Construction of ZnSe/ZnO Nanosheet Architecture to Boost Electrochemical Performance in Supercapacitors

Developing high-performance electrode materials with superior electrochemical activity and long-term stability remains crucial for the advancement of next-generation supercapacitors. In this study, a ZnSe/ZnO nanosheet heterostructure was fabricated via facile solvothermal synthesis, followed by controlled thermal oxidation. Structural and morphological analyses confirmed the successful formation of a ZnSe/ZnO composite with a highly porous nanosheet architecture and abundant interfacial defects, which serve as active sites for redox reactions. The optimized Z400 sample exhibited a synergistic combination of the excellent electrical conductivity of ZnSe and the chemical stability of ZnO, leading to enhanced charge transfer and ion diffusion kinetics. Electrochemical investigations revealed a high specific capacitance of 402.5 F g–1 at 2 mV s–1, remarkable rate capability, and outstanding cyclic durability with 95% capacitance retention after 3000 cycles. When assembled into an asymmetric supercapacitor device using activated carbon as the negative electrode, the ZnSe/ZnO composite achieved an extended operating voltage window of 1.5 V, delivering an energy density of 5.55 Wh kg–1 and a power density of 83.25 W kg–1. Density functional theory calculations further corroborated the enhanced electronic density of states near the Fermi level, validating the experimentally observed superior capacitive behavior. These results demonstrate that the ZnSe/ZnO nanosheet heterostructure represents a promising and scalable electrode material for high-performance energy storage applications.