Tailoring cobalt doped zinc oxide nanocrystals with high capacitance activity: Factors affecting structure and surface morphology

Highly crystalline zinc cobaltite (ZnCo ₂O ₄) nanocrystals were successfully synthesized through an epoxide driven, sol-gel method using Zn(NO ₃)·6H ₂O and CoCl ₂·6H ₂O 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 m ² 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.