Highly Stable Electrochemical Supercapacitor Performance of Self-Assembled Ferromagnetic Q-Carbon

Abstract

Novel phase Q-carbon thin films exhibit some intriguing features and have been explored for various potential applications. Herein, we report the growth of different Q-carbon structures (i.e., filaments, clusters, and microdots) by varying the laser energy density from 0.5 to 1.0 J/cm 2 during pulsed laser annealing of amorphous diamond-like carbon films with different sp 3 −sp 2 carbon compositions. These unique nano-and microstructures of Q-carbon demonstrate exceptionally stable electrochemical performance by cyclic voltammetry, galvanostatic charging−discharging, and electrochemical impedance spectroscopy for energy applications. The temperature-dependent magnetic studies (magnetization vs magnetic field and temperature) reveal the ferromagnetic nature of the Qcarbon microdots. The saturation magnetization and coercive field values decrease from 132 to 14 emu/cc and 155 to 92 Oe by increasing the temperature from 2 to 300 K, respectively. The electrochemical performances of Q-carbon filament, cluster, and microdot thin-film supercapacitors were investigated by twoelectrode configurations, and the highest areal specific capacitance of ∼156 mF/cm 2 was observed at a current density of 0.15 mA/ cm 2 in the Q-carbon microdot thin film. The Q-carbon microdot electrodes demonstrate an exceptional capacitance retention performance of ∼97.2% and Coulombic efficiency of ∼96.5% after 3000 cycles due to their expectational reversibility in the charging−discharging process. The kinetic feature of the ion diffusion associated with the charge storage property is also investigated, and small changes in equivalent series resistance of ∼9.5% and contact resistance of ∼9.1% confirm outstanding stability with active charge kinetics during the stability test. A high areal power density of ∼5.84 W/cm 2 was obtained at an areal energy density of ∼0.058 W h/cm 2 for the Q-carbon microdot structure. The theoretical quantum capacitance was obtained at ∼400 mF/ cm 2 by density functional theory calculation, which gives an idea about the overall capacitance value. The obtained areal specific capacitance, power density, and impressive long-term cyclic stability of Q-carbon thin-film microdot electrodes endorse substantial promise in high-performance supercapacitor applications.

Tailoring the Perovskite Structure to Acquire an Inorganic La2NiCrO6 Double Perovskite as an Efficient Energy Storage Application by Varying Molar Concentrations of Citric Acid

“…The measured R s and R ct values of other samples are shown in Table S3. The straight line in the low-frequency region represents the capacitive behavior of the electrode material. − …”

Tubular Diamond as an Efficient Electron Field Emitter

“…The simulation was carried out until the force on an individual atom is less than 0.01 eV/Å and the plane wave cutoff energy is taken as 550 eV. Monkhorst–Pack grid of 5 × 5 × 5 K -points was used for relaxation, and to analyze the density of states, we used 7 × 7 × 7 K -points.…”

Unveiling Superior Capacitive Behaviors of One‐Pot Molten Salt‐Engineered B, N Co‐Doped Porous Carbon Sheets

“…As an importantly commercialized energy storage device, supercapacitors (SCs) constructed by activated carbons have high DOI: 10.1002/smll.202204119 power density, superior cycle life, and robust charge-discharge capacity. [1][2][3] Limited by the electrostatic adsorption mechanism, the carbon-based SCs always face low energy density. [4,5] Improving the ionaccessible sites through pore engineering is an effective method to improve the capacity and energy density of electric doublelayer capacitors (EDLCs).…”