Effect of Annealing Temperature on the Structural and Electrochemical Properties of Hydrothermally Synthesized NiCoO Electrodes.

In this study, a porous Ni-foam support was employed to enhance the capacitance of nickel cobaltite (NiCoO) electrodes designed for supercapacitors. The hydrothermal synthesis method was employed to grow NiCoO as an active material on Ni-foam. The NiCoO sample derived from hydrothermal synthesis underwent subsequent post-heat treatment at temperatures of 250 °C, 300 °C, and 350 °C. Thermogravimetric analysis of the NiCoO showed that weight loss due to water evaporation occurs after 100 °C and enters the stabilization phase at temperatures above 400 °C. The XRD pattern indicated that NiCoO grew into a spinel structure, and the TEM results demonstrated that the diffraction spots (DSs) on the (111) plane of the sample annealed at 350 °C were more pronounced than those of other samples. The specific capacitance of the NiCoO electrodes exhibited a decrease with increasing current density across all samples, irrespective of the annealing temperature. The electrode annealed at 350 °C recorded the highest specific capacitance value. However, the capacity retention rate of the NiCoO electrode revealed a deteriorating trend, declining to 88% at 250 °C, 75% at 300 °C, and 63% at 350 °C, as the annealing temperature increased.