Increase In Capacitance Research Articles

Textile PAN Carbon Fibers Cathode for High-Voltage Seawater Batteries

Rechargeable sodium seawater batteries (SWBs) are gaining the world leadership of high voltage energy storage devices for marine environments. With natural seawater as the source of active material, SWBs can be supplied infinitely with Na cations. Because of their open-structured cathode, the cathode material’s specific surface area, porosity and wettability need to be optimized to achieve a high-performance cell. In this work, activated textile polyacrylonitrile (PAN) fibers were used to produce an activated carbon felt with a facile manufacturing process. The easy and low-cost production of these fibers makes them excellent candidates for energy storage applications involving oxygen evolution and reduction reactions. The electrochemical performance results of the fabricated activated PAN fibers and of commercial carbon felts were measured and compared, being characterized through galvanostic charge discharge cycles, electrochemical impedance spectroscopy and cyclic voltammetries. A performance improvement was observed with PAN activated carbon felt as half cell with a capacitance increase (about 9000%), and as full cell with a smaller voltage gap (about 10%) and increased gravimetric capacitance (about 260%) when compared to the commercial carbon felt. The successful implementation of PAN activated carbon felts in an aqueous environment opens new paths toward high performance seawater battery’s cathodes.

Influence of Capping Agents on the Synthesis of Mn3O4 Nanostructures for Supercapacitors

Nanotechnology offers powerful strategies for the synthesis of advanced materials for supercapacitors. It is hypothesized that the size reduction of Mn3O4 nanoparticles can eliminate time-consuming electrochemical activation and increase the electrochemical pseudocapacitance of this material. Moreover, due to the redox properties and specific features of its chemical synthesis procedure, Mn3O4 can potentially outperform other promising cathode materials for energy storage in supercapacitors. A facile room temperature method to fabricate Mn3O4 nanoparticles is described, which is based on the application of advanced capping agents (CAs) for nanofabrication. Building on the strong adsorption power of the catechol ligand, we utilize tetrahydroxy-1,4-quinone, catechin, and gallocyanine as CAs for the preparation of Mn3O4. The use of the catecholate molecules as CAs for chemical precipitation facilitates the preparation of Mn3O4 platelet nanoparticles with a typical size of 5 nm. The reduction of the particle size allows the fabrication of advanced Mn3O4 multiwalled carbon nanotube cathodes with 40 mg cm–2 active mass (AM), which show a significant increase in capacitance in a 0.5 M Na2SO4 electrolyte. The highest capacitances of 7.03 F cm–2 (175.8 F g–1) at a potentiodynamic sweep rate of 2 mV s–1 and 9.13 F cm–2 (228.3 F g–1) at a constant current density of 3 mA cm–2 are obtained at a low impedance using gallocyanine as a CA. Obtained electrodes outperform MnO2-based cathodes of similar mass. Another important finding is the possibility to avoid the time-consuming activation process for Mn3O4-based electrodes. Analysis of the testing results provides evidence of the influence of the CA structure on the electrode performance. The results of this investigation pave the way for the application of Mn3O4 in advanced high-AM supercapacitor cathodes.

Effects of post-deposition annealing temperature and atmosphere on interface properties in ALD Al2O3/plasma oxidation GeO x /(111) and (100) n-Ge MOS structures

In this work, the effects of post-deposition annealing (PDA) on Al2O3/GeO x /(111) and (100) n-Ge structures are experimentally studied with changing annealing temperatures from 300 °C to 650 °C in a vacuum, N2 and O2 atmosphere in order to clarify the stability of the MOS interface properties under high-temperature annealing. A decrease in D it and an increase in the oxide capacitance with increasing PDA temperature is observed up to 500 ∼ 600 °C, depending on the annealing atmosphere and surface orientation. The minimum D it of ∼3 × 1011 eV−1cm−2 is achieved for (111) Ge after PDA at 550 °C and 600 °C in N2/O2 or vacuum. This trend is similar to the (100) MOS interfaces and a similar amount of minimum D it is obtained. These results suggest that the present Al2O3/GeO x /Ge interfaces are suitable for the formation of the Ge-On-insulator (GOI) back interfaces by the wafer bonding process in the Smart-cut, where high-temperature annealing is indispensable.

Corrosion, electrical and thermal behaviour of graphene modified polyester powder coatings

This work investigates polyester powder coatings containing graphene on aluminium alloy AA6060. The coatings were developed with a multifunctional approach in order to combine efficient barrier properties and high electrical and thermal conductivity. Graphene contents up to 10 wt% were introduced in the composite powder coatings. The barrier properties were investigated by means of electrochemical impedance spectroscopy (EIS) in 0.1 M NaCl solution. This technique was also employed to obtain information about the electrical parameters of the coatings. Although barrier properties remain high over immersion times up to 35 days, a strong increase of coating capacitance and a decrease of coating resistance were observed by EIS for the coatings with graphene content above 1 wt%. Impedance data were interpreted on the base of the electrical percolation theory in order to correlate the increase of capacitance and the decrease of the resistance to the existence of graphene-rich agglomerates in the composites coatings. Moreover, the thermal behaviour of the composite powder coatings was preliminarily evaluated indicating that the introduction of graphene can improve heat dissipation.

The structure analysis and chemical properties probing during recycling processes of transition metal dichalcogenides exfoliation

Transition metal dichalcogenides (TMDs) have attracted much attention in electrochemistry due to their outstanding properties; however, there is a limit to the production of TMDs samples on a large scale. In this work, we have demonstrated the recycling process of TMDs materials using WSe2 as a representative of the TMDs family. WSe2 nanoflakes were synthesised by solvent-assisted liquid phase exfoliation through sonication of “bulk” WSe2. It has been found that the unexfoliated WSe2 can be recycled up to 6 times, this improve the production yield. The physical and chemical properties of the exfoliated WSe2 nanoflakes were investigated during the recycling processes. Interestingly, the recycling processes (number of recycling times) directly affect the flake sizes, and surface chemistry of the exfoliated samples. The obtained flake size decreases from about 1 μm to less than 200 nm (from 1st to 7th exfoliation), the diminished of sample thickness has also been found. Besides, the local structure of WSe2 remains unchanged, showing the W4+ oxidation state of WSe2, which to the best of our knowledge. The applicability of the as-recycled samples were then demonstrated as bi-functional electrode materials: (i) supercapacitor, (ii) and electrocatalyst (for hydrogen evolution reaction). From 1st to 7th exfoliation, the electrochemical performance improves about 1-fold (capacitance increase from 3 to 6 F g−1, and the overpotential at 10 mA cm−2 improves from -0.67 to -0.42 vs. RHE). This study provides an alternative way to improve the synthesis method, which can not only utilise “waste” but also recover the production yield of TMDs leading to the continued development of 2D materials, and related families.

Carbon matrix nanostructured composites as a new type of supercapacitor electrode materials

Carbon matrix nanocomposites C / Au and C / MnxOy are obtained by a reduction of HAuCl4 and KMnO4 precursor solutions with single-walled carbon nanotubes or highly porous carbon materials obtained by high-temperature alkaline activation of various metamorphism degree coals. The morphology of the nanocomposite materials is studied by the electron microscopy. It is found that the filler introduction slightly reduces the specific surface of matrices and, due to the blocking of meso- and micropore volumes, filler nanoparticles do not precipitate in the pores of a predominantly microporous matrix and partially decorate them in mixed-type matrices (meso- and micropores). Nanocomposites have been studied as supercapacitor electrode materials. It is established that decorating the matrix surface with both types fillers (Au, which increases the electrical double layer capacitance, and MnxOy, which is electrochemically active in a given potential window due to the occurrence of Red-Ox electrode processes) results in an increase in the supercapacitor electrodes capacitance. The most significant effect is observed for composites based on the SWCNT and highly porous Boghead in the region of high potential scan rates by a factor of 3.4 – 4.5, and in the region of low rates (2.5 – 2.8), depending on the filler. The results obtained allow one to consider the composites C / Au and C / MnxOy as promising materials for the development of SC electrodes.

In Situ Raman Study of Voltage Tolerance Up to 2.2 V of Ionic Liquid Analogue Supercapacitor Electrolytes Immune to Water Adsorption Conferred by Amphoteric Imidazole Additives.

Ionic liquid analogues (ILAs) are promising electrolytes for supercapacitors due to their low cost and considerable voltage (>2.0 V). However, the voltage is <1.1 V for water-adsorbed ILAs. Herein for the first time, an amphoteric imidazole (IMZ) additive is reported to address this concern by reconfiguring the solvent shell of ILAs. Addition of only 2 wt % IMZ increases the voltage from 1.1 to 2.2 V, with an increase in capacitance from 178 to 211 F g-1 and an increase in energy density from 6.8 to 32.6 Wh kg-1. In situ Raman reveals that the strong H-bonds formed by IMZ with completive ligands 1,3-propanediol and water induce a reversal of the polarity of the solvent shells, suppressing absorbed water electrochemical activity and thus increasing the voltage. This study solves the problem of low voltage for water-adsorbed ILAs and reduces the equipment cost of ILA-based supercapacitor assembly (e.g., assembly in air without a glovebox).

Experimental and Molecular Dynamic Modeling Studies of Electrospun Carbon Fiber Electrode Performance Enhancement by Potassium Ferricyanide Addition

In this work, we convert coal extraction waste into functional carbon fiber electrodes. Detailed experimental and modeling studies reveal the importance of surface properties and dramatic increase (162%) in capacitance with adding small amount of 0.01 M K3Fe(CN)6 to 6 M KOH (referred to as mixed electrolyte). Molecular dynamics (MD) modeling reveals that ferricyanide ions in the mixed electrolyte contributed to the increase of both pseudocapacitance and electric double layer capacitance. With the mixed electrolyte, a symmetric supercapacitor (SSC) using coal-derived carbon fiber mat electrodes can deliver energy density as high as16.8 Wh kg–1 at a power density of 362.2 W kg–1, with excellent cycling stability (∼95.83% at 10,000 cycles). This study provides an insightful perspective on the strategic efforts of nonthermal usage of coal as we transition to renewable energy economy. Additionally, the mixed electrolyte effect and MD modeling results shed light on carbon electrodes from biomass, such as lignin, for various electrochemical energy devices.

Employing Redox‐Active Additives for Enhanced Charge Polarization and Twofold Higher Energy Density in Supercapacitor

AbstractRemarkable improvement in the polarization and charge transport at the solid–solid electrode–electrolyte interface due to the incorporation of a redox‐active additive sodium molybdate (Na2MoO4) is demonstrated. The presence of the electrochemically active oxide center along with Na+facilitates the hopping‐based charge transport of the ionic liquid leading to higher ionic conductivity and a twofold increase in specific capacitance (0.009 to 0.018 F cm−2). This drives a 200% increase in the energy density (0.76–1.7 µW h cm−2) and a 2.5 times improvement in the rate capability (10 000 mV s−1) of the solid‐state supercapacitor. Importantly, the power density, non‐Faradic nature, and cyclability remain unaltered, resulting in performance exceeding several solid‐state and liquid electrolyte‐based supercapacitors. Thus, the results established here through the use of redox‐active additive establish the robustness of the approach and practicality of the resulting device besides providing transformative opportunities in tuning the performance of solid‐state devices.

Salt-Induced Doping and Templating of Laser-Induced Graphene Supercapacitors

The use of inexpensive and widely available CO2 lasers to selectively irradiate polymer films and form a graphene foam, termed laser-induced graphene (LIG), has incited significant research attention. The simple and rapid nature of the approach and the high conductivity and porosity of LIG have motivated its widespread application in electrochemical energy storage devices such as batteries and supercapacitors. However, nearly all high-performance LIG-based supercapacitors reported to date are prepared from costly, petroleum-based polyimide (Kapton, PI). Herein, we demonstrate that incorporating microparticles of inexpensive, non-toxic, and widely abundant sodium salts such as NaCl and Na2SO4 into poly(furfuryl alcohol) (PFA) resins enables the formation of high-performance LIG. The embedded particles aid in carbonization and act as a template for pore formation. While increasing both the carbon yield and surface area of the electrodes, the salt also dopes the LIG formed with S or Cl. The combination of these effects results in a two- to four-order-of-magnitude increase in device areal capacitance, from 8 μF/cm2 for PFA/no salt at 5 mV/s to up to 80 mF/cm2 for some PFA/20% Na2SO4 samples at 0.05 mA/cm2, significantly higher than that of PI-based devices and most other LIG precursors.

Tracking surface ionic movement of Ni3S2@CuS electrode materials with high electrochemical performance

Supercapacitors have overwhelming advantages in cycle life, charging time and power density. Metal sulfides involve reversible Faraday redox reactions, and chemical reactions occur during charge and discharge, resulting in high specific capacity of the electrode. Different from the traditional nickel foam as a current collector, in this work, vulcanized nickel foam (Ni3S2) is used to further grow CuS nanosheets by hydrothermal reaction to produce new cathode material. The results show that the electrochemical properties of the electrode material Ni3S2@CuS obtained at 190 °C for 4 h reach a mass specific capacity of 967.7F/g. When assembled as a supercapacitor device, it has an energy density of 103.7 Wh/kg and a power density of 15050.3 W/kg. The coulomb efficiency of the device remains 97.4 % after 10,000 cycles of constant current charge and discharge. To deeply understand the mechanism of the capacitance increase, we carry out a molecular dynamics (MD) simulation on pure Ni3S2 electrode and Ni3S2@CuS to investigate the influence of this unique structure on capacitance for the first time. We discover that the CuS tunnel on the Ni3S2 electrode surface will restrict the deintercalation of K+ ions and promote the intercalation of OH–, and this phenomenon will promote the reversible redox reaction on the surface of the metal sulfides and enhance the capacitance of this pseudocapacitor.

Structural, morphological and electrochemical characterization of the degradation processes during the oxygen reduction reaction of iron(II) phthalocyanine supported on carbon nanotubes

A non-noble metal catalyst (Fe-Nx@MWCNTs), which was prepared by wet impregnation of surface-functionalized multi-walled carbon nanotubes (MWCNTs) with iron(II) phthalocyanine (FePc) and heat treatment, as well as the functionalized MWCNTs without FePc were examined towards their performance for the oxygen reduction reaction (ORR) in neutral media and their structural properties during electrochemically forced degradation. Electroanalytical methods as well as in situ-Raman microscopy and ex situ-X-ray photoelectron spectroscopy (XPS) were applied at different levels of a two-stage accelerated stress test (AST). In particular, the comparability between the electrochemical, the in situ-Raman and the ex situ-XPS setup was confirmed. It was found that the iron central atom was leached out of the Fe-Nx-complex during the first stage of the AST causing a decline of ORR activity, still higher than that of the MWCNT support, which remained unaffected. During the second stage, the samples were subjected to stronger electrochemical stress by cycling to highly positive potentials, causing the formation of surface groups and an increase of double layer capacitance. The high potentials also destroy remaining catalytic NC moieties and the ORR activity of the catalyst approaches that of the bare support. With ongoing AST cycling, the overall current of the samples is heavily reduced which is attributed to loss of electric conductivity of the sample backbone by further oxidation.

Hydrodynamic cavitation-assisted preparation of porous carbon from garlic peels for supercapacitors

Hydrodynamic cavitation (HC), which can effectively induce sonochemical effects, is widely considered a promising process intensification technology. In the present study, HC was successfully utilized to intensify the alkali activation of GPs for SCs, for the first time. Five BDCMs were synthesized following the method reported in the literature. For comparison, four more BDCMs with HC-treated, among which a sample was further doped with nitrogen during the HC treatment, were prepared. Then all the samples were compared from microscopical characteristics to electrochemical performance as SCs materials. The morphology study demonstrated that the HC treatment had created many defects and amorphous carbon structures on the GP-based BDCMs, with the highest SSA reaching 3272 m2/g (1:6-HCGP), which 32 folded that of the Raw carbon sample’s. The HC treatment also intensified the N-doping process. XRD and XPS results manifested that the N content had been increased and consequently changed the electronic structure of the carbon atoms, leading to the increase of specific capacitance (1:6-HCGP+N-based SC, 227 F/g at 10 A/g). The cycle performance proved that the GP-based BDCMs have long-term stability, indicating that the HC-treated BDCMs were good choices for energy storage technologies. Compared with the ultrasound-assisted method, which may have a high energy density, the HC-assisted method enables high production and energy efficiency. This work is a first time attempt towards the industrial application of HC method in energy-related materials synthesis and encourages more in-depth studies in the future.

Electrochemical characterization of Ti3C2Tx MXene prepared via a molten salt etching route in an acetonitrile-based electrolyte

Two-dimensional metal carbide and nitride materials (MXenes) with controlled Cl- and O-surface terminations (MS-Ti3C2Tx) were prepared by a molten salt etching route and their electrochemical properties were investigated in nitrile-based electrolytes. The results show that the power performance of MS-Ti3C2Tx was greatly improved in acetonitrile (ACN)-based non-aqueous organic electrolytes, which are conventional electrolytes for electrochemical capacitors. The addition of a lithium salt to produce 2 M LiTFSI in ACN results in an increase in the specific capacitance. Moreover, replacing LiTFSI by LiFSI drastically improves the power performance of MXenes at a high scan rate (95 mAh g−1 at 900C). These results highlight the importance of properly matching the electrolyte composition to the electrode material and shed light on MXenes as high-rate electrode materials for energy storage applications.

Battery Cycle Stability in Additive-free MAX(Ti3AlC2) Li-ion Battery Anode

We fabricated an additive-free MAX(Ti3AlC2) phase Li-ion battery (LIB) electrode using the electrophoretic deposition (EPD) method. In this study, MAX, a precursor of MXene, which has recently been receiving great attention as a negative electrode material for LIBs, was manufactured as a coin cell through EPD rather than the conventional slurry system. We excluded the effect of additives on the electrochemical performance, enabling evaluation of the intrinsic electrochemical properties related to battery charging and discharging. As a result, the battery using MAX as an anode material showed a large specific capacity of 148.2 mAh/g in the first discharge and superior cycle stability. Enhanced cycle stability and reversible electrochemical reactions were attributed to activation of faradaic and non-faradaic behavior, i.e., pseudocapacitive behavior, caused by delamination of the MAX(Ti3AlC2) into MXene (Ti3C2). This was confirmed by the decrease in the charge transfer resistance and the increase in total capacitance at the interface, using electrochemical impedance spectroscopy and cyclic voltammetry measurements. In addition, the activation of pseudocapacitive behavior was confirmed by the change in kinetic mechanism, as evidenced from a significant increase in the Li ion diffusivity with cycles. These results demonstrate that MAX(Ti3AlC2) is promising as an anode material for LIBs and at the same time shows potential for tuning electrochemical properties through the electrochemical delamination process.

Closed-Pore Formation in Oxygen Electrodes for Solid Oxide Electrolysis Cells Investigated by Impedance Spectroscopy.

Electrochemical impedance spectroscopy was used to investigate the chemical capacitance of La0.6Sr0.4CoO3-δ (LSC) thin-film electrodes under anodic polarization (i.e., in the electrolysis mode). For this purpose, electrodes with different microstructures were prepared via pulsed-laser deposition. Analysis of dense electrodes and electrodes with open porosity revealed decreasing chemical capacitances with increasing anodic overpotentials, as expected from defect chemical considerations. However, extremely high chemical capacitance peaks with values in the range of 104 F/cm3 at overpotentials of >140 mV were obtained after annealing for several hours in synthetic air and/or after applying high anodic bias voltages of >750 mV. From the results of several surface analysis techniques and transmission electron microscopy, it is concluded that closed pores develop upon both of these treatments: (i) During annealing, initially open pores get closed by SrSO4, which forms due to strontium segregation in measurement gases with minute traces of sulfur. (ii) The bias treatment causes mechanical failure and morphological changes including closed pores in the bulk of dense films. Under anodic polarization, high-pressure oxygen accumulates in those closed pores, and this causes the capacitance peak. Model calculations based on a real-gas equation allow us to properly predict the experimentally obtained capacitance increase. We demonstrate that analysis of the chemical capacitance of oxygen electrodes in solid oxide electrolysis cells can thus be used as a nondestructive observation tool to detect and quantify closed porosity with a lower detection limit between 10-4 and 10-3.

A Study of Phase-Adjusting Architectures for Low-Phase-Noise Quadrature Voltage-Controlled Oscillators

Quadrature voltage-controlled oscillators (VCOs) with current-weight-average and voltage-weight-average phase-adjusting architectures are studied. The phase adjusting equalizes the oscillation frequency to the LC-resonant frequency. The merits of the equalization are explained by using Leeson's phase noise equation and the impulse sensitivity function (ISF). Quadrature VCOs with the phase-adjusting architectures are fabricated using 180-nm TSMC CMOS and show low-phase-noise performances compared to a conventional differential VCO. The ISF analysis and small-signal analysis also show that the drawbacks of the current-weight-average phase-adjusting and voltage-weight-average phase-adjusting architectures are current-source noise effect and large additional capacitance, respectively. A voltage-average-adjusting circuit with a source follower at its input alleviates the capacitance increase.

Analysis on electric impedance-controlled active ultrasonic horn in radial vibration

As a key component of high-powered ultrasonic vibration systems, ultrasonic horns play an important role in various practical application scenarios. Recent advances in longitudinal ultrasonic horns have enabled them to magnify the Langevin transducer's mechanical vibration and efficiently transmit the mechanical vibration to the mechanical load. However, limited research has been devoted to active radial ultrasonic horns in radial vibration. Here we propose an electric impedance-controlled active radial ultrasonic horn (ARUH) capable of tuning both resonance frequency and displacement magnification in radial vibration. The resulting device consists of a radially polarized piezoelectric ring connected with adjustable electric impedance and two metal rings with variable sections. The underlying mechanism is that the change of the converted mechanical impedance of the piezoelectric material by the external electric impedance connected to the piezoelectric material modulates the resonance frequency and displacement magnification of the ARUH. It can be found that the resonant frequency shifts to higher frequencies as the resistance increases and the resonant frequency shifts to lower frequencies as the inductance and capacitance increase, while the displacement magnification has the opposite trend to the resonance frequency. For example, the resonance frequency of the constant-section radial horn is 41130.2 Hz. When the inductance increases from −0.007 to 0.007H, the resonance frequency shifts from 41171.3 to 34606.2 Hz and the displacement magnification moves from 1.189 to 3.5. The experiments are conducted to verify the effectiveness of the resulting device, which is in good agreement with the simulated results and theoretical predictions. Our design with functionality and flexibility opens up possibilities for the design of ARUHs and may find important application prospects in diverse fields such as cold-drawn steel tubes and ultrasonic plastic welding.

Changes in Electrical Capacitance of Cell Membrane Reflect Drug Partitioning-Induced Alterations in Lipid Bilayer

The plasma membrane is a lipid bilayer that establishes the outer boundary of a living cell. The composition of the lipid bilayer influences the membrane's biophysical properties, including fluidity, thickness, permeability, phase behavior, charge, elasticity, and formation of flat sheet or curved structures. Changes in the biophysical properties of the membrane can be occasioned when new entities, such as drug molecules, are partitioned in the bilayer. Therefore, assessing drugs for their effect on the biophysical properties of the lipid bilayer of a cell membrane is critical to understanding specific and non-specific drug action. Previously, we reported a non-invasive technique for real-time characterization of cellular dielectric properties, such as membrane capacitance and cytoplasmic conductivity. In this study, we discuss the potential application of the technique in assessing the biophysical properties of the cell membrane in response to interaction with amiodarone compared to aspirin/acetylsalicylic acid and glucose. Amiodarone is a potent drug used to treat cardiac arrhythmia, but it also exerts various non-specific effects. Compared to aspirin and glucose, we measured a rapid and higher magnitude increase in membrane capacitance on cells under amiodarone treatment. Increased membrane capacitance induced by aspirin and glucose quickly returned to baseline in 15 s, while amiodarone-induced increased capacitance sustained and decreased slowly, approaching baseline or another asymptotic limit in ~2.5 h. Because amiodarone has a strong lipid partitioning property, we reason that drug partitioning alters the lipid bilayer context and subsequently reduces bilayer thickness, leading to an increase in the electrical capacitance of the cell membrane. The presented microfluidic system promises a new approach to assess drug-membrane interactions and delineate specific and non-specific actions of the drug on cells.

Efficient Oxygen Doping of Graphitic Carbon Nitride by Green Microwave Irradiation for High-Performance Supercapacitor Electrode Material

A highly efficient microwave irradiation method was employed for doping oxygen into the g-C3N4 framework using H2O2, which entailed 10 min compared to energy- and time-intensive calcination and hydrothermal methods. HR-XPS revealed that O doping preferentially occurred through replacement of two coordinated N atoms of the triazine units. The effects of the ensuing electronic structure modulation were investigated with electrochemical tests where the metal-free catalyst displayed a specific capacitance of 262.5 F/g at a 1 A/g current density and a satisfactory capacitance retention of 73.17% at 6 A/g after 2000 cycles, which is comparable to those of various metals containing g-C3N4-based catalysts. The designed asymmetric supercapacitor device revealed a specific energy of 36.45 Wh/kg at a specific power of 2.5 kW/kg. The microwave-irradiated O-doped g-C3N4 showed an 8-fold increase in specific capacitance compared with bulk g-C3N4 in both CV and GCD analyses. The improved surface structure and O content enhanced the electrode–electrolyte contact area, thus making ion transfer highly efficient for EDLCs. These results also opened the potential of microwave-synthesized O-doped g-C3N4 as a base material for designing binary and ternary electrode materials.