Tailoring NiO-SrCO₃ nanocomposites via fuel-controlled combustion synthesis for enhanced supercapacitor performance

Abstract

The electrochemical performance of transition metal oxide (TMO)-based supercapacitor electrodes depends on the morphology, composition, crystal structure, and porosity of the TMO nanoparticles. Solution combustion synthesis offers a versatile approach in tailoring these physical and electrochemical properties, as the characteristics of the resulting nanoparticles are influenced by the choice of fuel used in the process. In the current study, we investigated the influence of different fuels-citric acid, urea, and glucose-on the morphology, composition, crystal structure, and functionality of nickel oxide-strontianite nanocomposites synthesised via solution combustion method. The X-ray diffraction investigations confirmed the formation of nanocomposite consisting cubic phase of NiO along with the orthorhombic phase of SrCO 3 . Variations in the type of fuel employed during the synthesis lead to notable changes in particle morphology and size distribution. These structural differences profoundly impact the electrochemical properties of the synthesized materials. Electrochemical performance was assessed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in a three-electrode system with 1M KOH electrolyte. The electrodes were fabricated by drop casting the nanoparticles over the Toray carbon sheet. The sample prepared using urea as a fuel exhibited the highest specific capacitance of 131.89 F/g. The redox peaks confirmed a pseudocapacitive charge storage mechanism, involving both faradaic reactions and electrical double-layer capacitance, where an increase in pseudocapacitance (C Pseudo ) directly enhances energy storage efficiency. Trasatti's analysis carried out using CV data recorded at different scan rates reveals that among the electrodes, the one fabricated using citric acid-synthesised nanoparticles (NiO-SrCO 3 -@Citric acid) shows the lowest C Pseudo contribution at 71.1%, followed by the NiO-SrCO 3 -@Glucose at 90.5%, while the NiO-SrCO 3 -@Urea offers the highest pseudocapacitance of 94.8%. The study demonstrates that the nanocomposite, particularly those synthesised with urea, hold promise as efficient electrode materials for supercapacitors.