Direct solid–vapor approach to 2D FeCoNiP@N-graphene-CNTs as robust electrode material for high-performance supercapacitors

Abstract

Carbon supported bi(tri)-metallic phosphides are well known high-active electrode nanomaterials as it poses multiple redox sites, excellent electrochemical reversibility, and stability. In spite of that the synthesis of metal phosphides are limited as it involves multiple steps, harsh preparation conditions and often pose poor metal-support interactions. Herein, a simple and direct one-step solvent-free solid–vapor method was developed for the fabrication of bi(tri)-metallic phosphides supported N-graphene/N-CNTs 2D-nanosandwidch, first report to the best of our knowledge. Unique surface morphology, high surface area, good thermal stability and strong metal-support interaction, were confirmed for the as prepared electrocatalysts (FeNiP/NCNTs, FeCoP/NCNTs and FeNiCoP/NCNTs). In three electrode system, the FeNiCoP/NCNTs showed highest specific capacitance of 1479F/g at 1 A/g in 3 M KOH and excellent cycling stability, with capacitance retention of 90.8 % over 5000 cycles. Interestingly in the two-electrode system, the FeNiCoP/NCNTs demonstrated impressive capacitance of 245F/g at 1 A/g, power density of 10567 W/kg and energy density of 66.7 Wh/kg, with excellent retention of 91.5 % over 5000 cycles. The direct one-step preparation and high electrochemical performance inclusively promote the present FeNiCoP/NCNTs (with low metal loading of less than 10 wt%) as a promising supercapacitor electrode nanomaterial for energy storage applications.