Enhancing the supercapacitive performance of Nickel based metal organic framework-carbon nanofibers composite by changing the ligands

Abstract

The present work offers a facile, cost-effective and green strategy to efficiently regulate the pore dimensions and surface morphology of Nickel based Metal organic frameworks (MOFs) using three carboxylic acids of different molecular lengths. The material characterization studies revealed that Ni MOF with longer organic linker i.e., 4, 4‘-Biphenyl dicarboxylic acid (Ni-BPDC) exhibits large surface area and large pore dimensions which enables swift movement of electrolyte ions through the framework. Also, the interconnected network of Ni-BPDC nanoplates results into continuous charge distribution, thus delivering better electrochemical performance amongst three Ni MOFs. Furthermore, to enhance the electrochemical performance of Ni-BPDC, it was combined with carbon nanofibers (CNF) and the electrochemical characterization studies of Ni-BPDC/CNF as a single electrode material shows its high specific capacity of 250.6 mA h g−1 at current density of 1 A g−1. To further explore real time application of Ni-BPDC/CNF composite, a symmetric supercapacitor device was fabricated in a Swagelok cell and it is found to deliver excellent energy density of 48.1 Wh kg−1 and power density of 1064.7 W kg−1 at an operating voltage of 1.2 V. Besides, it manifests a long cycle life with only 8% deterioration of initial specific capacity after 5000 cycles. We believe that these encouraging results not only suggests the possibility for tuning properties of existing MOFs using different organic linkers but also provides an efficient way to develop hybrid MOF composites for future energy storage applications.