Tailoring cobalt doped zinc oxidenanocrystals with high capacitance activity: factors affecting structure and surface morphology

Abstract

Highly crystalline zinc cobaltite (ZnCo₂O₄) nanocrystals were successfully synthesized through an epoxide driven, sol–gel method using Zn(NO₃)·6H₂O and CoCl₂·6H₂O as precursors. The crystal phase, morphology, specific surface areas, porosity, and capacitance activity of the prepared materials were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), gas sorption techniques, and cyclic voltammetry, respectively. Results reveal that the synthesized nanocrystals are ∼4 nm in diameter. Electron microscopy studies illustrate significant changes brought on by varying the solvent and epoxide. Gas sorption analyses detail high specific surface areas (>200 m² g⁻¹) and porosities of the as prepared and annealed samples. Cyclic voltammetry experiments show that these zinc cobaltite nanocrystals have exceptional capacitance (∼700 Fg⁻¹) and excellent cycle durability making them an excellent electrode material for supercapacitors.