Ag doped Co₃O₄ nanoparticles for high-performance supercapacitor application

Ag doped Co₃O₄ nanoparticles (NPs) were synthesized via a co-precipitation method changing the concentration of Ag. The crystal structure, morphology, surface area, functional group, optical band gap, and thermal property were investigated by XRD, SEM, BET, FTIR, UV-Vis, and TGA/DTA techniques. The XRD results showed the formation of single-cubic Co₃O₄ nanostructured materials with an average crystal size of 19.37 nm and 12.98 nm for pristine Co₃O₄ and 0.25 M Ag-doped Co₃O₄ NPs. Morphological studies showed that pristine Co₃O₄ and 0.25 M Ag-doped Co₃O₄ NPs having a porous structure with small spherical grains, porous structures with sponge-like structures, and loosely packed porous structures, respectively. The pristine and 0.25 M Ag-doped Co₃O₄ NPs showed BET surface areas of 53.06 m²/g, and 407.33 m²/g, respectively. The band gap energy of Co₃O₄ NPs were 2.96 eV, with additional sub-bandgap energy of 1.95 eV. Additionally, it was discovered that the band gap energies of 0.25 M Ag-doped Co₃O₄ NPs ranged from 2.2 to 2.75 eV, with an extra sub-band with energies ranging from 1.43 to 1.94 eV for all as-prepared samples. The Ag-doped Co₃O₄ as prepared samples show improved thermal properties due to the doping effect of silver. The CV test confirmed that the 0.25 M Ag-doped Co₃O₄ NPs exhibited the highest specific capacitance value of 992.7 F/g at 5 mV/s in a 0.1 M KOH electrolyte solution. The energy density and power density of 0.25 M Ag-doped Co₃O₄ NPs were 27.9 W h/kg and 3816.1 W/kg, respectively.