Ni/Co-MOF@aminated MXene hierarchical electrodes for high-stability supercapacitors

Owing to the instability and poor electronic conductivity of redox-active metal-organic frameworks (MOFs), the redox-active MOFs as a direct electrode for achieving fast and high-stability supercapacitors is a significant challenge. Herein, highly redox-active bimetallic Ni/Co metal-organic frameworks (Ni/Co-MOF) is in-situ stabilizied by 2D thin-layer aminated Ti3C2Tx to construct promising hierarchical heterostructural electrodes with superior wettability for high-performance supercapacitors. Benefitting from high conductivity and the good wettability with electrolyte of aminated MXene, the bimetallic Ni/Co-MOF can be uniformly in-situ stabilizied on the aminated MXene surface, thus guaranteeing the superior electronic and ionic transmission from the redox active center of Ni/Co-MOF, and good interfacial compatibility and large contact area. The modified MXene is beneficial to slow down the van der Waals interactions between functional groups to exfoliate the sheet-like structures. For the rapid redox reactions whereas the synergy of highly redox-active Ni/Co in bimetallic Ni/Co-MOF provides a fast redox reaction for Faradaic capacitance. Therefore, as-obtained Ni/Co-MOF@TCT-NH2 presents an ultra-high specific capacitance of 1924 F.g(-1) at 0.5 A.g(-1) and an ultra-long cycling stability with 10,000 cycles at 10 A.g(-1) in a three-electrode system. Besides, the assembled Ni/Co-MOF@TCT-NH2//AC asymmetrical devices exhibit a maximum specific energy density of 98.1 Wh.kg(-1) at 600 W.kg(-1) and superior rate stability with 15,600 cycles. Such superior electrochemical performance demonstrates that the heterojunction construction of thin-layer aminated MXene to stabilize highly redox-active bimetallic MOFs is an effective strategy for MOFs as a direct electrode to enhance the energy storage.

Automated summary

This study presents a strategy to enhance the energy storage of metal-organic frameworks (MOFs) by constructing promising hierarchical heterostructural electrodes using a thin-layer aminated MXene. By stabilizing highly redox-active bimetallic Ni/Co MOFs on the surface of aminated MXene, the electrodes exhibit superior wettability and conductivity, allowing for superior electron and ion transmission. The modified MXene also helps to exfoliate the sheet-like structures of MOFs, resulting in rapid redox reactions and high capacitance. The obtained electrode shows ultra-high specific capacitance and long cycling stability in a three-electrode system, demonstrating the effectiveness of this strategy for enhancing energy storage.