Biomass-derived porous carbon electrode modified with nanostructured nickel-cobalt hydroxide for high-performance supercapacitors

Apple-derived porous carbon (denoted as APC) is successfully prepared and analyzed as a potential carbon material by hydrothermal carbonization and pyrolysis, which exhibits a high specific surface area and porous structure. Furthermore, nickel–cobalt double hydroxide (Ni–Co DH) is synthesized by design of hybrid nanowires on APC for supercapacitors via a simple hydrothermal process. The fabricated electrode produces a capacitance of 1519 F g−1 at 1 A g−1, and 90.2% of the capacitance is retained after 2000 cycles at a high current density. An asymmetric supercapacitor (ASC) is assembled using the Ni–Co DH@APC as the positive electrode and active carbon as the negative electrode. The ASC exhibits a prominent energy density of 61.2 Wh kg−1 and high power density of 14,400 W kg−1 at 5 A g−1. The desirable electrochemical performance can be attributed to the suitability of APC as a support and the Ni–Co nanostructure constructed on the surface of APC as an effective active material for high-energy and long-life cycling supercapacitor applications. The fabricated composite provides a potential design of low-cost functional carbon materials that can be produced in large scale by using biomass as starting materials.