-dopants in generating advantageous structural imperfections, including oxygen and nickel vacancies. The dielectric and conductivity measurements have provided valuable insights into the electrical behavior of Ru- and Gd-doped NiO nanoparticles. The influence of the Ru- and Gd-dopants on the Debye model, universal dielectric model, and relaxation mechanism was implemented. The dielectric constant was affected by the dopants, where the Ru-dopants reduced it by a factor of 0.24, however, the Gd-dopants boosted it by a factor of 4. Moreover, the opposing influence of the Ru- and Gd-dopants on the nickel vacancies has tuned the ac conductivity of the NiO lattice, where it was reduced by 75 % with Ru-dopants due to the suppressed nickel vacancies and enhanced by 70 % with the Gd-dopants due to the augmented nickel vacancies. The dc conductivity was examined at ranging temperatures to explore the conduction mechanism and the effect of the dopants. The multi-functional ability of the pure, Ru- and Gd-doped NiO nanoparticles was tested by studying the complex power and temperature coefficient of resistance (TCR), from which the dominating capacitive and resistive nature is identified for the samples. Besides, NiO nanoparticles have attained a maximum TCR value of −10.41 %, rendering it a superior material for bolometric devices, even better than the used conventional materials. The studied dielectric and conductive properties unveiled the potential applicability of the samples in microelectronics, storage capacitor applications, and bolometric devices.

Synthesis of Binder-Free, Low-Resistant Randomly Orientated Nanorod/Sheet ZnS-MoS2 as Electrode Materials for Portable Energy Storage Applications.

The scientific community needs to conduct research on novel electrodes for portable energy storage (PES) devices like supercapacitors (S-Cs) and lithium-ion batteries (Li-ion-Bs) to overcome energy crises, especially in rural areas where no electrical poles are available. Herein, the nanostructured MoS2 and ZnS-MoS2 E-Ms consisting of nanoparticles/rods/sheets (N-Ps-Rs-Ss) are deposited on hierarchical nickel foam by a homemade chemical vapor deposition (H-M CVD) route. The X-ray diffraction patterns confirm the formation of polycrystalline films growing along various orientations, whereas the field-emission scanning electron microscope analysis confirms the formation of N-Ps-Rs-Ss. The change in structural and microstructural parameters indicates the existence of defects improving the energy storage ability of the deposited ZnS-MoS2@Ni-F electrodes. The specific capacitances of MoS2@Ni-F and ZnS-MoS2@Ni-F electrodes are found to be 1763 and 3565 F/g at 0.5 mV/s and 1451 and 3032 F/g at 1 A/g, respectively. The growing behavior of impedance graphs indicates their capacitive nature; however, the shifting of impedance curves toward y-axis indicates that the increasing diffusion rates due to the formation of nanostructures of ZnS-MoS2 results in low impedance. An excellent energy storage performance, minimum capacity fading, and improved electrical conductivity of the deposited E-Ms are due to the combined contributions of the electrical double layer and pseudocapacitor nature, which is again confirmed by theoretical Dunn's model. The absence of charge transfer resistance and good capacitance retention (95%) even after 10,000 cycles indicates that the deposited E-Ms are better for PES devices like S-Cs and Li-ion-Bs than MoS2 E-Ms. The assembled asymmetric supercapacitor device exhibited the maximum specific capacitance = 996 F/g, energy density = 354-285 W h/kg, power density = 2400-24,000 W/kg, capacitance retention = 95% and Coulombic efficiency = 100% even after a long charging-discharging of 10,000 cycles.

Nanocrystalline cellulose as a reinforcing agent for poly (vinyl alcohol)/ gellan-gum-based composite film for moxifloxacin ocular delivery

Nanocrystalline cellulose (NCC) is a star material in drug delivery applications due to its good biocompatibility, large specific surface area, high tensile strength (TS), and high hydrophilicity. Poly(Vinyl Alcohol)/Gellan-gum-based innovative composite film has been prepared using nanocrystalline cellulose (PVA/GG/NCC) as a strengthening agent for ocular delivery of moxifloxacin (MOX) via solvent casting method. Impedance analysis was studied using the capacitive sensing technique for examining new capacitance nature of the nanocomposite MOX film. Antimicrobial properties of films were evaluated using Pseudomonas aeruginosa and Staphylococcus aureus as gram-negative and gram-positive bacteria respectively by disc diffusion technique. XRD revealed the characteristic peak of NCC and the amorphous form of the drug. Sustained in vitro release and enhanced corneal permeation of drug were noticed in the presence of NCC. Polymer matrix enhanced the mechanical properties (tensile strength 22.05 to 28.41 MPa) and impedance behavior (resistance 59.23 to 213.23 Ω) in the film due to the presence of NCC rather than its absence (16.78 MPa and 39.03 Ω respectively). Occurrence of NCC brought about good antimicrobial behavior (both gram-positive and gram-negative) of the film. NCC incorporated poly(vinyl alcohol)/gellan-gum-based composite film exhibited increased mechanical properties and impedance behavior for improved ocular delivery of moxifloxacin.

Structural transformations and enhanced electrochemical performance of Co doped NiS2 nanosheets for supercapacitor applications

Doping and morphology tailoring in metal sulfides up to nanoscale plays a vital role for better performance in various applications. Herein hydrothermally synthesized Co-doped nickel sulfide (NiS2) nanostructures have been transformed from nano-rods to nano-sheets up to optimal doping concentration of 3 %. The phase changes, morphological modifications and elemental investigations have been analyzed by SEM, TEM, HRTEM, SAED, EDS, XRD and FTIR. The morphology transitions revealed that NiCo3S exhibited sophisticated morphology of flower like structures formed by nano-sheet patterns. NiCo3S electrode possesses an auspicious capacitance of 1242 Fg_1 at 1 Ag_1 within potential window range of 0.1–0.8 V. In accordance with GCD study, CV and EIS study confirmed that NiCo3S is more electroactive and less resistive showing excellent stability up to 92 % after 5000 cycles. The power law (b = 0.71) showed the capacitive nature of the NiCo3S. The capacitive and diffusive behavior calculated by Dunn’s relationship confirmed the pseudocapacitive charge storage behavior of NiCo3S electrode making this a potential candidate for electrochemical applications.

Effect of fluoride (CoF2) based electrode material for high energy and power density asymmetric flexible supercapacitors

Herein, an asymmetric supercapacitor (ASC) device was assembled by employing the pristine CoF2 as active positive electrode material and activated carbon (AC) as negative electrode material. The CoF2 electrode exhibited an outstanding electrochemical behavior with enhanced specific capacitance (Cs) of 872 F/g at 1 A/g current density in three electrode configurations. The reversible Faradaic redox reactions in CoF2 instigate the formation of cobalt-oxyfluorides and generating the mixed valence state of Co (Co2+ and Co3+) which improves its electrical conductivity and electrochemical behaviors. Furthermore, the room temperature paramagnetic nature of CoF2 increases the gradient force of ions which could possibly increase the redox reactions at the electrolyte/electrode interface. The constructed asymmetric device structure of CoF2//AC revealed a quasi-rectangular shaped cyclic voltametric curve and symmetrical semi-triangular shaped galvanostatic charge-discharge profiles, respectively, which affirms the combined electric double layer capacitance and pseudocapacitive nature by its hybrid assembly. Hence, the constructed CoF2//AC ASC demonstrated a remarkable specific capacitance of 141 F/g, energy density of 44.06 Wh.Kg−1, and power density of 422.97 W.Kg−1 at 1 A/g with the high cell voltage of 1.5 V. The CoF2//AC ASC device retained c.a. 92 % of its initial capacitance and attained over 96 % of Coulombic efficiency after 2000 cycles of charge-discharge profiles at 1 A/g, which suggests the high electrochemical stability. This admirable electrochemical performance and the origin towards the magneto-capacitance of CoF2 could pave a new way to explore next generation high-performance supercapacitors.

Thermogravimetric and temperature-dependent electrical investigations of Pr3+ doped multi-component silicate glasses for microelectronic technology

Multi-component silicate glasses doped with 0, 0.5, 1, and 1.5 mol% of praseodymium (Pr3+) were synthesized by the sol–gel method. Thermal analysis of the glasses, evinced a high working temperature of 351 °C and Hruby coefficient, K H = 1.415 in the highly doped system, corroborating the effective role of Pr3+ ions in endowing superior thermal stability to the glass. Broadband dielectric spectroscopy was applied to study the temperature-dependent electrical behavior of the glasses for their suitability as electrodes and solid electrolyte materials in batteries. A high dielectric constant of 4797 was evidenced at 1 kHz when recorded at 473 K. The AC conductivity of the glass doped with 1 mol% was observed to be the highest with 94.8 × 10−5 S cm−1 at 10 MHz and 473 K. Jonscher’s power law exponent decreased with temperature, attributing the conducting mechanism to the Correlated Barrier Hopping (CBH) model. The Nyquist impedance spectra demonstrated a depressed semicircle with a spur at the low-frequency end, validating the non-Debye relaxation in the glasses. The equivalent circuitry of the plot predicted parallel combinations of resistor and constant phase elements which reflects a Warburg diffusion and capacitive approach. Bode’s phasor diagram confirmed the capacitive nature by a phase angle of −90° in all the glasses. While a uniform increase in dielectric constant and conductivity was observed up to 1 mol% of Pr3+, a sharp decline in the electrical phenomenon was observed with 1.5 mol% of Pr3+, due to the possible blockade of the hopping of charge carriers by the largely quantified dopant ions. Extracting a high dielectric constant, and ionic conductivity at high frequencies, with an optimal dopant concentration of 1 mol% Pr3+, the composite glasses could be considered for their potential use in integrated microcomponent storage devices as cathode and solid electrolyte materials.

Optimizing energy storage: Carbon implantation in NiO matrix unveils C–NiO's hybrid capacitive and battery-like behavior with enhanced electrochemical performance

Doping is a common strategy employed to enhance material properties. Numerous researchers have introduced carbon into the nickel oxide (NiO) matrix through various methods to improve the electrochemical performance for energy storage applications. This study investigates the impact of carbon implantation into the NiO matrix using a particle accelerator. Cyclic voltammetry profiles of carbon-implanted NiO (C–NiO) reveal distinct oxidation–reduction peaks, and one side of the CV curves exhibits a rectangular shape, confirming the hybrid capacitive and battery-like behavior of C–NiO. The reduced separation between oxidation–reduction peaks and the increased specific capacitance at higher scan rates validate the capacitive nature of C–NiO. Enhanced electrochemical performance was further explored through GCD, EIS, and BET techniques. C–NiO demonstrates impressive capacitance retention of 93.8 % after 5000 cycles. The Nyquist plot indicates that the improved performance of C–NiO is attributed to its heightened electrode activity, resulting from lower charge-transfer resistance. BET analysis confirms that C-doping leads to a larger surface area. In the NiO matrix, two bands of adsorbed CO2 are observed, whereas these bands are absent in C–NiO, indicating clearer pathways for ion–electron exchange. Compared to undoped NiO (55 F/g at 50 mV/s), C–NiO exhibits a more than tenfold increase in specific capacitance (1079 F/g at 50 mV/s).

FT-Raman spectroscopic and electrical investigations of RE3+ doped multi-functional silicate glasses for cathode plating and integrated microelectronic technology

Lanthanide-doped silicate glasses were subjected to structural and temperature-dependent electrical investigations to validate their multi-functionality in the integrated microelectronic industries. Raman-active vibrations around 920 cm−1 and 1330 cm−1 confirmed the silicate and phosphate tetrahedra respectively. The Er3+ doped glass demonstrated the highest dielectric constant of 9.21 × 105, while Sm3+ infused glass exhibited the lowest dielectric constant of 4.37 × 104 at 0.1 Hz and 473 K. The Sm3+ doped glasses are prospective for plating on copper chips in printed circuit boards that necessitate low dielectric constants to minimize propagation delay. The equivalent circuitry fitted for the Nyquist impedance plot of Er3+ doped glass constituted parallel combinations of a resistor and Constant Phase Element (CPE), in series with Warburg diffusion impedance. The CPE approaching a capacitive nature in the Er3+ doped glass could be suggested for cathode plating in batteries, and fabrication of multi-layer dielectric substrates in radio frequency condensers.

Hydrophobic polymer nano hybrid ternary composite electrode for nanomolar tracing of Cd2+ ions

AbstractIn the present study, we reported the successful synthesis of a ternary nano hybrid polymer composite system obtained by solution casting. Composing carbon nanotubes (CNTs) and molybdenum disulfide (MoS2) in ethylene vinyl acetate (EVA) derived ECM ternary electrode. It demonstrated an excellent electrochemical sensor performance and a more efficient supercapacitor. Chemical structure of hybrid electrode Fourier transform Infrared Spectroscopy (FTIR) illustrated the CS and CN stretching with MoS2 and CNT new bands (at 1368 and 1032 cm−1). FE‐SEM and Atomic force microscopy (AFM) 3D topographic image identified the decreased rough morphology of the hybrid electrode. Whereas contact angle measurements revealed the enhanced wettability of electrode system. Microporous nature of the hybrid electrode was observed through SEM investigation. Transmission electron microscopy (TEM) revealed the nano hybrid entity in a hybrid electrode system. XRD and TEM investigation confirmed semicrystalline phase of the hybrid electrode system due to the presence of MoS2. D band, G bands, E12g and A1g vibrational modes in Raman spectroscopy revealed the occupied hybrid filler CNTs and MoS2. An electroactive site for the Cd2+ ion sensor was confirmed by the ECM/PGE hybrid electrode. It comply the desirable sensor qualities, such as excellent selectivity, reproducibility and repeatability with a high accuracy and lower detection limit of 15 nM. Additionally, the ECM/PGE electrode demonstrated a capacitive nature with an aerial capacitance of 73 μF/cm2 at an applied current density of 3 μA/cm2. Furthermore, it exhibited a power density of 44 mW/cm2 and an energy density of 148 μWh/cm2 over a wide potential range of 1 V.

Synchronous activation of praseodymium vanadate/graphitic carbon nitride nanocomposite: A promising electrode material for detection of flavonoid– Quercetin

Flavonoids or phenolic compounds are part of the daily intake of every human being. Though they are positive traders for metabolism, excessive intakes bring about detrimental impacts on human health. Herein, the anti-cancer capacitive nature quercetin (Qc) was electrochemically detected through the rare earth metal-based sphere like praseodymium vanadate (PrVO4) entrapped graphitic carbon nitride (g-CN) as electrode modifiers. The nanocomposite was prepared by the one-pot hydrothermal method and characterized by phase compositional and morphology-based techniques. The existing synergistic nature between the PrV@g-CN (praseodymium vanadate@graphitic carbon nitride) makes them have an enhanced electrochemical response towards the Qc than the individual material. The obtained cyclic voltammogram and differential pulse voltammogram profile show one major oxidation peak which is attributed to the conversion of quercetin to quercetin-o-quinone. The PrV@g-CN/GCE (GCE- glassy carbon electrode) shows a good electrochemical active surface area (A = 110 cm2) and linear range between 0.05 and 252.00 μM with a LOD (limit of detection) of 0.002 µM. Moreover, the PrV@g-CN/GCE exhibits good current retention (94.76 %) around 14 days and appreciable repeatability (RSD- 0.5 %) and reproducibility (RSD- 1.3 %) towards the Qc. The real-time implementation of the proposed sensor exhibits a good recovery range towards the black tea (95.00–98.10 %) and green tea (97.80–99.60 %).

Supercapatteries as Hybrid Electrochemical Energy Storage Devices: Current Status and Future Prospects.

Among electrochemical energy storage (EES) technologies, rechargeable batteries (RBs) and supercapacitors (SCs) are the two most desired candidates for powering a range of electrical and electronic devices. The RB operates on Faradaic processes, whereas the underlying mechanisms of SCs vary, as non-Faradaic in electrical double-layer capacitors (EDLCs), Faradaic at the surface of the electrodes in pseudo-capacitors (PCs), and a combination of both non-Faradaic and Faradaic in hybrid supercapacitors (HSCs). EDLCs offer high power density but low energy density. HSCs take advantage of the Faradaic process without compromising their capacitive nature. Unlike batteries, supercapacitors provide high power density and numerous charge-discharge cycles; however, their energy density lags that of batteries. Supercapatteries, a generic term that refers to hybrid EES devices that combine the merits of EDLCs and RBs, have emerged, bridging the gap between SCs and RBs. There are numerous articles and reviews on EES, and many of those articles have emphasized various aspects of HSCs and supercapatteries. However, there are no recent reviews that dealt with supercapatteries in general. Here, we review recently published critically selected articles on supercapatteries. The review discusses different EES devices and how supercapatteries are different from others. Also discussed are properties, design strategies, and future perspectives on supercapatteries.

Dielectric analysis of surface modified nano-graphite: effects of frequency and thickness

The nano-graphite (NG) and acid modified nano-graphite (ANG) have been synthesized from graphite powder via mixture of strong acid (sulphuric acid and nitric acid) respectively by a soft chemistry route involving microwave, ultrasonic method and characterized by high-resolution electron microscopy (HR-TEM), scanning electron microscopy (SEM), fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), clearly demonstrated the successful synthesis of acid modified NG. SEM images confirmed the surface morphology of NG, and ANG and HR-TEM study shows the nanoparticles size of NG and ANG. FTIR data confirmed the presence of acid functional groups on the surface of synthesized NG powder. XRD data of NG and ANG shows that 2θ is at 26.43° and 0.336 nm is an interlayer distance (d). NG and ANG pellets have been prepared for their dielectric analysis with frequency for different thickness. The dielectric loss tangent (tanδ) spectra show relaxation peak with frequency and peak shifts due to presence of polar groups in the ANG. The capacitance values of NG and ANG decrease with frequency and increase with thicknesses due to the capacitive nature of nanoparticles. The dielectric permittivity decreases with frequency and increases with thickness due to the charge orientation and dipole moment change of functional groups of synthesized NG, and ANG. The electrical conductivity of NG and ANG nanoparticles increases with frequency and thickness of NG and ANG pellets due to the conductive nature. Electrical conductivity and dielectric permittivity of NG and ANG are found to highly rely on thickness, according to the dielectric evaluation.

A Comparative Cyclic Voltammetry Study of Amorphous Carbon-Transition Metal Oxide Hybrid System: Selection for the Best Capacitor

The present study addresses the synthesis of various amorphous carbon nanostructures-transition metal hybrid systems by a simple, low-temperature chemical route. Electron microscopic images of the pure and hybrid systems confirmed that different functionalized samples have significantly different morphologies. The Fourier-transformed infrared spectroscopic analysis provided ideas about different bonds present in all the samples, whereas the Raman spectra quantified the carbon content with different hybridization states. Thermal analysis confirmed that all the samples are thermally well-stable. Whereas energy dispersive X-ray was used to perform quantitative еlеmеntal analysisWhen cyclic-voltammetry (CV) and galvanostatic charge-discharge (GCD) studies of all the samples were performed, it was seen that among all the hybrids, the manganese-based system gave the best result with specific capacitance values over 530F/g.When Nyquist plots of all the samples were done in order to study the electrochemical impedance spectra, it was confirmed that the manganese based system shows the ideal capacitive nature with the lowest value of internal resistance. It was seen that when a-CNTs were functionalized with MnO2, the specific capacitance increased almost 7 times, whereas other samples gave much inferior results. Efforts have been made to explain the variation of the results from the point of view of the fundamentals of electrochemistry. It has been shown that the change in surface area, porosity, ion transport, and clustering of the foreign nanostructures are the key parameters behind the result.

Tungsten doping role in structural modification and boosting electrochemical efficiency of Co(OH)2 dandelion assemblies

Globally increasing energy demands and the drastic climate changes are pursuing cost-effective and environmental friendly energy storage option i.e. supercapacitors. Tungsten (W) doping in Co(OH)2 has played an effective role in morphology changes along with improving its super capacitive properties. The 5 % W-doped Co(OH)2 revealed perfectly dandelion assemblies having size range 3–4 µm and emerging wires with ∼10 nm diameter. These dandelion assemblies exhibited pseudocapacitive behavior and excellent specific capacitance 1000 Fg−1 at 1Ag−1 and 1051 Fg−1 at 5mVs−1 which is more than twice as compared to pristine Co(OH)2. Power law (b = 0.71) exhibited capacitive nature of 5 % W-doped Co(OH)2. High cyclic stability with 92 % charge retention have been achieved for 5000 cycles. This improved electrochemical performance is attributed to the high surface area with numerous active sites, amazing Faradaic redox reactions and excellent charge transfer rate. Hence, 5 % W-Co(OH)2 dandelion assemblies are promising electrode materials for efficient supercapacitors.

Effects of Heteroatom Doping and Physicochemical Character on the Electrochemical Properties of Graphene Sheets

AbstractGraphene attracted great interest in the electrochemical applications due to its stability and extremely high surface area‐to‐mass ratio. Wet chemical and electrochemical synthesis allow affordable and single to multilayer graphenes with functional groups that contribute to surface accessibility, and electrolyte diffusion. These materials also have faradaic and pseudocapacitive reaction sites which enhance the electrochemical performance while altering their capacitive nature based on reaction type and density of these sites. Therefore, heteroatom doping of graphene has been studied widely, and various outcomes, some of which have been controversial, were reported. In this study, we investigated the doping modification with multiple samples and also conduct a detailed physicochemical characterization. Oxidation‐reduction and electrochemical exfoliation methods were utilized to synthesize pristine, nitrogen‐doped, and phosphorus‐doped reduced graphene oxide as well as the phosphorus‐doped and pristine electrochemically exfoliated graphene materials. Samples have been characterized in terms of doping level, particle size, number of layers, defect density, and exfoliation homogeneity. Electrochemical measurements showed that surface wrinkling property among similarly large rGO particles (~9x) and small lateral particle size (~2x) of graphenes are effective in determination of specific capacitance (Cspecific) and capacitive characteristic of samples while heteroatom doping doesn't produce any significant change on these properties.