Oxygen vacancy-enriched NiFe-MOF/Ti3C2Tx MXene composite as a binder-free cathode for high-performance hybrid supercapacitors

Abstract

With growing global energy demands, developing electrode materials with high capacitance and rate capability is increasingly critical for supercapacitors. Herein, a free-standing composite cathode was fabricated via a one-step solvothermal method, achieving in situ growth of 2D nickel-iron metal-organic framework (MOF) nanosheets on Ti3C2Tx MXene-decorated nickel foam (denoted as NiFe-MOF/MX/NF). The architectural design leverages synergistic effects of bimetallic coupling and the strong MOF-MXene interfacial interactions to enhance redox kinetics and structural durability. Notably, Fe incorporation induces abundant oxygen vacancies within the MOF lattice, facilitating improved charge transfer and increasing electroactive sites. Consequently, the NiFe-MOF/MX/NF electrode exhibits a high specific capacity of 197.0 mAh g-1 at 1 A g-1, along with outstanding rate performance, retaining 68.03% of its capacitance at 10 A g-1. Moreover, a hybrid supercapacitor assembled with the NiFe-MOF/MX/NF composite cathode and an activated carbon anode achieves a maximum energy density of 40.3 Wh kg-1 and a peak power density of 7500 W kg-1, along with exceptional capacitance retention of 93.26% after 20,000 cycles. This work paves the way for the development of binder-free, bimetallic MOF-based electrode materials with defect engineering for high-performance supercapacitors.