Facile hydrothermal synthesis of rGO/CoSO4 composite as high-performance supercapacitor electrode: Effect of autoclave and non-autoclave

Hybrid materials for electrode exhibit promising electrochemical performance in energy storage systems due to their excellent ion accessibility and high electrical conductivity. In this work, a novel rGO/CoSO₄-H₂O nanocomposite powder was synthesized via a simple one-pot hydrothermal process with and without autoclave at 90 °C for 24 h to investigate the influence of these synthesis conditions on their structural, morphological, and electrochemical properties. The X-ray diffraction (XRD) and Scanning electron microscope (SEM) studies revealed the presence of a hybrid structure that consists of polycrystalline CoSO₄-H₂O embedded on the rGO surface. The autoclaved sample exhibited a higher specific capacitance of 992.69 F/g at a current density of 2 A/g compared to the non-autoclaved one (654.92 F/g less at 2 A/g). However, both samples showed excellent stability (>93 %) over 7500 charge-discharge cycles. The material synthesis strategy presented in this study is facile, rapid, and simple. The results show that the autoclaving enhances the capacitive performance of rGO/CoSO₄-H₂O composites by improving graphene oxide reduction and nanoparticle contact. It should be noted that the rGO/CoSO₄-H₂O composite prepared without autoclaving still shows excellent performance, outperforming those synthesized by other methods. Additionally, graphene can be reduced efficiently in a single hydrothermal step at low temperature without additives. The above results indicate that the hybrid rGO/CoSO₄-H₂O electrodes synthesized by this approach would be a promising candidate for practical application of high-performance SCs.