Hydrothermal growth of 2D AlOOH nanoflakes with semi-green approach towards solid-state symmetric supercapacitor

Abstract

Metal oxyhydroxides with 2D nanostructures have recently gained significant momentum for supercapacitor application due to their remarkable electrochemical properties. This work demonstrates the electrochemical performance of Al-based oxyhydroxide (AlOOH) electrode for supercapacitor application. AlOOH nano powder has been prepared using the hydrothermal approach without using any surfactants or organic bases in double distilled water as a solvent with semi semi-green synthesis approach. The crystal structure and bonds present in the synthesized sample are characterized by X-ray diffraction and fourier transform infrared spectroscopy respectively. The 2D nanoflakes-like surface architecture of AlOOH is revealed by scanning and transmission electron microscopy as well as atomic force microscopy. The AlOOH electrode exhibits the highest specific capacitance of 891 F g⁻¹@4.7 A g⁻¹ in 3 M KOH electrolyte. It also shows a 100 % coulombic efficiency after 4000 charge-discharge cycles. Furthermore, A prototype, symmetric supercapacitor device has been assembled using a 3 M KOH-PVA gel electrolyte. The fabricated device delivered the highest energy and power densities of 6.53 Wh kg⁻¹ and 2555 W kg⁻¹ having ∼85.71 % stability after 6000 GCD cycles. The AlOOH device is able to illuminate various coloured LEDs for varying durations after only 60 s of charging. The 2D AlOOH nanoflakes displays encouraging results, suggesting that it could be a useful energy storage material.