Cobalt-molybdenum selenide double-shelled hollow nanocages derived from metal-organic frameworks as high performance electrodes for hybrid supercapacitor

Abstract

In this paper, we developed a sequential chemical etching and selenization processes to synthesize Co-MoSex double-shelled hollow nanocages (CMS-DSHNCs) as high performance electrode materials for supercapacitor applications. Co-MoO_x yolk-shelled hollow nanocages were firstly synthesized using a solvothermal process through facile ion-exchange reactions between zeolitic imidazolate framework-67 (ZIF-67) and MoO₄^2- ions. By applying a solvothermal temperature of 160 °C in the presence of SeO₃^2- and subsequently annealing strategy, CMS-DSHNCs were successfully synthesized with a yolk-shell hierarchically hollow and porous morphology of mixed metal selenides. The CMS-DSHNCs exhibit superior electrochemical properties as electrode materials for supercapacitor: e.g., a specific capacity of 1029.8C g^-1 at 2 A g^-1 (3.089C cm^-2 at 6 mA cm^-2), a rate capability of ∼ 76.14%, a capacity retention at 50 A g^-1, and a good cycle stability (95.2% capacity retention over 8000 cycles). A hybrid supercapacitor was constructed using the CMS-DSHNCs as the cathode and activated carbon (AC) as the anode in a solution of 3 M KOH, and achieved a high specific energy of 45 Wh kg^-1, and a specific power up to 2222 W kg^-1 with a good cycling stability of 94% after 8000 cycles.

Keywords: Asymmetric supercapacitor; Capacitive-type electrode; Co-MoSe(x); Double-shelled and hollow nanocages.