Mechanistic investigation of defect-engineered, non-stoichiometric, and Morphology-regulated hierarchical rhombus-/spindle-/peanut-like ZnCo2O4 microstructures and their applications toward high-performance supercapacitors

Self-assembled hierarchical rhombus-, spindle-, and peanut-like zinc cobaltite (ZnCo2O4, ZCO) microstructures have strategically engineered using an effective solvothermal approach. The various morphology-regulated ZCO samples have obtained by altering the concentration of precursors in the solvent. Effective strategic methods led to various regulated morphologies, as well as different physicochemical properties, such as the surface area/pore size/volume, crystalline nature, and non-stoichiometry of Zn and Co in the ZCO samples. The metal (Zn/Co)/O deficiencies have quantitatively estimated via X-ray photoelectron spectroscopy and confirmed by the Rietveld refinement of ZCO samples using X-ray diffraction data. A mechanistic study has performed to investigate the formation mechanism of the precursor concentration-dependent self-assembled ZCO microstructures. We demonstrate that the specific capacitance of ZCO has proportional to the Zn-deficiency/Co-excess. The Co-deficient-dependent electrochemical properties have studied for three samples and a decline in the following order: P-ZCO (1608.95 F g(-1) at 0.35 A g(-1)) > S-ZCO (1007.48 F g(-1) at 0.35 A g(-1)) > R-ZCO (629.05 F g(-1) at 0.35 A g(-1)). The simple and inexpensive method of synthesized non-stoichiometric ternary metal oxides micro/nanostructures will introduce new directions in this emerging energy field.