Template-driven synthesis of tin selenide nanosheets and their composites for supercapacitor applications

Bulk SnSe and SnSe₂, with direct-band gaps of 1.3 eV and 1.84 eV, are promising materials for optoelectronics, lithium-ion batteries, thermoelectrics, and supercapacitors, due to their excellent electrochemical performance for energy storage. In this context, a new molecular precursor, [Me₂Sn(SeC₄H₃N₂)₂], has been derived from bis(2-pyrazinyl)diselenide {(2-pyzSe)₂} and structurally characterised by single crystal X-ray diffraction (sc-XRD) that serves as a building block for the fabrication of tin selenide (SnSe) nanosheets and tin selenide/g-C₃N₄ composites. The electrochemical performance of the synthesised nanosheets and composites was evaluated for their potential use in supercapacitor applications. The band gaps of rectangular SnSe (1.85 eV) and hexagonal SnSe₂ (2.21 eV) nanosheets, and tin selenide/g-C₃N₄ composites (1.89 and 1.91 eV) exhibited a blue shift compared to those of bulk SnSe (E_g = 1.3 eV) and SnSe₂ (E_g = 1.84 eV). The tin selenide/g-C₃N₄ composite utilised in supercapacitor applications exhibited a specific capacitance of 140 F g^-1 at a current density of 1 A g^-1. Remarkably, it retained 85% of this specific capacitance after 5000 cycles, demonstrating outstanding cycling durability.