Heterostructure of metal–organic framework-derived straw-bundle-like CeO2 decorated with (Ni, Co)3S4 nanosheets for high-performance supercapacitor

Abstract

Rational design of complex nanostructure with controllable composition and morphology is highly desired for electrode materials of supercapacitors (SCs). Herein, (Ni, Co)3S4 nanosheets have been decorated on metal–organic framework (MOF)-derived straw-bundle-like CeO2 assembled by one-dimensional (1D) nanorods to form a CeO2@(Ni, Co)3S4 heterostructure. Such a heterostructure shows a high specific capacitance of 1319F/g at a current density of 1 A/g and an outstanding rate performance (85.2%) when the current density is increased to 10 A/g. In addition, the CeO2@(Ni, Co)3S4 is assembled into an asymmetric cell, which displays a maximum energy density of 34.2 Wh/kg at a power density of 849.2 W/kg along with excellent cycling stability (84.8% of initial capacitance is retained after 10,000 cycles). The outstanding electrochemical performance of the electrode material is ascribed to the merits of CeO2@(Ni, Co)3S4 heterostructure. The MOF-derived porous 1D CeO2 nanorods can afford large accessible electroactive surface area and rapid electron transfer pathways. The strong electronic interaction between CeO2 and (Ni, Co)3S4 promotes surface reaction kinetics, and the abundant oxygen vacancies increase electronic conductivity of electrode and OH−capture. The rich valence states boost the specific capacitance by complex redox reactions. Besides, the core-shelled structure ensures robust mechanic stability. The present synthesis strategy can be used to prepare various heterostructures as electrode materials for SCs and electrolysis.