Novel Au nanorod/Cu₂O composite nanoparticles for a high-performance supercapacitor

Metal-oxide nanomaterials have attracted great interest in recent years due to their novel characteristics such as surface effect and quantum confinement. A fascinating Au nanorod (NR)/cuprous oxide core-shell composite (AuNR/Cu₂O) was directly synthesized using a moderate one-pot facile green redox method and further utilized for energy storage applications in a supercapacitor. The synthesis mechanism is based on the use of reducing agents to form the core shell. The resultant composite was deposited on the surface of nickel foam as a result of redox reactions between Au and Cu via a hydrothermal method. AuNR/Cu₂O composite nanoparticles (NPs) were characterized using various spectroscopic and microscopic techniques, including UV-vis and X-ray photoelectron spectroscopies, Brunauer-Emmett-Teller surface area analysis, X-ray diffractometry, and transmission electron microscopy. The AuNR/Cu₂O composite NPs grow via the depositing of a 20-50 nm Cu₂O shell on an AuNR core with dimensions of 5-20 nm in width and 40-70 nm in length. The as-synthesized AuNR/Cu₂O composite NPs were effectively used as electrode materials in a supercapacitor, and their electrochemical performance was determined by cyclic voltammetry, galvanostatic charge-discharge measurements, and electrochemical impedance spectroscopy in 2 M KOH aqueous solution as an electrolyte. The composite NPs showed excellent average specific capacitance of 235 F g⁻¹ at a current density of 2 A g⁻¹ and durable cycling stability (96% even after 10 000 cycles). The higher efficiency of the AuNR/Cu₂O composite NPs can be attributed to the presence of AuNR in the core. The AuNR/Cu₂O composite NPs exhibit a high surface area and high electrical conductivity, which consequently result in their excellent specific capacitance and outstanding rate as an all-solid-state supercapacitor electrode.