Formation of surfaces oxide vacancies in porous ZnCo₂O₄ nanoflowers for enhanced energy storage performance

A cost-effective and large-scale method for synthesizing ZnCo₂O₄ nanoflowers with surface oxygen vacancies as electrode materials for supercapacitors is presented. The existence of oxygen vacancies on the surface of the ZnCo₂O₄ nanoflowers has been confirmed through X-ray photoelectron spectroscopy (XPS). The energy bands and density of states (DOS) of ZnCo₂O₄ are examined using density functional theory, revealing that treatment with NaBH₄ reduces the band gap of ZnCo₂O₄ while increasing the DOS near the Fermi level compared to pristine ZnCo₂O₄. Furthermore, the specific capacitance of reduced ZnCo₂O₄ is nearly double that of its unmodified counterpart. This straightforward and practical approach significantly enhances both conductivity and specific capacitance in metal oxides, making it applicable to other similar materials.