Designing a Copper- and Silver-Sulfide Composite with Co₃O₄ for High-Performance Electrochemical Supercapacitors

Electronic devices have driven modern lifestyle demands for efficient and environmentally friendly energy storage appliances. This paper reports the simple design of an efficient, cost-effective pseudocapacitor electrode based on copper sulfide (Cu₂S) and silver sulfide (Ag₂S) composites with cobalt oxide (Co₃O₄) for high-performance energy storage devices. A simple one-pot approach was used to synthesize hexagonal sheets of Co₃O₄ and a successive ionic layer adsorption and reaction method was exploited to coat these sheets with nanostructures of Cu₂S and Ag₂S. The resulting three-dimensional (3D) Co₃O₄/Cu₂S and Co₃O₄/Ag₂S composite electrode contained a high loading of Cu₂S and Ag₂S nanoparticles (metal sulfides) on the hexagonal sheets of Co₃O₄ (metal oxide), which offers a highly conductive network assisting in rapid charge-transfer reactions and reduces the internal resistance of the electrode. A symmetrical supercapacitor based on Co₃O₄/Cu₂S//Co₃O₄/Cu₂S showed a high areal capacitance of 1080 mF cm⁻², which was significantly higher than that of the Co₃O₄/Ag₂S//Co₃O₄/Ag₂S symmetric supercapacitor (645 mF cm⁻²). These results show that the Co₃O₄/Cu₂S composite heterostructure is a promising electrode architecture for high performance pseudocapacitors.