Tetra germanium nonaselenide enwrapped with reduced graphene oxide and functionalized carbon nanotubes (Ge4Se9/RGO/FCNTs) hybrids for improved energy storage performances

Abstract

The development of multifunctional layered semiconductor materials and their carbonaceous hybrids as acceptable positive electrode materials for supercapacitor application is of key interest. Ternary germanium selenide (Ge₄Se₉) with reduced graphene oxide (RGO) and functionalized carbon nanotube (FCNT) hybrids were successfully synthesized by following a one-step hydrothermal approach, and their electrochemical energy storage performance toward supercapacitor (SC) applications was investigated. It was observed that the specific capacitance of Ge₄Se₉/RGO/FCNTs was 440 F g⁻¹ at 1 A g⁻¹ in an acidic (1 M H₂SO₄) medium. Further, the material showed 83% retention of its own initial value of capacitance with 98% coulombic efficiency after 5000 galvanostatic charge–discharge cycles. Considering the two-dimensional (2D) layered structures of MXenes with their greater stability, exceptional hydrophilicity, and pseudocapacitive behavior in aqueous electrolytes makes them an alternative for the fabrication of asymmetric SC devices. The above findings about MXenes suggest the design of an asymmetric device using MXene as the negative electrode material and as-prepared Ge₄Se₉/RGO/FCNTs as the positive electrode material in a similar electrolyte media. The fabricated Ge₄Se₉/RGO/FCNTs//MXenes displayed a higher specific capacitance of 102 F g⁻¹ at 1 A g⁻¹, with an acceptable energy density (E.D.) of 32 W h kg⁻¹ and a power density (P.D.) of 1071 W kg⁻¹. Furthermore, over long-term repeated 5000 GCD cycles the fabricated device retained 92% of its initial capacitance and good reversibility (96% coulombic efficiency), making the Ge₄Se₉/RGO/FCNT//MXenes assembly a preferable electrode material for enhancing asymmetric SC performance.