In-situ conversion of Ni2P/rGO from heterogeneous self-assembled NiO/rGO precursor with boosted pseudocapacitive performance

Abstract Two-dimensional (2D) heterostructural Ni2P/rGO is successfully fabricated by in-situ phosphating self-assembled NiO/rGO composites and shows the enhanced electrochemical performances. In this design, the rGO sheets effectively reduce the lattice strain created during the phase transformation from NiO to Ni2P, thereby maintaining ultrathin nanostructures of Ni2P. The resulting Ni2P/rGO layered heterostructure gives the composite plenty of pores or channels, good electrical conductivity and well-exposed active sites. Density functional theory (DFT) calculation further demonstrates that the Fermi energy level and electron localize of near Ni atoms in Ni2P is higher than that of NiO, which endow Ni2P with faster and more reversible redox reactivity in dynamic. Benefiting from their structural and compositional merits, the as-synthesized Ni2P/rGO exhibits high specific discharge capacity and excellent rate performance. Furthermore, a hybrid supercapacitor built with Ni2P/rGO and activated carbon shows a high specific energy of 38.6 Wh/kg at specific power of 375 W/kg.