Lanthanum-Doped Co3O4 Nanocubes Synthesized via Hydrothermal Method for High-Performance Supercapacitors.

The development of high-performance supercapacitor electrodes is crucial to meet the increasing demand for efficient and sustainable energy storage systems. Cobalt oxide (Co3O4), with its high theoretical capacitance, is a promising electrode material, but its practical application is hindered by poor conductivity limitations and structural instability during cycling. In this work, lanthanum La3+-doped Co3O4 nanocubes were synthesized via a hydrothermal approach to tailor their structural and electrochemical properties. Different doping concentrations (1, 3, and 5%) were introduced to investigate their influence systematically. X-ray diffraction confirmed the retention of the spinel phase with clear evidence of La3+ incorporation into the Co3O4 lattice. Also, Raman spectroscopy validated the structural integrity through characteristic Co-O vibrational modes. Scanning electron microscopy analysis revealed uniform cubic morphologies across all samples. The formation of the cubic spinel structure of 1% La3+-doped Co3O4 are confirmed from XPS and TEM studies. Electrochemical evaluation in a 3 M KOH electrolyte demonstrated that 1% La3+-doped Co3O4 nanocubes delivered the highest performance, achieving a specific capacitance of 1312 F g-1 at 1 A g-1 and maintaining a 79.8% capacitance retention and a 97.12% Coulombic efficiency over 10,000 cycles at 5 Ag-1. It can be demonstrated that La3+ doping is an effective strategy to enhance the charge storage capability and cycling stability of Co3O4, offering valuable insights for the rational design of next-generation supercapacitor electrodes.