Room temperature boronized and phosphated cobalt-nickel metal-organic framework as the electrode material for supercapacitors

Phosphating is a common method for improving the carrier concentration and electrochemical activity of metallic compounds for energy storage applications. However, the traditional phosphating approach often requires high-temperature thermal treatments that accompany complex recrystallization processes, which are not suitable for supercapacitors. Herein, we conducted the boronation of a cobalt‑nickel metal-organic framework (MOF) at room temperature (25 °C) followed by phosphating to fully activate the metallic species of the MOF through crystal structure regulation. The resultant sample (Co-Ni-B-P) achieved excellent electrochemical properties. And the prepared Co-Ni-B-P exhibited a high specific capacitance of 1578 Fg−1 at 1 Ag−1. Meanwhile, an asymmetric supercapacitor (ACS) with activated carbon and the Co-Ni-B-P composite acting as cathode and anode, respectively, delivered a specific energy of 76.5 Wh kg−1 at a specific power of 849 W kg−1. In addition, it exhibited an outstanding cycling stability characteristic of 87% after 5000 charge/discharge cycles. This study provides an ingenious phosphating route for boronation samples to enhance performance of the electrode materials of supercapacitors. This two-step activation approach elucidates the modulation of the electronic structure while maintaining the stacked structure of clearly defined nanosheets, which is promising for the design of MOFs derivatives for capacitive energy storage devices.