Cost-effective akermanite derived from industrial waste for working electrodes in supercapacitor applications

Abstract

The aim of this study is the synthesis of an akermanite (Ca₂MgSi₂O₇) material by sol–gel method using industrial waste (fly ash (FA) and ground-granulated blast furnace slag (GGBS)) as an initial precursor for the first time. In the present work, attention was paid to the temperature optimization of the structure executed in the temperature range from 700 °C to 1100 °C. The obtained powders were characterized by thermogravimetric and differential thermal analyses (TG/DTA), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, field emission-scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), photoluminescence (PL), and electrochemical studies such as cyclic voltammetry (CV), galvanic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The structural studies showed that the material exhibits a major phase of akermanite (Ca₂MgSi₂O₇) and a minor phase of diopside (Ca(Mg, Fe)Si₂O₆). The minor diopside phase was observed due to the inherently present Fe₂O₃ in the initial precursors FA and GGBS. The PL studies revealed that the deep red emission at 690 nm has occurred due to the ⁴T₁(⁴G) → ⁶A₁(⁶S) transition in ferric ions. The surface area of the electrode material for supercapacitor applications was calculated by the BET analysis and the adsorption pore size of the material was found to be 2.8 nm. The non-linear nature of discharge curves in electrochemical studies signifies the pseudocapacitive behaviour of the material. An attempt was made to fabricate a supercapacitor device for glowing a RED LED, and it showed that the prepared material exhibits a good response towards energy storage applications.