Redox-active nanostructure electrode of Mn/Ni bimetal organic frameworks anchoring on multi-walled carbon nanotubes for advanced supercapacitor

Abstract

The metal-organic frameworks (MOF) is a promising electrode material for supercapacitor, but the traditional monometallic metal-organic frameworks are limited by poor conductivity and structural stability. In this work, a novel manganese (Mn) and nickel (Ni) bimetallic metal-organic frameworks anchored on multi-walled carbon nanotubes (Mn/Ni-MOF@MWCNTs) were fabricated via a one-step solvothermal method. The morphologies, micro-structures and electrochemical properties of Mn/Ni-MOF@MWCNTs with different mass ratios of Mn and Ni were compared. The results indicated that multi-walled carbon nanotubes (MWCNTs) provides numerous active anchoring sites which is introduced into the architecture of the optimal Mn/Ni-MOF; these sites are responsible for enhancing the electrons transfer and structural integrity, with the small contact resistance and charge transfer resistance. As a result, a specific capacitance of 793.6 F g −1 at 1 A g −1 in 1 M LiOH aqueous solution was achieved, and the capacitance retention was retained at 74.92% after 1000 cycles at 1 A g −1 . The crystal structures and valence band information of the anchored Mn/Ni-MOF were obtained by DFT calculation. Besides, Mn/Ni-MOF@MWCNTs//Mn/Ni-MOF@MWCNTs symmetry supercapacitor showed an excellent energy density of 33.2 Wh kg −1 at a power density of 1198 W kg −1 and stabilizing capacity retention of 78.3% over 2000 cycles. These results provide a promising strategy for high-performance electrochemical energy storage. • Mn/Ni-MOF@MWCNTs is an effective electrode material for supercapacitors. • The structure is well tailored at the optimal mass ratio of Mn to Ni of 1: 3. • Mn/Ni-MOF@MWCNTs shows excellent specific capacitance of 793.6 F g −1 at 1 A g −1 . • Mn/Ni-MOF@MWCNTs//Mn/Ni-MOF@MWCNTs SSC device shows an excellent energy density of 33.2 Wh kg −1 at a power density of 1198 W kg −1 . • Excellent cycling durability with 78.3% retention after 2000 cycles was observed.