Four-stage chemical treatment of spent pot lining carbon for titanium oxide doped high performance supercapacitor electrode material

Abstract

Obtaining carbon materials in a sustainable way and applying them in energy storage systems is attracting more attention. Spent potlining (SPL) which is a carbon-rich waste produced in electrolytic cells of aluminium smelters can be a potential source of carbon for engineering applications. However, SPL is hazardous in nature and needs to undergo chemical treatment for most engineering applications. In this study, a four-step procedure was adopted to remove sodium fluoride (NaF), cryolite (Na3AlF6), alumina (Al2O3), calcium fluoride (CaF2), sodium aluminate (NaAl11O17) and silica (SiO2) from the SPL. The adopted treatment processes proved effective as Energy Dispersive X-ray (EDX) and X-ray Diffraction (XRD) results showed no traces of the major impurities after the treatment. The treated carbon-rich SPL was activated using NaOH to obtain activated SPL (ASPL). The ASPL was doped with TiO2 to form ASPL-TiO2 (1:1), ASPL-TiO2 (3:1) and ASPL-TiO2 (2:1) electrodes. The electrode materials were tested using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The ASPL, ASPL-TiO2 (1:1), ASPL-TiO2 (3:1) and ASPL-TiO2 (2:1) demonstrated specific capacitance of 180.2 F/g, 279.1 F/g, 536.7 F/g, and 203.2 F/g at 10 A/g respectively with high stability over 1000 cycles. The present study was designed to determine the suitability of using chemically treated SPL as an alternative source of carbon for supercapacitor applications and this was achieved as the material exhibited an improved charge storage capacity.

Keywords

• Spent potlining
• Leaching
• Impurities
• Supercapacitor
• Titanium oxide
• Electrochemical analysis