Heterogeneous Ni-MOF/V2CTx–MXene hierarchically-porous nanorods for robust and high energy density hybrid supercapacitors

Abstract

Interfacial engineering is an appealing strategy to construct heterogeneous nanostructures and tunes the morphology of metal–organic frameworks (MOFs) and MXenes for hybrid supercapacitors. Herein, a temperature-controlled annealing process is introduced to fabricate Ni-MOFs/V₂CT_x–MXene (T_x denotes the surface groups, –O, –OH, and –F) composites on Ni foam (NF) (namely MOF/MXene/NF) and subsequently build the heterogeneous structure of a hierarchically-porous nanorod composite without a change in the crystalline structure. Experimental characterizations and theoretical calculations reveal that Ni–O–V bridging bonds are constructed at the Ni-MOF and V₂CT_x interfaces, which could be used to establish a favorable electronic structure in promoting conductivity and reactivity. The optimized MOF/MXene/NF electrode obtained at 300 °C (i.e., MOF/MXene/NF-300) delivers an ultrahigh specific capacity of 1103.9 C g⁻¹ at 1 A g⁻¹. The as-assembled hybrid supercapacitor, composed of MOF/MXene/NF-300 as the cathode and activated carbon/NF as the anode, delivers a high energy density of 46.3 W h kg⁻¹ at a power density of 746.8 W kg⁻¹ and an outstanding cycling stability of ca. 118.1% capacity retention after 15 000 cycles. Such an achievement stems from the strong chemical bonds at the interface and unique porous morphology. This work suggests a new avenue for designing and preparing robust and high-performance electrode materials for hybrid supercapacitors.