Facile hydrothermally grown cobalt oxide (Co3O4) nanostructures and their electrochemical performances

In this study, pure cobalt oxide (Co3O4) nanoparticles were synthesized using a simple hydrothermal approach. The effect of the reducing agent and reaction temperatures of the prepared products were examined. Co3O4 is formed in the as-synthesized sample, at reaction temperature 190 °C was observed in the XRD pattern. The XPS survey scan spectrum showed the distinctive peaks of the Co and O elements and their valence states. FESEM and HRTEM revealed the particles as cubical in nature. Peak associated with the elements Co and O on the EDAX spectrum demonstrated the purity of the nanoparticles. Three electrode setups were used to measure the electrochemical properties of the synthesized nanoparticles. DTA curve corresponding exothermic peak at 225 °C and the crystallization of the final product was attributed for the third weight loss of 1.5 % in the temperature range of 280 °C to 450 °C. Formation of Co3O4 was confirmed by the observed XRD diffraction peaks at 2θ = 36.83°, 59.82°, and 65.30°, which correspond to h k l planes (311), (511) and (440), respectively. The high-resolution Co2p spectra showed two prominent spin-orbital peaks, 2p1/2 and 2p3/2, at 796.37 eV and 781.81 eV, respectively. The increase in temperature causes the particle size to grow ranges between 20 and 70 nm and the average particle size distribution in the TEM image is 42 nm. The integral area of the CV curve was measured during the CV measurement and as the as-prepared Co3O4 electrode displays specific capacitance values of 154, 126, 81, 65, and 49 Fg−1 at various scan rates of 10, 20, 50, 70, and 100 mVs−1, respectively.