Mass-loading effect of graphene foam (GF) on the electrochemical performance of nickel phosphate as an electrode for supercapacitor application

A.A. Mirghni, M.J. Madito, K.O. Oyedotun, T.M. Masikhwa, N.M. Ndiaye, N. Manyala
University of Pretoria,
South Africa

Keywords: nickel phosphate, hydrothermal method, energy storage, supercapacitor

Summary:

Increasing demands for portable and flexible electronics along with highly efficient electrical vehicles has promoted the rapid development of lightweight, highly efficient energy storage devices. Electrochemical capacitors also commonly referred to as supercapacitors (SCs), due to their fast charge-discharge dynamics and good long life cycle stability, have equally attracted considerable attention. This work presents the effect of different contents of graphene foam (GF) on the electrochemical capacity of nickel phosphate Ni3(PO4)2 nanorods as an electrode material for supercapacitor applications. Ni3(PO4)2 nanorods were synthesized via a hydrothermal method followed by different mass loading of graphene (30, 60, 90 and 120 mg, denoted as Ni3(PO4)2/30 mg GF, Ni3(PO4)2/60 mg GF, Ni3(PO4)2 /90 mg GF and Ni3(PO4)2/120 mg GF, respectively. The electrochemical behavior of Ni3(PO4)2 and Ni3(PO4)2/GF nanorods composites were analysed in a three-electrode cell using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) in a 6 M KOH electrolyte. The electrochemical tests showed that the specific capacity increased with increasing the GF content up to 90 mg then decreased. The Ni3(PO4)2/90 mg GF exhibited the highest specific capacity of 49.6 mAh g-1 at 0.5 Ag-1 current density. The high specific capacity is attributed to good crystallinity and synergetic interaction of the GF and Ni3(PO4)2 nanorods.