Jenni Lie, Hardy Shuwanto, Hairus Abdullah, Suryadi Ismadji, I.D.A.A. Warmadewanthi, Felycia Edi Soetaredjo
This work explores the utilization of coal fly ash (FA) for supercapacitor (SC) applications. Subcritical water extraction (SWE), a pressurized hydrothermal process, under acidic conditions was used to prepare FA as a SC electrode material; this is essential to remove the undesired compounds from FA powder as well as to improve its electrical conductivity. The effect of acid concentration in SWE process on the SC performance of the FA electrode was investigated. Characterizations such as galvanostatic charge-discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were carried out to determine the electrochemical properties of samples. The FA electrode with 0.5 M acid pretreatment in SWE (FA-0.5) resulted in the best performance of the SC. The specific capacitance (Cs), energy density (Ed), and power density (Pd) of FA-0.5 as an electrode are calculated to be 620 F g−1, 22 W h kg−1, and 500 W kg−1 at 2 A g−1, respectively, in 3 M KOH alkaline solution. The energy storage capability might originate from the contained silicon dioxide and metal oxides in the FA-0.5 sample. The demonstration of a full cell supercapacitor was also performed by assembling FA-0.5 and activated carbon (AC) as the cathode and anode, respectively. Under a current density of 2 A g−1, the asymmetrical FA-0.5//AC cell exhibits an Ed of 99 W h kg−1 and Pd of 1600 W kg−1 in the PVA-KOH gel electrolyte. This work provides an alternative valorization process to convert solid waste of coal FA by a novel SWE technique to an advanced energy storage application. © 2023 The Royal Society of Chemistry.
Department of Chemical Engineering, Widya Mandala Surabaya Catholic University, Kalijudan 37, Surabaya, 60114, Indonesia; Collaborative Research Center for Zero Waste and Sustainability, National Research and Innovation Agency, Indonesia; Science and Technology Innovation Center for Circular Economy and Green Innovative Resources, Taiwan, Indonesia; Department of Industrial Engineering, Universitas Prima Indonesia, Medan, Indonesia; Department of Environmental Engineering, Faculty of Civil, Planning, and Geo Engineering, Institut Teknologi Sepuluh Nopember. Kampus ITS Sukolilo, Surabaya, 60111, Indonesia