Large-scale synthesis and activation of polygonal carbon nanofibers with thin ribbon-like structures for supercapacitor electrodes

Abstract

Polygonal carbon nanofibers (PCNFs) were prepared on a large scale by chemical vapor deposition using Ni<inf>3</inf>Sn<inf>2</inf> intermetallic compound as a catalyst. The PCNFs feature polygonal cross sections with side lengths ranging from 200 nm to 400 nm, as primarily determined by the orthorhombic structure of the Ni<inf>3</inf>Sn<inf>2</inf> compound. The PCNFs were subsequently activated by KOH with different concentrations, denoted as a-PCNFs, for supercapacitor electrode applications. The PCNFs were significantly etched during the activation process under a high KOH concentration, forming a unique thin ribbon-like nanostructure with large specific surface area and high content of oxygen-containing functional groups. The electrochemical measurements reveal that a-PCNFs, activated by KOH at a KOH:C weight ratio of 4:1 under 800 °C, exhibit favorable electrochemical properties with a specific capacitance of 186 F g^-1 at a current density of 3 A g^-1 in 1 M Na<inf>2</inf>SO<inf>4</inf>, good rate capability, low internal resistance, and reasonably stable cycle life. These promising electrochemical properties indicate significant potential for use as scalable supercapacitor electrodes.