Preparation and characterization of a pseudocapacitor electrode by spraying a conducting polymer onto a flexible substrate

Biomimetic Synthesis of PANI/Graphitic Oxidized Carbon Nitride for Supercapacitor Applications

Polyaniline (PANI) composites have gained momentum as supercapacitive materials due to their high energy density and power density. However, some drawbacks in their performance remain, such as the low stability after hundreds of charge-discharge cycles and limitations in the synthesis scalability. Herein, we report for the first time PANI-Graphitic oxidized carbon nitride composites as potential supercapacitor material. The biomimetic polymerization of aniline assisted by hematin, supported by phosphorous and oxygen-modified carbon nitrides (g-POCN and g-OCN, respectively), achieved up to 89% yield. The obtained PAI/g-POCN and PANI/g-OCN show enhanced electrochemical properties, such as conductivity of up to 0.0375 S/cm, specific capacitances (C_s) of up to 294 F/g (at high current densities, 5 A/g) and a stable operation after 500 charge-discharge cycles (at 3 A/g). In contrast, the biomimetic synthesis of Free PANI, assisted by stabilized hematin in cosolvents, exhibited lower performance properties (65%). Due to their structural differences, the electrochemical properties of Free PANI (conductivity of 0.0045 S/cm and C_s of up to 82 F/g at 5 A/g) were lower than those of nanostructured PANI/g-POCN and g-OCN supports, which provide stability and improve the properties of biomimetically synthesized PANI. This work reveals the biomimetic synthesis of PANI, assisted by hematin supported by modified carbon nitrides, as a promising strategy to produce nanostructured supercapacitors with high performance.

Controllable Morphology of Sea-Urchin-like Nickel-Cobalt Carbonate Hydroxide as a Supercapacitor Electrode with Battery-like Behavior

Nickel-cobalt carbonate hydroxide with a three-dimensional (3D) sea-urchin-like structure was successfully developed by the hydrothermal process. The obtained structure enables the enhancement of charge/ion diffusion for the high-performance supercapacitor electrodes. The mole ratio of nickel to cobalt plays a vital role in the densely packed sea-urchin-like structure formation and electrochemical properties. At optimized nickel/cobalt mole ratio (1:2), the highest specific capacitance of 950.2 F g^-1 at 1 A g^-1 and the excellent cycling stability of 178.3% after 3000 charging/discharging cycles at 40 mV s^-1 are achieved. This nickel-cobalt carbonate hydroxide electrode yields an energy density in the range of 42.9-15.8 Wh kg^-1, with power density in the range of 285.0-2849.9 W kg^-1. The charge/discharge mechanism at the atomic level as monitored by time-resolved X-ray absorption spectroscopy (TR-XAS) indicates that the high capacitance behavior in a nickel-cobalt carbonate hydroxide is mainly dominated by cobalt carbonate hydroxide.