MXene Integrated Metal-Organic Framework Derived Cobalt Phosphide for Supercapacitor Applications

Abstract

The development of high energy density electrode materials for supercapacitors is essential to address the growing energy demands and environmental concerns. Transition metal phosphides, particularly cobalt phosphide (CoP) have attracted significant interest due to their high theoretical capacity and excellent redox activity. However, their practical application is limited by poor cycling stability and lower electrical conductivity. To address these challenges, this study employs a metal-organic framework (ZIF-67) as a precursor to synthesize CoP, followed by the in- situ heterojunction formation (CoP/50-Ti₃C₂T_x, CoP/100-Ti₃C₂T_x, and CoP/150-Ti₃C₂T_x) with different mass loading (50, 100, and 150 mg) of MXene (Ti₃C₂T_x). The optimized electrode material CoP/100-Ti₃C₂T_x achieve the highest specific capacitance of 625.9 F/g at 0.25 A/g with a high rate performance of 260.2 F/g at 25 A/g. This performance significantly surpasses bare CoP (397.3 F/g at 0.25 A/g), Ti₃C₂T_x (106.3 F/g at 0.25 A/g), and other CoP/Ti₃C₂T_x composite. Additionally, it demonstrates a cycling stability of 78.13% for 10,000 cycles at 20 A/g. Furthermore, an asymmetric supercapacitor device was fabricated using CoP/100-Ti₃C₂T_x as positive electrode materials and activated carbon as the negative electrode. The as-fabricated device delivered an energy density of 22.59 Wh/kg at a power density of 399.99 W/kg with capacitance retention of 73.25% after 2000 cycles at 10 A/g and Coulombic efficiency close to 100%. The insight charge-discharge mechanism is explained in detail.