Facile room-temperature solution-phase synthesis of a ZIF-67 : Ni hybrid-MOF battery type material for supercapacitor applications

Metal-organic frameworks (MOFs) have gained significant attention as potential supercapacitor electrodes due to their high surface area, tunability, and well-defined porosity. However, their application is often limited by low capacity, poor electrical conductivity, and weak substrate adhesion, as observed in zeolitic imidazolate framework-67 (ZIF-67). To address these limitations, this study investigates the effect of nickel incorporation into ZIF-67, aiming to enhance its electrochemical performance. A series of hybrid-MOFs, denoted as ZIF-67 : Ni (1 : <i>X</i>), were synthesized <i>via</i> a simple solution-phase method at room temperature by varying the nickel content. Nickel was introduced to facilitate faster redox reactions and improve ion transport, thereby enhancing charge storage capability. The optimized ZIF-67 : Ni (1 : 2) electrode exhibited a high specific capacity of 161.2 mA h g^-1 at 1 A g^-1, with a capacity retention of 74.6% after 5000 charge-discharge cycles, outperforming pristine ZIF-67 and other nickel-mixture variants. The improved electrochemical performance is attributed to the enhanced porous structure, which increased active site accessibility and reduced charge transfer resistance. Furthermore, an asymmetric supercapacitor device assembled using ZIF-67 : Ni (1 : 2) as the positive electrode and activated carbon (AC) as the negative electrode (ZIF-67 : Ni (1 : 2)//AC) demonstrated a cell capacity of 44.6 mA h g^-1, a specific energy of 36.97 W h kg^-1, and a specific power of 416.3 W kg^-1 at 0.5 A g^-1. Notably, the device exhibited excellent cycling stability, retaining 99.8% of its capacity after 10 000 cycles at 10 A g^-1. These findings highlight the potential of multi-metallic interactions in enhancing the electrochemical performance of ZIF-67-based MOFs, offering valuable insights for the development of high-performance supercapacitor electrodes.