Utilization of ZnO–MgO derived from ferrochrome ash waste as a supercapacitor electrode material

Abstract The present study involved the production of a novel hybrid supercapacitor electrode material ZnO–MgO from ferrochrome ash (FCA) waste using a hydrometallurgical method for the first time in the literature. FCA was initially leached with H 2 SO 4 solutions with varying concentrations and leaching durations at the solid:liquid ratio of 100 g/L. The optimal leaching parameters were determined as 1-M H 2 SO 4 concentration and 60 min, which resulted with the 91.35% of Zn and 31.69% of Mg leaching efficiency. Afterward, the leached ions were precipitated as hydroxides by pH adjustment. Obtained precipitates were subsequently calcined at 500, 750, and 1000 °C to obtain three different ZnO–MgO hybrid materials with various morphological and electrochemical properties. The obtained materials were employed as electrode materials in coin cell-type asymmetric supercapacitors, and the electrochemical performance of the supercapacitors were assessed using CV, GCD, and EIS analyses. The supercapacitor containing the anode calcined at 750 °C exhibited the highest specific capacitance value as 486 mF cm −2 at a scan rate of 10 mV cm −2 and retained 93% of its initial capacitance after 5000 GCD cycles at the current density of 0.5 mA cm −2 .