Cobalt oxide-based nanoparticles were prepared by solvothermal method (140°C and 8 h) by using Cobalt II acetylacetonate and cobalt III acetylacetonate in a polar protic solvent, where H2O2 acted as reducing agent facilitating the oxidation. XRD analysis confirmed the formation of pure cubic structure, with crystallite size 40 nm. Spectroscopic analysis using FTIR and Raman indicated the presence of several functional groups and vibrational modes, thereby confirming once again the purity of the spinel cubic structure. Nanosheet like morphology was observed by HRSEM and polycrystalline nature was confirmed by SAED pattern. UV-VIS-DRS analysis indicated the presence of two energy band gap values, and decreased with increasing reaction temperature. Surprisingly, a weak ferromagnetic order has been detected and was attributed to finite size, shape and uncompensated surface spin effects. The prepared Co3O4 nanoparticles exhibited high electrochemical performance brought out the pseudocapacitive behavior with high specific capacitance.