Polyvinylpyrrolidone (PVP) assisted synthesis of Ni MOF: Enhanced supercapacitive performance through morphology control

Abstract

Metal-organic frameworks (MOFs) are highly coveted for supercapacitors owing to their extensive surface area and customizable pore structures. Nickel MOF (Ni MOF) has shown superior capacitance among MOFs but faces limitations such as poor conductivity and cyclic stability. This study presents a nitrogen-enriched Nickel MOF (N-Ni MOF) synthesized via a simple solvothermal method, with polyvinylpyrrolidone (PVP) acting as a nitrogen source and structure-directing agent. For the first time, the influence of PVP on the structure and supercapacitive performance of Ni MOF electrodes was systematically evaluated. Comprehensive characterization was performed using X-ray diffraction, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy, Brunauer-Emmett-Teller analysis and X-ray photoelectron spectroscopy. Cyclic voltammetry and galvanostatic charge-discharge tests were employed to evaluate the supercapacitive characteristics. The introduction of PVP altered the flower-like structure of Ni MOF into hierarchical microspheres, resulting in an expanded surface area. The N-Ni MOF reached a notable specific capacitance of 1519 Fg⁻¹ at 1 Ag⁻¹. A symmetric supercapacitor utilizing N-Ni MOF electrodes demonstrated a specific capacitance of 529 Fg⁻¹, an energy density of 66.12 Whkg⁻¹, and a power density of 900.3 Wkg⁻¹, maintaining 89 % stability after 2000 cycles at 1Ag⁻¹.