Synergistic Effect of 2D Cu x S y Nanoflakes and a PVA/Phytic Acid-Derived Porous Carbon Heterostructure for Enhanced Supercapacitor Performance

Abstract

Porous heterostructure platforms prepared by the combination of a mixed phase of 2D copper sulfide nanoflakes (CSNF) and a phosphorus-doped porous carbon (PC) are found to act as efficient electrode materials. CSNF has been synthesized from Cu(NO3)2·3H2O using a hydrothermal process, whereas PC has been produced by the carbonization of poly(vinyl alcohol)-phytic acid (PVA–PA) film obtained by an ultrasonic method. The amount of phosphorus doping in PC was ca. 2.6 atom%. An optimized amount of CSNF and PC mixed together in a weight ratio of 1:2 gave CSNF@PC-2 with a surface area of 138 m2 g–1 and specifically exhibited better properties over the other samples. The specific capacitance of CSNF@PC-2 is found to be 467 F g–1 at a current density of 1 A g–1 in 1 M H2SO4, with a Coulombic efficiency of 93.2%. It also displays a cyclic stability with a 90% retention of its initial capacitance after 5000 cycles of charge/discharge at 30 A g–1. This electrode material demonstrates a good energy density of 52.53 Wh kg–1 and a power density of 450.32 W kg–1 at a current density of 1 A g–1. A symmetric device prepared with the material (CSNF@PC-2//CSNF@PC-2) delivers a specific capacitance of 194.67 F g–1 at a current density of 0.2 A g–1, and after 1000 GCD cycles retains ca. 54.1% of its specific capacitance with a Coulombic efficiency of up to 120%. When three symmetric devices with an overall mass loading of 4 mg cm–2 are connected in a series to form a circuit, it can light up a 3 V green light-emitting diode (LED) bulb, which can be recharged and reused, revealing the long-term energy storage capability of CSNF@PC-2.